Particles are a fundamental component of the ocean, as they facilitate the transport of matter and provide surfaces for chemical reactions, while also acting as vehicles for the transport of nutrients, contaminants, and plastics from land to sea and impacting the distribution of sediments (Nowack and Bucheli, 2007; Wright et al., 2013; Corsi et al., 2014; Jeandel et al., 2015). They transfer metabolized energy from the upper productive layers to below the photic zone, act as a source of organic matter to the mesopelagic and benthic communities, and regulate turbidity and thus photosynthetically available water depths (Volkman and Tanoue, 2002; Turner, 2015).
Traditionally, particulate matter was defined as material unable to pass through a 0.45 µm filter to distinguish dissolved solutes from settling matter (Goldberg et al., 1952). Later a 0.2 µm filter was employed increasingly because such ‘sterile filtration’ better selected for all living particles (Verdugo, 2012; Jeandel et al., 2015). The particulate fraction may include mineral particles from rivers or resuspended sediment (e.g., sand, silt, clay, or metal oxides) and particles of organic origin such as viruses, bacteria, phytoplankton, fecal pellets, detritus and biopolymer aggregates (e.g., transparent exopolymeric particles (TEP), marine snow aggregates; Figure 1). However, it is now known that the fraction passing through a 0.45 µm filter also contains particulates in the form of colloids, macromolecules, biopolymers and nanoparticles (Filella, 2007). In addition, in the Anthropocene natural particles are being contested in abundance by synthetic nanoparticles (Corsi et al., 2014), contaminants and microplastics (Wright et al., 2013; Wagner et al., 2014). Thus, marine particles occur in many different shapes, sizes and compositions, and can be both living and dead organic as well as lithogenic pieces of matter (Newton and Liss, 1990) (Figure 1).
Particle transport occurs on a multitude of scales, from Brownian motion on the nanoscale and millisecond movements on a microscale to vertical settling in meters per day, and from horizontal current transport occurring dynamically in coastal seas to the slow movement in gyres within ocean basins at a scale of kilometers per hour (Nittrouer and Wright, 1994; Burd and Jackson, 2009). The coastal zone in particular is an extremely dynamic environment for particles and a zone where anthropogenic activities are concentrated (Halpern et al., 2008). Increased sediment input to the coastal seas has a range of sources from both the land and from offshore activities (Figure 2), which include dredging (Newell et al., 1998; Essink, 1999) and drilling operations (Breuer et al., 2004), as well as fishing activities such as bottom trawling (e.g., Ferré et al., 2008).
Greater particle abundance is also expected due to our changing climate: increased precipitation leads to rapidly increasing abundances of iron oxides and colloidal organic matter in rivers in the northern Hemisphere (e.g., Kritzberg and Ekström, 2012), precipitation and turbidity are correlated in catchments (Göransson et al., 2013), and stronger winds increase wave-driven turbidity in shallow coastal waters which can affect the submerged coastal vegetation such as seagrass (Harley et al., 2006; van der Heide et al., 2007). Climatically forced particle loads to the coast as well as anthropogenic activities lead to a multitude of impacts, such as decreased light availability to macro- and microalgae (Essink, 1999; De Boer, 2007), particle-bound contaminants, and local increased deposition and smothering of benthic organisms including shellfish, sponges, and corals (e.g., Essink, 1999; Gilmour, 1999; Kutti et al., 2015). Increased nutrient run-off frequently exacerbates these effects, leading to a range of problems such as intensification of (potentially harmful) algal blooms (Hallegraeff, 2010) and an expansion of coastal hypoxia (Zhang et al., 2010). Growing global aquaculture activities are also placing heavy demands on coastal ecosystems (Holmer et al., 2005), while coastal waters are also subjected to major inputs of waste material such as plastics, chemical compounds and other pollutants (Browne et al., 2011; Wright et al., 2013; Corsi et al., 2014) (Figure 2). A combination of both human impacts and hydrodynamic processes thus influence the distribution of particles, both on temporal as well as spatial scales in coastal zones.
Improved understanding of how particles are distributed in the coastal zone is prerequisite for successful coastal management. Thus we describe relevant natural particle transport mechanisms such as sinking and resuspension (Figure 2) before addressing how anthropogenic activities in the coastal zone are affecting the sourcing of particles but also interactions with their environment. We review these key particle sources, pathways and transport processes with a focus on stratified water columns occurring in estuaries with little tidal impact, including the Baltic Sea from its entrance from the North Sea in Skagerrak on the west coast of Sweden to the Bothnian Bay on the northeastern Swedish coast. The Baltic Sea is characterized by both vertical and lateral salinity gradients from Skagerrak to the Bothnian Bay. It is stratified by a shallow thermocline from spring to autumn, and permanently stratified by a halocline which occurs deeper through its basins. Examples of research focus and knowledge gaps are highlighted throughout emphasizing the need for more interdisciplinary approaches combining fields such as physical oceanography, marine chemistry, sedimentology, biology and marine technology.
Suspended and sinking particles represent a continuum, from nanoscale colloids with supramolecular properties, through micron-sized clays and bacteria, to mm-sized TEP and aggregates of particles (Figure 1). They transport carbon and energy in marine ecosystems but also scavenge and transport other abiotic particles, including microplastics, oil spill components, and other pollutants (Olsen et al., 1982; Shahidul Isam and Tanaka, 2004). The transport, transformation and fate of particulate material in coastal waters, involving natural hydrodynamic processes at both vertical and horizontal scales as well as processes of aggregation and disaggregation, are thus extremely complex.
In most parts of the ocean, the mean flow is mainly horizontal with only local and intermittent vertical upwelling or downwelling. Horizontal eddies can be large and energetic, leading to effective horizontal dispersion, typically with more energy at larger length scales (Thorpe, 2005). Vertical eddies are smaller and less energetic, but nevertheless constitute the main vertical transport mechanism for soluble substances outside of areas of upwelling or downwelling (Talley et al., 2011). Particles can be positive, negative or neutral in buoyancy; for particles of similar density, the larger ones will sink faster (Lynch et al., 2015). Small particles (<5 µm), however, are virtually non-sinking (<1 m d–1), even if their densities are more than double that of the surrounding water. Aggregation processes can increase the sinking velocities of organic particles, so that larger aggregates composed of many particles (>0.5 mm in size) can have sinking rates of several tens to hundreds of meters per day (Asper, 1987; Alldredge et al., 1990; Berelson, 2001), providing a substantial vertical flux of particles to the seafloor (Burd and Jackson, 2009; Turner, 2015; Figure 2) as part of the ‘biological carbon pump’ (Volk and Hoffert, 1985). Large and heavy particles will sink quickly and only be transported a small distance by horizontal mean flow. Particles with slow sinking velocities will move considerably in the direction of the mean flow while sinking.
The sinking of particles leads to an accumulation close to the seafloor, forming a benthic nepheloid layer, often coinciding with the bottom boundary layer (BBL). The currents in the BBL are exposed to friction against the seafloor, which causes a velocity shear, which in turn induces turbulence. The turbulence can keep particles in the BBL in suspension for a long time (months), transporting them long distances, depending on the velocity in the BBL (Thorpe, 2005). Particles in the BBL will eventually be deposited on the seafloor, contributing to a new top layer of sediment. If the currents in the BBL are strong, the frictional forces can cause erosion of sediments, leading to resuspension of particles and reversion of the deposition. The combined effect of deposition and erosion determines the accumulation rate at any given location. On erosion bottoms the accumulation rate is negative; on transport bottoms the deposition and erosion are in balance, yielding zero accumulation rates. Particularly in coastal zones, wave-induced energy and strong bottom currents are the natural processes that easily resuspend sediments and keep them in suspension (Simpson and Sharples, 2012; Figure 2). As a generality, larger particles require stronger flows to be eroded. For smaller particles, the cohesive forces are more effective; they therefore also require stronger currents to be eroded. According to the classical Hjulström curve (Sundborg, 1956), particles around 0.2 mm are the ones that are most easily eroded, requiring flow velocities of approximately 20 cm s–1. However, Hjulström conducted his investigation in the Swedish river Klarälven, where particles are mostly of mineral origin. More recent research has shown that the onset of cohesive forces and the critical erosion velocities vary not only with particle size, but also depend on organic content and composition (Thomsen, 2003). On the one hand, particles with an organic content are typically less dense than mineral particles, hence requiring lower flow velocities to erode; on the other hand, the presence of microbial exudates can also increase adhesive forces and stabilize sediments (Dade et al., 1990; Thomsen and Gust, 2000; Son and Hsu, 2011).
Along the waters adjacent to the Swedish coastline, sedimentation processes are mostly controlled by currents and motion in the benthic boundary layer via surface wave action (Corell and Döös, 2013), with the seasonal thermocline being significant for the water column stratification typically found in Baltic Sea waters (Leppäranta and Myrberg, 2009). Sinking and suspension processes at both the small and large scale therefore need to be well understood, which requires the application of a combination of various techniques and disciplines. Corell and Döös (2013), for example, used a 3D ocean circulation model combined with an off-line particle-tracking model to evaluate the potential movement of sediment at two geomorphologically different areas off the Swedish east coast, as part of an assessment of where to locate a future underground nuclear repository. As with most models, assumptions have to be made and certain factors are not fully parameterized, which means this model has its shortcomings. They include the lack of a turbulence model to account for particle dynamics in areas of low mixing and the lack of a functional model regarding wind-induced short surface waves (Corell and Döös, 2013). In another study, Kuhrts et al. (2004) simulated the transport of sedimentary material in the western Baltic. They coupled a 3D ocean circulation model to both a wave model and a BBL model, but did not use particle-tracking. Both Corell and Döös (2013) and Kurhts et al. (2004) represent valid modelling approaches, but neither included aggregation and disaggregation of particles. Jackson and Burd (2015) have thoroughly reviewed these processes and the different approaches to modelling them. Scientists need to think broadly and in multi-disciplinary terms, including aspects such as biological activity.
Many studies have revealed the complexity of erosion and deposition processes, including the importance of sediment and seafloor characteristics and of biological activity (see, e.g., Lynch et al. (2015), for a thorough description of both theoretical and modelling approaches). Graf and Rosenberg (1997) show in their review that benthic organisms significantly alter both deposition and erosion, often increasing the physically induced deposition and erosion by a factor of two or more. Organisms exert this effect directly by interacting with the particles in the sediment and in the BBL, or indirectly by altering the sediments and seafloor and the dynamics of the current flow.
Aggregation increases the sinking velocities of their composite organic particles and is therefore an efficient mechanism rapidly removing photosynthetically fixed CO2 from the surface of the ocean (Turner, 2015; Figure 2). Aggregation itself is controlled primarily by three factors: (1) the characteristics of the composite particles, such as their origin (e.g., diatoms, coccolithophores, fecal material, lithogenic input, etc.), concentration, density, size distribution and shape; (2) the physical mechanisms that lead to the collision of suspended particles, including Brownian motion and diffusion, differential settling, and turbulent shear; and (3) the stickiness of the particles, which can influence the probability of particles staying together after they have collided (Alldredge and Silver, 1988; Jackson, 1990; Kiørboe et al., 1994; Beauvais et al., 2006; Burd and Jackson, 2009). Regarding the physical mechanisms, Brownian motion generally relates to nanoparticles and macromolecules which move with rapidly changing direction on the nanometer scale, causing collisions between particles in the nanometer to submicron size domains and perikinetic aggregation (Elimelech et al., 1995). For slowly diffusing micrometer-sized particles such as clay particles, which are frequently dominant in estuarine ecosystems, orthokinetic movements (smaller and larger sizes moving with different speeds under turbulent shear) are more important for their collisions and aggregation (McCave, 1984), while for even larger particles and aggregates, such as millimeter-sized marine snow, differential settling becomes the dominant collision and aggregation process (Burd and Jackson, 2009). Aggregation due to the differential settling velocities of particles is particularly important for particles of dissimilar size in environments with low turbulence, while in the upper ocean and coastal environments, small-scale turbulence brings particles together to collide and form aggregates (McCave, 1984; Jackson, 1990; Kiørboe, 1997).
In turbulent environments the formation and presence of gel-forming extracellular polymeric substances (EPS) and resulting larger (particulate) structures such as TEP play a critical role for aggregation processes, as it is the stickiness of TEP that ‘glues’ together other particles (Passow, 2002; Bar-Zeev et al., 2015) and affects the overall morphology of resulting aggregates (Stoll and Buffle, 1998). An increase in stickiness can lead to higher coagulation efficiency and subsequently enhanced particle flocculation (Beauvais et al., 2006). Turbulence may increase the coagulation processes of TEP, but stronger turbulence may also increase disaggregation (Riebesell, 1992; Ruiz and Izquierdo, 1997) and maintain the TEP pool suspended in surface waters (Beauvais et al., 2006). TEP can even be positively buoyant and thus reduce sinking velocities of aggregates and vertical C fluxes (Azetsu-Scott and Passow, 2004; Mari et al., 2017). The effect of turbulent flows on TEP production itself is not fully understood, although it does appear to increase with the intensity of turbulence (Beauvais et al., 2006; Pedrotti et al., 2010).
In relation to anthropogenic impacts, questions arise on how the presence of biopolymers such as TEP affects, for example, the water quality of intake waters of aquaculture activities. How do such biopolymers affect the aggregation processes of microplastics, and how are nanoparticles attaching to these polymers? An interdisciplinary approach addressing the relevant physics, chemistry and biology of such systems is needed; it could be used, for example, to better understand the impact of aggregate properties and TEP produced by diatoms and other microalgae on the exchange of gases, nutrients, and solutes between sinking aggregates and the ambient water. Combining techniques such as laboratory analyses for TEP production (Engel, 2009), microsensor profiling (measuring chemical species such as O2 and NH4+; e.g., Ploug and Bergkvist, 2015), and particle image velocimetry (Ploug and Jørgensen, 1999; Kiørboe et al., 2001) can provide a holistic understanding of the occurring processes (Ploug and Jørgensen, 1999; Ploug, 2001; Ploug and Passow, 2007), preferably in a setting very similar to the natural environment. Hence, aggregates are studied in vertical flow chambers, in which aggregates are stabilized in the water by an upward flow velocity that balances their natural sinking velocity, thus allowing aggregates to be examined under hydrodynamic conditions similar to those of sinking aggregates (Ploug and Jørgensen, 1999).
Both natural and synthetic particles co-occur in the marine environment. Their physicochemical behavior and interactions with each other, in relation to the physical and chemical dynamics of coastal seawater, and their impacts on marine ecosystem components can, however, differ, and particularly in terms of their inherent toxicity and their propensity to act as carriers for other associated pollutants.
Heavy metals and many organic pollutants frequently have their first point of entry to the ocean via coastal ecosystems (Figure 2). They may enter as solutes but associate to a large extent with natural particles, through sorption or incorporation. Particle association influences both their bioavailability and transport behavior in estuarine and coastal waters (Gustafsson and Gschwend, 1997; Lead et al., 1999). Colloids, the smallest non-settling particles, are primarily responsible for most of the contaminant sorption, which is attributed to their ubiquitous abundance and large specific surface area with many efficient binding sites. To a large extent colloids bind most metals in freshwaters (Lyvén et al., 2003); as an example, iron oxide colloids act as so-called ‘nanovectors’ for transport of lead from soils through rivers to the sea (Hassellöv and von der Kammer, 2008). The role of particles for sorbing organic pollutants is less well studied, but endocrine disruptors, pharmaceuticals and polycyclic aromatic hydrocarbons (PAHs) have been found to partition effectively with colloids (Gustafsson et al., 2001; Liu et al., 2005; Maskaoui et al., 2007). In estuaries most colloids are aggregating colloids, with the contaminants largely following the fate of the aggregates, including the persistence of stabilized, organic-rich aggregates in coastal waters (e.g., Stolpe and Hassellöv, 2010).
In the last decade the extensive research and development efforts within nanoscience and nanotechnology have led to numerous products containing nanomaterials in all application areas, from cosmetics to coatings and antimicrobial textiles (Corsi et al., 2014). There is an increasing concern about the risks associated with nanoparticles to ecosystems due to the special reactivity of many nanomaterials (Handy et al., 2008). Initially, the marine environment did not receive as much research attention as freshwater environments, but scientists are now investigating the emission patterns, behavior and transport, and ecotoxicity of nanoparticles to key components of marine ecosystems (Corsi et al., 2014; Callegaro et al., 2015). Especially important are the physicochemical dynamics that occur in the strong salinity gradients of estuaries and the role of natural organic matter interactions in colloidal behavior and aggregation processes. To advance the study of these processes, the development of highly sensitive and selective analytical and characterization techniques, adapted specifically for nanoparticles in seawater, is needed.
Microplastics released into the marine environment are also intricately linked to the natural marine particle matrix and have the potential to affect, as well as be affected by, the dynamic processes that control vertical particle transportation (Figure 2). Microplastics released into the coastal zone are a heterogeneous group of particles, including preproduction pellets (Lechner et al., 2014), fibers from textiles (Browne et al., 2011), microbeads from cosmetic products (Napper et al., 2015) and fragmented plastic debris to name only a few sources. In order to understand their interactions in the environment, one must distinguish between different types of plastics (Browne et al., 2011). They can be divided into two broad main categories: floating and sinking particles. Microplastics from material with a higher density than water, such as polyvinyl chloride (PVC), polyethylene terephthalate (PET) and most polyamides, are expected to sink more readily compared to, for example, polyethylene and polypropylene, which have a typical density of 0.9–1 g cm–3 (Wright et al., 2013). Moreover, transport will also be affected by the size and the shape of the particles (Ballent et al., 2012). Smaller particles, for example, have a lower rise velocity and are more affected by vertical transport (Reisser et al., 2015). A release of less buoyant microplastics can therefore lead to higher concentrations close to the emission source, thus causing a more localized pollution problem, whereas buoyant plastics can be transported further away from the source.
Plastic degradation can lead to a change in crystallinity which is linked to the material density (Lu et al., 1995; Singh and Sharma, 2008). Additionally, biofouling (Fazey and Ryan, 2016) and biotransformation (Watts et al., 2015) can change the properties of the material. Subsequently, material that enters the ocean as buoyant can become less buoyant over time. Holmström (1975) found polyethylene on the ocean floor already in the 1970s. Fazey and Ryan (2016) evaluated the effect of biofouling on buoyant microplastic and found that particles showed a 50% probability of sinking after an exposure of between 17 and 66 days only. The rates of degradation and biofilm formation are likely to be further affected by seasonal variations of UV radiation, temperature and biological activity (Fazey and Ryan, 2016; Weinstein et al., 2016). Further studies where low-density types of particles are being found in sediment samples also confirm the effect of biofouling on sedimentation processes (Thompson et al., 2004; Morét-Ferguson et al., 2010; Browne et al., 2011; Chubarenko et al., 2016). In samples from different environments off the west coast of Sweden (Figure 3), microplastic composition in terms of polymer type, level of degradation and biofouling was studied using techniques such as Fourier transform infrared spectroscopy (FTIR; Figure 3), image analysis, scanning electron microscopy and Raman spectroscopy (Hidalgo-Ruz et al., 2012; Fries et al., 2013; Rocha-Santos and Duarte, 2015; Karlsson et al., 2016) in the laboratory and indicated that the particles had undergone degradation. Microplastic particles are thereby known to be affected by degradation, biofouling and biotransformation, and also to interact with the natural particle matrix of marine snow (Van Cauwenberghe et al., 2013; Wright et al., 2013). Once incorporated, microplastic particles have the potential to change the normal sinking rate of the aggregates themselves (Long et al., 2015) and may thus influence the role of aggregates within the biological carbon pump, particularly in the coastal zone.
All of these factors can, individually and in combination with each other, affect the buoyancy and sinking/settling properties of the particles, which in turn will affect their vertical and horizontal transportation, likely explaining some of the discrepancies observed between modelled amounts of plastic material entering the environment and what is found in field samples. In the future, predictive transport and fate models need to consider the effects of degradation, polymer type and particle size. In order to better understand how these factors affect transportation, particles found in field samples need to be analyzed for material composition using chemical analysis and imaging techniques such as FTIR or Raman. Because the material changes with degradation and biofouling, studies of these processes are vital both to predict fate of the material and to accurately interpret the findings in field samples.
Particle inputs to the coastal zone due to human activities are not restricted to synthetic micro- and nanoparticles, but also occur as a consequence of other activities such as aquaculture. Aquaculture activities take a variety of forms: net cages in the ocean, flow-through systems such as open raceways, intertidal or pond aquaculture, and land-based tank systems (Figure 2). In all of these instances, the discharge of particulate matter is of concern, but is particularly important in open-net fish cages, where outflows of waste are difficult to control (Brager et al., 2015). Uneaten food and fecal matter may settle below and around farm sites leading to deposition of organic matter that can be up to 20 times higher than background values (Tlusty et al., 2000). Water transport processes are important as particle dispersion patterns are influenced by particle size and flocculation, tidal flow, topography and residual circulation, turbulence, as well as wind and wave energy (Lander et al., 2013; Law et al., 2016). Because smaller particles remain longer in the water column, they have a greater tendency for horizontal movement: airborne dust from feed pellet distributors for instance can be carried even greater distances by wind, or transported in surface films (Hargrave, 2003). Dissolved waste products have been recorded up to 1 km away, while particulate sedimentation from aquaculture sites can affect the benthic environment to a radius of 100 m around farm sites (Sarà et al., 2004). The composition of particulate waste depends on the farming methods, species, feed quality, management practices and stocking density, but the settlement of particulates is consistent, resulting in increased turbidity (Bongiorni et al., 2003) and an increase of organic solids that eventually settle on the sediment under and near farms (Tomassetti et al., 2016). Changes in sediment biogeochemistry due to anoxic conditions, including the production of hydrogen sulfide, ammonium, and methane, in turn affect the marine environment by altering the habitat and community composition of all levels of flora and fauna (bacteria, seagrasses, meiofauna and macrofauna; see, for example, Holmer et al., 2005; Hargrave, 2010; Martinez-Garcia et al., 2015).
Aquaculture practices, however, are not only a source of particulates but are themselves also affected by other particles already present in the environment (Figure 2). Human activities such as urbanization, construction, agriculture, and mining cause short-term or long-term increases in particulates at aquaculture sites that have been shown to negatively impact spawning, growth and reproduction (Bash et al., 2001). What effect the intake of microplastics and other pollutants have is not well documented, but hatcheries are particularly vulnerable to small fluctuations in water quality at their intakes (Attramadal et al., 2016). The existence of TEP, an important particle type in aggregate formation, is often overlooked in relation to aquaculture activities, especially in hatcheries (Joyce and Utting, 2015).
Although resuspension of sediments occurs in shallow (<5 m depth) and deeper coastal waters as a consequence of natural transport processes and events (Figure 2), sediments are also resuspended by human activities such as bottom trawling (Ferré et al., 2008), dredging (Newell et al., 1998; Essink, 1999) and drilling (Khondaker, 2000). Bottom trawling affects the seafloor (Puig et al., 2012; Martín et al., 2014b), but also the water column above it (O’Neill and Summerbell, 2011; Bradshaw et al., 2012) by suspending sediments from the seafloor (Figure 2). This action may result in the relocation of sediment to deeper areas (Martín et al., 2014a) and even in sediment gravity flows (Palanques et al., 2006). Resuspension of sediments may reduce the organic content of the surface layer (Pusceddu et al., 2014) and mobilize nutrients (Dounas et al., 2007) and contaminants (Bradshaw et al., 2012). Elevated turbidity may reduce light, thus affecting primary producers (e.g., seagrasses) in shallow waters (Moore et al., 1997; Essink, 1999; De Boer, 2007). Elevated turbidity can also affect egg and larvae of fish and invertebrates, through adherence-associated loss in buoyancy of the egg, the disturbance of larval settlement behavior, and increased mortality (Gilmour, 1999; Westerberg et al., 1996), and affect aquaculture activities. Changes in the quality and size of suspended particles may affect feeding and oxygen consumption by suspension feeders such as sponges (Tjensvoll et al., 2013; Kutti et al., 2015), while fish may be affected by fine particles that clog their gills (Humborstad et al., 2006).
The mechanical force of a trawl lifts resuspended particles into a plume that rises above the seabed. The same force creates strong vertical mixing. In stratified waters this forcing will lead to local vertical homogenization. The plume thus not only has high particle concentrations and turbidity, but also has a density that deviates from its surrounding. Pressure gradients will force the plume to intrude the surrounding water at its neutral density level (Thorpe, 2005). In stratified waters this process thus enhances dispersion of trawl plumes and associated particles.
The Kosterhavet National Park on the west coast of Sweden is well suited for investigating the sediment resuspension effect from trawling (Figure 4), but this effort requires an interdisciplinary approach with physical oceanographers, marine biologists and fishery experts. It also requires the application of multiple methods, including fishing vessel monitoring and use of state-of-the-art instrumentation, such as the Laser in-situ Scattering and Transmissometry (LISST) particle analyzer (Agrawal and Pottsmith, 2000). In the National Park, trawling activity is restricted to the weekdays Monday–Thursday, with closures in place from Friday to Sunday. Multiple investigations of the turbidity on Sunday (last day of closure) and the following Monday (first day of trawling) have allowed for quantification of the effect, as exemplified in Figure 4B. In Kosterhavet, the trawling activity has an impact on the turbidity at depths where trawling occurs. The average effect on the turbidity is moderate, 0.05 NTU compared to background levels after one day of trawling. However, the variation increases by as much as 75%, with many more instances of high turbidity, and the background level is also likely affected by the trawling (Wikström et al., 2016; Linders et al., 2017).
Dredging has similar effects on particles and their transport as trawling. Resuspension occurs during both the removal and eventual disposal of the dredged material (Netzband and Adnitt, 2009). Turbidity is increased, and enhanced deposition at dump sites impacts the benthic fauna and flora (Newell et al., 1998; Essink, 1999). Dredging often takes place in heavily industrialized areas, such as harbors, which may lead to the mobilization of contaminated sediments (Fichet et al., 1998; Essink, 1999; Sturve et al., 2005). One of the most important drivers for dredging is the increasing seaborne trade as shipping channels and ports are maintained and expanded (IADC, 2015). Several Nordic governments have expressed an ambition to expand the seaborne transport capacity: for example, Norway’s ‘National Transport Plan 2018–2029’ (www.regjeringen.no/no/dokumenter/meld.-st.-33-20162017, in Norwegian), and the Swedish Maritime Administration’s 2016 report on the potential for short sea shipping (http://www.sjofartsverket.se/pages/106206/Slutrapport_rev_2017-01-17.pdf, in Swedish). Further drivers for dredging also include the increasing pressures on coasts and their waters due to population growth, energy demands and development of water-related tourism, as well as the need for coastal protection (IADC, 2015).
Benthic organisms present in coastal and deeper waters actively contribute to the resuspension and trapping of particles (Graf and Rosenberg, 1997). Bioturbators, such as the lugworm Arenicola marina, can destabilize the sediment by reworking and loosening the top grains of the sedimentary matrix. In contrast, bacterial biofilms and sedentary organisms, such as tube-builders (e.g., Polydora cornuta and Lanice conchilega) and seagrass meadows, can stabilize the sediment by binding sediment particles (Fonseca, 1989; Delgado et al., 1991; Volkenborn et al., 2008). Benthic organisms can thus modify the bottom topography, which can alter interactions with near bottom velocities. For example, coastal submerged vegetation such as seagrass can increase the bottom roughness and the height of the benthic boundary layer (Infantes et al., 2012). In shallow areas (<5 m depth), the hydrodynamics of waves and currents are among the main factors increasing water turbidity by resuspending sediment. This sediment in suspension alters the water quality and reduces the light penetration depth, until particles settle to the seabed or are redistributed (De Boer, 2007). Water transparency is crucial, however, for submerged coastal vegetation because they need high levels of light for growth and development (Duarte, 1991). Sediment stabilization by vegetation maintains good water quality, representing a positive feedback that keeps light available for the plants (van der Heide et al., 2007; Maxwell et al., 2016) (Figure 5A).
Seagrasses are common in Nordic coastal waters and, as ecosystem engineers, modify both the biotic and the abiotic environment of their ecosystem. They can reduce flow velocities and attenuate waves (Bouma et al., 2005; Infantes et al., 2012), and thus decrease turbidity through the reduction of fine suspended sediment particles in the water column which accumulate instead within the seagrass meadow (Ward et al., 1984). Seagrasses are able to affect particle flux directly through loss of momentum and increased path length from particle collisions with leaves (Hendriks et al., 2008). A large-scale recovery of the seagrass Zostera marina in the US after restoration showed a dramatic decrease in the water turbidity once the seagrass was established, indicating the positive feedback of aquatic vegetation (Orth et al., 2012). Other benthic organisms such as filter feeders (e.g., the mussel Mytilus edulis) increase biodeposition by trapping nutrients and particles from the water column (Kautsky and Evans, 1987). The use of mussel farms to improve water quality has been suggested in Sweden by Lindahl et al. (2005), because they were estimated to reduce 20% of the total dissolved and particulate nitrogen in the water.
However, in areas where vegetation has been affected negatively by anthropogenic causes (e.g., eutrophication, dredging, fishing activities, coastal development), flow velocities are higher than in existing vegetated beds, resulting in sediment resuspension events that prevent plant development. For example, in the area of Marstrand on the Swedish west coast, 90% of the eelgrass Zostera marina has been lost since the 1980s (Baden et al., 2003). Studies suggest that the primary mechanism behind the decline is an increased abundance of ephemeral algal mats, caused by eutrophication in combination with overfishing, that cover the eelgrass beds during the summer, and which have caused a trophic cascade that promotes growth of the algae (Moksnes et al., 2008; Baden et al., 2010; Baden et al., 2012). Despite decreasing nutrient loads to the coastal waters, there has not been a natural recovery of eelgrass (Nyqvist et al., 2009; SwAM, 2012). In these sites, turbidity is high due to the resuspension of fine clay particles (Figure 5B), and thus light penetration is low. In locations where the environment has shifted from a vegetated state to a state of bare sediment (e.g., Marstrand, Sweden), seagrass restoration could be challenging as particle resuspension and turbidity are preventing plant establishment (Infantes et al., 2016b; Moksnes et al., 2016). Others factors might also prevent restoration, including the presence of predators and bioturbators, the sediment composition, hydrodynamics or light (Infantes et al., 2011; Eriander et al., 2016; Infantes et al., 2016a), such that additional management plans might be needed.
Seagrass ecosystems provide important services in coastal seas by supporting high biodiversity (Duffy et al., 2015), reducing coastal erosion by attenuating waves (Infantes et al., 2012; Luhar et al., 2017), trapping particles and reducing resuspension (Hendriks et al., 2008), trapping CO2 and functioning as carbon sinks (Röhr et al., 2016). Management actions are needed to break feedbacks that are preventing seagrass development and to promote plant growth with regard to seagrass restoration. For example, temporary floating wave barriers to attenuate waves and reduce sediment resuspension could be implemented until vegetation is established. Adding coarse sand over fine muddy sediments (sand-capping) before restoration could also be used as a measure to reduce resuspension and improve water clarity for plant growth. Yet, before these actions are implemented, it is necessary to understand the local coastal hydrodynamics to ensure their efficiency and prevent further environmental degradation.
The coastal zone is a highly dynamic environment and frequently the first point of entry for many natural as well as anthropogenic particles such as microplastics, heavy metals and waste from aquaculture activities. We have highlighted the particular importance of particles in stratified coastal waters and estuaries, their roles in natural processes, their formation and transport, and their interactions with anthropogenic activities. We have further stressed their complexity and emphasized the need for interdisciplinary approaches involving marine biologists, chemists, geologists and physical oceanographers to achieve a mechanistic understanding of particle processes in the coastal waters of the Anthropocene. Raising our understanding of particles and our ability to manage coastal waters will require investigations in controlled laboratory and mesocosm settings, actual in situ observations of the coastal ocean, and incorporation of relevant processes into numerical models.
We have identified two areas of research that are fundamental to our understanding of particle transport and that demand more research attention: the role of turbulence, and the size spectra and abundance of particles. Turbulence is important for small-scale and large-scale production, transport and transformation of organic particles in marine environments. Yet, our quantitative and mechanistic understanding of the influence of turbulence on these processes remains poor. In future studies, we propose new combinations of in situ approaches to quantify turbulence in relation to particle size spectra and abundance, with ex situ laboratory studies to improve our mechanistic understanding of particle dynamics. In situ monitoring may involve a wider range of optical and multi-frequency acoustic sensors. Novel laboratory approaches may involve holographic microscopy and confocal microscopy for analysis of 3D particle composition of, for example, TEP, in addition to chemical analysis of composite particles and their diversity.
Particle parameters often display higher natural variability than other hydrographic parameters. Given this variability and the interest in expanding trawling and dredging activities, frequent monitoring of particle parameters is warranted. Particle size is one of the most defining parameters, but particle size distribution remains largely unmapped in most of the Nordic coastal ocean and lacking in current monitoring efforts. Today off-the-shelf optical sensors for in situ measurements of particle size distribution exist, including sensors using near forward scattering (Agrawal and Pottsmith, 2000), macroscopic imaging (e.g., Picheral et al., 2010), and holographic imaging (Davies et al., 2015). Some of these sensors could easily be included into existing monitoring programs.
Advancing understanding of both topics would thus benefit from improved water column monitoring. Currently, vertical profile monitoring is carried out once per month or less in most of the Nordic waters (http://marine.copernicus.eu/) and largely conducted from research vessels. Expecting this costly form of monitoring activity to expand is unrealistic. We suggest the expansion of automated or semi-automated monitoring, well exemplified with the FerryBox on commercial ships along diverse routes (www.ferrybox.org) and with monitoring buoys and moorings within the joint European JERICO project (www.jerico-ri.eu/). The JERICO project (Puillat et al., 2016) aims to integrate the existing automated systems for operational monitoring of the coastal and shelf seas and to stimulate the development of new systems. However, too little is done currently and what is implemented scarcely covers the coastal zone. A fundamental problem is that we need to monitor the whole water column, from the sea surface to the seafloor. This requirement could be achieved from a mooring with multiple sensor packages arranged on a vertical line or possibly by one sensor package moving along a vertical line. The Wirewalker is a successful example of the approach with a moving package, with package movement powered by the ocean waves, creating vertical heaving of the wire suspended beneath a surface buoy (Pinkel et al., 2011; Lucas et al., 2017). Another more flexible option is to use unmanned gliders. This technology has come of age, with proven reliability, decreasing costs, and the capability of hosting many types of sensors (Rudnick, 2016), recently including sensors for particle size distribution (e.g., www.sequoiasci.com).
We thank Matthias Obst for providing feedback to our manuscript. Symbols used in Figures 2 and 5 are courtesy of the Integration and Application Network, University of Maryland Center for Environmental Science (ian.umces.edu/symbols/). We thank anonymous reviewers and the journal editors for their valuable comments in helping to improve this manuscript.
TL was funded by The County Administrative Board of Västra Götaland, project “Investiagtion of the effect of trawling on turbidity and sedimentation”. EZ is funded by a Maria Skłodowska Curie Action, project no. MSCA_IF_GA_660481. TK and MH acknowledge funding from the Swedish Research Council FORMAS (Grant number 2014-1146) and the Interreg project Clean Coastline, and HP from the Swedish Research Council (Dnr: 2015-05322). EI would like to thank FORMAS grant Dnr. 231-2014-735.
The authors have no competing interests to declare.
Agrawal, Y and Pottsmith, H 2000 Instruments for particle size and settling velocity observations in sediment transport. Mar Geo 168(1): 89–114. DOI: 10.1016/S0025-3227(00)00044-X
Alldredge, AL, Granata, TC, Gotschalk, CC and Dickey, TD 1990 The physical strength of marine snow and its implications for particle disaggregation in the ocean. Limnol Oceanogr 35(7): 1415–1428. DOI: 10.4319/lo.1918.104.22.1685
Alldredge, AL and Silver, MW 1988 Characteristics, dynamics and significance of marine snow. Prog Oceanogr 20(1): 41–82. DOI: 10.1016/0079-6611(88)90053-5
Asper, VL 1987 Measuring the flux and sinking speed of marine snow aggregates. Deep Sea Res A 34(1): 1–17. DOI: 10.1016/0198-0149(87)90117-8
Attramadal, KJ, Minniti, G, Øie, G, Kjørsvik, E, Østensen, M-A, et al. 2016 Microbial maturation of intake water at different carrying capacities affects microbial control in rearing tanks for marine fish larvae. Aquaculture 457: 68–72. DOI: 10.1016/j.aquaculture.2016.02.015
Azetsu-Scott, K and Passow, U 2004 Ascending marine particles: significance of transparent exopolymer particles (TEP) in the upper ocean. Limnol Oceanogr 49(3): 741–748. DOI: 10.4319/lo.2004.49.3.0741
Baden, S, Boström, C, Tobiasson, S, Arponen, H and Moksnes, P-O 2010 Relative importance of trophic interactions and nutrient enrichment in seagrass ecosystems: A broad-scale field experiment in the Baltic-Skagerrak area. Limnol Oceanogr 55(3): 1435–1448. DOI: 10.4319/lo.2010.55.3.1435
Baden, S, Emanuelsson, A, Pihl, L, Svensson, C-J and Åberg, P 2012 Shift in seagrass food web structure over decades is linked to overfishing. Mar Ecol Prog Ser 451: 61–73. DOI: 10.3354/meps09585
Baden, S, Gullström, M, Lundén, B, Pihl, L and Rosenberg, R 2003 Vanishing seagrass (Zostera marina, L.) in Swedish coastal waters. Ambio 32(5): 374–377. DOI: 10.1579/0044-7447-32.5.374
Ballent, A, Purser, A, Mendes, PdJ, Pando, S and Thomsen, L 2012 Physical transport properties of marine microplastic pollution. Biogeosci Discuss 9(12): 18755–18798.
Bar-Zeev, E, Passow, U, Romero-Vargas Castrillón, S and Elimelech, M 2015 Transparent exopolymer particles: from aquatic environments and engineered systems to membrane biofouling. Environ Sci Technol 49(2): 691–707. DOI: 10.1021/es5041738
Bash, J, Berman, CH and Bolton, S 2001 Effects of turbidity and suspended solids on salmonids. University of Washington Center for Streamside Studies 80. Available at: http://hdl.handle.net/1773/16382.
Beauvais, S, Pedrotti, ML, Egge, J, Iversen, K and Marrasé, C 2006 Effects of turbulence on TEP dynamics under contrasting nutrient conditions: implications for aggregation and sedimentation processes. Mar Ecol Prog Ser 323: 47–57. DOI: 10.3354/meps323047
Berelson, WM 2001 Particle settling rates increase with depth in the ocean. Deep Sea Res Part II Top Stud Oceanogr 49(1–3): 237–251. DOI: 10.1016/S0967-0645(01)00102-3
Bongiorni, L, Shafir, S and Rinkevich, B 2003 Effects of particulate matter released by a fish farm (Eilat, Red Sea) on survival and growth of Stylophora pistillata coral nubbins. Mar Pollut Bull 46(9): 1120–1124. DOI: 10.1016/S0025-326X(03)00240-6
Bouma, T, De Vries, M, Low, E, Peralta, G, Tánczos, I, et al. 2005 Trade-offs related to ecosystem engineering: A case study on stiffness of emerging macrophytes. Ecology 86(8): 2187–2199. DOI: 10.1890/04-1588
Bradshaw, C, Tjensvoll, I, Sköld, M, Allan, I, Molvaer, J, et al. 2012 Bottom trawling resuspends sediment and releases bioavailable contaminants in a polluted fjord. Environ Pollut 170: 232–241. DOI: 10.1016/j.envpol.2012.06.019
Brager, LM, Cranford, PJ, Grant, J and Robinson, SM 2015 Spatial distribution of suspended particulate wastes at open-water Atlantic salmon and sablefish aquaculture farms in Canada. Aquac Environ Interact 6(2): 135–149. DOI: 10.3354/aei00120
Breuer, E, Stevenson, AG, Howe, JA, Carroll, J and Shimmield, GB 2004 Drill cutting accumulations in the Northern and Central North Sea: a review of environmental interactions and chemical fate. Mar Pollut Bull 48(1–2): 12–25. DOI: 10.1016/j.marpolbul.2003.08.009
Browne, MA, Crump, P, Niven, SJ, Teuten, E, Tonkin, A, et al. 2011 Accumulation of microplastic on shorelines woldwide: sources and sinks. Environ Sci Technol 45(21): 9175–9179. DOI: 10.1021/es201811s
Burd, AB and Jackson, GA 2009 Particle aggregation. Annu Rev Mar Sci 1(1): 65–90. DOI: 10.1146/annurev.marine.010908.163904
Callegaro, S, Minetto, D, Pojana, G, Bilanicová, D, Libralato, G, et al. 2015 Effects of alginate on stability and ecotoxicity of nano-TiO2 in artificial seawater. Ecotoxicol Environ Saf 117: 107–114. DOI: 10.1016/j.ecoenv.2015.03.030
Chubarenko, I, Bagaev, A, Zobkov, M and Esiukova, E 2016 On some physical and dynamical properties of microplastic particles in marine environment. Mar Pollut Bull 108: 105–112. DOI: 10.1016/j.marpolbul.2016.04.048
Corell, H and Döös, K 2013 Difference in particle transport between two coastal areas in the Baltic Sea investigated with high-resolution trajectory modeling. Ambio 42(4): 455–463. DOI: 10.1007/s13280-013-0397-3
Corsi, I, Cherr, GN, Lenihan, HS, Labille, J, Hassellov, M, et al. 2014 Common strategies and technologies for the ecosafety assessment and design of nanomaterials entering the marine environment. ACS Nano 8(10): 9694–9709. DOI: 10.1021/nn504684k
Dade, WB, Davis, JD, Nichols, PD, Nowell, ARM, Thistle, D, et al. 1990 Effects of bacterial exopolymer adhesion on the entrainment of sand. Geomicrobiol J 8(1): 1–16. DOI: 10.1080/01490459009377874
Davies, EJ, Buscombe, D, Graham, GW and Nimmo-Smith, WAM 2015 Evaluating unsupervised methods to size and classify suspended particles using digital in-line holography. J Atmos Ocean Technol 32(6): 1241–1256. DOI: 10.1175/JTECH-D-14-00157.1
De Boer, W 2007 Seagrass–sediment interactions, positive feedbacks and critical thresholds for occurrence: a review. Hydrobiologia 591(1): 5–24. DOI: 10.1007/s10750-007-0780-9
Delgado, M, De Jonge, V and Peletier, H 1991 Experiments on resuspension of natural microphytobenthos populations. Mar Biol 108(2): 321–328. DOI: 10.1007/BF01344347
Dounas, C, Davies, I, Triantafyllou, G, Koulouri, P, Petihakis, G, et al. 2007 Large-scale impacts of bottom trawling on shelf primary productivity. Cont Shelf Res 27(17): 2198–2210. DOI: 10.1016/j.csr.2007.05.006
Duarte, CM 1991 Seagrass depth limits. Aquat Bot 40(4): 363–377. DOI: 10.1016/0304-3770(91)90081-F
Duffy, JE, Reynolds, PL, Boström, C, Coyer, JA, Cusson, M, et al. 2015 Biodiversity mediates top–down control in eelgrass ecosystems: a global comparative-experimental approach. Ecol Lett 18(7): 696–705. DOI: 10.1111/ele.12448
Elimelech, M, Gregory, G, Xia, X and Williams, R 1995 Particle deposition and aggregation . USA: Butterworth-Heinemann.
Engel, A 2009 Determination of marine gel particles. In: Wurl, O (ed.), Practical guidelines for the analysis of seawater , 125–142. Boca Raton: CRC Press. DOI: 10.1201/9781420073072.ch7
Eriander, L, Infantes, E, Olofsson, M, Olsen, JL and Moksnes, P-O 2016 Assessing methods for restoration of eelgrass (Zostera marina L.) in a cold temperate region. J Exp Mar Bio Ecol 479: 76–88. DOI: 10.1016/j.jembe.2016.03.005
Essink, K 1999 Ecological effects of dumping of dredged sediments; options for management. J Coast Conserv 5(1): 69–80. DOI: 10.1007/BF02802741
Fazey, FM and Ryan, PG 2016 Biofouling on buoyant marine plastics: An experimental study into the effect of size on surface longevity. Environ Pollut 210: 354–360. DOI: 10.1016/j.envpol.2016.01.026
Ferré, B, Durrieu de Madron, X, Estournel, C, Ulses, C and Le Corre, G 2008 Impact of natural (waves and currents) and anthropogenic (trawl) resuspension on the export of particulate matter to the open ocean: Application to the Gulf of Lion (NW Mediterranean). Cont Shelf Res 28(15): 2071–2091. DOI: 10.1016/j.csr.2008.02.002
Fichet, D, Radenac, G and Miramand, P 1998 Experimental studies of impacts of harbour sediments resuspension to marine invertebrates larvae: bioavailability of Cd, Cu, Pb and Zn and toxicity. Mar Pollut Bull 36(7): 509–518. DOI: 10.1016/S0025-326X(97)00190-2
Filella, M 2007 Colloidal properties of submicron particles in natural waters. In: Wilkinson, K and Lead, J (eds.), Environmental colloids and particles: behaviour, structure and characterization IUPAC series on analytical and physical chemistry of environmental systems , 17–93. Chichester: John Wiley and Sons.
Fonseca, M 1989 Sediment stabilization by Halophila decipiens in comparison to other seagrasses. Estuar Coast Shelf Sci 29(5): 501–507. DOI: 10.1016/0272-7714(89)90083-8
Fries, E, Dekiff, JH, Willmeyer, J, Nuelle, M-T, Ebert, M, et al. 2013 Identification of polymer types and additives in marine microplastic particles using pyrolysis-GC/MS and scanning electron microscopy. Environ Sci Process Impacts 15(10): 1949–1956. DOI: 10.1039/c3em00214d
Gilmour, J 1999 Experimental investigation into the effects of suspended sediment on fertilisation, larval survival and settlement in a scleractinian coral. Mar Biol 135(3): 451–462. DOI: 10.1007/s002270050645
Goldberg, E, Baker, M and Fox, D 1952 Microfiltration in oceanographic research. 1. Marine sampling with the molecular filter. J Mar Res 11(2): 194–204.
Göransson, G, Larson, M and Bendz, D 2013 Variation in turbidity with precipitation and flow in a regulated river system–river Göta Älv, SW Sweden. Hydrol Earth Syst Sci 17(7): 2529–2542. DOI: 10.5194/hess-17-2529-2013
Graf, G and Rosenberg, R 1997 Bioresuspension and biodeposition: a review. J Mar Syst 11(3–4): 269–278. DOI: 10.1016/S0924-7963(96)00126-1
Gustafsson, O and Gschwend, PM 1997 Aquatic colloids: Concepts, definitions, and current challenges. Limnol Oceanogr 42(3): 519–528. DOI: 10.4319/lo.1997.42.3.0519
Gustafsson, Ö, Nilsson, N and Bucheli, TD 2001 Dynamic colloid-water partitioning of pyrene through a coastal Baltic spring bloom. Environ Sci Technol 35(20): 4001–4006. DOI: 10.1021/es0003019
Hallegraeff, GM 2010 Ocean climate change, phytoplankton community responses, and harmful algal blooms: a formidable predictive challenge. J Phycol 46(2): 220–235. DOI: 10.1111/j.1529-8817.2010.00815.x
Halpern, BS, Walbridge, S, Selkoe, KA, Kappel, CV, Micheli, F, et al. 2008 A global map of human impact on marine ecosystems. Science 319(5865): 948–952. DOI: 10.1126/science.1149345
Handy, RD, Von der Kammer, F, Lead, JR, Hassellöv, M, Owen, R, et al. 2008 The ecotoxicology and chemistry of manufactured nanoparticles. Ecotoxicology 17(4): 287–314. DOI: 10.1007/s10646-008-0199-8
Hargrave, BT 2003 Far-field environmental effects of marine finfish aquaculture. In: Hargrave, BT, Cranford, P, Dowd, M, Grant, B, McGladdery, S, et al. (eds.), Fisheries and Oceans Canada A scientific review of the potential environmental effects of aquaculture in aquatic ecosystems 1(2450): 1–49. Canadian Technical Report of Fisheries and Aquatic Sciences.
Hargrave, BT 2010 Empirical relationships describing benthic impacts of salmon aquaculture. Aquac Environ Interact 1(1): 33–46. DOI: 10.3354/aei00005
Harley, CD, Randall Hughes, A, Hultgren, KM, Miner, BG, Sorte, CJ, et al. 2006 The impacts of climate change in coastal marine systems. Ecol Lett 9(2): 228–241. DOI: 10.1111/j.1461-0248.2005.00871.x
Hassellöv, M and von der Kammer, F 2008 Iron oxides as geochemical nanovectors for metal transport in soil-river systems. Elements 4(6): 401–406. DOI: 10.2113/gselements.4.6.401
Hendriks, IE, Sintes, T, Bouma, TJ and Duarte, CM 2008 Experimental assessment and modeling evaluation of the effects of the seagrass Posidonia oceanica on flow and particle trapping. Mar Ecol Prog Ser 356: 163–173. DOI: 10.3354/meps07316
Hidalgo-Ruz, V, Gutow, L, Thompson, RC and Thiel, M 2012 Microplastics in the marine environment: a review of the methods used for identification and quantification. Environ Sci Technol 46(6): 3060–3075. DOI: 10.1021/es2031505
Holmer, M, Wildish, D and Hargrave, B 2005 Organic enrichment from marine finfish aquaculture and effects on sediment biogeochemical processes. In: Hargrave, BT (ed.), Environmental Effects of Marine Finfish Aquaculture , 181–206. Berlin, Heidelberg: Springer. DOI: 10.1007/b136010
Holmström, A 1975 Plastic films on the bottom of the Skagerack. Nature 255: 622–623. DOI: 10.1038/255622a0
Humborstad, O-B, Jørgensen, T and Grotmol, S 2006 Exposure of cod Gadus morhua to resuspended sediment: an experimental study of the impact of bottom trawling. Mar Ecol Prog Ser 309: 247–254. DOI: 10.3354/meps309247
IADC 2015 Dredging in Figures. The Netherlands: International Association of Dredging Companies: 13. Available at: https://www.iadc-dredging.com/ul/cms/fck-uploaded/documents/PDF%20Dredging%20in%20Figures/dredging-in-figures-2015.pdf.
Infantes, E, Crouzy, C and Moksnes, P-O 2016a Seed predation by the shore crab Carcinus maenas: a positive feedback preventing eelgrass recovery? PLoS One 11(12): e0168128. DOI: 10.1371/journal.pone.0168128
Infantes, E, Eriander, L and Moksnes, P-O 2016b Eelgrass (Zostera marina) restoration on the west coast of Sweden using seeds. Mar Ecol Prog Ser 546: 31–45. DOI: 10.3354/meps11615
Infantes, E, Orfila, A, Bouma, TJ, Simarro, G and Terrados, J 2011 Posidonia oceanica and Cymodocea nodosa seedling tolerance to wave exposure. Limnol Oceanogr 56(6): 2223–2232. DOI: 10.4319/lo.2011.56.6.2223
Infantes, E, Orfila, A, Simarro, G, Terrados, J, Luhar, M, et al. 2012 Effect of a seagrass (Posidonia oceanica) meadow on wave propagation. Mar Ecol Prog Ser 456: 63–72. DOI: 10.3354/meps09754
Jackson, GA 1990 A model of the formation of marine algal flocs by physical coagulation processes. Deep Sea Res A 37(8): 1197–1211. DOI: 10.1016/0198-0149(90)90038-W
Jackson, GA and Burd, AB 2015 Simulating aggregate dynamics in ocean biogeochemical models. Prog Oceanogr 133: 55–65. DOI: 10.1016/j.pocean.2014.08.014
Jeandel, C, van der Loeff, MR, Lam, PJ, Roy-Barman, M, Sherrell, RM, et al. 2015 What did we learn about ocean particle dynamics in the GEOSECS-JGOFS era? Prog Oceanogr 133: 6–16. DOI: 10.1016/j.pocean.2014.12.018
Joyce, A and Utting, S 2015 The role of exopolymers in hatcheries: an overlooked factor in hatchery hygiene and feed quality. Aquaculture 446: 122–131. DOI: 10.1016/j.aquaculture.2015.04.037
Karlsson, TM, Grahn, H, van Bavel, B and Geladi, P 2016 Hyperspectral imaging and data analysis for detecting and determining plastic contamination in seawater filtrates. J Near Infrared Spectrosc 24(2): 141–149. DOI: 10.1255/jnirs.1212
Kautsky, N and Evans, S 1987 Role of biodeposition by Mytilus edulis in the circulation of matter and nutrients in a Baltic coastal ecosystem. Mar Ecol Prog Ser , 201–212. DOI: 10.3354/meps038201
Khondaker, AN 2000 Modeling the fate of drilling waste in marine environment — an overview. Comput Geosci 26(5): 531–540. DOI: 10.1016/S0098-3004(99)00135-1
Kiørboe, T 1997 Small-scale turbulence, marine snow formation, and planktivorous feeding. Sci Mar 61(1): 141–158.
Kiørboe, T, Lundsgaard, C, Olesen, M and Hansen, JLS 1994 Aggregation and sedimentation processes during a spring phytoplankton bloom: A field experiment to test coagulation theory. J Mar Res 52(2): 297–323. DOI: 10.1357/0022240943077145
Kiørboe, T, Ploug, H and Thygesen, UH 2001 Fluid motion and solute distribution around sinking aggregates I: Small-scale fluxes and heterogeneity of nutrients in the pelagic environment. Mar Ecol Prog Ser 211: 1–13. DOI: 10.3354/meps211001
Kritzberg, E and Ekström, S 2012 Increasing iron concentrations in surface waters – a factor behind brownification? Biogeosciences 9(4): 1465–1478. DOI: 10.5194/bg-9-1465-2012
Kuhrts, C, Fennel, W and Seifert, T 2004 Model studies of transport of sedimentary material in the western Baltic. J Marine Syst 52(1): 167–190. DOI: 10.1016/j.jmarsys.2004.03.005
Kutti, T, Bannister, RJ, Fosså, JH, Krogness, CM, Tjensvoll, I, et al. 2015 Metabolic responses of the deep-water sponge Geodia barretti to suspended bottom sediment, simulated mine tailings and drill cuttings. J Exp Mar Bio Ecol 473: 64–72. DOI: 10.1016/j.jembe.2015.07.017
Lander, T, Robinson, S, MacDonald, B and Martin, J 2013 Characterization of the suspended organic particles released from salmon farms and their potential as a food supply for the suspension feeder. Mytilus edulis in integrated multi-trophic aquaculture (IMTA) systems. Aquaculture 406: 160–171. DOI: 10.1016/j.aquaculture.2013.05.001
Law, B, Hill, P, Milligan, T and Zions, V 2016 Erodibility of aquaculture waste from different bottom substrates. Aquac Environ Interact 8: 575–584. DOI: 10.3354/aei00199
Lead, J, Hamilton-Taylor, J, Davison, W and Harper, M 1999 Trace metal sorption by natural particles and coarse colloids. Geochim Cosmochim Acta 63(11): 1661–1670. DOI: 10.1016/S0016-7037(99)00006-X
Lechner, A, Keckeis, H, Lumesberger-Loisl, F, Zens, B, Krusch, R, et al. 2014 The Danube so colourful: a potpourri of plastic litter outnumbers fish larvae in Europe’s second largest river. Environ Pollut 188: 177–181. DOI: 10.1016/j.envpol.2014.02.006
Leppäranta, M and Myrberg, K 2009 Physical oceanography of the Baltic Sea . Berlin: Springer Science & Business Media. DOI: 10.1007/978-3-540-79703-6
Lindahl, O, Hart, R, Hernroth, B, Kollberg, S, Loo, L-O, et al. 2005 Improving marine water quality by mussel farming: A profitable solution for Swedish society. Ambio 34(2): 131–138. DOI: 10.1579/0044-7447-34.2.131
Linders, T, Nilsson, P, Wikström, A and Sköld, M 2017 Distribution and fate of trawling-induced suspension of sediments in a marine protected area. ICES J Mar Sci , In press. DOI: 10.1093/icesjms/fsx196
Liu, R, Wilding, A, Hibberd, A and Zhou, JL 2005 Partition of endocrine-disrupting chemicals between colloids and dissolved phase as determined by cross-flow ultrafiltration. Environ Sci Technol 39(8): 2753–2761. DOI: 10.1021/es0484404
Long, M, Moriceau, B, Gallinari, M, Lambert, C, Huvet, A, et al. 2015 Interactions between microplastics and phytoplankton aggregates: Impact on their respective fates. Mar Chem 175: 39–46. DOI: 10.1016/j.marchem.2015.04.003
Lu, X, Qian, R and Brown, N 1995 The effect of crystallinity on fracture and yielding of polyethylenes. Polymer 36(22): 4239–4244. DOI: 10.1016/0032-3861(95)92219-5
Lucas, AJ, Pinkel, R and Alford, M 2017 Ocean wave energy for long endurance, broad bandwidth ocean monitoring. Oceanography 30(2): 126–127. DOI: 10.5670/oceanog.2017.232
Luhar, M, Infantes, E and Nepf, H 2017 Seagrass blade motion under waves and its impact on wave decay. J Geophys Res Oceans 122: 3736–3752. DOI: 10.1002/2017JC012731
Lynch, DR, Greenberg, DA, Bilgili, A, Mcgillicuddy, J, Dennis, J, Manning, JP, et al. 2015 Particles in the Coastal Ocean: Theory and Applications . 1st ed., Cambridge University Press. DOI: 10.1017/CBO9781107449336
Lyvén, B, Hassellöv, M, Turner, DR, Haraldsson, C and Andersson, K 2003 Competition between iron-and carbon-based colloidal carriers for trace metals in a freshwater assessed using flow field-flow fractionation coupled to ICPMS. Geochim Cosmochim Acta 67(20): 3791–3802. DOI: 10.1016/S0016-7037(03)00087-5
Mari, X, Passow, U, Migon, C, Burd, AB and Legendre, L 2017 Transparent exopolymer particles: Effects on carbon cycling in the ocean. Prog Oceanogr 151: 13–37. DOI: 10.1016/j.pocean.2016.11.002
Martín, J, Puig, P, Masqué, P, Palanques, A and Sánchez-Gómez, A 2014a Impact of bottom trawling on deep-sea sediment properties along the flanks of a submarine canyon. PLoS One 9(8): e104536. DOI: 10.1371/journal.pone.0104536
Martín, J, Puig, P, Palanques, A and Giamportone, A 2014b Commercial bottom trawling as a driver of sediment dynamics and deep seascape evolution in the Anthropocene. Anthropocene 7: 1–15. DOI: 10.1016/j.ancene.2015.01.002
Martinez-Garcia, E, Carlsson, MS, Sanchez-Jerez, P, Sánchez-Lizaso, JL, Sanz-Lazaro, C, et al. 2015 Effect of sediment grain size and bioturbation on decomposition of organic matter from aquaculture. Biogeochemistry 125(1): 133–148. DOI: 10.1007/s10533-015-0119-y
Maskaoui, K, Hibberd, A and Zhou, JL 2007 Assessment of the interaction between aquatic colloids and pharmaceuticals facilitated by cross-flow ultrafiltration. Environ Sci Technol 41(23): 8038–8043. DOI: 10.1021/es071507d
Maxwell, P, Eklof, J, van Katwijk, MM, O’Brien, K, de la Torre-Castro, M, et al. 2016 The fundamental role of ecological feedback mechanisms in seagrass ecosystems – a review. Biol Rev 92: 1521–1538. DOI: 10.1111/brv.12294
McCave, IN 1984 Size spectra and aggregation of suspended particles in the deep ocean. Deep Sea Res A 31(4): 329–352. DOI: 10.1016/0198-0149(84)90088-8
Moksnes, P-O, Gipperth, L, Eriander, L, Laas, K, Cole, S, et al. 2016 Handbok för restaurering av ålgräs i Sverige – Vägledning. 146 (incl. appendices).
Moksnes, P-O, Gullström, M, Tryman, K and Baden, S 2008 Trophic cascades in a temperate seagrass community. Oikos 117(5): 763–777. DOI: 10.1111/j.0030-1299.2008.16521.x
Moore, KA, Wetzel, RL and Orth, RJ 1997 Seasonal pulses of turbidity and their relations to eelgrass (Zostera marina L.) survival in an estuary. J Exp Mar Bio Ecol 215(1): 115–134. DOI: 10.1016/S0022-0981(96)02774-8
Morét-Ferguson, S, Law, KL, Proskurowski, G, Murphy, EK, Peacock, EE, et al. 2010 The size, mass, and composition of plastic debris in the western North Atlantic Ocean. Mar Pollut Bull 60(10): 1873–1878. DOI: 10.1016/j.marpolbul.2010.07.020
Napper, IE, Bakir, A, Rowland, SJ and Thompson, RC 2015 Characterisation, quantity and sorptive properties of microplastics extracted from cosmetics. Mar Pollut Bull 99(1): 178–185. DOI: 10.1016/j.marpolbul.2015.07.029
Netzband, A and Adnitt, C 2009 Dredging management practices for the environment: A structured selection approach. Terra et Aqua 114: 3–8.
Newell, R, Seiderer, L and Hitchcock, D 1998 The impact of dredging works in coastal waters: A review of the sensitivity to disturbance and subsequent recovery of biological resources on the sea bed. Ann Rev Mar Sci 36: 127–178.
Newton, P and Liss, P 1990 Particles in the oceans (and other natural waters). Sci Progress Oxford 74(1): 91–114.
Nittrouer, CA and Wright, LD 1994 Transport of particles across continental shelves. Rev Geophys 32(1): 85–113. DOI: 10.1029/93RG02603
Nowack, B and Bucheli, TD 2007 Occurrence, behavior and effects of nanoparticles in the environment. Environ Pollut 150(1): 5–22. DOI: 10.1016/j.envpol.2007.06.006
Nyqvist, A, André, C, Gullström, M, Baden, SP and Åberg, P 2009 Dynamics of seagrass meadows on the Swedish Skagerrak coast. Ambio 38(2): 85–88. DOI: 10.1579/0044-7447-38.2.85
O’Neill, F and Summerbell, K 2011 The mobilisation of sediment by demersal otter trawls. Mar Pollut Bull 62(5): 1088–1097. DOI: 10.1016/j.marpolbul.2011.01.038
Orth, RJ, Moore, KA, Marion, SR, Wilcox, DJ and Parrish, DB 2012 Seed addition facilitates eelgrass recovery in a coastal bay system. Mar Ecol Prog Ser 448: 177–195. DOI: 10.3354/meps09522
Palanques, A, Martín, J, Puig, P, Guillén, J, Company, J, et al. 2006 Evidence of sediment gravity flows induced by trawling in the Palamós (Fonera) submarine canyon (northwestern Mediterranean). Deep Sea Res Part 1 Oceanogr Res Pap 53(2): 201–214. DOI: 10.1016/j.dsr.2005.10.003
Passow, U 2002 Transparent exopolymer particles (TEP) in aquatic environments. Prog Oceanogr 55(3–4): 287–333. DOI: 10.1016/S0079-6611(02)00138-6
Pedrotti, M, Peters, F, Beauvais, S, Vidal, M, Egge, J, et al. 2010 Effects of nutrients and turbulence on the production of transparent exopolymer particles: a mesocosm study. Mar Ecol Prog Ser 419: 57–69. DOI: 10.3354/meps08840
Picheral, M, Guidi, L, Stemmann, L, Karl, DM, Iddaoud, G, et al. 2010 The Underwater Vision Profiler 5: An advanced instrument for high spatial resolution studies of particle size spectra and zooplankton. Limnol Oceanogr Methods 8: 462–473. DOI: 10.4319/lom.2010.8.462
Pinkel, R, Goldin, MA, Smith, JA, Sun, OM, Aja, AA, et al. 2011 The Wirewalker: A vertically profiling instrument carrier powered by ocean waves. J Atmos Oceanic Tech 28(3): 426–435. DOI: 10.1175/2010JTECHO805.1
Ploug, H 2001 Small-scale oxygen fluxes and remineralization in sinking aggregates. Limnol Oceanogr 46(7): 1624–1631. DOI: 10.4319/lo.2001.46.7.1624
Ploug, H and Bergkvist, J 2015 Oxygen diffusion limitation and ammonium production within sinking diatom aggregates under hypoxic and anoxic conditions. Mar Chem 176: 142–149. DOI: 10.1016/j.marchem.2015.08.012
Ploug, H and Jørgensen, BB 1999 A net-jet flow system for mass transfer and microsensor studies of sinking aggregates. Mar Ecol Prog Ser 176: 279–290. DOI: 10.3354/meps176279
Ploug, H and Passow, U 2007 Direct measurement of diffusivity within diatom aggregates containing transparent exopolymer particles. Limnol Oceanogr 52(1): 1–6. DOI: 10.4319/lo.2007.52.1.0001
Puig, P, Canals, M, Company, JB, Martín, J, Amblas, D, et al. 2012 Ploughing the deep sea floor. Nature 489(7415): 286–289. DOI: 10.1038/nature11410
Puillat, I, Farcy, P, Durand, D, Karlson, B, Petihakis, G, et al. 2016 Progress in marine science supported by European joint coastal observation systems: The JERICO-RI research infrastructure. J Mar Syst 162: 1–3. DOI: 10.1016/j.jmarsys.2016.06.004
Pusceddu, A, Bianchelli, S, Martín, J, Puig, P, Palanques, A, et al. 2014 Chronic and intensive bottom trawling impairs deep-sea biodiversity and ecosystem functioning. PNAS 111(24): 8861–8866. DOI: 10.1073/pnas.1405454111
Qin, H, Zhang, S, Liu, H, Xie, S, Yang, M, et al. 2005 Photo-oxidative degradation of polypropylene/montmorillonite nanocomposites. Polymer 46(9): 3149–3156. DOI: 10.1016/j.polymer.2005.01.087
Reisser, J, Slat, B, Noble, K, du Plessis, K, Epp, M, et al. 2015 The vertical distribution of buoyant plastics at sea: an observational study in the North Atlantic Gyre. Biogeosciences 12(4): 1249–1256. DOI: 10.5194/bg-12-1249-2015
Riebesell, U 1992 Factors controlling the formation of marine snow and its sustained residence in surface waters. Limnol Oceanogr 37(1): 63–76. DOI: 10.4319/lo.1992.37.1.0063
Rocha-Santos, T and Duarte, AC 2015 A critical overview of the analytical approaches to the occurrence, the fate and the behavior of microplastics in the environment. Trends Analyt Chem 65: 47–53. DOI: 10.1016/j.trac.2014.10.011
Röhr, ME, Boström, C, Canal-Vergés, P and Holmer, M 2016 Blue carbon stocks in Baltic Sea eelgrass (Zostera marina) meadows. Biogeosciences 13(22): 6139–6153. DOI: 10.5194/bg-13-6139-2016
Rudnick, DL 2016 Ocean research enabled by underwater gliders. Annu Rev Mar Sci 8: 519–541. DOI: 10.1146/annurev-marine-122414-033913
Ruiz, J-E and Izquierdo, A 1997 A simple model for the break-up of marine aggregates by turbulent shear. Oceanol Acta 20(4): 597–605.
Sarà, G, Scilipoti, D, Mazzola, A and Modica, A 2004 Effects of fish farming waste to sedimentary and particulate organic matter in a southern Mediterranean area (Gulf of Castellammare, Sicily): a multiple stable isotope study (δ13C and δ15N). Aquaculture 234(1): 199–213. DOI: 10.1016/j.aquaculture.2003.11.020
Simpson, JH and Sharples, J 2012 Introduction to the physical and biological oceanography of shelf seas . Cambridge University Press. DOI: 10.1017/CBO9781139034098
Singh, B and Sharma, N 2008 Mechanistic implications of plastic degradation. Polym Degrad Stab 93(3): 561–584. DOI: 10.1016/j.polymdegradstab.2007.11.008
Son, M and Hsu, T-J 2011. The effects of flocculation and bed erodibility on modeling cohesive sediment resuspension. J Geophys Res 116(C03): 021. DOI: 10.1029/2010JC006352
Stoll, S and Buffle, J 1998 Computer simulation of flocculation processes: the roles of chain conformation and chain/colloid concentration ratio in the aggregate structures. J Colloid Interface Sci 205(2): 290–304. DOI: 10.1006/jcis.1998.5644
Stolpe, B and Hassellöv, M 2010 Nanofibrils and other colloidal biopolymers binding trace elements in coastal seawater: Significance for variations in element size distributions. Limnol Oceanogr 55(1): 187–202. DOI: 10.4319/lo.2010.55.1.0187
Sturve, J, Berglund, Å, Balk, L, Broeg, K, Böhmert, B, et al. 2005 Effects of dredging in Göteborg Harbor, Sweden, assessed by biomarkers in eelpout (Zoarces viviparus). Environ Toxicol Chem 24(8): 1951–1961. DOI: 10.1897/04-449R1.1
Sundborg, Å 1956 The River Klaralven: A study of fluvial processes. Geogr Ann 38(3): 238–316. DOI: 10.2307/520285
SwAM 2012 God Havsmiljö 2020. Inledande bedömning av miljötillståndet och socioekonomisk analys. Report in Swedish.
Talley, LD, Pickard, GL, Emery, WJ and Swift, JH 2011 Chapter 7 – Dynamical Processes for Descriptive Ocean Circulation. Descriptive Physical Oceanography , 187–221. 6th ed. Boston: Academic Press.
Thompson, RC, Olsen, Y, Mitchell, RP, Davis, A, Rowland, SJ, et al. 2004 Lost at sea: where is all the plastic? Science 304(5672): 838–838. DOI: 10.1126/science.1094559
Thomsen, L 2003 The Benthic Boundary Layer. In: Wefer, G, Billett, D, Hebbeln, D, Jørgensen, BB, Schlüter, M, et al. (eds.), Ocean Margin Systems , 143–155. Berlin, Heidelberg: Springer Berlin Heidelberg.
Thomsen, L and Gust, G 2000 Sediment erosion thresholds and characteristics of resuspended aggregates on the western European continental margin. Deep Sea Res Part 1 Oceanogr Res Pap 47(10): 1881–1897. DOI: 10.1016/S0967-0637(00)00003-0
Thorpe, SA 2005 The Turbulent Ocean . Cambridge, U.K.: Cambridge University Press. DOI: 10.1017/CBO9780511819933
Tjensvoll, I, Kutti, T, Fosså, JH and Bannister, R 2013 Rapid respiratory responses of the deep-water sponge Geodia barretti exposed to suspended sediments. Aquat Biol 19: 65–73. DOI: 10.3354/ab00522
Tlusty, MF, Snook, K, Pepper, VA and Anderson, MR 2000 The potential for soluble and transport loss of particulate aquaculture wastes. Aquac Res 31(10): 745–755. DOI: 10.1046/j.1365-2109.2000.00497.x
Tomassetti, P, Gennaro, P, Lattanzi, L, Mercatali, I, Persia, E, et al. 2016 Benthic community response to sediment organic enrichment by Mediterranean fish farms: Case studies. Aquaculture 450: 262–272. DOI: 10.1016/j.aquaculture.2015.07.019
Turner, JT 2015 Zooplankton fecal pellets, marine snow, phytodetritus and the ocean’s biological pump. Prog Oceanogr 130: 205–248. DOI: 10.1016/j.pocean.2014.08.005
Van Cauwenberghe, L, Vanreusel, A, Mees, J and Janssen, CR 2013 Microplastic pollution in deep-sea sediments. Environ Pollut 182: 495–499. DOI: 10.1016/j.envpol.2013.08.013
van der Heide, T, van Nes, EH, Geerling, GW, Smolders, AJ, Bouma, TJ, et al. 2007 Positive feedbacks in seagrass ecosystems: Implications for success in conservation and restoration. Ecosystems 10(8): 1311–1322. DOI: 10.1007/s10021-007-9099-7
Verdugo, P 2012 Marine microgels. Annu Rev Mar Sci 4: 375–400. DOI: 10.1146/annurev-marine-120709-142759
Volk, T and Hoffert, MI 1985 Ocean carbon pumps: Analysis of relative strengths and efficiencies in ocean-driven atmospheric CO2 changes. In: Sundquist, ET and Broecker, WS (eds.), The carbon cycle and atmospheric CO: Natural variations archean to present , 99–110. Washington, D. C.: American Geophysical Union.
Volkenborn, N, Robertson, DM and Reise, K 2008 Sediment destabilizing and stabilizing bio-engineers on tidal flats: cascading effects of experimental exclusion. Helgol Mar Res 63(1): 27–35. DOI: 10.1007/s10152-008-0140-9
Volkman, JK and Tanoue, E 2002 Chemical and biological studies of particulate organic matter in the ocean. J Oceanogr Soc Japan 58(2): 265–279. DOI: 10.1023/A:1015809708632
Wagner, M, Scherer, C, Alvarez-Muñoz, D, Brennholt, N, Bourrain, X, et al. 2014 Microplastics in freshwater ecosystems: what we know and what we need to know. Environ Sci Eur 26(1): 12. DOI: 10.1186/s12302-014-0012-7
Wang, S-M, Chang, J-R and Tsiang, RC-C 1996 Infrared studies of thermal oxidative degradation of polystyrene-block polybutadiene-block-polystyrene thermoplastic elastomers. Polym Degrad Stab 52(1): 51–57. DOI: 10.1016/0141-3910(95)00226-X
Ward, LG, Kemp, WM and Boynton, WR 1984 The influence of waves and seagrass communities on suspended particulates in an estuarine embayment. Mar Geo 59(1–4): 85–103. DOI: 10.1016/0025-3227(84)90089-6
Watts, AJ, Urbina, MA, Corr, S, Lewis, C and Galloway, TS 2015 Ingestion of plastic microfibers by the crab Carcinus maenas and its effect on food consumption and energy balance. Environ Sci Technol 49(24): 14597–14604. DOI: 10.1021/acs.est.5b04026
Weinstein, JE, Crocker, BK and Gray, AD 2016 From macroplastic to microplastic: Degradation of high-density polyethylene, polypropylene, and polystyrene in a salt marsh habitat. Environ Toxicol Chem 35(7): 1632–1640. DOI: 10.1002/etc.3432
Wikström, A, Linders, T, Sköld, M, Nilsson, P and Almén, J 2016 Bottentrålning och resuspension av sediment. Technical report, Länsstyrelsen i Västra Götalands län, Naturvårdsenheten. 2016:36. In Swedish.
Wright, SL, Thompson, RC and Galloway, TS 2013 The physical impacts of microplastics on marine organisms: A review. Environ Pollut 178: 483–492. DOI: 10.1016/j.envpol.2013.02.031
Zhang, J, Gilbert, D, Gooday, A, Levin, L, Naqvi, S, et al. 2010 Natural and human-induced hypoxia and consequences for coastal areas: synthesis and future development. Biogeosciences 7: 1443–1467. DOI: 10.5194/bg-7-1443-2010