This paper reviews the provisions and efforts to implement the 1946 International Convention for the Regulation of Whaling (ICRW) and the 1980 Convention on the Conservation of Antarctic Marine Living Resources (CCAMLR). It illustrates progress and continuing challenges to stopping the overexploitation of living resources in high seas areas beyond national jurisdictions. Progress includes recognition that living organisms interact with each other and the environment in complex ways and that single-species management to attain maximum sustainable yield (MSY) fails to account for these interactions. Continuing challenges include data limitations that allow differing views concerning the adequacy and interpretation of the available data, and decision-makingthat allows a minority of the decision-makers to block adoption of regulatory measures that the majority believe necessary to meet the intent and provisions of the regulatory agreements. The provisions and continuing challenges to meeting the objectives of these two conventions should be considered in the formulation of future international high seas regulatory agreements such as the regime to govern fisheries in the central Arctic Ocean as envisioned in the 16 year ban on commercial fishing there agreed in October 2018 by Canada, Denmark (for Greenland), Iceland, Russia, Norway, the United States, the European Union, Japan, China, and South Korea.
The following titles are freely-available, or include a link to a preprint or postprint.
Skin marks occur frequently in many cetacean species across the globe revealing a broad spectrum of causes, including social interactions, infectious diseases and injuries produced by anthropogenic factors. The current study used photo-id data from 2005–2014 to estimate the skin mark pattern on resident bottlenose dolphins (Tursiops truncatus) from the Aeolian Archipelago (Italy). Thirteen skin mark types were identified and their origin, prevalence and permanence time were examined. The pattern of skin marks was assessed for the abundance, richness, distribution and severity in six body regions and compared among age classes, sex and degree of dolphins’ interaction with trammel nets (DIN). Our results showed higher prevalence, abundance, richness and distribution of skin marks in adults than in the younger age classes, with the exception of black marks and white ring lesions. The prevalence and abundance of skin marks were higher in males than females, with the exception of scratches and white patches. Moreover, gunshot wounds, mutilations and irregular dorsal fin edges were found only on adult males. Since males showed higher DIN than females and, in dolphins with higher DIN, skin marks were more abundant and frequently distributed in different body regions, the skin mark pattern in regard to DIN seems to be sex-related. The more severe marks were observed on adults, males and dolphins with higher DIN, namely skin disorder, tooth rake marks, small shallow indentations, deep indentations and mutilations. On the contrary, the severity of scratches, white patches and dark ring lesions was higher in females than males, but not significantly related to DIN and age of the individuals. Our results showed that photo-id data provide an efficient and cost-effective approach to document the occurrence of skin marks in free-ranging bottlenose dolphin populations, a critical step toward understanding the cause and supporting the conservation strategies.
The Juan Fernández Ridge (JFRE) is a vulnerable marine ecosystem (VME) located off the coast of central Chile formed by the Juan Fernández Archipelago and a group of seamounts. This ecosystem has unique biological and oceanographic features, characterized by: small geographical units, high degree of endemism with a high degree of connectivity within the system. Two fleets have historically operated in this system: a long term coastal artisanal fishery associated with the Islands, focused mainly on lobster, and a mainland based industrial demersal finfish fishery operating on the seamounts which is currently considered overexploited. The management of these fisheries has been based on a classical single-species approach to determine output controls (industrial fleet) and a mixed management system with formal and informal components (artisanal fleet). There has been growing interest in increasing the exploitation of fisheries, and modernization of the fishing fleet already operating in the JFRE. Under this scenario of increased levels of fishing exploitation and the high level of interrelation of species it might be necessary to understand the impact of these fisheries from a holistic perspective based on a ecosystem-based modeling approach. To address these challenges we developed an Atlantis end-to-end model was configured for this ecosystem. The implemented model has a high degree of skill in representing the observed trends and fluctuations of the JFRE. The model shows that the industrial fishing has a localized impact and the artisanal fisheries have a relatively low impact on the ecosystem, mainly via the lobster fishery. The model indicates that the depletion of large sized lobster has leads to an increase in the population of sea urchins. Although this increase is not sufficient, as yet, to cause substantial flow-on effects to other groups, caution is advised in case extra pressure leads the ecosystem towards a regime shift.
Reef sharks are vulnerable predators experiencing severe population declines mainly due to overexploitation. However, beyond direct exploitation, human activities can produce indirect or sub-lethal effects such as behavioral alterations. Such alterations are well known for terrestrial fauna but poorly documented for marine species. Using an extensive sampling of 367 stereo baited underwater videos systems, we show modifications in grey reef shark (Carcharhinus amblyrhynchos) occurrence and feeding behavior along a marked gradient of isolation from humans across the New Caledonian archipelago (South-Western Pacific). The probability of occurrence decreased by 68.9% between wilderness areas (more than 25 hours travel time from the capital city) and impacted areas while the few individuals occurring in impacted areas exhibited cautious behavior. We also show that only large no-entry reserves (above 150 km²) can protect the behavior of grey reef sharks found in the wilderness. Influencing the fitness, human linked behavioral alterations should be taken into account for management strategies to ensure the persistence of populations.
The aesthetic appreciation of natural places is one of the most fundamental ways in which people relate to their environment. It provides wellbeing, an opportunity for recreation and reflection, a sense of place, and cultural enrichment. It also motivates people to take care of natural places and to conserve them for current and future appreciation. Aesthetically valuable places also support significant economic activity. However, there is little guidance available to assist environmental managers and policy-makers to consider and integrate aesthetic values into decision-making processes. In this study, we present an approach for developing robust and practical indicators of aesthetic value to enable environmental managers to consider, assess and report on aesthetic condition and trend. We demonstrate its utility using the case of the Great Barrier Reef, a region currently undergoing significant social, economic and environmental change and an area formally protected, in part, for its aesthetic values. A qualitative scoping study with 30 key informants identified over 180 potential qualities contributing to reef aesthetics. We tested five for their utility in capturing key aspects of the coral reef aesthetic: (i) coral cover, (ii) coral pattern, (iii) coral topography, (iv) fish abundance, and (v) visibility. We asked 1,417 online Australians to aesthetically rate 50 out of 181 underwater coral reef images that varied in relation to these five attributes. Coral topography, fish abundance, and visibility were significantly correlated with aesthetic ratings, whilst coral cover and coral pattern were not. We also tested for demographic patterns in aesthetic ratings. Our pilot study has demonstrated that readily measurable characteristics of coral reefs can provide useful indicators of aesthetic quality, opening up opportunities for coral reef managers and policymakers to assess and track changes in aesthetics in ways that are relevant to the public. There is considerable scope to further advance capacity for monitoring and managing aesthetic values of coral reefs through additional research that resolves nuances in the meanings associated with aesthetics in coral reef settings.
As documented by the numerous publications that have appeared in recent years, plastic pollution of the environment and the effects on the respective ecosystems are currently one of the most intensely discussed issues in environmental science and in society at large. Of special concern are the effects of micro- and nano-sized plastics. A key issue in understanding the fate and potential effects of micro- and nano-sized plastics is their dynamic nature, as the size, shape, and charge of the particles change over time. Moreover, due to various biological processes, such as the aggregation of organic material and/or bacteria (“biofouling”), the density of plastic particles that settle in the sediments of aquatic ecosystems may be several orders of magnitudes higher than that in the surrounding waters. Consequently, the risk posed by plastic pollution to benthic fauna is considerably high. Nonetheless, the vast majority of studies examining the effects of microplastics have focused on pelagic organisms so far. We therefore conducted a comprehensive literature review to examine the impact of micro- and nano-sized plastics on benthic invertebrates, including the physical and chemical effects of leaching and the interactions of plastic particles with contaminants. Overall, 330 papers were reviewed for their fulfillment of different criteria (e.g., test species, plastic material, particle shape, particle size, exposure concentration, exposure route, assay type, assay duration), with 49 publications finally included in our survey. A comprehensive gap-analysis on the effects of plastic particles on benthic invertebrates revealed a wide variety of effects triggered by micro- and/or nano-sized plastics but also distinct differences regarding the plastic materials tested, the size fractions applied, the shape of the respective particles, and the exposure routes tested. Our review concludes with a discussion of the important research gaps concerning freshwater ecosystems and recommendations for future areas of research.
Mangrove forests provide valuable coastal protection from erosion, habitat for terrestrial and marine species, nursery grounds for commercial fisheries and are economically important for tourism. Galapagos’ mangroves usually grow directly on solid lava and fragmented rocky shores, thereby stabilizing the sediment and facilitating colonisation by other plants and many animals. However, until very recently, only inaccurate data described mangrove coverage and its distribution. We mapped mangroves using freely available Google Earth Very High Resolution images based on on-screen classification and compared this method to three semi-automatic classification algorithms. We also analysed mangrove change for the period 2004–2014. We obtained an area of 3657.1 ha of fringing mangrove that covers 35% of the coastline. Eighty percent of mangrove cover is found in Isabela island, and 90% in the western and central south-eastern bioregions. The overall accuracy of mangrove classification was 99.1% with a Kappa coefficient of 0.97 when validated with field data. On-screen digitization was significantly more accurate than other tested methods. From the semi-automated methods, Maximum Likelihood Classification with prior land-sea segmentation yielded the best results. During the 2004–2014 period, mangrove coverage increased 24% mainly by expansion of existing mangroves patches as opposed to generation of new patches. We estimate that mangrove cover and growth are inversely proportional to the geological age of the islands. However, many other factors like nutrients, currents or wave exposure protection might explain this pattern. The precise localization of mangrove cover across the Galapagos islands now enables documenting whether it is changing over time.
The recent decline of the Arctic sea ice cover leads to an increasing number of vessels navigating through the Arctic shipping routes. Ballast water, essential for the vessel's safety during voyages and cargo transfers, however, is also considered one of the main vectors for transport and introduction of non-indigenous species. The aim of this paper is to investigate potential effects of the ballast water discharged in the main Arctic shipping routes on the local environment. For that a passive tracer was implemented in a fine resolution coupled ocean-sea ice model covering the entire Arctic and northern North Atlantic, to simulate the spread of the ballast water discharged based on release points along real ship positions from 2013. The model results showed that spring and summer were the seasons with the highest tendency for accumulation of ballast water tracer on the surface layers south of NovayaZemlyaand south of Spitsbergen, not only due to a higher number of vessels navigating in the area but also due to strong stratification. During winter and autumn, the tracer was mixed with and into deeper layers due to vertical convection. The simulated ballast water accumulation during spring and summer indicated that organisms, that survived the voyage in the ballast tanks, could establish a stable or growing population and eventually become invasive.
Deep-sea mining (DSM) may become a significant stressor on the marine environment. The DSM industry should demonstrate transparently its commitment to preventing serious harm to the environment by complying with legal requirements, using environmental good practice, and minimizing environmental impacts. Here existing environmental management approaches relevant to DSM that can be used to improve performance are identified and detailed. DSM is still predominantly in the planning stage and will face some unique challenges but there is considerable environmental management experience in existing related industries. International good practice has been suggested for DSM by bodies such as the Pacific Community and the International Marine Minerals Society. The inherent uncertainty in DSM presents challenges, but it can be addressed by collection of environmental information, area-based/spatial management, the precautionary approach and adaptive management. Tools exist for regional and strategic management, which have already begun to be introduced by the International Seabed Authority, for example in the Clarion-Clipperton Zone. Project specific environmental management, through environmental impact assessment, baseline assessment, monitoring, mitigation and environmental management planning, will be critical to identify and reduce potential impacts. In addition, extractive companies’ internal management may be optimised to improve performance by emphasising sustainability at a high level in the company, improving transparency and reporting and introducing environmental management systems. The DSM industry and its regulators have the potential to select and optimize recognised and documented effective practices and adapt them, greatly improving the environmental performance of this new industry.
Fisheries management interventions that protect certain species by redistributing fishing effort may generate unintended consequences for other species. In the California drift gillnet fishery for swordfish and sharks, a large spatial closure was implemented in 2001 to protect endangered leatherback turtles, which limited fishing effort to the Southern California Bight. Leatherback bycatch has since decreased, but the effects on other species have not been comprehensively examined. Here, we explore the effects of this closure on the community catch composition in the fishery and find that other protected species may have benefited, while catch per unit effort of major target species increased or was not significantly affected over the long term. However, a time-series analysis reveals that changes in catch trends across twenty species began at least five years before the closure was implemented, suggesting that previous regulatory measures or other drivers may also contribute to these trends. These results highlight the importance of comprehensive approaches that include the historical context when evaluating management outcomes.
We have evaluated the cultivation potential of sugar kelp (Saccharina latissima) as a function of latitude and position (near- and offshore) along the Norwegian coast using a coupled 3D hydrodynamic-biogeochemical-kelp model system (SINMOD) run for four growth seasons (2012–2016). The results are spatially explicit and may be used to compare the suitability of different regions for kelp cultivation, both inshore and offshore.The simulation results were compared with growth data from kelp cultivation experiments and in situ observations on coverage of naturally growing kelp. The model demonstrated a higher production potential offshore than in inshore regions, which is mainly due to the limitations in nutrient availability caused by the stratification found along the coast. However, suitable locations for kelp cultivation were also identified in areas with high vertical mixing close to the shore. The results indicate a latitudinal effect on the timing of the optimal period of growth, with the prime growth period being up to 2 months earlier in the south (58 °N) than in the north (71 °N). Although the maximum cultivation potential was similar in the six marine ecoregions in Norway (150–200 tons per hectare per year), the deployment time of the cultures seems to matter significantly in the south, but less so in the north. The results are discussed, focusing on their potential significance for optimized cultivation and to support decision making toward sustainable management.
We modelled and assessed the past, present and predicted future eutrophication status of the Baltic Sea. The assessment covers a 350-year period from 1850 to 2200 and is based on: (1) modelled concentrations of dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorous (DIP), chlorophyll-a, Secchi depth, and oxygen under four different of nutrient input scenarios and (2) the application of a multi-metric indicator-based tool for assessment of eutrophication status: HEAT 3.0. This tool was previously applied using historical observations to determine eutrophication status from 1901 to 2012. Here we apply HEAT 3.0 using results of a biogeochemical model to reveal significant changes in eutrophication status from 1850 to 2200. Under two scenarios where Baltic Sea Action Plan (BSAP) nutrient reduction targets are met, we expect future good status will be achieved in most Baltic Sea basins. Under two scenarios where nutrient loads remain at 1997–2003 levels or increase, good status will not be achieved. The change from a healthy state without eutrophication problems in the open waters took place in the late 1950s and early 1960s. Following introduction of the first nutrient abatement measures, recovery began in some basins in the late 1990s, whilst in others it commenced in the beginning of the 21st century. Based on model results, we expect that the first basin to achieve a status without eutrophication will be Arkona, between 2030 and 2040. By 2060–2070, a status without eutrophication is anticipated for the Kattegat, Bornholm Basin and Gulf of Finland, followed by the Danish straits around 2090. For the Baltic Proper and Bothnian Sea, a good status with regard to eutrophication is not expected before 2200. Further, we conclude that two basins are not likely to meet the targets agreed upon and to attain a status unaffected by eutrophication, i.e., the Gulf of Riga and Bothnian Bay. These results, especially the prediction that some basins will not achieve a good status, can be used in support of continuous development and implementation of the regional ecosystem-based nutrient management strategy, the HELCOM Baltic Sea Action Plan.
Climate change, represented by ever-rising ocean temperatures, is a mounting threat to the marine ecosystem and its services. This is most evident in the longitudinal and depth-related migrations of the ectothermic species. Although the impacts of climate change on the marine ecosystem of the Arabian Gulf are expected to be exacerbated—owing to its semi-enclosed basin that limits species range shift, extreme environmental conditions, overfishing, and pollution—very few studies have been carried out to evaluate such impacts. Here, we conduct a systematic review of literature over the period 1950–2018 to assess the status of knowledge about climate change impacts on the Arabian Gulf's marine ecosystem and fisheries resources. We found that this region suffers a significant research gap in this critical subject, with only a handful of studies that explicitly addresses the effects of climate change. Our finding raises an urgent need for initiating long-term monitoring programs, along with establishing effective transboundary institutions to advance the current knowledge in climate change.
Identifying the species that are at risk of local extinction in highly diverse ecosystems is a big challenge for conservation science. Assessments of species status are costly and difficult to implement in developing countries with diverse ecosystems due to a lack of species-specific surveys, species-specific data, and other resources. Numerous techniques are devised to determine the threat status of species based on the availability of data and budgetary limits. On this basis, we developed a framework that compared occurrence data of historically exploited reef species in Kenya from existing disparate data sources. Occurrence data from archaeological remains (750-1500CE) was compared with occurrence data of these species catch assessments, and underwater surveys (1991-2014CE). This comparison indicated that only 67 species were exploited over a 750 year period, 750-1500CE, whereas 185 species were landed between 1995 and 2014CE. The first step of our framework identified 23 reef species as threatened with local extinction. The second step of the framework further evaluated the possibility of local extinction with Bayesian extinction analyses using occurrence data from naturalists’ species list with the existing occurrence data sources. The Bayesian extinction analysis reduced the number of reef species threatened with local extinction from 23 to 15. We compared our findings with three methods used for assessing extinction risk. Commonly used extinction risk methods varied in their ability to identify reef species that we identified as threatened with local extinction by our comparative and Bayesian method. For example, 12 of the 15 threatened species that we identified using our framework were listed as either least concern, unevaluated, or data deficient in the International Union for the Conservation of Nature red list. Piscivores and macro-invertivores were the only functional groups found to be locally extinct. Comparing occurrence data from disparate sources revealed a large number of historically exploited reef species that are possibly locally extinct. Our framework addressed biases such as uncertainty in priors, sightings and survey effort, when estimating the probability of local extinction. Our inexpensive method showed the value and potential for disparate data to fill knowledge gaps that exist in species extinction assessments.
Determining what abiotic and biotic factors affect the diversity and abundance of species through time and space is a basic goal of ecology and an integral step in predicting current and future distributions. Given the pervasive effect of humans worldwide, including anthropogenic factors when quantifying community dynamics is needed to understand discrete and emergent effects of humans on marine ecosystems, especially systems with economically important species. However, there are limited studies that combine a large-scale ecological survey with multiple natural and anthropogenic factors to determine the drivers of community dynamics of temperate reef systems. We combined data from a 24-year fish survey on temperate reefs along the Southeast United States coast with information on recreational and commercial fisheries landings, surface and bottom temperature, habitat characteristics, and climate indices to determine what factors may alter the community structure of fishes within this large marine ecosystem. We found that both abundance and richness of temperate reef fishes declined from 1990 to 2013. Climate indices and local temperature explained the greatest variation, and recreational fishing explained slightly more variation compared to commercial fishing in the temperate reef fish community over a multi-decadal scale. When including habitat characteristics in a 3 year analysis, depth, and local temperature explained the greatest variation in fish assemblage, while the influence of habitat was comparatively minimal. Finally, the interaction between predictor variables and fish traits indicated that bigger and longer-lived fishes were positively correlated with depth and winter temperature. Our findings suggest that lesser-studied anthropogenic impacts, such as recreational fishing, may influence communities throughout large ecosystems as much as other well-studied impacts such as climate change and commercial fishing. In addition, climate indices should be considered when assessing changes, natural or anthropogenic, to fish communities.
The European Union (EU) instituted a carding system via its European Commission Regulation (EC) No. 1005/2008 with the goal of incentivizing fish and fish products (fish) exporting countries to the Union to take action to reduce IUU fishing in their waters. This regulation stipulates that the EU will issue warnings, known as a “yellow card,” to countries that perform poorly in the effort to end IUU fishing in their waters. Failure to curb IUU fishing will result in a ban in the export of fish to the EU via the issuance of a red card. Here, I ask the following questions: what is the economic risk of being red carded by the EU? Is the economic risk big enough to significantly reduce IUU fishing in a targeted country’s waters? Would the risk be broad enough to result in a significant reduction in IUU fishing globally? What if the two other leading fish importing countries, i.e., the United States and Japan, also institute a similar carding system as the EU? To address these questions, I develop and compute an economic risk index for the carding system. This study suggests that the impact of an EU only IUU carding system could be significant for some targeted countries but its effect globally, with respect to reducing IUU fishing, would be minimal. However, I find that the economic risk to fish exporting countries would increase significantly if the United States and Japan also instituted similar carding systems, which would in turn help to reduce IUU fishing worldwide. This contribution shows that an IUU carding system could contribute significantly to the elimination of IUU fishing provided a critical mass of top fish importing countries participate in such a system.
Trait-based approaches to investigate (short- and long-term) phytoplankton dynamics and community assembly have become increasingly popular in freshwater and marine science. Although the nature of the pelagic habitat and the main phytoplankton taxa and ecology are relatively similar in both marine and freshwater systems, the lines of research have evolved, at least in part, separately. We compare and contrast the approaches adopted in marine and freshwater ecosystems with respect to phytoplankton functional traits. We note differences in study goals relating to functional trait use that assess community assembly and those that relate to ecosystem processes and biogeochemical cycling that affect the type of characteristics assigned as traits to phytoplankton taxa. Specific phytoplankton traits relevant for ecological function are examined in relation to herbivory, amplitude of environmental change and spatial and temporal scales of study. Major differences are identified, including the shorter time scale for regular environmental change in freshwater ecosystems compared to that in the open oceans as well as the type of sampling done by researchers based on site-accessibility. Overall, we encourage researchers to better motivate why they apply trait-based analyses to their studies and to make use of process-driven approaches, which are more common in marine studies. We further propose fully comparative trait studies conducted along the habitat gradient spanning freshwater to brackish to marine systems, or along geographic gradients. Such studies will benefit from the combined strength of both fields.
Exposure to oil from the Deepwater Horizon spill may have lasting impacts on preservation of historic shipwrecks in the Gulf of Mexico. Submerged steel structures, including shipwrecks, serve as artificial reefs and become hotspots of biodiversity in the deep sea. Marine biofilms on submerged structures support settlement of micro- and macro-biota and may enhance and protect against corrosion. Disruptions in the local environment, including oil spills, may impact the role that biofilms play in reef preservation. To determine how the Deepwater Horizon spill potentially impacted shipwreck biofilms and the functional roles of the biofilm microbiome, experiments containing carbon steels disks (CSDs) were placed at five historic shipwreck sites located within, and external to the benthic footprint of the Deepwater Horizon spill. The CSDs were incubated for 16 weeks to enable colonization by biofilm-forming microorganisms and to provide time for in situ corrosion to occur. Biofilms from the CSDs, as well as sediment and water microbiomes, were collected and analyzed by 16S rRNA amplicon gene sequencing to describe community composition and determine the source of taxa colonizing biofilms. Biofilm metagenomes were sequenced to compare differential gene abundances at spill-impacted and reference sites. Biofilms were dominated by Zeta-, Alpha-, Epsilon-, and Gamma-proteobacteria. Sequences affiliated with the Mariprofundus and Sulfurimonas genera were prolific, and Roseobacter, and Colwellia genera were also abundant. Analysis of 16S rRNA sequences from sediment, water, and biofilms revealed sediment to be the main known source of taxa to biofilms at impacted sites. Differential gene abundance analysis revealed the two-component response regulator CreC, a gene involved in environmental stress response, to be elevated at reference sites compared to impacted sites within the spill plume fallout area on the seafloor. Genes for chemotaxis, motility, and alcohol dehydrogenases were differentially abundant at reference vs. impacted sites. Metal loss on CSDs was elevated at sites within the spill fallout plume. Time series images reveal that metal loss at a heavily impacted site, the German Submarine U-166, has accelerated since the spill in 2010. This study provides evidence that spill residues on the seafloor may impact biofilm communities and the preservation of historic steel shipwrecks.
Reaching protected area (PA) coverage goals is challenged by a lack of sufficient financial resources. This funding gap is particularly pervasive for marine protected areas (MPAs). It has been suggested that marine conservationists examine examples from terrestrial protected areas (TPAs) for potential solutions to better fund MPAs. However, the funding needs for MPAs and TPAs have not been directly compared, and there is risk of management failures if any such differences are not properly considered when designing MPA financial strategies. We perform an in-depth literature review to investigate differences in distribution of costs incurred by MPAs and TPAs across three primary categories; establishment, operational, and opportunity costs. We use our findings to conduct a snapshot quantitative comparison, which we complement with theoretical support to provide preliminary insight into differences between MPA and TPA costs, and how these may influence financial strategies most appropriate for each type of PA. Our research suggests that TPA costs, and thereby funding requirements, are greater for the time period leading up to and including the implementation phase, whereas MPAs have higher financial requirements for meeting long-term annual operational costs. This may be primarily due to the prevalence of private property rights for terrestrial regions, which are less frequently in place for ocean areas, as well as logistical requirements for enforcement and monitoring in a marine environment. To cement these suggestions in greater analytical certainty, we call for more thorough and standardized PA cost reporting at all stages, especially for MPAs and PAs in developing countries. The quantity and quality of such data presently limits research in PA sustainable finance, and will need to be remedied to advance the field in future years.
Despite growing plastic discharge into the environment, researchers have struggled to detect expected increases of marine plastic debris in sea surfaces, sparking discussions about “missing plastics” and final sinks, which are hypothesized to be coastal and deep-sea sediments. While it holds true that the highest concentrations of plastic particles are found in these locations (103-104 particles m-3 in sediments vs. 0.1-1 particles m-3in the water column), our meta-analysis also highlights that in open oceans, microplastic polymer types segregated in the water column according to their density. Lower density polymers, such as polypropylene and polyethylene, dominated sea surface samples (25% and 42%, respectively) but decreased in abundance through the water column (3% and 2% in the deep-sea, respectively), whereas only denser polymers (i.e.polyesters and acrylics) were enriched with depth (5% in surface seawater vs. 77 % in deep-sea locations). Our meta-analysis demonstrates that some of the most abundant and recalcitrant manufactured plastics are more persistent in the sea surface than previously anticipated and that further research is required to determine the ultimate fate of these polymers as current knowledge does not support the deep sea as the final sink for all polymer types.