Sea Ecosystem Research Articles

Characterization of microplastics in digestive tract of commercial fish species from the Oman Sea

Microplastics (MPs) content of the digestive tract of two commercial fish from the northern shores of the Oman Sea were investigated. The MPs were characterized by optical microscopy, fluorescent microscopy, and SEM-EDX for their number, shape, size, and color. Polymer composition was analyzes using micro-Raman spectroscopy (RMS). MPs were recovered in all fish samples (100 %), with an average of 43.16 ± 8.23 items/individual in Otolithes ruber, and 29.9 ± 2.73 items/individual in Acanthopagrus latus. The predominant shape of MPs in both fishes was fiber (46 %) with black, transparent, and white colors. The majority of MPs were <1000 μm (75 %), and half of the MPs were smaller than 300 μm in size. Their synthetic nature was confirmed by Nile Red staining and determination of the elemental composition of selected items. Polypropylene (PP) and polyethylene (PE) were the dominant plastic polymers in the fish digestive tracts. This study reveals abundance distribution of MPs in digestive tract of commercial marine fish. High number of ingested MPs can alarm the accumulation of MPs in the northern of Oman Sea ecosystem with anthropogenic activities and raises issues in public health.

Joint research in the Baltic Sea by the Atlantic Branch of the VNIRO and the Atlantic Branch of the Shirshov Institute of Oceanology of the RAS

The aim: complex study of the Baltic Sea ecosystem, including the habitat conditions of aquatic biological resources based on the results of joint research by AtlantNIRO and the P.P. Shirshov Institute of Oceanology RAS (Atlantic Branch). Methods used: analysis of long-term data of joint expeditionary research in the open part and coastal zone of the Baltic Sea.Results: owing to the interaction of AtlantNIRO with AB IO RAS in 2018–2022, the continuity of long-term observations has been preserved and the volume of scientific information necessary for assessing the state of the habitat of aquatic biological resources in the Russian sectors of the Baltic Sea has been increased. Modern data on eutrophication and pollution, on distribution of phytoplankton, zooplankton, benthos, as well as the early ontogenetic stages of the main commercial fish have been obtained. The spatial distribution of plankton and benthic communities, including areas favorable for spawning and feeding of fish, has been detailed. A rather high contamination of bottom sediments with radionuclides in certain areas of the Baltic Sea, primarily in the Gulf of Finland, has been found.Practical significance: the implementation of the areas provided by the Agreement between Rosrybolovstvo and RAS, and above all, the participation of AtlantNIRO scientific groups in expeditions in the Baltic Sea in 2018–2022, was a significant addition to the annual research and state monitoring of aquatic biological resources and their habitats conducted by VNIRO in the Baltic Sea.

Exploring fishing impacts on the structure and functioning of the Yellow Sea ecosystem using an individual-based modeling approach

The Yellow Sea is a marginal sea in the Northwestern Pacific where the fishery resources have been overfished and the community structure has greatly changed over the past six decades. Ecosystem modeling approaches are valuable tools to uncover potential mechanisms behind the ecosystem changes. Here, we developed ‘OSMOSE-YS’, an individual-based multi-species OSMOSE model that includes important commercial pelagic and demersal fish and invertebrates in the Yellow Sea. Simulations were carried out under three fishing scenarios to investigate how different levels of fishing pressure may have impacted the Yellow Sea ecosystem. Results indicate that the biomass of demersal fish continued to decline during 1970–2014, while the biomass of pelagic fish and invertebrates fluctuated periodically. Long-term fishing pressure has led to the reduction of total biomass, body sizes, and longevity of the modelled species. Under low-fishing condition, the ecosystem biomass is restored and the proportion of elder and larger individuals increases. On the contrary, high-fishing condition further decreases the proportion of high-trophic-level species. OSMOSE-YS serves as a baseline model to investigate ecosystem responses to different fishing strategies, in support of ecosystem-based fisheries management in the Yellow Sea.

SCAIRM: A spatial cumulative assessment of impact risk for management

This study introduces SCAIRM, a Spatially explicit Cumulative Impact Assessment method specifically developed for application to guide Ecosystem-Based Management. The method incorporates relevant human activities, their pressures and their impacts on ecosystem components. Cumulative assessment methods usually apply categorical semi-quantitative scores based on expert judgement in order to be comprehensive, or alternatively, only cover a small subset of interactions using more sophisticated quantitative information. The SCAIRM approach aims to capture 'the best of both worlds': it builds on categorical risk-based approaches, but modified such that their outcome, i.e. Impact Risk from cumulative pressures, is conceptually identical to the outcome from the quantitative approaches. This allows harmonization of qualitative and quantitative approaches into a single method, that has the advantage that it is comprehensive and can be used in data-poor situations while allowing the use of available quantitative information in more data-rich situations. It results in an improved capacity to inform policy or provide operational-centric guidance required for the essentially sectoral management. The method was applied to the North Sea ecosystem as an illustrative example of the typical output of most Cumulative Impact Assessments: indicating the ecosystem components mostly under threat, and the main activities and their pressures responsible for it. To that end, SCAIRM provides an assessment outcome expressed in ecologically meaningful terms, i.e. potential change in state compared to an undisturbed situation, implying all receptors except the pelagic water column to be potentially “endangered” (more than 50% decrease) and requiring conservation efforts. A decision tree was developed to guide management towards an increased effectiveness showing that much of the Impact Risk (41%) is caused by few well-known stressors (7%) that are difficult to mitigate but a remaining 29% of the Impact Risk from many often lesser-known stressors (59%) where management is likely to perform better.

Metagenomic analysis as a tool for studying and monitoring biological diversity in the Arctic Seas

The monitoring of the state of the ecosystems of the Arctic seas is both an urgent practical task in the face of ever-increasing anthropogenic pressure on fragile Arctic ecosystems, and a fundamental scientific task, because for its implementation it is necessary to solve a number of important scientific issues. A reliable assessment of the state of biological diversity in marine ecosystems is associated with the need to have accurate data on the species composition of benthic and plankton communities. The development of a method for assessing the biological diversity of marine communities by metagenomic analysis opens up a promising way to solve this problem.

Retrospective analysis of the pelagic ecosystem of the Western Mediterranean Sea: Drivers, changes and effects

In the Western Mediterranean Sea, forage fishes have changed in abundance, body condition, growth, reproduction, and distribution in the last decades. Different hypotheses have been proposed to explain these changes, including increase in fishing mortality; changes in environmental conditions affecting species fitness, and planktonic productivity and quality; recovery of top predators; and increase in competitors. We investigated the main drivers and changes of the pelagic ecosystem and their effects using an ecosystem-based modelling approach. Specifically, we (1) quantified the potential historical contribution of various drivers of change, (2) investigated changes in temporal trends and spatial distributions of main ecosystem components, and (3) identified ecological consequences of these changes in top predator and competitors, their fisheries and ecosystem traits during 2000–2020. We updated an established Ecopath food-web model representing the Spanish and French Mediterranean sub-areas (GSA06 and GSA07) in 2000 with recent available data. We applied the temporal dynamic Ecosim module, and tested historical time series of fishing effort, fishing mortality and environmental factors as potential drivers. Observed biomass and landings of key species were used to validate model projections. A spatial-temporal Ecospace model was developed to project species distribution changes. Results showed historical biomass and catch changes driven by a combination of high fishing pressure and environmental change (i.e. increase in temperature and salinity, and decline in primary productivity). Small pelagic fish showed significant temporal changes and predicted shifts in their distributions, following a latitudinal gradient. Predators and competitors showed changes as well, displaying heterogeneous spatial patterns, while fisheries landings declined. Overall, results matched observations (e.g., decline of sardine, fluctuations of anchovy and increases in bluefin tuna) and illustrated the need to complement traditional assessments with integrative frameworks to move towards an ecosystem-based approach in the Mediterranean. They also highlighted important knowledge gaps to guide future research in the region.

Climate change impact and anthropogenic activity on the hydrometeorological regime and the ecosystem of the Baltic Sea

Climate change impact and anthropogenic activity on the hydrometeorological regime and the ecosystem of the Baltic Sea

Abundance and biomass of copepods and cladocerans in Atlantic and Arctic domains of the Barents Sea ecosystem

Abstract Zooplankton in the Barents Sea have been monitored annually with a standard procedure with determination of size-fractioned biomass since the mid-1980s. Biomass of copepods and cladocerans was estimated based on measured abundance and individual weights taken from literature. Calanus species were dominant, making up ~85% of the estimated biomass of copepods. The second most important taxon was Oithona spp. (~0.5 g dry weight (dw) m−2, ~10%), followed by Metridia spp. (~0.15 g dw m−2, 2–3%) and Pseudocalanus spp. (0.10–0.15 g dw m−2, 1–5%). Estimated biomass of cladoceran taxa (Evadne and Podon) was low (0.01 g dw m−2). Calanus spp. contributed most of the biomass of the medium size fraction (1–2 mm), whereas small copepod species (Oithona, Pseudocalanus and others) contributed to the small size fraction (&amp;lt;1 mm). Estimated biomass of Calanus spp. and of the sum of small copepod species were both positively correlated with measured total zooplankton biomass (R2 = 0.72 and 0.34, respectively). The biomass ratio of small copepod species to Calanus was similar in Atlantic and Arctic water masses (~0.15–0.2) but tended to increase with decreasing total biomass. This suggests a shift to relatively larger roles of small copepods as Calanus and total biomass decrease.

Climate change dynamics and mercury temporal trends in Northeast Arctic cod (Gadus morhua) from the Barents Sea ecosystem

The Northeast Arctic cod (Gadus morhua) is the world's northernmost stock of Atlantic cod and is of considerable ecological and economic importance. Northeast Arctic cod are widely distributed in the Barents Sea, an environment that supports a high degree of ecosystem resiliency and food web complexity. Here using 121 years of ocean temperature data (1900–2020), 41 years of sea ice extent information (1979–2020) and 27 years of total mercury (Hg) fillet concentration data (1994–2021, n = 1999, ≥71% Methyl Hg, n = 20) from the Barents Sea ecosystem, we evaluate the effects of climate change dynamics on Hg temporal trends in Northeast Arctic cod. We observed low and consistently stable, Hg concentrations (yearly, least-square means range = 0.022–0.037 mg/kg wet wt.) in length-normalized fish, with a slight decline in the most recent sampling periods despite a significant increase in Barents Sea temperature, and a sharp decline in regional sea ice extent. Overall, our data suggest that recent Arctic amplification of ocean temperature, “Atlantification,” and other perturbations of the Barents Sea ecosystem, along with rapidly declining sea ice extent over the last ∼30 years did not translate into major increases or decreases in Hg bioaccumulation in Northeast Arctic cod. Our findings are consistent with similar long-term, temporal assessments of Atlantic cod inhabiting Oslofjord, Norway, and with recent investigations and empirical data for other marine apex predators. This demonstrates that Hg bioaccumulation is highly context specific, and some species may not be as sensitive to current climate change-contaminant interactions as currently thought. Fish Hg bioaccumulation-climate change relationships are highly complex and not uniform, and our data suggest that Hg temporal trends in marine apex predators can vary considerably within and among species, and geographically. Hg bioaccumulation regimes in biota are highly nuanced and likely driven by a suite of other factors such as local diets, sources of Hg, bioenergetics, toxicokinetic processing, and growth and metabolic rates of individuals and taxa, and inputs from anthropogenic activities at varying spatiotemporal scales. Collectively, these findings have important policy implications for global food security, the Minamata Convention on Mercury, and several relevant UN Sustainable Development Goals.

Public participation in beach clean-up activities to raise awareness and reduce marine litter for the protection of the Black Sea ecosystem

Human activities and poor awareness are believed to be responsible for marine litter pollution. In the scope of the European Union, Cross Border Cooperation, and Black Sea Basin (EU, CBC, BSB - 785) LitOUTer Project, “Raising Public Awareness and Reducing Marine Litter for the Protection of the Black Sea Ecosystem”, beach clean-up activities have been conducted. A beach clean-up activity was conducted at the Kıyıcık Beach, Trabzon, Turkiye involved by Stakeholders, NGOs, middle to high school, university students, teachers, and lecturers. This study aims to reveal the amount of marine litter at Kıyıcık Beach through public participation in beach clean-up activities. A total of 4488 solid wastes (∼100 kg) were collected and removed from the beach. The waste composition consisted of 50% plastic, 22% metal, 10% glass, 8% paper, 4% cloth, 1% metal, and 4% Covid-19-related waste. Plastic pieces, plastic bottles, and caps dominated the plastic litter on the beach. Moreover, 119 single-use face masks (Covid-19-related waste) were collected. Single-use plastic waste in the environment implies the impact of human activities and a lack of awareness regarding marine litter. Public participation in beach clean-up activities is expected to raise individual awareness and reduce marine litter to protect the Black Sea Ecosystem.

Benthic habitat mapping and assessment of seagrass species diversity in Da Lon Reef, Truong Sa Islands, Vietnam, using very high-resolution satellite imagery and in situ data

Benthic habitats are critical in shallow sea areas; they regulate the diversity and richness of organisms in each area. Mapping benthic habitats elucidates natural sea characteristics and aids in managing and using natural resources, as well as conserving marine biodiversity. This study established a benthic habitat map for the Da Lon Reef area, Truong Sa Islands, Vietnam, using Pléiades high-resolution remote sensing imaging materials and field survey results from 2020 and 2021. We identified seven classes of benthic habitats with a 91.64% overall accuracy, corresponding to a Kappa coefficient of 0.88. In the Da Lon Reef, seagrass biomes occupy a large area (more than 200 ha) and are distributed mainly inside lagoons at depths of 2–6 m. The field survey results identified five seagrass species and the biodiversity and biomass of seagrass populations in the lagoon of Da Lon Reef. The study results confirm the fundamental value of resources, biodiversity in general and seagrass in particular, in managing and protecting shallow sea ecosystems and biodiversity conservation in the Da Lon Reef area, an important part of the Truong Sa Islands, Vietnam.

Projections of winter polynyas and their biophysical impacts in the Ross Sea Antarctica

This study investigates winter polynyas in the southern Ross Sea, Antarctica where several polynyas are known to form. Coastal polynyas are areas of lower sea ice concentration and/or thickness along the coast that are otherwise surrounded by more extensive, thicker sea ice pack. Polynyas are also locations where organisms can exploit both the ice substrate and pelagic resources. Using a self organizing map algorithm, we identify polynya events in the Community Earth System Model Version 2 Large Ensemble (CESM2-LE). The neural network algorithm is able to identify polynya events without imposing an ice concentration or thickness threshold, as is often done when identifying polynyas. The CESM2-LE produces a wintertime polynya feature comparable in size and location to the Ross Sea polynya, and during polynya events there are large turbulent heat fluxes and export of sea ice from the Ross Sea. In the CESM2-LE polynya event frequency is projected to decrease sharply in the later twentyfirst century, leading to increasing sea ice concentrations and thicknesses in the region. The drivers of the polynya frequency decline are likely both large scale circulation changes and local atmosphere and ocean feedbacks. If declines in wintertime polynya frequency over the twentyfirst century do occur they may impact Antarctic Bottom Water formation and local net primary productivity. Thus, better understanding potential local and unexpected sea ice changes in the Ross Sea is important for both assessing climate system impacts and ecological impacts on the Ross Sea ecosystem, which is currently protected by an internationally recognized marine protected area.

The ecology and fishery of the vendace (Coregonus albula) in the Baltic Sea.

Brackish water ecosystems often have high primary production, intermediate salinities, and fluctuating physical conditions and therefore provide challenging environments for many of their inhabitants. This is especially true of the Baltic Sea, which is a large body of brackish water under strong anthropogenic influence. One freshwater species that is able to cope under these conditions in the northern Baltic Sea is the vendace (Coregonus albula), a small salmonid fish. Here, we review the current knowledge of its ecology and fishery in this brackish water environment. The literature shows that, by competing for resources with other planktivores and being an important prey for a range of larger species, C. albula plays a notable role in the northern Baltic Sea ecosystem. It also sustains significant fisheries in the coastal waters of Sweden and Finland. We identify the need to better understand these C. albula populations in terms of the predator-prey interactions, distributions of anadromous and sea spawning populations and other putative (eco)morphs, extent of gene exchange between the populations, and effects of climate change on their future. In this regard, we recommend strengthening C. albula-related research and management efforts by improved collaboration and coordination between research institutions, other governmental agencies, and fishers, as well as by harmonization of fishery policies across national borders.

Cod distribution in the Barents Sea under climate changes

The aim of the paper is to assess the impact of climate changes and oceanographic conditions on the distribution of cod stocks in the Barents Sea in recent decades. The material for the study was oceanographic data obtained during surveys in the Barents Sea by PINRO and other available information on hydrometeorological conditions of the sea in 1981–2021, as well as data onRussian catches of cod in the Barents Sea based on bottom trawl fishing operations. Methods of descriptive statistics as well as comparative, correlation and regression analyses were applied. Results: The modern changes in the climate and oceanographic conditions of the Barents Sea are described. Since the early 1980s, the warming has been observed against the background of increasing storm activity, having peaked in 2016. After that, despite still warm and low-ice conditions, there has been a cooling trend in the Barents Sea. Under climate changes in recent decades, cod made increasingly long migrations north and east, spreading more widely in the feeding areas. The most informative predictors in assessing the impactof climate changes and oceanographic conditions on the distribution of cod stocks in the Barents Sea were Arctic ice extent, area-averaged temperature at a depth of 100 m, Atlantic water area in the 50–100 m layer, and parameters of the Barents Sea thermal frontal zones. Practical significance: The obtained results are useful for a better understanding of the processes occurring in the Barents Sea ecosystem and, in the future, will be used to predict cod distributions in the sea, depending on oceanographic conditions and climate changes.

Epidemiology of Turbot (Scophthalmus maeoticus) Bacterial Contamination, a Fishery Limiting Factor on the Romanian Black Sea

The aim of this research was to evaluate the health status of the Scophthalmus maeoticus (Pallas, 1814) population from the Romanian marine area in 2016–2019, by identifying and investigating information about bacterial and constitutional diseases, establishing the influence of these bacterioses on the researched populations, and highlighting the main biological disorders (reproduction, growth, and feeding) that manifested in the analyzed fish. The bacterial diseases reported in S. maeoticus (Pallas, 1814) populations were caused by pathogens from the genera Vibrio, Aeromonas, and Pseudomonas. Numerous skin diseases, especially various types of “wounds”, lesions of bony tubercles, and tissue lesions may be the subsequent cause of neoplasms, as a result of fishing gear manipulations. The appearance of significant changes in the prevalence of neoplasia on the Romanian Black Sea coast can be considered an indicator of chronic stress (anthropogenic impact), rather than acute (environmental impact), and we suggest that the species could be used as a biological indicator of changes that may occur in the habitat in which it lives. In terms of future research directions, a combined analysis of the population structure, morphology and diseases determined in S. maeoticus populations, with a structural analysis of the habitat and bacteria contamination degree would be useful; this monitoring should be carried out regularly, to reveal changes in the Black Sea ecosystem, and to propose possible recommendations and protective measures.

Proteomic Approach to Anemonia sulcata and Its Symbiont Symbiodinium spp. as New Source of Potential Biotechnological Applications and Climate Change Biomarkers.

Marine ecosystems are among the richest in terms of biodiversity, and at present, still remain largely unknown today. In the molecular biology era, several analyses have been conducted to unravel the biological processes in this ecosystem. These systems have provided biotechnological solutions to current problems, including the treatment of diseases, as well as for the development of new biotechnological tools with applications in biomedicine and/or agri-food. In addition, in the context of climate change and global warming, these studies become even more necessary for the development of molecular tools that allow a reliable follow-up of this situation to anticipate alterations and responses of bioindicator species and to create a database to prevent and predict the environmental and climatic changes before the damage is irreversible. Proteomics approaches have revealed their potential use to obtain the set of biological effectors that lead to the real biological station on a specific stage, the proteins. In addition, proteomics-based algorithms have allowed the discovery of proteins with new potential biotechnological applications from proteome data through "applied proteomics". In this project, the first proteome analysis of the sea anemone, Anemonia sulcata, and its symbiont has been developed. These organisms present a wide distribution sea ecosystem. In Spain, it is accepted as a fishing and aquaculture species. Moreover, Anemonia sulcate has a symbiotic relation with autotroph Dinoflagellates, Symbiodinium spp., that allows the study of its relation at the molecular level. For the first characterization of A. sulcata proteome, three independent biological replicates were used, and proteins were extracted and analyzed by LC-MS/MS, allowing the quantification of 325 proteins, 81 from Symbiodinium spp. proteins and 244 from A. sulcata proteins. These proteins were subjected to gene ontology categorization by Cellular Component, Molecular Function and Biological Process. These analyzes have allowed the identification of biomarkers of gene expression as potential powerful emerging diagnostic tools to identify and characterize the molecular drivers of climate change stresses and improve monitoring techniques. In addition, through the application of novel algorithms for the detection of bioactive compounds based on the analysis of molecules of marine origin, the proteome has allowed the identification of proteins with potential applications in the fields of biomedicine and agri-food.

Super Climate Events

New environmental extremes are currently underway and are much greater than those in previous records. These are mostly regional, singular events that are caused by global change/local weather combinations and are larger than the impact of linear temperature increases projected using climate models. These new states cannot easily be assigned probabilities because they often have no historical analogs. Thus, the term super climate extremes is used. Examples are the loss of sea ice and ecosystem reorganization in northern marine Alaska, heatwave extreme in western Canada, and the loss of snow in Greenland. New combined extreme occurrences, which are reported almost daily, lead to a new, higher level of climate change urgency. The loss of sea ice in 2018–2019 was a result of warmer Arctic temperatures and changes in the jet stream. They resulted in a chain of impacts from southerly winds, the northward movement of predatory fish, and the reduction of food security for coastal communities. Record temperatures were measured in southwestern British Columbia following previous drought conditions, a confluence of two storm tracks, and warming through atmospheric subsidence. Greenland’s losses had clear skies and jet stream events. Such new extremes are present indicators of climate change. Their impacts result from the interaction between physical and ecological processes, and they justify the creation of a new climate change category based on super climate extremes.

Evaluation of fisheries management policies in the alien species-rich Eastern Mediterranean under climate change

Recent decades have witnessed declines in the amount of fishing catch due to changes in the marine ecosystem of the Eastern Mediterranean Sea. These changes are mainly a consequence of direct human activities as well as global warming and the entry of invasive species. Therefore, there is a need to improve fisheries management so that it accounts for the various stressors and uses of the marine environment beyond fishing, while providing sustainable catches and maintaining a healthy ecosystem. The ability to understand, and sustainably manage, the fishing industry relies on models capable of analyzing and predicting the effects of fishing on the entire ecosystem. In this study, we apply Ecospace, the spatial-temporal component of the Ecopath with Ecosim approach, to study the Israeli continental shelf to evaluate the impact of climate change and alternative management options on the ecosystem. We examine several management alternatives under the severe assumption of the RCP8.5 climate change scenario for the region. Results indicate that under business-as-usual conditions, the biomass of the native species will decrease, the biomass of the invasive species will increase, and there will be a decrease in the fishing catch. In addition, of the management alternatives examined, the alternative of prohibition of fishing in the northern region of Israel along with the establishment of a network of marine nature reserves provides the optimal response for the ecosystem and fisheries. The Achziv Nature Reserve is projected to be successful, improving the biomass of local species and reducing, to some extent, the presence of invasive species. These results are consistent with visual surveys conducted inside and outside the reserve by the Israeli Nature and Parks Authority. Furthermore, simulation results indicate spill-over effects in areas close to nature reserves yielding higher catches in those regions.

Monthly microplastics change in European anchovy's (Engraulis encrasicolus) gastrointestinal tract in the Black Sea

To contribute to a better understanding of the regional dynamics of MP pollution and its potential effects on the anchovy population and human health, here we assessed the presence and characterization of microplastics (MPs) in European anchovy (Engraulis encrasicolus), which is the most caught/consumed species in the Black Sea and is of vital importance to the ecosystem. A total of 360 individuals (30 per month) were sampled from the eastern Black Sea continental shelf all year round (monthly from September 20 to Aug 21). We extracted and digested the gastrointestinal tracts (GITs) of the samples with H2O2 and characterized the MPs in the GITs by stereomicroscope and ATR-FTIR. MPs varied between 0 and 0.43 MP individual−1. The morphological structure of MPs was composed of 51 % fiber > fragment (32.7 %) > film (12.2 %) > foam (4.1 %) and polymer types as PP (42.9 %) and PE (22.4 %). In the prevalence of MP colors, black (26.5 %) > white (24.5 %) > red (22.5 %) was observed. The mean MP size was 735.32 ± 836.62 μm, with no significant correlation between the abundance and size of ingested MPs and anchovy height/weight and GIT weight. We determined that MP abundance showed substantial differences between the fishing season (0.18 ± 0.05 MP ind−1) and the banned season (0.05 ± 0.03 MP ind−1). It is essential to develop effective waste management strategies to protect the vulnerable marine ecosystems of the Black Sea and ensure sustainable exploitation of living resources in this region. These strategies should be accompanied by robust monitoring and enforcement measures to guarantee their effectiveness and compliance.

Characteristics and seasonal variation of microplastics in the wastewater treatment plant: The case of Bursa deep sea discharge

Microplastics (MPs) are an emerging pollutant that can be detected in all ecosystems, especially aquatic ecosystems. Wastewater treatment plants (WWTPs) are important point sources of MP release into the sea. In this study, the characteristics of MPs in wastewater and sludge samples taken from different units of WWTP in Bursa-Gemlik district for 12 months were investigated. Wastewater and sludge samples collected from 7 different points were classified as size, shape, color, and counted. The amount of MP in the influent and effluent of the WWTP, respectively; 107.1 ± 40.2 MP/L and 4.1 ± 1.1 MP/L. Although the MP removal efficiency of the WWTP is 96.17 %, approximately 74,825,000 MP is discharged into the Marmara Sea every day. The amount of MP in the sludge is 14.3 ± 7.1 MP/g. The amount of MP accumulated in 22tons of waste sludge formed daily in WWTP was calculated as 314,600,000 MP, and the annual accumulated amount was calculated as approximately 1.15 × 1011 MP. The MPs in the WWTP were mainly 1–0.5 mm in size. Fibers were the dominant MP shape in both the wastewater and sludge samples. Black and transparent were the dominant MP colors. Seven different polymer types of MPs were detected, which were mainly types of polyethylene, polypropylene, and polyethylene terephthalate. Despite the high removal efficiency in the investigated WWTP, it has been shown that it acts as an important source of MPs to the sea ecosystem due to the high discharge rates.