Global Meta-Analysis and Review of Microplastic in Marine Copepods.

Plastic pollution has spread through all parts of the marine environment, representing a significant threat to species and ecosystems. This study investigates the role of copepods as widespread microplastic reservoirs in the marine environment, by performing, a systematic review, meta-analysis, and semiquantitative analysis of scientific articles focusing on the interaction between copepods and microplastics under field conditions. Our findings indicate that despite uniformly low ingestion of microplastics across different marine layers and geographical areas, with a slight uptake in neustonic copepods, copepods might constitute one of the largest marine microplastic reservoirs. This phenomenon is attributed more to their vast abundance than to average microplastic ingestion values. In this article, a framework for data analysis and reporting is proposed to facilitate future large-scale evaluations and modelling of their extent and impact on plastic and carbon cycles. These insights place copepods at the forefront of the marine plastic cycle, possibly affecting plastic distribution, and bioavailability, thereby opening new pathways for understanding the complex dynamics of microplastics in marine ecosystems.

The hyperbenthic environment: A forgotten habitat for plastic pollution.

This study investigates the abundances and composition of microplastics (MP) among the shallow layers of a coastal Mediterranean Marine Protected Area (Cabrera MPA), seafloor sediments, hyperbenthic environment, and the water column. The mid waters samples were collected mid-way between the sea surface and the seafloor and hyperbenthic samples at the water layer adjacent to the seafloor. Sampling was carried out on patchiness seafloor of Posidonia oceanica meadows. The seafloor sediments showed a mean abundance of 378,769.20 ± 508,109.11 MPs/m3, three orders of magnitude higher than the hyperbenthic (209.17 ± 117.07 MPs/m3), and the mid waters layer (106.48 ± 107.17 MPs/m3). An increasing vertical gradient in MP abundances, mainly composed of fibers was observed. Fibers were made-up mainly of polystyrene (PS, 25 %), expanded polystyrene (EPS, 18 %) and cellulose acetate (CA, 16 %). The results stress the need to increase efforts to find solutions to mitigate fiber pollution in the marine environment.

Breaking the paradigm: Marine sediments hold two-fold microplastics than sea surface waters and are dominated by fibers.

We conducted one of the first studies to integrate the quantification and characterization of microplastics (MPs), including fibers, in different habitats (sea surface, seafloor and beach sediments) of a coastal Mediterranean marine protected area, analyzing their ingestion in several marine species. The objectives of the study were to evaluate the distribution of MPs according to shape and polymer, to assess the contribution of fibers to local plastic pollution and to evaluate their ingestion in fish and invertebrates species that inhabit the study area (Pagrus pagrus, Serranus scriba, Spondyliosoma cantharus, Diplodus vulgaris, Oblada melanura, Holothuria forskalii, Holothuria tubularis, Holothuria polis, Arbacia lixula, Paracentrotus lividus, Modiolus barbatus, Mytilus galloprovincialis and Arca noae). A total of 111 environmental samples were analyzed. The mean abundance of MPs (excluding fibers) quantified in beach sediments (13,418.86 ± 28,787.99 MPs/m2) was two orders of magnitude higher than that found in seafloor sediments (76.92 ± 108.84 MPs/m2), which in turn was two orders of magnitude higher than sea surface samples (0.17 ± 0.39 MPs/m2). The fibers were the most abundant shape of MPs identified in all habitats. Variability in MPs ingestion was detected between species, with ingestion rates ranging from 43 % to 100 % for general MPs and ranging from 7 % to 100 % for fibers. The highest ingestion was observed in Holoturians, representing suitable bioindicators for plastic pollution. The composition of the polymer varies weakly depending on habitats and biota, but the result is strongly correlated with the morphology of the plastic. Fibers were mainly composed of cellulose acetate (29 %), styrofoam of polystyrene (18 %), and filaments, films and fragments of polyethylene and polypropylene. The results highlighted the need to expand integrated approaches to effectively study marine plastic pollution and to undertake efficient actions to limit the input of plastics, particularly fibers, into the marine environment.

Marine plastics in Mediterranean islands: Evaluating the distribution and composition of plastic pollution in the surface waters along four islands of the Western Sea Basin.

To study the spatial distribution of sea surface plastics in marine protected and non-protected areas, 65 sea surface trawls were carried out using a Hydro-bios manta net coupled with a 335-µm mesh. A total of 19 sampling sites along the coastal waters of Mallorca, the "Parque Nacional Marítimo-Terrestre del Archipiélago de Cabrera" and Menorca in the Balearic Islands as well as along coastal waters of The Natural Park of Columbretes Islands (NW Mediterranean Sea) were sampled. A total of 10,637 plastic items were identified and a subset of these items was categorized by shape, color, size and polymer composition. Plastic particles were found at each sampling site and in all samples. No microscale nor mesoscale variability in floating marine plastics abundance (particles/m2) was encountered throughout the study area where similar values were found in protected areas with no local land-based contamination sources, such as Columbretes [0.04 (±0.03) particles/m2], and in high anthropized areas, such as the island of Mallorca [0.04 (±0.07) particles/m2]. However, differences were found in characteristics of plastic items (shape, polymer, and size range), with the protected area of Columbretes characterized by the presence of the highest density of very small plastic items composed mainly of fragments (93%). Quantified plastics from the marine environment were composed mainly of polyethylene (PE, 63.3%), polypropylene (PP; 24.9%), polycarbonate (PC; 4.6%) and polystyrene (PS, 3.3%). The polymer composition showed a homogenous composition between islands and differences were detected only amongst Columbretes and the other islands. Results from this study provide further evidence of the ubiquity of plastics in the marine environment and highlight that remote and protected areas, such as Columbretes, are not exempt from plastic pollution, but receptor areas for small and aged floating plastics composed mainly by fragments, which might have potentially harmful effects on protected ecosystems.

Neustonic microplastics and zooplankton in coastal waters of Cabrera Marine Protected Area (Western Mediterranean Sea).

The high abundance of microplastics in marine environments is becoming a growing threat for Marine Protected Areas (MPAs). Recent studies have identified microplastics (MP) as having multiple effects on biota, and it is of special interest to highlight their effects on zooplanktonic organisms. These organisms play a key role on local food web structures and there is a need to better understand the accumulation of MPs and associated contaminants within the food web. The present study addresses MP distribution and composition within Cabrera MPA as well as its effects on local zooplanktonic community composition. Neustonic microplastic and zooplankton abundance and composition were determined in the shallow coastal waters of Cabrera MPA during the summer season of 2019. Samples were taken using a sea surface manta-net, with a mesh size of 335 µm. MPs were found in all manta trawl samples for a total of 7047 MP with an overall mean abundance (± SD) of 3.52 (± 8.81) items/m3, a value higher than those reported for the majority of Western Mediterranean Sea basins. Qualitative and semi-quantitative analyses of the local zooplankton community suggest that its composition could be sensitive to MP abundances. Although no correlation was found between overall mean abundance of MP and zooplankton, a positive correlation was found between MP abundance and the abundance of the planktonic stage of the foraminifer Rosalina globularis (Tretomphalus). This species seems to be able to use MP for its dispersion. On the other hand, a negative correlation between MP abundance and Copepoda abundance was detected. This work confirms that the coastal zooplankton community composition within the MPA of Cabrera are not exempt from MP pollution and suggests important and complex interactions between MP and zooplankton organisms in coastal waters.

Microplastic intake and enzymatic responses in Mytilus galloprovincialis reared at the vicinities of an aquaculture station.

Aquaculture is a potential source of microplastics (MPs) that could be strong stressors for marine organisms. In this study, we evaluated the effects of MPs derived from aquaculture in antioxidant defences and oxidative stress markers in gills of Mytilus galloprovincialis. Mussels were distributed in three areas with different impacts: inside aquaculture cages, Control 1 (located inside Andratx harbour) and Control 2 (located in a no-anthropized area). Samples were obtained along three different time periods in May (T0), July (T60) and in September (T120). At each sampling period, mussels' biometric measurements were taken, and tissue samples were kept frozen for biochemical determinations and to determine the intake of MPs. An increase in MPs intake was detected throughout the study, and this increase was significantly higher in samples from the aquaculture cages. Similarly, antioxidant enzyme activities (catalase, superoxide dismutase, glutathione reductase and glutathione peroxidase) were significantly higher in samples from cages at T120. Additionally, a similar tendency was observed in glutathione-s-transferase, with a higher activity in the aquaculture cages at T60 and T120. Malondialdehyde and carbonyl protein derivates as a marker of oxidative damage were also measured and samples from aquaculture cages presented higher oxidative stress markers, mainly in T120. In conclusion, living in environments exposed to aquaculture activities at sea may imply a higher intake of MPs which in turn might cause an antioxidant response in M. galloprovincialis which is not enough to avoid oxidative damage.

Impact of the marine litter pollution on the Mediterranean biodiversity: A risk assessment study with focus on the marine protected areas.

In this paper a novel methodology to assess the risk of marine litter (ML) pollution in the Mediterranean Sea is implemented. In this approach, the hazard component is estimated using a state-of-the-art 3D modeling system, which allows the simulation of floating and sinking ML particles; the exposure component is defined from biodiversity estimates; and the vulnerability is related to ML ingestion rates of each species. The results show that the hot-spots for the ML risk concentrate in the coastal regions, and are mainly conditioned by the biodiversity in the region. A dedicated analysis on the marine protected areas shows that the risk therein is controlled by the proximity to ML sources and that their present-day protection levels are not effective in the case of ML pollution. Only a reduction of ML at the sources could reduce the impact of ML pollution in protected areas.

Long-term exposure to virgin and seawater exposed microplastic enriched-diet causes liver oxidative stress and inflammation in gilthead seabream Sparus aurata, Linnaeus 1758.

Plastics accumulation in marine ecosystems has notable ecological implications due to their long persistence, potential ecotoxicity, and ability to adsorb other pollutants or act as vectors of pathogens. The present work aimed to evaluate the physiological response of the gilthead seabream (Sparus aurata) fed for 90 days with a diet enriched with virgin and seawater exposed low-density polyethylene microplastics (LDPE-MPs) (size between 100 and 500 µM), followed by 30 days of depuration, applying oxidative stress and inflammatory markers in liver homogenates. No effects of LDPE-MPs treatments on fish growth were observed throughout this study. A progressive increase in antioxidant enzyme activities was observed throughout the study in both treatments, although this increase was higher in the group treated with seawater exposed MPs. This increase was significantly higher in catalase (CAT), glutathione reductase (GRd), and glutathione-s-transferase (GST) in the seawater exposed MPs group, with respect to the virgin group. In contrast, no significant differences were recorded in superoxide dismutase (SOD) and glutathione peroxidase (GPx) between both groups. Exposure to MPs also caused an increase in the oxidative damage markers (malondialdehyde and carbonyls groups). Myeloperoxidase activity significantly increased because of MPs treatments. After 30 days of depuration, antioxidant, inflammatory enzyme activities and oxidative damage markers returned to values similar to those observed in the control group. In conclusion, MPs exposure induced an increase of antioxidant defences in the liver of S. aurata. However, these elevated antioxidant capabilities were not enough to prevent oxidative damage in the liver since, an increased oxidative damage marker was associated with MPs ingestion. The treatment with seawater exposed MPs caused a more significant antioxidant response (CAT, GRs, and GST). Although after a depuration period of 30 days a tendency to recover the initial values of the biomarkers was observed this does not seem to be time enough for a complete normalization.