The tolerance of a keystone ecosystem engineer to extreme heat stress is hampered by microplastic leachates.

Plastic pollution and ongoing climatic changes exert considerable pressure on coastal ecosystems. Unravelling the combined effects of these two threats is essential to management and conservation actions to reduce the overall environmental risks. We assessed the capacity of a coastal ecosystem engineer, the blue mussel Mytilus edulis, to cope with various levels of aerial heat stress (20, 25, 30 and 35°C) after an exposure to substances leached from beached and virgin low-density polyethylene pellets. Our results revealed a significant interaction between temperature and plastic leachates on mussel survival rates. Specifically, microplastic leachates had no effect on mussel survival at 20, 25 and 30°C. In turn, mussel survival rates significantly decreased at 35°C, and this decrease was even more significant following an exposure to leachates from beached pellets; these pellets had a higher concentration of additives compared to the virgin ones, potentially causing a bioenergetic imbalance. Our results stress the importance of adopting integrated approaches combining the effects of multiple environmental threats on key marine species to understand and mitigate their potential synergistic effects on ecosystem dynamics and resilience in the face of the changing environment.

Microplastic leachates inhibit small-scale self-organization in mussel beds.

Self-organized spatial patterns are increasingly recognized for their contribution to ecosystem functioning. They can improve the ecosystem's ability to respond to perturbation and thus increase its resilience to environmental stress. Plastic pollution has now emerged as major threat to aquatic and terrestrial biota. Under laboratory conditions, we tested whether plastic leachates from pellets collected in the intertidal can impair small-scale, spatial self-organization and byssal threads production of intertidal mussels and whether the effect varied depending on where the pellets come from. Specifically, leachates originating from plastic pellets collected from relatively pristine and polluted areas respectively impaired and inhibited the ability of mussels to self-organize at small-scale and to produce byssal threads compared to control conditions (i.e., seawater without leaching solution). Limitations to natural self-organizing processes and threads formation may translate to a declined capacity of natural ecosystems to avoid tipping points and to a reduced restoration success of disturbed ecosystems.

The effect of interspecific and intraspecific diversity on microplastic ingestion in two co-occurring mussel species in South Africa.

Interspecific and intraspecific diversity are essential components of biodiversity with far-reaching implications for ecosystem function and service provision. Importantly, genotypic and phenotypic variation within a species can affect responses to anthropogenic pressures more than interspecific diversity. We investigated the effects of interspecific and intraspecific diversity on microplastic ingestion by two coexisting mussel species in South Africa, Mytilus galloprovincialis and Perna perna, the latter occurring as two genetic lineages. We found significantly higher microplastic abundance in M. galloprovincialis (0.54 ± 0.56 MP items g-1WW) than P. perna (0.16 ± 0.21 MP items g-1WW), but no difference between P. perna lineages. Microbeads were the predominant microplastic (76 % in P. perna, 99 % in M. galloprovincialis) and polyethylene the prevalent polymer. Interspecific differences in microplastic abundance varied across locations, suggesting diverse sources of contamination. We suggest that microplastic ingestion can be species-specific even in organisms that coexist and play similar functional roles within ecosystems.

Size-dependent response of the mussel collective behaviour to plastic leachates and predator cues.

Both individual and collective anti-predator behaviours are essential for the survival of many species. This is particularly true for ecosystem engineers such as intertidal mussels, which through their collective behaviour create novel habitats for a range of organisms and biodiversity hotspots. However, contaminants may disrupt these behaviours and consequently indirectly affect exposure to predation risk at the population level. Among these, plastic litter is a major and ubiquitous contaminant of the marine environment. Here, we assessed the impact of microplastic (MP) leachates of the most produced plastic polymer, polypropylene (PlasticsEurope, 2022), at a high but locally relevant concentration (i.e. ca. 12 g L-1) on the collective behaviours and anti-predator responses of both small and large Mytilus edulis mussels. Indeed, in contrast to large mussels, small ones reacted to MP leachates, showing a taxis towards conspecifics and stronger aggregations. All mussels reacted to the chemical cues of the predatory crab, Hemigrapsus sanguineus, but with two different collective anti-predator behaviours. Small mussels only showed a taxis towards conspecifics when exposed to predator cues. This response was also found in large ones with a tendency to form more strongly bound aggregations and a considerable reduced activity, i.e. they significantly delayed their time to start to form aggregations and decreased their gross distance. These anti-predator behaviours were respectively inhibited and impaired in small and large mussels by MP leachates. The observed collective behavioural changes may reduce individual fitness by enhancing predation risk, particularly in small mussels that are the crab H. sanguineus's favourite preys. Given the key role of mussels as ecosystem engineers, our observations suggest that plastic pollution may have implication on M. edulis at the species level, but also enhancing a cascading effect towards a higher level of organisation such as population, community and ultimately structure and function of intertidal ecosystem.

Transcriptome wide analyses reveal intraspecific diversity in thermal stress responses of a dominant habitat-forming species.

The impact of climate change on biodiversity has stimulated the need to understand environmental stress responses, particularly for ecosystem engineers whose responses to climate affect large numbers of associated organisms. Distinct species differ substantially in their resilience to thermal stress but there are also within-species variations in thermal tolerance for which the molecular mechanisms underpinning such variation remain largely unclear. Intertidal mussels are well-known for their role as ecosystem engineers. First, we exposed two genetic lineages of the intertidal mussel Perna perna to heat stress treatments in air and water. Next, we ran a high throughput RNA sequencing experiment to identify differences in gene expression between the thermally resilient eastern lineage and the thermally sensitive western lineage. We highlight different thermal tolerances that concord with their distributional ranges. Critically, we also identified lineage-specific patterns of gene expression under heat stress and revealed intraspecific differences in the underlying transcriptional pathways in response to warmer temperatures that are potentially linked to the within-species differences in thermal tolerance. Beyond the species, we show how unravelling within-species variability in mechanistic responses to heat stress promotes a better understanding of global evolutionary trajectories of the species as a whole in response to changing climate.

Symbiont-induced phenotypic variation in an ecosystem engineer mediates thermal stress for the associated community.

Microbial symbionts have strong potential to mediate responses to climate change. Such modulation may be particularly important in the case of hosts that modify the physical habitat structure. By transforming the habitats, ecosystem engineers alter resource availability and modulate environmental conditions which, in turn, indirectly shape the community associated with that habitat. Endolithic cyanobacteria are known to reduce the body temperatures of infested mussels and here, we assessed whether the thermal benefits of endoliths on the intertidal reef-building mussel Mytilus galloprovincialis extends to the invertebrate community utilising mussel beds as habitat. Artificial reefs of biomimetic mussels either colonised or not colonised by microbial endoliths were used to test whether infauna species (the limpet Patella vulgata, the snail Littorina littorea and mussel recruits) in a mussel bed with symbionts experience lower body temperatures than those within a bed composed of mussels without symbionts. We found that infaunal individuals benefitted from being surrounded by mussels with symbionts, an effect that may be particularly critical during intense heat stress. Indirect effects of biotic interactions, complicate our understanding of community and ecosystem responses to climate change, especially in cases involving ecosystem engineers, and accounting for them will improve our predictions.

Comparative mitogenomic analyses and gene rearrangements reject the alleged polyphyly of a bivalve genus.

Background: The order and orientation of genes encoded by animal mitogenomes are typically conserved, although there is increasing evidence of multiple rearrangements among mollusks. The mitogenome from a Brazilian brown mussel (hereafter named B1) classified as Perna perna Linnaeus, 1758 and assembled from Illumina short-length reads revealed an unusual gene order very different from other congeneric species. Previous mitogenomic analyses based on the Brazilian specimen and other Mytilidae suggested the polyphyly of the genus Perna. Methods: To confirm the proposed gene rearrangements, we sequenced a second Brazilian P. perna specimen using the "primer-walking" method and performed the assembly using as reference Perna canaliculus. This time-consuming sequencing method is highly effective when assessing gene order because it relies on sequentially-determined, overlapping fragments. We also sequenced the mitogenomes of eastern and southwestern South African P. perna lineages to analyze the existence of putative intraspecific gene order changes as the two lineages show overlapping distributions but do not exhibit a sister relationship. Results: The three P. perna mitogenomes sequenced in this study exhibit the same gene order as the reference. CREx, a software that heuristically determines rearrangement scenarios, identified numerous gene order changes between B1 and our P. perna mitogenomes, rejecting the previously proposed gene order for the species. Our results validate the monophyly of the genus Perna and indicate a misidentification of B1.

Effects of habitat quality on abundance, size and growth of mussel recruits.

Recruitment of mussels is a complex process with the successful arrival of individuals hinging on the availability of suitable habitats. We examined the effects of adult mussels as settlement habitat and the degree to which the suitability of habitat they offer is species-specific by comparing the recruitment success of intertidal mussels. We hypothesised that mussel recruitment and early growth are dictated by the quality of habitat offered by conspecifics adults. We used a unique experimental arena on the south coast of South Africa, where Mytilus galloprovincialis and two lineages of Perna perna co-exist. Treatments were based on the translocation of individuals of M. galloprovincialis, western- and eastern lineage of P. perna to a single site, where artificial beds were created and sampled monthly over one year. Recruit's number, their sizes and growth were greater within beds of the western lineage of Perna than eastern lineage or Mytilus beds. The results clearly demonstrate that the quality of settlement habitat offered by adult beds differs among adult lineages/species and affects rates of settlement and the early growth of recruits. This effect extends to the intraspecific level; we found greater differences in density and growth of recruits between lineages of Perna than between either lineage and M. galloprovincialis. Supplementary Information: The online version contains supplementary material available at 10.1007/s10750-022-04994-7.

The relative effects of interspecific and intraspecific diversity on microplastic trapping in coastal biogenic habitats.

Our understanding of how anthropogenic stressors such as climate change and plastic pollution interact with biodiversity is being widened to include diversity below the species level, i.e., intraspecific variation. The emerging appreciation of the key ecological importance of intraspecific diversity and its potential loss in the Anthropocene, further highlights the need to assess the relative importance of intraspecific versus interspecific diversity. One such issue is whether a species responds as a homogenous whole to plastic pollution. Using manipulative field transplant experiments and laboratory-controlled hydrodynamic simulations, we assessed the relative effects of intraspecific and interspecific diversity on microplastic trapping in coastal biogenic habitats dominated by two key bioengineers, the brown intertidal macroalgae Fucus vesiculosus and F. guiryi. At the individual level, northern morphotypes of F. guiryi trapped more microplastics than southern individuals, and F. vesiculosus trapped more microplastics than F. guiryi. Canopy density varied among species, however, leading to reversed patterns of microplastic accumulation, with F. guiryi canopies accumulating more microplastics than those of F. vesiculosus, while no differences were observed between the canopies of F. guiryi morphotypes. We emphasize the importance of assessing the effects of intraspecific variation which, along with other crucial factors such as canopy density, flow velocity and polymer composition, modulates the extent of microplastic accumulation in coastal biogenic habitats. Our findings indicate that a realistic estimation of plastic accumulation in biogenic habitats requires an understanding of within- and between-species traits at both the individual and population levels.

Microplastic leachates disrupt the chemotactic and chemokinetic behaviours of an ecosystem engineer (Mytilus edulis).

The massive contamination of the environment by plastics is an increasing global scientific and societal concern. Knowing whether and how these pollutants affect the behaviour of keystone species is essential to identify environmental risks effectively. Here, we focus on the effect of plastic leachates on the behavioural response of the common blue mussel Mytilus edulis, an ecosystem engineer responsible for the creation of biogenic structures that modify the environment and provide numerous ecosystem functions and services. Specifically, we assess the effect of virgin polypropylene beads on mussels' chemotactic (i.e. a directional movement in response to a chemical stimulus) and chemokinetic (i.e. a non-directional change in movement properties such as speed, distance travelled or turning frequency in response to a chemical stimulus) responses to different chemical cues (i.e. conspecifics, injured conspecifics and a predator, the crab Hemigrapsus sanguineus). In the presence of predator cues, individual mussels reduced both their gross distance and speed, changes interpreted here as an avoidance behaviour. When exposed to polypropylene leachates, mussels moved less compared to control conditions, regardless of the cues tested. Additionally, in presence of crab cues with plastic leachates, mussels significantly changed the direction of movement suggesting a leachate-induced loss of their negative chemotaxis response. Taken together, our results indicate that the behavioural response of M. edulis is cue-specific and that its anti-predator behaviour as well as its mobility are impaired when exposed to microplastic leachates, potentially affecting the functioning of the ecosystem that the species supports.

A whale of a plastic tale: A plea for interdisciplinary studies to tackle micro- and nanoplastic pollution in the marine realm.

Plastic is one of the most ubiquitous sources of both contamination and pollution of the Anthropocene, and accumulates virtually everywhere on the planet. As such, plastic threatens the environment, the economy and human well-being globally. The related potential threats have been identified as a major global conservation issue and a key research priority. As a consequence, plastic pollution has become one of the most prolific fields of research in research areas including chemistry, physics, oceanography, biology, ecology, ecotoxicology, molecular biology, sociology, economy, conservation, management, and even politics. In this context, one may legitimately expect plastic pollution research to be highly interdisciplinary. However, using the emerging topic of microplastic and nanoplastic leachate (i.e., the desorption of molecules that are adsorbed onto the surface of a polymer and/or absorbed into the polymer matrix in the absence of plastic ingestion) in the ocean as a case study, we argue that this is still far from being the case. Instead, we highlight that plastic pollution research rather seems to remain structured in mostly isolated monodisciplinary studies. A plethora of analytical methods are now available to qualify and quantify plastic monomers, polymers and the related additives. We nevertheless show though a survey of the literature that most studies addressing the effects of leachates on marine organisms essentially still lack of a quantitative assessment of the chemical nature and content of both plastic items and their leachates. In the context of the ever-increasing research effort devoted to assess the biological and ecological effects of plastic waste, we subsequently argue that the lack of a true interdisciplinary approach is likely to hamper the development of this research field. We finally introduce a roadmap for future research which has to evolve through the development of a sound and systematic ability to chemically define what we biologically compare.

Symbiont-induced intraspecific phenotypic variation enhances plastic trapping and ingestion in biogenic habitats.

Plastic contamination has major effects on biodiversity, enhancing the consequences of other forms of global anthropogenic disturbance such as climate change and habitat fragmentation. Despite this and the recognised importance of intraspecific diversity, we still know relatively little about how plastic pollution affects diversity below the species level. Here, we assessed the effects of intraspecific variation in a habitat forming species (the Mediterranean mussel Mytilus galloprovincialis) on the trapping and ingestion of microplastics. We focused on symbiont-induced phenotypic variation in mussel beds. Using fractal analysis, we measured an increase in the complexity of mussel bed surfaces by ca. 15% caused by phototropic shell-degrading endoliths. By simulating high tide flow conditions and incoming waves, we found that symbionts significantly increased microplastic accumulation in mussel beds. This likely reflects deceleration of near-bed flow velocities, creation of turbulence in the bottom boundary layer and consequently increased particle retention. This effect was not constant at high tide, with no effect of infestation on retention at the base of the mussel bed under mid and high flow conditions and reduced microplastic trapping on the surface of mussel shells. Nevertheless, under natural conditions, the ingestion and trapping of microplastic were higher by the mussels comprising beds with symbionts than those in beds without symbionts. Given the dependency of many species on mussel biogenic habitats, there is an increased risk of plastics moving up the food chain in mussel beds infested by symbiotic endoliths. Our results highlight how the effects of within-species phenotypic diversity may influence the consequences of rising levels of plastic pollution.

Heads in the clouds: On the carbon footprint of conference-seeded publications in the advancement of knowledge.

The carbon footprint of flying overseas to conferences, meetings, and workshops to share and build knowledge has been increasingly questioned over the last two decades, especially in environmental and climate sciences, due to the related colossal carbon emissions. Here, we infer the value of scientific meetings through the number of publications produced either directly or indirectly after attending a scientific conference, symposium, or workshop (i.e., the conference-related production) and the number of publications produced per meeting (i.e., the conference-related productivity) as proxies for the academic value of these meetings, and relate them to both the number of meetings attended and the related carbon emissions. We show that conference-related production and productivity, respectively, increase and decay with the number of meetings attended, and noticeably that the less productive people exhibit the largest carbon footprint. Taken together, our results imply that a twofold decrease in the carbon footprint F CO 2 of a given scientist would result in a twofold increase in productivity through a fivefold decrease in the number of meeting attended. In light of these figures, we call for both the implementation of objective and quantitative criteria related to the optimum number of conferences to attend in an effort to maximize scientific productivity while minimizing the related carbon footprint, and the development of a rationale to minimize the carbon emission related to scientific activities.

Density-Dependent and Species-Specific Effects on Self-Organization Modulate the Resistance of Mussel Bed Ecosystems to Hydrodynamic Stress.

AbstractSelf-organized, regular spatial patterns emerging from local interactions among individuals enhance the ability of ecosystems to respond to environmental disturbances. Mussels self-organize to form large, regularly patterned biogenic structures that modify the biotic and abiotic environment and provide numerous ecosystem functions and services. We used two mussel species that form monospecific and mixed beds to investigate how species-specific behavior affects self-organization and resistance to wave stress. Perna perna has strong attachment but low motility, while Mytilus galloprovincialis shows the reverse. At low density, the less motile P. perna has limited spatial self-organization compared with M. galloprovincialis, while when coexisting, the two species formed random spatial patterns. At high density, the two species self-organized in similar ways, while when coexisting, patterns were less strong. Spatial pattern formations significantly shaped resistance to hydrodynamic stress. At low density, P. perna beds with strong attachment and M. galloprovincialis beds with strong spatial organization showed higher retention rates than mixed beds. At high density, the presence of strongly attached P. perna significantly increased retention in mixed and P. perna beds compared with M. galloprovincialis beds. Our study emphasizes the importance of the interplay of species-specific behaviors to spatial self-organization and stress tolerance in natural communities.

Foul-weather friends: Modelling thermal stress mitigation by symbiotic endolithic microbes in a changing environment.

Temperature extremes are predicted to intensify with climate change. These extremes are rapidly emerging as a powerful driver of species distributional changes with the capacity to disrupt the functioning and provision of services of entire ecosystems, particularly when they challenge ecosystem engineers. The subsequent search for a robust framework to forecast the consequences of these changes mostly ignores within-species variation in thermal sensitivity. Such variation can be intrinsic, but can also reflect species interactions. Intertidal mussels are important ecosystem engineers that host symbiotic endoliths in their shells. These endoliths unexpectedly act as conditionally beneficial parasites that enhance the host's resistance to intense heat stress. To understand how this relationship may be altered under environmental change, we examined the conditions under which it becomes advantageous by reducing body temperature. We deployed biomimetic sensors (robomussels), built using shells of mussels (Mytilus galloprovincialis) that were or were not infested by endoliths, at nine European locations spanning a temperature gradient across 22°of latitude (Orkney, Scotland to the Algarve, Portugal). Daily wind speed and solar radiation explained the maximum variation in the difference in temperature between infested and non-infested robomussels; the largest difference occurred under low wind speed and high solar radiation. From the robomussel data, we inferred body temperature differences between infested and non-infested mussels during known heatwaves that induced mass mortality of the mussel Mytilus edulis along the coast of the English Channel in summer 2018 to quantify the thermal advantage of endolith infestation during temperature extremes. Under these conditions, endoliths provided thermal buffering of between 1.7°C and 4.8°C. Our results strongly suggest that sustainability of intertidal mussel beds will increasingly depend on the thermal buffering provided by endoliths. More generally, this work shows that biomimetic models indicate that within-species thermal sensitivity to global warming can be modulated by species interactions, using an intertidal host-symbiont relationship as an example.

Microplastic leachates induce species-specific trait strengthening in intertidal mussels.

Plastic pollution is ubiquitous with increasing recognition of its direct effects on species' fitness. Little is known, however, about its more subtle effects, including the influence of plastic pollution on the morphological, functional and behavioral traits of organisms that are central to their ability to withstand disturbances. Among the least obvious but most pernicious forms of plastic-associated pollution are the chemicals that leach from microplastics. Here, we investigate how such leachates influence species' traits by assessing functional trait compensation across four species of intertidal mussels, through investigations of byssal thread production, movement and aggregation behavior for mussels held in natural seawater or seawater contaminated by microplastic leachates. We found no evidence for compensation of functional traits, but for each species, microplastic leachates reinforced one trait while others remained unaffected. Two species (Perna perna and Mytilus galloprovincialis), were characterized by a resistance strategy to disturbance; they produced more byssal threads in microplastic leachate seawater than in control seawater, while motility and aggregation remained essentially unaffected. In contrast, the other two species (M. edulis and Choromytilus meridionalis), showed a resilience strategy to disturbance through increased motility and aggregation in leachate seawater, while byssal thread production remained unaffected. These results suggest that the competitive abilities of intertidal mussels may be related to their sensitivity to microplastic leachates or other chemical disturbance. Importantly, the trait strengthening observed will affect the ability of these mussels to form spatially patterned beds, with implications for their quality as autogenic ecological engineers or foundation species. Thus, our findings have implications for the ability of mussel beds to tolerate disturbance, and hence for central ecosystem services, such as their ability to support biodiversity and enhance secondary and tertiary production. The results suggest that an inconspicuous aspect of plastic pollution has the potential to influence other communities and ecosystems in powerful ways.

Small scale habitat effects on anthropogenic litter material and sources in a coastal lagoon system.

Anthropogenic litter is ubiquitous throughout marine ecosystems, but its abundance and distribution are driven by complex interactions of distinct environmental factors and thus can be extremely heterogeneous. Here we compare the extent of anthropogenic litter pollution at a sheltered lagoon habitat and nearby open coast sites. Monthly surveys over a period of five months showed that both the types and sources of litter always differed significantly between lagoon and open coast sites. Pollution within the lagoon was mainly land-derived and was largely made up of construction materials (70% to 95%). At open coast sites, construction materials represented a minor portion of pollution (4% to 12%) while plastics were the most abundant (82% to 95%). We show that stranded anthropogenic litter in adjacent marine habitats can differ significantly and stress the importance of sampling at appropriate spatial scales to gain realistic insights into the sources of pollution.

Historical and contemporary range expansion of an invasive mussel, Semimytlius algosus, in Angola and Namibia despite data scarcity in an infrequently surveyed region.

Understanding the spread of invasive species in many regions is difficult because surveys are rare. Here, historical records of the invasive marine mussel, Semimytilus algosus, on the shores of Angola and Namibia are synthesised to re-construct its invasive history. Since this mussel was first discovered in Namibia about 90 years ago, it has spread throughout the western coast of southern Africa. By the late 1960s, the species was well established across a range of 1005 km of coastline in southern Angola and northern Namibia. Although only coarse spatial resolution data are available since the 1990s, the distribution of S. algosus clearly increased substantially over the subsequent decades. Today, the species is distributed over 2785 km of coastline, appearing in southern Namibia in 2014, whence it spread across the border to northern South Africa in 2017, and in northern Angola in 2015. Conspicuously, its current range appears to be relatively contiguous across at least 810 km of shore in southern Angola and throughout Namibia, with isolated, spatially disjunct occurrences towards the southern and northern limits of its distribution. Despite there being few occurrence records that are unevenly distributed spatially and temporally, data for the distributional patterns of S. algosus in Angola and Namibia provide invaluable insights into how marine invasive species spread in developing regions that are infrequently monitored.

Intraspecific diversity in an ecological engineer functionally trumps interspecific diversity in shaping community structure.

Can intraspecific diversity functionally supersede interspecific diversity? Recent studies have established the ecological effects of intraspecific variation on a number of ecosystem dynamics including resilience and productivity and we hypothesised that they may functionally exceed those of species diversity. We focused on a coastal ecosystem dominated by two coexisting bioengineering mussel species, one of which, Perna perna, displays two distinct phylogeographic lineages. A manipulative field experiment revealed greater habitat structural complexity and a more benign microscale environment within beds of the eastern lineage than those of the western lineage or the second species (Mytilus galloprovincialis); the latter two did not differ. Similarly, while infaunal species abundance and biomass differed significantly between the two lineages of Perna, there was no such difference between Mytilus and the western Perna lineage. The evenness and diversity of associated infaunal assemblages responded differently. Diversity differed relatively weakly between species, while evenness showed a very strong difference between conspecific lineages. Our results show that variation within a species can functionally supersede diversity between species. As the two P. perna lineages have different physiological tolerances, we expect them to react differently to environmental change. Our findings indicate that predicting the ecosystem-level consequences of climate change requires an understanding of the relative strengths of within- and between-species differences in functionality.

Species-specific plastic accumulation in the sediment and canopy of coastal vegetated habitats.

Plastic waste has become ubiquitous in ecosystems worldwide. Few, recent studies report evidence of coastal vegetated habitats acting as sink for plastics, yet assessments have been completed either for macro or microplastics and focussing on just one type of vegetated habitat. Here, we investigated the role of marine coastal vegetated habitats as sinks for macro (≥5 mm) and microplastics (<5 mm) through a comprehensive, multi-habitat approach. We assessed the occurrence, abundance and physical properties of macro and microplastics in the canopy and superficial sediment of two intertidal (seagrass Zostera noltei, saltmarsh Sporobolus maritimus) and two subtidal (mixed seagrass meadows of Cymodocea nodosa and Zostera marina, rhizophytic macroalga Caulerpa prolifera) habitats in the Ria Formosa lagoon (Portugal). Our results showed that coastal vegetated habitats trapped macro and microplastics in the sediment at variable degrees (1.3-17.3 macroplastics 100 m-2, and 18.2-35.2 microplastics kg-1). Macroplastics accumulated in all vegetated habitat but not in nearby unvegetated areas, yet only S. maritimus habitat presented a significant trapping effect. Microplastics occurred in the sediment of all vegetated and unvegetated areas with similar abundances and high variability. Microplastics, all of type fibre, were recorded on all canopies except for S. maritimus. Overall, the trapping capacity of microplastics in the sediment and on the canopy was higher for subtidal than for intertidal vegetated habitats. We conclude that generalizations in the trapping effect of coastal vegetated areas should be done with caution, since it may be highly variable and may depend on the plastic size, habitat and tidal position. Since these habitats support a high biodiversity, they should be included in assessments of plastic debris accumulation and impacts in coastal areas. Further research, including experimental studies, is needed to shed more light on the role of coastal vegetated habitats as plastic sinks.