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The accumulation of human-derived waste on our coasts is an escalating phenomenon, yet the relative importance and potential interactions among its main drivers are not fully understood. We used citizen-science standardized collections to investigate how anthropogenic and environmental factors influence the level, composition, and temporal variation of beach debris. An average of 58 kg and 803 items/100 m, dominated by single-use items of land (rather than sea) origin, were collected in the 881 beaches sampled. Interactions between anthropogenic and environmental factors (e.g., human use × beach substrate) were the strongest predictors of beach debris, accounting for 34% of the variance explained in its amount and composition. Beach debris showed a highly stochastic temporal variation (adjusted R 2 = 0.05), partly determined by interactions between different local and landscape anthropogenic pressures. Our results show that both environmental and anthropogenic factors (at the local and landscape scale) co-determine the level and composition of beach debris. We emphasize the potential of citizen-science to inform environmental policy, showing that land-originated single-use items dominate beach debris, and the importance of considering their multiple anthropogenic and environmental drivers to improve our low predictive power regarding their spatio-temporal distribution., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Determining the sources of marine litter is necessary to mitigate this increasing global problem. Plastic bottles are useful tracers of marine litter and constitute the main item (24%) stranding on remote beaches in the Galapagos Islands. The aim of this study was to estimate the abundance of plastic bottles in remote beaches and inferred their sources. To do so, we collected plastic bottles at 60 remote Galapagos Island beaches from 2018 to 2022. 76% of beaches were qualified as badly polluted, with >34 bottles·100 m -1 . Most identified bottles came from Peru (71%), followed by China (17%) and Ecuador (9%). Although most locally-sold products are made in Ecuador, they contribute little to beach litter loads. Polyethylene terephthalate bottles with lid (necessary for litter dispersal) represented 88% of all bottles, demonstrating that most of the litter reaching the Galapagos comes from distant sources, mainly from South America. However, bottle ages indicate that at least 10% of Peruvian, 26% of Ecuadorian, and all Chinese bottles likely were dumped from ships. Reducing marine litter reaching the Galapagos Islands requires tackling litter leakage from land-based sources in South America and better compliance with regulations banning the dumping of plastics and other persistent wastes from ships., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Plastic pollution is a global environmental threat. Remote and pristine islands are not safe from this threat. Here, we estimated beach macro- (>25 mm), meso- (5-25 mm) and microdebris (<5 mm) levels in Galapagos and studied the role of environmental variables determining their accumulation. The vast majority of beach macro- and mesodebris were plastic, while most microdebris were cellulosic. The levels of beach macro-, meso- and microplastics were notably high and comparable with exceptional levels reported in contaminated areas. Oceanic currents and the anthropic pressure of use of the beach were the main factors that determined the level of macro- and mesoplastics, as well as the diversity of items, with more types of items in the beaches facing the predominant current. Microplastic levels were mainly driven by the slope and, to some extent, the grain size of the sediment in the beach. The absence of relationship between the levels of large size debris and the level of microplastics suggests that secondary microplastics that accumulated in the beaches were previously fragmented before arriving to the beach. This differential influence of environmental factors in the accumulation of marine debris according to their size should be taken into account when developing strategies to mitigate plastic pollution. Additionally, this study reports high levels of marine debris reported in a remote and protected area such as Galapagos, which are comparable to areas with direct sources of marine debris. This is especially worrying for Galapagos since the sampled beaches are cleaned at least annually. This fact highlights the global dimension of this environmental threat that demands further extensive international commitment to conserve some of the last paradises on Earth., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.)

While the use of biodegradable polymers is recognized as a global strategy to minimize plastic pollution, the technical standards (TS) used to attest their biodegradability may not be in compliance with most environmental parameters observed aquatic ecosystems. Indeed, through a careful assessment of the TS currently in use, this study evidenced that these guidelines cover only a fraction of the biogeochemical parameters seen in nature and largely disregard those that occur in the deep-sea. Thus, these TS may not be able to ensure the degradation of such polymers in natural environments, where microbial activity, pH, temperature, salinity, UV radiation and pressure are highly variable. This raises environmental concern, since relevant parcel of plastic ends up in the oceans reaching deep zones. Therefore, there is an urgent need to revise these TS, which must consider the actual fate of most plastic debris and include assessments under the challenging conditions found at these types of environment, alongside microplastic formation and ecotoxicology effects. Moreover, the next generation of biodegradability tests must be designed to enable a cost-effective implementation and incorporate accurate analytical techniques to assess polymer transformation. Furthermore, certification should provide information on time scale and degradation rates and, preferably, be globally harmonized., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The seabed constitutes a global sink for plastic debris, where they can remain for centuries. Biodegradable plastics offer the advantage of having less persistence in the environment than conventional ones. The seabed is responsible for key ecosystem functions related to the cycling of elements by decomposing the labile fraction of organic matter and fueling primary production, while storing the most recalcitrant part of this organic matter and limiting CO 2 emissions. Although plastics are expected to affect these processes, knowledge on this matter is scarce. In controlled microcosms, we show that biodegradable plastics can stimulate the decomposition of marine-buried carbon and reduce the release of inorganic nitrogen. We found that conventional and biodegradable plastics promoted anaerobic sediment metabolic pathways. Biodegradable plastics produced a two-fold CO 2 release to the water column, which suggests the decomposition of not only plastics, but also of buried organic carbon. The stimulation of sediment metabolism could be due to excessive carbon consumption by bacteria that derives from a rise in the carbon:nitrogen ratio. Accordingly, the NH 4 + flux to the water column lowered. As NOx fluxes also lowered, biodegradable plastics might promote nitrification-denitrification coupling. If biodegradable plastics become a major component of marine pollution, then sediment biogeochemical cycles might be strongly influenced, which could affect the carbon sequestration of coastal ecosystems and compromise their mitigation capacity against climate change., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Climate change is introducing new stressors into already stressed ecosystems. Among these, extreme events such as heat waves play a crucial role in determining the structure of ecosystems. We tested single and combined effects of overgrazing, burial and heat waves on the seedlings of the habitat-forming species Posidonia oceanica. At current heat wave temperatures, overgrazing in isolation had more deleterious effects than seed burial, and effects were synergistic and additive when both factors co-occurred. The combined effect of overgrazing and seed burial with current heat waves could hamper P. oceanica seedling development, with similar or even higher levels than the sole effect of heat waves in the near future (29 °C). The effects of overgrazing and seed burial are expected to be overridden if heat waves temperatures exceed 29 °C. These results suggest that co-occurring environmental stressors, in combination with current heat waves, could compromise the sexual recruitment of this seagrass., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The perdurability of plastics in the environment is one of the major concerns of plastic pollution and, as a consequence, oceans are accumulating large amounts of plastic. The degradation of conventional and biobased materials was evaluated through a laboratory experiment for a year simulating four different conditions in the marine environment. The water column environmental compartment was simulated under euphotic and aphotic (with and without light availability) conditions. The seafloor environmental compartment was simulated with sediment under non-polluted and polluted conditions. By combining weight loss (%), spectroscopic and thermal analyses, the degradation patterns regarding the polymer structure were assessed. The studied biobased materials were polylactic acid (PLA) based materials and showed higher degradability than conventional ones. The weight loss of conventional materials was not influenced by the water column or sediment, while in PLA-based materials, the degradation rates were ca. 5 times greater in the sediment than in the water column. The absorbance (Abs) value at 3400 cm -1 for polyethylene terephthalate (PET), and carbonyl (CO) index for PET and PLA could be useful to detect early signs of degradation. The crystallization index could be a useful parameter to discriminate degradation stages. The obtained results highlight the different degradability rates of materials depending on the specific environmental marine conditions., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The seagrass Posidonia oceanica is considered one of the oldest and largest living organisms on Earth. Notwithstanding, given the difficulty of monitoring its fruits and seeds in the field, the development of P. oceanica during its sexual recruitment is not completely understood. We studied the stages of development of P. oceanica seeds from their dispersion in the fruit interior to their settlement in sediment through histological, ultrastructural and mesocosm experiments. P. oceanica sexual recruitment can be divided into three main stages that focus on maximising photosynthesis and anchoring the seedlings to the sediment. In the first stage (fruit dispersion), seeds perform photosynthesis while being transported inside the fruit along the sea surface. In the second stage (seed adhesion), seeds develop adhesive microscopic hairs that cover the primary and secondary roots and favour seed adhesion to the substrate. In the last stage (seedling anchorage), roots attach the seedlings to the substrate by orienting them towards the direction of light to maximise photosynthesis. The adaptations observed in P. oceanica are similar to those in other seagrasses with non-dormant seeds and fruits with membranous pericarps, such as Thalassia sp. and Enhalus sp. These common strategies suggest a convergent evolution in such seagrasses in terms of sexual recruitment. Understanding the sexual recruitment of habitat-forming species such as seagrasses is necessary to adequately manage the ecosystems that they inhabit., Competing Interests: The authors have declared that no competing interests exist.

Extreme weather events are major drivers of ecological change, and their occurrence is likely to increase due to climate change. The transient increases in atmospheric temperatures are leading to a greater occurrence of heat waves, extreme events that can produce a substantial warming of water, especially in enclosed basins such as the Mediterranean Sea. Here, we tested the effects of current and predicted heat waves on the early stages of development of the seagrass Posidonia oceanica. Temperatures above 27 °C limited the growth of the plant by inhibiting its photosynthetic system. It suffered a reduction in leaf growth and faster leaf senescence, and in some cases mortality. This study demonstrates that the greater frequency of heat waves, along with anticipated temperature rises in coming decades, are expected to negatively affect the germination of P. oceanica seedlings., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Extreme climatic events have a major role in the structuring of biological communities, and their occurrence is expected to increase due to climate change. Here I use a manipulative approach to test the effects of extreme storm events on rocky mid-shore assemblages. This study shows that an extreme storm can cause more negative effects than several mild storms, primarily by bringing the biological assemblages towards early stages of succession. This finding contrasts with the effects of clustering of climatic events due to climate change, which are expected to mitigate its ecological impacts. Thus, the ecological consequences of climatic events that are influenced by climate change may have contrasting effects depending on the features that are considered. These results have relevant implications in the forecasting of the ecological consequences of climate change and should be considered when designing measures to mitigate its effects.

Coastal biogeochemical cycles are expected to be affected by global warming. By means of a mesocosm experiment, the effect of increased water temperature on the biogeochemical cycles of coastal sediments affected by organic-matter enrichment was tested, focusing on the carbon, sulfur, and iron cycles. Nereis diversicolor was used as a model species to simulate macrofaunal bioirrigation activity in natural sediments. Although bioirrigation rates of N. diversicolor were not temperature dependent, temperature did have a major effect on the sediment metabolism. Under organic-enrichment conditions, the increase in sediment metabolism was greater than expected and occurred through the enhancement of anaerobic metabolic pathway rates, mainly sulfate reduction. There was a twofold increase in sediment metabolism and the accumulation of reduced sulfur. The increase in the benthic metabolism was maintained by the supply of electron acceptors through bioirrigation and as a result of the availability of iron in the sediment. As long as the sediment buffering capacity toward sulfides is not surpassed, an increase in temperature might promote the recovery of organic-enriched sediments by decreasing the time for mineralization of excess organic matter.

The changes in the biofilm community due to organic matter enrichment, eutrophication and metal contamination derived from fish farming were studied. The biofilm biomass, polysaccharide content, trophic niche and element accumulation were quantified along an environmental gradient of fish farm wastes in two seasons. Biofilm structure and trophic diversity was influenced by seasonality as well as by the fish farm waste load. Fish farming enhanced the accumulation of organic carbon, nutrients, selenium and metals by the biofilm community. The accumulation pattern of these elements was similar regardless of the structure and trophic niche of the community. This suggests that the biofilm communities can be considered a reliable tool for assessing dissolved aquaculture wastes. Due to the ubiquity of biofilms and its wide range of consumers, its role as a sink of dissolved wastes may have important implications for the transfer of aquaculture wastes to higher trophic levels in coastal systems., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

The aim of this work was to study the dispersion of particulate wastes derived from marine fish farming and correlate the data with the impact on the seabed. Carbon and nutrients were correlated with the physico-chemical parameters of the sediment and the benthic community structure. The sedimentation rates in the benthic system were 1.09, 0.09 and 0.13 g m⁻² day⁻¹ for particulate organic carbon (POC), particulate organic nitrogen (PON) and total phosphorus (TP), respectively. TP was a reliable parameter for establishing the spatial extent of the fish farm particulate wastes. Fish farming was seen to influence not only physico-chemical and biological parameters but also the functioning of the ecosystem from a trophic point of view, particularly affecting the grazers and the balance among the trophic groups. POC, PON and TP sedimentation dynamics reflected the physico-chemical status of the sediment along the distance gradient studied, while their impact on the benthic community extended further. Therefore, the level of fish farm impact on the benthic community might be underestimated if it is assessed by merely taking into account data obtained from waste dispersion rates. The benthic habitat beneath the fish farm, Maërl bed, was seen to be very sensitive to aquaculture impact compared with other unvegetated benthic habitats, with an estimated POC-carrying capacity to maintain current diversity of 0.087 g C m⁻² day⁻¹ (only 36% greater than the basal POC input). Environmental protection agencies should define different aquaculture waste load thresholds for different benthic communities affected by finfish farming, according to their particular degree of sensitivity, in order to maintain natural ecosystem functions., (© 2010 Elsevier Ltd. All rights reserved.)

The assessment of sediment contamination is of crucial importance for the management of estuarine ecosystems. Environmental risk assessment of oil pollution must be specific to these ecosystems because of their unique toxicant bioavailability dynamics, which is not comparable with that of other ecosystems where the environmental parameters are less variable. The goal of this work was to test in two European estuarine areas (Ria de Aveiro, Portugal; La Manga, Spain) whether the common methodology used to evaluate sediment pollution in marine sediment (amphipod toxicity tests and community structure analysis) is suited to these physico-chemically unique systems. Manipulative field experiments were conducted at three oil concentration levels, to compare resulting changes in community structure with laboratory and in situ amphipod toxicity tests carried out with native amphipod species Corophium multisetosum (Atlantic area) and Microdeutopus gryllotalpa (Mediterranean area). The impact of the toxicant was reflected in the community structure and toxicity tests, both of which were correlated with oil concentration. These results point to this methodology being a reliable tool for assessing and monitoring pollution in estuarine areas.

ABSTRACT The effect of phenanthrene, fluoranthene, and pyrene in dimethyl sulfoxide on the amphipods Gammarus aequicauda, Gammarus locusta, and Corophium multisetosum was tested in a static exposure in sea water. The 48-h lethal concentration (LC(50)) of phenanthrene was 173.85 mug/L for G. aequicauda, 147.64 mug/L for G. locusta, and 215.20 mug/L for C. multisetosum. The 48-h LC(50) of fluoranthene was 49.99 mug/L for G. aequicauda, 42.71 mug/L for G. locusta, and 2.85 mug/L for C. multisetosum. The 48-h LC(50) of pyrene was 73.49 mug/L for G. aequicauda, 60.78 mug/L for G. locusta, and 25.29 mug/L for C. multisetosum. Together with their wide distribution along European coasts, the evidence of toxicity on the tested PAH compounds in these amphipods make these species appropriate candidates for evaluating oil-contaminated sediments in Europe.

Fish farming is an important source of organic matter input in coastal waters, which contributes to eutrophication. In this study, the macrofaunal benthic community was studied after the cessation of fish farming with the aim of improving our understanding of benthic succession and sediment recovery in a marine ecosystem. The results showed that the best environmental variables for assessing organic pollution were acid-volatile sulfides (AVS) and redox potential. Succession and recovery was best explained by macrofaunal analysis based on community composition as well as on trophic groups. The patterns of recovery differed between each impacted station. For this reason, succession could not be accurately predicted due to the unique environmental parameters and the singular community functional structure of each location. The Azti Marine Benthic Index (AMBI) proved its validity for assessing pollution but did not distinguish between successional stages.