Fifty-year study of microplastics ingested by brachyuran and fish larvae in the central English North Sea.

Microplastics (MPs) are ubiquitous pollutants in marine environments. Among the many detrimental consequences of microplastic pollution, its consumption by marine biota is of particular relevance for human health, due to exposure through the food web. Long-term time-series biotic samples are overlooked sources of information for microplastics research. These collections are extremely valuable for the detection and monitoring of changes in marine environments. However, there are very few long-term studies (>10 years) of the uptake of microplastics by biota. Here, we used Dove Time Series planktonic samples (from 1971 to 2020) to assess the presence and prevalence of microplastics in the English North Sea coast over time. Fish and brachyuran larvae were selected due to their commercial importance and consequent implications for human health. A custom enzymatic digestion method was used to extract microplastics for FTIR-ATR polymer identification. An increasing cumulative trend in MP ingestion was identified. Cellophane and polyethylene terephthalate were the polymer types found most frequently in both taxa. Although a total higher microplastics uptake was observed in fish, consumption was not significantly different between taxa over time. Equally, results were not clearly related to microplastics shape or polymer type. This work did not find significant long-term evidence on the increasing uptake of microplastic particles by zooplankton over time. However, the results of this report identified additives, plasticisers, and other more complex and hazardous compounds that should not be released to the environment (e.g., bis-(2-hydroxyethyl) dimerate, propylene glycol ricinoleate) inside marine biota. The study detailed herein provides a case study for the use of long-term time-series in providing accurate assessments of microplastic pollution in marine biota.

Enzymatic digestion method development for long-term stored chitinaceous planktonic samples.

Different extraction methods have been proposed to study the ingestion of microplastics by marine organisms, including enzymatic digestion. While mussels have been the focus of research, crustaceans' enzymatic digestion has received little attention. An overlooked source of information for microplastic research is analysis of long-term time-series biotic samples. These collections are invaluable for the detection and monitoring of changes in ecosystems, especially those caused by anthropogenic factors. Here, crustacean larvae collected in two periods, 1985 and 2020, in the central North Sea were used to develop and optimise an effective and gentle enzymatic digestion method suitable for microplastic research. Sequential breakdown of these chitinaceous samples via a mechanical and surfactant (Sodium Dodecyl Sulphate 1% v/v) pre-treatment, followed by proteinase K (100 mU/mL) and chitinase (50 mU/mL) digestion, efficiently removed >96% of biomass of 1985 and 2020 samples. The optimised method was effective without interfering with the identification of naturally weathered microplastics via FTIR Spectroscopy.

Global-scale species distributions predict temperature-related changes in species composition of rocky shore communities in Britain.

Changes in rocky shore community composition as responses to climatic fluctuations and anthropogenic warming can be shown by changes in average species thermal affinities. In this study, we derived thermal affinities for European Atlantic rocky intertidal species by matching their known distributions to patterns in average annual sea surface temperature. Average thermal affinities (the Community Temperature Index, CTI) tracked patterns in sea surface temperature from Portugal to Norway, but CTI for communities of macroalgae and plant species changed less than those composed of animal species. This reduced response was in line with the expectation that communities with a smaller range of thermal affinities among species would change less in composition along thermal gradients and over time. Local-scale patterns in CTI over wave exposure gradients suggested that canopy macroalgae allow species with ranges centred in cooler than local temperatures ('cold-affinity') to persist in otherwise too-warm conditions. In annual surveys of rocky shores, communities of animal species in Shetland showed a shift in dominance towards warm-affinity species ('thermophilization') with local warming from 1980 to 2018 but the community of plant and macroalgal species did not. From 2002 to 2018, communities in southwest Britain showed the reverse trend in CTI: declining average thermal affinities over a period of modest temperature decline. Despite the cooling, trends in species abundance were in line with the general mechanism of direction and magnitude of long-term trends depending on the difference between species thermal affinities and local temperatures. Cold-affinity species increased during cooling and warm-affinity ones decreased. The consistency of responses across different communities and with general expectations based on species thermal characteristics suggests strong predictive accuracy of responses of community composition to anthropogenic warming.

The interaction between nutrient availability and disturbance frequency on the diversity of benthic marine communities on the north-east coast of England.

1. Several theoretical models predict under what conditions maximum species diversity can be maintained, and they are often used to develop effective ecosystem management plans. 2. Two models that are currently used to predict patterns of species diversity were empirically tested in marine subtidal benthic communities of different successional stages. 3. The two models were: the interactive effects of nutrient availability and disturbance frequency proposed by Kondoh (2001; Proceedings of the Royal Society London B, 268, 269-271), and the intermediate disturbance hypothesis (IDH) proposed by Connell (1978; Science, 199, 1302-1310). 4. Interactive effects were found to be transient and only occurred in the older communities, while the unimodal pattern suggested by the IDH was not supported in either successional stage. 5. It is concluded that these models are very general and thus lack sufficient explanatory power. Both models require a number of specific prerequisites for maximum diversity to be found, and though applicable in many different ecosystems they need to be refined as tools in order that they can be effectively used in habitat management plans.