Interaction of climate change and marine pollution in Southern India: Implications for coastal zone management practices and policies.

Climate change and marine litter are inextricably linked, and their interaction manifests differently depending on the specific environmental and biological characteristics, and other human activities taking place. The negative impacts resulting from those synergistic interactions are threatening coastal and marine ecosystems and the many goods and services they provide. This is particularly pervasive in the coastal zone of the Indian subcontinent. India is already experiencing severe climate change impacts, which are projected to worsen in the future. At the same time, the country is gripped by a litter crisis that is overwhelming authorities and communities and hindering the country's sustainable development goals. The coastal environment and communities of the southern states of Kerala and Tamil Nadu are particularly vulnerable to the impacts of climate change. While these state governments and authorities are stepping up efforts to improve the management of their coastal zones, the scale and severity of these issues are mounting. Here we review the combined effects of climate change and marine litter pollution in Southern India, focusing on the Gulf of Mannar Reserve in Tamil Nadu and the Malabar Coast in Kerala. Finally, we discuss effective management options that could help improve resilience and sustainability.

Marine litter and climate change: Inextricably connected threats to the world's oceans.

The global issues of climate change and marine litter are interlinked and understanding these connections is key to managing their combined risks to marine biodiversity and ultimately society. For example, fossil fuel-based plastics cause direct emissions of greenhouse gases and therefore are an important contributing factor to climate change, while other impacts of plastics can manifest as alterations in key species and habitats in coastal and marine environments. Marine litter is acknowledged as a threat multiplier that acts with other stressors such as climate change to cause far greater damage than if they occurred in isolation. On the other hand, while climate change can lead to increased inputs of litter into the marine environment, the presence of marine litter can also undermine the climate resilience of marine ecosystems. There is increasing evidence that that climate change and marine litter are inextricably linked, although these interactions and the resulting effects vary widely across oceanic regions and depend on the particular characteristics of specific marine environments. Ecosystem resilience approaches, that integrate climate change with other local stressors, offer a suitable framework to incorporate the consideration of marine litter where that is deemed to be a risk, and to steer, coordinate and prioritise research and monitoring, as well as management, policy, planning and action to effectively tackle the combined risks and impacts from climate change and marine litter.

Pollution in the Arctic Ocean: An overview of multiple pressures and implications for ecosystem services.

The Arctic is undergoing unprecedented change. Observations and models demonstrate significant perturbations to the physical and biological systems. Arctic species and ecosystems, particularly in the marine environment, are subject to a wide range of pressures from human activities, including exposure to a complex mixture of pollutants, climate change and fishing activity. These pressures affect the ecosystem services that the Arctic provides. Current international policies are attempting to support sustainable exploitation of Arctic resources with a view to balancing human wellbeing and environmental protection. However, assessments of the potential combined impacts of human activities are limited by data, particularly related to pollutants, a limited understanding of physical and biological processes, and single policies that are limited to ecosystem-level actions. This manuscript considers how, when combined, a suite of existing tools can be used to assess the impacts of pollutants in combination with other anthropogenic pressures on Arctic ecosystems, and on the services that these ecosystems provide. Recommendations are made for the advancement of targeted Arctic research to inform environmental practices and regulatory decisions.

Communicating marine climate change impacts in the Caribbean and Pacific regions.

The scientific literature on marine and coastal climate change has proliferated in recent decades. Translating and communicating this evidence in a timely, and accessible manner, is critical to support adaptation, but little is being done to summarise the latest science for decision makers. For Small Island Developing States (SIDS), which are highly vulnerable to marine and coastal climate change impacts, there is an urgent need to make the latest science readily available to inform national policy, leverage climate funding and highlight their vulnerability for international reports and climate negotiations. Climate change report cards are a proven successful way of presenting climate change information in an easily accessible and informative manner. Here we compare the development of marine climate change report cards for Caribbean and Pacific Commonwealth SIDS as a means of translating the latest science for decision makers. Regional engagement, priority issues and lessons learnt in these regions are compared, and future opportunities identified.

The impact of marine recreational fishing on key fish stocks in European waters.

Marine recreational fishing (MRF) has been shown to substantially contribute to fishing mortality of marine fish. However, European MRF catches are only quantified for a small number of stocks, so it is unclear whether a significant part of fishing mortality is excluded from stock assessments. This study estimated: (i) European MRF removals, which were defined as landings plus dead releases; and (ii) impact at stock level by comparing the percentage contribution to total removal by MRF and commercial fishing. As MRF data were limited for some European countries, catches were reconstructed using a mixture of average release proportions, average fish weights, and extrapolation using the catch per fisher of the nearest country providing catch estimates. Where catch reconstructions exceeded 50%, data were excluded from further analysis. Furthermore, as MRF survey methodology can be variable, semi-quantitative estimates of bias and error were calculated for each stock. Only 10 of the 20 stocks assessed in this study had sufficient MRF data for full reliable estimates. Percentage contribution to total removals (MRF + commercial removals) by MRF ranged between 2% for Atlantic mackerel in the North Sea and Skagerrak and 43% for Atlantic pollack in the Celtic Seas and English Channel. The biomass removed ranged between 297 (± 116) tonnes (Atlantic cod in the western English Channel and southern Celtic seas) and 4820 (± 1889) tonnes (Atlantic mackerel in the North Sea and Skagerrak), but the errors were substantial. Additionally, the bias in the estimated removals was low for most stocks, with some positive biases found. The present study indicates that removals by MRF can represent a high proportion of the total removals for some European marine fish stocks, so inclusion in stock assessments should be routine. To achieve this, regular surveys of MRF are required to collect data essential for stock assessments.

Historical Arctic Logbooks Provide Insights into Past Diets and Climatic Responses of Cod.

Gadus morhua (Atlantic cod) stocks in the Barents Sea are currently at levels not seen since the 1950s. Causes for the population increase last century, and understanding of whether such large numbers will be maintained in the future, are unclear. To explore this, we digitised and interrogated historical cod catch and diet datasets from the Barents Sea. Seventeen years of catch data and 12 years of prey data spanning 1930-1959 cover unexplored spatial and temporal ranges, and importantly capture the end of a previous warm period, when temperatures were similar to those currently being experienced. This study aimed to evaluate cod catch per unit effort and prey frequency in relation to spatial, temporal and environmental variables. There was substantial spatio-temporal heterogeneity in catches through the time series. The highest catches were generally in the 1930s and 1940s, although at some localities more cod were recorded late in the 1950s. Generalized Additive Models showed that environmental, spatial and temporal variables are all valuable descriptors of cod catches, with the highest occurring from 15-45°E longitude and 73-77°N latitude, at bottom temperatures between 2 and 4°C and at depths between 150 and 250 m. Cod diets were highly variable during the study period, with frequent changes in the relative frequencies of different prey species, particularly Mallotus villosus (capelin). Environmental variables were particularly good at describing the importance of capelin and Clupea harengus (herring) in the diet. These new analyses support existing knowledge about how the ecology of the region is controlled by climatic variability. When viewed in combination with more recent data, these historical relationships will be valuable in forecasting the future of Barents Sea fisheries, and in understanding how environments and ecosystems may respond.