EPA - Ireland's Environment, An Integrated Assessment - 2020

Chapter 8: The Marine Environment Marine Litter Marine litter, including plastics and microplastics can be found throughout our marine waters; more research to assess their impact on marine life, food webs and human health is required. Public awareness of the impacts of marine litter and, including, microplastics on marine ecosystems and life forms has been growing over the last few years. Marine litter, including microplastics have been recorded in every part of the world’s oceans (Lusher, 2015), on our beaches, and in many marine organisms. The EU Commission’s Joint Research Council Technical Report on the Harm Caused by Marine Litter (Werner et al., 2016) concluded that, ‘although the extent of harm of marine litter to ecosystems has yet to be determined there is evidence of harm to individuals or groups of marine animals or plants’. Ingestion may also provide a pathway for the transport of harmful chemicals into marine food webs. These harmful chemicals include persistent organic pollutants such as polychlorinated biphenyls (PCBs) which can bioaccumulate in apex predators such as killer whales (Schlingermann et al. , 2019). Laboratory tests suggest that high levels of exposure to harmful chemicals under specific circumstances can result in physical and chemical toxicity (SAPEA, 2019). Chapter 14 provides further details on plastic pollution. Nutrient Enrichment While eutrophication is currently not a major concern for coastal and marine waters, future warming due to climate change could increase the impacts of nutrient enrichment. Excess nutrients in coastal and offshore marine areas can stimulate the growth of aquatic plant life and result in the depletion of oxygen, leading to eutrophication. This reduction in oxygen can have negative knock-on effects for fish and marine fauna living in these areas and can result in the loss of sensitive aquatic species. The build-up of phytoplankton blooms and large green seaweed in coastal areas can also be detrimental for tourism, recreation and fisheries. In Ireland, eutrophication increases with proximity to human activity and land-based sources of nutrients (see Chapter 7 for further details). While our estuaries are affected by eutrophication, our coastal regions are healthier, and no eutrophication issues have been found in outer marine areas. Coastal and marine systems benefit from their proximity to the Atlantic Ocean, which can dilute nutrients and decrease contaminant loads originating from land-based sources. However, in coastal and marine systems eutrophication impacts could be exacerbated by warmer growth conditions for phytoplankton and seaweed. A recent analysis of long-term monitoring data indicates that, after nutrient concentrations, temperature is the factor that most influences the health of the phytoplankton community in Irish transitional and coastal waters (Ní Longphuirt et al. , 2019). Similarly, global warming scenarios are expected to have an impact on green tides (opportunistic algal blooms) in Irish coastal areas if nutrient conditions are not improved (Bermajo et al. , 2019). Consideration of the combined impact of pressures such as climate change and eutrophication is essential to understand the future health of marine ecosystems. 203