Major declines in NE Atlantic plankton contrast with more stable populations in the rapidly warming North Sea.

Plankton form the base of marine food webs, making them important indicators of ecosystem status. Changes in the abundance of plankton functional groups, or lifeforms, can affect higher trophic levels and can indicate important shifts in ecosystem functioning. Here, we extend this knowledge by combining data from Continuous Plankton Recorder and fixed-point stations to provide the most comprehensive analysis of plankton time-series for the North-East Atlantic and North-West European shelf to date. We analysed 24 phytoplankton and zooplankton datasets from 15 research institutions to map 60-year abundance trends for 8 planktonic lifeforms. Most lifeforms decreased in abundance (e.g. dinoflagellates: -5 %, holoplankton: -7 % decade-1), except for meroplankton, which increased 12 % decade-1, reflecting widespread changes in large-scale and localised processes. K-means clustering of assessment units according to abundance trends revealed largely opposing trend direction between shelf and oceanic regions for most lifeforms, with North Sea areas characterised by increasing coastal abundance, while abundance decreased in North-East Atlantic areas. Individual taxa comprising each phytoplankton lifeform exhibited similar abundance trends, whereas taxa grouped within zooplankton lifeforms were more variable. These regional contrasts are counterintuitive, since the North Sea which has undergone major warming, changes in nutrients, and past fisheries perturbation has changed far less, from phytoplankton to fish larvae, as compared to the more slowly warming North-East Atlantic with lower nutrient supply and fishing pressure. This more remote oceanic region has shown a major and worrying decline in the traditional food web. Although the causal mechanisms remain unclear, declining abundance of key planktonic lifeforms in the North-East Atlantic, including diatoms and copepods, are a cause of major concern for the future of food webs and should provide a red flag to politicians and policymakers about the prioritisation of future management and adaptation measures required to ensure future sustainable use of the marine ecosystem.

Marine water quality of a densely populated Pacific atoll (Tarawa, Kiribati): Cumulative pressures and resulting impacts on ecosystem and human health.

The resilience of coastal ecosystems and communities to poor environmental and health outcomes is threatened by cumulative anthropogenic pressures. In Kiribati, a developing Pacific Island country where human activities are closely connected with the ocean, both people and environment are particularly vulnerable to coastal pollution. We present a survey of environmental and human health water quality parameters around urban South Tarawa, and an overview of their impacts on the semi-enclosed atoll. Tarawa has significant water quality issues and decisions to guide improvements are hindered by a persistent lack of appropriate and sufficient observations. Our snapshot assessment identifies highest risk locations related to chronic focused and diffuse pollution inputs, and where mixing and dilution with ocean water is restricted. We demonstrate the importance of monitoring in the context of rapidly changing pressures. Our recommendations are relevant to other atoll ecosystems where land-based activities and ocean health are tightly interlinked.

Baseline assessment of coastal water quality, in Vanuatu, South Pacific: Insights gained from in-situ sampling.

Nearshore deterioration of water quality in Pacific coastal waters is a growing problem, associated with increasing urban and industrial sewage discharges, and agricultural runoff. Published water quality studies in the Pacific region are limited in both number and scope, making it difficult to resolve the extent of the issue or quantify the variability of water quality across Pacific islands and countries. This study collected water quality measurements over three years in the coastal waters around the Island of Efate (Vanuatu) with majority of work carried out in Port Vila, its capital. Port Vila is the key urban centre for Vanuatu where the increasing population and pollution inputs are placing substantial pressure on the coastal environment. Highest concentrations of dissolved nutrients and suspended sediments were measured adjacent or near the urban drains that enter the coastal areas along the capital's seafront, highlighting many of the issues around anthropogenic inputs are linked to the increasing urbanisation in Port Vila Bay. We provide baseline data that explores variability of coastal water quality and these types of datasets for Pacific islands are a first step towards facilitating development of long-term monitoring programmes and informing coastal zone management decision making.

Lifeform indicators reveal large-scale shifts in plankton across the North-West European shelf.

Increasing direct human pressures on the marine environment, coupled with climate-driven changes, is a concern to marine ecosystems globally. This requires the development and monitoring of ecosystem indicators for effective management and adaptation planning. Plankton lifeforms (broad functional groups) are sensitive indicators of marine environmental change and can provide a simplified view of plankton biodiversity, building an understanding of change in lower trophic levels. Here, we visualize regional-scale multi-decadal trends in six key plankton lifeforms as well as their correlative relationships with sea surface temperature (SST). For the first time, we collate trends across multiple disparate surveys, comparing the spatially and temporally extensive Continuous Plankton Recorder (CPR) survey (offshore) with multiple long-term fixed station-based time-series (inshore) from around the UK coastline. These analyses of plankton lifeforms showed profound long-term changes, which were coherent across large spatial scales. For example, 'diatom' and 'meroplankton' lifeforms showed strong alignment between surveys and coherent regional-scale trends, with the 1998-2017 decadal average abundance of meroplankton being 2.3 times that of 1958-1967 for CPR samples in the North Sea. This major, shelf-wide increase in meroplankton correlated with increasing SSTs, and contrasted with a general decrease in holoplankton (dominated by small copepods), indicating a changing balance of benthic and pelagic fauna. Likewise, inshore-offshore gradients in dinoflagellate trends, with contemporary increases inshore contrasting with multi-decadal decreases offshore (approx. 75% lower decadal mean abundance), urgently require the identification of causal mechanisms. Our lifeform approach allows the collation of many different data types and time-series across the NW European shelf, providing a crucial evidence base for informing ecosystem-based management, and the development of regional adaptation plans.