Plymouth Marine Laboratory

Society relies on intact marine ecosystems for ecosystem services such as nutrition, livelihoods, health and well‐being. Yet, to obtain these benefits, we carry out activities, introducing pressures to ecosystems, damaging and degrading habitats and reducing their capacity to optimally provide ecosystem services. Biodiversity and ecosystem services are consequently being lost globally but impact chains from these activities are poorly understood, especially in tropical marine ecosystems. We identified for the first time impact chains linking activities with pressures they introduce in five tropical coastal and marine habitats, specifically through application in four Southeast Asian case study sites. Using expert elicitation based on existing evidence, we weighted each impact chain according to pressure extent, frequency and persistence, and habitat resistance and resilience. Assigning each impact chain an impact risk score allowed identification of activities and pressures introducing most risk, and habitats most under threat. Of 26 activities we considered, we found fishing activities, specifically trawling, gill nets and seine nets introduce most risk, along with tourism and recreation. Litter and pollution were among the greatest pressures on habitats, with coral reefs being most vulnerable overall. Destructive fishing practices were associated with physical pressures like abrasion, smothering and siltation and total habitat loss, while tourism activities were associated with organic enrichment, litter and pollution. The risk levels depended on the habitat and on local case study context. Synthesis and applications: A contextualised risk‐based approach can help to prioritise sustainability issues for management in data‐poor regions by making use of a range of knowledge types from local experts to broader scientific knowledge. A multisectoral, and ecosystem‐based risk assessment can help decision makers to consider trade‐offs in marine resource management and highlight priorities transparently, where coordination of multiple administrative organisations, sectors and local actors is required to meet multiple sustainability objectives. Physical pressures from fishing activities combined with pollution from tourism indicate effective management requires a multi‐use zoning approach that not only considers impacts at the site of activities but also integrates regional coordination to tackle dispersive pressures from pollution or sediment disturbance that occur at a distance from the source.

The cell size of picophytoplankton populations affects their ecology and biogeochemical role, but how different environmental drivers control its variability is still not well understood. To gain insight into the role of temperature and nutrient availability as determinants of picophytoplankton population mean cell size, we carried out five microcosm experiments across the Atlantic Ocean (45°N-27°S) in which surface plankton assemblages were incubated under all combinations of three temperatures (in situ, 3 °C cooling and 3 °C warming) and two nutrient levels (unamended and addition of nitrogen and phosphorus). The overall range of variability in cell volume was 5-fold for Prochlorococcus, 8-fold for Synechococcus and 6-fold for the picoeukaryotes. We observed, in all the treatments and in the control, a consistent trend toward larger mean cell sizes over time for both Prochlorococcus and Synechococcus, which was likely the result of sample confinement. Changes in temperature and nutrient status alone did not cause clear changes in cell size, relative to the control, but the combination of warming and nutrient addition resulted in an increase in Prochlorococcus and Synechococcus cell size. The largest increases in cell volume were associated with slow or negative population net growth rates. Our results emphasize the importance of considering changes in biovolume to obtain accurate estimates of picophytoplankton biomass and suggest that the inverse relationship between growth rate and population mean cell size may be a general pattern in marine phytoplankton.

The latitude of the north wall of the Gulf Stream along the US seaboard has been recorded in the Gulf Stream North Wall (GSNW) Index for over half a century from 1966 to 2023. The first half of this series shows the position fluctuating about a steady northward drift but this drift ceased in the second half. The same abrupt change is seen in the data of Joyce et al. from 200m depth which begin back to 1954 and extend further east. Monthly values of the GSNW index have been used to estimate how the occurrence of extreme meanders has changed over the 58-year period. Southern extremes follow the same pattern of change as the annual average positions but northern extremes show no northward drift. It may be the Gulf Stream has approached its northern limit. The transition has accompanied the rise in the number of warm-core rings observed by Gangopadhyay and colleagues and this may have been part of the process preventing further northward drift.

Plastic pollution is now considered globally ubiquitous, irreversible, and a planetary boundary threat. Solutions are urgently needed but their development and application are hampered by the complexity and scale of the issue. System dynamics is a technique used to understand complex behaviours of systems through model building and is useful for conceptualising the relationships between various interacting, dynamic factors, and identifying potential intervention points within the system where specific policies or innovations might have the greatest impact or meet with the greatest resistance. Here, twenty-five participants (all scientific researchers of various career stages, disciplines and nationalities working on plastic pollution) completed a series of exercises through an interactive, iterative group model building exercise during a one-day workshop. The process culminated in the generation of a causal loop diagram, based on participants' perspectives, illustrating the dynamic factors relating to the constraints and enablers of solutions to plastic pollution. A total of 18 factors and seven feedback loops were identified. Key factors influencing the system were Effective legislation, Funding, Public education and awareness, Behaviour change, Innovation, and Effective waste management. Our findings highlight that there is no single driver, or 'silver bullet', for resolving this complex issue and that a holistic approach should be adopted to create effective and systemic change.

The ocean annually absorbs about a quarter of all anthropogenic carbon dioxide (CO2) emissions. Global estimates of air–sea CO2 fluxes are typically based on bulk measurements of CO2 in air and seawater and neglect the effects of vertical temperature gradients near the ocean surface. Theoretical and laboratory observations indicate that these gradients alter air–sea CO2 fluxes, because the air–sea CO2 concentration difference is highly temperature sensitive. However, in situ field evidence supporting their effect is so far lacking. Here we present independent direct air–sea CO2 fluxes alongside indirect bulk fluxes collected along repeat transects in the Atlantic Ocean (50° N to 50° S) in 2018 and 2019. We find that accounting for vertical temperature gradients reduces the difference between direct and indirect fluxes from 0.19 mmol m⁻² d⁻¹ to 0.08 mmol m⁻² d⁻¹ (N = 148). This implies an increase in the Atlantic CO2 sink of ~0.03 PgC yr⁻¹ (~7% of the Atlantic Ocean sink). These field results validate theoretical, modelling and observational-based efforts, all of which predicted that accounting for near-surface temperature gradients would increase estimates of global ocean CO2 uptake. Accounting for this increased ocean uptake will probably require some revision to how global carbon budgets are quantified.

Background Marine sediments represent one of the planet’s largest carbon stores. Bottom trawl fisheries constitute the most widespread physical disturbance to seabed habitats, which exert a large influence over the oceanic carbon dioxide (CO 2 ) sink. Recent research has sparked concern that seabed disturbance from trawling can therefore turn marine sediments into a large source of CO 2 , but the calculations involved carry a high degree of uncertainty. This is primarily due to a lack of quantitative understanding of how trawling mixes and resuspends sediments, how it alters bioturbation, bioirrigation, and oxygenation rates, and how these processes translate into carbon fluxes into or out of sediments. Methods The primary question addressed by this review protocol is: how does mobile bottom fishing affect benthic carbon processing and storage? This question will be split into the following secondary questions: what is the effect of mobile bottom fishing on: (i) the amount and type of carbon found in benthic sediments; (ii) the magnitude and direction of benthic-pelagic carbon fluxes; (iii) the biogeochemical, biological, and physical parameters that control the fate of benthic carbon; and (iv) the biogeochemical, biological, and physical parameters that control the fate of resuspended carbon. Literature searches will be conducted in Web of Science, SCOPUS, PROQUEST, and a range of grey and specialist sources. An initial scoping search in Web of Science informed the final search string, which has been formulated according to Population Intervention Comparator Outcome (PICO) principles. Eligible studies must contain data concerning a change in a population of interest caused by mobile bottom fishing. Eligible study designs are Before and After, Control and Impact, and Gradient studies. Studies included at full-text screening will be critically appraised, and study findings will be extracted.Extracted data will be stored in an Excel spreadsheet. Results will be reported in narrative and quantitative syntheses using a variety of visual tools including forest plots. Meta-analysis will be conducted where sufficient data exists.

Synthesising knowledge on the health of marine ecosystems and the human activities is crucial to informing holistic marine management. In many coastal states, however, research is conducted in an ad hoc manner and rarely compiled into accessible repositories making it challenging for marine managers to identify knowledge gaps when allocating resources. Here we conduct a structured review of existing literature to identify the current state of marine and coastal knowledge in the Isles of Scilly, an oceanic archipelago in the UK. The archipelago's marine flora and fauna are biogeographically unique in the Northeast Atlantic, with a distinct mosaic of warm and cold temperate habitats and species and are also considered a rare example of a near pristine marine environment in the otherwise highly degraded Northeast Atlantic Ocean. We found 150 sources relating to the marine biodiversity and relevant human activities in the Isles of Scilly with increasing diversification of research topics in recent years. Sources however remain dominated by specific taxa and habitats, suggesting the Isles of Scilly would particularly benefit from future research into: (1) anthropogenic impacts associated with warming waters and intense seasonal vessel activity; (2) development of repeatable survey protocols that can underpin long-term, ecosystem-based monitoring and management (notably for reef and sediment habitats and the European spiny lobster); and (3) data gaps associated with marine teleost fish and elasmobranch communities including identifying core habitat. This review can therefore act as a baseline biological synthesis for the region and importantly, can inform future research priorities.

Arctic biodiversity is under threat from both climate induced environmental change and anthropogenic activity. However, the rapid rate of change and the challenging conditions for studying Arctic environments mean that many research questions must be answered before we can strategically allocate resources for management. Addressing threats to biodiversity in the Arctic is further complicated by the region's complex geopolitics, as eight countries claim jurisdiction over the area, with multiple local considerations such as Indigenous sovereignty and resource rights. Here, we identify research priorities to serve as a starting point for addressing the most pressing threats to Arctic biodiversity. We began by collecting pressing research questions about Arctic biodiversity, thematizing them as either threats or actions, and then categorizing them further into 18 groups. Then, drawing on cross-disciplinary and global expertise of professionals in Arctic science, management, and policy, we considered the barriers to answering these questions and proposed potential solutions that could be implemented if barriers were overcome. Overall, our horizon scan provides an expert assessment of threats (e.g., species’ responses to climate change) and actions (e.g., a lack of fundamental information regarding Arctic biodiversity) needing attention and is intended to guide future conservation action within the Arctic.

of key findings. Polystyrene and wood were selectively colonized by antimicrobial-resistant (AMR) bacteria, while bio-beads selected for potential Escherichia coli pathogens and surface weathering did not significantly influence AMR colonization. Created in BioRender. Stevenson, E. (2024) BioRender.com/r90g504

Ecological theory and empirical research show that both direct lethal effects and indirect non-lethal effects can structure the composition of communities. While the direct effects of grazers on marine phytoplankton communities are well studied, their indirect effects are still poorly understood. Direct and indirect effects are inherently difficult to disentangle in plankton food webs. In this study we evaluate the indirect effects of copepod grazers on community function and structure using isolated chemical alarm signals, copepodamides. We expose intact summer and spring communities to direct grazing from copepods, or to chemical alarm cues without the presence of grazers in controlled experiments. The effects of direct grazing on ecosystem function were moderate in both experiments as indicated by levels of chlorophyll and primary production. Indirect and direct effects resulted in changes in the composition of both the eukaryote and prokaryote communities as shown by metabarcoding of 18S and 16S rRNA. Size structure analysis suggests that direct grazing and copepodamide exposure both favoured smaller organisms (< 10–15 μm) corroborating the size-structuring effect of copepod grazers. We conclude that the well-established effect of copepods on phytoplankton communities results from a combination of direct and indirect effects. This is a first attempt to isolate indirect effects of copepods on community structure and the results suggest that a full mechanistic understanding of the structuring effect of copepods will require insights to both direct and indirect effects of consumers as demonstrated for other ecosystems components.

The carbon sequestration potential of open-ocean pelagic ecosystems is vastly under-reported compared to coastal vegetation ‘blue carbon’ systems. Here we show that just a single pelagic harvested species, Antarctic krill, sequesters a similar amount of carbon through its sinking faecal pellets as marshes, mangroves and seagrass. Due to their massive population biomass, fast-sinking faecal pellets and the modest depths that pellets need to reach to achieve sequestration (mean is 381 m), Antarctic krill faecal pellets sequester 20 MtC per productive season (spring to early Autumn). This is equates USD$ 4 − 46 billion depending on the price of carbon, with krill pellet carbon stored for at least 100 years and with some reaching as far as the North Pacific. Antarctic krill are being impacted by rapid polar climate change and an expanding fishery, thus krill populations and their habitat warrant protection to preserve this valuable carbon sink.

The influence of mesoscale eddies on chlorophyll (Chl) has received significant attention due to Chl being a proxy for phytoplankton, which plays a crucial role in marine ecosystems. Solely relying on the analysis of satellite-observed Chl poses challenges in determining the phytoplankton response to mesoscale eddies. To address this, our study takes a collaborative approach, utilizing satellite-derived sea surface temperature anomalies (SSTA) and chlorophyll anomalies (CHLA) to comprehensively investigate the dynamical-biological processes associated with eddies in the subtropical and mid-latitude North Atlantic. In the subtropics, the patterns in CHLA and SSTA predominantly exhibit a dipole nature, with the dipole component providing more than 70% of the explained variance (EV). This suggests that eddy stirring is the dominant mechanism driving the observed anomaly patterns. Conversely, in the mid-latitudes, the monopole components (TM) explain more than 60% of the EV, implying a more influential role for eddy trapping and vertical modulations. The signs of the TM of eddy SSTA persist throughout their lifetime, being consistent with the lowering (raising) of isopycnals within AEs (CEs). However, the subtropical CHLA response is higher in AEs than CEs, indicating additional factors, such as eddy-induced Ekman pumping and/or mixing to a deeper level may be important. This finding is also corroborated by subsurface observations from Argo floats. At mid-latitudes, there is a clear inverse correspondence between the CHLA and mixed layer depth. In contrast, no significant correlation is observed in the subtropics, except during winter when a positive relationship emerges. These patterns suggest that phytoplankton exhibit highly diverse responses to the physical dynamics associated with eddies. Our work offers a method to estimate eddy dynamical-biological impacts on phytoplankton using satellite products, compensating for the limitations of in-situ observations. It also reveals potential contributions to marine primary production, global carbon cycles, and the development of biogeochemical models.

Understanding processes driving air-sea gas transfer and being able to model both its mean and variability are critical for studies of climate and carbon cycle. The air-sea gas transfer velocity (K660) is almost universally parameterized as a function of wind speed in large scale models – an oversimplification that buries the mechanisms controlling K660 and neglects much natural variability. Sea state has long been speculated to affect gas transfer, but consistent relationships from in situ observations have been elusive. Here, applying a Machine Learning technique to an updated compilation of shipboard direct observations of the CO2 transfer velocity (KCO2,660), we show that the inclusion of significant wave height improves the model simulation of KCO2,660, while parameters such as wave age, wave steepness, and swell-wind directional difference have little influence on KCO2,660. Wind history is found to be important, as in high seas KCO2,660 during periods of falling winds exceed periods of rising winds by ∼20% in the mean. This hysteresis in KCO2,660 is consistent with the development of waves and increase in whitecap coverage as the seas mature. A similar hysteresis is absent from the transfer of a more soluble gas, confirming that the sea state dependence in KCO2,660 is primarily due to bubble-mediated gas transfer upon wave breaking. We propose a new parameterization of KCO2,660 as a function of wind stress and significant wave height, which resemble observed KCO2,660 both in the mean and on short timescales.