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Thermal resistance of the coral-zooxanthellae symbiosis has been associated with chronic photoinhibition, increased antioxidant activity and protein repair involving high demands of nitrogen and energy. While the relative importance of heterotrophy as a source of nutrients and energy for cnidarian hosts, and as a means of nitrogen acquisition for their zooxanthellae, is well documented, the effect of feeding on the thermal sensitivity of the symbiotic association has been so far overlooked. Here we examine the effect of zooplankton feeding versus starvation on the bleaching susceptibility and photosynthetic activity of photosystem II (PSII) of zooxanthellae in the scleractinian coral Stylophora pistillata in response to thermal stress (daily temperature rises of 2-3 degrees C) over 10 days, employing pulse-amplitude-modulated chlorophyll fluorometry. Fed and starved corals displayed a decrease in daily maximum potential quantum yield (F (v)/F (m)) of PSII, effective quantum yield (F/F (m)') and relative electron transport rates over the course of 10 days. However after 10 days of exposure to elevated temperature, F (v)/F (m) of fed corals was still 50-70% higher than F (v)/F (m) of starved corals. Starved corals showed strong signs of chronic photoinhibition, which was reflected in a significant decline in nocturnal recovery rates of PSII relative to fed corals. This was paralleled by the progressive inability to dissipate excess excitation energy via non-photochemical quenching (NPQ). After 10 days, NPQ of starved corals had decreased by about 80% relative to fed corals. Feeding treatment had no significant effect on chlorophyll a and c (2) concentrations and zooxanthellae densities, but the mitotic indices were significantly lower in starved than in fed corals. Collectively the results indicate that exogenous food may reduce the photophysiological damage of zooxanthellae that typically leads to bleaching and could therefore play an important role in mediating the thermal resistance of some corals.

A risk framework has been developed to examine the influence of climate change on disease emergence in the United Kingdom. The fish immune response and the replication of pathogens are often correlated with water temperature, which manifest as temperature ranges for infection and clinical diseases. These data are reviewed for the major endemic and exotic disease threats to freshwater fish. Increasing water temperatures will shift the balance in favour of either the host or pathogen, changing the frequency and distribution of disease. A number of endemic diseases of salmonids (e.g. enteric red mouth, furunculosis, proliferative kidney disease and white spot) will become more prevalent and difficult to control as water temperatures increase. Outbreaks of koi herpesvirus in carp fisheries are likely to occur over a longer period each summer. Climate change also alters the threat level associated with exotic pathogens. The risk of viral haemorrhagic septicaemia (VHSV), infectious haematopoietic necrosis virus (IHNV) and spring viraemia of carp virus (SVCV) declines as infection generally only establishes when water temperatures are less than 14°C for VHSV and IHNV and 17°C for SCVC. The risk of establishment of other exotic pathogens (epizootic haematopoietic necrosis and epizootic ulcerative syndrome) increases. The spread of Lactococcus garvieae northwards in Europe is likely to continue, and thus is more likely to be both introduced and become established. Measures to reduce the threat of exotic pathogens need to be revised to account for the changing exotic diseases threat. Increasing water temperatures and the negative effects of extreme weather events (e.g. storms) are likely to alter the freshwater environment adversely for both wild and farmed salmonid populations, increasing their susceptibility to disease and the likelihood of disease emergence. For wild populations, surveillance and risk mitigation need to be focused on locations where disease emergence, as a result of climate change, is most likely.

Coral reefs in the tropical Pacific region are exposed to a range of anthropogenic local pressures. Climate change is exacerbating local impacts, causing unprecedented declines in coral reef habitats and bringing negative socio-economic consequences to Pacific communities who depend heavily on coral reefs for food, income and livelihoods. Continued increases in greenhouse gas emissions will drive future climate change, which will accelerate coral reef degradation. Traditional systems of resource governance in Pacific island nations provide a foundation to address local pressures and build reef resilience to climate change. Management and adaptation options should build on the regional diversity of governance systems and traditional knowledge to support community-based initiatives and cross-sectoral cooperation to address local pressures and minimize climate change impacts. Such an inclusive approach will offer enhanced opportunities to develop and implement transformative adaptation solutions, particularly in remote and regional areas where centralized management does not extend.

Among the various quality elements which the Water Framework Directive requires should be monitored are macroalgae. One aspect of these is the presence, in transitional waters particularly, of large blooms of opportunistic macroalgae, such as Ulva and Enteromorpha. Within the United Kingdom (UK) and Republic of Ireland (RoI) there are currently no set ecological quality objectives or standards for macroalgae. Nor are there standard methods for monitoring macroalgal blooms, although various combinations of aerial photography, remote sensing and measurements on the ground are used. This paper attempts to set a logical framework for the prioritisation of sites for monitoring, the development of a tiered monitoring procedure and the derivation of thresholds for classification. Draft threshold limits for percentage cover and biomass of macroalgae have been derived from the literature. The importance of secondary effects and physico-chemical parameters is discussed.

Abstract Under increasing nutrient loading, shallow lakes may shift from a state of clear water dominated by submerged macrophytes to a turbid state dominated by phytoplankton or a shaded state dominated by floating macrophytes. How such regime shifts mediate the relationship between taxonomic and functional diversities (FD) and lake multifunctionality is poorly understood. We employed a detailed database describing a shallow lake over a 12‐year period during which the lake has displayed all the three states (clear, turbid and shaded) to investigate how species richness, FD of fish and zooplankton, ecosystem multifunctionality and five individual ecosystem functions (nitrogen and phosphorus concentrations, standing fish biomass, algae production and light availability) differ among states. We also evaluated how the relationship between biodiversity (species richness and FD) and multifunctionality is affected by regime shifts. We showed that species richness and the FD of fish and zooplankton were highest during the clear state. The clear state also maintained the highest values of multifunctionality as well as standing fish biomass production, algae biomass and light availability, whereas the turbid and shaded states had higher nutrient concentrations. Functional diversity was the best predictor of multifunctionality. The relationship between FD and multifunctionality was strongly positive during the clear state, but such relationship became flatter after the shift to the turbid or shaded state. Our findings illustrate that focusing on functional traits may provide a more mechanistic understanding of how regime shifts affect biodiversity and the consequences for ecosystem functioning. Regime shifts towards a turbid or shaded state negatively affect the taxonomic diversity and FD of fish and zooplankton, which in turn impairs the multifunctionality of shallow lakes.

AbstractResting egg production is considered the most common form of dormancy in aquatic invertebrates. Given that many taxa at least partially terminate resting egg state using environmental cues, knowledge on environmental drivers of hatching success is important, particularly within the context of climate change and environmental degradation. Fairy shrimp (anostracans) are temporary wetland specialists that are reliant on resting egg production for population persistence. Temporary wetlands are common in many arid regions projected to experience increases in temperature, and in areas often compromised by human‐mediated activities. In this study, we assessed the combined effects of light and temperature on the hatching success of Streptocephalus cafer (Anostraca) dormant eggs from temporary wetlands in an arid environment. Both temperature and light altered hatching success, with emergent effects evident. Light caused a significant threefold increase in hatching success overall, while temperature effects were non‐linear, with hatching optimised at 27°C, and especially under light conditions. These results are discussed within the context of shifting climates and disturbances to temporary wetland ecosystems.

This work analyses a 30 year water quality data set collated from chemical analyses of Kuwait's marine waters. Spatial patterns across six sites in Kuwait Bay and seven sites located in the Arabian Gulf are explored and discussed in terms of the changing influences associated with point and diffuse sources. Statistical modelling demonstrated significant increases for dissolved nutrients over the time period. Kuwait marine waters have been subject to inputs from urban development, untreated sewage discharges and decreasing river flow from the Shatt al-Arab River. Chlorophyll biomass showed a small but significant reduction; the high sewage content of the coastal waters from sewage discharges likely favouring the presence of smaller phytoplankton taxa. This detailed assessment of temporal data of the impacts of sewage inputs into Kuwait's coastal waters establishes an important baseline permitting future assessments to be made as sewage is upgraded, and the river continues to be extracted upstream.

SummaryThe recent emergence of Vibrio infections at high latitudes represents a clear human health risk attributable to climate change. Here, we investigate the population dynamics of three Vibrio species: Vibrio parahaemolyticus, Vibrio vulnificus and Vibrio cholerae within a British coastal estuarine site, with contrasting salinity and temperature regimes during an intense heatwave event. Water samples were collected weekly through the summer of 2018 and 2019 and filtered using membrane filtration and subsequently grown on selective media. Suspected vibrios were confirmed using a conventional species‐specific PCR assay and further analysed for potential pathogenic markers. Results showed that Vibrio parahaemolyticus, Vibrio vulnificus and Vibrio cholerae were present at high concentrations throughout both years, with their populations at substantially greater abundances corresponding to conditions of higher water temperatures during the heatwave of 2018 and at lower salinity sites, which is comparable to the results of previous studies. A subset of strains isolated during the extreme heatwave event in 2018 (46 Vibrio parahaemolyticus, 11 Vibrio cholerae and 4 Vibrio vulnificus) were genomically sequenced. Analysis of these 63 sequenced strains revealed a broad phenotypic and genomic diversity of strains circulating in the environment. An analysis of pathogenicity attributes identified a broad array of virulence genes across all three species, including a variety of genes associated with human disease. This study highlights the importance of the need for an increased Vibrio spp. surveillance system in temperate regions and the potential impact warming events such as heatwaves may have on the abundance of potentially pathogenic bacteria in the environment.

It is premature to sell carbon offsets from ocean iron fertilization unless research provides the scientific foundation to evaluate risks and benefits.

Biodiversity indicators provide a vital window on the state of the planet, guiding policy development and management. The most widely adopted marine indicator is mean trophic level (MTL) from catches, intended to detect shifts from high-trophic-level predators to low-trophic-level invertebrates and plankton-feeders. This indicator underpins reported trends in human impacts, declining when predators collapse ("fishing down marine food webs") and when low-trophic-level fisheries expand ("fishing through marine food webs"). The assumption is that catch MTL measures changes in ecosystem MTL and biodiversity. Here we combine model predictions with global assessments of MTL from catches, trawl surveys and fisheries stock assessments and find that catch MTL does not reliably predict changes in marine ecosystems. Instead, catch MTL trends often diverge from ecosystem MTL trends obtained from surveys and assessments. In contrast to previous findings of rapid declines in catch MTL, we observe recent increases in catch, survey and assessment MTL. However, catches from most trophic levels are rising, which can intensify fishery collapses even when MTL trends are stable or increasing. To detect fishing impacts on marine biodiversity, we recommend greater efforts to measure true abundance trends for marine species, especially those most vulnerable to fishing.