Clare Woulds

Priority water research questions as determined by UK practitioners and policy makers

Several recent studies have emphasised the need for a more integrated process in which researchers, policy makers and practitioners interact to identify research priorities. This paper discusses such a process with respect to the UK water sector, detailing how questions were developed through inter-disciplinary collaboration using online questionnaires and a stakeholder workshop. The paper details the 94 key questions arising, and provides commentary on their scale and scope. Prioritization voting divided the nine research themes into three categories: (1) extreme events (primarily flooding), valuing freshwater services, and water supply, treatment and distribution [each >150/1109 votes]; (2) freshwater pollution and integrated catchment management [100-150 votes] and; (3) freshwater biodiversity, water industry governance, understanding and managing demand and communicating water research [50-100 votes]. The biggest demand was for research to improve understanding of intervention impacts in the water environment, while a need for improved understanding of basic processes was also clearly expressed, particularly with respect to impacts of pollution and aquatic ecosystems. Questions that addressed aspects of appraisal, particularly incorporation of ecological service values into decision making, were also strongly represented. The findings revealed that sustainability has entered the lexicon of the UK water sector, but much remains to be done to embed the concept operationally, with key sustainability issues such as resilience and interaction with related key sectors, such as energy and agriculture, relatively poorly addressed. However, the exercise also revealed that a necessary condition for sustainable development, effective communication between scientists, practitioners and policy makers, already appears to be relatively well established in the UK water sector.

The long-term fate of permafrost peatlands under rapid climate warming.

Permafrost peatlands contain globally important amounts of soil organic carbon, owing to cold conditions which suppress anaerobic decomposition. However, climate warming and permafrost thaw threaten the stability of this carbon store. The ultimate fate of permafrost peatlands and their carbon stores is unclear because of complex feedbacks between peat accumulation, hydrology and vegetation. Field monitoring campaigns only span the last few decades and therefore provide an incomplete picture of permafrost peatland response to recent rapid warming. Here we use a high-resolution palaeoecological approach to understand the longer-term response of peatlands in contrasting states of permafrost degradation to recent rapid warming. At all sites we identify a drying trend until the late-twentieth century; however, two sites subsequently experienced a rapid shift to wetter conditions as permafrost thawed in response to climatic warming, culminating in collapse of the peat domes. Commonalities between study sites lead us to propose a five-phase model for permafrost peatland response to climatic warming. This model suggests a shared ecohydrological trajectory towards a common end point: inundated Arctic fen. Although carbon accumulation is rapid in such sites, saturated soil conditions are likely to cause elevated methane emissions that have implications for climate-feedback mechanisms.

Macrofaunal Ecology of Sedimented Hydrothermal Vents in the Bransfield Strait, Antarctica

Sedimented hydrothermal vents, where hot, mineral-rich water flows through sediment, are poorly understood globally, both in their distribution and the ecology of individual vent fields. We explored macrofaunal community ecology at a sediment-hosted hydrothermal vent in the Southern Ocean. This is the first such study of these ecosystems outside of the Pacific and the furthest south (62˚S) of any vent system studied. Sedimentary fauna were sampled in four areas of the Bransfield Strait (Southern Ocean), with the aim of contrasting community structure between vent and non-vent sites. Macrofaunal assemblages were clearly distinct between vent and non-vent sites, and diversity, richness and density declined towards maximum hydrothermal activity. This variation is in contrast to observations from similar systems in the Pacific and demonstrates the influence of factors other than chemosynthetic primary productivity in structuring infauna at deep-sea vent communities. Vent endemic fauna had limited abundance and were represented by a single siboglinid species at hydrothermally active areas, meaning that that the majority of local biota were those also found in other areas. Several taxa occupied all sampling stations but there were large differences in their relative abundances, suggesting communities were structured by niche variation rather than dispersal ability.

Geochemistry, faunal composition and trophic structure in reducing sediments on the southwest South Georgia margin

Despite a number of studies in areas of focused methane seepage, the extent of transitional sediments of more diffuse methane seepage, and their influence upon biological communities is poorly understood. We investigated an area of reducing sediments with elevated levels of methane on the South Georgia margin around 250 m depth and report data from a series of geochemical and biological analyses. Here, the geochemical signatures were consistent with weak methane seepage and the role of sub-surface methane consumption was clearly very important, preventing gas emissions into bottom waters. As a result, the contribution of methane-derived carbon to the microbial and metazoan food webs was very limited, although sulfur isotopic signatures indicated a wider range of dietary contributions than was apparent from carbon isotope ratios. Macrofaunal assemblages had high dominance and were indicative of reducing sediments, with many taxa common to other similar environments and no seep-endemic fauna, indicating transitional assemblages. Also similar to other cold seep areas, there were samples of authigenic carbonate, but rather than occurring as pavements or sedimentary concretions, these carbonates were restricted to patches on the shells of Axinulus antarcticus (Bivalvia, Thyasiridae), which is suggestive of microbe–metazoan interactions.

Rates and Regulation of Microbially Mediated Aerobic and Anaerobic Carbon Oxidation Reactions in Continental Margin Sediments from the Northeastern Arabian Sea (Pakistan Margin)

Rates of microbially mediated C oxidation were measured at sites above, within, and below the oxygen minimum zone (OMZ) on the Pakistan margin of the Arabian Sea, before and after the southwest monsoon, with the goal of assessing how low bottom water O 2 concentration affects microbial C oxidation processes. Rates of C oxidation coupled to aerobic and anaerobic processes were measured at five depths: 140 m (seasonally hypoxic), 300 m (OMZ core), 940 m (OMZ transition), 1200 m (OMZ transition), and 1850 m (non-OMZ). Rates and mechanisms of C oxidation did not vary significantly between seasons. However, an exception was found at the 140-m site, which became hypoxic during the southwest monsoon. Considering both seasons, C oxidation rates ranged from 0.73 to 4.86 mmol C m ―2 d ―1 . Generally, OMZ sites and those on the OMZ transition had lower C oxidation rates (0.73―2.90 mmol C m ―2 d ―1 ) than those located below the OMZ (3.13―4.86 mmol C m ―2 d ―1 ). The relative importance of C oxidation via different terminal electron acceptors varied between sites according to the position and intensity of the OMZ. At all sites, a large proportion of measured O 2 consumption (30―100%) was coupled to the oxidation of reduced species; consequently, aerobic processes were essentially absent at low-0 2 sites. In contrast, under higher bottom water O 2 concentrations, aerobic processes accounted for 4―64% of C oxidation. Denitrification largely dominated carbon oxidation at all sites (36―99%). Rates of C oxidation coupled to microbial Mn 4+ and Fe 3+ reduction were quantitatively unimportant. Measured sulphate reduction rates at all sites across the margin were surprisingly low (0―0.45 mmol m ―2 d ―1 ) compared to rates measured on other margin environments.

Tracer Studies of Benthic Communities and Biogeochemical Processes in Coastal and Estuarine Marine Environments

This chapter provides a summary of benthic processes and benthic–pelagic coupling in estuarine and coastal settings and how they contribute to the recognized biogeochemical importance of these environments. This is followed by a synopsis of the environmental controls on benthic faunal communities and the diverse ways in which benthic fauna contribute to sediment biogeochemistry. The main focus of the chapter is on methods and experimental details of tracer techniques that have been developed to assess these faunal processes, a summary of results from recent studies, and suggestions for future research.

Rates and regulation of microbially mediated aerobic and anaerobic carbon oxidation reactions in continental margin sediments from the Northeastern Arabian Sea (Pakistan Margin)

Rates of microbially mediated C oxidation were measured at sites above, within, and below the oxygen minimum zone (OMZ) on the Pakistan margin of the Arabian Sea, before and after the southwest monsoon, with the goal of assessing how low bottom water O 2 concentration affects microbial C oxidation processes. Rates of C oxidation coupled to aerobic and anaerobic processes were measured at five depths: 140 m (seasonally hypoxic), 300 m (OMZ core), 940 m (OMZ transition), 1200 m (OMZ transition), and 1850 m (non-OMZ). Rates and mechanisms of C oxidation did not vary significantly between seasons. However, an exception was found at the 140-m site, which became hypoxic during the southwest monsoon. Considering both seasons, C oxidation rates ranged from 0.73 to 4.86 mmol C m ―2 d ―1 . Generally, OMZ sites and those on the OMZ transition had lower C oxidation rates (0.73―2.90 mmol C m ―2 d ―1 ) than those located below the OMZ (3.13―4.86 mmol C m ―2 d ―1 ). The relative importance of C oxidation via different terminal electron acceptors varied between sites according to the position and intensity of the OMZ. At all sites, a large proportion of measured O 2 consumption (30―100%) was coupled to the oxidation of reduced species; consequently, aerobic processes were essentially absent at low-0 2 sites. In contrast, under higher bottom water O 2 concentrations, aerobic processes accounted for 4―64% of C oxidation. Denitrification largely dominated carbon oxidation at all sites (36―99%). Rates of C oxidation coupled to microbial Mn 4+ and Fe 3+ reduction were quantitatively unimportant. Measured sulphate reduction rates at all sites across the margin were surprisingly low (0―0.45 mmol m ―2 d ―1 ) compared to rates measured on other margin environments.

INDIAN OCEAN BIOGEOCHEMICAL PROCESSES AND ECOLOGICAL VARIABILITY

Rates of microbially mediated C oxidation were measured at sites above, within, and below the oxygen minimum zone (OMZ) on the Pakistan margin of the Arabian Sea, before and after the southwest monsoon, with the goal of assessing how low bottom water O 2 concentration affects microbial C oxidation processes. Rates of C oxidation coupled to aerobic and anaerobic processes were measured at five depths: 140 m (seasonally hypoxic), 300 m (OMZ core), 940 m (OMZ transition), 1200 m (OMZ transition), and 1850 m (non-OMZ). Rates and mechanisms of C oxidation did not vary significantly between seasons. However, an exception was found at the 140-m site, which became hypoxic during the southwest monsoon. Considering both seasons, C oxidation rates ranged from 0.73 to 4.86 mmol C m ―2 d ―1 . Generally, OMZ sites and those on the OMZ transition had lower C oxidation rates (0.73―2.90 mmol C m ―2 d ―1 ) than those located below the OMZ (3.13―4.86 mmol C m ―2 d ―1 ). The relative importance of C oxidation via different terminal electron acceptors varied between sites according to the position and intensity of the OMZ. At all sites, a large proportion of measured O 2 consumption (30―100%) was coupled to the oxidation of reduced species; consequently, aerobic processes were essentially absent at low-0 2 sites. In contrast, under higher bottom water O 2 concentrations, aerobic processes accounted for 4―64% of C oxidation. Denitrification largely dominated carbon oxidation at all sites (36―99%). Rates of C oxidation coupled to microbial Mn 4+ and Fe 3+ reduction were quantitatively unimportant. Measured sulphate reduction rates at all sites across the margin were surprisingly low (0―0.45 mmol m ―2 d ―1 ) compared to rates measured on other margin environments.