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deepseasgroup - Oceans 2025

Oceans 2025 is NERC's strategic marine science programme. The deepseas group is invloved in workpackages (WPs) in both the continental margins and deep ocean components of Oceans 2025 Theme 5.

Theme 5: Continental Margins and the Deep Ocean

We will be invloved in workpackages (WPs) in both the continental margins and deep ocean components of Theme 5.

Continental Margins
WP 5.1 Physical controls on the benthic ecosystems of continental margins
WP 5.4 Transport of fluids from the sub-seafloor to the seabed and their part in carbon fluxes
WP 5.5 Application of scientific knowledge to the management of
ocean resources
Biogeochemistry of the Deep Ocean
WP 5.8 Benthic system dynamics

Strategic setting. The deep ocean is a vast fluid universe, the largest (yet least explored) habitat on our planet. It is also the largest reservoir for carbon in the Earth system - understanding its capacity to store CO2 is critical to global climate, marine food chains, biodiversity and human existence. This dark, cold, remote frontier is one of NERC’s priority themes - of strategic importance in major global change and biodiversity programmes. The pace of deep-sea technological developments reflects the rapidly increasing human exploitation of the deep ocean, but our knowledge of the deep ocean lags behind our ability to sustainably use its resources.

Main science aims. The aim of Theme 5 is to deliver coordinated, multidisciplinary research on the functioning of the deep ocean from the photic zone to the sub-seabed, encompassing biology, physics, geology, chemistry and mathematical modelling. The goal is to provide the knowledge essential for underpinning UK policy in conserving marine biodiversity, controlling the effects of global change and managing ocean resources in a sustainable manner.Some key objectives are:

• To determine how carbon flow interacts with deep-ocean pelagic and benthic communities in the open ocean and on continental slopes.
• To investigate how benthic ecosystems on continental margins and in the deep ocean respond to spatial and temporal variation in environmental parameters.
• To apply scientific knowledge to the sustainable management of the ocean and its resources.

In “Continental Margins”, the physical processes regulating the transport of sediment will be investigated as well as the transport of hydrocarbons and aqueous fluids from the seafloor. The effect of both of these major processes on the landscape ecology of the continental slope will be assessed. The information will be used to advise on whole ecosystem management strategies, including policy issues relating to Marine Protected Areas and international treaties on the development of open ocean resources.

In “Biogeochemistry of the Deep Ocean”, we will study the flux of particles through the ‘twilight zone’ and the impact on the deep-sea benthos of repackaged organic matter. This will include ROV in situ experimentation and the modelling of benthic ecosystems.

Continental Margins

Human exploitation of continental margins is progressing at a rapidly increasing rate. Hydrocarbons are being extracted from deep-sea sites, new communication cables are being laid and bottom trawling now occurs to >1500 m. We are now beginning to understand connections between sub-surface geological processes – fluid flow, gas hydrates, and microbial activity – and seabed processes and ecosystems. Our objectives include:

to investigate how ecosystems, sedimentary systems and subsurface fluid flow on continental margins respond to spatial and temporal variations in environmental parameters

to examine the consequences of such change for sustainable use of resources on continental margins.

WP 5.1 Physical controls on the benthic ecosystems of continental margins

The classical view of the deep-ocean floor as a gently sloping, sediment-draped, continental margin leading to a flat and featureless abyssal plain – all unaffected by human activities - has been overturned in the last few decades, principally through the use of novel technology. Deep-towed sidescan sonar and ROVs have enabled the deep ocean to be studied in fine detail, particularly in areas of complex terrain. Current advice on sustainable management issues has developed through the science of ‘landscape ecology’. Integrated multidisciplinary research is now needed to understand how organisms are distributed in a complex environment, how their distributions affect the flow of energy, materials and bioresources, and how ecological functions are influenced by natural and human factors. We have already made substantial contributions to this topic, including the discovery of novel and important habitats in UK waters, such as deep-sea barchan dunes and the coral-topped Darwin Mounds. In WP 5.1, we will extend observations of ecological patterns in relation to environmental variables by using ROVs to test experimentally the hypotheses generated from these patterns.

Landscape ecology of continental margins. Recent technical innovations have led to remarkable scientific discoveries, such as giant coral mounds and methane-seeping mud volcanoes, on continental margins across the World. The EU HERMES Integrated Project has developed a comprehensive strategy for the study of Europe’s continental margin. Particular attention is being given to canyon systems because they fast-track material, including pollutants, from land and shelf seas into the deep ocean and they play an important role in carbon storage.

Canyons characterise more than half of the European margin and far exceed their terrestrial equivalents in extent and depth. They may be important ‘hotspots’ of biodiversity and biomass. Episodic ‘flushing’ of canyons mobilises large amounts of sediment and associated material overwhelming benthic ecosystems over a wide area of the abyss as well as the canyon floor. Canyons are complex systems, highly variable in terms of their hydrography, sedimentology, biogeochemistry and biology, and each with its own characteristics. To create useful policies for whole ecosystem management there is a clear need not only for a concerted effort to compare canyons from different biogeochemical provinces and different topographic settings, but also for co-ordinated, multidisciplinary projects relating the fauna to the environmental variables that regulate their distributions, i.e. their landscape ecology. Specific objectives for WP 5.1 include:

i) To describe the physical environment of each canyon system - its bathymetry, the distribution of substratum / sediment facies, physical oceanography - at scales that relate to the distribution of distinct biological communities, and to assess the relative ‘activity’ of each canyon.

ii) To describe the major ecological components of each canyon system and to investigate and ground-truth the distribution of distinct biotic communities within each canyon. By comparing different canyons, and by comparing canyon and adjacent open slope environments, we will assess: a) successional status in relation to canyon activity; b) level of canyon endemism; and c) species turnover (beta-diversity) along the European margin.

iii) To synthesise the physical and ecological information leading to an understanding of the landscape ecology of canyon systems relevant to their environmental management. This objective includes identification and mapping environmental management units (e.g. biological communities / habitats), and identification of key environmental controls on present biological distributions and the relative vulnerability of the various canyon ecosystem components.

Experimental ecology. Practical difficulties have led to deep-sea biology being dominated by observation of ecological patterns. However, many aspects would be better addressed by direct experiment and some can only be tackled in this way. This is notoriously difficult in the deep sea, not only because sophisticated technology is needed, but also because experimentation is best conducted as a series of iterative steps. Through the SERPENT project, we have access to stand-by time in commercial ROV activities. This has provided unprecedented opportunities for in situ experimental ecology, as well as a proving ground for technologies to be used with the UK ROV Isis.

WP 5.4 Transport of hydrocarbons and aqueous fluids from the sub-seafloor to the seabed and their contribution to carbon fluxes

Understanding subsurface fluid flow and its surface expression is vital to the safe exploitation of the marine environment, with implications for climate change and the sustainable management of marine bioresources. Among others WP 5.4 will address the following question: how does fluid flow control benthic ecosystems?

The role of cold seeps for benthic ecosystems. Large communities of unique chemosynthetic organisms have been reported from active mud volcanoes and large pockmarks. There is substantial geological and geophysical evidence for further seabed seepage fuelled by other geological processes such as sediment dewatering, volcanic intrusions, and gas hydrate systems. It is important to assess the relevance of these systems for biodiversity, total biomass and ecosystem functioning, because they are common and thus likely to be important on a margin-wide scale.

WP 5.5 Application of scientific knowledge to the management of ocean resources

The governance of ocean space in terms of resource use and environmental protection falls within the international statute of the United Nations Convention on the Law of the Sea (UNCLOS). UK government departments (FCO, DTI and Defra) require specialised technical advice from marine experts in a range of disciplines in order to develop and monitor UK maritime policy in this legal framework. Theme 5 aims to deliver independent, high-quality scientific advice on territorial sovereignty, marine scientific research, resource management, and the preservation of the marine environment. Much of this advice focuses on continental shelf and margin settings, where demand for both living and non-living resources pushes exploration and exploitation into increasingly deeper waters.

Biogeochemistry of the Deep Ocean

Without understanding the dominant processes occurring in the deep ocean and their variability, it is impossible to evaluate the oceans’ responses to global change. Our lack of understanding of the biota and biogeochemistry of the deep ocean has been highlighted as strategically important in many international assessments. This programme has a unique national role in providing the underpinning knowledge required by policy makers for international agreements on conserving deep-ocean biodiversity, the management of deep ocean bioresources, and the role of the global ocean in climate change.

The deep ocean is Earth’s inner space, and most of it remains unexplored. This important reservoir in the Earth system receives a rain of material from the more turbulent surface layer across the seasonal thermocline and into the twilight zone. There it is transformed biogeochemically, partly returning as nutrients to fuel production in the surface layer, and partly continuing downwards to reach the seabed. The carbon that passes the main ocean thermocline is locked out of contact with the surface mixed layer, and hence the atmosphere, for centuries to millennia. Part of this downward flux fuels the diversity of life on the deep-ocean floor. Although the importance of the deep ocean is recognised, few coordinated measurements and experiments have been made there – and our understanding of its biogeochemistry is still in its infancy. Our overall aim is to understand the processes controlling the downward flux and fate of carbon and associated elements and how changes in these processes impact on life in the deep ocean. Specific objectives include:

to determine how ocean biogeochemical provinces map onto the structure and function of deep-ocean communities.

WP 5.8 Benthic system dynamics

The deep seabed is linked to processes in the upper water column by the downward organic matter flux. Benthic communities integrate processes over space and time, and so large-scale faunal changes reflect major processes occurring in the overlying water column. Strong coupling between surface primary production and the seafloor profoundly influences these communities and hence carbon recycling. Specialized linkages may exist between the deep-sea benthos and sea surface primary production. For example, bio-essential carotenoids, synthesized by cyanobacteria but not by deep-sea benthic organisms, may regulate life processes on the seafloor. We recently compared abyssal benthic communities at two adjacent sites under different production regimes off the Crozet Islands (Southern Ocean). The Crozet eutrophic community resembled North Atlantic eutrophic faunas more closely than an oligotrophic community only 240 km away. These observations confirm the close link between phytoplankton and the benthos, with the latter providing the ultimate measure of organic matter flux and the crucial gateway for carbon burial.

Benthic community models are less developed than pelagic ecosystem models. Most seafloor modelling has focused on early diagenesis via bioturbation coefficients. Benthic models are limited by the difficulty of quantifying biological processes (e.g. respiration and ingestion) due to sampling constraints and problems involved in extrapolating species-specific measurements to community level processes. Models of the size structure of benthic communities that use the close relationship between body size and most biological functions offer a promising approach; these assume that organisms of the same size have similar bioenergetics regardless of identity. Models can be constrained by biomass measurements and in situ pulse-chase experiments that yield respiration and radiolabelled food ingestion rates.

Bentho-pelagic coupling – global patterns. On AMT cruises, we will assess broad-scale changes in benthic communities with biogeochemical provinces using seafloor photography to determine megabenthic composition and standing stock. The megabenthos of comparable abyssal localities (6-8 sites) in the North and South Atlantic will be quantified using the NMFD SHRIMP (Seabed High Resolution IMaging Platform). Owing to low standing stocks in oligotrophic regions we will undertake 6 hr surveys to generate reliable quantitative data. These data will be related to surface ocean and water column biogeochemical measurements to determine how oceanic processes map to the seafloor. Bathysnap time-lapse camera systems will be deployed for periods of up to one year to provide data on temporal variation in the benthos and the flux of organic matter to the seafloor. These data will also make a substantial contribution to understanding global patterns in biodiversity of particular relevance to the international Census of Marine Life programme.

Experimental biogeochemistry of the deep-ocean floor. In order to test hypotheses derived from observed patterns, we will use the UK ROV Isis to conduct experiments at PAP on two dedicated benthic cruises. Repeated access to commercial ROVs through the SERPENT project will facilitate hypothesis testing and will be used to refine experimental techniques prior to the Isis expeditions. We will conduct in situ incubation experiments using food radiolabelling, respiration, size fractionation and proteomic techniques. We will examine how the composition of organic matter (i.e. food quality: diatom, dinoflagellate, prymnesiophyte, cyanobacteria detritus) affects different benthic species. A proteomics analysis will pinpoint proteins that correlate with detritus of different origin and whether the response varies between benthic species.

Modelling deep-ocean benthic processes. We will build on our recent modelling using body size based allometric relationships (for ingestion, respiration, defecation and mortality) to understand controls on observed benthic biomass distributions for meio- and macro-fauna. The model will be expanded to include the megabenthos, which may dominate deep-sea benthic processes. Historic and ongoing data collection at PAP will initially be used to establish and test the model, then new data on benthic process rates, derived from in situ incubation experiments, will be used to refine the models’ parameters. Ultimately, we will couple benthic models to ecosystem models developed under Themes 2 and 9, to investigate how variability in surface ocean and water column processes affects deep-ocean benthic ecosystems.