The impact of chemosynthetic carbon sources in marine food webs at Arctic cold seeps

Understand the extent to which methane-derived carbon from cold seeps (originating from petroleum/gas reservoirs) is incorporated into higher trophic level organisms in the Barents Sea.

Background

The Barents Sea is a hotspot of ecological diversity and marine productivity for the circumpolar Arctic and at the same time an economically important region supporting both Norwegian petroleum interests and fisheries. Associated with the gas reservoirs in the Barents Sea, there are large areas where methane gas is naturally emanating from the seabed. Until recently, these so called ‘cold seeps’ were thought to be relatively isolated, but it is now apparent that seeps are widespread in the Barents Sea and Svalbard margin. These seabed emissions can be strong environmental driver that influences the biosphere and local seafloor conditions, including ecosystem function and animal communities.

Figure 1: An American plaice, Hippoglossoides platessoides, is lying in a dense field of chemosymbiotic worms at a Barents Sea cold seep (Photo: from Åström et al. 2016).

At cold seeps, food webs can be fueled by chemosynthesis where the energy source for life provided by reduced chemical compounds (e.g. methane, sulphide) rather than sunlight via photosynthesis. Chemosynthesis generates energy from seeping hydrocarbons in near-surface sediments via microbial processes (anaerobic and aerobic oxidation of methane). Animals inhabiting seeps can rely directly on microbes providing them with energy via chemosymbiosis or could possibly utilize chemosynthetic carbon via predator-prey interactions through the food web. By combining analyses of stable isotope ratios of carbon (δ¹³C) and nitrogen (δ¹⁵N) to assess energy sources and trophic structure, we can document ecosystem characteristics and predator-prey interactions at these cold seeps.

Despite the substantial interest in petroleum activities in the Barents Sea, the ecological significance of methane cold seeps have remained poorly explored. This VISTA project will focus on interaction between high trophic level taxa, the input of chemosynthetic carbon as food resources and the utilization of methane in the Arctic biosphere. Furthermore, will explore the role of cold seep ecosystems within the context of a Barents Sea undergoing large environmental changes and provide new interdisciplinary information on Arctic benthos.

Figure 2: A close-up of a small chemosymbiotic worm from a Barents Sea cold seep. These worms cannot feed themselves, they have neither a mouth nor gut, and instead they host endo-symbionts (microbes) that sustain them with energy via chemosynthesis. Photo: from Åström et al. 2016).

Related published peer-reviewed articles:
Sen A., Åström, E.K.L., Hong W-L., Portnov A., Waage M., Serov P., Carroll, M.L., and Carroll, J. (2018) Geophysical and geochemical controls on the megafaunal community of a high Arctic cold seep. Biogeosciences 15, 4533–4559 doi: 10.5194/bg-15-4533-2018

Åström E.K.L., Carroll M.L., Sen, A., Ambrose Jr W.G., Silyakova A and Carroll, J. (2018). Methane Cold Seeps as Biological Oases in the High-Arctic Deep-Sea. Limnology & Oceanography doi:10.1002/lno.10732

Åström, E. K. L., Oliver, P. G. & Carroll, M. L. (2017). A new genus and two new species of Thyasiridae associated with methane seeps off Svalbard, Arctic Ocean. Mar. Biol. Res. 13, 402–416 doi:10.1080/17451000.2016.1272699

Åström E.K.L, Carroll M. L., Ambrose Jr W. G., & Carroll J. (2016). Arctic cold seeps in marine methane hydrate environments: impacts on shelf macrobenthic community structure offshore Svalbard. Marine Ecology Progress Series 552: 1-18. doi: 10.3354/meps11773