Vent crab, Austinograea alayseae, lying in wait in a chimney crevice? The shrimp are Chorocaris vandoverae. Photo copyright C.R. Fisher/Ridge2000.It is established that chemoautotrophic primary production is utilized other inhabitants of vent ecosystems. This is evidenced by stable isotope ratios and gut content analysis of selected non-chemoautotrophic fauna. Stable isotope ratios provide a powerful tool to understand trophic relationships based on the predictable fractionation of elements with trophic level. Coupled with mixing model, stable isotopes can show minimum input of a source of primary production into an ecosystem in relation to other sources.
In this chapter I propose to construct a trophic model of this nested (within substrate) 3-foundation species ecosystem. A paper currently in peer review gave hint at some differences in the combined use of carbon and nitrogen stable isotopes in separating out signatures between the three chemoautotrophic foundation species. I will investigate the carbon, nitrogen and sulfur stable isotope composition of whole communities to understand resource partitioning, trophic guild structure and food web interactions in the ELSC ecosystem. Selected fauna from the periphery of the foundation species’ communities will be used to study how chemoautotrophic primary production is utilized away from the source.
• Null hypothesis 1: There is no difference in stable isotope ratios between chemoautotrophic foundation species
o Response: carbon, nitrogen and sulfur stable isotope ratios
o Predictor: foundation species type
• Null hypothesis 2: Stable isotopes ratios will be similar between substrate types for each foundation species
o Response: carbon, nitrogen and sulfur stable isotope ratios
o Predictor: foundation species type by substrate type
• Null hypothesis 3: There is no relationship of associated fauna’s stable isotope ratios to that of the chemoautotrophic foundation species.
o Response: carbon, nitrogen and sulfur stable isotope ratios
o Predictor: foundation species type
• Null hypothesis 4: Stable isotope ratios are similar between trophic guilds (i.e. no apparent structure is present)
o Response: carbon, nitrogen and sulfur stable isotope ratios
o Predictor: trophic guild level
• Other objectives:
o Use a mixing model to determine percentage of vent-derived nutrients used by associated fauna, using the chemoautotrophic fauna as proxies for the vent end-member(s)
o Form a model of the food web and trophic guild structure.
