Using stable isotopes and quantitative community characteristics to determine a local hydrothermal vent food web

Abstract

To investigate food web structure in diffuse flow vent environments, an entire macrofaunal community associated with a single aggregation of the tubeworm Ridgeia piscesae was collected from a vent field on the Juan de Fuca Ridge in the NE Pacific. All members of the community were identified and enumerated, and the biomass and stable carbon (δ 13 C) and nitrogen (δ 15 N) isotope ratios were determined for almost all taxa. Symbiont-bearing invertebrates (primarily R. piscesae) accounted for a vast majority of the biomass of the community, and 3 presumably grazing bacterivorous gastropods dominated the biomass of the consumer fauna. Biomass and abundance of individuals declined from the bacterivore to the scavenger/detritivore to the predator feeding guild. Several species (a folliculinid ciliate, Idas washingtonia, Provanna variabilis) possessed unique stable isotope signatures, suggesting the possibility of symbiotic relationships with autotrophic bacteria. Stable isotope values varied widely between and occasionally within species in the lowest consumer levels suggesting a great diversity of food source 13 C and 15 N composition. Based on the distinct isotopic values of 3 bacterivores, 3 potential pools of isotopically-distinct microbial production were identified. The 4 highest-biomass predatory species (all polynoids) possessed δ 13 C and δ 15 N values consistent with a diet that included the tubeworm R. piscesae, a species comprising 83% of the total biomass in the collection, and the gastropod Depressigyra globulus, a species comprising 10% of the total biomass in the collection. A potential specialist predator (Clypeosectus curvus) on folliculinid ciliates was also identified. Overall the study suggested a dominant pattern of energy transfer from microbial producers to symbiont-bearing siboglinid tubeworms, various bacterivores (gastropods, polychaetes and pycnogonids), and detritivorous polychaetes to predaceous polynoids.

A hydrothermal seep on the Costa Rica margin: middle ground in a continuum of reducing ecosystems

“…Heavy Bassham (CBB) cycle and/or from consumption of bacteria carrying out the rTCA cycle [53]. An isotopic survey of species at Jaco Scar (figure 4a) reveals that, despite the occurrence of planktonic epsilonproteobacteria at this site, the fauna lack the heavy d 13 C signatures characteristic of other hydrothermal vents in the East Pacific [58]. The symbiont-bearing mussels, clams, frenulates and vestimentiferans at Jaco Scar have isotopic signatures consistent with reliance on sulphide oxidation coupled with CBB (average d 13 C ¼ 239 to 226‰) for nutrition, as do the majority of deposit-feeding annelids, grazers and predatory taxa (figure 4a).…”

Biotic and abiotic factors affecting distributions of megafauna in diffuse flow on andesite and basalt along the Eastern Lau Spreading Center, Tonga

“…Tissue stable isotope contents of all species of vent fauna analyzed to date indicate they obtain the bulk of their nutrition from local primary productivity (Fisher et al 1994, Van Dover & Fry 1994, Van Dover 2000, Bergquist et al 2007). Most species do not contain symbionts and either feed on free-living bacteria or consume these primary consumers.…”

“…Understanding the relation between different animals and the abiotic environment and the role of biological interactions in structuring the vent communities have been a primary focus of ecological research at vents for 2 decades. Our understanding of the factors affecting hydrothermal vent community structure has been significantly advanced as a result of intensive research efforts on the Mid-Atlantic Ridge (Desbruyères et al 2000(Desbruyères et al , 2001,the East Pacific Rise (Hessler et al 1985, 1988, Fisher et al 1994, Johnson et al 1994, Shank et al 1998, Luther et al 2001, Van Dover 2003, and the Juan de Fuca Ridge , Govenar et al 2002, Bergquist et al 2007); however, relatively few studies have focused on vent communities in the Western Pacific, particularly the ELSC (Desbruyères et al 1994, Podowski et al 2009). The mobility of the symbiont-containing fauna in this biogeographic province holds promise for new insights into the fundamental processes that structure vent animal communities.…”

Trophic structure of hydrothermal vent communities at Myojin Knoll and Nikko Seamount in the northwestern Pacific: Implications for photosynthesis-derived food supply

“…Stable isotopic analysis is known to be effective for examining the trophic relationships of hydrothermal vent communities (e.g. Bergquist et al 2007). …”