High incidence of invertebrate‐chemoautotroph symbioses in benthic communities of the New Zealand fjords

Abstract

In the New Zealand fjords, hydrogen sulfide production from decomposing forest litter is used by chemoautotrophs to fix CO 2[aq] and support benthic food webs. We used quantitative surveys and stable isotope analyses to investigate the contribution of chemoautotrophy to shallow (50 m) and deep (400 m) benthic communities in Doubtful and Bradshaw Sounds. Prevalence of bivalve-chemoautotroph symbioses varied between shallow sites where large-bodied (# 50 mm) Solemya parkinsonii (Solemyidae) were common, and deepbasin sites where small-bodied (, 2 mm) Nucinella maoriana (Manzanellidae) dominated assemblages. d 13 C and d 15 N of sediment indicated that the basal carbon source supporting chemosynthesis was likely decomposing forest litter at 50 m, and decomposing marine algae at 400 m. An isotopic mass balance model weighted to community composition and biomass indicated that the majority of carbon supporting communities at 50 m originated from chemoautotrophy. Concentration of fatty acid biomarkers for heterotrophic bacteria (C 15 and C 17 ) were correlated with the estimated amount of carbon from terrestrial sources, indicating that decomposing forest litter is important in the system. Analysis of the trophic level of these macroinfaunal communities normalized to biomass indicated that the communities sampled from 50 m were on average chemoautotrophic, whereas those sampled at 400 m were on average heterotrophic. The reliance of benthic invertebrate communities on decomposing forest litter and chemoautotrophy, particularly in shallow habitats, demonstrates close connectivity between terrestrial and marine ecosystems in this region and illustrates how diverse food webs can be supported in the shaded and quiescent inner fjord environments.

A safety network against regional population collapse: mature subpopulations in refuges distributed across the landscape

“…Analysis of the diet of lobsters living closest to the Elizabeth Island reserve indicate that they did not feed on the preferred diet of heterotrophic bivalves, but had likely switched to feeding on chemosymbiont bearing clams (Jack et al 2009). These clams occurred at low density deep in the mud, contained high concentrations of sulfur and were likely a low quality food resource (McLeod et al 2010b). Thus the absence of rock lobsters in the Elizabeth Island marine reserve was likely due to the lack of sufficient high quality food due to the anthropogenic degradation of the marine environment (Jack et al 2009).…”

Resource base of blue cod Parapercis colias subpopulations in marginal fjordic habitats is linked to chemoautotrophic production

“…These patterns are consistent with a systematic response by individ- uals occupying the inner fjord habitats to feeding on chemosynthesis-based food webs. At some inner fjord sites, we observed a high incidence of the chemosymbiont-bearing clam Solemya parkinsonii in the stomachs of blue cod, suggesting that blue cod actively feed in the thick layers of decomposing forest material common in these relatively low productivity habitats (McLeod et al 2010b Table 3. General linear model for the fraction of organic matter originating from chemoautotrophic production versus concentration of chl a, density of Ecklonia radiata and presence of mussels (r 2 = 0.87, ically shifted toward higher use of organic matter originating from chemoautotrophy.…”

“…New Zealand's Fiordland marine ecosystem represents an ideal study system in this regard. A high incidence of invertebrate−chemoautotrophic symbioses has been observed within benthic communities of the innermost regions of the New Zealand fjords (McLeod et al 2010b). In these habitats, standing stocks of macroalgae and phytoplankton are relatively low (Goebel et al 2005.…”

“…These attributes of δ 13 C and δ 15 N present a distinct scientific opportunity in the Fiordland system to distinguish between inputs of organic matter from photoautotrophic versus chemoautotrophic production to the food webs supporting blue cod Parapercis colias, an important high trophic level consumer. In this system, the chemosymbiontharbouring clam Solemya parkinsonii makes up a large component of the chemoautotrophic biomass (McLeod et al 2010b) and is an important component of the diet of fishes and invertebrates (Rodgers & Wing 2008, Jack et al 2009). …”

Resource specialisation among suspension-feeding invertebrates on rock walls in Fiordland, New Zealand, is driven by water column structure and feeding mode

“…No evidence for use of organic matter sources depleted in 13 C, such as terrestrial organic matter or chemosynthetically derived organic matter, was observed in these species (e.g. McLeod et al 2010).…”