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2014
Zapata-Hernandez, G, Sellanes J, Thurber AR, Levin LA, Chazalon F, Linke P.  2014.  New insights on the trophic ecology of bathyal communities from the methane seep area off Concepcion, Chile (similar to 36 degrees S). Marine Ecology-an Evolutionary Perspective. 35:1-21.   10.1111/maec.12051   AbstractWebsite

Studies of the trophic structure in methane-seep habitats provide insight into the ecological function of deep-sea ecosystems. Methane seep biota on the Chilean margin likely represent a novel biogeographic province; however, little is known about the ecology of the seep fauna and particularly their trophic support. The present study, using natural abundance stable isotopes, reveals a complex trophic structure among heterotrophic consumers, with four trophic levels supported by a diversity of food sources at a methane seep area off Concepcion, Chile (similar to 36 degrees S). Although methanotrophy, thiotrophy and phototrophy are all identified as carbon fixation mechanisms fueling the food web within this area, most of the analysed species (87.5%) incorporate carbon derived from photosynthesis and a smaller number (12%) use carbon derived from chemosynthesis. Methane-derived carbon (MDC) incorporation was documented in 22 taxa, including sipunculids, gastropods, polychaetes and echinoderms. In addition, wide trophic niches were detected in suspension-feeding and deposit-feeding taxa, possibly associated with the use of organic matter in different stages of degradation (e.g. from fresh to refractory). Estimates of Bayesian standard ellipses area (SEA(B)) reveal different isotopic niche breadth in the predator fishes, the Patagonian toothfish Dissostichus eleginoides and the combtooth dogfish Centroscyllium nigrum, suggesting generalist versus specialist feeding behaviors, respectively. Top predators in the ecosystem were the Patagonian toothfish D. eleginoides and the dusky cat shark, Bythaelurus canescens. The blue hake Antimora rostrata also provides a trophic link between the benthic and pelagic systems, with a diet based primarily on pelagic-derived carrion. These findings can inform accurate ecosystem models, which are critical for effective management and conservation of methane seep and adjacent deep-sea habitats in the Southeastern Pacific.

2010
Thurber, AR, Kroger K, Neira C, Wiklund H, Levin LA.  2010.  Stable isotope signatures and methane use by New Zealand cold seep benthos. Marine Geology. 272:260-269.   10.1016/j.margeo.2009.06.001   AbstractWebsite

The carbon isotopic composition of seep faunal tissue represents a time-integrated view of the interaction between biology and the biogeochemical gradients within the environment. Here we provide an initial description of carbon and nitrogen stable isotope signatures of dominant symbiont-bearing megafauna and heterotrophic mega- and macrofauna from 10 methane-seep sites on the continental margin of the North Island of New Zealand (662-1201 m water depth). Isotopic signatures suggest that sulfide oxidation supports symbiont-bearing taxa including solemyid and vesicomyid bivalves, and methanotrophic symbionts are present in the seep mussel Bathymodiolus sp Multiple species of Frenulata (Siboglinidae) are present and have a range of isotopic values that are indicative of both thiotroph- and methanotroph-based nutrition. Isotopic composition of the tubeworm Lamellibrachia sp. varied by 23 3 parts per thousand among individuals although there was no consistent difference among sites Variation in methane use by heterotrophic fauna appears to reflect the availability of hard vs. soft substrate, macrofauna on hard substrates had high delta(13)C signatures, reflecting consumption of photosynthetic-derived organic matter Two unique, biotic assemblages were discovered to be fueled largely by methane: a hard-substrate, multi-phyla sponge-associated community (inhabiting the sponge Pseudosuberites sp) and a soft-sediment assemblage dominated by ampharetid polychaetes Isotope signatures yield estimates of 38-100% and 6-100% methane-derived carbon in sponge associates and ampharetid-bed macrofauna. respectively. These estimates are comparable to those made for deeper methane seeps at the Florida Escarpment (3290 m) and Kodiak. Alaska seeps (4445 m) The overall high use of methane as a carbon source by both symbiont-bearing and heterotrophic fauna suggests that New Zealand methane seeps are an ideal model system to study the interaction among metazoans, bacteria, archaea, and their resulting effect on methane cycles. (C) 2009 Elsevier B V All rights reserved

2000
Levin, LA, James DW, Martin CM, Rathburn AE, Harris LH, Michener RH.  2000.  Do methane seeps support distinct macrofaunal assemblages? Observations on community structure and nutrition from the northern California slope and shelf Marine Ecology-Progress Series. 208:21-39.   10.3354/meps208021   AbstractWebsite

Although the conspicuous epifauna of reducing environments are known to exhibit strong morphological, physiological, and nutritional adaptations for life in these habitats, it is less clear whether infaunal organisms do so as well. We examined metazoan macrofauna from methane-seep sediments on the northern California slope (500 to 525 m depth) and from seep and non-seep sediments at 3 locations on the shelf (31 to 53 m depth) to determine whether the community structure and nutritional sources of seep infauna were distinct from those in non-seep, margin sediments. Seep macrofauna consisted mainly of normal slope and shelf species found in productive settings. Several macrofaunal taxa, such as Capitella sp., Diastylopsis dawsoni, and Synidotea angulata, exhibited a preference for seeps. Other taxa, such as the amphipods Rhepoxynius abronius and R, daboius, avoided seeps. Species richness of shelf macrofauna, evaluated by rarefaction and diversity indices (H' and J'), generally did not differ in seep and non-seep sediments. Similarly, stable isotopic composition (delta C-13, delta N-15) Of active seep and non-seep macrofauna did not differ at the 3 shelf sites. Stable isotopic analyses of calcareous material confirmed the presence of methane-influenced pore waters at the slope study site. At one slope clam bed, macrofaunal delta C-13 signatures were lower and delta N-15 values were higher than at another clam bed, inactive slope sediments and shelf sites. However, only 1 of 14 macrofaunal taxa (a dorvilleid polychaete) exhibited isotopic evidence of chemosynthetic nutritional sources. At these sites, seep influence on the ecology of continental margin infauna appears spatially limited and relatively subtle. At their current level of activity, the northern California slope and shelf seeps appear to function as ephemeral, small-scale disturbances that are not sufficiently persistent to allow chemosynthesis-based trophic specialization by most infauna. Rather, we suggest that many of the infauna inhabiting these seep sediments are shelf and slope species preadapted to organic-rich, reducing environments.