Publications (2)0 Total impact
Article: Initial characterization of cold seep faunal communities on the New Zealand Hikurangi margin[show abstract] [hide abstract]
ABSTRACT: Cold-seep communities have been known from the North Atlantic and North Pacific for more than 20 years, but are only now being explored in the Southern Hemisphere. While fisheries bycatch had suggested the presence of cold seeps on the New Zealand margin, the biodiversity and distribution of these communities remained unknown. Explorations using towed cameras and direct sampling gear revealed that cold seep sites are abundant along the New Zealand Hikurangi margin. Initial characterization of the faunal communities at 8 of these sites indicates a fauna that is associated with particular sub-habitats but which varies in abundance between sites. Community composition is typical, at higher taxonomic levels, of cold seep communities in other regions. The dominant, symbiont-bearing taxa include siboglinid (tube) worms, vesicomyid clams and bathymodiolin mussels. At the species level, much of the seep-associated fauna identified so far appears either to be new to science, or endemic to New Zealand seeps, suggesting the region may represent a new biogeographic province for cold-seep fauna. Some overlap at the species and genus level is also indicated between the sampled seep communities and the fauna of hydrothermal vents on the Kermadec Arc in the region. Further taxonomic and genetic identifications of fauna from this study will allow us to fully test the levels of species overlap with other New Zealand chemosynthetic ecosystems as well as with other cold seep sites worldwide. These apparently novel communities exhibit evidence of disturbance from a deep bottom-trawl fishery and appear to be threatened along the entire New Zealand margin. As bottom fisheries, mining, and fossil-fuel exploitation move into deeper waters, seep communities may be endangered worldwide, necessitating the initiation of conservation efforts even as new seep ecosystems are discovered and explored. Our findings highlight the unique nature of anthropogenic impacts in the deep-sea, in which reservoirs of biodiversity can be impacted long before they are even known.Marine Geology.
Article: Sediment community structure around a whale skeleton in the deep Northeast Pacific: Macrofaunal, microbial and bioturbation effects[show abstract] [hide abstract]
ABSTRACT: Chemoautotrophic communities on lipid-rich whale skeletons are known from a total of 16 modern and fossil sites in the deep Pacific Ocean. While the attached fauna of modern whale bones has been studied, the impact of whale falls on surrounding sediment assemblages remains largely unevaluated. Using the research submersible Alvin, we sampled the sediment community at distances of 0, 0.5, 1, 2, 4, and ∼100 m from the lipid-rich skeleton of a 21 m balaenopterid on the 1240 m seafloor in Santa Catalina Basin. When sampled in 1988 and 1991, the skeleton had been on the seafloor for >4 yr and supported a large attached chemoautotrophic assemblage. Sedimentary organic content, microbial biomass and bacterial abundance were not significantly different near the skeleton than in background sediments, and pore-water sulfide concentrations were only modestly elevated (to ⩽20 μM) adjacent to the bones. The species composition of infaunal macrobenthos near the skeleton was similar to that in background sediments, providing little evidence of a specialized enrichment and/or sulfophilic assemblage. Nonetheless, macrofaunal abundance within 0.5 m of the skeleton was reduced by >40%, due to a decline in the paraonid polychaete Levinsenia oculata. The reduction in L. oculata (the community dominant) caused a sharp increase in rarefaction diversity near the skeleton. Bioturbation intensities, evaluated from 234Th profiles, were also dramatically reduced in sediments near the skeleton, as were rates of extracellular lipase activity. We postulate that reduced infaunal abundance and bioturbation near the skeleton resulted from the interference effects of vesicomyid clam-shell debris, and that the low bioturbation rates in turn limited extracellular lipase activity. We conclude that whale skeletons, and the remains of their associated chemoautotrophic assemblages, may physically impact nearby sediment communities for years after the organic and sulfide enrichment effects of whale falls have dissipated, yielding changes in infaunal diversity and bioturbation.Deep Sea Research Part II: Topical Studies in Oceanography.