Perspectives in visual imaging for marine biology and ecology: from acquisition to understanding

Durden J, Schoening T, Althaus F, et al. Perspectives in Visual Imaging for Marine Biology and Ecology: From Acquisition to Understanding. In: Hughes RN, Hughes DJ, Smith IP, Dale AC, eds. Oceanography and Marine Biology: An Annual Review. 54. Boca Raton: CRC Press; 2016: 1-72

Photographic survey of benthos provides insights into the Antarctic fish fauna from the Marguerite Bay slope and the Amundsen Sea

We reviewed photographic images of fishes from depths of 381–2282 in Marguerite Bay and 405–2007 m in the Amundsen Sea. Marguerite Bay fishes were 33% notothenioids and 67% non-notothenioids. Channichthyids (47%) and nototheniids (44%) were the most abundant notothenioids. The deep-living channichthyid Chionobathyscus dewitti (74%) and the nototheniid genus Trematomus (66%) were the most abundant taxa within these two families. The most abundant non-notothenioids were the macrourid Macrourus whitsoni (72%) and zoarcids (18%). Amundsen Sea fishes were 87% notothenioids and 13% non-notothenioids, the latter exclusively Macrourus whitsoni. Bathydraconids (38%) and artedidraconids (30%) were the most abundant notothenioids. We observed that Macrourus whitsoni was benthopelagic and benthic and infested by large ectoparasitic copepods. Juvenile (42-cm) Dissostichus mawsoni was not neutrally buoyant and resided on the substrate at 1277 m. Lepidonotothen squamifrons was seen near and on nests of eggs in early December. A Pogonophryne spp. from 2127 m was not a member of the deep-living unspotted P. albipinna group. Chionobathyscus dewitti inhabited the water column as well as the substate. The pelagic zoarcid Melanostigma gelatinosum was documented in the water column a few meters above the substrate. The zoogeographic character of the Marguerite Bay fauna was West- or low-Antarctic in zoogeographic character and the Amundsen Sea was East- or high-Antarctic

No barrier to emergence of bathyal king crabs on the Antarctic shelf

Cold-water conditions have excluded durophagous (skeleton-breaking) predators from the Antarctic seafloor for millions of years. Rapidly warming seas off the western Antarctic Peninsula (WAP) could now facilitate their return to the continental shelf, with profound consequences for the endemic fauna. Among the likely first arrivals are king crabs (Lithodidae), which were discovered recently on the adjacent continental slope. During the austral summer of 2010-2011, we used underwater imagery to survey a slope-dwelling population of the lithodid Paralomis birsteini off Marguerite Bay, WAP for environmental or trophic impediments to shoreward expansion. The average density was ~4.5 ind·1000m-2 within a depth-range of 1100-1500 m (overall observed depth-range 841–2266 m). Evidence of juveniles, molting, and precopulatory behavior suggested a reproductively viable population on the slope. At the time of the survey, there was no thermal barrier to prevent the lithodids from expanding upward and emerging on the outer shelf (400–500 m depth); however, near-surface temperatures remained too cold for them to survive in shallow, coastal environments (<200 m). Ambient salinity, composition of the substrate, and the depth-distribution of potential predators likewise indicated no barriers to expansion onto the outer shelf. Primary food resources for lithodids—echinoderms and mollusks—were abundant on the upper slope (500–800 m) and outer shelf. At present rates of warming, lithodids should emerge in outer-shelf environments within several decades. As sea temperatures continue to rise, they will likely play an increasingly important trophic role in subtidal communities closer to shore