Diversity, Distribution and Ecology of decapod shrimps in the Ross Sea, Antarctica

Abstract

This dissertation describes the diversity, distribution and ecology of decapod shrimps of the Ross Sea, Antarctica. It hypothesizes their potential past, present and future distribution with Species Distribution Modelling (SDM) using most comprehensive collation of observation records and environmental dataset to date. The data comprised of specimens, high resolution video and photography collected in the Ross Sea cruise by New Zealand Government during International Polar Year – Census of Antarctic Marine Life survey in 2008. This was complimented with data collected from the literature, online databases, and museum collections around the world. The new compendium of high-resolution marine environment datasets created from this study will be a useful resource for researchers to expedite the mapping of species distribution ranges using the popular SDM algorithms. The study found 23 shrimp species in Antarctica and about half of the species have their northern distribution limit coinciding with the Polar Front suggesting it is a biogeographic boundary. The distribution ranges of 8 shrimp species were identified from collected specimens, and provided the first records of shrimps from seamounts and the abyssal plain. Chorismus antarcticus and Notocrangon antarcticus were found only on the continental shelf and upper slopes, while Nematocarcinus lanceopes, Lebbeus n. sp., Dendrobranchiata, Petalidium sp., Pasiphaea cf. ledoyeri, and Pasiphaea scotiae were found on the slopes, seamounts and abyssal plain. In the Ross Sea, C. antarcticus and N. antarcticus appeared abundant on the shelf while N. lanceopes was abundant outside of the shelves. Although, the mean densities reached up to 50 individuals per 1000 m2 in the Ross Sea, overall density was low. However, the sizes of all the species were larger in comparison with populations found elsewhere in the Antarctica. The community composition shrimps’ habitat in the Ross Sea showed C. antarcticus and N. antarcticus habitats were associated with bryozoans and ophiuroids, while N. lanceopes habitat was dominated by sponges, ophiuroids and anemones. The stable isotope analysis of the shrimps identified a carnivorous and detrivorous diet in the Ross Sea. The SDM predicted a widespread distribution of two species in the shelf, slope and seamount regions. Models generated with different spatial resolution showed changes in the relative ranking, but not the composition of, variables. The predicted suitable area was shown to be smaller in models using finer scale environmental layers. Hind casting the distribution of N. lanceopes in the last glacial maximum predicted new glacial refugia around the Southern Ocean, when forecasting the distribution for 2100 the model predicted a range expansion in the east Antarctica and continued pole-ward contraction in the west Antarctica.