Population dynamics of the ubiquitous Antarctic benthic amphipod Orchomenella franklini and its vulnerability to environmental change

Comprehensive ecological research is still lacking for many of the species that dominate the Antarctic benthos, preventing an adequate understanding of their potential response to environmental change. Here, population dynamics were explored in one of the most ubiquitous nearshore Antarctic benthic amphipods, Orchomenella franklini. Sex, reproductive status and body length were recorded for over 6,000 individuals, sampled from a variety of locations and times at Casey station in East Antarctica. Several life history traits were revealed for O. franklini that exemplify adaptations predicted for a polar environment. These include delayed reproduction, extended brood incubation, low fecundity, longevity and seasonal breeding linked to the summer phytoplankton bloom. There was also preliminary evidence of inter-annual and spatial fluctuations in population structure, potentially reflecting local environmental heterogeneity such as sea-ice duration. The influence of both large scale and local environmental conditions on the ecology of O. franklini provides insight into the vulnerability of this species to environmental change.