The influence of depth and season on the benthic communities of a Macrocystis pyrifera forest in the Falkland Islands

Information on the ecology of invertebrate communities populating Macrocystis pyrifera forests in the Falkland Islands is scarce. Indeed, the factors influencing diversity, distribution and community structure have never been studied here. Benthic photoquadrats were collected along three permanent 20 m transects at three depth strata (shallow 5–10 m; middle 10–15 m; deep 15–20 m) off the coast of Kidney Island, Falkland Islands from Austral summer 2009 to Austral spring 2010. 146 taxa comprising 10 phyla and 21 classes were recorded during the surveys, with the most abundant sessile and vagile taxa being Spirorbinid worms and the hermit crab Pagurus comptus, respectively. Community structure was influenced by depth, with highest species richness in the middle depth stratum, and strong contrasts between the communities in the shallow and deep depth strata. Influence of season on community structure was evident, though not as strong a factor as depth. Spring and summer months were most species rich, demonstrating a difference between the shallow subtidal regions of Patagonia where species richness was reported to be highest in Austral autumn and winter. The effect of substrate and depth was also investigated for the abundance of individual taxa. This study provides the first description of the fauna and flora of shallow rocky reefs in the Falkland Islands, describing how these communities change over small spatial and temporal scales. The outcomes of this investigation contribute to better understanding ecological patterns of the Falklands shallow benthic environments and adds knowledge to the biogeography of the South Atlantic.