meroplankton communities from the coastal Ross Sea: a latitudinal study

The study of meroplankton communities in the coastal Ross Sea has been difficult due to the logistical challenges associated with sampling in remote areas and with the hurdle of larval identification. As a result, it has not been possible to estimate the latitudinal changes in reproductive strategies of marine invertebrates and to investigate Thorson’s rule—that planktotrophy is less favoured than lecithotrophy and brooding at high latitudes—along the southernmost coastline on Earth. As part of the Latitudinal Gradient Project (Antarctica New Zealand), we studied the meroplankton communities at three sites on the Victoria Land Coast and identified—using morphological and genetic information—11,117 larvae from 52 molecular Operational Taxonomical Units. This allowed for the analysis of patterns in larval diversity and abundance with latitude. Genetic identification permitted the usage of multivariate techniques to study changes in the meroplankton community and to further investigate the latitudinal variation in larval mode of nutrition. Our results showed distinct larval communities at each site, with species dominating nearby benthos being crucial in site discrimination, but with no latitudinal gradients in abundance or diversity. Planktotrophy was predominant in all three sites reflecting the minimal effect of Thorson’s rule within the Ross Sea.