Comparison of a sediment trap and plankton pump for time-series sampling of larvae near deep-sea hydrothermal vents
Limnol. Oceanogr. Methods 7:235-248 (2009) | DOI: 10.4319/lom.2009.7.235
ABSTRACT: Studies of larval dispersal and supply are critical to understanding benthic population and community dynamics. A major limitation to these studies in the deep sea has been the restriction of larval sampling to infrequent research cruises. In this study, we investigated the utility of a sediment trap for autonomous, time-series sampling of larvae near deep-sea hydrothermal vents. We conducted simultaneous deployments of a time-series sediment trap and a large-volume plankton pump in close proximity on the East Pacific Rise (2510-m depth). Grouped and species-specific downward fluxes of larvae into the sediment trap were not correlated to larval abundances in pump samples, mean horizontal flow speeds, or mean horizontal larval fluxes. The sediment trap collected a higher ratio of gastropod to polychaete larvae, a lower diversity of gastropod species, and over- or undercollected some gastropod species relative to frequencies in pump sampling. These differences between the two sampling methods indicate that larval concentrations in the plankton are not well predicted by fluxes of larvae into the sediment trap. Future studies of deep-sea larvae should choose a sampling device based on specific research goals. Limited by battery power, a plankton pump in combination with a current meter is useful for estimating horizontal advective fluxes in short-term (days to weeks) studies of larval dispersal. A sediment trap, selecting for larvae with downward trajectories, is more appropriate for studies of larval supply to the benthos. For some species, a time-series sediment trap can collect sequential larval samples for long-term studies (months to years) for correlation to larval settlement and recruitment patterns.