Publication Date:
2016-06-04
Description:
Copepods are important grazers on phytoplankton and contributors to carbon export, but their role is poorly understood in the Western Antarctic Peninsula (WAP), a region of high productivity and rapid climate warming. We conducted grazing and egestion experiments with large, dominant copepods each January from 2012 to 2014. We found higher gut evacuation rates ( k ), initial gut pigment and ingestion rates ( I ) for Calanus propinquus and Rhincalanus gigas compared with Calanoides acutus . Since k and I linearly increased with chlorophyll a for most species, ingestion rates were 4–70 times greater in more productive coastal regions than offshore, slope waters. Copepods have a low grazing impact on phytoplankton biomass (〈1%) and productivity (1%, up to 11%) compared with the dominant WAP macro- and microzooplankton. Egestion rates were high (0.8–37.3 µgC ind. –1 day –1 ); however, ~58% of fecal pellets are retained in the upper water column. Daily carbon rations of ~1% indicated feeding on other carbon sources (protozoans and metazoans) to meet metabolic demands. However, during a coastal phytoplankton bloom, daily C rations increased to up to 13%, indicating increased reliance on phytoplankton. Future changes in the WAP plankton community may affect food web carbon flow and export.
Print ISSN:
0142-7873
Electronic ISSN:
1464-3774
Topics:
Biology
