Master of Science (M.Sc.)
Virginia Institute of Marine Science
Copepods are the dominant mesozooplankton in the Southern Ocean, but long- term change in their abundance and distribution along the Western Antarctic Peninsula (WAP), a region experiencing rapid climate warming, is unknown. Copepods are also potentially important grazers of phytoplankton in the WAP and contributors to carbon export through production of sinking fecal pellets. I examined summer (January- February) copepod community structure and abundance along the WAP over two decades (1993-2013) and investigated long-term trends in copepod abundance and their relationship with environmental parameters (sea ice, phytoplankton biomass and productivity, climate indices, and sea surface temperature). Copepods comprised on average 81% of total mesozooplankton abundance in the WAP; the copepod community was dominated by a few species that included Metridia gerlachei, Oithonaspp., and Calanoides acutus. There was a significant long-term increase in total copepod abundance over time, with higher abundances in years with earlier sea ice retreat and higher phytoplankton biomass and productivity. Trends for individual species reflected feeding and life cycle strategies, but generally followed those of total copepods. to examine the impact of copepod grazing on phytoplankton and contribution to carbon export, I conducted grazing and fecal pellet production experiments with the large dominant copepods (Calanus propinquus,Rhincalanus gigas, and C. acutus) in the WAP each January from 2012 to 2014. Copepods have a lowoverall impact on grazing of phytoplankton biomass (<1%) and productivity (1%, up to 11%). Copepods were likely feeding on other sources of carbon (i.e., protozoans and metazoans) besides phytoplankton to meet metabolic demands, especially in the offshore, slope region and in low chlorophyll a conditions. Fecal pellet production (egestion) rates were high, ranging from 0.82 (R. gigas)to 37.3μC ind. day -1 (Paraeuchaeta antarctica), and did not exhibit regional trends. My results suggest mechanisms leading to interannual variability of summer copepod abundance and grazing in the WAP can be used to predict how copepods will respond to future environmental changes and may affect the flow of carbon through the food web and the export of carbon to depth.
© The Author
Gleiber, Miram Rayzel, "Long-Term Change in Copepod Community Structure in the Western Antarctic Peninsula: Linkage to Climate and Implications for Carbon Cycling" (2014). Dissertations, Theses, and Masters Projects. William & Mary. Paper 1539617951.