Microzooplankton Community Structure and Grazing Impact along the Western Antarctic Peninsula

• Main Author: Price, Lori M.
• Format: Text
• Language: English
• Published: W&M ScholarWorks 2012
• Subjects: Marine Biology; Oceanography; Antarctic; Antarctic Peninsula; Marguerite; Marguerite Bay; Palmer Station; Palmer-Station; Southern Ocean; Antarc*; Antarctica; Sea ice
• Online Access: https://scholarworks.wm.edu/etd/1539617922; https://doi.org/10.25773/v5-8b8j-1h33; https://scholarworks.wm.edu/context/etd/article/3052/viewcontent/10632061.pdf

Microzooplankton (zooplankton 20 – 200 μm) are an integral part of aquatic food webs as they can be significant grazers of phytoplankton and bacteria, remineralizers of nutrients, and prey for higher trophic levels. The importance of microzooplankton in many pelagic ecosystems has been established, yet compared to larger zooplankton, microzooplankton are understudied in the Southern Ocean. I quantified microzooplankton community composition and grazing rates along the Western Antarctic Peninsula (WAP) as part of the Palmer Antarctica Long-Term Ecological Research project (PAL LTER). This region is experiencing rapid warming, causing declines in sea ice and changes in the marine food web. I determined distributions of major microzooplankton taxa in January 2010 and 2011 within the top 100 m of the water column, along both north-south and coastal-offshore gradients of the WAP, using microscopy. I found that microzooplankton are potentially adjusting to climate changes along with other trophic levels, as there was generally higher microzooplankton biomass in the south compared to the north. Biomass was higher in surface waters compared to 100 m, and variability in microzooplankton biomass between years and with distance from shore appeared to be influenced by sea ice dynamics. Microzooplankton biomass was also positively correlated with chlorophyll-a and particulate organic carbon (POC), and biomass of several microzooplankton taxonomic groups peaked near Marguerite Bay, historically a productivity hot spot. I also calculated phytoplankton and bacterial growth and grazing mortality rates using the dilution method at select stations along the WAP in January 2009 – 2011 and in the near shore waters near Palmer Station in February – March 2011. Microzooplankton exerted higher grazing pressure on bacteria, relative to grazing on phytoplankton. Microzooplankton also exhibited selective grazing on smaller phytoplankton (picoautotrophs and nanophytoplankton), and on the more actively growing bacterial cells, thus shaping ...