Pigment derived phytoplankton composition along the western Antarctic Peninsula
Wendy
Kozlowski, Scripps Institution of Oceanography / San Diego State University, wkoz@ucsd.edu
(Presenting)
Maria
Vernet, Scripps Institution of Oceanography, mvernet@ucsd.edu
Douglas
Deutschman, San Diego State University, doug@sciences.sdsu.edu
Charles
Trees, Center for Hydro Optics and Remote Sensing, trees@nurc.nato.int
Current bio-optical models for remote sensing of chlorophyll a biomass and production are sensitive to changes in specific absorption. Variability in phytoplankton composition is tied to changes in spectral absorption; our ability to follow these changes would be enhanced by a better understanding of community composition. Examined in this study was a thirteen year span (1995-2007) of high-performance liquid chromatography (HPLC) pigments collected as part of the Palmer Long Term Ecological Research (PAL LTER) project along the western Antarctic Peninsula (wAP) between roughly -64 and -68° South. Phytoplankton composition was estimated using CHEMTAX analysis software, and presented here is the temporal and spatial distribution of those assemblages in both surface (50% E0,PAR) and deep euphotic zone (1% E0,PAR) waters. Diatoms and cryptophytes were found to be the two dominant groups at the surface. In the deep water sample, contribution to total chlorophyll a (chl_a) was more evenly distributed between groups, with only diatoms ever consisting of more than 50% of the population. Spatially, diatoms were most abundant (in terms of µg L-1 chl_a) inshore along the entirety of the sampling grid, whereas cryptophyte and prasinophyte abundance was typically highest inshore only in the north. Mixed flagellate concentration was highest inshore in the south-eastern region but in shelf waters further north, and type 4 haptophytes were most abundant along the length of the shelf region. Temporal distribution of groups is discussed in terms of anomalies calculated as yearly differences from the climatological means. Variability in space and time was examined using principle component analysis, and possible relationships between seasonal sea ice retreat and phytoplankton composition, as well as phytoplankton composition and primary production are discussed.