MARINE PLANKTON SIZE SPECTRA AND TROPHIC TRANSFER EFFICIENCY AT PELAGIC LONG-TERM ECOLOGICAL RESEARCH (LTER) SITES ACROSS A LATITUDINAL GRADIENT

Plankton size spectra are an empirical way to study trophic transfer efficiency in marine ecosystems. The slopes of size spectra have been related to abiotic factors such as nutrient concentration and temperature, as well as primary productivity, fish biomass, and carbon export, with flatter slopes suggesting more efficient transfer of carbon from smaller to larger organisms. As part of the pelagic Long-Term Ecological Research (LTER) synthesis working group, the four oceanic LTER sites spanning a latitudinal gradient from the Northern Gulf of Alaska to the Northeast U.S. Shelf, California Current, and Antarctic Peninsula, standardized carbon-based biomass measurements for planktonic organisms from heterotrophic bacteria (<1 micron) through phytoplankton to macrozooplankton (as large as 50 mm). The range in the normalized biomass size spectrum (NBSS) spans seven orders of magnitude and is similar across sites. Interesting nonlinear features in size spectra slopes are likely related to characteristics of planktonic community structure, such as the relatively low biomass of heterotrophic bacteria and high biomass of macrozooplankton at Palmer LTER on the western Antarctic Peninsula, which are well-described phenomena in the Southern Ocean. Other deviations from linearity appear to be related to undersampling of certain size classes and variation in methodologies; knowledge that will help inform future synthesis efforts across these diverse programs. Finally, we discuss how size spectra relate to environmental drivers and ecosystem function at these sites.

Presentation Preference: Oral

Primary Presenter: Deborah Steinberg, Virginia Institute of Marine Science (debbies@vims.edu)

Authors:

Deborah Steinberg, Virginia Institute of Marine Science  (debbies@vims.edu)

John Conroy, University of California Santa Cruz  (jaconroy@ucsc.edu)

Alexandra Cabanelas, Woods Hole Oceanographic Institution  (acabanelas@whoi.edu)

Moira Décima, Scripps Institution of Oceanography  (mdecima@ucsd.edu)

Biatriz Dias, University of Alaska Fairbanks  (biadias@uw.edu)

Gwen Hennon, University of Alaska Fairbanks  (gmhennon@alaska.edu)

Russell Hopcroft, University of Alaska Fairbanks  (rrhopcroft@alaska.edu)

Thomas Kelly, University of Alaska Fairbanks  (tbkelly@alaska.edu)

Mark Ohman, Scripps Institution of Oceanography  (mohman@ucsd.edu)

Oscar Schofield, Rutgers University  (oscar@marine.rutgers.edu)

Heidi Sosik, Woods Hole Oceanographic Institution  (hsosik@whoi.edu)

Michael Stukel, Florida State University  (mstukel@fsu.edu)