Food for Benthos on the Antarctic Continental Shelf

Project Description

"Primary production in Antarctic coastal waters is highly seasonal,
yielding an intense pulse of biogenic particles to the continental
shelf floor. This seasonal pulse may have major ramifications for
carbon cycling, benthic ecology, and material burial on the west
Antarctic Peninsula (WAP) shelf. Thus, we propose a multi-disciplinary
program ot evaluate the seafloor accumulation, fate and benthic
community impacts of bloom material along a transect of three stations
crossing the Antarctic shelf in the Palmer LTER study area. Using a
seasonal series of five cruises to our transects, we will test the
following hypotheses:

1) A substantial proportion of spring/summer export production (circa
50%) is deposited on the WAP shelf as phytodetritus or fecal pellets.

2) The deposited bloom production is a source of labile POC (or a
'food bank') for benthos for an extended period of time (months)

3) Large amounts of labile bloom POC are rapidly subducted into the
sediment column by the deposit-feeding and caching activities of

4) Macrobenthic detritivores sustain a rapid increase in biomass and
abundance following the spring/summer POC pulse

To test these hypotheses we will use multiple-core and box-core
samples, radiochemical profiles, sediment respirometry, and time-lapse
bottom photography to evaluate (a) seabed deposition and lability of
POC, (b) patterns of POC mixing into sediments, (c) seasonal
variations in macrofaunal and megafaunal abundance, biomass and
reproductive condition, and (d) rates of POC and silica mineralization
and accumulation in the seabed. Fluxes of biogenic materials and
radionuclides into midwater particle traps (D.Karl, P.I.) will be
contasted with our seabed deposition and burial rates to establish
water-column and seabed preservation efficiencies for these
materials. Cruises (each 10-d in length) will be conducted to collect
these data in: November 1999 (shortly pre-bloom); Feb-Mar 2000 (at the
end of the POC pulse); Apr-May 2000 (near the end of the ice-free
summer period), Sept-Oct 2000 (near the end of the winter-ice period),
and Feb-Mar 2001 (end of second annual POC pulse). This project will
substantially improve our understanding of the spring/summer
production pulse on the WAP shelf, and its impacts on seafloor
communities and carbon cycling in Antarctic coastal ecosystems."

Craig R Smith and David J DeMaster, Principal Investigators