Introduction

As recently reviewed by Quetin and Ross (1992, "A Long-term Ecological Research Strategy for Polar Environmental Research," Mar. Poll. Bull. 25: 233-238), the Long-Term Ecological Research (LTER) program recognizes that some ecological phenomena occur on time scales of decades or centuries, and that investigations on these time scales are not routinely supported by funding agencies. Without an understanding of interannual variability over the long term, interpretation of ecological experiments and distinguishing long-term trends from cyclic changes in natural ecosystems is difficult. The LTER Network, sponsored by the National Science Foundation, has grown during the last decade to a total of eighteen sites in ecosystems ranging from tall grass prairies to tundra. To facilitate comparisons and the ability to construct ecological generalities, all sites are required to set up research efforts in five core areas:

pattern and control of primary production
spatial and temporal distribution of populations representing trophic structures
pattern and control of organic matter accumulation
pattern of inorganic inputs and movements of nutrients
pattern and frequency of disturbance to the research site

The Palmer LTER, established in the fall of 1990, focuses on the pelagic marine ecosystem in Antarctica, and the ecological processes that link the extent of annual pack ice to the biological dynamics of different trophic levels. Pack ice may be a major physical factor affecting the structure and function of polar biota. Interannual cycles and/or trends in the annual extent of pack ice are hypothesized to impact all levels of the food web, from total annual primary production to breeding success in seabirds. In the region around Palmer Station (64 40'S, 64W) west of the Antarctic Peninsula, the maximum extent of pack ice varies from near shore to halfway across Drake Passage and appears to vary on a six- to eight- year cycle. Satellite data on the maximum extent of pack ice in the Weddell Sea sector show cold winters with heavy pack ice in 1973, and 1980 and 1981, and personal observations confirm that winters of 1980 and 1981, and 1986 and 1987 had heavy ice cover in the region around Palmer Station. The overall objectives of the Palmer LTER are:

to document interannual variability in the development and extent of the annual pack ice and in life-history parameters of primary producers and populations of "key" species from different trophic levels
to quantify the processes that underlie natural variation in these representative populations
to construct models that link ecosystem processes to physical environmental variables and that simulate the spatial/temporal relationships between representative populations
to employ such models to predict and validate the impacts of altered periodicities in the annual extent of pack ice on ecosystem dynamics

To achieve these program objectives, data will be obtained on a variety of spatial and temporal scales including, but not limited to, continuous remote sensing of a variety of environmental parameters at representative locations within the general study area, annual cruises at approximately the same time each year to ascertain the interannual variabiltity and spatial gradients of key oceanographic and biological parameters and at least two process-oriented cruises.

In support of the "Microbiology and Carbon Flux" component of the Palmer LTER program (D. Karl, P.I., Project S-046) a special-focus microbiology process cruise was designed and organized to focus on the trophic coupling among various microbial assemblages including heterotrophic bacteria, archaeobacteria, phytoplankton, protozoans and viruses. This cruise was termed Project SANTA CLAµS (Studies in ANTarcticA: Coupled Linkages Among micro(µ)organismS).