PAL-LTER: Introduction

This is a multidisciplinary, multi-investigator project to investigate ecosystem dynamics in Antarctica. A central tenet of the PAL-LTER project is that the annual advance and retreat of sea ice is a major physical determinant of spatial and temporal variability and change in the antarctic marine ecosystem from total annual primary and export production to breeding success in seabirds. Numerous interrelated hypotheses are currently under investigation. PAL-LTER is one of 18 separate LTER programs around the globe with common research objectives, methods and scientific motivations. A comprehensive summary of the PAL-LTER program has recently appeared (Smith et al. 1995, Oceanography 8: 77-86).

Within PAL-LTER, our group "Coupled Ocean-ice Linkages and Dynamics (COLD)" has focused our research on the topics of microbiology and carbon flux. Microorganisms, including unicellular algae, bacteria, viruses, protozoans and small metazoans, are vital components of Southern Ocean habitats. They are largely responsible for the production and decomposition of organic matter, for the primary uptake and regeneration of inorganic nutrients and for export of carbon and energy to intermediate ocean depths. Furthermore, microbial growth and metabolism can have a profound effect on seawater pH and redox state and, therefore can influence the distribution, speciation and availability of certain elements and compounds. Consequently, field data both on individual groups of microorganisms and on the complex interactions among them are necessary for a complete assessment of the role of marine microorganisms on both local and global environments.

Our COLD program research can be broadly divided into several separate but related topics: (1) dissolved inorganic carbon and dissolved organic carbon pool dynamics, (2) bacterial biomass and activity distributions, and controls on bacterial growth and (3) particle sedimentation and export production. These interrelated studies will be used to gain a general understanding of carbon and energy flux through the microbial food web and subsequently to higher trophic levels. As such, they are a central component of the overall PAL-LTER program objectives.