Project Title

CAREER: Understanding Microbial Heterotrophic Processes In Coastal Antarctic Waters

Summary

Event Number:
B-285-P

Program Director:
Dr. William Ambrose

ASC POC/Implementer:
Matthew Erickson / Jamee Johnson

Principal Investigator(s)

Mr. Jeff Shovlowsky Bowman
jsbowman@ucsd.edu
University of California San Diego

Location

Supporting Stations: Palmer Station
Research Locations: Palmer Station

Description

Despite decades of observations of ecological processes along the western Antarctic Peninsula (WAP) surprisingly little is known about the role of heterotrophic microbes in the WAP marine food web. Recent model-based research suggests that the microbial loop, the repackaging of dissolved organic carbon (DOC) by heterotrophic bacteria for consumption by bacterivores, is increasing in importance in the northern WAP region, where the timing and extent of sea ice cover is highly variable. The proposed work will address critical questions regarding the sensitivity and ecological role of the WAP microbial loop through a series of grazing experiments to assess bacteria mortality by bacterivorous protists and bacteriophages. These experiments will be coupled with observations of ecophysiology including bacterial production and respiration, and microbial community structure, to identify how specific Antarctic heterotrophic bacterial taxa respond to the physiological and ecological stress of the WAP environment. These data will be used to reparametrize the Palmer Ecosystem Model for a series of experiments to test food web sensitivity to ecological change, and a community segmentation approach will be applied to integrate the community structure data and modeling experiments in a novel way.

Field Season Overview

In coordination with the Palmer Long Term Ecological Research (PAL-LTER) program, two participants will deploy to Palmer Station in 2023. Fieldwork at Palmer Station will require visits via rigid-hulled inflatable boats (RHIB) to PAL-LTER Station E to collect water samples from 5m, 35m, and 55m depths, which will ideally be in collaboration with PAL-LTER (expected frequency of twice each week). These samples will be used in dilution experiments in the outdoor incubator to measure rates of heterotrophic bacteria mortality by viruses and protists. Basic parameters will be measured in water collected from all depths. Due to the high demand for water samples, multiple casts at sampling sites will be required. Zodiacs may be required if RHIBs are over-subscribed or RHIB operators are not available. Team members will also collect daily samples from Palmer Station's unfiltered seawater intake. These daily samples will provide a more highly resolved view of bacterial and protist community structure and abundance, and a source of material for grazing experiments and the remaining parameters in the event that conditions prevent sampling for an extended period.

Deploying Team Members