PHYTOPLANKTON STUDIES IN COOPERATION WITH THE U.S. ANTARCTIC MARINE LIVING RESOURCES (AMLR) PROGRAM,
JANUARY-MARCH, 2007
Link to NOAA Strategic Plan: NOAA's Mission Goal 1: Protect, Restore, and Manage the Use of Coastal and Ocean Resources through Ecosystem-based Management
NOAA Goal 2: Understand Climate Variability and Change to Enhance Society's Ability to Plan and Respond
RESEARCH OBJECTIVES AND SPECIFIC PLANS TO ACHIEVE THEM
The overall objective of our research project was to assess the distribution and concentration of food reservoirs available to the herbivorous zooplankton populations throughout the AMLR study area during the austral summer. The specific objectives of our work were:
(i) To determine the distribution, biomass, and size distribution of phytoplankton in the upper water column (surface to 200m), with emphasis on the upper 100m,
(ii) To determine or estimate the rate of primary production in the water column,
(iii) To better our understanding of the reasons for the variability in distribution of phytoplankton in relation to dynamic physical processes, nutrient concentrations, and solar irradiance in the upper 100 m of the water column.
These objectives were obtained by the following observations/measurements/methods:
(i) Phytoplankton Distribution in the AMLR Survey Area.
(ii) Mean Chlorophyll-a Concentrations in the Four AMLR Areas.
(iii) Water column profiles in relation to water zones.
(iv) Chl-a and water density.
(v) Profiles of chl-a, in situ chl-a fluorescence, beam attenuation, and solar irradiance.
(vi) Inorganic nutrient and trace metal concentrations.
RESEARCH ACCOMPLISHMENTS
Our data indicate that this season was close to normal based on our 17 previous years. The most unusual feature was either the very deep (> 100 m) or absence of the deep chl-a maximum in WZ-1A waters. This might have been a result of the violent storm activity (water sampling was halted for ~40 hours) that directly preceded our survey of the Elephant Island Area, which is where a majority of the WZ-1A stations are located in the survey area. WZ-1 waters are Fe-stressed, and one suspected result is that in situ fluorescence yield is enhanced, which will lead to over-estimated Chl-a concentrations by the Chelsea fluorometer unless accounted for in the algorithms.
Fig. 2 Changes in Chl-a concentrations over time for incubations with trace-metal clean technique, and where 2 nM Fe was added to natural water samples (solid symbols and lines) and compared with controls in which no Fe was added (open symbols, dashed lines). The cultures were incubated under 40% ambient incident irradiance.
