Science Club Series - 19/02/2015

Biosciences Science Club Series - Lent term 2015
19 February 2015 - 1pm - Zoology Museum (Wallace 129)

Biological oceanographic processes in the Ross Sea, Antarctica: Paradigms lost?

Prof. Walker O. Smith, Jr.

(Virginia Institute of Marine Sciences, USA)

downloaded from: voices.nationalgeographic.com

Our Science Club Series continues with a seminar by Prof. Walker Smith Jr. - a marine scientist interested in understanding what controls phytoplankton growth in the ocean, e.g. the role of iron, and how this affects the carbon pool and carbon fluxes. Furthermore, Walker uses new technology, such as gliders, to understand oceanographic processes, for example the linkages between the spatiotemporal dynamics of phytoplankton blooms, macrozooplankton  and fish distributions, and penguin foraging hotspots.


Abstract
The Ross Sea is one of the most important regions in the Southern Ocean, contributing significantly to the biogeochemical cycles and supporting a diverse and abundant food web, characterized by the world’s largest Adélie and Emperor Penguin colonies and supporting massive numbers of baleen whales, pelagic birds and seals.  

Photo by A. Shields

Its phytoplankton and primary productivity have been characterized as having a unimodal peak in late December dominated by the haptophyte Phaeocystis antarctica, after which the haptophyte biomass disappears and is replaced by diatoms. 

Irradiance limits growth in spring, but iron limitation is common in summer.  Vertical flux is substantial, and largely driven by aggregate formation.  Characteristics of these “paradigms” are described.  

image from: marine.rutgers.edu

Recent data using new and novel technologies have forced us to re-evaluate some basic features of these concepts.  Specifically, the importance of episodic events may be important in both vertical flux and phytoplankton growth. Furthermore, while iron is reduced to low (and apparently limiting) concentrations, phytoplankton growth continues for substantial time periods after Fe becomes reduced.   The role of zooplankton vertical flux can also be important during restricted times.  

The results of numerical models predicting future (+50 and +100 years) conditions suggest that drastic oceanographic and food web modifications will occur, with relatively unpredictable effects for higher trophic levels and biogeochemical cycles.  

Hope to see many of you - everyone most welcome to attend!