My laboratory
tackles questions in ecology and cell biology in aquatic organisms using a
range of biophysical, physiological, biochemical and molecular tools. Although we tend to focus on planktonic systems, we are also interested in benthic and
near-shore processes, and we work across the spectrum of living things, from
bacteria to fishes. We move freely
between the laboratory and the field.
Our efforts have been informed by new genome sequence information
becoming available, and we have been involved in several genome annotations of
algal species.
1) Developing indices
of biological rates and processes in aquatic ecosystems
We work with
a variety of biochemical and molecular methods to examine ecological processes
and estimate rates in both marine and freshwaters.
a)
We
have used measurements of the enzyme nitrate reductase
(NR) to examine rates of nitrogen uptake and metabolism in marine and
freshwater phytoplankton and macroalgae, both in the
laboratory and in the field. There
are several interesting questions that could be addressed in Lake Michigan,
including origins of deep-water nitrite maxima, and the relative importance of
new versus recycled nitrogen sources in the lake ecosystem.
b)
The
significance of ‘natural’ mortality and pathogenesis in aquatic
ecosystems is poorly understood.
Biochemical and molecular methods are being used to understand how
phytoplankton cells die under different stresses, and how such death related to
processes like apoptosis. We are
also working with bacterial and algal viruses found in local freshwaters, and
examining how they vary seasonally.
c)
The
biogeochemical processes affecting silicate and sulfur are not well understood
in many aquatic systems. We are
examining blooms of the macroalga, Cladophora,in Lake Michigan to understand the factors driving
them, and how they affect silica cycling.
We are also measuring sulfur content of marine and freshwater algae to
see how it varies under different environmental conditions, and determine the
location of the major pools of S.
d)
We
are using antibodies raised against putative prey species to examine the diets
of the invasive zooplankton predators Bythotrephes longimanus and Cercopagis pengoi and make predictions about their effects on in
Lake Michigan food webs.
2) Characterizing
responses to stress and environmental change
Our interests
in stress responses and acclimation to different environmental conditions span
a wide range of organisms including phytoplankton, zooplankton, corals and
fishes, and include work in the laboratory and in the field.
a)
Measurements
of fluorescence emissions (Fv:Fm)
in phytoplankton and macroalgae have helped us to
assess photosynthetic efficiency and how it changes under different conditions.
a)
Stress
response proteins (some of which are proteases) have been of considerable
interest in examining responses to freezing in phytoplankton species, and in
characterizing stress responses in fish under typical aquarium conditions
(vibration, crowding, lighting).
b)
We
have also been interested in acclimation of seaweeds to high concentrations of
heavy metals, measured using ICPMS methods. Some species show remarkable tolerances
and may be useful in biomonitoring and/or
bioremediation of metals wastes.