John A Berges
John A Berges
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.
- 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. b) Stress response proteins (some of which are proteases) have been of considerable interest in examing responses to freezing in phytoplankton species, and in characterizing stress responses in fish under typical aquarium conditions (vibration, crowding, lighting). c) 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.
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