1. Current research projects and status

Diatom genome annotation. I was invited (one of 25 scientists from 6 countries) to participate in the annotation of the complete genome sequence of the diatom Thalassiosira pseudonana, the first eukaryotic alga to be completely sequenced. The annotation was carried out at The Department of Energy’s Joint Genome Institute (Walnut Creek CA). The first overview of the annotation will be published in Science magazine this autumn, and two follow up manuscripts being prepared dealing will nitrogen metabolism and stress responses.

Cell death in phytoplankton. Maria Segovia completed her postdoctoral fellowship in my group in 2002. Her work demonstrated conclusively that apoptosis occurs in the unicellular chlorophyte Dunaliella tertiolecta. Her first paper, demonstrating the phenomenon was published in 2003 and a second dealing with regulation of the process has been submitted. A third manuscript focusing on cell oxidative stress and the cell death response is in preparation. Collaborations with C.D.P Brussaard (Netherlands Institute for Sea Research) are continuing. We have two manuscripts in late stages of preparation: Berges, J.A. D. Franklin and C. D. P. Brussaard. Phytoplankton mortality: the semantics of death. for submission to Limnology and Oceanography as a note, and Brussaard, C.D.P. & Berges, J.A. Application of flow cytometric assays for apoptosis to marine phytoplankton, for submission to Aquatic Microbial Ecology. Dan Franklin completed (and defended) his PhD in 2002. His project examined cell death in free-living and symbiotic dinoflagellates. Two of his thesis chapters have been accepted for publication, and a review is currently being written. In the summer of 2003 I employed an undergraduate (J. Hudgins) to assist in research on cell death supported through a UWM Graduate School Research Award and we have made good progress in identifying candidate freshwater species. In 2003, I recruited a Ph. D. student (Chang Jae Choi) who is interested in pursuing cell mortality from a molecular perspective. This will be aided by sequence data from the annotation project.

Seaweeds metal bioremediation/accumulation. Adam Mellor completed (and defended) his PhD in 2002. His project involved examining metals uptake by seaweeds, in terms of potential for both biomonitoring and bioremediation of metals wastes. At least three chapters from his thesis will be publishable and are currently being prepared as manuscripts (authorship: Mellor A., Dring M.J and Berges J.A. Inter- and intraspecific difference in accumulation of heavy metals in three species of marine macroalgae; Bioremediation of metal-contaminated aqueous wastes using marine macroalgae; Metals content of seaweeds: potential as biomonitors of metal pollution in coastal regions).

Nitrate metabolism in seaweeds. Erica Young completed her postdoctoral work on nitrogen metabolism in marine macroalgae. Writing up is progressing well, with one manuscript submitted and another in preparation (Young E.B., Dring M.J. & Berges J.A. Diel-periodicity and seasonal variability in nitrogen metabolism in intertidal and subtidal brown algae); a third manuscript on the effect of ammonium and nitrate availability on nitrate reductase activity, internal nutrient pools and chemical composition of brown macroalgae is planned.

Dissolved organic nitrogen pools. Kay Sommerville completed her postdoctoral work on organic nitrogen cycling in Strangford Lough, working with myself, G. Savidge and Tom Preston of the Scottish Universities Environmental Research. Our work demonstrated the importance of dissolved protein and peptide pools in coastal waters, and a manuscript is being prepared (Sommerville K., Berges J.A., Savidge G. & Preston T. The importance of dissolved organic nitrogen in macroalgal dominated coastal ecosystems: seasonality of dissolved free and combined amino acids in Strangford Lough, Northern Ireland). I have taken samples from Lake Michigan and these reveal shore to open water gradients in dissolved protein in the lake.

Stress responses in marine algae. Sergio Lourenço (U. Sao Paulo, Brazil) completed a Brazilian-government-sponsored study leave in my laboratory in 2002. We completed experiments examining changes in bulk composition and cellular proteins in two species of microalgae, and two species of macroalgae undergoing nutrient limitation and light deprivation. Results will form the basis for a pair of companion manuscripts to be prepared in 2004. Dr. T. Richardson (now at Texas A&M University) and I completed a series of experiments on freezing tolerance in freshwater algae; these results are currently being analyzed.

Cladophora blooms. With Erica Young and Harvey Bootsma I have been planning research aimed at understanding why Cladophora problems have returned to Lake Michigan. MMSD has funded work this summer in which we employed fluorometric measurements to examine nutrient status of the algae. We are continuing to seek funding for a larger-scale study that will use enzymatic techniques to measure the status of algae and also employ remote sensing and GIS technologies to map distributions and project where blooms might become problematic. With collaborators at University of Waterloo in Canada, we are planning a special workshop to be held in Milwaukee, and also for a special session on algal blooms and lake biogeochemistry at the 2005 International Association for Great Lakes Research, to be held in Ann Arbor, MI. As well, I am continuing to maintain contact with European collaborators, through contributions to European projects under Framework 6 initiatives.

Nitrate reductase in freshwater microalgae. In May 2004 I began work with M. Twiss (Clarkson University) and M. McKay (Bowling Green State University) on nitrate reductase activity in Lake Superior. Nitrate levels in the lake have been steadily rising and there is no clear explanation. I have participated in one cruise and samples for NR activity and protein levels will be collected for me over the next two years. In the longer term 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.

Nitrogen in the Marine Environment. I am currently co-writing a chapter for a revision of the classic marine textbook, Nitrogen in the Marine Environment. The new book will be edited D. G. Capone, D. A. Bronk, M. R. Mullholland and E. J. Carpenter and published by Blackwell Sciences. I will co-author a chapter on “Enzymes and inhibitors” with M. Mullholland.

2. Descriptions of plans for future and when it might be started.

Advances in Marine Biology. I have been invited by the editor to co-author (with M. Mullholland, Old Dominion University) a major review on extracellular enzymes, to be prepared for March 2005.

Sulphur composition of phytoplankton. I have recently purchased a new elemental analyzer capable of measuring particulate sulphur. Within the next 6 months, I plan to begin examining sulphur content of freshwater and marine microalgae. Elemental composition has been powerful tool to examine planktonic processes, but has generally been restricted to C, N and P. Sulphur may be a more conserved element, which might be useful as a scaling variable. I plan to seek NSF funding and initiate collaborations with C. Sandgren, R. Cuhel and external collaborators (e.g. R. Sterner at U. Minnesota, G. Malin at U. East Anglia).

Proteases in freshwater microalgae. Virtually nothing is known about proteases and protein turnover in freshwater algae. I plan to begin characterization of algal proteases in the coming year. Longer term directions include examining the potential for finding novel and therapeutic protease inhibitors in algae (I have discussed a collaboration with E. Cheng), and characterizing algal proteolytic mechanisms (I have contacted R. Vierstra in UW-Madison’s Horticulture department and he is willing to offer assistance).

Indices of condition and growth rate. I would like to revisit work on growth indices of zooplankton that I began during my M. Sc. Several new discoveries and the rise of molecular techniques have opened new approaches to the problem of finding a quick and simple way to assay zooplankton to determine growth rates. Potential collaborations with R. Strickler and colleagues at the Great Lakes Water Institute who are working on Daphnia will be explored in the coming year. As well, a M.Sc. student, D. Gronquist, is beginning work with me on growth rate and lactate dehydrogenase activity in fish species.