Life Sciences Commons^™

Anatomy Of The Recurrent Coastal Sediment Plume In Lake Michigan And Its Impacts On Light Climate, Nutrients, And Plankton, Henry Vanderploeg, Thomas Johengen, Peter J. Lavrentyev, Changsheng Chen, G. A. Lang, M. A. Agy, M. H. Bundy, J. F. Cavaletto, B. J. Eadie, J. R. Liebig, G. S. Miller, S. A. Ruberg, M. J. Mccormick

Peter J. Lavrentyev

As part of the Episodic Events Great Lakes Experiment, we sampled total suspended matter (TSM), light climate, nutrients, and plankton along cross-margin transects in southern Lake Michigan during February, March, and April 1998-2000 to capture conditions before, during, and after the occurrence of storm-driven recurrent coastal sediment plumes to define the anatomy of the resuspension events and get insights into their interactions with nutrients and plankton. Variability in timing and strength of winter storms among years led to different timing, intensity, and extent of plumes among years. TSM concentrations in the core of plumes varied between 15 and 30 mg …

A Modeling Study Of Benthic Detritus Flux's Impacts On Heterotrophic Processes In Lake Michigan, Changsheng Chen, Lixia Wang, Jianhua Qi, Hedong Liu, Judith Wells Budd, David J. Schwab, Dmitry Beletsky, Henry Vanderploeg, Brian Eadie, Thomas Johengen, James Cotner, Peter J. Lavrentyev

Peter J. Lavrentyev

Effects of sediment resuspension-induced benthic detrital flux on the heterotrophic part of the microbial food web in Lake Michigan were examined using a three-dimensional (3-D) coupled biological and physical model. The model was driven by the realistic meteorological forcing observed in March 1999. Wind-induced surface wave dynamics were incorporated into the physical model to generate the bottom flux. The model-generated benthic detrital flux was assumed to be proportional to the difference between model-calculated and critical stresses at the bottom. The model results indicate that detrital flux at the bottom was a key factor causing a significant increase of phosphorus and …

Effects Of The Zebra Mussel On Nitrogen Dynamics And The Microbial Community At The Sediment-Water Interface, Peter J. Lavrentyev, Wayne S. Gardner, Longyuan Yang

Peter J. Lavrentyev

A flow-through experiment was conducted on intact cores of sediments from Saginaw Bay, Lake Huron, to examine how trophic interactions between filter-feeding bivalve mussels and microbial populations could affect nitrogen dynamics at the sediment-water interface. The zebra mussels used in this experiment removed a large proportion of protozoa and phytoplankton from the overlying water, particularly heterotrophic nanoplankton (up to 82%), while bacterial populations showed less change. A 3-fold decrease in the protozoan to bacterial carbon ratio corresponded to a 2.5-fold increase in relative ammonium removal rates as estimated from the dark loss of N-15-ammonium. Excretion by the bivalves also increased …

Distribution And Dynamics Of Nitrogen And Microbial Plankton In Southern Lake Michigan During Spring Transition 1999-2000, Wayne S. Gardner, Peter J. Lavrentyev, Joann F. Cavaletto, Mark J. Mccarthy, B. J. Eadie, Thomas Johengen, James Cotner

Peter J. Lavrentyev

[ 1] Ammonium and amino acid fluxes were examined as indicators of N and microbial food web dynamics in southern Lake Michigan during spring. Either (NH4+)-N-15 or a mixture of N-15-labelled amino acids (both at 4 muM N final concentration) was added to Lake Michigan water. Net fluxes were measured over 24 h under natural light and dark conditions using deck-top incubators and compared to microbial food web characteristics. Isotope dilution experiments showed similar light and dark NH4+ regeneration rates at lake ( 6 versus 5 nM N h(-1)) and river-influenced ( 20 versus 24 nM N h(-1)) sites. Ammonium …

Effects Of Microzooplankton Growth And Trophic Interactions On Herbivory In Coastal And Offshore Environments, Matthew R. First, Harlan L. Miller Iii, Peter J. Lavrentyev, James L. Pinckney, Adrian B. Burd

Peter J. Lavrentyev

We performed serial dilution experiments to estimate rates of gross phytoplankton growth (L) and grazing mortality (m) in both eutrophic (Corpus Christi Bay, Texas, USA) and oligotrophic (offshore Gulf of Mexico) waters. Two parallel experiments were performed in both environments, with seawater pre-screened through 153 or 25 Inn mesh to observe the responses of microzooplankton (MZP) to dilution treatments. MZP biomass changed over the duration of the experimental incubations; in several treatments, MZP net growth rates were >1 d(-1). Patterns of growth varied between dilutions and initial screening size. In the eutrophic system, the ratio of phytoplankton grazing mortality rate …

Grazing And Virus-Induced Mortality Of Microbial Populations Before And During The Onset Of Annual Hypoxia In Lake Erie, Christopher J. Gobler, Timothy W. Davis, Sarah N. Deonarine, Matthew A. Saxton, Peter J. Lavrentyev, Frank J. Jochem

Peter J. Lavrentyev

Lake Erie is the most productive of the North American Great Lakes and experiences annual periods of hypolimnetic hypoxia with unknown consequences for the microbial food web. We established the abundances and mortality rates of microbes in Lake Erie during thermal stratification and determined how they varied with changes in bottom-water dissolved oxygen concentrations. The microbial plankton community (heterotrophic bacteria, Cyanobacteria, eukaryotic phytoplankton, nanozooplankton, microzooplankton) was quantified in surface and bottom waters along with measurements of herbivory and bacterivory rates on eukaryotic and prokaryotic picoplankton and rates of viral lysis of bacteria. High rates of grazing mortality of prokaryotic picoplankton …

Microzooplankton Growth Rates Examined Across A Temperature Gradient In The Barents Sea, Gayantonia Franzè, Peter J. Lavrentyev

Peter J. Lavrentyev

Microzooplankton Distribution, Dynamics, And Trophic Interactions Relative To Phytoplankton And Quagga Mussels In Saginaw Bay, Lake Huron, Peter J. Lavrentyev, Henry A. Vanderploeg, Gayantonia Franze, Dinorah H. Chacin, James R. Liebig, Thomas H. Johengen

Peter J. Lavrentyev