A5008275061- Marine and coastal ecosystems
- Microbial Community Ecology and Physiology
- Aquatic Ecosystems and Phytoplankton Dynamics
- Fish Ecology and Management Studies
- Marine Biology and Ecology Research
- Environmental DNA in Biodiversity Studies
- Isotope Analysis in Ecology
- Soil and Water Nutrient Dynamics
- Karst Systems and Hydrogeology
- Genomics and Phylogenetic Studies
- Geology and Paleoclimatology Research
- Groundwater and Isotope Geochemistry
- Protist diversity and phylogeny
- Methane Hydrates and Related Phenomena
- Aquatic Invertebrate Ecology and Behavior
- Marine Bivalve and Aquaculture Studies
- Paleontology and Stratigraphy of Fossils
- Gut microbiota and health
- Oceanographic and Atmospheric Processes
- Coastal and Marine Management
- Groundwater flow and contamination studies
- Geochemistry and Elemental Analysis
- Ocean Acidification Effects and Responses
- Water Quality Monitoring Technologies
- Arctic and Antarctic ice dynamics
Grand Valley State University
2015-2024
Michigan United
2015
University of Minnesota System
2006
University of Minnesota
2000-2003
University of Connecticut
1999
The University of Texas at Austin
1992-1997
Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung
1990
University of Georgia
1988
Although the principal source of marine organic matter is phytoplankton, experimental data on carbon and nitrogen mass balance during their growth cycle are lacking. Phytoplankton from diverse taxonomic groups (Synechococcus bacillaris, Phaeocystis sp., Emiliania huxleyi, Skeletonema costatum) were grown in synthetic seawater media, changes particulate dissolved carbon, nitrogen, carbohydrates followed for 14 d. There was a close molar between inorganic (DIC) uptake total (TOC) production...
Heterotrophic bacteria are a key component driving biogeochemical processes in aquatic ecosystems. In 1998, we examined the role of heterotrophic by quantifying plankton biomass and bacterial planktonic respiration across trophic gradient several small Minnesota lakes as well Lake Superior. The contribution (<1‐ µm fraction) to total ranged from ~10 90%, with highest occurring most oligotrophic waters. size fraction constituted substantial reservoir carbon, nitrogen, phosphorus (14‐58%,...
The effects of photochemical transformations on the bioavailability marine dissolved organic matter (DOM) were investigated in surface and deep water from Gulf Mexico. Seawater samples collected eight depths (15–1,000 m), passed through 0.2‐µm pore‐size filters, exposed to sunlight quartz bottles a flowing seawater deck incubator for 5‐9 h. Following exposure, inoculated (1:10) with unfiltered 15‐m depth, bacterial growth rates estimated 3 H‐leucine incorporation dark incubations. Exposure...
Carbon flow through bacterioplankton can be evaluated only if both growth and respiration are known. Measurements of community bacterial (oxygen consumption) production ([3H]leucine incorporation) were made in highly productive shelf less slope waters the northern Gulf Mexico. Rates respiration, as well abundance dissolved organic C concentrations, declined with depth at locations. Water-column ranged from 0.1 to 3.1 µg liter−1 h−1, rates 0.05 0.45 µM O2 h−1. In comparison slope, was...
The bacterial phylum Verrucomicrobia was formally described two decades ago and originally believed to be a minor member of many ecosystems; however, it is now recognized as ubiquitous abundant in both soil aquatic systems. Nevertheless, knowledge the drivers its relative abundance within-phylum habitat preferences remains sparse, especially lake Here, we documented distribution 12 inland lakes Southeastern Michigan, Laurentian Great Lake (Lake Michigan), freshwater estuary, which span...
Abstract Cyanobacteria are renowned as the mediators of Earth’s oxygenation. However, little is known about cyanobacterial communities that flourished under low‐O 2 conditions characterized most their evolutionary history. Microbial mats in submerged Middle Island Sinkhole Lake Huron provide opportunities to investigate cyanobacteria such persistent conditions. Here, venting groundwater rich sulfate and low O supports a unique benthic ecosystem purple‐colored mats. Beneath mat layer...
We chronicled the seasonally recurring hypolimnetic hypoxia in Muskegon Lake – a Great Lakes estuary over 3 years, and examined its causes consequences. is mesotrophic drowned river mouth that drains Michigan's 2nd largest watershed into Michigan. A buoy observatory tracked ecosystem changes Area of Concern (AOC), gathering vital time-series data on lake's water quality from early summer through late fall 2011 to 2013 (www.gvsu.edu/buoy). Observatory-based measurements dissolved oxygen (DO)...
Freshwater ecosystems constitute a small fraction of our planet but play disproportionately large and critical role in the global carbon cycle.
Abstract The biotic and abiotic controls on major shifts in atmospheric oxygen the persistence of low-oxygen periods over a majority Earth’s history remain under debate. Explanations stepwise pattern oxygenation have mostly neglected effect changing diel illumination dynamics linked to daylength, which has increased through geological time due rotational deceleration caused by tidal friction. Here we used microsensor measurements dynamic modelling interfacial solute fluxes cyanobacterial...
A major episodic sediment resuspension event (25‐yr high), which was triggered by atmospheric and water column instability in an El Niň;o year, temporarily altered the dynamics of autotrophy heterotrophy Lake Michigan. Resuspended sediments, rich organic inorganic nutrients, especially phosphorus, stimulated heterotrophic production despite low temperatures (2ºC or less). During event, southern basin winter bacterial productivity high (64% summertime productivity), along margins lake. The...
Several aspects of bacterial glucose assimilation and production (BP) were investigated over 2 d in the upper 300 m Gulf Mexico. Glucose concentrations ranged from to 15 nM surface seawater; utilization rates 1–3 −1 150 water column 0.02–0.8 deeper (150–300 m). Turnover bacteria similar range 0.01–0.4 . Measured imply that supports ∼5–10% observed BP waters. The limiting factors for varied with depth. seemed be limited by availability inorganic N chlorophyll maximum. Additions nitrate or...
Summary Metagenomic and metatranscriptomic sequencing was conducted on cyanobacterial mats of the M iddle I sland S inkhole ( MIS ), L ake H uron. data from 14 samples collected over 5 years were used to reconstruct genomes two genotypes a novel virus, designated PhV1 type A B . Both viral encode express nblA , gene involved in degrading phycobilisomes, which are complexes pigmented proteins that harvest light for photosynthesis. Phylogenetic analysis indicated viral‐encoded is derived host...
The occurrence of bottom-water hypoxia is increasing in bodies water around the world. Hypoxia concern due to way it negatively impacts lakes and estuaries at whole ecosystem level. During 2015, we examined influence on Muskegon Lake by collecting surface- nutrient samples, bacterial abundance counts, benthic fish community information, performing profiles chlorophyll phycocyanin as proxies for phytoplankton cyanobacterial growth, respectively. Several significant changes occurred bottom...
We examined the organic carbon budget for Earth's largest lake, Lake Superior, in Laurentian Great Lakes. This is a unique, ultra-oligotrophic system with many features similar to oligotrophic oceanic gyres, such as dominance of microbial biomass and dissolved biogeochemical processes. Photo-autotrophy dominant source reduced matter lake. Areal rates primary production are among lowest measured any aquatic system, likely result cold water temperatures low nutrient concentrations...
We studied the motility of filamentous mat-forming cyanobacteria consisting primarily Oscillatoria-like cells growing under low-light, low-oxygen and high-sulfur conditions in Lake Huron's submerged sinkholes using situ observations, vitro measurements time-lapse microscopy. Gliding movement cyanobacterial trichomes (100-10,000 µm long filaments, composed ~10 wide ~3 tall) revealed individual as well group-coordinated motility. When placed a petri dish dispersed ground water from sinkhole,...
The viscous and elastic moduli at different shear rates, together with various biological oceanographic properties, were determined in seawater from hydrological layers the southern North Sea June. parameters included Phaeocystis Noctiluca abundances, chlorophyll a level (Chi), bacteria. HNAN aggregate volume fraction. plankton was jointly dominated by sp. scintillans. abundance showed no correlation any other or viscoelastic parameter, but correlated strongly. each positively mostly...