Metatranscriptomic Analyses of Diel Metabolic Functions During a Microcystis Bloom in Western Lake Erie (United States)

This study examined diel shifts in metabolic functions of spp. during a 48-h Lagrangian survey of a toxin-producing cyanobacterial bloom in western Lake Erie in the aftermath of the 2014 Toledo Water Crisis. Transcripts mapped to the genomes of recently sequenced lower Great Lakes isolates showed distinct patterns of gene expression between samples collected across day (10:00 h, 16:00 h) and night (22:00 h, 04:00 h). Daytime transcripts were enriched in functions related to Photosystem II (e.g., ), nitrogen and phosphate acquisition, cell division (), heat shock response (, ), and uptake of inorganic carbon (, ). Genes transcribed during nighttime included those involved in phycobilisome protein synthesis and Photosystem I core subunits. Hierarchical clustering and principal component analysis (PCA) showed a tightly clustered group of nighttime expressed genes, whereas daytime transcripts were separated from each other over the 48-h duration. Lack of uniform clustering within the daytime transcripts suggested that the partitioning of gene expression in is dependent on both circadian regulation and physicochemical changes within the environment

Chronicles of hypoxia: Time-series buoy observations reveal annually recurring seasonal basin-wide hypoxia in Muskegon Lake – A Great Lakes estuary

We chronicled the seasonally recurring hypolimnetic hypoxia in Muskegon Lake – a Great Lakes estuary over 3 years, and examined its causes and consequences. Muskegon Lake is a mesotrophic drowned river mouth that drains Michigan\u27s 2nd largest watershed into Lake Michigan. A buoy observatory tracked ecosystem changes in the Muskegon Lake Area of Concern (AOC), gathering vital time-series data on the lake\u27s water quality from early summer through late fall from 2011 to 2013 (www.gvsu.edu/buoy). Observatory-based measurements of dissolved oxygen (DO) tracked the gradual development, intensification and breakdown of hypoxia (mild hypoxia b4 mg DO/L, and severe hypoxia b2 mg DO/L) below the ~6 m thermocline in the lake, occurring in synchrony with changes in temperature and phytoplankton biomass in the water column during July–October. Time-series data suggest that proximal causes of the observed seasonal hypolimnetic DO dynamics are stratified summer water-column, reduced wind-driven mixing, longer summer residence time, episodic intrusions of cold DO-rich nearshore Lake Michigan water, nutrient run off from watershed, and phytoplankton blooms. Additional basin-wide water-column profiling (2011–2012) and ship-based seasonal surveys (2003–2013) confirmed that bottom water hypoxia is an annually recurring lake-wide condition. Volumetric hypolimnetic oxygen demand was high (0.07–0.15 mg DO/Liter/day) and comparable to other temperate eutrophic lakes. Over 3 years of intense monitoring, ~9–24% of Muskegon Lake\u27s volume experienced hypoxia for ~29–85 days/year – with the potential for hypolimnetic habitat degradation and sediment phosphorus release leading to further eutrophication. Thus, time-series observatories can provide penetrating insights into the inner workings of ecosystems and their external drivers

An algorithm to retrieve chlorophyll, dissolved organic carbon, and suspended minerals from Great Lakes satellite data

An algorithm has been developed for the Great Lakes that utilizes SeaWiFS, MODIS, or MERIS satellite data to estimate concentrations of Chlorophyll (chl), dissolved organic carbon (doc), and suspended minerals (sm). The Color Producing Agent Algorithm (CPA-A) utilizes a specific, updated hydro-optical (HO) model for each lake. The HO models provide absorption functions for all three CPAs (chl, colored dissolved organic matter (cdom), and sm) as well as backscatter relationships for chl and sm, and were generated using simultaneous near surface optical data collected with in situ water chemistry measurements during research cruises in the Great lakes. A single average HO model for the Great Lakes was found to generate insufficiently accurate retrievals for Lakes Michigan, Erie, Superior and Huron. The new HO models were then evaluated with respect to EPA in situ observations, as well as compared to the NASA OC3 retrieval. The CPA-A retrievals provided more accurate chl values for Lakes Michigan, Superior, Huron, and Ontario than those from the NASA approach as well as providing concentrations of doc and sm. The CPA-A chl retrieval for Lake Erie is quite robust, producing reliable chl values within EPA concentration ranges, while the NASA chl retrieval for this case II water provided chl estimates with large uncertainty

Generation of an operational algorithm to retrieve chlorophyll, dissolved organic carbon, and suspended minerals from satellite data of the Great Lakes

A set of algorithms have been developed for the five Great Lake that utilizes SeaWifs, MODIS, or MERIS satellite data to estimate Chlorophyll (chl), dissolved organic carbon (doc), and suspended minerals (sm), the three primary Color Producing Agents (CPAs). The algorithms utilize a specific hydro-optical (HO) model for each lake. The HO models provide absorption functions for all three CPA components as well as backscatter relationships for the chl, and sm and were generated using near surface optical data collected with in situ water chemistry measurements. These in situ optical data are housed in a geospatial data base and will be made available via a web portal to support other Great lakes investigations. These new algorithms provided more accurate chl values then those obtained using the standard OC3 NASA MODIS retrieval when compared to the EPA and other in situ cruise observations, as well as providing the additional information on doc and sm. The suite of atmospheric correction algorithms for MODIS was also evaluated. In general the standard NASA algorithm does an adequate correction all of the time

An algorithm to retrieve chlorophyll, dissolved organic carbon, and suspended minerals from Great Lakes satellite data

An algorithm that utilizes individual lake hydro-optical (HO) models has been developed for the Great Lakes that uses SeaWiFS, MODIS, or MERIS satellite data to estimate concentrations of chlorophyll, dissolved organic carbon, and suspended minerals. The Color Producing Agent Algorithm (CPA-A) uses a specific HO model for each lake. The HO models provide absorption functions for the Color Producing Agents (CPAs) (chlorophyll (chl), colored dissolved organic matter (as dissolved organic carbon, doc), and suspended minerals (sm)) as well as backscatter for the chlorophyll, and suspended mineral parameters. These models were generated using simultaneous optical data collected with in situ measurements of CPAs collected during research cruises in the Great Lakes using regression analysis as well as using specific absorption and backscatter coefficients at specific chl, doc, and sm concentrations. A single average HO model for the Great Lakes was found to generate insufficiently accurate concentrations for Lakes Michigan, Erie, Superior and Huron. These new individual lake retrievals were evaluated with respect to EPA in situ field observations, as well as compared to the widely used OC3 MODIS retrieval. The new algorithm retrievals provided slightly more accurate chl values for Lakes Michigan, Superior, Huron, and Ontario than those obtained using the OC3 approach as well as providing additional concentration information on doc and sm. The CPA-A chl retrieval for Lake Erie is quite robust, producing reliable chl values in the reported EPA concentration ranges. Atmospheric correction approaches were also evaluated in this study