Harmful Algal Blooms (HABs)
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The USGS collaborates with local, state, federal, tribal, university, and industry partners to conduct the science necessary to understand the causes and effects of toxic HABs and inform water management and public health decisions. USGS is characterizing the life cycle of HABs, their asociated toxins, and the genes responsible for cyanotoxin production. This work is enhancing the ability of Great Lakes decision-makers to help prevent, prepare for and respond effectively to HABs when they occur. In addition, treatment methods for removing microcystins (bacteria-related toxins) from drinking water are effective but costly, and some treatments may result in toxic by-products. Biodegradation of microcystins is a promising, environmentally friendly, and cost-effective treatment technique. USGS is currently investigating this treatment method, in cooperation with local stakeholders, along Lake Erie.
Learm more at Great Lakes HABs Collaboratory
Biodegradation of Microcystins in Lake Erie
Biodegradation of microcystins, produced by cyanobacterial harmful algal blooms (cyanoHABs) is a promising, environmentally friendly, and cost-effective drinking-water treatment technique that may be used to augment conventional techniques, such as adsorption on activated carbon.
To identify the potential for biodegradation in the Lake Erie Western Basin watershed, samples were collected from source waters and sand filters in drinking-water treatment plants. In laboratory microcosms, potential biodegraders were isolated from these samples and identified by DNA sequencing. Four isolates that grew on microcysin as the sole carbon source and produced biofilms, which are necessary for bacteria attachment and biodegradation in plant sand filters, were further tested to determine biodegradation rates; analyzing the results from final laboratory tests is in progress. A journal article will be written and published in FY2018. These initial studies may lead to economically feasible and effective treatments for toxins caused by cyanobacterial blooms.
Assessing Aquatic Restoration Success Using Biophyscial Models of Ecosystem Services
Understanding the cumulative impact of multiple, simultaneous aquatic restoration actions requires a systems-level evaluation tool. The USGS is collaborating with the US Army Corps of Engineers ERDC Center personnel that developed a preliminary hydrodynamic model (i.e., EFDC model) of the St. Louis River estuary as well as with scientists from the University of Minnesota Duluth (UMD) to develop a predictive model capable of meeting the need for this systems-level evaluation tool.
The goal of the project is to use an expanded and calibrated version of the Corps of Engineers EFDC model to evaluate ecosystem-level responses to restoration projects in the estuary, including long-term changes in hydrology and reductions in sediment and nutrient loading. The proposed hydro-dynamic, mechanistic model will integrate physical, biogeochemical, and trophic-level ecosystem responses to spatially and temporally variable stressor gradients throughout the estuary. The model domain includes transport to the near-shore zone of western Lake Superior, combining the research and monitoring results from a number of local, State, and Federal partners into an integrated model of ecosystem response .The calibrated model will established a baseline understanding of how the estuary system as a whole responds to the aquatic restoration activities in the St. Louis River / Nemadji River estuary: one of the largest and most complex tributary systems in the upper Great Lakes.
Ecosystem Process Monitoring of the Great Lakes
Measurements of ecosystem process are needed to evaluate the success of different restoration strategies and the impacts of environmental gradients.
A major part of this work is the development and deployment of ecological process monitoring stations. Essentially, these are stations where several indices of ecological processes are measured. Processes measured include secondary production, biofouling rates, decomposition and metal corrosion. In addition, samples have been collected to assess biodiversity of macrobiota and bacteria and the availability of high-quality food resources for higher trophic levels (i.e., fish).
Using these stations, we have demonstrated that areas in the immediate vicinity of rivermouths in the western basin of Lake Erie appear to have high rates of secondary production and biofouling. Further, an upcoming publication demonstrates microcystin concentrations are a stronger predictor of spatial variation in secondary production than simply cyanobacterial abundance. Ongoing work in this project is linked to the controls over the production of cyanotoxins in Lake Erie and Green Bay (Lake Michigan), specifically identifying the role of trace metals and iron in facilitating microcystin production.
Quantifying Nutrient Retention and Transformation in the Rivermouth
Algal blooms and nearshore productivity are strongly influenced by nutrient loads, the timing of nutrient delivery, and nutrient form upon delivery. The mouths of rivers are zones of active mixing and nutrient transformation. This work is evaluating the effects of restoration of rivermouth habitats as a mechanism to minimize impacts of excessive nutrient loads from upstream watershedds into the Great Lakes.
Cauterizing Zones of High Potential Nutrient Cycling in Agricultural Catchments
Rivers (including the Fox River, WI) draining agricultural lands in the Laurentian Great Lakes basin transport elevated loads of nitrogen (N) and phosphorus (P) to the lakes (Robertson and Saad 2011). The increased concentration of N and P is causing eutrophication of the lake, creating hypoxic zones and damaging the lake ecosystem. Streams and rivers have some capacity to naturally retain (P) and permanently remove (N) nutrients but these removal zones are patchily distributed along a river course.