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Oceans and Human Health (OHH): Microcystins in the Great Lakes
Primary Investigator:
Gary Fahnenstiel - NOAA/GLERL
Co-Investigators:
Juli Dyble Bressie - NOAA/GLERL
David Millie* -
Florida Institute of Oceanography, GulfBase
NOAA Research Area:
Forecasting ecosystem events
Performance Objective:
Increase number of regional, coastal, and marine ecosystems delineated with approved indicators of ecological health and socioeconomic benefits that are monitored and understood.
Research Milestones:
Define the primary forcing factors and time and space scales that cause HABs and anoxia for selected coastal, ocean, and Great Lakes regions.
Executive Summary of Rationale
Microcystis aeruginosa is the dominant bloom-forming, toxic cyanobacterium in the Great Lakes. Microcystis has (again) become a dominant component of the summer phytoplankton in both Saginaw Bay and western Lake Erie after being a relatively minor component during the late 1980s and early 1990s. The recent blooms of Microcystis have caused considerable concern due to the dependence on these waters as a resource and the health risks attributable to microcystins. Preliminary studies have verified the presence of the cyanotoxin, microcystin, in both systems during the summers of 2003-2005 at concentrations of 0.1-4.0 ug/l. Moreover, significant genetic variability exists within the Microcystis populations in both systems, and the factors contributing to high microcystin concentrations are unknown. The purpose of this study is to determine the factors controlling microcsystin production in western Lake Erie and Saginaw Bay.
Proposed Work
Current/Ongoing
Funding through the NOAA Oceans and Human Health Initiative has supported significant mitigation efforts directed towards cyanobacterial harmful algal blooms in the Great Lakes. During the summers 2003 and 2005, regular sampling was conducted at master stations in western Lake Erie and Saginaw Bay to determine the abundance of Microcystis cells, microcystin concentrations, and a suite of environmental factors. In addition to the bi-weekly sampling, larger scale monitoring has also been conducted over a wider spatial range including sampling at 15-20 stations in Saginaw Bay and western Lake Erie in August 2004, 2005, and 2006, and June 2006. The results from the 2003-2005 field years were analyzed this year and several manuscripts were published (see below).
In these manuscripts we documented that multiple abiotic factors (including annual/episodic meteorological patterns, seasonal/intermittent riverine inflows, annual phosphorus loading, etc.) interact with taxon-specific traits to holistically regulate summer cyanobacteria diversity and abundance in Saginaw Bay, Lake Huron. We also documented that in Saginaw Bay microcystin concentrations appeared to be more controlled by the abundance of Microcystis aeruginosa, and that environmental factors are more important in controlling the abundance and growth rate of M. aeruginosa than in cellular pathways of microcystin synthesis. In both Saginaw Bay and western Lake Erie we documented that the genetic composition of the Microcystis population could impact the concentrations and congeners of microcystin.
Preliminary results from six field experiments in which Microcystis populations were subjected to a series of light and nutrient treatments suggest that environmental factors play a limited role in controlling cellular microcystin concentrations (see Figure 1) consistent with field data. Increased phosphorus caused a significant decrease in microcystin cell quota (2-4X) whereas increased light caused only a minor increase in cell quota. These experiments were conducted in both Saginaw Bay and western Lake Erie, and significant differences in response were noted between the environments.
Additional experiments were conducted in FY08 to further understand the role that nutrients and light play in controlling cellular microcystin production. We have begun preparation of these results for publication in a scientific journal.
In FY08, we also used a variety of statistical approaches, including non-parametric multiplicative regression and neural net analysis, to determine the factors controlling Microcystis abundance in Saginaw Bay. Preliminary results suggest that temperature, total phosphorus and dissolved silica can be used to predict Microcystis abundance in Saginaw Bay. In FY09 we hope to continue this modeling by including more hydrometeorological variables in our analysis.
Figure 1. Microcystin cell quota for Microcystis aeruginosa for various nutrient-light treatments: HL = high light no added P, HL+P = high light plus added P, LL = low light no added P, and LL + P = low light + P.
Scientific rationale
Bloom-forming, toxic cyanobacteria occur worldwide in nutrient-enriched freshwaters. Such blooms can have disastrous short- and long- term consequences for water quality and resource utilization. Consequently, cyanobacteria have been the focus of considerable research and information exists concerning the factors allowing a species to exploit environmental conditions and initiate blooms. In particular, cyanobacterial toxins are noted causative agents for human and animal illness/mortality as well as a litany of environmental-, legal-, and recreational-related problems.
Microcystis aeruginosa is the dominant bloom-forming, toxic cyanobacterium occurring in the Great Lakes. Preliminary studies have verified the presence of the cyanotoxin, microcystin, in both systems. In particular, microcystin concentrations for Saginaw Bay have exceeded the recommended limit of 1 µg/L for drinking water (World Health Organization 1998). In the past two years, we have regularly found concentrations of microcystin › 1ug/l in Saginaw Bay and western Lake Erie during the summer when surface scums of Microcystis were absent.
Despite the concern for toxin concentrations in the Great Lakes, very limited information exists on the factors controlling microcystin concentrations in the Great Lakes.
Governmental/Societal Relevance
Because of the increased incidence of cyanobacterial blooms in the Great Lakes and the public health concerns attributable to microcystins, much attention has been placed on Microcystis blooms and associated toxins within these waters. Relatively high concentrations of microcystin have been found in Saginaw Bay, western Lake Erie, and in the western region of Lake Ontario. During most of last summer, microcystin concentrations in Saginaw Bay and western Lake Erie routinely exceeded the 1 ug/l standard. Also, high concentrations (›200 ug/l) of microcystin have been associated with Microcystis blooms in two coastal lakes on the eastern shore of Lake Michigan.
Relevance to Ecosystem Forecasting
Improvements in ecological forecasting are a critical national need. Much of our forecasting ability is dependent on understanding how environmental drivers change community structure and ecosystem function. Moreover, more research is needed on determining the resiliency of the ecosystem at critical temporal and spatial scales, including those related to specific ecosystem events,e.g. harmful algal blooms (HABs). The concentrations of toxins are an important end-point for ecological forecasting and modeling. Other projects are focused on forecasting cyanobacteria/Microcystis abundance which will complement this project.
Our understanding of factors controlling microcystin production will feed modeling/forecasting efforts directed towards microcystin occurrence and distribution throughout the Great Lakes. Specifically, data generated will ‘initialize’ variables within mechanistic models defining the time-dependent, spatial fields of cyanobacterial abundance and toxicity throughout the Great Lakes (Bierman et al 1984). Mechanistic models for predicting cyanobacteria abundance in the Great Lakes have a long history of use, and only need to be updated by including the filtering activities of non-indigenous mussels. These modeling efforts, coupled with satellite imagery from NOAA-GLERL's CoastWatch site, will serve as an operational and proactive, predictive facility on which to base (and initiate) event-response resource management, potential public health risks, and mitigation efforts concerning growth and potential toxicity of cyanobacteria blooms in the Great Lakes.
Products
Publications:
FY08
Millie, D. F., G. L. Fahnenstiel, J. Dyble, R. Pigg, R. Rediske, R. W. Litaker, and P. A. Tester. 2008. Influence of environmental conditions on summer cyanobacterial abundance in Saginaw Bay, Lake Huron. Aquat. Ecosyt. Health Management. 11:196-205.
Fahnenstiel, G. L., D. F. Millie, J. Dyble, R. W. Litaker, P. A. Tester, M. J. McCormick, R. Rediske, and D. Klarer. 2008. Microcystin concentrations and cell quotas in Saginaw Bay, Lake Huron. Aquat. Ecosyst. Health Management. 11:190-195.
Dyble, J., G. Fahnenstiel, R. W. Litaker, D. Millie, and P. Tester. 2008. Microcystin concentrations and genetic diversity of Microcystis in Saginaw Bay and western Lake Erie. Env. Toxicology. 23:507-516.
FY06
Gregson, B. P., D. F. Millie, C. Cao, G. L. Fahnenstiel, and D. P. Fries. 2006. Single-platform detection and identification of environmental peptide toxins using antibody-capture surfaces with subsequent mass spectrometry detection. J. Chromatography A. 1123:233-238.
Millie, D. F., G. R. Weckman, R. J. Pigg, P. A. Tester, J. Dyble, R. W. Litaker, H. J. Carrick, and G. L. Fahnenstiel. 2006. Modeling phytoplankton abundance in Saginaw Bay, Lake Huron: using artificial neural networks to discern functional influence of environmental v ariables and relevance to a Great Lakes Observing System. J. Phycol. 42:336-349.
Presentations:
FY08
Factors affecting microcystin concentrations and cell quotas in the Great Lakes. Presented at Fourth Symposium on Harmful Algae in the US. Woods Hole, MA. Oct. 29 2007.
FY07
Microcystis and microcystins in Saginaw Bay, Lake Huron. Presented at State of Lake Huron Conference in Honey Harbour, Ontario. October 2006
Influence of environmental factors on microcystin cell quotas. Presented at 50th IAGLR Conference, University Park, Pa.
Milestone Reports:
FY08 Q3 ERP Milestone(s): Determine the importance of nutrients and light in controlling microcystin (a biological toxin) concentrations in Saginaw Bay, Lake Huron.
*Link leads off GLERL's website