«Status of Nutrients in the Lake Erie Basin Prepared by the Lake Erie Nutrient Science Task Group for the Lake Erie Lakewide Management Plan ...»
Nutrients in the
Lake Erie Basin
Prepared by the Lake Erie Nutrient Science Task Group
for the Lake Erie Lakewide Management Plan
Scientiﬁc information contained in the report Status of Nutrients in the Lake Erie Basin
is current as of November 2008. The report was created to deliberately inform the Lake
Erie Lakewide Management Plan (LaMP) Work Group and to provide a “weight of
evidence” rationale for the Lake Erie Binational Nutrient Management Strategy. The
LaMP recognizes that ongoing research and scientiﬁc investigation will continue to ﬁll knowledge gaps and answer outstanding questions, potentially changing current, prevailing hypotheses. In the spirit of adaptive management, the LaMP will closely monitor research advancements and recommend appropriate adjustments to nutrient management actions to assure that sound science continues to serve as the basis of responsible public policy.
Cover page photo credit: NOAA CoastWatch Great Lakes Region, Lake Erie April 23, 2009 @ 18:33 GMT. http://coastwatch.glerl.noaa.gov $FNQRZOHGJHPHQWV The Lake Erie Nutrient Science Task Group, under the direction of the Lake Erie Lakewide Management Plan (LaMP) Management Committee, prepared the Status of Nutrients in the Lake Erie Basin.
Research and writing: Murray Charlton, contractor to the Lake Erie Millennium Network.
Editing: Jennifer Vincent and Chris Marvin, Environment Canada; Jan Ciborowski, Lake Erie Millennium Network, University of Windsor.
Agencies and individuals that participated on the Lake Erie Nutrient Science Task Group
• Paul Bertram, U.S. EPA
• Murray N. Charlton, LEMN
• Véronique Hiriart-Baer, Environment Canada
• Todd Howell, Ontario Ministry of the Environment
• Chris Marvin, Environment Canada
• Jennifer Vincent, Environment Canada
• Susan Watson, Environment Canada Presented at the Lake Erie Millennium Network 5th Biennial Conference, April 29 – May 1, 2008, University of Windsor, Windsor, Ontario.
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LY 7DEOH RI &RQWHQWV Acknowledgements
Note to Reader
Table of Contents
List of Figures
List of Tables
3.1 Information Gaps
3.2 Mitigation Needs
4.0 Future Directions & Recommendations
Appendices Appendix 1: Calculation of background low concentration Phosphorus load in the Detroit River
Appendix 2: Advances in sewage treatment
/LVW RI 7DEOHV Table 1. Statistical summary of the correlations analysis between the three water quality variables chlorophyll a, total phosphorus and Secchi depth............ 8 Table 2. A summary of the history of algal blooms in western Lake Erie................. 11 YL 2YHUYLHZ The Lakewide Management Plan (LaMP) process is the mechanism in the current Canada – U.S.A. Great Lakes Water Quality Agreement (GLWQA) that brings together the federal Parties and their State and Provincial partners to develop, implement, and manage improvements to the Great Lakes. This technical document is written in support of the Lake Erie LaMP’s efforts to achieve the LaMP Nutrient Management Ecosystem Objective and to prepare a Lake Erie Binational Nutrient Management Strategy. The primary audience is the LaMP Work Group and Management Committee.
Beginning in the 1970s, the trend to increasing nutrient loads and worsening algal conditions in Lake Erie was reversed, consistent with the GLWQA objectives. During that period, most of the damage occurred in Lake Erie’s western basin and, subsequently, water quality improvements were most prevalent there. By the 1990s, phosphorus concentrations were one half of their former levels in the western basin with smaller improvements in the central and eastern basins. However, despite tremendous efforts, total phosphorus concentrations in the western basin remained high enough to stimulate occasional algal blooms. In recent years, these blooms seem to have become worse.
Recent algal problems in Lake Erie prompted a brief review of stimulatory nutrients in the lake. Changes in the lake’s biological components seem to render the nutrient controls of decades past insufﬁcient for today’s conditions in some areas. Offshore algal problems are most prevalent in the western basin. There is a west to central to east basin gradient of improving water quality, consistent with the presence of the largest total phosphorus loads in the west basin. Phosphorus continues to be the limiting nutrient. There is enough nitrogen present that it is not usually limiting algae, although almost any nutrient can be shown to appear limiting to algae on a given day. Nitrogen warrants watching as the ecological implications of ongoing increases are unknown. The relationship between phosphorus and algae as indicated by chlorophyll remains strong in offshore waters.
Nearshore, there is a serious problem with attached ﬁlamentous algae in the east basin and parts of the west basin. Algal problems are usually associated with elevated nutrient supplies but Dreissenid mussels seem mostly responsible for attached algae. At the same time, more research is needed to determine whether whole lake and/or shoreline source control, if possible, would be effective at ameliorating the problem.
For the lands draining to Lake Erie, the LaMP called for aquatic habitat improvements (land use modiﬁcations) that would cause a concomitant reduction of phosphorus loads. Those reductions now seem desirable even if, individually, they may not be capable of effecting large changes in the lake. There is evidence that the agricultural losses of nutrients to the lake, after initial reductions, have become more serious. Total phosphorus concentrations in some rivers such as the Maumee are so high that, despite many actions to date, further strong remedial measures are needed for long-term improvement of algal problems.
Overall reductions in total phosphorus to the lake are still needed. Great Lakes Water Quality Agreement goals and targets are not consistently being met. Agricultural and municipal sources of phosphorus remain mitigation targets, because they have the highest loads at the highest concentrations with the highest availability to algae. A strong nutrient research and monitoring program is needed to address unknowns and to evaluate progress.
'DWD ([WUDFWLRQ DQG 0DQLSXODWLRQ The data used in this technical report for offshore temporal trends in water quality were from the Environment Canada (EC) “STAR” database; U.S. data were provided by Glenn Warren at the U.S. EPA Great Lakes National Programs Ofﬁce (GLNPO). Samples were collected on surveillance, monitoring and research cruises. Offshore data were selected for the eastern and central basins from stations deeper than 20 m. Depth discrimination was not applied to data of the shallow western basin; all values were considered ‘offshore.’ Only the spring and summer season data are presented as these data were collected the most consistently throughout the years. The spring period was deﬁned as the months of April, May and June, while the summer season was deﬁned as the months of July, August and September. The spring data represent the entire water column assuming complete mixing, while the summer values represent data from the epilimnion only for both datasets. For the EC data, typical epilimnion depths of 16 m and 13 m were used for the east and central basins, respectively, while the west basin was assumed to be uniformly mixed throughout the summer season. The GLNPO data were provided for the epilimnion and hypolimnion separately. The minimum dissolved oxygen data is from the central basin only and from the hypolimnion deﬁned as greater than 13 m.
Where necessary, data not normally distributed were plotted on a log scale. Chlorophyll a data are for phaeophytin corrected values and reﬂect a merge of the integrated and discrete depth samples in the EC dataset. This was done to overcome the lack of continuous data in either of these sample types.
Total phosphorus (TP) is comprised of many types of phosphorus compounds in both particulate and soluble forms. Each form has different abilities to grow algae, referred to as its “bioavailability.” Apatite mineral from shore erosion, for example, is a particulate form that is largely unavailable to algae. Soluble reactive phosphorus (SRP) is a soluble form found in sewage and fertilizers that is highly bioavailable. Algal cells (particulate) contain organic phosphorus that will be released upon decomposition.