Wednesday, May 28, 2008 - 9:15 AM
379

The atlantic multidecadal oscillation (AMO) as a surrogate for climate change in the southeastern united states

James A. Gore, Environmental Science & Policy Program, University of South Florida St. Petersburg, 140 6th Ave. South, DAV 258, St. Petersburg, FL 33701, Andrew F. Casper, Aquatic Ecology and Invasive Species Branch, USACE, Waterways Experiment Station, 3909 Halls Ferry Rd., Vicksburg, MS 39180, and Martin H. Kelly, Ecological Evaluation Section, Southwest Florida Water Management District, Brooksville, FL 34604.

In general, predictions of climate change indicate increasingly frequent drought conditions in some areas and increased precipitation in other areas of the southeastern United States.  It has been demonstrated that the Atlantic Multidecadal Oscillation (AMO) in oceanic temperature and subsequent changes in precipitation patterns operates on an approximate 60-year cycle, creating 20- to 40-year wet and dry periods with an order of magnitude difference in mean monthly and daily flows.  As an outgrowth of our work to establish state-mandated MFL’s (minimum flows and levels), we have discovered that the standard time-series analysis, using the previous 20 years of historical record, is not adequate to meet the needs of most instream flow analysis and does not adequately provide management strategies for appropriate flow allotments.  In addition, we have examined the potential for this hydrographic change to mimic projected impacts from climate change.  We have examined the results of PHABSIM analysis for the Alafia and Myakka Rivers of central Florida and have discovered that different life-stages, indeed different species are most affected by gains or losses in habitat during individual wet or dry intervals [we chose 30-year wet and dry periods for simulation]. The duration and frequency of these intervals are likely to be altered by the effects of climate change. It appears that each of these shifts can result in significant changes in community composition.  For example, in the Myakka River, during the low-flow months, largemouth bass (Micropterus salmoides) and benthic macroinvertebrates are the most sensitive to habitat change during dry periods while this sensitivity shifts to spotted sunfish (Lepomis punctatus) during wet periods.  In essence, with changes in sensitivity and dominance of certain fish and macroinvertebrate species, it can be inferred that the lotic community is undergoing a restructuring during every shift from wet to dry hydrographic cycle, as habitat availability favors one species over another.  These changes in community structure suggest that the reconstruction of reference conditions or criteria for bioassessment of these rivers must also take into account the impacts of the AMO and the ability to assess ecological “health.” Thus, it will become important to create two management strategies for rivers influenced directly by the AMO and/or climate change:  one to address ecosystem integrity (including floodplain inundation) during dry hydrographic periods and another to address preservation of existing instream communities during periods dominated by wet hydrograph.  This analysis will continue as we examine the potential for this model to predict the ability of introduced exotics (especially, Plecostomus and Tilapia) to invade Florida rivers and further alter that structure.


Web Page: climate change, minimum flows, time-series analysis

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