Aquatic Macroinvertebrate Community Responses to Drought Conditions in a Coastal Plains Floodplain

Document Type

Conference Proceeding

Publication Date

4-10-2013

Publication Title

Proceedings of the Georgia Water Resources Conference

Abstract

Coastal floodplains are productive ecosystems that depend on a regular hydrologic regime that includes a predictable flooding event. Since 2011, ~60-76% of Georgia has experienced abnormally dry to extreme drought conditions. To investigate how an extended drought affects a floodplain ecosystem, we characterized benthic macroinvertebrate communities and organic matter standing stocks on a floodplain of the Altamaha River at the Moody Forest Natural Area. Macroinvertebrate communities were sampled monthly from December 2011-April 2012 and characterized by functional feeding group (FFG) during pre- (December-January); peak- (February-March); and post- (April) flood conditions. There were observed differences in FFG composition over the course of the study. Collector-gatherers were the dominant FFG during pre-flood comprising 85-87% of the community. During peak-flood, filtering macroinvertebrates became more abundant (25- 47% of total community). We observed monthly differences in dissolved oxygen (DO) with a trend of increasing DO with increasing flood stage and consequently decreasing as the waters receded. Changes in abiotic factors such as DO are predicted to contribute to changes in consumer communities. While there was a noticeable hydrological event at the area, gauge height readings indicated that flood stage (approx. 4m) was not reached and discharge remained under the 42 year average during the entire sampling period. Ongoing studies in this area will allow for a comprehensive assessment of the effects of extreme events such as drought on floodplain communities. Furthermore, this study will provide insight into the response and potential resiliency of one of Georgia’s unique ecosystems to a commonly occurring disturbance in the region.

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