Effects of water level fluctuation and sediment–wa

Authors: Solange Duhamel Géraldine Nogaro Alan D Steinman

Publish Date: 2016/03/22

Volume: 79, Issue: 1, Pages: 57-72

PDF Link

Abstract

Freshwater coastal wetlands are sensitive to drying and wetting events DWE associated with water level fluctuations Prior studies have shown that DWE influence sediment–water nutrient exchange but the fate of these nutrients has received much less attention To address this information gap we investigated how microbial ie bacteria and phytoplankton structure and function respond to DWEinduced release of nutrients from the sediment of mesotrophic and eutrophic coastal wetlands Our approach was threefold 1 sediment from each wetland was subjected to a desiccation 2 month and rewetting 2 days period in the laboratory 2 the overlying water column from the DWE was measured for nutrient concentration and 3 we conducted a microbial response experiment using the water from either DWE experiment containing the nutrients released during the DWE or with added nutrients obtained from commercially available sources but at similar concentrations to those released from the sediments to test the effect of nutrient concentration and source on microbes inhabiting the water column and their role in the fate of the released nutrients in particular phosphate Pi In both coastal wetlands the microbial community structure in the water column absolute and relative abundance of different microbial groups was modified by bacteria resuspended from the sediment after rewetting However results from the microbial response experiments showed that the microbial communities did not grow following inputs of commercially available nutrients or release of sediment nutrients In Pi amended treatments Pi uptake rates increased but not enough to reduce Pi turnover time to values measured in the control As a result Pi concentration and turnover remained high In coastal wetlands with limited hydrologic exchange these elevated nutrients will accumulate and lead to further eutrophication However in open coastal wetlands with substantial hydrologic exchange advected nutrients may influence biological activity in the nearshore zoneWe thank the following individuals who assisted with either sample collection or analyses Dr Bopi Biddanda Anna Harris James Smit Brian Scull Kurt Thompson and Maggie Weinert Financial support was generously provided by an anonymous gift in memory of Donald L and Patrice S Bailey and the Anonymous Fund at the Community Foundation for Muskegon County

Keywords: