Title: MACROALGAL CANOPIES CONTRIBUTE TO EELGRASS (<i>ZOSTERA MARINA</i>) DECLINE IN TEMPERATE ESTUARINE ECOSYSTEMS
Abstract: EcologyVolume 82, Issue 4 p. 1007-1022 Article MACROALGAL CANOPIES CONTRIBUTE TO EELGRASS (ZOSTERA MARINA) DECLINE IN TEMPERATE ESTUARINE ECOSYSTEMS Jennifer Hauxwell, Jennifer Hauxwell Boston University Marine Program, Marine Biological Laboratory, Woods Hole, Massachusetts 02543 USA Present address: Department of Zoology, University of Florida, P.O. Box 11825, Gainesville, Florida 32611-8525 USA. E-mail: [email protected]Search for more papers by this authorJust Cebrián, Just Cebrián Boston University Marine Program, Marine Biological Laboratory, Woods Hole, Massachusetts 02543 USA Present address: Dauphin Island Sea Lab, 101 Bienville Boulevard, P.O. Box 369-370, Dauphin Island, Alabama 36528 USA.Search for more papers by this authorChristopher Furlong, Christopher Furlong Boston University Marine Program, Marine Biological Laboratory, Woods Hole, Massachusetts 02543 USASearch for more papers by this authorIvan Valiela, Ivan Valiela Boston University Marine Program, Marine Biological Laboratory, Woods Hole, Massachusetts 02543 USASearch for more papers by this author Jennifer Hauxwell, Jennifer Hauxwell Boston University Marine Program, Marine Biological Laboratory, Woods Hole, Massachusetts 02543 USA Present address: Department of Zoology, University of Florida, P.O. Box 11825, Gainesville, Florida 32611-8525 USA. E-mail: [email protected]Search for more papers by this authorJust Cebrián, Just Cebrián Boston University Marine Program, Marine Biological Laboratory, Woods Hole, Massachusetts 02543 USA Present address: Dauphin Island Sea Lab, 101 Bienville Boulevard, P.O. Box 369-370, Dauphin Island, Alabama 36528 USA.Search for more papers by this authorChristopher Furlong, Christopher Furlong Boston University Marine Program, Marine Biological Laboratory, Woods Hole, Massachusetts 02543 USASearch for more papers by this authorIvan Valiela, Ivan Valiela Boston University Marine Program, Marine Biological Laboratory, Woods Hole, Massachusetts 02543 USASearch for more papers by this author First published: 01 April 2001 https://doi.org/10.1890/0012-9658(2001)082[1007:MCCTEZ]2.0.CO;2Citations: 245 Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Abstract Loss of eelgrass (Zostera marina) habitat from temperate estuaries worldwide often coincides with increased macroalgal accumulations resulting from increased delivery of anthropogenic nitrogen. We conducted macroalgal enclosure/exclosure experiments during summer 1998 within eelgrass populations in two estuaries of Waquoit Bay, Massachusetts, USA, to evaluate how increased macroalgal biomass affects density, recruitment, growth rate, and production of eelgrass. One estuary featured a low nitrogen loading rate and sustained a relatively pristine eelgrass population with a 2 cm high macroalgal canopy. The other estuary had a sixfold higher nitrogen loading rate and a declining eelgrass population with a 9 cm high macroalgal canopy. Experimental units were 1 × 1 m plots of eelgrass fenced within 50 cm high plastic mesh that excluded or included macroalgae at canopy heights ranging from 0 to 25 cm. In both estuaries, rates of eelgrass loss increased, largely a result of decreased recruitment, and growth rates decreased (due to decreased rates of leaf appearance) with increasing macroalgal canopy height. Aboveground summer production in both estuaries decreased exponentially as macroalgal canopy heights increased. We conclude that macroalgal cover is a proximate cause for loss of eelgrass in the higher N estuary since, upon removal of macroalgae, we observed an increase in shoot density, a 55% increase in summer growth, and a 500% increase in summer aboveground net production. Based on summer growth data and density of shoots in our experimental plots the following spring, we suggest that the negative impacts of macroalgal canopies persist, but also that eelgrass recovery upon removal of macroalgae may be possible. To identify the mechanisms by which macroalgae potentially inhibit eelgrass production, we measured changes in nutrient and oxygen concentrations resulting from macroalgal canopies and estimated the relative importance of summer standing stocks of phytoplankton, epiphytes, and macroalgae to potential shading of eelgrass in both estuaries. We document both (1) unfavorable biogeochemical conditions (lowered redox conditions and potentially toxic concentrations of NH4+) imposed by the presence of macroalgal canopies and (2) potential light limitation of eelgrass by standing stocks of producers in the higher N estuary, with estimates of light reduction via macroalgae numerically more important than light sequestration by phytoplankton and epiphytes for newly recruiting shoots. 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Publication Year: 2001
Publication Date: 2001-04-01
Language: en
Type: article
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