Add to my Schedule 201C Nov 28, 2018 Oral Abstracts
Living Resources 11:30 AM - 11:45 AM

Since 1989, warmer winter temperatures have facilitated black mangrove (Avicennia germinans) expansion into Spartina alterniflora-dominated salt marsh. Here, we investigated seasonal allocations of carbon and nitrogen to plant tissues and to sediment environments in coastal wetlands dominated by A. germinans or S. alterniflora near Port Fourchon, Louisiana. The two species have different seasonal growth patterns in subtropical regions where they coexist: tropical A. germinans retains leaves year-round but is susceptible to freeze damage, while most leaves of temperate S. alterniflora senesce each winter and resprout the following growing season. Despite S. alterniflora’s potential to uptake nitrogen for regrowth during the growing season, the baseline nitrogen-uptake of A. germinans was higher than S. alterniflora throughout the year. In the absence of freeze events, A. germinans consistently led to significantly lower pore water nitrogen concentrations than S. alterniflora. These results indicate that a vegetation shift from S. alterniflora to A. germinans could result in greater nutrient removal capacity, thereby mitigating eutrophication in coastal waters. Range expansion of dominant vegetation in response to climate change can drive large changes in the supply of ecosystem services – some good, some bad. Collectively, our results advance understanding of changes to nitrogen filtration capacity with climate-induced mangrove encroachment into salt marsh. However, nutrient filtration is just one of many ecosystem services, and the potential benefits of this single service must be considered within the context of the many other ecosystems services that are affected by mangrove expansion and replacement of salt marsh.

Dauphin Island Sea Lab
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