Macroalgal-mediated transfers of water column nitrogen to intertidal sediments and salt marsh plants

• Published in: Journal of experimental marine biology and ecology 2005-07, Vol.321 (1), p.59-69
• Main Authors: Boyer, Katharyn E., Fong, Peggy
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Enteromorpha; Enteromorpha intestinalis; Fundamental and applied biological sciences. Psychology; Marine; N isotopes; N limitation; Salicornia; Salicornia virginica; Salt marsh; Sea water ecosystems; Synecology
• ISSN: 0022-0981; 1879-1697
• DOI: 10.1016/j.jembe.2005.01.005

In many temperate estuaries, mats of opportunistic macroalgae accumulate on intertidal flats and in lower elevations of salt marshes, perhaps playing a role in linking water column nitrogen (N) supply to these benthic habitats. Using a flow-through seawater system and tidal simulator, we varied densities (equivalent to 0, 1, 2, or 3 kg m −2 wet mass) of 15N-labelled macroalgae ( Enteromorpha intestinalis) on estuarine sediments in microcosms with/without pickleweed ( Salicornia virginica) to assess N transfers from algae. In the 6-week experiment, macroalgal biomass increased from initial levels in the lower density treatments but all algae lost N mass, probably through both leakage and decomposition. With all densities of algae added, sediments and pickleweed became enriched in 15N. With increasing mat density, losses of algal N mass increased, resulting in stepwise increases in 15N labeling of the deeper sediments and pickleweed. While we did not detect a growth response in pickleweed with macroalgal addition during the experiment, N losses from algal mats that persist over many months and/or recur each year could be important to the mineral nutrition of N-limited marsh plants. We conclude that N dynamics of intertidal sediments and lower salt marsh vegetation are linked to the N pools of co-occurring macroalgae and that further study is needed to assess the magnitude and importance of N transfers.