Relative effects of nutrient enrichment and grazing on epiphyte-macrophyte (Zostera marina L.) dynamics

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The independent and interactive effects of nutrient concentration and epiphyte grazers on epiphyte biomass and macrophyte growth and production were examined in Zostera marina L. (eelgrass) microcosms. Experiments were conducted during early summer, late summer, fall, and spring in a greenhouse on the York River estuary of Chesapeake Bay. Nutrient treatments consisted of ambient or enriched (3× ambient) concentrations of inorganic nitrogen (ammonium nitrate) and phosphate. Grazer treatments consisted of the presence or absence of field densities of isopods, amphipods, and gastropods. epiphyte biomass increased with both grazer removal and nutrient enrichment during summer and spring experiments. The effect of grazers was stronger than that of nutrients. There was little epiphyte response to treatment during the fall, a result possibly of high ambient nutrient concentrations and low grazing pressure. Under low grazer densities of early summer, macrophyte production (g m−2 d−1) was reduced by grazer removal and nutrient enrichment independently. Under high grazer densities of late summer, macrophyte production was reduced by enrichment only with grazers absent. During spring and fall there were no macrophyte responses to treatment. The relative influence of epiphytes on macrophyte production may have been related to seasonally changing water temperature and macrophyte requirements for light and inorganic carbon.

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Publication type Article
Publication Subtype Journal Article
Title Relative effects of nutrient enrichment and grazing on epiphyte-macrophyte (Zostera marina L.) dynamics
Series title Oecologia
DOI 10.1007/BF00317683
Volume 93
Issue 2
Year Published 1993
Language English
Publisher Springer
Contributing office(s) National Wetlands Research Center, Patuxent Wildlife Research Center, Wetland and Aquatic Research Center
Description 11 p.
First page 285
Last page 295
Country United States
State Virginia
Other Geospatial York River estuary
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