Aquatic Sciences Meeting, Albuquerque 2001

SS01 Submerged Aquatic Vegetation and the Water Column (Environmental Connections)

Date: Tuesday, February 13, 2001, Time: 12:00:00 PM

Location: Galisteo

Drake, L, A, Old Dominion University, Norfolk, USA, ldrake@odu.edu

Dobbs, F, C, Old Dominion University, Norfolk, USA, fdobbs@odu.edu

Ball, L, G, Old Dominion University, Norfolk, USA, lball@odu.edu

Zimmerman, R, C, Moss Landing Marine Laboratories, Moss Landing, USA, RZimmer197@aol.com

LIGHT ATTENUATION BY SEAGRASS EPIPHYTES: EFFECTS OF EPIPHYTE ABUNDANCE AND COMPOSITION

Seagrasses support a rich epiphyte community that may contribute as much to community productivity as the seagrasses themselves. Heavy epiphyte loads, however, may outcompete seagrasses for light and nutrients, accelerating seagrass losses. We measured spectral light attenuation as a function of epiphyte load (abundance and composition) and calculated its effect on seagrass light absorption and photosynthesis. We chose two species of seagrasses in environments differing in nutrient regimes, Thalassia testudinum (turtle grass) growing in oligotrophic waters of the Bahamas Bank and Zostera marina (eel grass) from eutrophic environments in Monterey Bay, California. Epiphyte load was quantified from lipid biomass. Light attenuation by epiphytes was determined spectrophotometrically over the visible light range on intact leaves. Thalassia epiphytes from the oligotrophic site absorbed a maximum of 57% of incident light in peak chlorophyll absorption bands and 48% of total PAR. Higher epiphyte loads on Zostera marina from the more eutrophic Monterey Bay absorbed 88% of incident light in peak chlorophyll absorption bands and 52% of total PAR. Data were incorporated into a model that predicts the biomass-dependent light attenuation by epiphytes.

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Aquatic Sciences Meeting, Albuquerque 2001

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