Reprint Series No. 21

TEMPORAL, DIEL, AND VERTICAL DISTRIBUTION VARIATION OF EPIPHYTE GRAZERS IN A TEMPERATE EELGRASS (ZOSTERA MARINA L.) SYSTEM

Travis C. Shaw

May 1994

Bibliographic Citation
Shaw, Travis C. 1994. Temporal, diel, and vertical distribution variation of epiphyte grazers in a temperate eelgrass (zostera marina l.) system. Master of Science Thesis, Western Washington University, Bellingham, Washington. 61pp. Washington State Department of Ecology (Publication No. 94-157), Padilla Bay National Estuarine Research Reserve Reprint Series No. 21.

Abstract
Temporal abundance and the vertical distribution of macroinvertebrate epiphyte grazers on eelgrass (Zostera marina) were examined over the diel cycle and through time. Discrete samples of eelgrass and associated epifauna were collected weekly from the apical, intermediate and basal fractions of Zostera marina during the day and at night. The abundance of individual grazer taxa fluctuated temporally during the study. In addition, three of four grazers exhibited a vertical diel migration. Idotea resecata and Caprella califomica were more abundant on the apical fraction of the eelgrass shoot at night. However, the migration of caprellids occurred only during the period of maximum abundance. Similarly, the migration of the opisthobranch phyllaplysia taylori from the basal to the intermediate eelgrass fractions occurred during the period of maximum abundance. The opisthobranch the intermediate Haminoea vesicula was more abundant on the upper end of the eelgrass plant during day and night. The most numerous grazers, Caprella califomica and Phyllaplysia taylori, reached peak abundance at different times and avoided direct competition. In addition, the epiphyte resource was partitioned vertically by the two opisthobranchs. Temporal and vertical distribution variation of grazers reflected niche separation and allowed wider use of the epiphyte resource.