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MEASURING INVERTEBRATE GRAZING ON SEAGRASSES AND EPIPHYTES
Citation:
Zupo, V., W G. Nelson, AND M. C. Gambi. MEASURING INVERTEBRATE GRAZING ON SEAGRASSES AND EPIPHYTES. Chapter 14, Short, FT; Coles, RG (ed.), Global Seagrass Research Methods. Elsevier Science BV, Amsterdam, Netherlands, , 271-292, (2001).
Description:
The chapter describes methods to assess grazing rates, grazer preferences, and grazer impacts, by mobile organisms living in the canopy or in the rhizome layer in any seagrass system. One set of methods quantifies grazing activity in small to medium sized, mobile organisms living in the seagrass leaf stratum, and includes: a) gut content analysis, b) rate of ingestion, and c) evaluation of residual chlorophyll in the fecal pellets. Two approaches, feeding preference and plant consumption experiments, can be used to determine food selection preferences and relative rates of herbivory in individual species. Methods for image analysis of grazed surfaces and for assessment of abundance and feeding activity of organisms boring into both living and detrital seagrass tissues are also provided. Finally, designs for short-term field experiments on grazers are described. Small, sealed chambers enclosing individual plants may be appropriate for grazers such as smaller gastropods or crustaceans, while larger invertebrate grazers such as sea urchins may require pen type enclosures of much larger size. These methods can be used both to evaluate the ecology of individual grazers, and in combination, can lead to development of general models of the grazing food webs in seagrass ecosystems.