Techniques for quantitative sampling of infauna and epifauna in seagrass

This chapter describes recommended techniques for collecting quantitative samples of infauna and small epifauna for the determination of abundance and biomass. The fauna of seagrass beds can be classified based on where they live. Infauna lives within the bottom sediments and epifauna lives above the bottom, among the plant leaves and stems. The major kinds of quantitative sampling devices for infauna are grabs, corers, dredges, and suction samplers. Each includes a wide variety of different models and variations on the basic design. Several environmental characteristics typical of seagrass habitats contribute to the superiority of corers and suction samplers for quantitative sampling of the infauna. Although some species of seagrasses occur at water depths of 60 m or more, most species are restricted to much shallower depths. Hence, most seagrasses can be sampled with hand-held devices, such as corers or suction samplers while wading at low tide, or from a boat, or by divers. In contrast, many grabs and dredges are heavy, cumbersome devices that require a boat and winch for deployment. Ease of operation probably has been a major factor in the choice of corers over other methods. The combination of the environmental characteristics of seagrass beds (shallow waters, adequate visibility, and accessibility) and the structural and functional properties of a small beam net make it the most convenient sampler for small epifauna.