Protozoans and Meiofauna Inhabiting a Bead Filter: A Preliminary Investigation of Their Role as Potential Bioindicators of Shrimp Production System Health

Abstract.— Protozoans are used as bioindicators of system health in wastewater treatment plants. The objective of this study was to determine if protozoans or meiofauna could be useful bioindicators of shrimp production system health. Specifically, we noted the relative abundance of protozoans and meiofauna inhabiting a propeller-washed bead filter (PBF) used in a recirculating aquaculture system for intensive shrimp production during a 12-wk grow-out trial. Based on microscopic analysis of PBF backwash, results indicate that (1) the presence of nematodes and rotifers may reflect the age and/or organic loading of the filter; (2) feed quantity affects protozoan biomass, whereas feed quality impacts the nutritional group of protozoans that survive; (3) free-living amoeba typically are surface associated in their active feeding state and were present in most PBF samples; and (4) ciliates likely play an important ecological role in PBF used in intensive shrimp culture.