Comparison of Phytoplankton Communities in Catfish Split-Pond Aquaculture Systems with Conventional Ponds

摘要

There has been a growing interest and use of variations of partitioned aquaculture systems (PAS) in recent years by the southeastern U.S. catfish farming industry. Split-pond systems, one type of PAS, are designed to better manage fish waste byproducts (e.g., ammonia) and dissolved oxygen levels than the conventional earthen ponds that have been used by farmers for many decades. Recent studies have focused on design, water flow rates, and other management areas of catfish split-ponds, but so far there has not been a focused examination of phytoplankton community composition and biomass in these split-ponds. In the current study, pond water samples were collected from split-ponds at a research facility in western Mississippi and at a commercial fish farm in western Alabama approximately every 3 weeks during the fish grow-out period (May to November). Water samples were analyzed for chlorophyll a concentration (phytoplankton biomass) of several major phytoplankton divisions and for types of phytoplankton and their abundance. Overall, chlorophyll a concentrations in the split-ponds were maintained within the typical range (0-800 mu g/L) found in non-PAS (conventional) catfish ponds. The phytoplankton communities in split-ponds were dominated by cyanobacteria or blue-green algae (Cyanophyta) and by the same common species of cyanobacteria (e.g., Planktothrix agardhii, P. perornata, Microcystis aeruginosa, Raphidiopsis brookii) reported in previous studies for conventional catfish ponds. In addition, many types of phytoplankton in the other major divisions-Chlorophyta (green algae), Bacillariophyta (diatoms), Chrysophyta (golden brown algae), Cryptophyta (cryptomonads), Euglenophyta (euglenophytes), and Pyrrhophyta (dinoflagellates)-present in the split-ponds were the same as those reported previously in conventional catfish ponds. Therefore, issues related to management practices for pond water quality (e.g., dissolved oxygen) and undesirable cyanobacteria are expected to be similar to those used for conventional ponds.