World Aquaculture Society Meetings

Measuring the Effects of Recycled Water on the Growth of Three Algal Species:  Tisochrysis lutea, Chaetocerous calcitrans and C. muelleri in a large-scale oyster hatchery

Lisa M. Bourassa* and John E. Supan
Sea Grant Oyster Research Laboratory
Louisiana Sea Grant College Program
Louisiana State University
133 LSU Drive
Grand Isle, LA 70358
lbourassa@lsu.edu

Algal production is often the limiting factor in large scale oyster hatcheries requiring moderate, consistent temperatures and good water quality to grow enough algae to support all oyster larvae and broodstock grown and conditioned in the hatchery. The algal rooms in the Michael C Voisin Oyster hatchery in Grand Isle, LA are temperature controlled to maintain consistent temperature, but this hatchery is unique in its ability to recycle natural seawater pumped into the hatchery from Barataria Bay. Recycling seawater will be used in times of low salinities and poor water quality due to a high influx of freshwater from the Mississippi River, and during hurricane evacuations. However, effects of recycling seawater on algal production are unknown.

In this study, Tisochrysis lutea, Chaetoceros calcitrans and C. muelleri will be grown in F/2 media using different water sources at the oyster hatchery to mimic "recycled" water conditions. These sources of water include: 1) a control; "normal" operating conditions (natural seawater from Barataria Bay filtered to 1 micron nominal and "polished" with bead filtration), 2) Instant Ocean® artificial seawater mixed with reverse osmosis water that is chemically very similar to natural seawater, and 3) water from our continuous oyster system discharge that will be treated as if under "recycling" conditions (soda ash to adjust the pH, protein skimmer and filtered to 1 micron nominal).  Cell counts, dry biomass, nitrate, total nitrogen, total phosphate, and total silicate concentration will be measured. Results from this study will be presented.  

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