Improvement of a rotifer ecosystem culture to promote recycling marine microalga, nannochloropsis sp.

An ecosystem culture with a consumer-producer relationship based on the cycle of substances in the, natural ecosystem was constructed in order to study the feasibility of economical cultivation of the marine microalga Nannochloropsis sp, in rotifer waste water. To promote algal growth, the following points were investigated to determine: (1) whether micronutrients necessary for Nannochloropsis culture are generated by rotifers, (2) the favorable and optimal ranges of nutrient concentrations in aged rotifer culture water involved in the optimal growth of Nannochloropsis sp., and (3) the suitability of some economical organic fertilizers in rotifer waste water at earlier stages. In new rotifer waste water, the growth of Nannochloropsis was equal to that in enriched sea water with Enriched Sea Water Provasoli (ESP) nutrients. Micronutrients could be recycled rapidly through feeding and excretion of rotifers. Using aged rotifer waste water, the maximum cellular density was obtained in a waste water with nitrogen and phosphorus concentrations of 364 and 179 mu g at. l(-1), respectively. This growth was 23% higher than that obtained in enriched sea water with ESP nutrients (control). On the other hand, the organic fertilizers used in this experiment (chicken manure extract and decomposed shark meat) were found to be suitable for enhancing growth of Nannochloropsis sp. in rotifer waste water at earlier stages. The use of chicken manure with an additional inorganic nitrogen source to rotifer waste water resulted in a 50% increase in cellular density of Nannochloropsis sp. compared with that obtained in the control. However, addition of decomposed shark meat to rotifer waste water led only to a 20% increase. (C) 1998 Elsevier Science B.V.