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AEI
Aquaculture Environment Interactions

    AEI prepress abstract   -  DOI: https://doi.org/10.3354/aei00341

    Dynamics and succession of phytoplankton communities in response to changing ammonium and nitrate levels in tropical shrimp ponds growing whiteleg shrimp Litopenaeus vannamei

    Veronica Fernandes, Elaine A. Sabu, Mamatha S. Shivaramu, Maria Judith B. D. Gonsalves, Rayadurga A. Sreepada*

    *Corresponding author:

    ABSTRACT: Optimal water quality is a prerequisite for the economic and environmental sustainability of shrimp aquaculture. The dynamics and succession of phytoplankton and microzooplankton assemblages and their inter-relationship with water-quality parameters in 2 commercial ponds growing the whiteleg shrimp Litopenaeus vannamei in south-western coastal India were assessed through periodic sampling during 96 d of culture. Of the many centric diatoms that were encountered during the initial stages of culture in nitrogen-rich conditions, only 2 dominant species, belonging to Thalassiosira, persisted throughout the progression of the culture to produce a healthy bloom (up to 6 × 106 cells l1). Blooms of Thalassiosira spp. contributed significantly to the increased phytoplankton biomass towards the end of culture period, with a concomitant decrease in concentrations of ammonia and nitrate. The succession of pennate diatoms such as Nitzschia closterium, Pleurosigma elongatum and Thalassionema nitzschoides in moderate abundance was also discernible. Results of canonical correspondence analyses revealed that the progression of diatom bloom, the emergence of dinoflagellates and the occurrence of intermittent blooms of the mixotrophic flagellate Eutreptiella marina were closely linked to factors such as higher temperature, salinity and phosphate concentration. Grazing by the herbivorous-bacterivorous ciliate communities may have controlled the blooms of undesirable groups of phytoplankton, ensuring better shrimp growth, higher survival and a lower food conversion ratio. Effective uptake of ammonium and nitrate by the blooming diatoms and phytoflagellates possibly prevented nutrient concentrations from reaching toxic levels, thereby generating an eco-friendly aquaculture water discharge into the adjacent ecosystem.