Nutrient Loading and Phytoplankton Responses to Open-Sea Cage Farming of Mud Spiny Lobster (Panulirus polyphagus)
Mayur Shivdas Tade
Kerala University of Fisheries and Ocean Studies, Panangad Road, Madavana Junction, Kochi, Ernakulam, Kerala 682-506, India and Indian Council of Agricultural Research-Central Marine Fisheries Research Institute (ICAR-CMFRI), North P.O, Abraham Madamakkal Road, Ernakulam, Ayyappankavu, Kochi-682 018, Kerala, India.
Suresh Kumar Mojjada
Indian Council of Agricultural Research-Central Marine Fisheries Research Institute (ICAR-CMFRI), North P.O, Abraham Madamakkal Road, Ernakulam, Ayyappankavu, Kochi-682 018, Kerala, India and Indian Council of Agricultural Research- National Academy of Agricultural Research Management (NAARM), Rajendranagar, Hyderabad, Telangana 500 030, India.
Swathi Lekshmi Perumal Sundaram
Indian Council of Agricultural Research-Central Marine Fisheries Research Institute (ICAR-CMFRI), North P.O, Abraham Madamakkal Road, Ernakulam, Ayyappankavu, Kochi-682 018, Kerala, India.
T. S. Ramshad
Indian Council of Agricultural Research-Central Marine Fisheries Research Institute (ICAR-CMFRI), North P.O, Abraham Madamakkal Road, Ernakulam, Ayyappankavu, Kochi-682 018, Kerala, India.
Mayank Soni
Kerala University of Fisheries and Ocean Studies, Panangad Road, Madavana Junction, Kochi, Ernakulam, Kerala 682-506, India.
Boby Ignatius
Indian Council of Agricultural Research-Central Marine Fisheries Research Institute (ICAR-CMFRI), North P.O, Abraham Madamakkal Road, Ernakulam, Ayyappankavu, Kochi-682 018, Kerala, India.
Achamveetil Gopalakrishnan
Indian Council of Agricultural Research-Central Marine Fisheries Research Institute (ICAR-CMFRI), North P.O, Abraham Madamakkal Road, Ernakulam, Ayyappankavu, Kochi-682 018, Kerala, India.
Damodaran Divu *
Indian Council of Agricultural Research-Central Marine Fisheries Research Institute (ICAR-CMFRI), North P.O, Abraham Madamakkal Road, Ernakulam, Ayyappankavu, Kochi-682 018, Kerala, India.
*Author to whom correspondence should be addressed.
Abstract
The rapid expansion of offshore mariculture has raised concerns regarding nutrient enrichment and its ecological impacts on coastal ecosystems. Among emerging mariculture practices, open-sea cage culture of mud spiny lobster (Panulirus polyphagus) has gained increasing importance along the Indian coast; however, information on nutrient budgets and ecological responses remains limited. This study quantified nitrogen (N) and phosphorus (P) loading associated with lobster cage farming and evaluated phytoplankton responses in the north-eastern Arabian Sea off Veraval, Gujarat. Nutrient budgets were estimated using a mass-balance approach, while phytoplankton abundance and nutrient concentrations were monitored throughout the culture cycle. Approximately 88.9% of nitrogen and 89.3% of phosphorus supplied through feed were released into the surrounding environment, with only a small proportion retained in lobster biomass. Mean phytoplankton abundance was 2.01 × 10⁵ ± 1.21 × 10⁴ cells L⁻¹, with diatoms consistently dominating the community. Although nutrient discharge increased progressively with farming activity, no signs of eutrophication, harmful algal blooms, or ecological deterioration were observed. Nitrate exhibited the strongest positive association with phytoplankton abundance, suggesting a potential role of nitrogen availability in regulating primary productivity. The results suggest that efficient hydrodynamic flushing promotes nutrient dispersion and assimilation, enabling the receiving ecosystem to accommodate nutrient inputs at the current production scale. This study provides valuable baseline information for ecosystem-based environmental monitoring and the sustainable expansion of offshore lobster mariculture in the Arabian Sea.
Keywords: Nutrient budget, Phytoplankton, Lobster mariculture, environmental sustainability, coastal ecosystem, Panulirus polyphagus.