Analysis of the causes of N/P imbalance in mangrove water caused by high elevation shrimp ponds

Due to its unique estuarine location at the junction of land and sea, mangrove wetlands are surrounded by numerous high-elevation shrimp ponds. The high-elevation shrimp ponds around the mangrove forest undergo 2.3 clearances by quicklime (CaO) disinfectant per year in China, but the impact of the quicklime disinfectant used and emitted on the mangrove wetland ecosystem is seriously underestimated. Due to the relatively limited data provided by high-elevation shrimp pond aquaculture in estuarine areas for the mangrove ecosystem, this study established an algorithm for calculating the reaction rate of quicklime disinfectants used in high-elevation shrimp pond aquaculture, which is the fundamental reason for the imbalance of N/P ratio in mangrove wetlands. Results showed that the amount of Ca(OH)₂ produced by quicklime during the initial cleaning of the shrimp pond was 1303.4 t/a. The annual consumption of Ca(OH)₂ by organic acids, strong chlorine disinfectants, and TP in the marine system was 154.6–171.5 t, 1.7 t, and < 284.5 t, respectively. The lack of phosphorus and the imbalance of N/P ratio caused by quicklime disinfectants may be a factor in the changes of mangrove wetlands and surrounding nearshore waters, the growth and decline of marine species, and even global changes.