Water, sediment, and productivity dynamics for Integrated Multi-Trophic Aquaculture development in Mauritius

Abstract

Aquaculture is essential for food security and economic sustainability, yet its environmental impacts must be carefully managed to protect coastal ecosystems. This study assessed water and sediment quality at an operational fish farm (Pointe-aux-Feuilles) and proposed lagoonal and off-lagoonal sites in Mauritius for Integrated Multi-Trophic Aquaculture (IMTA). Physico-chemical parameters, microbial loads, heavy metals, and productivity indicators were analyzed. Elevated ammonia (0.47 ± 0.02 mg L−1) and nitrate (2.50 ± 0.27 mg L−1) at MPAS1 indicated anthropogenic inputs. Nickel and manganese exceeded recommended limits at some sites, while other metals remained acceptable. Chlorophyll-a (0.28–2.97 mg m−3) and phytoplankton densities (9.6 × 103 −98.7 × 105 cells L−1) showed spatial variability in nutrient enrichment. Sediment organic carbon (0.39 ± 0.11%) and nitrogen (0.25 ± 0.13%) varied. The off-lagoon site at Trou aux Biches met most IMTA criteria, though low nutrient levels may require inputs, highlighting need for continuous monitoring and adaptive management.