Assessing the Impact and Spatial Pattern of Diffusion of Nutrient from Cage Culture by Using CORMIX Modeling in the Coastal Ecosystem of the Caspian Sea

Abstract

Aquaculture contributes to elevated levels of phosphates and nitrates in both water and sediment, leading to reduced biodiversity and a proliferation of pollution-resistant organisms. One significant challenge in developing effective management strategies is the lack of accurate predictions regarding the dispersion and distribution of pollutants. Consequently, modeling water quality and pollutant distribution is crucial for evaluating these impacts. This study aims to spatially model nutrient release from fish breeding cages in the Sisangan region and assess its impact on water quality using the CORMIX numerical model. Conducted in November 2019 in the Caspian Sea, Mazandaran province, the research involved nine sampling stations. Physicochemical parameters were measured using a Conductivity-Temperature-Depth (CTD) device. Nutrient samples, including nitrogen and phosphorus compounds, were collected with a Niskin bottle and analyzed in the laboratory. Field sampling revealed an average TRIX index of 2.3, indicating oligotrophic water conditions but an elevated trophic state. Modeling results demonstrated that nitrogen and phosphorus concentrations decrease with increasing distance from the fish cages. The findings suggest a potential shift from oligotrophic to mesotrophic conditions due to the increased nutrient load from fish farming activities. This underscores the importance of understanding and managing the environmental impacts of marine aquaculture on water quality and ecosystem health. Effective management strategies must be developed to mitigate these impacts and ensure sustainable aquaculture practices.