Seasonal Dynamics and Vertical Distribution of Phosphorus in Sediments Under Trout Сage Farms in Lake Ladoga

This study focuses on the seasonal dynamics and vertical distribution of phosphorus in the sediments of trout cage farms in Lake Ladoga, Russia. With the burgeoning development of aquaculture, assessing the environmental impact of this practice is crucial. The fieldwork was conducted at two farms, where sediment cores were collected for layer-by-layer laboratory analyses. Chemical parameters such as the Red/Ox potential (Eh), phosphorus content (organic and inorganic forms), and organic matter percentage were measured to understand their influence on geochemical behavior of phosphorus. The findings revealed increases in organic matter and phosphorus content during the active feeding periods. Inorganic compounds of phosphorus, primarily from fish feed, was the predominant form of the element entering the sediments. It was shown that reducing conditions exist in the sediments under the studied cages. Thus, anoxic Red/Ox environment can contribute to phosphorus release into the water column from polluted sediments. At the reference sampling sites, no accumulation of organic wastes and phosphorus was observed, which suggests a local spatial impact of fish farming on sediment quality. The results obtained are important for developing sediment monitoring strategies to mitigate the environmental footprint of trout farming in Lake Ladoga.