Effects of Nile Tilapia (Oreochromis niloticus) on phytoplankton community structure and water quality: a short-term mesocosm study

Abstract

Nile tilapia is a highly invasive fish species, deliberately introduced into many lakes and reservoirs worldwide, sometimes resulting in significant ecosystem alterations. A short-term mesocosm experiment with and without Nile tilapia (Oreochromis niloticus) was designed to test the hypotheses that the presence of tilapia may affect phytoplankton community structure, increase nutrients availability in water column and deteriorate water quality. Nutrients, total suspended solids (TSS) and biomass of phytoplankton in different size classes (as Chl a) were measured. We found that tilapia increased the total nitrogen (TN), total dissolved nitrogen (TDN), NH4 + and TSS concentrations, deteriorating the water quality. In addition, under tilapia presence, the biomass of phytoplankton, as well as that of micro- and nano-phytoplankton, increased leading to a change in the structure of the phytoplankton assemblage. Moreover, a reduction in the biomass of periphyton was observed. Omnivorous tilapia is often dominant in tropical and subtropical waters, and removal of this fish may represent an effective management tool to improve the water quality.

Assessment of Growth, Reproduction, Recruitment and Virtual Population Analysis of Invasive Species, Coptodon zilllii in Garmat Ali River, Iraq

“…The impacts of cichlids introduced on native fish and their habitats were well documented [3]. Tabasian et al [8] stated that C. zillii may compete for food and space with the native fish species and remove macrophytes and phytoplankton, which leads to ecosystem-level changes in the wetland. Also, the cichlids are little desired by the Iraqis compared to exotic and indigenous cyprinids.…”