Preliminary assessment of water quality post-the first phase of the development plans in Lake Burullus, Deltaic coast of the Mediterranean Sea, Egypt

Abstract

Lake Burullus is the second largest lake in Egypt and a Ramsar site located north of the Nile Delta. The lake is connected to the Mediterranean Sea through the Burullus inlet and the River Nile through Brimbal Canal. Lake Burullus receives a large amount of agricultural drainage water (about 97% of its water balance), which affects its water quality. The national plan, launched in 2017, aimed to improve the condition, water quality, and fish production of Lake Burullus. The current study provides an effective protocol to monitor the water quality of Lake Burullus post the first phase of the national plan. Aglydopting the proposed protocol would enable researchers and managers to evaluate the effectiveness of the development plans in resolving the environmental problem facing Lake Burullus and similar lakes. Intensive sampling was carried out in December 2019 and October 2020 to collect ecological parameters. The results showed a general improvement in the lake water indicated by the phytoplankton composition and diversity. Compared to previous research, the current study recorded a lower number of species belonging to Chlorophyceae and Cyanophyceae and new records of marine species belonging to Dinophyceae. The changes in phytoplankton community structure were mainly due to the deepening of the seawater inlet which has resulted in a better exchange between seawater and the lake and a subsequent increase in salinity. Based on TSIChl-a, the lake has shifted from being predominantly hypereutrophic to eutrophic. Nutrient-load reduction strategies for Lake Burullus may result in measurable changes in trophic state parameters.