Eutrophication assessment using TRIX and Carlson’s indices in lake mariout water, Egypt

Abstract

Eutrophication of coastal waters is considered one of the major threats in marine ecosystems. Therefore, continuous monitoring is urgently needed to define potential risk zones. The present study is an attempt to test the applicability of the trophic state indices (TRIX) and Carlson’s indice for scaling the eutrophication status of Lake Mariout in concert with a number of physicochemical descriptors aimed to select the most relevant of their ecological quality directed to increase fish production. Water samples were investigated seasonally during 2014. The range and annual average values of Physicochemical parameters were 18-27.5°C (23.20±0.52°C) for Temperature; 0.28- 7.40‰ (3.70‰±1.69‰) for Salinity; 7.84-8.84 for pH; 0.60 - 5.24meq/l (1.97 ±0.43meq/l) for Total alkalinity; 0.14-10.71mg/l (4.91±2.98mg/l) for DO; 0.01-2.6mg/l (1.35±0.32mg/l) for BOD; 3.2-134.4mg/l (56.35±27.89 mg/l) for OOM; and 16.30- 161.00 mg/l (63.80±24.70) for Total suspended solids;. The results of nutrient salts range and mean concentration (µM) were from 0.20 to 118.30 (15.61±15.46) for Ammonium; from 0.05 to 22.48 (3.43±3.38) for Nitrite; from 0.14 to 66.67 (13.50±7.78) for Nitrate; from 0.39 to 157.26 (39.28±43.79) for DIN; from 0.32 to 123.55 (33.64±18.77) for total nitrogen; from 0.10 to 45.30 (8.27±10.28) for reactive phosphate; from 0.04 to 49.60 (7.98±6.93) for total phosphorus; and from 2.14 to 226.16 (39.97±21.85) for silicate. Chlorophyll-a ranged from 3.95 to 130.3µg/l (28.51±21.99µg/l). According to seasonally calculated TRIX and Carlson’s trophic state indices values, the sites are ranked in a descending order from very high to moderate eutrophic level for most stations, revealing the existence of anthropogenic stress.