Deviations in the biochemical structure of some macroalgal species and their relation to the environmental conditions in Qarun Lake, Egypt

Variations in the biochemical structure of seven macroalgal species, belonging to different families were investigated along with subsequent analysis of relevant water physico-chemical parameters. Samples were collected from different sites along the Egyptian Qarun Lake during spring of 2017. The relationship between the macroalgal components and ambient water parameters was studied. The results indicated that the macroalgal components differed according to plant species and spatial variations. The green macroalgae species Ulva fasciata was recorded at site 5. It was found to have the highest protein (20.66 ± 0.04%), DCP (15.67 ± 0.04%), P/NFE (0.65 ± 0.01%), P/EV 7.65 ± 0.03 mg crude protein/K cal GE and nitrogen contents (3.31 ± 0.01%). However Cladophora laetevirens collected from site7, had the highest lipid, ME, EV and K contents (3.64 ± 0.00%, 3.25 ± 0.00%, 3.99 ± 0.00 K cal/g and 0.40 ± 0.0%, respectively). Mougeotia genuflexa from site 4, had the highest ash content (53.58 ± 0.08%). Gracilaria corticata from site 6, had the highest NFE and OM contents (76.26 ± 0.15 and 89.68 ± 0.04% respectively) and Enteromorpha intestinalis collected from site 2 had the highest P/L value (11.71 ± 0.02%). Statistical analysis (CCA) showed that some environmental variables such as temperature, NO3, pH, COD and transparency had a strong effect on the macroalgal components and were considered as the most important water variables. While others such as DO, SiO3, NO2 and PO4, exhibited a weak correlation. The present study demonstrates differential response of the macroalgal components to the environmental variables. In addition to the importance of these macroalgal species as a balanced artificial fish and animal feeds, particularly Ulva fasciata, which have the highest nutritional components.