Patterns of microbial activity in the shallow bottom sediments of Lake Manzala, Egypt

Abstract

General microbial activity, determined by hydrolysis of fluoresceine diacetate (FDA), was investigated in two sediment cores collected from Manzala Lake during November 2011. FDA hydrolysis positively correlated with total bacterial counts, bacterial biomass and chlorophyll a in both cores. The 10–20 cm subsurface layer in both cores had higher bacterial counts (2.03 x 10⁶ and 1.6 x 10⁶ cells g^–1) and a higher V_max (kinetic parameter of esterase activity; 177.8 and 117.8 µmol g^–1 h^–1), respectively, than the top 0–10 cm. In both cores the upper 40 cm had not received any Nilotic sediments, which may account for the atypical vertical profiles observed.

Keywords:

• bacteria
• chlorophyll a
• enzyme activity
• pheophytin