| The release of inorganic nutrients into the sea by domestic sewage is a major threat to many marine systems. This eutrophication affects coral-reef organisms indirectly by increased growth of microalgae, leading to increased sedimentation, decreased light availibility, rapid growth of opportunistic macroalgae, etc. In this paper, we report a decrease in the cover of important group of coral-reef builders, the coralline algae. This decrease might be caused by the outlets of sewage water from Zanzibar town. Laboratory and field experiments show that both the growth rate and the calcification of these organisms are negatively affected by high phosphate levels, but not by nitrate or ammonia. |
