Figure 4.

Mesocosm experiments measuring the response of corals and algal-covered rubble to iron enrichment. (a) P. meandrina corals were treated with 1 μ ferric iron (FeCl₃) with and without the presence of black reef algae. The same treatments were conducted plus 50 μg ml⁻¹ ampicillin. Coral fragments and mesocosms were photo documented after 5 days (4 of 8 treatments shown, n=10). (b) Coral condition was visually assessed (top panel). The concentration of DO (mg O₂ l⁻¹) in the aquarium water was measured at the completion of the experiment (middle panel). The rate of change in DO (mg O₂ l⁻¹ h⁻¹) was also measured (bottom panel). Fe, ferric iron; Amp, ampicillin. (c) Photographs of iron-enriched mesocosms depicting water turbidity (1) and the formation of black particulate material characteristic of the black reef (2). Cross-section of algal-covered rubble collected from the Millennium black reef (3).