Andreas F. Haas

Benthic community composition affects O2 availability and variability in a Northern Red Sea fringing reef

Many coral reef ecosystems experience shifts in benthic community composition from scleractinian corals to algae. However, consequences of such phase shifts on O2 availability, important for many reef organisms, are unresolved. This study therefore comparatively investigated potential in situ effects of different benthic cover by reef macroalgae and scleractinian corals on water column O2 concentrations in a Northern Red Sea fringing reef. Findings revealed that mean daily O2 concentrations at algae-dominated sites were significantly lower compared to coral-dominated sites. Minimum O2 concentrations were significantly negatively correlated, while diurnal variability in O2 concentration was significantly positively correlated, with increasing benthic cover by algae. In contrast, no correlation with coral cover was found. These results indicate that shifts from corals to benthic algae may likely affect both in situ O2 availability and variability. This may be particularly pronounced in reef systems with low water exchange (e.g. closed lagoons) or under calm weather conditions and suggests potential O2-mediated effects on reef organisms.

Crown of thorns of Daphnia: an exceptional inducible defense discovered by DNA barcoding.

DNA barcoding has emerged as valuable tool to document global biodiversity. Mitochondrial cytochrome oxidase I (COI) sequences serve as genetic markers to catalog species richness in the animal kingdom and to identify cryptic and polymorphic animal species. Furthermore, DNA barcoding data serve as a fuel for ecological studies, as they provide the opportunity to unravel species interactions among hosts and parasites, predators and prey, and among competitors in unprecedented detail. In a recent paper we described how DNA barcoding in combination with morphological and ecological data unraveled a striking predator-prey interaction of organisms from temporary aquatic habitats, the predatory notostracan Triops and its prey, cladocerans of the Daphnia atkinsoni complex.