Nutrient-rich submarine groundwater discharge increases algal carbon uptake in a tropical reef ecosystem

Submarine groundwater discharge (SGD) in high volcanic islands can be an important source of freshwater and nutrients to coral reefs. High inorganic nutrient content is generally thought augment primary production coastal systems but when this delivered via a vector as the case with SGD study, effects on productivity are unclear. In current literature, there limited evidence for direct association between To elucidate response SGD, we conducted spatially temporally explicit situ benthic chamber experiments reef flat along gradient SGD. We found significant quadratic relationships C-uptake both phytoplankton most abundant macroalga, Gracilaria salicornia , uptake maxima at SGD-derived salinities ~21−22 (24.5−26.6 μmol NO 3 -L −1 ). These results suggest physiological tradeoff salinity tolerance availability producers. Spatially modeling reefs without indicate reef-scale G. decreased by 82% 36% absence respectively. Thus, nutrient-rich low has algal systems.