Data from: Nutrient pollution disrupts key ecosystem functions on coral reefs

There is a long history of examining the impacts of nutrient pollution and
pH on coral reefs. However, little is known about how these two stressors
interact and influence coral reef ecosystem functioning. Using a six-week
nutrient addition experiment, we measured the impact of elevated nitrate
(NO3) and phosphate (PO43) on net community calcification (NCC) and net
community production (NCP) rates of individual taxa and combined reef
communities. Our study had four major outcomes: 1) NCC rates declined in
response to nutrient addition in all substrate types; 2) the mixed
community switched from net calcification to net dissolution under medium
and high nutrient conditions; 3) nutrients augmented pH variability
through modified photosynthesis and respiration rates; and 4) nutrients
disrupted the relationship between NCC and aragonite saturation state
documented in ambient conditions. These results indicate that the negative
effect of NO3 and PO43 addition on reef calcification is likely both a
direct physiological response to nutrients and also an indirect response
to a shifting pH environment from altered NCP rates. Here, we show that
nutrient pollution could make reefs more vulnerable to global changes
associated with ocean acidification and accelerate the predicted shift
from net accretion to net erosion.