DOI: 10.5061/dryad.19kd421
title: Data from: Coral reef carbonate budgets and ecological drivers in the central Red Sea – a naturally high temperature and high total alkalinity environment

description: The structural framework provided by corals is crucial for reef ecosystem
 function and services, but high seawater temperatures can be detrimental
 to the calcification capacity of reef-building organisms. The Red Sea is
 very warm, but total alkalinity (TA) is naturally high and beneficial for
 reef accretion. To date, we know little about how such detrimental and
 beneficial abiotic factors affect each other and the balance between
 calcification and erosion on Red Sea coral reefs, i.e., overall reef
 growth, in this unique ocean basin. To provide estimates of present-day
 reef growth dynamics in the central Red Sea, we measured two metrics of
 reef growth, i.e., in situ net-accretion/-erosion rates (Gnet) determined
 by deployment of limestone blocks and ecosystem-scale carbonate budgets
 (Gbudget), along a cross-shelf gradient (25km, encompassing nearshore,
 midshore, and offshore reefs). Along this gradient, we assessed multiple
 abiotic (i.e., temperature, salinity, diurnal pH fluctuation, inorganic
 nutrients, and TA) and biotic (i.e., calcifier and epilithic bioeroder
 communities) variables. Both reef growth metrics revealed similar patterns
 from nearshore to offshore: net-erosive, neutral, and net-accretion
 states. The average cross-shelf Gbudget was 0.66kg CaCO3m−2yr−1, with the
 highest budget of 2.44kg CaCO3m−2yr−1 measured in the offshore reef. These
 data are comparable to the contemporary Gbudgets from the western Atlantic
 and Indian oceans, but lie well below optimal reef production (5–10kg
 CaCO3m−2yr−1) and below maxima recently recorded in remote high coral
 cover reef sites. However, the erosive forces observed in the Red Sea
 nearshore reef contributed less than observed elsewhere. A higher TA
 accompanied reef growth across the shelf gradient, whereas stronger
 diurnal pH fluctuations were associated with negative carbonate budgets.
 Noteworthy for this oligotrophic region was the positive effect of
 phosphate, which is a central micronutrient for reef building corals.
 While parrotfish contributed substantially to bioerosion, our dataset also
 highlights coralline algae as important local reef builders. Altogether,
 our study establishes a baseline for reef growth in the central Red Sea
 that should be useful in assessing trajectories of reef growth capacity
 under current and future ocean scenarios.
description: Carbonate Budgets
 Central Red SeaData files contain the
 measurements of physicochemical variables, reef census, and reef growth
 data from a monitoring study conducted in the coral reefs of the central
 Red Sea in 2014. Monitoring stations were located at depths between 7 - 9
 m, where loggers were deployed 1 - 1.5 m from the reef benthos. Data was
 collected from a nearshore reef (at 3 km distance from shore), a midshore
 reef (at 10 km distance from shore), and an offshore reef (at 25 km
 distance from shore). These data were use to describe carbonate budgets
 and eco-environmental drivers in the coral reefs of the central Red Sea.
 Please refer to the Materials & Methods section of the research
 article Roik et al. 2018 (Biogeosciences) for more
 details.