Habitat‐specific biogenic production and erosion influences net framework and sediment coral reef carbonate budgets

Abstract

AbstractCarbonate budgets are increasingly being used as a key metric to establish reef condition. To better understand spatial variations in framework and sediment net carbonate budgets, we quantified biogenic carbonate production, erosion, and dissolution within and between five distinct geomorphological habitats of Heron Reef on the southern Great Barrier Reef. The protected reef slope had the greatest estimated net framework carbonate budget (22.6 kgCaCO3 m−2 yr−1 ± 2.4 SE), driven by abundant, fast‐growing acroporid corals coupled with low levels of macro‐ and micro‐bioerosion. The estimate of the exposed reef slope was significantly lower due to localized damage from a single tropical cyclone that occurred 7 years prior to this study (9.7 kgCaCO3 m−2 yr−1 ± 2.8 SE). Within the extensive lagoon, net framework carbonate budgets ranged from 0.24 kgCaCO3 m−2 yr−1 (± 0.1 SE) to 3.0 kgCaCO3 m−2 yr−1 (± 0.7 SE). The greatest net sediment carbonate budget was estimated within the reef crest (6.0 kgCaCO3 m−2 yr−1 ± 1.1 SE) and the lowest in the shallow lagoon (1.2 kgCaCO3 m−2 yr−1 ± 0.2 SE). Chemical dissolution of the sediments exhibited spatial variability, with reef crest and reef flat sediments in a state of net production. Considering the area of each habitat, the net reef framework and sediment budgets across Heron Reef were 4.06 kgCaCO3 m−2 yr−1 and 2.82 kgCaCO3 m−2 yr−1, respectively. The results of this study improve our understanding of spatial variability in carbonate production and bioerosion and provide a comprehensive reef‐scale carbonate budget for a relatively undisturbed coral reef ecosystem.