A Calcium Carbonate Budget Estimate for Maahutigalaa Reef Platform, Maldives

Abstract

This research investigates the production and removal of carbonate material on Maahutigalaa Reef Platform, Republic of Maldives. The results provide quantitative data on the morphology of the reef platform and ecological composition. A modified methodology of “Reefbudget” is used to estimate gross carbonate production and total biological erosion. Carbonate production and erosion have been examined to produce a biological calcium carbonate budget of Maahutigalaa Reef platform. A census-based approach on the relative abundance and distribution of carbonate producers is used to estimate gross carbonate production and investigate the relative importance of carbonate producers to the calcium carbonate budget. Primary data on the relative abundance and distribution of carbonate producing groups (primary and secondary) is used alongside regionally specific production rates. At a whole reef scale, gross carbonate production was estimated at 499004.01 kg CaCO3 y-1. Corals were the main contributor to carbonate production across the reef platform contributing 463174.57 kg CaCO3 y-1 (93%) to gross carbonate production, with the majority of production attributed to the massive growth morphology. Secondary carbonate production contributed 35829.44 kg CaCO3 y-1 (7%) to reef-wide gross carbonate production. Biological erosion was estimated using a census-based approach on the relative abundance and distribution of bioeroders along with published bioerosion rates for parrotfish, urchins, microborers and macroborers. At a whole reef scale, bioerosion was estimated at 326416.12 kg CaCO3 y-1. Rates of gross carbonate production minus total bioerosion were used to determine the net biological carbonate budget for Maahutigalaa reef platform. Net biological carbonate production for Maahutigalaa is estimated at +172588.88 kg CaCO3 y-1. The data within this thesis was collected following the ENSO-induced warming experienced in the central Indian Ocean from late March to mid May 2016. The calcium carbonate budget produced for Maahutigalaa has been compared to other studies conducted on various spatial and temporal scales. The findings therefore add to the dataset of budget studies available for central Indian Ocean reefs and Maldivian reefs, and furthermore allows the examination of the implications of changing environmental conditions upon carbonate budgets, and how these may impact on the ability of reefs to maintain their morphological and ecological integrity.