Relationship of internal macrobioeroder densities in living massive Porites to turbidity and chlorophyll on the Australian Great Barrier Reef

Abstract

This study investigates the relationship between the density of internal macrobioeroders in living massive Porites and nutrient status. The study was conducted along turbidity and chlorophyll gradients towards river mouths on 12 reefs in four regions of the inshore Great Barrier Reef. Mean internal macrobioeroder densities doubled from 2 to 8 m depth, and at the 8 m sites, densities increased 4-to 7-fold towards the river mouths in all regions. Densities also increased 1.6-fold for each additional 1 NTU turbidity and 650-fold per 1 lg L -1 additional chlorophyll a. The study shows that the density of macrobioeroder boreholes in living massive Porites is a simple bioindicator measure for changing turbidity and chlorophyll concentrations on the Great Barrier Reef for sites from which direct water quality measurements are unavailable.

Effects of submarine groundwater discharge on coral accretion and bioerosion on two shallow reef flats

“…This indicates that bioerosion is less sensitive to low salinities than coral growth, and that SGD‐derived nutrients likely increase bioerosion rates until nutrients become saturating or conditions become stressful, at which point bioerosion rates plateau. This is consistent with previous studies that have noted increased bioerosion with increasing nutrients (Edinger et al ; Holmes 2000; Le Grand and Fabricius ). Studies that have assessed bioerosion rates in the Hawaiian Archipelago have found the highest bioerosion rates at Kahekili, Maui, a site with a significant influx of nutrient‐rich SGD (Prouty et al ; Silbiger et al ), indicating that the relationship between SGD and bioerosion in the current study is not a localized phenomenon.…”

A bioindicator system for water quality on inshore coral reefs of the Great Barrier Reef

“…In colonies smaller than the quadrat, the five deepest grooves on the entire colony were measured. -The density of externally visible apertures of macrobioeroders was determined on upward facing surfaces with living tissue (Cooper et al, 2008;LeGrand and Fabricius, 2011). In Study 1, colonies >1 m were sub-sampled in 3 replicate 25 Â 25 cm quadrats, while colonies <1 m in diameter were counted in total after determining their living surface area.…”

Environmental drivers of coral reef carbonate production and bioerosion: a multi‐scale analysis

“…). In several field studies, bioerosion increased in eutrophic relative to oligotrophic conditions (e.g., Le Grand and Fabricius , DeCarlo et al. ), likely due to increased food availability to filter feeding bioeroders.…”

“…) and local eutrophication (e.g., Fabricius , Hutchings et al. , Le Grand and Fabricius ). These stressors threaten to shift reefs from a state of net accretion to net erosion.…”

“…Corals and other calcifiers (e.g., non-coral encrusting invertebrates and crustose coralline algae [CCA]) build reefs through the production of calcium carbonate (CaCO 3 ) skeletons, while a diverse community of organisms bioerode reefs through grazing on (e.g., urchins, parrotfish) and boring into (e.g., boring sponges, sipunculids, and polychaetes) CaCO 3 reef substrate (e.g., Hutchings 2011, Tribollet andGolubic 2011). Anthropogenic stressors affect the accretion-erosion balance of coral reefs at a range of spatial scales from global ocean acidification (e.g., Hoegh- Guldberg et al 2007, Silbiger andDonahue 2015) to regional overfishing (e.g., Brown-Saracino et al 2007, Kennedy et al 2013) and local eutrophication (e.g., Fabricius 2005, Hutchings et al 2005, Le Grand and Fabricius 2011.…”