Palaeoecological records of coral community development on a turbid, nearshore reef complex: baselines for assessing ecological change

Abstract

Understanding past coral community development and reef growth is crucial for placing contemporary ecological and environmental change within appropriate reef-building timescales. On Australia's Great Barrier Reef (GBR), coral reefs situated within coastal inner-shelf zones are a particular priority. This is due to their close proximity to river point sources, and therefore susceptibility to reduced water quality discharged from coastal catchments, many of which have been modified following European settlement (ca. 1850 AD). However, the extent of waterquality decline and its impacts on the GBR's inner-shelf reefs remain contentious. In this study, palaeoecological coral assemblage records were developed for five proximal coral reefs situated within a nearshore turbid-zone reef complex on the central GBR. A total of 29 genera of Scleractinia were identified from the palaeoecological inventory of the reef complex, with key contributions to reef-building made by Acropora, Montipora, and Turbinaria. Discrete intervals pre-and post-dating European settlement, but associated with equivalent water depths, were identified using Bayesian age-depth modelling, enabling investigation of competing ideas of the main drivers of nearshore coral assemblage change. Specifically, we tested the hypotheses that changes in the composition of nearshore coral assemblages are: (1) intrinsically driven and linked to vertical reef development towards sea level, and (2) the result of changes in water quality associated with coastal river catchment modification. Our records found no discernible evidence of change in the generic composition of coral assemblages relative to European settlement. Instead, two distinctive depth-stratified assemblages were identified. This study demonstrates the robust nature of nearshore coral communities under reported water-quality decline and provides a useful context for the monitoring and assessment of ecological change on reefs located within the most nearshore turbidzone environments of the central GBR.

High coral reef connectivity across the Indian Ocean is revealed 6–7 Ma ago by a turbid-water scleractinian assemblage from Tanzania (Eastern Africa)

“…4, 5) (e.g. Stafford-Smith and Ormond 1992; Stafford-Smith 1993; Riegl et al 1996; Tomascik et al 1997; Wilson et al 2005; Sofonia and Anthony 2008; Browne et al 2012; Bessell-Browne et al 2017; Johnson et al 2017) points to a significant terrigenous influx. Furthermore, many coral colonies in the studied outcrop show growth features related to high, episodic sediment accumulation.…”

Projections of coral cover and habitat change on turbid reefs under future sea-level rise

“…By approximately 200 yrs BP, reefs transitioned to rapid rates of vertical reef growth (5.1 ± 4 to 6.9 ± 9.4 mm yr −1 ) as they reached water depths between 1.5 and 3.5 m, and fast-growing coral taxa (e.g. foliose Montipora and Turbinaria, branching Acropora) became more abundant [14,16]. Shore-attached reefs (e.g.…”

Environmental impact on the mechanical properties of Porites spp. corals

“…As numerous paleoclimate studies have been performed using massive Porites, chemical composition and age-modeling methods are well-established (Allison and Finch 2010;LaVigne et al 2016;Tanzil et al 2016;Murty et al 2018). Porites are an important reef-building coral that are found globally on coral reefs (Vernon 2000), as well as in the underlying reef substrate (Johnson et al 2017). However, despite their importance as a reef-building genus, and their widespread use in coral science, the mechanical properties of Porites have never been measured at the nanoscale.…”