Abdul Wahab, M. A. | Search bioRxiv

bioRxiv2025

Unravelling the influence of light on inshore coral and sponge recruits and their substrate communities

Recruitment of progeny to coral reef populations involves complex ecological interactions, influenced by environmental factors such as altered underwater light conditions associated with poor water quality. Here, we exposed newly settled corals (Acropora millepora and Acropora cf. tenuis), the sponge (Phyllospongia foliascens), and their substrate communities to various light intensities and spectral profiles relevant to turbid inshore reefs. Coral and sponge recruit survivorship and growth generally exhibited an inverted U-shaped response to light intensity, suggesting environmental optima at lower light levels, while the influence of light spectra remained less clear within environmentally realistic treatment combinations. Crustose coralline algae cover similarly peaked at lower light levels, whereas turf algae increased with higher light conditions. Competitive interactions between the substrate communities and the recruits, along with photophysiological responses, were also assessed. Our results suggest that altered light characteristics associated with turbidity may not be as detrimental to coral and sponge recruits as other sediment-related stressors.

ecology↗

bioRxiv2020

Impacts of water quality on Acropora coral settlement: The relative importance of substrate quality and light

Coral larval settlement patterns are influenced by a vast array of factors; however, the relative roles of individual factors are rarely tested in isolation, leading to confusion about which are most crucial for settlement. For example, direct effects of light environment are often cited as a major determinate of settlement patterns, yet this has not been demonstrated under environmentally realistic lighting regimes in the absence of confounding factors. Here we apply programmable multispectral lights to create realistic light spectra, while removing correlating (but not obvious) factors that are common in laboratory settlement experiments. Using two common species of Acropora - key framework builders of the Great Barrier Reef - we find little evidence that light intensity or changes in the spectral profile play a substantial role in larval settlement under most environmentally realistic settings but can under more extreme or artificial settings. We alternatively hypothesise and provide evidence that chronic conditions of light and recent sediment exposures that impact benthic substrates (e.g., crustose coralline algae) preceding settlement have a greater impact, with up to 74% decrease in settlement observed on substrates with prior exposure and poor water quality conditions. Management of water quality conditions that impact the quality of benthic-settlement substrates therefore should present a priority area of focus for improving coral recruitment.

ecology↗