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

Gerard F Ricardo, Charlotte E Harper, Andrew P Negri, Heidi M Luter, Muhammad Azmi Abdul Wahab, Ross J Jones
2020 bioRxiv   pre-print
A vast array of factors are associated with coral larval settlement patterns; 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
more » ... ammable 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 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 substrates 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 settlement substrates therefore should present a priority area of focus for improving coral recruitment.
doi:10.1101/2020.11.19.390724 fatcat:a7o6jo6y35gvpn5ngz4qdn53uu