Abstract
Microhabitats influence the distribution and abundance of benthic harmful dinoflagellate (BHAB) species. Currently, much of the information on the relationships between BHABs and microhabitat preferences is based on non-quantitative anecdotal observations, many of which are contradictory. The goal of this study was to better quantify BHAB and microhabitat relationships using a statistically rigorous approach. Between April 2016 to May 2017, a total of 243 artificial substrate samplers were deployed at five locations in the Perhentian Islands, Malaysia while simultaneous photo-quadrat surveys were performed to characterize the benthic substrates present at each sampling site. The screen samplers were retrieved 24 h later and the abundances of five BHAB genera, Gambierdiscus, Ostreopsis, Coolia, Amphidinium, and Prorocentrum were determined. Substrate data were then analyzed using a Bray–Curtis dissimilarity matrix to statistically identify distinct microhabitat types. Although BHABs were associated with a variety of biotic and abiotic substrates, the results of this study demonstrated differing degrees of microhabitat preference. Analysis of the survey results using canonical correspondence analysis explained 70.5% (horizontal first axis) and 21.6% (vertical second axis) of the constrained variation in the distribution of various genera among microhabitat types. Prorocentrum and Coolia appear to have the greatest range being broadly distributed among a wide variety of microhabitats. Amphidinium was always found in low abundances and was widely distributed among microhabitats dominated by hard coral, turf algae, sand and silt, and fleshy algae and reached the highest abundances there. Gambierdiscus and Ostreopsis had more restricted distributions. Gambierdiscus were found preferentially associated with turf algae, hard coral and, to a lesser extent, fleshy macroalgae microhabitats. Ostreopsis, almost always more abundant than Gambierdiscus, preferred the same microhabitats as Gambierdiscus and were found in microbial mats as well. With similar habitat preferences Ostreopsis may serve as an indicator organism for the presence of Gambierdiscus. This study provides insight into how BHAB-specific microhabitat preferences can affect toxicity risks.
Highlights
This study focused on expanding our understanding of the role microhabitat types play in controlling the distribution and abundance of benthic harmful algal bloom species (BHABs) in the genera Amphidinium, Coolia, Gambierdiscus, Ostreopsis, and Prorocentrum
The results of this study revealed that substrate variability in the microhabitats across depth-gradients determined the composition and differentially foster the abundance of BHAB species
This study and Yong et al.[63] represent pioneering efforts to numerically evaluate the influence of benthic microhabitat heterogeneity on the abundance and distributions of BHABs
Summary
BHABs inhabit a wide range of marine habitats and have close associations with biotic and abiotic bottom substrates including algal turf, macrophytes, seagrasses, corals, denuded coral rubble, rocks and sediment[2, 49,50,51,52,53] These substrates, in combination with abiotic factors such as temperature, salinity and light form microhabitats that influence the relative distribution and abundance of BHABs. The degree to which certain species are favoured will determine the types and amounts of toxins entering the marine food chain. In a proof of concept study, Yong et al.[63] quantified the importance of microhabitats in influencing BHAB composition and abundances They used a standardized sampling m ethod[70,71,72] combined with digital underwater imagery to quantify various bottom substrates[73]. The roles of temperature and depth in structuring microhabitats and associated BHAB composition and abundances were examined as well
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