High taxonomic resolution surveys and trait-based analyses reveal multiple benthic regimes in North Sulawesi (Indonesia)

Abstract

As coral reef communities change and reorganise in response to increasing disturbances, there is a growing need for understanding species regimes and their contribution to ecosystem processes. Using a case study on coral reefs at the epicentre of tropical marine biodiversity (North Sulawesi, Indonesia), we explored how application of different biodiversity approaches (i.e., use of major taxonomic categories, high taxonomic resolution categories and trait-based approaches) affects the detection of distinct fish and benthic communities. Our results show that using major categories fails to identify distinct coral reef regimes. We also show that monitoring of only scleractinian coral communities is insufficient to detect different benthic regimes, especially communities dominated by non-coral organisms, and that all types of benthic organisms need to be considered. We have implemented the use of a trait-based approach to study the functional diversity of whole coral reef benthic assemblages, which allowed us to detect five different community regimes, only one of which was dominated by scleractinian corals. Furthermore, by the parallel study of benthic and fish communities we provide new insights into key processes and functions that might dominate or be compromised in the different community regimes.

Coral reef benthic community changes in the Anthropocene: Biogeographic heterogeneity, overlooked configurations, and methodology

“…The current 'flattening' of reefs will have, at present largely unknown, ecological consequences as cryptic communities, with largely understudied ecological functions, may disappear accordingly. Studies assessing coral reef trajectories and recovery after disturbances should incorporate a functional assessment of the communities as recent studies have shown that cover estimates or alpha diversity measures can mask important changes (McWilliam et al, 2020;Reverter et al, 2021;Richardson et al, 2018). Furthermore, novel threats, such as the increase of pathogens linked to climate change or anthropogenic substances (e.g.…”

“…In fact, recent research suggests that coral reefs dominated by invertebrates other than hard corals, such as sponges and soft corals, might be becoming more frequent as a result of global change (Bell et al, 2018;Chaves-Fonnegra et al, 2018;Inoue et al, 2013;Lesser & Slattery, 2020). Yet, information regarding changes to such alternative communities remain highly scattered and the drivers and mechanisms behind the proliferation of these alternative organisms remain largely unknown (Norström et al, 2009;Reverter et al, 2021). For example, whereas some changes have been observed after specific pulse disturbances, such as bleaching events (Chaves-Fonnegra et al, 2018) or ocean acidification (Inoue et al, 2013), their frequency, distribution and implications for ecosystem functioning remain unexplored.…”