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

Miriam Reverter,Robert Bara,Markus T Lasut,Sven Rohde,Peter J Schupp,Matthew Jackson,Marco Segre Reinach,Mareen Moeller

doi:10.1038/s41598-021-95905-8

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.

Highlights

Ecosystems worldwide are experiencing profound ecological changes including biodiversity losses[1] and community rearrangements[2], which are expected to worsen with climate change, even under moderate C O2 mitigation s cenarios[3]
We studied the benthic and fish community composition of nine coral reefs in North Sulawesi (Indonesia, Supplementary Table 1) by using major categories, categories at the highest taxonomic resolution possible and functional entities (FEs, defined using trait-base approaches) (Supplementary Tables 2, 3)
Regardless of the type of community studied the use of major categories failed to identify most of the community differences highlighted by the use of higher resolution data (Fig. 2)

Summary

Introduction

Ecosystems worldwide are experiencing profound ecological changes including biodiversity losses[1] and community rearrangements (i.e., non-random species turnover)[2], which are expected to worsen with climate change, even under moderate C O2 mitigation s cenarios[3]. Shifts in species compositions including decreases in scleractinians and increases in non-reef building species such as algae, sponges and octocorals are becoming more frequent as a result of continuous anthropogenic and climate stressors[12,13,14] Such compositional changes affect several core ecosystem processes (i.e., carbonate production, primary production, trophic interactions and reef replenishment) and pose new conservation challenges[5,15,16]. And functionally distinct ecosystems will likely respond differently to disturbances, which can result in different species configurations, further hindering the study and prediction of coral reef trajectories and their effect on core ecosystem p rocesses[17,19] In this context, conservation approaches need to consider both. Whilst scleractinian corals are the key organisms of coral reefs, recent shifts towards assemblages dominated by alternate organisms highlight the need of expanding these approaches to include all types of benthic organisms

Methods

Results

Conclusion