Effect of fine-scale habitat differences on algal colonisation in a coral-dominated subtropical reef.

Leonardo L De Carvalho,Roberto C Villaça

doi:10.1590/0001-3765202120191191

Abstract

Maintaining the coexistence of algae and corals depends on the interactions between them. We investigated these interactions to assess: (1) recruitment patterns of algal turfs over time in dead areas on live corals; (2) the influence of fine-scale differences in coral-dominated environments on algal colonisation; (3) the influence of coral as a substrate for algal recruitment; (4) the invasion potential of algal turf on live coral tissue. This study compared algal colonisation directly on dead or damaged coral areas with algal colonisation on recruitment plates in coral-dominated or -free areas at 23, 154, and 230 days. We also monitored coral colonies over 1.5 years. Filamentous and articulated coralline algae were primarily evident in the early colonisation, reaching stability after 154 days. On a fine scale, the coral-dominated environment showed an increase in number of algal species and coverage. However, coral substrate was selective, with fewer species recruited to this substrate compared to the artificial plates. Furthermore, the competitive dynamics between corals and algal turfs did not result in a winner over time. Thus, algal turf colonisation was influenced not only by coral substrate but also by the reef environment on a fine scale.

Highlights

Algal turfs are considered competitors against corals for space (Wild et al 2004)
In an important review about algal turf sediments on coral reefs, Tebbett & Bellwood (2019) defined algal turfs to be shorter than 2 cm and generally composed of filamentous macroscopic algae associated with sediment
We recognized that other groups, such as diatoms and cyanobacteria, are part of the algal turf community (Diaz-Pulido & McCook 2002, Connell et al 2014, Tebbett & Bellwood 2019), our work focuses on assessing the interaction between algae in turfs and corals

Summary

Introduction

Algal turfs are considered competitors against corals for space (Wild et al 2004). definitions of algal turfs or epilithic algal matrix (EAM) are highly varied (Connell et al 2014). Connell et al (2014) concluded that the term turfs represents several types of microand macro-algae which share an extensive lowlying morphology and are densely aggregated. We considered turfs to be consortia of green, red, and brown algae, which are less than 10 cm in height (Odum & Odum 1955, Morrissey 1980, Connell et al 2014) These turfs form dense mats often associated with sediments

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Discussion

Conclusion