Algae on coral rocky reefs as indicators of disturbances along the Ecuadorian coast

Abstract

We present an analysis of algal communities of two coral rocky reefs of the Ecuadorian coast. This study aims to determine which algae classify best two sites with different degrees of disturbance, considering the spatio-temporal variation of algal groups (macroalgae and turf) using a random forest approach. 14 algae species were recorded, eight belong to Rhodophyta, five to Chlorophyta and four to Phaeophyta. Overall macroalgae coverage species displayed significant differences between sites, among months and the interaction Site*Month. Based on a random forest classification algorithm, we performed a systematic study of the interactions using the algal coverage values. Our data indicated that coral rocky reefs disturbance in these sites of the Ecuadorian coast can be classified by the interactions of Dictyota dichotoma, Lobophora variegata and algal turf. Results of this study indicated that lower diversity of macroalgae were associated with higher macroalgae coverage of L. variegata and the presence of turf algae in the disturbed site. The presence of D. dichotoma and lower coverage of turf was associated with the undisturbed site. Our results evidence the interaction among algal turf and macroalgae on coral rocky reefs and exhibits them as indicators of disturbances along the coral rocky reef systems. Results from random forest analysis revealed that, with presence of Dictyota dichotoma, turf can function as a healthy alternate state at undisturbed sites.