Effect of the herbivory of Cittarium pica (Gastropoda: Tegulidae) and seasonality on the rocky shore algal assemblage of Bonito Gordo, Tayrona National Natural Park, Colombian Caribbean

Abstract

This research was aimed at determining the role of herbivory by the Top Shell snail Cittarium pica on the rocky shore algal assemblage in the Santa Marta area, Colombia. Caging experiments were carried out in the upper mesolittoral from December 2017 to June 2018, with inclusion (C. pica), exclusion (no herbivores) and control (2 open sides, no cage) treatments. The natural algal decrease during the rainy season was reinforced in April, when for several days calm seas and noon low tides occurred together, producing high temperatures and desiccation, which generated their massive mortalities. Increased cover of encrusting coralline algae was observed in treatments with C. pica, insinuating that they are favored by grazing, on them or on other groups of algae. In general, herbivory by C. pica did not appear to control the algal assemblage. The current dominance of small individuals in the population from overexploitation could be responsible, owing to their physical limitation to graze on larger and firmer algae. The algae were stimulated mainly by coastal upwelling and controlled by environmental factors that sometimes can be extreme.