Interannual changes (2017–2022) in parrotfish abundance and biomass and their influence on bioerosion and macroalgae consumption rates in a Mexican Caribbean reef

In this study, we evaluated temporal variation in parrotfish biomass and abundance and their association with environmental variables in a Caribbean reef system on the southern Yucatan Peninsula (Mexico). Using visual surveys conducted at the reef front during the rainy season from 2017 to 2022, we analyzed interannual variations in abundance, species richness, and biomass, and their impacts on total bioerosion rates (TBR) and total macroalgal consumption (TMCR). Additionally, benthic substrate cover was quantified using video transects. Seven parrotfish species were recorded, with a drastic decline of ~ 45% in parrotfish abundance (from 40.33 ind. 100 m 2 in August 2017 to 18.33 ind. 100 m⁻ 2 in August 2022) and an 84% loss of total biomass (from 4,265.9 to 681.5 g 100 m⁻ 2 ). The biomass reduction was linked to changes in size-frequency distribution, with smaller size classes (1–10 cm TL) dominating the last sampling. This shift resulted in a 20-fold reduction in TMCR and a fivefold decrease in TBR. Both functional rates declined significantly between 2017 and 2022 (PERMANOVA, p < 0.05), driven mainly by a reduction in the average abundance of Sparisoma viride (SIMPER). A 12% increase in the average macroalgal cover was also documented (≈39% in 2017 to ≈51% in 2022), along with a 5% decrease in coral cover from 11 to 6%. Redundancy analysis (RDA) indicated that increased CO₂, seawater temperatures, and macroalgal cover were negatively correlated with parrotfish abundance, macroalgal consumption, and bioerosion rates of key species such as Scarus iseri , Sparisoma rubripinne , and Sparisoma viride .