Reproductive effort of an endemic major reef builder along an inshore–offshore gradient in south-western Atlantic

Abstract

Mussismilia braziliensisis endemic to the south-western Atlantic, where it plays an important role as a major reef builder. It occurs in a wide range of sediment conditions between coastal and offshore environments. Here, we investigated its reproductive effort along an inshore–offshore gradient. Three sites were sampled with varying distances (15 to 60 km) from the mainland in the Abrolhos Reef Complex (18° S). Reproductive effort was estimated as fecundity (number of eggs per: polyp, cm2, mm3, and mesenteries). Mean fecundity per polyp was 338.7 (±73.5 SD) and the highest number of eggs per polyp was 987. Percentages of fertile mesenteries per polyp were similar among sites. However, the fecundity per mesentery varied among colonies and among sites. Fecundity per polyp increased as its area, volume, height and number of fertile mesenteries increases. The area closest to the coast (‘Pedra de Leste’) presented the highest mean fecundity per polyp (410 eggs ± 159.2 SD), cm2(233.47 eggs ± 219.44 SD), mm3(4.95 eggs ± 2.34 SD) and mesentery (10.6 eggs ± 4.3 SD). Corals closest to the coast had 55% higher fecundity per polyp and 64% higher fecundity per cm2than corals offshore. This area presented the highest contribution of non-carbonate sediments deposited on the reefs. Therefore, we suggest that colonies ofM. braziliensismay present higher uptake rates of particulate matter at inshore reefs, which allow for higher rates of tissue growth (less nutrient limitation) and energy allocation to reproduction.