# Assessment of the fecundity of deep-sea corals in southeastern Brazil

## TL;DR

This study examines the reproductive capacity of deep-sea corals in Brazil to better understand their resilience and inform conservation efforts.

## Contribution

The study provides new fecundity data for key deep-sea coral species in Brazilian sedimentary basins, highlighting regional and temporal variations.

## Key findings

- S. variabilis had the highest average fecundity (53.6 ± 10.7 oocytes/mm3) among species with continuous gametogenic cycles.
- E. rostrata had the lowest fecundity (3.1 ± 0.7 oocytes/mm3) and the largest oocytes (900 μm).
- The Espírito Santo Basin showed the highest average fecundity and number of female samples.

## Abstract

Deep-sea corals have been facing several anthropogenic threats worldwide, making it increasingly important that studies better understand their reproductive biology and associated cycles. This study described the fecundity of the main habitat-building scleractinian species in three sedimentary basins of southeastern Brazil in two pre-determined periods over 2 years. These basins are responsible for the most significant oil and gas production on the Brazilian coast. The relation between the number of gametes and the size of the individuals’ polyps determines their fecundity. Madrepora oculata, Solenosmilia variabilis, Desmophyllum pertusum (formerly Lophelia pertusa), and Enallopsammia rostrata samples were obtained in 2016 and 2017 and histologically prepared to estimate the reproductive effort of these species. Each oocyte development stage was classified and counted to evaluate the reproduction strategies of each species. A single D. pertusum polyp (collected in May 2017) showed over 241 thousand oocytes and a 167.9 oocytes/mm3 fecundity, typical of periodic reproduction. S. variabilis had the highest average fecundity (53.6 ± 10.7 oocytes/mm3) of the species with a continuous gametogenic cycle. M. oculata showed 23.5 ± 7.03 oocytes/mm3, whereas E. rostrata had the lowest fecundity (3.1 ± 0.7 oocytes/mm3). Fecundity is inversely proportional to oocyte size, and E. rostrata showed the largest oocytes (900 μm), a result aligned with previous studies. Considering the entire sample, the Espírito Santo Basin was the most productive due to its highest average fecundity (followed by the Santos and the Campos Basins) and greatest number of female samples. Notably, 2017 showed the highest average fecundity. The reproductive strategies of organisms play an important role in the ability of species to respond to selective pressures since gamete production (especially oocytes) is energetically expensive and strongly sensitive to environmental conditions. Thus, this study contributes to refining the available data about the life history and resilience strategies of deep-water corals, providing scientific information to manage and conserve these deep-sea ecosystems.