Patterns in sexual reproduction of the dominant scleractinian corals at Rapa Nui (Easter Island): Pocillopora verrucosa and Porites lobata

Abstract

Sexual reproduction is fundamental to the maintenance and recovery of coraldominated communities in high-latitude and isolated locations, where replenishment often depends on local reproductive activity rather than recruitment from distant reefs. Rapa Nui (Easter Island) is one of the most remote islands in the Pacific, lying at the southern, subtropical edge of the range of reef-building scleractinians. Here, we describe the sexual reproduction and timing of the 2 dominant corals, Pocillopora verrucosa and Porites lobata. Reproductive activity was inferred from the identification and staging of gametes via histological analyses of monthly samples collected from December 2012 to May 2014 at 12 m depth at Motu Tautara (27°6.6' S, 109°25.5' W) with in situ temperature records. In P. verrucosa, the observed hermaphroditic activity spanned from December to January, resulting in mature oocytes of 117 µm mean diameter. In P. lobata, observed gonochoric activity spanned from December to March, resulting in mature oocytes of 180 µm mean diameter. The observed initiation of gametogenic cycles coincided with the onset of spring warming in both species. Inferred spawning of P. verrucosa followed a relatively calm period of daily variance reduction in local in situ temperature and wind speed prior to the peak in thermal conditions, whereas inferred spawning of P. lobata coincided with peak temperatures in one year but not the other. We suggest temporal restrictions of disruptive coastal activities such as dredging during coral spawning periods and mitigation of land-based sources of pollution and watershed discharge that may reduce water quality.

Coral reproduction at Hall Bank, a high latitude coral assemblage in Western Australia

“…Numbers are the number of sampled colonies in each reproductive condition on each occasion. Sex: sexuality; N: no gametes; M: mature; I: immature; Month of spawn: months in which mature gametes were observed; H: hermaphrodite; G: gonochore; na: could not be determined in the eastern Pacific, where 2 species of broadcast spawning corals were observed to spawn at times of low wind speeds and prior to the summer maximum seawater temperatures (Buck-Wiese et al 2018). One explanation for the difference in latitudinal patterns of spawning on the east and west coast might be the contrasting changes in water temperature and solar radiation between spring and autumn.…”

Same places, same stories? Genomics reveals similar structuring and demographic patterns for four Pocillopora coral species in the southwestern Indian Ocean

“…All four species are sexual broadcast spawners (Schmidt‐Roach, Miller, et al., 2012), with different timings depending on locality (e.g. Bouwmeester et al., 2021; Buck‐Wiese et al., 2018; Kruger & Schleyer, 1998), but only P. acuta has been reported as an asexual brooder with no doubt (Oury et al., 2019). This latter species seems also more proponent of fragmentation due to its finer branches, and is mostly found in shallow (<5 m depth) and relatively enclosed habitats compared to other species (Veron, 2000).…”