Split spawning increases robustness of coral larval supply and inter-reef connectivity.
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ABSTRACT:
SUBMITTER: Hock K
PROVIDER: S-EPMC6671964 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Split spawning in coral populations occurs when gamete maturation and mass spawning are split over two consecutive months. While split spawning has been observed at many reefs, little is known about the frequency and significance of these events. Here we show that split spawning occurred frequently and predictably over a decade at Scott Reef. Split spawning overlays the biannual spawning pattern in the region and occurs when the full moon falls in the first week of the usual spawning month, or the last week of the previous month. Additionally, in split years most species have their main spawning event after a 13-month lunar cycle, in the month following the usual spawning month. Without split spawning, spawn dates would shift by ~10 days each year to occur outside of optimal environmental windows. Our results suggest that split spawning is driven by a disconnect between lunar and seasonal cues, and is analogous with a 'leap year' in coral reproduction, realigning spawning dates with favourable conditions for reproduction.
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Project description:Climate warming is a major cause of the global decline of coral reefs. Active reef restoration, although still in its infancy, is one of several possible ways to help restore coral cover and reef ecosystem function. The deployment of mature coral larvae onto depauperate reef substratum has been shown to significantly increase larval recruitment, providing a novel option for the delivery of ex situ bred coral stock to the reef for restoration purposes. The success of such reef restoration approaches may be improved by the use of coral larval stock augmented for climate resilience. Here we explore whether coral climate resilience can be enhanced via interspecific hybridization through hybrid vigour. Firstly, we assessed cross-fertility of four pairs of Acropora species from the Great Barrier Reef. Temporal isolation in gamete release between the Acropora species was limited, but gametic incompatibility was present with varying strength between species pairs and depending on the direction of the hybrid crosses. We subsequently examined the fitness of hybrid and purebred larvae under heat stress by comparing their survival and settlement success throughout 10 days of exposure to 28 °C, 29.5 °C and 31 °C. Fitness of the majority of Acropora hybrid larvae was similar to that of the purebred larvae of both parental species, and in some instances it was higher than that of the purebred larvae of one of the parental species. Lower hybrid fertilization success did not affect larval fitness. These findings indicate that high hybrid fitness can be achieved after overcoming partial prezygotic barriers, and that interspecific hybridization may be a tool to enhance coral recruitment and climate resilience.
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Project description:For marine fishes with a bipartite life cycle, pelagic larval dispersal can shape the distribution, connectivity, composition and resilience of adult populations. Numerous studies of larval dispersal, and associated settlement and recruitment processes, have examined the relationship between population connectivity and oceanographic features. However, relatively little is known about spatial and temporal variation in the abundance of larvae settling among different reefs and the extent to which the species assemblage of larvae settling at one location is reflective of the assemblage in neighbouring areas. Here, using crest nets, which provide a non-selective measure of the total abundance and assemblage of larvae settling to a reef (i.e. larval supply), we collected larval coral reef fishes at five locations surrounding two spatially disparate French Polynesian islands: Moorea and Nengo-Nengo. Overall, larval settlement patterns were correlated with the lunar cycle, with larval abundance peaking during the new moon. Although there were some spatial differences in larval supply among the five monitored sites, settlement patterns were largely consistent, even at the species level, irrespective of factors such as coastline orientation or distance between sites. This study provides further insights into the mechanisms driving patterns of dispersal and settlement of larval fishes over large spatial scales.
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