The Importance of Coral Larval Recruitment for the Recovery of Reefs Impacted by Cyclone Yasi in the Central Great Barrier Reef

Abstract

Cyclone Yasi, one of the most severe tropical storms on record, crossed the central Great Barrier Reef (GBR) in February 2011, bringing wind speeds of up to 285 km hr−1 and wave heights of at least 10 m, and causing massive destruction to exposed reefs in the Palm Island Group. Following the cyclone, mean (± S.E.) hard coral cover ranged from just 2.1 (0.2) % to 5.3 (0.4) % on exposed reefs and no reproductively mature colonies of any species of Acropora remained. Although no fragments of Acropora were found at impacted exposed sites following the cyclone, small juvenile colonies of Acropora (<10 cm diameter) were present, suggesting that their small size and compact morphologies enabled them to survive the cyclone. By contrast, sheltered reefs appeared to be unaffected by the cyclone. Mean (± S.E.) hard coral cover ranged from 18.2 (2.4) % to 30.0 (1.0) % and a large proportion of colonies of Acropora were reproductively mature. Macroalgae accounted for 8 to 16% of benthic cover at exposed sites impacted by cyclone Yasi but were absent at sheltered sites. Mean (± S.E.) recruitment of acroporids to settlement tiles declined from 25.3 (4.8) recruits tile−1 in the pre-cyclone spawning event (2010) to 15.4 (2.2) recruits tile−1 in the first post-cyclone spawning event (2011). Yet, post-cyclone recruitment did not differ between exposed (15.2±2.1 S.E.) and sheltered sites (15.6±2.2 S.E.), despite the loss of reproductive colonies at the exposed sites, indicating larval input from external sources. Spatial variation in impacts, the survival of small colonies, and larval replenishment to impacted reefs suggest that populations of Acropora have the potential to recover from this severe disturbance, provided that the Palm Islands are not impacted by acute disturbances or suffer additional chronic stressors in the near future.

Reserves as tools for alleviating impacts of marine disease

“…To aid in distinguishing between disturbance caused by the cyclone and longer term disturbances caused by recreational activities, sites were further categorized as either windward sites that were exposed to cyclonic winds or leeward sites that were sheltered from wave damage (see [52]). There were eight leeward and six windward MNP sites and six HP sites in each leeward and windward location.…”

“…There were eight leeward and six windward MNP sites and six HP sites in each leeward and windward location. These surveys were conducted approximately 12 months after the passage of a severe category 5 cyclone in early February 2011 (see [52,53] for specific details of Cyclone Yasi and figure 1d).…”

The active spread of adaptive variation for reef resilience

“…Contrary to initial assumptions of complete connectivity in marine systems, corals vary in their dispersal ability and genetic connectivity (reviewed in Jones et al, 2009;van Oppen & Gates, 2006). Many coral species are highly differentiated with low levels of gene flow (Lukoschek, Cross, Torda, Zimmerman, & Willis, 2013;van Oppen, Bongaerts, Underwood, Peplow, & Cooper, 2011;Underwood, Smith, Oppen, & Gilmour, 2009;Warner, Oppen, & Willis, 2015), as initially described in early studies on predominantly brooding species on the GBR (Ayre & Hughes, 2004). Regional differentiation has also been detected in a number of species from the Caribbean, the Red Sea, Drury, Schopmeyer, et al, 2017;Foster et al, 2012;Howells, Abrego, Meyer, Kirk, & Burt, 2016;Rippe et al, 2017;Underwood, Richards, Berry, & Gilmour, 2017).…”

Congruent patterns of connectivity can inform management for broadcast spawning corals on the Great Barrier Reef

“…), as recruitment from external sources is essential for the recovery of reefs that have undergone high mortality (Lukoschek et al . ). However, lack of information about connectivity meant it was not used for the rezoning of the GBR (Fernandes et al .…”

“…Indeed, thermal anomalies (and their associated impacts on marine organisms) in the period 1985-2009 equally affected areas inside and outside no-take zones in the GBRMP (Ban et al 2012). Connectivity is a critical factor for improving the effectiveness of networks of no-take zones to respond to disturbances (Lagabrielle et al 2014), as recruitment from external sources is essential for the recovery of reefs that have undergone high mortality (Lukoschek et al 2013). However, lack of information about connectivity meant it was not used for the rezoning of the GBR (Fernandes et al 2005) nor in the design of most other marine no-take networks around the world Lagabrielle et al 2014;Magris et al 2014).…”