- Award ID(s):
- 1756381
- NSF-PAR ID:
- 10317124
- Date Published:
- Journal Name:
- Frontiers in Marine Science
- Volume:
- 8
- ISSN:
- 2296-7745
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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null (Ed.)Successful recruitment is critical to the maintenance and resilience of populations and may be at the core of the transition from scleractinian to octocoral dominated faunas on some Caribbean reefs. For sessile invertebrates, recruitment incorporates the composite effects of larval supply, settlement and survival. The relative success of these processes differs between species and successful recruitment may be achieved through different life history strategies. Recruitment of six abundant and widespread Antillogorgia spp. was assessed at six sites on Little Bahama Bank from 2009–2012. Identification of recruits to species level, based on microsatellite analyses, revealed differences in recruitment and survival between species, sites and ears. The broadcast spawning species, A. americana and A. acerosa had low rates of early recruitment and postsettlement survival. Higher levels of recruitment success were achieved among brooding and surface brooding species following somewhat different patterns of early recruitment and survival. The internal brooder Antillogorgia hystrix had the highest recruitment at five of the sites but low survival dramatically reduced its abundance and after a year it had similar densities as the surface brooding species, A. elisabethae and A. bipinnata. The brooders have smaller colonies and will produce fewer larvae than the broadcast spawning species, but they release competent larvae which probably accounts for their higher recruitment rates. The Antillogorgia illustrate the diversity of successful reproductive strategies exhibited by octocorals, and differences in the life history strategies among these congeners are best characterized by their mode of larval development.more » « less
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Growing up is hard to do: a demographic model of survival and growth of Caribbean octocoral recruitsBackground Among species with size structured demography, population structure is determined by size specific survival and growth rates. This interplay is particularly important among recently settled colonial invertebrates for which survival is low and growth is the only way of escaping the high mortality that small colonies are subject to. Gorgonian corals settling on reefs can grow into colonies of millions of polyps and can be meters tall. However, all colonies start their benthic lives as single polyps, which are subject to high mortality rates. Annual survival among these species increases with size, reflecting the ability of colonies to increasingly survive partial mortality as they grow larger. Methods Data on survival and growth of gorgonian recruits in the genera Eunicea and Pseudoplexaura at two sites on the southern coast of St John, US Virgin Islands were used to generate a stage structured model that characterizes growth of recruits from 0.3 cm until they reach 5 cm height. The model used the frequency distributions of colony growth rates to incorporate variability into the model. Results High probabilities of zero and negative growth increase the time necessary to reach 5 cm and extends the demographic bottleneck caused by high mortality to multiple years. Only 5% of the recruits in the model survived and reached 5 cm height and, on average, recruits required 3 y to reach 5 cm height. Field measurements of recruitment rates often use colony height to differentiate recruits from older colonies, but height cannot unambiguously identify recruits due to the highly variable nature of colony growth. Our model shows how recruitment rates based on height average recruitment and survival across more than a single year, but size-based definitions of recruitment if consistently used can characterize the role of supply and early survival in the population dynamics of species.more » « less
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Abstract As the major form of coral reef regime shift, stony coral to macroalgal transitions have received considerable attention. In the Caribbean, however, regime shifts in which scleractinian corals are replaced by octocoral assemblages hold potential for maintaining reef associated communities. Accordingly, forecasting the resilience of octocoral assemblages to future disturbance regimes is necessary to understand these assemblages' capacity to maintain reef biodiversity. We parameterised integral projection models quantifying the survival, growth, and recruitment of the octocorals,
Antillogorgia americana ,Gorgonia ventalina , andEunicea flexuosa, in St John, US Virgin Islands, before, during, and after severe hurricane disturbance. Using these models, we forecast the density of populations of each species under varying future hurricane regimes. We demonstrate that although hurricanes reduce population growth,A. americana ,G. ventalina , andE. flexuosa each display a capacity for quick recovery following storm disturbance. Despite this recovery potential, we illustrate how the population dynamics of each species correspond with a longer-term decline in their population densities. Despite their resilience to periodic physical disturbance events, ongoing global change jeopardises the future viability of octocoral assemblages. -
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