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Description:
Project Manager:
Ian Enochs
Project Years:
2016
2017
Project Summary:
Coral reefs along the Florida Keys portion of the Florida Reef Tract (FRT) have undergone a dramatic decline since the 1980s. Since the 1997-98 El Niño event, coral cover on offshore reefs of the FRT has been = 5% and continued to decline. Mortality of the Orbicella annularis species complex has driven this recent loss. One exception to this decline occurred on the inshore patch reefs of the Florida Keys, where coral cover has remained relatively high. Average coral cover on the patch reefs typically ranges from 15-35%, with some reefs having values > 40%. For instance, Cheeca Rocks (NCRMP class III sentinel climate/OA site) is an example of an inshore patch reef that has abundant Oribicella faveolata with many colonies presumed to be 100+ years of age (meters in diameter/height). In surveys from 2012-2015, mean coral cover across six sites was 28.4-31.6%. Cover of O. faveolata was 20.2-23.3%, or > 70% of the total coral cover --- this species accounts for > 75% of the total CaCO3 production of this reef (Manzello unpub. data). This population is also resilient as cover of O. faveolata declined only 1.3% as a result of the 2014 Keys-wide mass bleaching event, which was the warmest summer on record for the Florida Keys (Manzello in review). CRCP-funded work has shown that growth and calcification rates of both O. faveolata and Porites astreoides recovered quickly from cold and recurrent warm-water stress over the past decade (Manzello et al. 2015a,b). These higher calcification rates and their quick recovery after thermal stress are likely important factors in the persistence of high coral cover inshore.This high coral cover is enigmatic because inshore sites experience greater thermal variability, increased turbidity/depressed light, increased sedimentation, and elevated nutrients. Five hypotheses have been proposed to explain the persistence of high coral cover on the inshore patch reefs of the Florida Keys. It has been suggested that (1) the high temperature variance at the inshore patch reefs may have led to thermal acclimatization and/or adaptation, resulting in an increased resistance to thermal stress. Others have proposed that (2) the elevated turbidity inshore may lead to higher heterotrophic feeding, or (3) reduce photo-oxidative damage during warm-water stress via shading. Also, (4) heat-tolerant zooxanthellae clades may be a factor in these trends. Recently, via other CRCP-funded work, (5) it was discovered that aragonite saturation state is elevated inshore, adding another possible contributing factor (Manzello et al. 2012). Research is needed to determine which of the aforementioned factors are driving the persistence of the high coral cover at the inshore sites. This project will rigorously address these five hypotheses by opportunistically taking advantage of the current bleaching; yielding vital insights for managers as climate change and ocean acidification accelerate.References Manzello DP, et al (2012) PLoS ONE 7:e41715.Manzello DP, et al (2015a) Mar Ecol Prog Ser 521:81-89Manzello DP, et al (2015b) J Exp Mar Biol Ecol 471:198-207
Expected Outcome:
There are at least five potential factors leading to the high resilience of the inshore patch reefs in the Florida Keys. This project will determine which of those five factors are most crucial. This is vital information as it will lead to increased certainty for why these reef areas are resilient and this ‘recipe for resilient reefs' can then be used to prioritize other similar locations in Florida, across the wider Caribbean, and potentially worldwide. This will be the first time all of these hypotheses will be tackled in tandem during an actual bleaching event, which will directly show which of these factors are key to resilience from thermal stress for the Florida Keys inshore patch reefs.For example, if we find that corals nearshore exhibit thermal acclimatization of the host, whereas the remaining four hypotheses yield inconclusive data (i.e.,inshore no different than offshore), then we know that the most important element to resilient reefs in Florida is routine exposure to high and variable temperatures and the other factors are subsidiary. Any one of these individual factors, or a combination thereof, which quantitatively corresponds to a quicker recovery and/or increased survivorship inshore will provide evidence that they are crucial to management and preservation of resilient reefs in the future. Many projects aim to achieve this end, but this project is unique in that it has pared down the key factors associated with already resilient reefs that will be rigorously tested. Therefore, this project will yield concrete evidence rather than more arm-waving.
Project Locations:
Project Category:
Climate Change
Project Type:
Closed
Project Status:
Completed
Associated Products:
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