Effects of Climate and Seawater Temperature Variation on Coral Bleaching and Mortality

Abstract

Abstract. Coral bleaching due to thermal and environmental stress threatens coral reefs and possibly people who rely on their resources. Here we explore patterns of coral bleaching and mortality in East Africa in 1998 and 2005 in a region where the equatorial current and the island effect of Madagascar interact to create different thermal and physicochemical environments. A variety of temperature statistics were calculated, and their relationships with the degree-heating months (DHM), a good predictor of coral bleaching, determined. Changes in coral cover were analyzed from 29 sites that span .1000 km of coastline from Kenya to the Comoros Islands. Temperature patterns are influenced by the island effect, and there are three main temperature environments based on the rise in temperature over 52 years, measures of temperature variation, and DHM. Offshore sites north of Madagascar that included the Comoros had low temperature rises, low DHM, high standard deviations (SD), and the lowest relative coral mortality. Coastal sites in Kenya had moderate temperature rises, the lowest temperature SD, high DHM, and the highest relative coral mortality. Coastal sites in the south had the highest temperature rises, moderate SD and DHM, and low relative coral mortality. Consequently, the rate of temperature rise was less important than background variation, as reflected by SD and kurtosis measures of sea surface water temperature (SST), in predicting coral survival across 1998. Coral bleaching responses to a warm-water anomaly in 2005 were also negatively related to temperature variation, but positively correlated with the speed of water flow. Separating these effects is difficult; however, both factors will be associated with current environments on the opposite sides of reefs and islands. Reefs in current shadows may represent refugia where corals acclimate and adapt to environmental variation, which better prepares them for rising temperature and anomalies, even though these sites are likely to experience the fastest rates of temperature rise. We suggest that these sites are a conservation priority and should be targeted for management and further ecological research in order to understand acclimation, adaptation, and resilience to climate change.

Performance Evaluation of CRW Reef-Scale and Broad-Scale SST-Based Coral Monitoring Products in Fringing Reef Systems of Tobago

“…2016, 8,12 3 Atlantic coastlines. Buccoo Reef extends to 3 km offshore and consists of a shallow lagoon ranging in depths from 2-6 m containing several patch reefs and reef flats, with corals also present on the reef slope to 20 m depth [26].…”

“…These events have threatened to reduce fishery population [3,4], while simultaneously affecting the economic benefits of tourism that supports many coastal communities [5,6]. Effective management of coral reefs and associated ecosystem services has been aided in recent decades by satellite remote sensing monitoring that provides near real-time sea temperature (SST) data and customized products [7][8][9][10][11][12][13]. Mass coral bleaching has been related to anomalously high sea temperatures and has resulted in increased mortality of corals globally [7,14].…”

The physiological response of reef corals to diel fluctuations in seawater temperature

“…One example of the benefits of such an approach comes from Puerto Rico, where a combination of temperature metrics -rather than simply the maximum seawater temperature, and the duration of exposure to this value (Gleeson and Strong, 1995) -provided the best predictor of coral bleaching between 1966 and 1995 (Winter et al, 1998). Similarly, off the coast of East Africa, coral bleaching was associated with degree heating weeks, degree heating months, and the variability as assessed by the standard deviation and kurtosis of the monthly mean records of sea surface temperature (SST) (McClanahan et al, 2007). Together, studies such as those of Winter et al (1998) and McClanahan et al (2007) indirectly suggest that the thermal history of a coral matters a great deal in determining its response to thermal stress.…”

“…Similarly, off the coast of East Africa, coral bleaching was associated with degree heating weeks, degree heating months, and the variability as assessed by the standard deviation and kurtosis of the monthly mean records of sea surface temperature (SST) (McClanahan et al, 2007). Together, studies such as those of Winter et al (1998) and McClanahan et al (2007) indirectly suggest that the thermal history of a coral matters a great deal in determining its response to thermal stress.…”

Establishing the Current Cover and Abundance of Coral in Malindi Marine National Park

“…Consequently, several studies have revealed that the decline of corals has resulted in shifts in dominance from hard corals to macro algae and other sessile invertebrate dominated benthic functional groups in many regions of the world [10]. made in 2002 [2,3,11,12]. Since, coral cover is important to gauge the overall health and general status of a reef in relation to shifting dominance, ecological processes and economic services provided to human communities [9,13].…”