Decadal changes in common reef coral populations and their associations with algal symbionts (Symbiodinium spp.)

Abstract

Decadal populations changes in four coral taxa and their patterns of association with algal symbionts (Symbiodinium spp. – 10 years of sampling) were examined on Kenyan back reefs over a period of climatic disturbances (1991−2009). Some of the better surviving taxa, Pavona and Pocillopora, were associated with variable temperature regimes and >50% of sampled colonies in these taxa had some of the more thermally tolerant Symbiodinium in clade D. In contrast, only around 35% of Acropora and no branching forms of Porites contained detectable levels of clade D, and both taxa experienced high levels of thermally‐induced mortality and poor recovery. Overall, however the relationship between Symbiodinium clade and population‐level success of coral hosts was not strong, and differential success inside and outside fisheries closures suggests that other factors, such as predation on corals, were also influential. Consequently, while Symbiodinium in clade D may contribute to the success of coral hosts across thermal disturbances, multiple ecological factors and additional biological traits also influence their long‐term survival.

Changes in coral sensitivity to thermal anomalies

“…Symbiont change may be even more dynamic than found in Kenya because the coral holobiont is composed of many difficult to detect taxa, including genetically variable and promiscuous symbiont algae (Mieog et al 2007, Silverstein et al 2011, Ladner et al 2012, Cunning et al 2015a. Symbiont type did not, however, clearly result in higher survival and recovery rates of common Kenyan corals over a 20 yr study period (McClanahan et al 2015a). Therefore, other factors associated with the host or the holobiont are likely to be important for survival (Smith-Keune & van Oppen 2006, Ulstrup et al 2006, Cunning et al 2016.…”

“…For example, many current predictions rely on static coral life history characteristics and their ability to act as indicators of disturbance histories (Darling et al 2012, McClanahan et al 2015a. Yet, to further complicate predictions, many corals' responses are contextual and result from recent acute and chronic interactions with their environment.…”

Partitioning scleractinian coral diversity across reef sites and regions in the Western Indian Ocean

“…We identified 11 WIO subregions based on existing coral biogeography information and recent analyses of changes in coral cover and community structure and their relations with regional temperature properties (McClanahan et al. , , b , Obura , b ). A number of studies have found subregional differences in temperature histories that appear to influence coral bleaching and mortality across thermal disturbances and expected to influence regional stress and subsequent coral community responses (McClanahan et al.…”

“…Recent analyses, for example, found significant difference in the coral community structure between mainland and island coasts (McClanahan et al. , b ) and we therefore included mainland–island geography as another scale in the spatial hierarchy. Site were chosen as typical coral reef locations that ranged in depth from 0.5 to 20 m and dominated by a calcium carbonate substratum colonized by hard and soft corals and benthic algae.…”

“…, McClanahan et al. , b ). Recent studies of local diversity patterns have uncovered a biodiversity center in the Mozambique Channel, but many of these reefs face losses of biodiversity, functions, and eventually goods and services to coastal communities due to thermal disturbances and heavy fishing (McClanahan et al.…”