11th ICRS Abstract book - Nova Southeastern University

Oral Mini-Symposium 16: Ecosystem Assessment and Monitoring of Coral Reefs - New Technologies and Approaches
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Variations in The Symbiotic Algae (Zooxanthellae) Associated With Dominant
Scleractinian Corals in Hong Kong Sar, China
Yu Man TSANG * 1 , Put ANG 2
1 Marine Science Laboratory, Department of Biology, The Chinese University of Hong
Kong, Hong Kong, Hong Kong, 2 Marine Science Laboratory, Department of Biology,
The Chinese University of Hong Kong, Shatin, Hong Kong
Hong Kong is a marginal environment for coral growth. This study aims at investigating
the potential linkages between variation in environmental parameters (mainly seawater
temperature) and variation in symbiotic algal density, chlorophyll content (chlorophyll a
and c2) and the photosynthetic capacity of two dominant Hong Kong corals Porites lutea
and Platygyra acuta. The phylogenetic information on Symbiodinium associated with
Platygyra acuta was also examined based on restriction fragment length polymorphism
(RFLP).
Seasonal photophysiological parameters of algal symbionts in P. acuta and P. lutea were
monitored from October 2006 to April 2007 at A Ye Wan and A Ma Wan in Tung Ping
Chau Marine Park. Investigation on their zooxanthellae density and pigment contents
throughout the 18 months sampling period revealed no significant bleaching occurring in
these corals. However, significant temporal variations in the zooxanthellae density (from
2 × 10 6 to 10 × 10 6 cells cm -2 of coral surface area) for both species were recorded.
Concentrations of chlorophyll a per zooxanthella were significantly higher in winter than
in summer for both species (ANOVA and Kruskal Wallis Test, p < 0.05).
Molecular phylotyping showed Symbiodinium clade C to be the dominant zooxanthellae
associated with P. acuta irrespective of their location (i.e., top or shaded region) in the
coral host. Symbiodinium clade C formed a stable association with this coral host over the
sampling period. This result supported the finding that Symbiodinium clade C is the major
clade of zooxanthellae associated with scleractinian corals in the Pacific.
16-51
Large Scale Coral Mortality in Barbados: A Delayed Response to the 2005
Bleaching Episode
Hazel OXENFORD* 1 , Angelique BRATHWAITE 2 , Ramon ROACH 2
1 Centre for Resource Management and Environmental Studies, University of the West
Indies, Cave Hill, Barbados, 2 Coastal Zone Management Unit, Ministry of Energy and
the Environment, Bridgetown, Barbados
In common with many Caribbean countries, coral reefs in Barbados suffered significant
bleaching during the high temperature event of late summer 2005. Six reef sites,
including shallow (< 10 m) and deep (> 15 m) communities were monitored over the
following year (October 2005 – November 2006) to determine mortality impacts and rate
of recovery from the bleaching event. Quantitative benthic surveys along five 1 x 20 m
band transects and five 20 m line transects at each site, were undertaken every four
months. Bleached condition (measured as % of colonies fully or partially bleached)
gradually dropped from a mean of 71% in October 2005, 38% in February to 17% in
June, before rising again to 25% in November 2006 after summer warming. Coral
mortality (measured using two independent indices: estimated % of coral colony surface
recently dead; and % of benthic coral cover recently dead) remained surprisingly low for
most species five months after the onset of bleaching (means: 3.8% colony surface dead;
or 4.8% dead cover), but rose sharply after 10 months (means: 18.7% colony surface; or
25.9% cover), eventually declining after 15 months to a near ambient levels (means:
2.0% colony surface; or 6.1% cover). In common with other eastern Caribbean islands,
recovery from bleached condition was slow, persisting for many months after water
temperatures had cooled, and overall mortality impact was high on both deep and shallow
reefs. In contrast were the delayed onset of significant mortality and the low incidence of
coral disease following the bleaching event on Barbados reefs. High losses in live coral
cover have significant economic implications for the island which derives a major
proportion of its GDP from tourism, and relies heavily on healthy reefs for coastal
protection. This emphasises the extreme vulnerability of small Caribbean islands to the
global warming trend.
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