konstantin tkachenko
TRANSCRIPT
Konstantin Tkachenko Ph.D.Department of Natural and Geographic Sciences
Samara State Educational UniversitySamara, Russia
Location of study sites in Ihavandippolu atoll
CoordinatesLatitudinal extension:
7° 06’ – 6° 54’ N
Longitudinal extension:
72°47’ – 72°59’ E
SizeArea: 330 km2
Maximal dimension from W to E
is similar to that from N to S
and equal to 21 km
N
Material and methods
SamplingDepth: 3-7 m
Phototransect method
4×40 m photransects
20 photoquadrats per transect
Each photoquadrat = 0.4 sq. m
EstimationCPCe software
50 points per photoquadrat
Percent cover of:
1. Hard coral
2. Dead hard coral
3. Soft coral
4. Coralline algae
5. Macroalgae
6. Rock, rubble, sand
Census of herbivorous fish
Three major families of
herbivorous fish were counted:
Acanthuridae
Scaridae
Siganidae
4×10 min timed swim visual
estimations
Acanthuridae Scaridae
Siganidae
Distribution of major benthic and substrate categories on
study sites
Macroalgae cover < 0.5 % in all sites
Distribution of 12 dominant genera on study sites
Site 1
20.6
12.8
Distribution of specific coral groups with different susceptibilityto bleaching (% cover)
Susceptible Tolerant ResistantTypical reef on site 1
Site 2
Distribution of specific coral groups with different susceptibilityto bleaching (% cover)
Susceptible Tolerant Resistant
1 1.9
19.5
Typical reef on site 2
Site 3
5.7
0.2
22.3
Distribution of specific coral groups with different susceptibilityto bleaching (% cover)
Susceptible Tolerant Resistant
Typical reef on site 3
Site 4
18.5
1.2
20.5
Distribution of specific coral groups with different susceptibilityto bleaching (% cover)
Susceptible Tolerant Resistant
Typical reef on site 4
Site 5
11
2.1
8.9
Distribution of specific coral groups with different susceptibilityto bleaching (% cover)
Susceptible Tolerant Resistant
Typical reef on site 5
Site 6
14.6
2.1
16.5
Distribution of specific coral groups with different susceptibilityto bleaching (% cover)
Susceptible Tolerant Resistant
Typical reef on site 6
Site 7
28.3
0.8
10.3
Distribution of specific coral groups with different susceptibilityto bleaching (% cover)
Susceptible Tolerant Resistant
Typical reef on site 7
Site 8
15.3
4.76.8
Distribution of specific coral groups with different susceptibilityto bleaching (% cover)
Susceptible Tolerant Resistant
Typical reef on site 8
Site 9
38.1
0.1
13
Distribution of specific coral groups with different susceptibilityto bleaching (% cover)
Susceptible Tolerant Resistant
Typical reef on site 9
Site 10
18.5
0.1
2.8
Distribution of specific coral groups with different susceptibilityto bleaching (% cover)
Susceptible Tolerant Resistant
Typical reef on site 10
Site 11
Herbivorous fish
Abundant herbivore fish especially acanthurids prevent local coral reefs from phase shiftto algae-dominated communities
Effect of SW and NE monsoons and related hydrodynamic patterns on Ihavandippolu atoll
N
Status of coral communities in Ihavandippolu atoll
Stable coral community withhigh coral cover and dominance of susceptiblegenera
Plot is based on quantitative estimation of study sites and visual inspection of several reefs
Balanced coral community in terms of proportional abundance of susceptible and resistant + tolerant genera
Climax coral community with dominance of resistant genera and low total coral cover
Unstable coral community with low total coral cover and dominance of susceptible genera
Collapsed coral community with single occurrence of live corals
Conclusions
1. Inner reefs protected from the ocean swell and opened to the influence of internal waves generated by SW monsoon revealed the most healthy coral communities with relatively highest coral cover and proportion of susceptible genera
2. Reefs located in the center of atoll’s lagoon exhibited climax coral communities with low coral cover and diversity and dominance of resistant genera. Susceptible genera remain degraded after the first mass coral bleaching event in 1998.
3. Northern and eastern outer reefs most subjected to the influence of NE monsoon demonstrated unstable coral communities with low coral cover and high proportion of dead corals or totally degraded reef ecosystems
4. High abundance of herbivorous fish prevent microalgae blooms on local coral reefs
5. Increase of frequency of thermal anomalies may cause further decline of coral cover in Ihavandippolu atoll and strategic shift at most reefs to the dominance of coral genera that are more resistant to changing environment
Thank you for attention