CORDIO Status Report 1999.pdf

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THE BLEACHING EVENT The 1997–98 El-Niño Southern Oscillation had severe impacts on the climate of East Africa, with unprecedented rains starting in October 1997 and continuing to July 1998. Sea water temperatures in March and April 1998 rose to an average of 1.5°C above values measured during the same period in 1997, with daytime, low tide highs of over 32°C (Figure 1). Bleaching was first noticed in Kenya around March 15, 1998, and then rose to unprecedented levels of 50–90% of the corals along the entire Kenya coast. Mortality from bleaching appeared to peak about mid-May, and subsequently some bleached corals recovered, while others continued to die up until October. Following the coral bleaching in 1998, living coral Kiunga Temperature (°C) 33 32 31 30 29 28 27 26 25 1997–98 1992–93 1993–94 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Figure 1. Seawater temperature in shallow coral patch reefs in Kenya, measured using a hand-held thermometer during field visits. Curves are 7th-power polynomials to illustrate seasonal cycling. Data shown for 18-months January–June periods for 1992–93, 1993–94 and 1997–98. cover decreased significantly on all known reefs in Kenya. Table 1 illustrates the changes in various benthic cover categories on a reef in Malindi that had a stable coral community and normal cover characteristics from 1994–1998. Coral cover then decreased to 40% of prebleaching levels, while soft corals decreased to 10% of pre-bleaching levels. As a result of new available KENYA Lamu Table 1. Changes in benthic community structure as a result of bleaching (in% cover). Example of Malindi Marine National Park. M = mean, st. error = standard error of the mean. Malindi Malindi Watamu Indian Ocean Cover Before (1994) After (1999) mean st. error mean st. error Coral 35.7 2.46 14.7 4.63 Soft coral 9.6 1.96 1.0 0.42 Other 1.4 0.70 0.1 0.06 Mombasa Mombasa Kisite Algae Turf 31.2 4.58 59.6 7.82 Halimeda 7.0 2.39 5.7 2.61 Macroalgae 1.6 1.24 0.5 0.21 Coralline algae 3.8 1.40 8.7 3.68 Seagrass 0.1 0.07 1.3 0.66 Kenya’s coral reefs are divided between two main areas, a fringing reef system in the south (from Malindi to Kisite) and patch reefs and fore reef slopes in the north. After the 1998 bleaching event, the living coral reef cover has decreased on all known reefs in Kenya. Coral variables # Colonies 112.6 12.64 37.0 2.08 # Genera 19.8 1.77 8.7 0.88 – 33 –
substrate, the cover of algal turf increased by 200%. The number and diversity of coral colonies along sample transects decreased by a factor 3 and 2 respectively, with many small colonies remaining compared to the more numerous, but larger colonies before bleaching. About ten other sites have been visited by experienced coral reef researchers (including Kiunga, Lamu, Watamu, Vipingo, Kanamai, Mombasa, Galu, and Kisite), all suffering a similar fate, with coral cover at 10–50% of pre-bleaching levels. Bleaching was observed at all depths (to 20 m), with the highest impact and mortality at depths less than 2–3 m. Bleaching and mortality were highest in shallow habitats and pools, where water stagnation occurs, or where corals are regularly exposed to outflow of shallow (warm) lagoon waters and/or to mangrove and sediment influence. Bleaching and mortality were least in waveexposed habitats and locations subject to upwelling of cooler deeper water. Variability in space was a dominant feature observable, with different localized responses to a region-wide and ubiquitous threat. The impact of high temperature stress varied with habitat type and the suite of dominant species – wave zones and back-reef lagoons dominated by arborescent Acropora species were the most susceptible, and face loss of ecological function. Species and higher taxon-specific variability in bleaching was also high, ranging from 0–100% bleaching and mortality. Pocillopora, Stylophora and arborescent Acropora spp. were among the most susceptible corals, with close to 100% bleaching and/or mortality at some sites, even where exposed to high water motion. Other genera exhibited variable levels of bleaching and mortality even within the same species, at some sites low and at others severe. In general, where mortality levels were 50% and greater, sites on a scale of 100–200 m 2 lost up to 50% of their species and genus diversity (Table 1), though at a larger scale of several kilometers the loss of species was lower. The number of coral colonies recorded in transects dramatically decreased by up to 90% (Table 1, Figure 2), showing that the survival of corals Colonies per 10 m 2 100 75 50 25 0 hyp. 18 Figure 2. Number of coral colonies that were normal, bleached or dead at four sampling occasions in Malindi, from January 1998 to January 1999. The numbers above the columns indicate the number of 1 m 2 quadrats sampled each time. January data (# colonies) backcalculated from April and August. following bleaching can be very low; the number of living colonies was lower in January 1999, than that recorded for unbleached corals in April 1998, at the height of bleaching (Figure 1). OTHER IMPACTS OF BLEACHING No data has been collected so far to determine the impact of bleaching on other marine organisms, though extensive historical data exists for gastropods, sea urchins and fish. Similarly, previous socio-economic studies will provide good baselines for assessing the impact of coral bleaching and mortality on coral reef resource users. Coupled with the severe loss of coral cover and potentially reef vitality, the already high levels of subsistence fishing on many reefs in Kenya (at or above their maximum sustainable yields) suggest that fisheries may become increasingly unsustainable in the short term. The socio-economic impact of the bleaching on other sectors, such as tourism, is harder to predict, but the economic dependence on tourism in Kenya makes this an important sector for investigation. These two areas will comprise the principal focus of socio-economic investigations into the after-effects of the 1998 coral bleaching and mortality. 29 36 Jan-98 Apr-98 Aug-98 Jan-99 Normal Bleached Dead – 34 –
Page 2 and 3: CORAL REEF DEGRADATION IN THE INDIA
Page 4 and 5: Foreword Corals as organisms and co
Page 6 and 7: Table of contents EXECUTIVE SUMMARY
Page 8 and 9: Rationale Coral reefs throughout th
Page 10 and 11: STATUS REPORTS FROM DIFFERENT REGIO
Page 12 and 13: The South Asia region of the Indian
Page 14 and 15: man and Nicobar islands. Mainland I
Page 16 and 17: Table 1. (Cont.) Country Locations/
Page 18 and 19: International Year of the Coral Ree
Page 20 and 21: 72ºE Makunudu North Malosmadulu So
Page 22 and 23: has been a consequent lack of train
Page 24 and 25: Stoddart, D.R (1971). Environment a
Page 26 and 27: Table 1. Diversity of scleractinian
Page 28 and 29: 5ºS 71ºE 72ºE 73ºE Indian Ocean
Page 30 and 31: much higher in lagoons than on seaw
Page 32 and 33: Various corals in Chagos, 1999. A:
Page 36 and 37: MONITORING AND RESEARCH RELEVANT TO
Page 38 and 39: (17°20’S) and Bazaruto Island (2
Page 40 and 41: Locality Reef Description Results B
Page 42 and 43: Institute and from 24-30 March by D
Page 44 and 45: Tanga TANZANIA 39ºE 40ºE Bawe and
Page 46 and 47: Zanzibar noticed the rise in water
Page 48 and 49: Influence of coral bleaching on the
Page 50 and 51: Dead table-forming Acropora spp. af
Page 52 and 53: Horrill, J.C. & Ngoile, M.A.K. 1991
Page 54 and 55: The fringing reefs of Reunion are a
Page 56 and 57: platforms (21 km 2 ). As human acti
Page 58 and 59: Bleached and partly bleached Acropo
Page 60 and 61: Status report Mauritius DR JOHN R T
Page 62 and 63: OTHER RELEVANT WORK IN THE REGION T
Page 64 and 65: BLEACHING EVENT SST anomaly data in
Page 66 and 67: Remote sensing as a tool for assess
Page 68 and 69: parameters and apply correction and
Page 70 and 71: Coral bleaching effects on reef fis
Page 72 and 73: Chabanet et al., 1997; Öhman & Raj
Page 74 and 75: the status of the reef fish communi
Page 76 and 77: Letourneur, Y., Harmelin-Vivien, M.
Page 78 and 79: grow, but damage and loss of transp
Page 80 and 81: corals: a manual for coral reef use
Page 82 and 83: dependence on fisheries for income
Page 84 and 85:
REFERENCES Berg, H., Öhman, M.C.,
Page 86 and 87:
is an enigma. Everyone is in favour
Page 88 and 89:
solar cells is estimated to decreas
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LIST OF CORDIO PROJECTS 1999 - 89 -
Page 92 and 93:
lagoons will be studied to determin
Page 94 and 95:
South Asia Region Regional co-ordin
Page 96 and 97:
Central Indian Ocean islands Region
Page 98 and 99:
APPENDIX - 97 -
Page 100 and 101:
08.30 a.m.-09.00 a.m. Coral transpl
Page 102 and 103:
MAIZAN HASSAN MANIKU Director Gener
Page 104:
DR MOHIDEEN WAFAR Scientist Nationa
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