GCRMN_COI_2017-Western Indian Ocean Reef Status

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Coral reef status report for the Western Indian Ocean (2017) Global Coral Reef Monitoring Network 2.8.3 Status and trends Total hard and soft coral cover at the Nine-mile Reef monitoring site (Central Complex) has decreased gradually since monitoring commenced, from 67.5% in 1993 to 55.9% in 2014 (fig. 2.8.2b). The declining cover of soft corals over the 21-year period from 54.3% to 37.7% is primarily responsible for this (Porter and Schleyer 2017). The rate of soft coral cover decline is almost 1% per annum. Contrastingly, hard coral cover increased from 13% in 1993 to 18% in 2005, where it has since stabilised and remained constant (fig. 2.8.2a). a b Figure 2.8.2: a) Trend in hard coral cover on South Africa’s long-term monitoring site from 1992- 2014 (dark blue line); b) Comparison of cover of hard corals (HC, blue, top) and soft corals (SC, pink, bottom) at the site from 1993-2014. NATIONAL CHAPTERS Recruitment success of both soft and hard corals has been erratic between years and has not shown any trends for most of the monitoring period, except from 2010, when a large increase particularly in hard coral recruitment success occurred (Porter and Schleyer 2017) (fig. 2.8.3). Subsequent to 2010, recruitment success of hard corals has declined sharply to previous years’ levels. However, soft coral recruitment success has continued to increase from 2010 until 2013. Mortality of all corals combined, as well as soft and hard corals individually, displayed similar patterns to recruitment success, i.e. values have been erratic for most of the monitoring period but have begun to increase consistently from 2011 to 2014. Continued monitoring will determine if these trends continue. Mobile invertebrates and fish populations have not been monitored during this time period; a revision of the monitoring protocols in recent years will initiate these. 124
Coral reef status report for the Western Indian Ocean (2017) Global Coral Reef Monitoring Network a b Figure 2.8.3.: Recruitment success and mortality for soft coral a) and hard coral b) at Nine-mile Reef from 1994-2014. 2.8.4 Coral Bleaching 2016 Coral bleaching surveys were conducted in May 2016 at five sites on Two-mile Reef in the Central Complex. At each site, six to seven 10-m long transects were haphazardly placed on areas of reef, and the point-intercept method employed to measure intensities of bleaching using an underwater video recorder. Bleaching severity was assessed within the immediate vicinity of each point and scored on a 5-point scale as: no bleaching, partially bleached or pale but not white, white, bleached and partly dead and recently dead. A total of 700 points were assessed along transects placed at depths of 12-18 m. Mean ± standard deviation was then calculated for the proportion of coral cover bleached using sites as replicates. Bleaching of the corals ranged from 4.1 to 17.5%, with an average ± SD of 9.4 ± 5.9%. Montipora was by far the most commonly bleached genus, comprising 63% of the bleached coral cover followed by Favia (10%) and Pocillopora (7%). When corals were bleached, 49% were pale but not white, whilst the remaining 51% were white. At the time of the surveys, and four months later in follow up surveys, no bleaching-related mortality was detected. Bleaching has been previously recorded on several occasions in the region (see Timeline) with highest levels recorded in 2000 (Celliers and Schleyer 2002). In 2000, Montipora was similarly found to be the most susceptible genus to bleaching, and a comparable proportion of the coral colonies showed partial bleaching or paling (44%), or full-white bleaching (47%). 2.8.5 Drivers and pressures South Africa has a population of approximately 55 million and in 2015 had a GDP output of 317.3 billion US dollars (IMF 2015; Statistics South Africa, 2016). Economic growth was marginally above 2% for the period 2008 to 2012 (Statistics South Africa, 2016). Unemployment levels are relatively high at 25.5% (Statistics South Africa, 2016). The majority (63%) of people have completed primary education, whilst only 27.7% and 2.7% have completed secondary and bachelors-degree level education respectively (Statistics South Africa, 2011). South Africa’s Ecological Footprint stands at 2.59 per person per NATIONAL CHAPTERS 125
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