Jamaica’s ]]>
2 quadrats. Photographs ]]>
Siderastrea sidera -which dominated Rackham’s Cay before dredging- was consistently present in low coverage. Colonization by species of Acropora and
Scolymia indicate slower but better succession at 10m. Ten years following dredging activities, colonization and recruitment have been slow but successful at 5m and 10m; species previously described as abundant lead the colonization. We recommend limiting coral relocation activities to depths not exceeding 10m.
Key words: Rackham’s Cay, new ]]>
Resumen
Sucesión primaria de una comunidad de coral y algas en el nuevo sustrato vertical en el Cayo de ]]>
m2. Las fotografías fueron analizadas usando “Conteo de Puntos de Coral”. A 15m de profundidad, no se observó ninguna colonización de especies coralinas o algas. Las algas calcáreas y carnosas dominaron inicialmente los 5m de profundidad y mostraron una disminución gradual en el tiempo. Algas calcáreas dominaron los 10m de profundidad y también mostraban un incremento gradual en los 4 años. Corales pétreos en 5m y 10m de profundidad mostraron un % de cobertura bajo y lenta colonización, con la menor profundidad y ]]>
Acropora y Scolymia son indicación de sucesión más lenta pero ]]>
Palabras clave: Cayo Rackham, nuevo ]]>
Jamaica’s trans-shipment industry is amongst the largest in the Caribbean with 90% of trans-shipment activities occurring in the Kingston Harbour (latitude 17º58’N and longitude 76º48’W). This has been a lucrative industry for the Jamaican government, with current plans to diversify and expand this ]]>
Kingston Harbour’s main ship channel which runs on the east side of the Port Royal Cays is approximately 16.5m deep and is populated with the patch and fringing coral reefs known to be found throughout the area. The Port Royal Cays area has seven small cays, including Rackham’s Cay which is positioned on the south-west edge of the ship channel. To facilitate the improved ]]>
The dredging ]]>
In 2009 the Centre for Marine Sciences (CMS) of the University of the West Indies (UWI) received a grant from the Environmental Foundation of Jamaica (EFJ) to monitor the newly created vertical substrate at Rackham’s Cay for five years. The ]]>
The aims of this study were therefore:
1. To indicate the ]]>
2. To assess pioneer coral and algal community development using taxonomic composition and % cover.
3. To identify the water depth for optimal coral recruitment in the area of the ship channel near Rackham’s Cay.
Materials and Methods
The successional changes on the new vertical substrate (wall) were assessed between 2009 and 2012. Bi-annual photographs of fixed 1 m2 quadrats at 5m, 10m and 15m depths were taken during the period. A total of three 1 m2 permanent quadrats were randomly established at each depth along the vertical substrate of the providing a total of nine permanent quadrats. Photographs were taken with the camera positioned 1 m above the substrate and analyzed using Coral Point Count with Excel extensions (CPCe) version 3.5 software (Kohler & Gill, 2006). Genera and species, where possible, were identified from the images of the quadrats with the use of Human & DeLoach (2003) with checks of Coralpedia (http//coralpedia.bio.warwick.ac.uk) as a cross-reference. Tracing each organism identified (using the area measurement feature of CPCe) and calibration of the image, allowed the programme to compute the area occupied by the organism in question as a percentage of the total quadrat area (percentage cover). The percentage cover of major organisms/substrate categories measured over time at each depth was checked for normality and transformed where necessary (Sokal & Rohlf, 1981) before one-way analysis of variance (ANOVA, p = 0.05), tests were applied, using Statistica V.7, to indicate whether significant variability existed between depths and years. Diversity was calculated by the CPCe programme using the Shannon-Weaver Index (Kohler and Gill, 2006). Results
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Analysis of the photographs revealed that only quadrats located at 5m and 10m depths had live species present throughout the study period. Examination of quadrats at 15m indicated silt covered carbonate material as no colonization by algae, sponge or coralline species was observed at the 15m depth.
Species identification: Five ]]>
Undaria agaricites, Acropora palmata, Montastrea faveolata, Siderastrea siderea and Scolymiacubensis however they were observed at different depths and established at different times. U. agaricites and M. faveolata were identified from the pictorial data capture but were not captured in the random data capture based on the CPCe method employed. The algae observed were only identified to genus level. Those identified were Halimeda spp. ]]>
Caulerpa spp., Dictyota sp., Sargassum sp., Udotea sp. and an unidentified encrusting algae. Halimeda spp. had the greatest percentage cover (13.75 % cover at 5m and 31.1 % 10m depths) and comprised the dominant genera of calcareous algae. The vertical wall of the Rackham Cay was colonized primarily by algae with ]]>
Species and community changes: While the assessment of the photographic records at Rackham’s Cay suggested subtle changes in the community over time and depths, diversity was the only parameter that varied significantly over the years (ANOVA, p = 0.037), with only hard corals (ANOVA p = 0.004) and calcareous algae (ANOVA, p = 0.039) varying significantly with depth. ]]>
The algae Caulerpa spp., Halimeda spp. and Dictyota sp. were present at the 5m depth on each sample occasion. However, the abundance as indicated by % cover was variable, increasing from the first sample occasion to a maximum at the second or third sample occasion and declining thereafter (Figure 1). Other common species such as sponge and the coral Siderastrea siderea did not demonstrate maximum % cover until the fourth and fifth sample occasion. Species such as Agaricia agaricites, Sargassum spp., a species of gorgonian and the coral Acropora palmata all demonstrated successional changes as they were present on some sample occasions for one, two or three occasions then later would disappear at subsequent sample occasions (Table 1). It was also observed that A. palmata replaced the gorgonian species which had earlier replaced Agaricia agaricities, ]]>
The species pattern was similar at the 10m depth, but with different species being involved in the successional changes. Caulerpa spp.,
Dictyota sp., Halimeda spp., the sponge and Siderastrea siderea were always present with % cover maxima on sampling occasion 4 for Dictyota sp. and Halimeda spp. and occasion 2 for S. siderea and the sponge (Figure 2). In these deeper waters Udotea sp. and an encrusting alga, which were ]]>
Scolymiacubensis and a gorgonian were added to the species composition in the quadrats, providing further successional evidence. ]]>
Agaricia agaricities being present on the 4th occasion and A. palmata on the 5th sampling occasion as species change over time continued (
Table 2).
Community change over time, as demonstrated by the significant (ANOVA, p = 0.037) change in diversity, also indicated that communities at 5m were more diverse that those at 10m for each sampling occasion (Figure 3). Moreover the difference in ]]>
Figure 3).
Discussion
The study focused on the medium to long term changes occurring on the newly created bare vertical substrate referred to as the “cut face” of the cay. There are not many examples of colonization of new hard substrate by corals in the Caribbean. Most studies describe primary colonization in relation to artificial substrates (Vermeij, 2006) or newly created volcanic rock in areas outside the Caribbean (e.g. Grigg & Maracos, 1974, Tomascik, ]]>
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With the absence of a pre-dredging survey, it is impossible to determine the exact nature of the benthic community at the specific depths assessed in this investigation. However, studies in the general area of the Port Royal cays gave insight to the dominant members of the community (Mendes, 1992; Miller, 1996). Throughout this study, the dominance of calcareous and fleshy algae was as reported previously (McNaught, 2007; NEPA, 2012), with the concomitant overall low cover and slow colonization of hard corals and shallower depth having greater coral coverage. Previous reports also ]]>
Siderastrea siderea dominated Rackham Cay before dredging (Mendes, 1992; McNaught, 2007; Center for Marine Sciences, 2005) and therefore would be expected to colonize fastest and be the dominant coral species. Current data supports this suggestion, with Siderastrea siderea
being present in all quadrats and on all sample occasions but with very low percentage cover. With no colonization observed at 15m it is clear that the threshold for recovery in the area of Rackham’s Cay is between 10 and 15m. This threshold requires further investigation to identify the causative factors.
The primary community succession ]]>
Halimeda, Dictyota and Caulerpa) as well as the coral Siderastrea siderea dominated with sponges, while the later introduction of gorgonians and the once Jamaican dominant coral Acropora palmata, suggest the seral stage has begun. The community in deeper waters (10m) demonstrated additional successional rigour with the coral Scolymiacubensis, a seral deep water ]]>
Udotea sp. disappearing at the same time. Furthermore, where the species replacement trend was not observed the more widely observed successional trend of change in abundance of common species over time was also observed at both depths. Although only sampled over a period of four years, the successional trends at Rackham’s were clear.
The difference in communities at 5m and 10m was supported by the results of the diversity index, where diversity at 5m was consistently higher than that at 10m with the difference increasing with continued succession. Communities in deeper waters are expected to be less diverse resulting from the reduction in light, temperature and nutrient levels, especially adjacent to a major land based source of stress. As succession proceeds, species diversity ]]>
The success of coral reef communities in close proximity to the Kingston Harbour is documented as being low (Mendes, 1992; Miller 1996). Even without the additional human disturbance of vertical cutting of the reef structure, these ]]>
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The poor colonization, of coral reefs on Rackham’s Cay new vertical substrate may be an indicator that more careful planning and mitigation should be a part of future projects of this nature. The area would be more likely to show coral colonization if parent material was installed there following the completion of dredging. This is particularly true for species such as Acropora palmata which reproduces significantly ]]>
A number of recommendations can be derived from the current study. Without pre-dredging base line data, while the dramatic cut face produces opportunities for the study of ]]>
Acknowledgments
We would like to thank the Environmental Foundation of Jamaica for providing the grant funding to ]]>
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1. Discovery Bay Marine Laboratory, PO Box 35, Discovery Bay, St. Ann, Jamaica
2. Department of Life Sciences, Mona Campus, University of the West Indies, Kingston 7, Jamaica; mona.webber@uwimona.edu.jm
3. Centre for Marine Sciences, Mona Campus, University of the West Indies, Kingston, Jamaica
Received 04-X-2013 Corrected 02-I-2014 Accepted 24-III-2014