University Student Projects

Academic Year 2006 - 2007

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Influence of local anthropogenic terrestrial runoff on energy subsidies and trophic dynamics of coral reefs in Tobago.

[Final Report] (538KB)

J.R. Foley (james.foley@ncl.ac.uk)
MSc Tropical Coastal Management
Department of Tropical Coastal Management
School of Marine Science & Technology
Newcastle University, Newcastle, NE1 7RU, United Kingdom

Abstract

	Images from the Field
	Preparation of samples for mass spectrometer analysis
	BRT Scientific Diver & Marine Biologist Richard Parkinson, James Foley and CCC Scuba Instructor Angelie Peterson in the field. Image courtesy Angelie Peterson.

Coral reefs in Tobago have exhibited accelerated rates of degradation and reduced biodiversity over the past two decades [1]. Signs of eutrophication indicate elevated nutrient inputs to be the cause, particularly phosphorus (P) and nitrogen (N) [2]. Opinions differ on the cause of elevated N and P concentrations in coastal waters around Tobago. Stable isotope analysis (SIA) reveals higher nitrogen isotope ratios (d15N) with increasing proximity to point sources, such as sewage outfalls, fish processing plant discharges etc. [1]; [3]; [4], and non-point sources (deforestation, agricultural and urban runoff) of terrigenous anthropogenic effluent [4]. However, signatures of Orinoco flooding in skeletally dense bands in radiograph scans of cross-sections of corals indicate influence on Tobago reefs by seasonal influxes of nutrient-rich, high turbidity freshwater runoff from the Orinoco River in Venezuela during the wet season (June to December) [5], and particulate organic matter (POM) and sediments transported from the Amazon River by the coastal Guyana current [6]. A likely reality is that reef degradation in Tobago has resulted from the combined effects of all these factors. Baseline data is needed to assess the relative importance of continental riverine nutrient inputs versus local nutrient inputs in influencing coral reef food webs, and to evaluate the potential roles of these inputs as energy subsidisers acting to promote productivity on Tobago’s coral reefs. In contribution to the larger-scale project currently being conducted by the Buccoo Reef Trust (BRT) in Tobago, this project uses stable isotope analysis (SIA) to determine relative influence of local runoff on reef function & tropic cascades during the dry season, at six sites subject to varying degrees of local anthropogenic effluent impact on the Caribbean coast of Tobago. This study will test the null hypothesis that there is no effect of sewage on d15N during the dry season, updating existing quantitative data pertaining to the relevance of local anthropogenic nutrient inputs on coral reefs in Tobago, and providing essential comparison with subsequent wet season data. Combined d15N and d13C data will provide an understanding of trophic relationships in local coral reef food webs, serving as valuable information for use in the context of the larger-scale BRT project, and thus contributing to the continuum of research efforts leading towards sustainable and long-lasting management solutions for coral reef degradation in Tobago. This will potentially provide an effective model for tropical coastal management strategies on both regional and global scales.

Collaborators

Prof. Nicholas Polunin, Newcastle University, UK;
Dr Jennie Mallela, University of the West Indies, Trinidad;
Dr Chris Harrod, Queens University, Northern Ireland, UK;
Dr Richard Langton, University of Maine, USA & Buccoo Reef Trust, Tobago;
Dr Owen Day, Buccoo Reef Trust, Tobago.

References

[1] Lapointe, B. E. (2003) Impacts of Land-Based Nutrient Pollution on Coral Reefs in Tobago. Buccoo Reef Trust Website.

[2] IMA (1994) The formulation of a management plan for the Buccoo Reef Marine Park. Volume 3. Biological investigations and water quality monitoring. Institute of Marine Affairs. Prepared for the Tobago House of Assembly 58pp.

[3] John, G. M. (1996) Quantitative Characterisation of Land-Based Sources of Marine Pollution in the Vicinity of the Buccoo Reef Marine Park, Tobago. University of the West Indies. (Unpublished Thesis).

[4] Young, K. (1998) An Ecological Assessment of Buccoo Reef/Bon Accord Lagoon Complex, Tobago: ‘Evaluating the Trade-offs between Users of Marine Protected Areas in the Caribbean.’ Literature Review for UEA/UWI Collaborative Project.

[5] Risk, M. J., Van Wissen, F. A., Carriquiry Beltran, J. (1992) Schlerochronology of Tobago Corals: A record of the Orinoco? Proc. 7th Int. Cor. Reef. Symp., Guam, Vol 1.

[6] Medina, E, Francisco, M, Sternberg, L., Anderson, W. T. (2005) Isotopic signatures of organic matter in sediments of the continental shelf facing the Orinoco Delta: Possible contributions of organic carbon from savannas. Estuarine, Coastal and Shelf Science 63:527-536.

[7] Humboldt-Innovation GmbH, Humboldt Universität zu Berlin, Ziegelstraße 13c, 10117, Berlin, Deutschland http://www.humboldt-innovation.de/home/index.shtml