Romeo (2014) Tracing Anthropogenic Nutrient Inputs Using δ15N Levels in Algae Tissue Koh Tao, Thailand

In 2014, Laurence Romeo completed a research project on Koh Tao using macro-algae and water testing to use a bioassay method of tracking the sources of anthropogenic pollutants around Koh Tao.


Full Citation

Romeo, L. (2014) Tracing Anthropogenic Nutrient Inputs Using δ15N Levels in Algae Tissue Koh Tao, Thailand. Master’s Thesis, MAS Marine Biodiversity and Conservation, CMBC, Scripps Institute of Oceanography, UCSD. 29 pp.



It has been estimated that up to 25% of the ocean’s coral reefs are under threat from increased sediments and nutrients that are washed from the terrestrial environment due to the clearance and development of nearby land (Burke, 2011). Jackson et al. (2001) suggested that, in combination with overfishing, nutrient enrichment was the major factor in the decline of coral reefs worldwide. With the pressure on coral reefs increasing, effective mapping of tropical coastal areas affected by anthropogenic nutrient input is essential in conserving existing reefs and to also restore reefs that may already be degraded (Lin et al., 2007). To map anthropogenic nutrient input as part of a successful management strategy both the level of enrichment and the source of nutrient input is required.

A bioassay involves the use of a biological organism to test for the relative strength of a substance within the natural environment. A well established bioassay technique is the use of naturally stable Nitrogen (N) isotope ratios in algae tissue, which can be used as a proxy for anthropogenic nutrient inputs from human sewage and also help detect the source of these nutrient inputs into the coastal ecosystem.

This study attempts to quantify the amount, and find the source, of nutrient inputs into the marine environment on a developing tourist island in Thailand. Chemical data in the form of nutrient concentrations are used as an indication of the amount of nutrients present; while δ15N values in algae tissue are used to indicate the source of nutrients and whether or not they are of anthropogenic origin.


Download the full paper here