Developing a Real-Time Trophic State Index of a Seawater Lagoon: A Case Study From Dapeng Bay, Southern Taiwan

Algal blooms over the past years have caused considerable worldwide impacts on marine ecology, aquaculture, recreational activities, and human health. Therefore, there is an urgent need to develop indices for evaluating the nutritional status of seawater as a means of predicting algal blooms. A long-term water quality monitoring dataset from Dapeng Bay, Southern Taiwan, indicated that seawater dissolved oxygen (DO) concentrations and pH were significantly correlated with algal abundance. Using this dataset, we then developed a real-time trophic state index (RTSI) by (1) referring to the seawater nutrient grading system defined by Carlson's index and (2) incorporating an algorithm based on the relationship between DO, pH, and eutrophication status. The RTSI was superior to contemporary indices in its simplicity, as no complicated nutrient or chlorophyll a (Chl a) measurements were required, and real-time data were displayed on a personal computer. The index is sensitive to changes in seawater quality that will be of aid to managers.

Automated summary

Algal blooms have had significant global impacts on marine ecosystems, aquaculture, recreational activities, and human health. Therefore, there is an urgent need for indices to evaluate seawater nutritional status for predicting algal blooms. This study developed a real-time trophic state index (RTSI) using a long-term water quality monitoring dataset from Dapeng Bay, Southern Taiwan. The RTSI, which is simple and does not require complicated measurements, showed sensitivity to changes in seawater quality and can aid managers in monitoring and managing algal blooms.