**5. Discussion and conclusion**

In this study, the potential of remote sensing data for modeling and estimating the time series of chlorophyll-A concentration with field data for the coastal region of Khor Tiab was evaluated.Coastal Aerosol, Blue and green band-based bio-optical models (OC2 and OC3) were applied to Landsat-8 satellite multispectral data to estimate chlorophyll-A concentrations in the coastal area. The results of this study show that OC2 and OC3 bio-optical models have a high correlation with field data sampled from the coastal waters of Tiab estuary so that the statistical parameter values R2 and RMSE in the OC2 model with field data were equal to 0.91 and 0.13, respectively. While the results of statistical parameter R2 and RMSE in the OC3 model were evaluated with field data with a slight difference of 0.88 and 0.16, respectively. Due to the good performance of the OC2 algorithm compared to the OC3 algorithm with field data, this algorithm was selected and used to estimate the time series of chlorophyll-A concentration in the Tiab estuary. As the time series map shows, the concentration of chlorophyll-A in April and November compared to July has a relatively high concentration of chlorophyll that follows the natural conditions, which is due to the fact that in April and November the sea temperature is low and cold. This has increased the concentration of chlorophyll-A in the region, while the concentration of chlorophyll-A has decreased significantly in July because the sea temperature is high this month and is completely correlated with natural conditions. In fact, there is an inverse relationship between chlorophyll-A concentration and sea surface temperature, which fully illustrates the Remote Sensing data used in this study. The end result of this study indicates that remote sensing data is a much better alternative to field operations due to its cost and time consuming nature. Finally, the participants of this study are suggested to use more field data to calibrate the Remote Sensing data in order to estimate the chlorophyll-A concentration in order to obtain better results.
