Long-term trends in water quality parameters in coastal waters of Puerto Rico

Abstract

Ocean color remote sensing technology has been widely used in coastal water quality research. Of particular importance is the influence of river discharge on turbidity and chlorophyll concentration in coastal areas, which is seasonally and spatially variable. The coastlines and landscapes of Puerto Rico exhibit regional variability. In this study, Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) and Moderate Imaging Spectroradiometer (MODIS) Aqua satellite chlorophyll a concentration ([Chla]) and diffuse attenuation coefficient at 490nm (Kd490) data, at high spatial resolution, in combination with river streamflow discharge from the United Stated Geological Survey (USGS) were used to assess long-term trends impacting the diverse (i.e., Western, Northern, Eastern, and Southern) coastal waters along Puerto Rico for the years 1998 to 2013. The evaluation of Kd490, [Chla], river discharge time-series, and their correlation coefficients from 2km to 16km from the river mouth showed seasonal and spatial variation for the four regions of the island. Chlorophyll a concentration was the main contributor to turbidity in coastal waters of Puerto Rico during 1998 to 2013. Higher turbidity trends were primarily due to increased [Chla] (i.e., biogenic particles) compared to inorganic sediments, as shown by the high correlation between Kd490 and [Chla], especially during the dry season, compared to the rainy season. Kd490 and [Chla] were not related to river discharge.