Abstract
Coastal water-quality is both a primary driver and also a consequence of coastal ecosystem health. Turbidity, a measure of dissolved and particulate water-quality matter, is a proxy for water quality, and varies on daily to interannual periods. Turbidity is influenced by a variety of factors, including algal particles, colored dissolved organic matter, and suspended sediments. Identifying which factors drive trends and extreme events in turbidity in an estuary helps environmental managers and decision makers plan for and mitigate against water-quality issues. Efforts to do so on large spatial scales have been hampered due to limitations of turbidity data, including coarse and irregular temporal resolution and poor spatial coverage. We addressed these issues by deriving a proxy for turbidity using ocean color satellite products for 11 Gulf of Mexico estuaries from 2000 to 2014 on weekly, monthly, seasonal, and annual time-steps. Drivers were identified using Akaike’s Information Criterion and multiple regressions to model turbidity against precipitation, wind speed, U and V wind vectors, river discharge, water level, and El Nino Southern Oscillation and North Atlantic Oscillation climate indices. Turbidity variability was best explained by wind speed across estuaries for both time-series and extreme turbidity events, although more dynamic patterns were found between estuaries over various time steps.
Highlights
The quality of estuarine and other coastal waters is a complex function of hydrological, meteorological, oceanographic, and human drivers [1,2,3,4]
We used satellite data from the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) sensor flown on the Terra satellite to derive a proxy for turbidity
If a discharge dataset was missing more than 25% of daily observations, that discharge dataset was considered too sparse for evaluation and excluded from further analyses
Summary
The quality of estuarine and other coastal waters is a complex function of hydrological, meteorological, oceanographic, and human drivers [1,2,3,4]. The relative influence of these processes affects water-quality trends, variability, and the occurrence of extreme water-quality events. Identifying the primary drivers of such events can be useful for management and mitigation purposes. A state of emergency was declared in two Florida counties in 2016 as a result of thick algal mats growing along highly populated coastal waterways in the St. Lucie and Caloosahatchee estuaries, causing massive fish kills [5]. Lucie and Caloosahatchee estuaries, causing massive fish kills [5] This emergency was caused by the release of nutrient-rich waters from Lake Okeechobee. A commentary published by Michalak [5] called for targeted research to determine which environmental conditions, and in what combination, increase the likelihood of extreme water-quality issues
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