Seasonality of Selected Surface Water Constituents in the Indian River Lagoon, Florida

Abstract

Seasonality is often the major exogenous effect that must be compensated for or removed to discern trends in water quality. Our objective was to provide a methodological example of trend analysis using water quality data with seasonality. Selected water quality constituents from 1979 to 2004 at three monitoring stations in southern Florida were evaluated for seasonality. The seasonal patterns of flow-weighted and log-transformed concentrations were identified by applying side-by-side boxplots and the Wilcoxon signed-rank test (p < 0.05). Seasonal and annual trends were determined by trend analysis (Seasonal Kendall or Tobit procedure) using the U.S. Geological Survey (USGS) Estimate TREND (ESTREND) program. Major water quality indicators (specific conductivity, turbidity, color, and chloride), except for turbidity at Station C24S49, exhibited significant seasonal patterns. Almost all nutrient species (NO(2)-N, NH(4)-N, total Kjeldahl N, PO(4)-P, and total P) had an identical seasonal pattern of concentrations significantly greater in the wet than in the dry season. Some water quality constituents were observed to exhibit significant annual or seasonal trends. In some cases, the overall annual trend was insignificant while opposing trends were present in different seasons. By evaluating seasonal trends separately from all data, constituents can be assessed providing a more accurate interpretation of water quality trends.

Three dimensional water quality modeling of a shallow subtropical estuary

“…Lake Okeechobee is a large eutrophic system subject to cyanobacterial blooms (Havens et al, 1996). Compared with freshwater originated from the SLE watershed, the lake water released into the SLE contains elevated N concentrations (Qian et al, 2007). One algal bloom during major Lake Okeechobee releases occurred in May 2000.…”

Trend Analysis of Nutrient Concentrations and Loads in Selected Canals of the Southern Indian River Lagoon, Florida

“…The two seasons were divided by evaluating the plots of mean precipitation variation in a year and selecting the 'break points' between seasons as the section of the time series that exhibited the greatest change (Qian et al 2007). …”

“…Annual nutrient loads exhibited seasonality, which means nutrient loads exhibited different magnitudes and changes during different seasons (the dry and wet season) (Qian et al 2007). Most of the nutrient species showed greater loads in the wet season in comparison to the dry season (for example, Fig.…”

Characterization of turbidity in Florida's Lake Okeechobee and Caloosahatchee and St. Lucie Estuaries using MODIS-Aqua measurements

“…In another study, Qian et al (2007) examined in situ measurements from 1979 to 2004 of multiple parameters in the same region, turbidity being one of them. Researchers found no clear seasonal trend in all three stations for turbidity.…”