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clean-waters-and-sediments.md
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clean-waters-and-sediments.md
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# Clean Waters & Sediments
## Water Quality Decision Matrix
Water quality in Tampa Bay has improved steadily in recent decades due to pollution reduction projects and restoration of bay habitats. Tampa Bay has generally met water quality standards in each bay segment, excluding Old Tampa Bay, since 2006.
The water quality report card is produced annually to track status and trends of water quality conditions in each of the four major bay segments. This tool provides a simple "stoplight" graphic using water quality data provided by the Environmental Protection Commission of Hillsborough County. The report card synthesizes thousands of water quality records to understand annual and seasonal variation in chlorophyll concentrations and water column light attenuation. Chlorophyll provides a measure of algae growth in the water column and light attenuation provides a measure of potential shading from algae growth that can limit seagrass growth. Excess nutrient pollution from atmospheric, wastewater and stormwater sources can cause excess algae growth. The goal of the report card is to assess water quality trends that may be harmful for bay habitats, including conditions that are favorable for seagrass growth, to inform management activities that support a healthy environment.
Conditions in 2021 were ...
Water Quality Report Card data page: https://tbep.org/water-quality-report-card/
## Total Nitrogen Loading
In 2011, the FDEP approved numeric nutrient criteria (NNC) for each of the bay segments described by the Tampa Bay Nitrogen Management Consortium in the 2009 Tampa Bay Reasonable Assurance (RA) Update. The Tampa Bay NNC represent a total "nitrogen delivery ratio" [i.e. total nitrogen load (tons/yr) per unit water (million m3) delivered] to each of the RA segments and have been codified as FDEP Estuary Nutrient Regions in F.A.C. 62-302.532. The NNC are based on the average of 1992-1994 ratios for each of the RA segments, and therefore, account for year-to-year variation in rainfall and set a baseline for the assessment of future loading conditions.
Despite an increasing population in the Tampa Bay metropolitan area, per capita TN loading to the bay continues to decrease over time (ancillary figure below), and the amount of TN delivered per unit water has also decreased over time in each of the major bay segments. To date, hydrologically-normalized total loads to Tampa Bay are at the lowest levels since they have been estimated (1985-2020, refer to 5-panel summary).
## Tidal Creeks
Tidal creeks or tributaries are essential habitats in the Tampa Bay estuary and are important focal points for understanding watershed inputs that affect water quality. A fundamental goal of the Tampa Bay Estuary Program is to develop effective nutrient management strategies to support the ecological function of tidal tributaries. In partnership with Sarasota Bay NEP, Coastal & Heartland NEP, and local government and agency stakeholders, a tidal creek assessment framework was developed to evaluate the environmental health of these valuable ecosystems.
The tidal creek assessment framework supports tracking of water quality management goals and can help refine restoration and management plans in priority tributaries, including those in need of hydrologic restoration that can support critical nursery habitats for sportfishes. Similar to the water quality report card, tidal creeks are assigned to different categories that describe current conditions and inform management actions that support protection or restoration of bay habitats.
Tidal creeks are assigned to one of five categories: Monitor: Creek is at or below nitrogen concentrations that protect individual creek types within the larger population of creeks. Caution: Creek nutrients showing signs of elevated nutrient concentrations that may increase risk of eutrophic condition. Investigate: Creek nutrient concentrations above margin of safety to protect creek from potential impairment. Prioritize: Creek nutrient concentrations have exceeded regulatory standard for associated freshwater portion of ghe tributary indicating that actions are needed to identify remediative measures to reduce nutrients in the creek. No Data: Insufficient data exist to assess tidal creeks condition, additional monitoring is needed.
The current assessment period (2021) indicates that nine creeks had a "Prioritize" score, ten had an "Investigate" score, nine had a "Caution" score, and 58 had a "Monitor" score. The remaining 142 creeks in the Tampa Bay watershed had insufficient data for the current assessment period to assign a category.
Link to tidal creeks data page: https://tbep.org/tidal-creeks/
## Tampa Bay Benthic Index
Benthic invertebrates are a group of relatively small organisms (microscopic to visible to the naked eye) that live the majority of their life cycles in or near bay bottom sediments. They are a food source for small fish and crustaceans and may provide some water quality benefits through sediment removal via filtration during feeding (similar to oysters). Tampa Bay supports many different benthic organisms. The type of benthos varies depending on the salinity, sediment type, temperature, dissolved oxygen, and presence of excess nutrients and/or toxic contaminants.
The Tampa Bay Benthic Monitoring Program was started in 1993, and partners include the Environmental Protection Commission of Hillsborough County, and Hillsborough, Manatee and Pinellas Counties. Our partners monitor benthic invertebrate population characteristics and environmental conditions that affect these organisms, including percent silt-clay, sediment contaminant levels, and dissolved oxygen.
The Tampa Bay Benthic Index (TBBI) provides an estimate of the health of benthic invertebrate populations in Tampa Bay. The TBBI is scaled from 0-100 with values <73 classified as "Degraded", from 73-87 as "Intermediate", and >87 as "Healthy". The average TBBI score increased from 1993-2017, and the bay-wide median TBBI was continuously in the "Healthy" range from 2013-2017. During that time frame, the highest TBBI values were observed in the main portion of Tampa Bay (Old Tampa Bay, Middle Tampa Bay, and Lower Tampa Bay), while lower values were found in Hillsborough Bay and the Manatee River.
Human-caused pollution can contaminate aquatic sediments with various dangerous chemicals and heavy metals. As polluted water enters a waterbody, metals and other chemicals may adsorb or attach to suspended solids in the water column. These solids eventually sink to the bottom and integrate into the existing sediments. Toxicological studies have shown that many of these substances can affect the growth and survival of benthic organisms.
Sediment contaminant levels are assigned a letter grade (A, B, C. D, F) by averaging the scores of multiple contaminants according to the mean Probable Effects Level ratio, a measure of how likely a contaminant is to have a toxic effect on invertebrates. From 1993-2017, most sites fell within the "C" range, while some "D" and "F" graded sites were found, primarily in Hillsborough Bay, the Manatee River, and Boca Ciega Bay.
Link to benthic data page: https://tbep.org/tampa-bay-benthic-index/