Appendix F. Uncertainty assessment for net exchange (N-Ex).

Uncertainty assessment for net exchange (N-Ex)

Appendix D. Uncertainty assessment for point source input (PS).

Uncertainty assessment for point source input (PS)

Appendix H. Uncertainty assessment for the Black Box (BB) terms.

Uncertainty assessment for the Black Box (BB) terms

Appendix G. Uncertainty assessment for marsh exchange (M-Ex).

Uncertainty assessment for marsh exchange (M-Ex)

Appendix E. Uncertainty assessment for groundwater input (GW).

Uncertainty assessment for groundwater input (GW)

DataSheet_1_Abrupt chlorophyll shift driven by phosphorus threshold in a small subtropical estuary.pdf

Chlorophyll trends in subtropical and tropical estuaries are under characterized and may reveal patterns not shared by their temperate analogues. Detection of trends requires long-term monitoring programs, but these are uncommon. In this study, we utilized an 18-year chlorophyll-a time series from 2002 to 2020 in Weeks Bay, AL, to detect and quantify trends in chlorophyll variability over multiple time scales. Our analysis included up to 30 years of contemporaneous data for variables such as river discharge, nitrogen, and phosphorus to relate the chlorophyll-a trends to environmental drivers. We detected an abrupt shift in chlorophyll-a that was linked to changes in phosphorus and hydrology. The shift followed an abrupt increase in total phosphorus concentration from upstream of the primary river system that discharges into Weeks Bay. Total phosphorus continued to rise after the abrupt shift, but there was no detectable change in chlorophyll-a. We propose that the exceedance of a total phosphorus threshold at 0.1 mg l-1, combined with a period of very low river discharge variability, induced the shift in chlorophyll-a. This shift opposed the pattern of proportional change usually observed as a result of nutrient enrichment. Not all monitoring stations underwent the abrupt shift, which demonstrated the complexity of phytoplankton response to environmental drivers and the significance of spatial differences even over small estuaries.</p

An Approach to Developing Numeric Water Quality Criteria for Coastal Waters Using the SeaWiFS Satellite Data Record

Human activities on land increase nutrient loads to coastal waters, which can increase phytoplankton production and biomass and associated ecological impacts. Numeric nutrient water quality standards are needed to protect coastal waters from eutrophication impacts. The Environmental Protection Agency determined that numeric nutrient criteria were necessary to protect designated uses of Florida’s waters. The objective of this study was to evaluate a reference condition approach for developing numeric water quality criteria for coastal waters, using data from Florida. Florida’s coastal waters have not been monitored comprehensively via field sampling to support numeric criteria development. However, satellite remote sensing had the potential to provide adequate data. Spatial and temporal measures of SeaWiFS OC4 chlorophyll-<i>a</i> (Chl_RS-<i>a</i>, mg m^–3) were resolved across Florida’s coastal waters between 1997 and 2010 and compared with in situ measurements. Statistical distributions of Chl_RS-<i>a</i> were evaluated to determine a quantitative reference baseline. A binomial approach was implemented to consider how new data could be assessed against the criteria. The proposed satellite remote sensing approach to derive numeric criteria may be generally applicable to other coastal waters