Jan 27 2021
Water in the Chesapeake Bay has long been polluted by nutrients, leading to water quality degradation. But researchers at the University of Maryland Center for Environmental Science’s Horn Point Laboratory have reported certain improvements in the Choptank River on Maryland’s Eastern Shore.
The data presented here indicate that public and industrial investments in reductions of atmospheric emissions and upgrades to wastewater treatment plants have improved estuarine water quality in the Choptank.
Tom Fisher, Professor Emeritus, Center for Environmental Science, University of Maryland
In the past two decades, researchers have collaborated with government agencies, water quality groups, farmers, and wastewater treatment plant operators to promote conservation efforts and to identify the water quality trends in the Choptank basin.
As part of the current study, the researchers assessed whether the total maximum daily load (TMDL) for the Chesapeake—as determined by the U.S. Environmental Protection Agency to mitigate water quality degradation—and other management practices to inhibit atmospheric deposition, clean up point sources for pollution like wastewater treatment plants, and decrease runoff from agriculture have resulted in enhanced water quality in the Choptank estuary and streams.
Fisher and his colleagues assessed the advance toward water quality targets from 1998 to 2017. They discovered a decline in both wastewater treatment inputs and atmospheric deposition owing to these management actions, while there was an increase in overall inputs caused by higher agricultural inputs, despite conservation efforts.
Of the three monitoring stations located on the Choptank River, the one closer to a wastewater treatment plant outfall, which is a few miles downstream from Cambridge, Maryland, exhibited improvement.
This suggests that industrial and public investments in upgrades to wastewater treatment plants and reductions of atmospheric emissions have enhanced the quality of the estuarine water. Water clarity of the surface waters increased and there was a decline in the amount of algae. An increase in dissolved oxygen was observed in bottom waters.
An interesting question is why there is improving water quality at the monitoring station near the wastewater treatment plant despite an overall increase in nitrogen and pollution inputs to the estuary as a whole.
Tom Fisher, Professor Emeritus, Center for Environmental Science, University of Maryland
“This response suggests that local actions matter; in this case greatly reducing local inputs from the largest wastewater treatment plant in the area improved adjacent estuarine water quality, even when the overall estuary was receiving more nutrient pollution,” added Fisher.
The agricultural sector, which is the main source of phosphorus and nitrogen pollution, seemed to contribute very little to enhanced water quality during this period, although efforts were taken to promote best management practices, like drainage control structures, fertilizer management, or winter cover crops to minimize losses of phosphorus and nitrogen from fertilizers applied to fields.
The watershed includes several concentrated animal feeding operations, specifically poultry, which generate manure that is used as organic fertilizer for the crop fields. Fertilizers used for crops like wheat, corn, and soybeans might also reach the watershed through groundwater or surface runoff.
The watershed of the Choptank, which is a tributary of the Chesapeake Bay on the Delmarva Peninsula, lies mainly in the state of Maryland, with some part in Delaware. On the whole, the Choptank basin and the Chesapeake are quite similar, thereby facilitating the Choptank to be used as a model for progress in the Chesapeake.
“The eutrophication of the Choptank estuary is a microcosm of the Chesapeake Bay as a whole,” noted Fisher.
The Chesapeake Bay estuary has experienced major water quality degradation due to human influence as well as phosphorus and nitrogen pollutants from the air and land that have inhibited the use of the receiving waters for drinking and recreation, while leading to hypoxia and algal blooms.
Algal blooms can be found downstream in the Chesapeake and Choptank, and these block the sunlight and decrease the oxygen once the algae settle down at the bottom. This makes it challenging for fish and oysters to survive.
If reductions in agricultural nitrogen and phosphorus inputs over broad areas do occur in the future, improvements in estuarine water quality larger than those reported here, and more consistently throughout the entire estuary, could be expected. For this reason, it is important to continue monitoring agricultural areas with enhanced management practices.
Tom Fisher, Professor Emeritus, Center for Environmental Science, University of Maryland
Journal Reference:
Fisher, T. R., et al. (2021) Localized Water Quality Improvement in the Choptank Estuary, a Tributary of Chesapeake Bay. Estuaries and Coasts. doi.org/10.1007/s12237-020-00872-4.