Overview
Nutrients are essential for sustaining the marine ecosystem. However, when nutrients are present at excessive levels (“eutrophication”) due to human activities - they can be harmful to an estuary. When nutrients, especially nitrogen, are introduced to the estuary at higher than normal rates, they stimulate aquatic plant growth, including algae and “seaweed”. Under certain conditions, algal blooms can kill or harm fish and other aquatic animals by using up the dissolved oxygen in the water they need in order to breathe.
When sunlight is available, algae and plants release oxygen through photosynthesis, increasing the level of dissolved oxygen (DO) in the water. However, because algae use dissolved oxygen at night when photosynthesis does not occur (“water column respiration”), DO levels can become quite low by the early morning hours. Excess aquatic plant growth can also create problems as it settles to the bottom and is decomposed by bacteria. Not only do the bacteria use oxygen to break down the plant material (“sediment oxygen demand”), but they once again release the plants’ nitrogen back into the water column (“sediment nutrient flux”). If there is not enough dissolved oxygen in the water to sustain all of these processes, fish and other aquatic life will be forced to leave the area, become stressed or die. This condition of low dissolved oxygen is known as hypoxia. Click here to view an animated overview of how excess nutrients can lead to dissolved oxygen problems.
Although high levels of nutrients can lead to low dissolved oxygen conditions, other impacts from nutrients are also a concern. Excessive algae also cloud the water, effectively blocking sunlight from submerged aquatic vegetation (SAV). SAV, particularly eelgrass, provides prime nursery and spawning habitat for juvenile finfish and shellfish. The loss of SAV can affect the entire estuarine food web. The long-term impacts of high nutrient levels are difficult to measure, but probably include changes to the numbers and kinds of aquatic life present in the estuary.
Sources of nutrients in the Peconics
Sources of nitrogen include agricultural and residential fertilizers, on-site disposal systems (septic systems or cesspools), atmospheric deposition, in-place nutrient enriched bay bottom sediments, sewage treatment plants, and stormwater runoff. Most of the nutrients enter the bays from the atmosphere (rainfall) and groundwater, although sewage treatment plants are important in localized areas. Nitrogen loadings (inputs) to the entire estuary appear to be at an all-time high, with increases in loadings that come from the atmosphere and groundwater more than offsetting reductions that have occurred due to the closing of duck farms.
Status of nutrients in the Peconics
Fortunately, about 97 percent of the Peconic Estuary’s surface waters are classified as high quality when measured against New York State’s dissolved oxygen standards. These waters also meet the criteria for nitrogen set by the Long Island Sound Study and the Chesapeake Bay Program, which is based on the protection of eelgrass. However, due to poor tidal flushing and pollutant inputs, the environmentally sensitive western estuary is critically stressed (more specifically, the tidal Peconic River, Meetinghouse Creek and East Creek in Riverhead). These areas have elevated nitrogen levels and frequently do not meet dissolved oxygen standards. As a measurable goal, the PEP strives to reduce total nitrogen concentrations in the western estuary to meet the water quality standard established by the PEP.
PEP nitrogen management goals
- Reduce nutrient loads to the western estuary
- Preserve water quality in eastern estuary waters
- Develop and implement a total nitrogen load allocation strategy for the entire estuary
- Maintain or improve dissolved oxygen concentrations
- Optimize conditions for eelgrass
What the PEP is doing to reduce nitrogen loads
Reducing nitrogen loads is a priority for the Peconic Estuary Program. The PEP is pursuing several initiatives, including:
- Imposing limits on the amount of nitrogen that is discharged from the major sewage treatment plants and upgrading treatment systems to meet the limits.
- Supporting open space acquisition, particularly in nitrogen-stressed sub-watersheds (a benefit of natural lands protection is controlling nitrogen loads).
- Working with farmers to reduce the fertilizer (nitrogen) load from agriculture by 25%.
- Working with the 35 golf courses on the East End to reduce the amount of fertilizer (nitrogen) that leaches to groundwater and surface water.
- Developing more specific recommendations for homeowners and landscapers to reduce or eliminate fertilizer (nitrogen) losses to groundwater and runoff from lawn care and landscaping.
- Promoting the use of the treated wastewater from the Riverhead Sewage Treatment Plant to irrigate and “fertigate” the adjacent golf course.
- Working with the boating community to implement the “Vessel Waste No Discharge Zone” for the entire Peconic Estuary.
- Sponsoring shellfish and wetland restoration projects (both can help improve water quality).
- Supporting the construction of Crescent Duck Farm’s treatment plant to better treat processing waters.
- Working with governments to implement additional stormwater remediation projects on roadways.
- Investigating opportunities to reduce nutrient loadings from on-site wastewater disposal systems (“septic systems” or “cesspools”).
- Adopting the innovative policy of water quality preservation in the eastern estuary to accompany necessary mitigation projects.
