The recent closure of the harbor to shellfishing is due to a bacteria known as Vibrio parahaemolyticus, a naturally-occurring marine bacterium generally associated with warm water conditions. Vibrio parahaemolyticus is not associated with sewage or stormwater contamination of harvest areas. Vibrio is common in southern waters, where the water temperatures are warmer. The unusually warm spring, and intense heat this summer, are contributing factors to why it is occurring here this year. The closure notice from the DEC is posted on Friends of the Bay’s website at http://friendsofthebay.org/?p=1112
Friends of the Bay’s water quality monitoring data is now being posted online, (http://friendsofthebay.org/?page_id=1151) so that the results of the monitoring conducted by our volunteers will be available to the public as soon as possible after our water quality monitoring is performed on Monday. Each week, from the first Monday through the last Monday in October, 19 sites locate throughout the estuary are monitored by Friends of the Bay. Friends of the Bay’s 2010 Annual Water Quality Monitoring Report has been completed and is available on our website at http://friendsofthebay.org/?page_id=119.
Ambient readings, such as temperature, salinity, ph, and Dissolved Oxygen are conducted at three levels throughout the water column, one half a meter from the bottom, one meter from the surface, and at one half a meter at the surface (when the depth allows). Dissolved Oxygen is an important indicator of the overall health of the estuary, since all marine creatures need oxygen. Readings of 5.0 mg/Liter of dissolved oxygen are considered to be healthy. Hypoxia means “low oxygen.” In aquatic ecosystems, low oxygen usually means a concentration of less than 2-3 milligrams of oxygen per liter of water (mg/l). A complete lack of oxygen (0 mg/L) is called anoxia.
Factors which influence hypoxia include:
- Temperature: Cooler water holds more oxygen, so the warm summer waters can be particularly stressful for marine organisms.
- Saline water: The higher the salt concentration, the lower DO capacity of water
- Excessive nutrients (Nitrogen and Phosphorus): Excess nutrients can cause an algal bloom, which blocks sunlight from aquatic vegetation lower in the water column. When an excessive amount of algae dies it sinks to the bottom, and is decomposed by bacteria. The bacteria consume large amounts of oxygen reducing the amount available for fish and other living organisms in bottom waters.
- Poor water clarity: Algal blooms can reduce the amount of sunlight reaching plants attempting to grow lower in the water column. Poor water clarity can also indicate the presence of suspended sediments, eroded soil, and/or microscopic organisms. This can limit photosynthesis, inhibit the breathing of fish by clogging the grills, and adversely affect filter-feeding organisms (i.e. clams, oysters, mussels).
During the heat of summer, it is not unusual to see readings in the 2 – 3 mg/L range, especially in the shallower areas of the harbor, like Cold Spring Harbor South, or in Mill Neck Creek. This is a pattern which has been observed over the course of years, with the lowest readings being recorded in late July and August, and then as the water cools off, the readings rebound in September and October.
Coliform bacteria levels are used as an indicator of possible presence of human pathogens within the aquatic environment. Coliform are generally not harmful themselves. They indicate the possible presence of pathogenic (disease-causing) bacteria, viruses, and protozoans that also live in human and animal digestive systems. High levels of coliform bacteria can cause the closure of shellfish beds and beaches due to human health concerns. Causes of high coliform bacteria levels: include failing septic systems, storm water runoff and animal waste.
Coliform samples are collected and analyzed every week during Friends of the Bay’s monitoring season. Nitrogen samples are collected and analyzed once a month. The ecosystem of the estuary is complicated, and as with so much else in nature and science, the more that is learned, the more it is recognized that further study is necessary in order to more fully understand it.
Update on the Bald Eagles
There is mixed news on the juvenile bald eagles which were rescued and transported to the Raptor Trust. The bird found by Mitch Kramer in the middle of the sound and which was transported on July 4, has a case of Avian Pox (this is NOT transmittable to humans.) Avian Pox causes wart like lesions, which usually occur on the unfeathered parts of the bird’s body. Unfortunately, in this bird’s case is also affected his mouth, nose and soft palate. He is on antibiotics, and is in guarded condition. He will be remaining at The Raptor Trust for treatment for some time. The second bird is faring much better, is “eating like a champ” and will probably be able to be released relatively soon, at a location to be determined by the Department of Environmental Conservation.