Lower Neuse Riverkeeper NEWS ADVISORY OCTOBER 2009
In discussing the Menhaden fish kill in the Neuse and Trent Rivers that has been ongoing for nearly two months over a 40-square-mile area, state officials have suggested that the fish mortality is being caused by low oxygen levels induced by too many fish in one area. In response, the Neuse Riverkeeper has pointed out that other fish species as well as crabs located in the same exact areas were healthy and not deprived of oxygen. The Riverkeeper has also documented that during this entire period, wind conditions have varied greatly. Varying wind conditions, coupled with presence of healthy fish and crabs in the same area of the dying Menhaden, also casts doubt on the assertion that low oxygen is the only cause of the fish kill.
Considering the sparse available data, the state's Division of Water Quality lacks the scientific basis to determine the cause of the fish kill.In addition, many of the massive fish kill events over the past two months took place on weekends or after normal working hours. Members of the state sampling team were not on the water during those times. The continuing fish kill has, at times, been so massive that even during regular working hours, the state was and is without sufficient resources to adequately count the number of dead fish or collect the necessary data to establish the cause. Nevertheless, the state continues to suggest, simply, that the ongoing fish kill has been caused by low dissolved oxygen.
Even if the cause of the fish kill is, as suggested by the state, due to low levels of dissolved oxygen, nutrient pollution must be factored in as an underlying, significant contributing cause of the kill. Numerous peer-reviewed studies have established that nutrient levels in the Neuse Estuary have been and continue to be excessive. Such nutrient over-enrichment has been shown repeatedly to cause algal overgrowth and contribute to oxygen deficits and fish kills in estuaries like the Neuse. Some of these studies have examined trends in nutrient pollution levels over the past decade or more.In this regard, the most definitive study to date has been conducted by a group of distinguished scientists led by Dr. JoAnn Burkholder and renowned statistician Dr. David Dickey. It was peer-reviewed and published in 2006, and it documented a 500% increase in ammonium levels in the Neuse. Ammonium is a form of nitrogen that strongly stimulates algal growth. Other data collected by the state-certified laboratory at NC State University's Center for Applied Aquatic Ecology have shown that there also has been a substantial increase in algal biomass as chlorophyll a in the Neuse Estuary. This is another clear indicator that nutrient pollution is increasing substantially in the estuary, stimulating algal overgrowth, and contributing to the oxygen deficits that have been linked to the major fish kills.
For further information about the role of nutrient pollution in causing oxygen deficits and fish kills, the Neuse River Foundation suggests contacting the NC State University Center for Applied Aquatic Ecology by phone (919 515-3421) or email (http://www.ncsu.edu/wq/).