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Research findings: First Annual Onondaga Lake Scientific Forum
Consistent with the theme of the First Annual Onondaga Lake Scientific Forum, the independent research community presented a number of findings that are critical for effective management of this degraded resource. A selective listing of these findings is presented below.
Nitrogen
- violations of standards for ammonia and nitrite nitrogen, intended to protect against toxic effects, are violated annually in the upper waters of the lake as a result of the METRO discharge
- nitrification events occur in the lake during the fall mixing period of certain years; these events exacerbate the lake's oxygen problems
- upsets at the pharmaceutical pre-treatment facility represent challenges to the METRO discharge meeting in-lake standards for ammonia
- a probabilistic modeling framework has been developed that is appropriate to support TMDL analyses for ammonia
- the only management alternatives that are predicted to meet ammonia standards for the lake are "diversion" and an in-lake discharge with ammonia concentrations < 1 mgN·L-1 (year-round)
Phosphorus
- the lake's response to future reductions in phosphorus loading will not be retarded by sediment release of phosphorus, under existing stratification conditions
- efforts to oxygenate the lower layers of the lake will result in increased inputs of phosphorus to the upper waters of the lake
- phosphorus in METRO's discharge is more bioavailable than phosphorus from rural portions of the watershed
- METRO should be the primary focus of phosphorus-based rehabilitation efforts, and urban non-point should be considered secondary. Rural non-point is the least important source and is not an appropriate target for rehabilitation of the lake's eutrophication problem.
Mercury
- concentrations of mercury in smallmouth bass have not significantly changed over the last 25 years, and a substantial fraction of adults continues to have concentrations that exceed the standard
- changes in related policies by New York State on fishing in the lake; e.g., lifting the fishing ban in 1986 (changed to advisory on fish consumption), and lifting the advisory in 1999, appear to be unrelated to long-term data for mercury in fish
- the cycling of mercury in the lake and the extent of export to the river and Lake Ontario remain poorly understood; a reliable mechanistic model for mercury continues to be needed to guide related management actions
Oxygenation of the Hypolimnion
- the development of a near-field hydrodynamic model that is appropriate to evaluate the impact of an "oxygen bubble diffuser" (a method to oxygenate the hypolimnion recommended by US Army Corp) on the lake's stratification regime was documented
- model analyses demonstrated diffuser design would be critical to effectively oxygenate the lake's hypolimnion with this technology
- introduction of pure oxygen into the lake's hypolimnion in an appropriate manner (e.g., oxygen bubble diffuser) offers certain advantages over other technologies available to oxygenate hypolimnia; however, a more complete comparative analysis will be necessary before final selection of a technology is made
Fishery and Zebra Mussels
- on-going fish surveys have established high diversity in the lake, but reproduction is limited to a rather small subset of species
- densities of most fish (including desirable sport fish such as smallmouth bass) are unusually low, probably associated with the limited availability of rooted vegetation in potential nursery areas in the lake's near shore zone
- zebra mussels have invaded the lake, but populations remain relatively low, probably associated with limitations imposed by various features of industrial and domestic pollution
Organics
- the lake is enriched with a number of organic compounds as a result of industrial pollution
- substantial loadings of organics associated with residual inputs from closed facilities continue to enter the lake; e.g., chlorinated benzenes continue to enter along the west shore adjoining the old Allied signal plant
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