Microbial response to oxygen depletion
Oxygen concentration is an important determinant of ecosystem health that alters factors such as habitat utilization (e.g. utility for recreational and commercial fisheries), the production of noxious odors, and the persistence of pathogens. Oxygen depletion is caused by nutrient enrichment of the environment and the associated Biological Oxygen Demand (BOD) primarily from microbial respiration. In recent decades, improvements in wastewater treatment have decreased nutrient inputs, resulting in elevated average seasonal oxygen concentrations and decreased duration of hypoxia- low oxygen- events throughout the HRE. Although improvements have been observed, episodic hypoxia events still occur and can result in large-scale habitat degradation. Changes in oxygen concentration are known to alter microbial abundance and metabolism that control nutrient cycling, greenhouse gas formation (e.g. CH4, N2O, CO2), protozoan grazing and the accumulation of toxic metabolic byproducts (e.g. H2S, NO2). Field and laboratory research is being conducted to understand the response of microbes (and the associated ecosystem attributes) during exposure to variable duration (how long) and intensity (how depleted) low oxygen events. This will provide a predictive understanding of the ecosystem benefits from management strategies that further increase oxygen concentration in HRE waters.
Pathogen inputs and persistence in the River
Real time monitoring of water quality and environmental conditions
The River is altered by rain fall, tidal conditions, anthropogenic inputs (e.g. urban and agricultural waste), and seasonal variability (e.g. light, temperature). These factors influence the rapidly changing (in time and space) environment that is experienced by human and wildlife populations. Average seasonal conditions are often inadequate to describe our interaction with River. For conditions such as pathogen abundance, oxygen concentration, or rain fall, the episodic, extreme events (occurring over minutes or hours) are often more important to our interaction with the river (e.g. sickness from swimming, fish kills from hypoxia, or flooding) than the seasonal mean condition. In addition, the factors controlling environmental health or disaster susceptibility are often determined by the combination of many environmental factors. In order to more effectively manage this resource for current and future conditions we need to have a more complete understanding of its spatial and temporal variability across scales (meters and minutes to kilometers and years). We have begun to deploy environmental sensors to monitor this variability from fixed moorings and shipboard transects of the environment. It is the goal of this research to enable a predictive understanding of the interaction between environmental variability and biological dynamics in the Hudson River Estuary. Furthermore, it is our goal to begin to understand the importance of brief extreme events (that are invisible to traditional discrete sampling) to the long-term health of the ecosystem and surrounding human populations.