Thomas H. Johengen

Learn More
In 2011, Lake Erie experienced the largest harmful algal bloom in its recorded history, with a peak intensity over three times greater than any previously observed bloom. Here we show that long-term trends in agricultural practices are consistent with increasing phosphorus loading to the western basin of the lake, and that these trends, coupled with(More)
Hypoxic conditions, defined as dissolved oxygen (DO) concentrations below 2 mg/L, are a regular summertime occurrence in Lake Erie, but the spatial extent has been poorly understood due to sparse sampling. We use geostatistical kriging and conditional realizations to provide quantitative estimates of the extent of hypoxia in the central basin of Lake Erie(More)
TECHNOLOGY TYPE: Coupled conductivity and temperature sensors with instrument based algorithms for estimation of salinity APPLICATION: In situ estimates of salinity for coastal moored and profiled deployments NOTICE: ACT verifications are based on an evaluation of technology performance under specific, agreed-upon protocols, criteria, and quality assurance(More)
We propose the use of Bayesian hierarchical/multilevel ratio approach to estimate the annual riverine phosphorus loads in the Saginaw River, Michigan, from 1968 to 2008. The ratio estimator is known to be an unbiased, precise approach for differing flow-concentration relationships and sampling schemes. A Bayesian model can explicitly address the uncertainty(More)
The Alliance for Coastal Technologies (ACT) has been established to support innovation and to provide the information required to select the most appropriate tools for studying and monitoring coastal and ocean environments. ACT is a consortium of nationally prominent ocean science and technology institutions and experts who provide credible performance data(More)
Direct measurement of pCO 2 in natural water using gas equilibration and infrared detection of a gas stream APPLICATION: In-situ measurements of pCO 2 for coastal mooring. NOTICE: ACT Demonstration Projects are evaluations of technology performance under specific protocols, criteria, and quality assurance procedures that are established by mutual agreement(More)
Hydrogen peroxide (H 2 O 2) has been suggested to influence cyanobacterial community structure and toxicity. However, no study has investigated H 2 O 2 concentrations in freshwaters relative to cyanobacterial blooms when sources and sinks of H 2 O 2 may be highly variable. For example, photochemical production of H 2 O 2 from chromophoric dissolved organic(More)
APPLICATION: In-situ measurements of pCO 2 for coastal mooring. NOTICE: ACT Demonstration Projects are evaluations of technology performance under specific protocols, criteria, and quality assurance procedures that are established by mutual agreement of the ACT technical committee, technical staff and participating vendors. ACT and its Partner Institutions(More)
APPLICATION: In-situ measurements of pCO 2 for coastal mooring. NOTICE: ACT Demonstration Projects are evaluations of technology performance under specific protocols, criteria, and quality assurance procedures that are established by mutual agreement of the ACT technical committee, technical staff and participating vendors. ACT and its Partner Institutions(More)
Common ways to quantify watershed nutrient loads include estimating the annual or seasonal loads using simple relations between discharge and load, such as the ratio estimator, and fitting complex nutrient transport models to the observed concentrations. The former approach produces quite uncertain estimates even at low temporal resolution, when based on(More)
  • 1