Science Plan

Field Observations

Field studies commenced in June 2003. Twelve sites along the Huron River have been sampled on a regular basis: once or twice weekly during summer, weekly during spring and fall, and biweekly during the winter. Lake sampling, including vertical profiles of temperature, oxygen, and water chemistry has been conducted at Barton Pond, Ford Lake, and Belleville Lake. In addition, automated recording instruments have been installed in these lakes to measure temperature, oxygen, pH, and total dissolved salts (as conductivity) around the clock.

Water chemistry measurements include:

• Specific Conductance, an index of total salt concentrations dissolved in the water
• Major Cations: Sodium, Potassium, Magnesium, Calcium
• pH: hydrogen ion activity; indicative of the general intensity of photosynthesis or respiration
• Forms of Phosphorus, the mineral nutrient that most directly controls the amount of algal biomass produced in the lakes

SRP: soluble reactive phosphorus, mainly orthophosphate; this form is highly available to algae

DP: dissolved phosphorus, including both inorganic and organic compounds

TP: total phosphorus, including both dissolved and particulate material;

• Forms of Nitrogen, another essential component of all organic matter

NH₄: ammonium

NO₃: nitrate

DN: dissolved nitrogen, including both inorganic (ammonium, nitrite, and nitrate) and organic compounds

PN: particulate nitrogen

TN: total nitrogen, including both dissolved and particulate matter; usually calculated as the sum of DN + PN

• SRSi: soluble reactive silica, a mineral required by specialized types of algae known as diatoms for constructing their cell walls
• Trace Metals, including both micronutrients and potential toxic elements:

Arsenic, Aluminum, Copper, Iron, Lead, Manganese, Molybdenum, Zinc

• Alkaline Phosphatase, an enzyme released by algae when they are stressed by low phosphorus, and hence an index of the degree of phosphorus limitation

The chemical measurements make it possible to examine the river by segments and to learn whether each segment is a source or sink for specific compounds. By measuring different forms of phosphorus and nitrogen it is possible to tell if the elements are being transformed from one chemical form into another.

Algal Pigments

Algal pigments are measured both by in situ fluorescence as well as laboratory extractions for chlorophylls and phycocyanin, a pigment specific for bluegreen algae.

Experiments

Field observations are complemented by experimental manipulations designed to reveal algal growth potentials and rates of various biological processes. Measured processes include rates of oxygen consumption, nitrate respiration, nitrogen fixation, and ammonium production.