Dataset: CO2

This dataset provides CO2 data collected during 2017, 2018, 2019, and 2021 from a Lake Michigan transect between Milwaukee, Wisconsin and Muskegon, Michigan. Water chemistry and conductivity-temperature-depth (CTD) profiles were measured at several stations in Lake Michigan, ranging in depth from 10 to 55 m, in a region northeast of Milwaukee Harbor. Measurements included soluble reactive phosphorus, total dissolved phosphorus, particulate phosphorus, chlorophyll a, the concentrations and stable isotope ratios of particulate carbon and particulate nitrogen, dissolved carbon dioxide, dissolved total inorganic carbon, and dissolved organic carbon. In addition, continuous lake surface and atmospheric CO2 data were collected in 2019 and 2021 on a Lake Michigan transect between Milwaukee, WI and Muskegon MI. The water chemistry and CTD data are provided in separate datasets. Measurements were made with a CO2 monitoring system mounted on a high-speed ferry that crosses the lake 4 to 6 times daily between May and October. The monitoring system consists of a "wet" box which includes a peristaltic pump that draws water from the ship's sea chest and an equilibrator in which dissolved gases are equilibrated with a recirculating air flow. The air is pumped through a desiccant to remove moisture, after which it flows to a "dry" box where it passes through an infrared gas analyzer. A similar system, without the peristaltic pump or equilibrator, is mounted near the bow of the ship to record atmospheric CO2 concentration. These chemical measurements have several applications, including: 1) Constructing an annual carbon and nutrient budget for the water column, which is used along with direct measurements of quagga mussel nutrient recycling to assess the role of invasive quagga mussels in the lake's carbon and nutrient cycles; 2) When combined with separate measurements of the vertical structure of water density and currents, to quantify vertical fluxes of dissolved nutrients and inorganic carbon, to determine how carbon and nutrient recycling by profundal quagga mussels may affect plankton production in the euphotic zone; 3) The calibration and validation of physical / biogeochemical models used to better understand how invasive quagga mussel have altered energy flow and nutrient dynamics in the Great Lakes, and guide management decisions with regard to nutrients and fish stocking.