Science Equipment

 Air Sampling Equipment

The air sampling equipment is located on the bow of the ship, constructed of aluminum booms with samplers attached at the end. The samplers are set up to point into the wind for several hours, so as to collect air upwind of exhaust stacks. This equipment is used to filter particles and gasses from the air, which are analyzed for atmospheric contaminants. Monitoring these samples enables scientists to determine the quantity of contaminants that enter the lake from the atmosphere.

Benthic Sled

The benthic sled was designed and constructed by several crewmembers of the Lake Guardian, and is used to collect samples from the lake floor. A large net with ski-like feet, the benthic sled is towed horizontally along the bottom of the lake. The surface of the lake floor is dredged into the net, collecting plant and animal communities and sediment stirred up by the sled. The net is returned to the back deck of the ship after the tow, where the sample is rinsed and benthic organisms are collected for further analysis.

 Box Corer

The box corer is a stainless steel box with one wall of clear plastic and jaws at the opening on the bottom to grab sediment. After reaching the lake bottom, weights are triggered to push the box into the lake floor and a sample of the sediment is harvested and lifted back to the ship. The various sediment layers can be viewed from the plastic window of the corer. The box corer keeps the surface of the sediment sample intact so that subsamples can be drawn from the core.

 Plankton Nets

Plankton nets are made of a fine mesh (ranging from 63-µm to 153-µm) that funnels into a collection cup, where organisms such as phytoplankton (algae) and zooplankton (small animals) are concentrated as lake water flows through the mesh during a tow. The net can be between 3 to 10 feet long, and the circular mouth of the net is typically within the range of 1 to 3 feet in diameter. The plankton net is lowered off the side of the ship, and the resulting sample is analyzed for parameters such as abundance, diversity, and pollutant concentration. The small organisms that are collected in the plankton net make up the base of the lake’s food web, and therefore provide researchers with vital information about the lake’s trophic status and availability of food for organisms higher up in the food web.

 PONAR Grab Sampler

The PONAR grab is a metal device that is deployed to the lake bottom and triggered to clamp shut when it reaches the lake floor. The jaws scoop up the benthic (bottom) sediments and organisms, which are returned to the ship’s deck and then processed by subsampling, rinsing and filtration so as to separate the sediments from organisms that are then collected for analysis. Due to its smaller size the PONAR grab does not penetrate as deeply into the lake bottom as the box corer, and therefore only collects sediments and organisms that are nearer to the lake floor’s surface.

 Rosette Sampler

This piece of equipment houses twelve plastic cylinders (called Niskin bottles) attached to a wire cage. As the Rosette descends in the lake, a marine technician remotely triggers each of the Niskin bottles in a predetermined sequence to obtain water from multiple desired sampling depths. The water collected in the bottles is analyzed back in the laboratory for properties that are not instantaneously detected from the Sea-Bird as well as to run quality assurance checks on the water quality characteristics measured by the Sea-Bird.


The Sea-Bird is a profiling instrument that contains multiple sensors. It is used to collect information for a variety of water properties primarily including conductivity, temperature, depth (which is why the Sea-Bird is sometimes called the CTD). The Sea-Bird can also measure pH, light penetration, water transparency, and chlorophyll a. The desired parameters are instantaneously measured and transmitted to the ship’s computer four times a second as the Sea-Bird descends towards the lake bottom, recording data at various depths throughout the water column. The data is used to generate a vertical profile of the water column at that station, showing how the water’s properties change from the surface to the bottom of the lake. Stratification layers of the lake can be determined from this information (i.e. epilimnion, thermocline, and hypolimnion), which informs scientists at which depths to trip the Rosette bottles for water sample collections.

The Triaxus is a towed undulating vehicle that was designed to collect multi-parameter limnological profile data.  The Triaxus vehicle informs the EPA-GLNPO's monitoring program using an array of sensors that monitor the near shore condition of the Great Lakes.  Towed behind the RV Lake Guardian, the Triaxus collects data on physical parameters such as water temperature, clarity, conductivity, dissolved oxygen and nitrogen concentrations as well as biological parameters, such as chlorophyll concentrations and zooplankton density.  These data provide GLNPO scientists with information about the coastal conditions of the Great Lakes.

The R/V Lake Guardian sails on behalf of the USEPA Great Lakes National Program Office, gathering environmental data to gauge the health of Great Lakes.

What's Happening?

The 2018 sampling season has begun! See the full schedule here »

Read about the Lake Guardian and Captain Mallard in the Illinois-Indiana Sea Grant newsroom »

Check out a social media recap of the 2016 Summer Survey »

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