Scientist will test the quality of water at the beaches of the Great Lakes to determine if it is safe for humans to swim and play in. The scientist taking the sample wades out and collect water with a small vacuum made for this job. They have to take many samples at different depths. Shallow water closest to the shore will often yield different results than water samples that are collected at a deeper water level. The samples get sent to a lab where they are tested for pollution that could be harmful. If high levels of pollution is found, the beach is closed and more samples are taken until the testing shows that the beach is safe once again.
A water sample method used to measure the level of chlorophyll in the Great Lakes is the filtered vacuum. Water samples are taken at various depths by sucking the water and algae into a filtered vacuum. The filters are sent to the lab for testing.The collectors have to take several precautions so they do not change the amount of chlorophyll in the algae. They cannot allow bright light to reach the samples and they must store the samples in sub-freezing temperatures until they are ready to be tested at the lab.
Sometimes water samples are needed from very far below the surface of the Great Lakes. Scientists use a specialized remote operated vehicle, called an ROV. Scientist can stay onboard a boat and vacuum up samples from the lake bottom with the ROV. A technician controls where the remote operated vehicle goes. The vacuum sucks up water samples and the scientist collects them when they bring the ROV back onto the boat.
Sometimes water samples from the Great Lakes are taken with nets. This method is used to test for invasive species. Invasive species are plants and animals that have come from a different place and often will take over their new home, eating all the food. Scientist used the net method to take water samples when looking for the mysid shrimp. They use plankton nets at night to look for the small crustaceans. The nets were dropped into the water and hauled quickly back up to catch the invasive species.
Satellites are used to take photographs of the Great Lakes. Photographs are compared to previous year's photographs. This will show if the clarity or clearness of the water has changed and how sediment and shorelines have shifted. The clarity of water can tell the scientist if an algae bloom has occurred.