United States Environmental Protection Agency - Great Lakes National Program Office image collection. The images were (quoting from the "about" page) developed as a Cooperative Agreement project with Minnesota Sea Grant. A collection originally called Visualizing the Great Lakes - Images of a Region was the starting point for the EPA GLNPO collection these images are sourced from.

(quoting from the "restrictions" page)
Restrictions for Using USEPA/GLNPO Images:

• The Great Lakes image collection is in the public domain and CANNOT be copyrighted.
• Although at present, no fee is charged for using the photos credit MUST be given to the United States Environmental Protection Agency Great Lakes National Program office.