Maine officials monitoring algae bloom in Casco Bay that can harm marine life

PORTLAND PRESS HERALD • September 8, 2026

The Maine Department of Marine Resources is monitoring an algae bloom in Casco Bay. While the phytoplankton Karenia mikimotoi detected in the bay this week is not harmful to humans, it can be for marine life. The bloom has been observed from Portland Harbor to Middle Bay, and the department says its staff and members of the public have reported brown discoloration and “an accompanying smell.” “Karenia mikimotoi can produce compounds that can potentially impact fish and shellfish, and there have been fish kills and benthic mortality events reported during blooms of this species,” the Department of Marine Resources stated.