September 10, 2026 — An algae bloom in Casco Bay could be harming fish and shellfish.
The Maine Department of Marine Resources is monitoring the bloom of a common phytoplankton called Karenia mikimotoi. The phytoplankton are not harmful to humans, but they can produce compounds that can harm fish and shellfish.
The department was alerted to the bloom when the Portland Harbor Master and wharf owners in Portland Harbor noticed a dark brown tint to the water, according to a social media post by the Maine DMR .