PORTLAND (AP) — The Maine Department of Marine Resources believes an unusually large bloom of phytoplankton is declining.

The department says the bloom isn’t a threat to human health, unlike other toxic blooms it typically monitors. But it can deplete oxygen, and large patches of dead softshell clams were reported around Maquoit Bay in Brunswick.

The department said Friday that reports from the public and staff indicate the bloom that stretches from Cape Elizabeth to Bath is dissipating.

The main concern is that the impact of depleted oxygen levels on fish and shellfish. But the department says the toxicity of the species is not fully understood, and says there could be some kind of fish-specific toxin.