The main organisms causing red tides (water coloration) in the Galician estuaries are:

Species: Mesodinium sp.

Color: Reddish

Non Toxic

Responsible for the most characteristic red tides in Galicia, the color of the water has a bloody appearance.

Species: Noctiluca scintillans

Color: Orange

Non Toxic (although it may accumulate toxins through its prey).

Often they are dragged towards the shore, where they form oily-looking spots in late summer. They are not toxic but can cause a certain burning sensation in the skin.

Species: Lingulodinium polyedrum

Color: Reddish

Slightly toxic (Yesotoxins).

Causing the first red tide described in the Galician Estuaries by Odón de Buen in 1916, although the naturalist Ramón Sobrino correctly identified the responsible organism in 1918.

Species: Gymnodinium catenatum

Color: Reddish brown

Highly toxic (PSP: paralyzing toxins).

It is responsible for the toxic proliferation of 1976 in the Rías Baixas that led to the implementation of a program to monitor toxic algae in Galicia.

Species: Alexandrium spp.

Color: Reddish brown

Toxic (PSP: paralyzing toxins).

Its proliferations are more abundant in the Rías Altas (eg Ares-Betanzos), where a case of coloration at sea was cited in 1984.

Species: Kryptoperidinium foliaceum

Color: Reddish brown

Non toxic

Frequent in estuarine areas. Red tides of this species have been observed in the inlet of Ramallosa (Baiona) and in the Ulla river.