Gozo seems to have been invaded by blue blooms of jellyfish.

After a photograph of a bloom of the Velella Velella in Xlendi started doing the rounds some two weeks ago, reader Andrea Muscat today submitted the photo above of a bloom of the same jellyfish which appears to have taken over Dwejra. The photo was taken in the afternoon.

The living miniature sailing boat Velella Velella normally appears in Malta in spring, mostly between April and June.

This harmless species, often mistaken as a single jellyfish, is a floating colony, propelled by means of a 6cm-wide triangular flap, made of chitin, which acts as a veritable sail, beneath which are thousands of separate 3mm-individuals surrounding a large central mouth. The float contains a number of sealed air-filled compartments which ensure its buoyancy.

Dangling below the float are short tentacles which ensnare unwary plantkonic individuals but which do not impart a sting to humans. Velella Velella is a cosmopolitan species, being known from warm, temperate seas all over the world.

Two types of floats, which are mirror images of each other, exist within the same population such that the entire population is not propelled in the same direction but is dispersed in different ones.