22nd May, 2013

It’s Phaeocystis time again

It’s Phaeocystis time again. Phaeocystis is a tiny 4-8 µm alga that forms colonies when conditions are right. The individual cells become encased in a carbohydrate gel matrix which can be a couple of millimetres in size, easily visible to the naked eye and contain 1000s of cells. These colonies can sometimes be clearly seen in coastal waters around the UK and can form blooms that are visible from space by remote sensing satellites.
This year, Phaeocystis started appearing at the sea surface at station L4 a few weeks ago and this week it has been found in large numbers (single cells and colonies) lower in the water column from 25 m to the seabed at about 50 m. What’s really interesting this year is that there may be two species of Phaeocystis in the Channel (see photos): Phaeocystis globosa and Phaeocystis pouchetii.
Phaeocystis globosa, is a temperate species and the species we’ve been seeing regularly off Plymouth for the past 8 years, whereasd Phaeocystis pouchetii, is considered to be more of a cold water, even arctic species, which may have made its way down through the North Sea during our cold winter. This ties in with the observation of cold water species of diatoms such as Chaetoceros teres (photo below) off Plymouth this year. (All photos, Claire Widdicombe, PML)

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