Invasive species

Cosc _crop Coscinodiscus _wailesii3 Penilia Photo


The Pacific diatom Coscinodiscus wailessi is a phytoplankton species that was first recorded in the North Sea by the CPR survey in 1977.

It is thought that this large diatom arrived in the ballast water of container ships from the Pacific Ocean.  It is now a persistent and significant member of the spring plankton bloom community.  To date its presence has made little impact on the biodiversity of the plankton community.

Penilia avirostrisis a marine cladoceran which is usually found in the Mediterranean and Black sea and in sub tropical waters.  The rapid appearance of the species corresponded with exceptionally warm sea surface temperatures (SSTs). Since 1999, the species has become a regular feature of the autumnal zooplankton community of the North Sea.  It is suggested that increased autumn SSTs have provided suitable conditions in which P.avirostristo thrive, with warmer conditions contributing to the success of the species' resting eggs and aiding colonisation.