Tropical oomycetes in the German Bight – Climate warming or overlooked diversity?

Oomycetes have colonised both terrestrial and marine habitats, and leaf litter decomposing oomycetes have been found in coastal and estuarine environments, yet their ecological relevance remains unclear. In tropical and subtropical ecosystems, Halophytophthora species were reported from mangroves and salt marshes, and recently, the genus Salisapilia was described based on oomycetes recovered from leaf litter in subtropical Georgia, USA. In cool temperate regions, only Pythium and Phytophthora species have so far been reported from coastal environments. Here we report the presence of two species of Halophytophthora in the German Bight, north of Hamburg. The presence of a group of oomycetes, previously reported only from the subtropics and tropics, in the cool temperate German Bight raises the question of whether these were previously overlooked, introduced with ballast water or have migrated there as a result of climate change. Temperature preference of the strains hints at the first hypothesis.

► The tropical oomycete genus Halophytophthora is also present in the German Bight.
► Same species present in subtropical Georgia, USA and in the temperate German Bight.
► Local adaptation in strains from the North Sea, tolerating high temperatures less.