New Discovery of the Rare Freshwater Brown Alga Pleurocladia lacustris A. Braun (Ectocarpales, Phaeophyceae) in Ukraine (the Khadzhybey Estuary)

Abstract

A new locality of the freshwater brown alga <i>Pleurocladia lacustris</i> A. Braun, rare for Ukraine, was found. This species is classified as endangered in many European countries and is included in various protection lists. On the whole, about 50 habitats of <i>Pleurocladia lacustris</i> are known in the world, including Europe, North America, Australia, and Africa. For many decades, this is the second record of this alga in Ukraine, which was previously considered extinct here. It was found in the Khadzhybey estuary of the Black Sea in autumn 2023 at a depth of 0.5 m, water temperature 5.3 &deg;C, salinity 4.83 &#8240;, and pH 8.58. The alga occurred as an epiphyte on <i>Phragmites australis</i> (Cav.) Trin. ex Steud. and <i>Ruppia maritima </i>L. Its thallus was up to 5 mm long, slightly branched on one side, cells somewhat slimy, at the base impregnated with lime. The fouling formed a rather hard cover on the parts of flowering aqautic plants. In the fouling, <i>Pleurocladia lacustris</i> was accompanied by <i>Cladophora glomerata </i>(L.) K&#252;tz. and <i>Ulva flexuosa </i>Wulfen.