The First Record of <i>Acanthocyclops trajani</i> (Copepoda, Cyclopidae) in the Vistula Lagoon of the Baltic Sea

Abstract

In 2021 Acanthocyclops trajani Mirabdullayev et Defaye, 2002, was first record in the Vistula Lagoon of the Baltic Sea. This species quickly spread throughout the water area of the Lagoon. In summer, A. trajani reached its maximum development (up to 92 thousand ind./m3, 2.4 g/m3), was a dominant and forming a particularly high proportion of zooplankton in the most polluted, desalinated and eutrophicated eastern part of the Vistula Lagoon. As a result of predatory feeding, A. trajani exerted significant pressure on the planktonic communities of the Lagoon; its diet in August exceeded the production of non-predatory zooplankton. The pressure on zooplankton increased even more due to the mass development of Cercopagis pengoi (Ostroumov, 1891), with which the new species entered into competitive relationships. The main reasons for the successful naturalization of A. trajani in the Vistula Lagoon, apparently, include some features of its biology, the structure of the plankton community with the presence of unoccupied trophic niches, the continued eutrophication this waterbody, decreasing the pressure of the invasive mollusk Rangia cuneata (G.B. Sowerby, 1831), as well as local climate warming, noted in recent decades.