Impact of non-indigenous planktonic copepod species on the estuaries of the Basque coast

Abstract

Since 1998, monitoring program on the environmental variables and zooplankton community are carrying out in the estuaries of Bilbao and Urdaibai (Bay of Biscay). In the year 2001 two non-indigenous copepod species (NIS), Acartia tonsa and Oithona davisae, were found in the inner estuary of Bilbao (Bay of Biscay), becoming immediately the dominant copepod species of the zooplankton community. Similarly, in the year 2003 these species occurred in the estuary of Urdaibai (near estuary of Bilbao), A. tonsa becoming very abundant in summer at the inner part of the estuary, but O. davisae occurring sporadically and in very few abundances. Later, in the year 2010 another NIS, Pseudodiaptomus marinus, occurred also in the estuary of Bilbao, together with other expanding copepod species (OES), Calanipeda aquaedulcis and Acartia bifilosa. The impact of this colonizer species has been little studied. Therefore, the aim of this thesis is to analyse the colonization process by NIS and OES of planktonic copepods, and the impact of such colonising species on native zooplankton communities, in estuaries of the Basque coast in relation to the natural and anthropogenic differences between estuaries, in order to assess the invasive character of the studied colonizing copepods and the sensitivity of the studied estuaries to biological invasions.