The non-indigenous Oithona davisae in a Mediterranean transitional environment: coexistence patterns with competing species

Abstract

The Venice lagoon (VL) has been recognized as a hot spot of introduction of non-indigenous species (NIS), due to several anthropogenic factors and environmental stressors that combined may facilitate NIS invasions. In the last decades an increasing number of zooplankton NIS have been observed in the VL. This work aims to provide a picture of the annual cycle and distribution of the recently recorded non-indigenous copepod Oithona davisae, considering the coexistence patterns with the congeneric resident Oithona nana. Therefore, zooplankton samplings were carried out monthly from August 2016 to July 2017 at five Long-Term Ecological Research LTER stations in the VL. Oithona davisae showed a persistent occurrence throughout the year with the highest abundances in the warm season and in the inner areas, while the congeneric O. nana, showing a different distribution pattern, resulted more abundant near the inlets of the Lagoon, where O. davisae reached the minimum density. Oithona davisae seems to find local conditions that promote its settlement and distribution, especially in the inner and more trophic lagoon sites. In other European coastal embayments or transitional waters, O. davisae occupied the niche left by the indigenous O. nana or can replace this congeneric species through competitive exclusion mechanisms. Our data indicate that, for now, such species replacement has not occurred in the VL. One of the causes is the extreme variety of habitats and niches offered by this environment allowing a balanced coexistence with O. nana and in general with the resident copepod community.

Spatio-temporal variation of the invasive copepod Oithona davisae in the zooplankton community of Kavala harbour

“…Therefore, in many cases there is no clear picture of their distribution patterns or the time of O. davisae invasion in the newly established areas. In the Mediterranean Sea, it has so far been reported in the coastal lakes Faro & Ganzirri in Italy (Zagami et al, 2018), Venice Lagoon (Vidjak et al, 2019;Pansera et al, 2021), Barcelona port in Spain (Saiz et al, 2003), Thermaikos Bay in Greece (Dragicevic et al, 2019), the Turkish coasts of the Aegean Sea (Terbıyık Kurt & Beşiktepe, 2019) and the Levan-tine Sea (Terbıyık Kurt et al, 2022). Besides recording its presence, few of these studies investigated its seasonal and spatial variations.…”

“…5). Oithona davisae seems to find local conditions that promote its settlement and distribution, especially in the inner and more trophic sites (Pansera et al, 2021). Future monitoring of the evolution of the non-indigenous O. davisae population will allow investigation of potential consequences of its introduction, such as exclusion of congeneric species and competition with other copepods for limited resources and microhabitats.…”

Natural or anthropogenic variability? A long-term pattern of the zooplankton communities in an ever-changing transitional ecosystem

“…The zooplankton in the Venice Lagoon is mostly (80%) composed by Copepoda (with Acartia as the most abundant genus) and approximately 10% Chordata (Appendicularia, Ascidiacea larvae, and Actinopterygii larvae or eggs), followed by Echinodermata and Mollusca larvae (Camatti et al, 2006;Schroeder et al, 2020); in the hot season and in areas close to the inlets, the presence of Cladocera is relevant (Pansera et al, 2021). The community shows in general a clear seasonality in the populations' composition and taxonomic diversity, indicating that water temperature is the most prominent environmental factor shaping the zooplankton assemblages.…”

“…In addition, although the Venice Lagoon has been extensively studied both from the climatological point of view (Makris et al, 2023;Sambo et al, 2023) and from that of the impacts on ecosystems and resident biological communities (Solidoro et al, 2010;Picone et al, 2023;Milan et al, 2023;Zennaro et al, 2023), very few studies on zooplankton communities have been performed (Camatti et al, 2019;Pansera et al, 2021).…”

Transboundary Transitional Waters: Arenas for Cross-Border Cooperation or Confrontation?

“…Pitacco et al [36] summarized the variation patterns of macrobenthic invertebrates in 18 Italian TW. Considering the threats posed to the native biodiversity of TW by alien species, the primary concerns for researchers and TW managers are the invasions and proliferation of alien invertebrates [37][38][39], fish [40,41], and aquatic macrophytes [42][43][44]. These concerns are closely related to research on the economy and sustainable development in TW areas [45][46][47][48][49].…”