Over the past 13 years, this calanoid copepod species, native to the Indo-Pacific area, has been spreading rapidly throughout the Mediterranean Sea, Black Sea, Atlantic coasts, and North Sea. In 2019, following a technical workshop, researchers from nine European countries established an ICES expert group, Towards a EURopean the OBservatory of the non-indigenous calanoid copepod Pseudodiaptomus marinUS - or WGEUROBUS. “Knowledge sharing and establishing collaborations among research groups provided the impetus for setting up this expert group", states Marcus Uttieri, co-chair of WGEUROBUS, “As a model organism, P. marinus is a perfect candidate not only to understand the mechanisms by which non-invasive species can expand, but also the potentialities of this species for pure and applied research".
The group wanted to study the biological and behavioural attributes of Pseudodiaptomus marinus that allowed it to spread so easily – with a vision to create a European network of those working on the various aspects of the biology and ecology of P. marinus, an open forum where experiences and know-how could be shared. A driving question for the open forum is whether “Pseudodiaptomus marinus should be considered a threat, or… seen as an opportunity for scientific and economic development?". After two years of research, the group has published a paper that sets the background and future direction of this important topic.
With no consensus on terminology within bioinvasion science, there is some controversy surrounding the use of the term “invasive". WGEUROBUS notes that, except for one known example, “the introduction of Pseudodiaptomus marinus has not been associated with any documented impact neither on the pelagic plankton communities nor on the health of the receiving basin". For this reason, they argue for the species to be referred to as “non-indigenous" as opposed to “invasive".
WGEUROBUS research shows that records have increased by more than 450% over the 2015–2019 period. Transoceanic shipping, and specifically ship ballast water, are named as the main form of introduction to European waters for P. marinus but the authors also mention aquaculture as a likely vector, with coastal circulation, intra-coastal ship traffic, and hull fouling acting as secondary spreaders.
Much of the group's research is on the spatio-temporal distribution of P. marinus and in their paper, they present an overview of where the species is found in European waters – primarily in coastal waters, followed by transitional systems such as estuaries and lagoons.
But how has the species established itself in extremely diverse environments? A wide salinity tolerance is one advantageous physiological trait that researchers have noted. A prominent behavioural trait is the ability to induce a torpid state while in low ambient temperatures – this may be “considered an overwintering strategy to endure harsh wintertime conditions, such as those experienced in the Black Sea".
Does the introduction of Pseudodiaptomus marinus alter the benthic community? Can it be considered a valid feed for local predators? This not yet known. While the impact on the receiving environments does not appear to be negative, the authors highlight that “the presumed non-invasiveness of this species … should not reduce the attention towards it". Utteiri adds that, “The impact of introduced species may manifest at different spatial and temporal scales, and this implies the necessity of continuous monitoring of impacted areas".
So how might this species provide a benefit? There is research being carried out into its potential use as a more sustainable and environmentally-friendly feed in aquaculture, as well as a copepod-derived nutraceutical for humans. Moreover, from an ecological perspective, some authors believe that the introduction of non-indigenous species may even be considered as positive, increasing biodiversity and supporting the conservation of the environment.
WGEUROBUS currently hosts primarily European researchers, but like Pseudodiaptomus marinus they are happy to broaden their geographical area to include researchers from around the Mediterranean to get a more robust description of P. marinus spreading. “We are keen to expand our geographic scope and welcome contributors that may have an interest in this topic".
Highlighting the importance of the novel-thinking that this expert group has provided, Silvana Birchenough, Chair of Ecosystem Processes and Dynamics Steering Group (EPDSG) has stated, “We are delighted that these scientific topics are rapidly incorporated into ICES arena, it is a great example of contemporary and cutting-edge science development to document the presence and distribution paths of this species".
Read the full paper, WGEUROBUS – Working Group “Towards a EURopean Observatory of the non-indigenous calanoid copepod Pseudodiaptomus marinUS", in Biological Invasions.
The work of WGEUROBUS addresses Ecosystem science and Emerging techniques and technologies, two of ICES scientific priorities. Discover all seven interrelated scientific priorities and how our network will address them in our Science Plan: “Marine ecosystem and sustainability science for the 2020s and beyond" .
Pseudodiaptomus marinus Sato, 1913. Photo: Iole Di Capua.