Doctoral defence: Kristiina Nõomaa “Role of invasive species in brackish benthic community structure and biomass changes”

On 16 February at 10:15 Kristiina Nõomaa will defend her doctoral thesis “Role of invasive species in brackish benthic community structure and biomass changes” for obtaining the degree of Doctor of Philosophy (in Hydrobiology).

Supervisor:
Professor Jonne Kotta, University of Tartu

Opponent:
Research Fellow Hanno Sandvik, Norwegian University of Science and Technology (Norway)

Summary
Alien species are arriving to the Baltic Sea at high rates. By 2022, already 220 alien species have been recorded in the Baltic Sea. Many of these species have established large populations and are affecting the Baltic Sea ecosystems. Since there are low numbers of native species in the benthic communities of the Baltic Sea, many vacant functional niches are ready to be inhabited by the novel species. Addition of a functionally novel species has the potential to severely effect the Baltic Sea ecosystem functioning and the services they provide. In this thesis large knowledge caps on how these species spread and act in their new environment were addressed. The species long-lasting impact was investigated with both manipulative experiments and long timeseries investigations. Experimental studies showed that the novel benthic predators, the round goby and the Harris mud crab, are able to consume high amounts of all dominant native invertebrates. Field studies showed that the strong impact of alien species observed in experimental communities are also happening in natural communities. The round goby has removed substantial amounts of benthic bivalves from the Estonian coastal sea, who are acting as a natural filter and buffering eutrophication effects. The Harris mud crab reduced benthic invertebrate biomass, even in an elevated nutrient future climate scenario. These impacts are also cascading to other trophic levels with observed increases in phytoplankton biomass. In addition, the alien species directly affect the ecosystem as novel prey objects. The round goby is already a dominant component in the diet of European perch. This thesis shows directly that alien species are playing an important role in the ecosystem and all decisions management and protection of the Baltic Sea ecosystem should consider the role of invasive species.

Defence can be also followed in Zoom: https://ut-ee.zoom.us/j/99315460726?pwd=ZWxWZzdQQktHakNkZ0dRR0VsaWhWdz09 (Meeting ID: 993 1546 0726, Passcode: 477665).