Meroplankton in Svalbard waters

Meroplankton in Svalbard waters

Top image: The life cycle of benthic invertebrates; egg release (left), meroplankton stage (top) and adult life (bottom). Illustration: Eike Stübner/UNIS.

Meroplankton are important in Arctic marine environment, but their dynamics and ecological role in marine coastal ecosystems are poorly understood. Eike Stübner has investigated these benthic invertebrate larvae and her research shed some light on the function of meroplankton in the Arctic. Stübner will defend her PhD thesis at UNIS on 14 December.

9 December 2016
Press release from the University Centre in Svalbard (UNIS) and UiT The Arctic University of Norway

Meroplankton are largely larvae of benthic invertebrates, which only live temporarily in the water column before settling onto the sea floor. The dynamics of how and when they are found in the water column throughout the year is poorly understood in Arctic environments. The main objective of Eike Stübner’s PhD thesis was to increase the knowledge about meroplankton dynamics and their ecological role in Arctic marine coastal ecosystems.

Stübner’s study was conducted in three fjords of Svalbard; Rijpfjorden on the north coast of Nordaustlandet; Billefjorden and Adventfjorden. She employed three different research approaches including frequent sampling in the field, molecular identification (DNA bar-coding, with shells, Bivalvia) and feeding trials (barnacles, Cirripedia nauplii).

Spring bloom start of “meroplankton outbreak”
One research question was how the different benthic groups use the water column for their larvae, which groups, time periods, level of concentrations and how this is controlled by biological and environmental factors.

Time line of meroplankton activity

Meroplankton “outbreak” (red line) is closely associated with the spring bloom in Arctic waters. Top image show on-set of the spring bloom and corresponding meroplankton activity (red line) in a fjord with ice cover in spring (such as Rijpfjorden and Billefjorden). Bottom image is from a fjord with no ice cover, such as Adventfjorden the past 10 years. The black line illustrates activity of copepods and other zooplankton species. Illustration: Eike Stübner/UNIS.

Furthermore, Stübner investigated how much these groups help grazing on phytoplankton when they occur in high densities. She found that meroplankton contributed significantly to the total amount of zooplankton during the productive time of the year. A strong correlation between the total number of meroplankton and amount of phytoplankton were observed. The timing of the spring bloom was the start of the “meroplankton outbreak” which mainly consisted of Cirripedia and Bivalvia larvae.

Strong seasonal variations were also observed in the prevalence of the different shell-larvae species that were found.

Grazing experiments gave limited results, but suggests that the barnacles-larvae alone cannot control the spring algal bloom. However, since the larvae of benthic invertebrates occur in extreme large quantities and that the predominant species eat and are eaten by many other species, it is highly likely that they still play a significant role in the pelagic ecosystems in the Arctic coastal areas and links together the pelagic and benthic systems.

Eike Stübner will defend her PhD thesis entitled, “Seasonality of Meroplankton in Svalbard Waters”, at UNIS on Wednesday 14 December 2016 at 13:15. She will give a trial lecture entitled “What are the forces that form seasonality in marine organisms?” at 10:15 the same day.

Both lectures will take place in the auditorium “Lassegrotta” at UNIS in Longyearbyen.

Supervisors have been Associate professor Janne Søreide (UNIS) and Professor Marit Reigstad (UiT The Arctic University of Norway). The committee consists of Professor Jan Marcin Weslawski, Institute of Oceanology, Poland (1. opponent), Dr. Silke Lischa, Helmholtz Centre for Ocean Research Kiel, Germany (2. opponent), and Professor Einar M. Nilssen, UiT The Arctic University of Norway (Leader of the committee).

Eike Ingrid Stübner

About the candidate:
Eike Stübner was born in Wiesbaden, Germany in 1981. She moved to Norway in 2004 and completed her MSc in marine biology in 2007 at the Norwegian University of Science and Technology and UNIS. After working as dog sledding guide and working for her own company, she started her PhD programme at UNIS and UiT The Arctic University of Norway in 2010.

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