The PhD defence and trial lecture will be held in Auditorium 1 in The Geology Building. In some cases, it will be possible to attend the trial lecture and dissertation digitally, in that case a link to Zoom will be posted.
Trial lecture
Thursday 22 January, 11:15-12:00, Aud 1, The Geology Building:
The role of microorganisms in the Arctic marine carbon cycle
Conferral summary
Arctic seafloor communities are vulnerable to ocean warming and sea-ice retreat. In her study, Thaise Ricardo de Freitas investigated how benthic foraminifera—microscopic, single-celled organisms—respond to environmental shifts in the northern Barents Sea. The study shows that foraminiferal communities are primarily shaped by bathymetric and hydrographic gradients and exhibit seasonal dynamics not reflected in the sedimentary record. Experimental findings demonstrate that foraminifers are active consumers of organic matter but exhibit species-specific responses to food pulses. The observed complex relationship between productivity and biodiversity in polar regions suggests that future climate-driven increases in productivity can restructure the Arctic seafloor ecosystem.
Main research findings
Popular scientific article about de Freitas’s dissertation:
Benthic foraminifera in the warming Arctic: Seasonal dynamics, biodiversity, and response to phytodetrital pulses
Rising temperatures and melting sea ice are likely to affect the primary production and its fate in the Arctic Ocean seabed. Since seafloor communities rely on organic material that reaches the seafloor, these climate-driven changes will affect sedimentary organic carbon, food-web structure, and biodiversity in the area. Benthic foraminifera are valuable indicators of environmental change, playing a significant role in energy transfer and fast carbon consumption.
In her doctoral research, Thaise Ricardo de Freitas integrated biogeochemical and ecological studies to quantify the contribution of benthic foraminifera to carbon processing and to examine how environmental factors and seasonal fluctuations in food supply influence their diversity and distribution in the northern Barents Sea.
Arctic benthic foraminifera actively feed on phytodetritus, but differences between scavengers and suspension feeders are relevant. Warming alone didn’t impact overall feeding. Nevertheless, scavenger species adapted to high temperature variation and a steady food supply could be favoured under climate change.
The study shows that along the northern Barents Sea margin, the diversity and composition of benthic foraminifera are primarily shaped by water depth, water masses properties, and food availability. Foraminiferal populations exhibit seasonal fluctuations that are not seen in macrofaunal organisms or the sedimentary record. The lack of seasonal or long-term variation in the latter indicates prolonged water residence time and rapid degradation of organic carbon. The complex productivity-diversity relationship observed in the study suggests a mismatch between the timing of resource production in the water column and its utilisation at the seabed. Future climate warming may modify the benthic carbon cycle through species-specific shifts that restructure biodiversity and trophic adaptations.
Video description: Box Corer operation during Arven etter Nansen May 2021 field campaign. This equipment was used to collect sediment samples to study organisms living in the sediment (e.g, foraminifera) and to analyse sediment properties (e.g., grain size, organic carbon). In the video, it is also possible to observe particles (i.e., marine snow) and small animals in the water, and large organisms living on the sediment (e.g., brittle stars). Video recorded with Blueye ROV. Credits: Tore Mo-Bjørkelund and Martin Ludvigsen.
Photo and other information:
Press photo: Thaise Ricardo de Freitas, portrait; 800px. Photo: Private
