Joanna Norkko
University of Helsinki, Tvärminne Zoological Station, Faculty Member
- Marine Biology, Marine Ecology, Marine biodiversity, Benthic macroinvertebrates, Benthic Ecology, Benthic Macroinvertebrates as Bioindicators of Water Quality, and 3 moreMarine Benthic Ecology, Determine the effects of sediment and physico-chemical parameters on benthic macro-invertebrates, and Benthic effects on fauna and sediment geochemistryedit
Research Interests: Environmental Science, Resilience, Hindsight bias, Forecasting, Population Dynamics, and 11 moreResearch, Medicine, Biological Sciences, Environmental Resource Management, Animals, Empirical Research, Psychological Resilience, Theoretical Models, Ecosystem, Time Factors, and Medical and Health Sciences
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Research Interests: Earth Sciences, Environmental Science, Oceanography, Ecology, Hypoxia, and 15 moreBiodiversity, Eutrophication, Biological Sciences, Environmental Sciences, Anoxia, Benthic macrofauna, Marine sediments, Chesapeake Bay, Ecosystem, Baltic Sea, Coastal Zone, Nutrient Fluxes, Ecosystem Functioning, Organic Matter, and Archipelago Sea
ABSTRACT To explore the dynamic nature of geochemical conditions in bioirrigated marine permeable sed-iments, we studied the hydraulic activity of three tellinacean bivalve molluscs (the Pacific species Macoma nasuta and Macomona liliana,... more
ABSTRACT To explore the dynamic nature of geochemical conditions in bioirrigated marine permeable sed-iments, we studied the hydraulic activity of three tellinacean bivalve molluscs (the Pacific species Macoma nasuta and Macomona liliana, and the northern Atlantic and Pacific species Macoma balth-ica). We combined porewater pressure sensing, time-lapse photography and oxygen imaging to quan-tify the durations and frequencies of tellinid irrigation activity and the associated oxygen dynamics in the sediment. Porewater pressure records of all tellinids were dominated by intermittent porewater pressurization, induced by periodic water injection into the sediment through their excurrent siphons, which resulted in intermittent oxygen supply to subsurface sediments. The irrigation (two–12 minutes long) and intervals between subsequent irrigation bouts (1.5–13 minutes) varied among tellinid species and individual sizes. For large M. liliana and M. nasuta, the average intervals between irrigation bouts were sufficiently long (10 minutes and four minutes, respectively) to allow complete oxygen consump-tion in between irrigation bouts in all tested sediment types. Irrigation patterns of smaller conspecifics and the smaller species M. balthica were characterized by significantly shorter separation of irrigation bouts, which resulted in more continuous oxygenation of the sediment. Transport-reaction modeling confirmed these species-and size-specific geochemical signatures and indicated that the geochemical character of the sediment is largely conditioned by the interplay between temporal irrigation pat-terns and sedimentary oxygen consumption rates. For large tellinids, model simulations indicated that oscillatory rather than stationary geochemical conditions are prevalent in a wide range of sediment types, with oxic pockets collapsing completely between periods of active irrigation. Based on the model results we developed analytical approximations that allow estimation of spatio-temporal char-acteristics of sediment oxygenation for a wide range of sediment types and infaunal activity patterns. Our results emphasize the need to consider the intermittent nature of bioirrigation when studying the geochemical impact of infauna in permeable sediments.
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Research Interests: Environmental Science, Oceanography, Ecology, Biodiversity, Biogeochemical processes, and 14 moreMarine, Habitat, Bioturbation, Ecology and Evolutionary Biology, Sediment, Sea, Ecosystem engineer, Ecosystem, Fresh, Organic carbon, Benthic Fauna, Context dependence, Sediment reworking, and habitat characteristics
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Research Interests: Environmental Science, Productivity, Ecology, Biodiversity, Microphytobenthos, and 15 morePhytoplankton, Medicine, Communities, Marine, Benthic Diatoms, Diatom, Nutrient, Ecosystem, Baltic Sea, Fresh water, Ecological Applications, Organic Matter, Marine ecosystem, phosphorus limitation, and multivariate analyses
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Research Interests: Environmental Science, Oceanography, Carbon, Benthic-pelagic coupling, Food web, and 15 moreEcology and Evolutionary Biology, Sediments, Continental shelf, Oxygen, Baltic Sea, Water Column, Organic Matter, Life Stage, Seasonal Patterns, Seafloor Spreading, Sedimentary organic matter, Beaufort Sea, spring bloom, Phytodetritus, and pelagic zone
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<p>Excess bioavailable nitrogen (N) is the key driver of coastal eutrophication, thus knowledge on the fate of N in coastal systems is imperative for improving eutrophication mitigation measures. In the coastal... more
<p>Excess bioavailable nitrogen (N) is the key driver of coastal eutrophication, thus knowledge on the fate of N in coastal systems is imperative for improving eutrophication mitigation measures. In the coastal Baltic Sea, benthic heterotrophic denitrification, the main process of bioavailable N-removal from a coastal system, has recently been suggested to be seasonally limited by labile organic carbon (OC) availability<sup>1</sup> - despite the system´s richness in labile organic matter from long-term eutrophication. This challenges our common understanding of the intrinsic link between C- and N-cycling, and highlights the need for a more advanced concept of OC availability. Hence, in this project, we (i) extensively characterized the biochemical composition of coastal OC beyond traditional descriptors of ‘lability’, applying techniques such as isotopic fingerprinting and Fourier transform ion cyclotron resonance mass spectrometry, and (ii) concurrently quantified benthic nitrate reduction rates both with and without addition of easily degradable OC (glucose), to ultimately confirm and understand proposed OC-limitation of denitrification in coastal sediments. All measurements were done in high temporal and spatial resolution at the southern coast of Finland, covering a three-month period from late winter to early summer that included the peak annual input of fresh organic matter to the benthic system by the phytoplankton spring bloom. First results will be presented and their implications for understanding seasonal N turnover and coastal eutrophication dynamics will be discussed.</p><p><sup>1</sup>Hellemann D, Tallberg P, Aalto SL, Bartoli M, Hietanen S (2020) Seasonal cycle of benthic denitrification and DNRA in the aphotic  coastal zone, northern Baltic Sea. Mar Ecol Prog Ser 637:15–28</p>
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Research Interests: Microbiology, Zoology, Medical Microbiology, Biology, Ecology, and 15 moreMedicine, Ticks, Babesia, Monitoring, Borrelia burgdorferi, Tick-Borne Pathogens, Ixodes ricinus, Longitudinal Study, Borrelia garinii, Borrelia afzelii, Bartonella, Ticks and Tick Borne Diseases, Borrelia, Anaplasma Phagocytophilum, and Tick
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Global marine heatwave assessments often rely on satellite-derived sea surface temperature. However, these data have low accuracy in coastal areas, are unable to measure sub-surface temperatures and have only been available since the... more
Global marine heatwave assessments often rely on satellite-derived sea surface temperature. However, these data have low accuracy in coastal areas, are unable to measure sub-surface temperatures and have only been available since the 1980s. Here, we analyse 90 years of in situ surface and bottom (30 m) water temperature data from a Finnish coastal monitoring site. Water temperatures were significantly higher between 1991–2020 than 1931–1960 and 1961–1990. We find strong differences between satellite-derived and in situ temperatures, with in situ temperatures being lower in autumn and winter and higher in spring. Measurements at the seafloor indicate marine heatwaves occurred during all seasons between 2016 and 2020, with intensities and durations exceeding previous records. Since the 1990s, we find an upward shift of the baseline temperature and increasingly frequent occurrence of temperatures previously considered as an extreme. Our findings highlight the importance of long-term in...
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Research Interests: Oceanography and Sea
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Research Interests: Oceanography and Sea
... profiles of pH, oxygen, sulfides, and other compounds can be measured with millimeter accuracy using microsensors penetrating the sediment (Glud 2008 ... bioturbation activities are preserved and can be seen in thick sediment layers... more
... profiles of pH, oxygen, sulfides, and other compounds can be measured with millimeter accuracy using microsensors penetrating the sediment (Glud 2008 ... bioturbation activities are preserved and can be seen in thick sediment layers that are thousands of years old (Erwin 2008 ...
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Research Interests: Oceanography and Marine
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