scholarly journals Biogenic silica production and diatom dynamics in the Svalbard region during spring

2018 ◽  
Vol 15 (21) ◽  
pp. 6503-6517 ◽  
Author(s):  
Jeffrey W. Krause ◽  
Carlos M. Duarte ◽  
Israel A. Marquez ◽  
Philipp Assmy ◽  
Mar Fernández-Méndez ◽  
...  
Keyword(s):  
Primary Production ◽  
Silicic Acid ◽  
Biogenic Silica ◽  
Spring Bloom ◽  
Critical Role ◽  
The Arctic ◽  
Acid Uptake ◽  
Regional Food ◽  
Carbon Cycles ◽  
European Arctic

Abstract. Diatoms are generally the dominant contributors to the Arctic Ocean spring bloom, which is a key event in regional food webs in terms of capacity for secondary production and organic matter export. Dissolved silicic acid is an obligate nutrient for diatoms and has been declining in the European Arctic since the early 1990s. The lack of regional silicon cycling information precludes understanding the consequences of such changes for diatom productivity during the Arctic spring bloom. This study communicates the results from a cruise in the European Arctic around Svalbard, which reports the first concurrent data on biogenic silica production and export, export of diatom cells, the degree of kinetic limitation by ambient silicic acid, and diatom contribution to primary production. Regional biogenic silica production rates were significantly lower than those achievable in the Southern Ocean and silicic acid concentration limited the biogenic silica production rate in 95 % of samples. Compared to diatoms in the Atlantic subtropical gyre, regional diatoms are less adapted for silicic acid uptake at low concentration, and at some stations during the present study, silicon kinetic limitation may have been intense enough to limit diatom growth. Thus, silicic acid can play a critical role in diatom spring bloom dynamics. The diatom contribution to primary production was variable, ranging from <10 % to ∼100 % depending on the bloom stage and phytoplankton composition. While there was agreement with previous studies regarding the export rate of diatom cells, we observed significantly elevated biogenic silica export. Such a discrepancy can be resolved if a higher fraction of the diatom material exported during our study was modified by zooplankton grazers. This study provides the most direct evidence to date suggesting the important coupling of the silicon and carbon cycles during the spring bloom in the European Arctic.

scholarly journals Biogenic silica production and diatom dynamics in the Svalbard region during spring

2018 ◽  
Author(s):  
Jeffrey W. Krause ◽  
Carlos M. Duarte ◽  
Israel A. Marquez ◽  
Philipp Assmy ◽  
Mar Fernández-Méndez ◽  
...  
Keyword(s):  
Primary Production ◽  
Silicic Acid ◽  
Biogenic Silica ◽  
Spring Bloom ◽  
Critical Role ◽  
The Arctic ◽  
Acid Uptake ◽  
Regional Food ◽  
European Arctic ◽  
Diatom Productivity

Abstract. Diatoms are generally the dominant contributors to the Arctic Ocean spring bloom, which is a key event in regional food webs in terms of capacity for secondary production and organic matter export. Dissolved silicic acid is an obligate nutrient for diatoms and has been declining in the European Arctic. The lack of regional silicon cycling information precludes understanding the consequences of such changes for diatom productivity during the Arctic spring bloom. This study communicates the results from a cruise in the European Arctic around Svalbard reporting the first concurrent data on biogenic silica production and export, diatom cellular export, the degree of kinetic limitation by ambient silicic acid, and diatom contribution to primary production. Regional biogenic silica production rates were significantly lower than those achievable in the Southern Ocean and silicic acid concentration limited the biogenic silica production rate in 95 % of samples. Compared to diatoms in the Atlantic subtropical gyre, regional diatoms are less adapted for silicic acid uptake at low substrate, and at some stations during the present study, silicon limitation may have been intense enough to limit diatom growth. Thus, silicic acid can play a critical role in diatom spring bloom dynamics. Diatom contribution to primary production was variable, ranging from

Overview of nutrient cycling in the sub-Arctic Atlantic regions: insights from nitrate & silicon isotopes

2021 ◽  
Author(s):  
Margot Debyser ◽  
Robyn Tuerena ◽  
Raja Ganeshram ◽  
Laetitia Pichevin
Keyword(s):  
Stable Isotopes ◽  
Nutrient Cycling ◽  
Primary Production ◽  
Silicic Acid ◽  
North Atlantic ◽  
Nutrient Budget ◽  
The Arctic ◽  
Silicon Isotopes ◽  
The North ◽  
The North Atlantic

&lt;p&gt;The environmental consequences of rapid climate change are already becoming apparent in the Arctic. Polar amplification has led to major loss of sea ice, increasing freshwater run-off and a poleward intrusion of Atlantic waters, thereby affecting biogeochemical cycles. Additionally, while primary production in the Arctic has increased by &gt;50% over the last two decades (Lewis et al., 2020), it is still unclear whether Arctic nutrient budgets can sustain this increase on the long-term. Increased primary production in the central Arctic has the potential to reduce nutrient concentrations of Arctic outflow waters and modify their nutrient ratios, having consequences for the Atlantic nutrient budget.&lt;/p&gt;&lt;p&gt;Primary production in the Arctic is principally nitrogen-limited as a result of benthic denitrification on Arctic shelves. This is contrasted by silicon limitation in water masses originating from the Atlantic basin. To untangle the complexities of dual nutrient limitation and to gain insights into the role of Arctic outflows in controlling nutrient export to the North Atlantic, we examine the cycling of both major nutrients, nitrate and silicic acid, in key Arctic seas and straits. Using stable isotopes of dissolved nitrate and silicic acid, we provide new insights into the &amp;#160;mechanisms and factors that control nutrient cycling in the Arctic Ocean: nutrient origins, transformation during transport, as well as the relative contribution of primary production, remineralisation and regeneration to water column inventories.&lt;/p&gt;&lt;p&gt;In this study, measurements of nutrient stoichiometry and stable isotopes of dissolved nitrate and silicic acid profiles are presented across the Fram Strait, Labrador Sea (AR7W transect), and the Iceland Basin and Irminger Sea (the Extended Ellett line and the OSNAP-East program). The measured variability in nutrient isotope signatures across the Arctic gateways brings to light the contribution of Arctic-sourced freshwater to the North Atlantic and its potential impact to the North Atlantic nutrient budget with future changes to primary production in these key regions.&lt;/p&gt;

scholarly journals Modeling silicate–nitrate–ammonium co-limitation of algal growth and the importance of bacterial remineralization based on an experimental Arctic coastal spring bloom culture study

2021 ◽  
Vol 18 (5) ◽  
pp. 1719-1747
Author(s):  
Tobias R. Vonnahme ◽  
Martial Leroy ◽  
Silke Thoms ◽  
Dick van Oevelen ◽  
H. Rodger Harvey ◽  
...  
Keyword(s):  
Primary Production ◽  
Nitrogen Limitation ◽  
Spring Bloom ◽  
Algal Growth ◽  
Chlorophyll Synthesis ◽  
Model Complexity ◽  
The Arctic ◽  
Nutrient Regeneration ◽  
Nutrient Inputs ◽  
Ecosystem Models

Abstract. Arctic coastal ecosystems are rapidly changing due to climate warming. This makes modeling their productivity crucially important to better understand future changes. System primary production in these systems is highest during the pronounced spring bloom, typically dominated by diatoms. Eventually the spring blooms terminate due to silicon or nitrogen limitation. Bacteria can play an important role for extending bloom duration and total CO2 fixation through ammonium regeneration. Current ecosystem models often simplify the effects of nutrient co-limitations on algal physiology and cellular ratios and simplify nutrient regeneration. These simplifications may lead to underestimations of primary production. Detailed biochemistry- and cell-based models can represent these dynamics but are difficult to tune in the environment. We performed a cultivation experiment that showed typical spring bloom dynamics, such as extended algal growth via bacterial ammonium remineralization, reduced algal growth and inhibited chlorophyll synthesis under silicate limitation, and gradually reduced nitrogen assimilation and chlorophyll synthesis under nitrogen limitation. We developed a simplified dynamic model to represent these processes. Overall, model complexity in terms of the number of parameters is comparable to the phytoplankton growth and nutrient biogeochemistry formulations in common ecosystem models used in the Arctic while improving the representation of nutrient-co-limitation-related processes. Such model enhancements that now incorporate increased nutrient inputs and higher mineralization rates in a warmer climate will improve future predictions in this vulnerable system.

scholarly journals Modelling Silicate – Nitrate - Ammonium co-limitation of algal growth and the importance of bacterial remineralisation based on an experimental Arctic coastal spring bloom culture study

2020 ◽  
Author(s):  
Tobias R. Vonnahme ◽  
Martial Leroy ◽  
Silke Thoms ◽  
Dick van Oevelen ◽  
H. Rodger Harvey ◽  
...  
Keyword(s):  
Primary Production ◽  
Nitrogen Limitation ◽  
Spring Bloom ◽  
Algal Growth ◽  
Chlorophyll Synthesis ◽  
Model Complexity ◽  
The Arctic ◽  
Nutrient Inputs ◽  
Ecosystem Models ◽  
Ammonium Accumulation

Abstract. Arctic coastal ecosystems are rapidly changing due to climate warming, which makes modelling their productivity crucially important to better understand future changes. System primary production in these systems is highest during the pronounced spring bloom, typically dominated by diatoms. Eventually the spring blooms terminate due to silicon or nitrogen limitation. Bacteria can play an important role for extending bloom duration and total CO2 fixation through ammonium regeneration. Current ecosystem models often simplify the effects of nutrient co-limitations on algal physiology and cellular ratios and neglect bacterial driven regeneration, leading to an underestimation of primary production. Detailed biochemistry- and cell-based models can represent these dynamics but are difficult to tune in the environment. We performed a cultivation experiment that showed typical spring bloom dynamics, such as extended algal growth via bacteria ammonium remineralisation, and reduced algal growth and inhibited chlorophyll synthesis under silicate limitation, and gradually reduced nitrogen assimilation and chlorophyll synthesis under nitrogen limitation. We developed a simplified dynamic model to represent these processes. The model also highlights the importance of organic matter excretion, and post bloom ammonium accumulation. Overall, model complexity is comparable to other ecosystem models used in the Arctic while improving the representation of nutrient co-limitation related processes. Such model enhancements that now incorporate increased nutrient inputs and higher mineralization rates in a warmer climate will improve future predictions in this vulnerable system.

scholarly journals ECOSMO II(CHL): a marine biogeochemical model for the North Atlantic and the Arctic

2021 ◽  
Author(s):  
Veli Çağlar Yumruktepe ◽  
Annette Samuelsen ◽  
Ute Daewel
Keyword(s):  
Primary Production ◽  
Baltic Sea ◽  
Chlorophyll A ◽  
North Sea ◽  
North Atlantic ◽  
Spring Bloom ◽  
The Arctic ◽  
The North ◽  
The North Sea ◽  
The North Atlantic

Abstract. ECOSMO II is a fully coupled bio-physical model of 3d-hydrodynamics with an intermediate complexity N(utrient) P(hytoplankton) Z(ooplankton) D(etritus) type biology including sediment-water column exchange processes originally formulated for the North Sea and Baltic Sea. Here we present an updated version of the model incorporating chlorophyll a as a prognostic state variable: ECOSMO II(CHL). The version presented here is online coupled to the HYCOM ocean model. The model is intended to be used for regional configurations for the North Atlantic and the Arctic incorporating coarse to high spatial resolutions for hind-casting and operational purposes. We provide the full descriptions of the changes in ECOSMO II(CHL) from ECOSMO II and provide the evaluation for the inorganic nutrients and chlorophyll variables, present the modeled biogeochemistry of the Nordic Seas and the Artic and experiments on various parameterization sets as use cases targeting chlorophyll a dynamics. The model evaluations demonstrated that the simulations are consistent with the large-scale climatological nutrient settings, and are capable of representing regional and seasonal changes. The Norwegian and Barents Seas primary production show distinct seasonal patterns with a pronounced spring bloom dominated by diatoms and low biomass during winter months. The Norwegian Sea annual primary production is around double that of the Barents Sea while also having an earlier spring bloom. The parameterization experiments showed that the representation of open ocean chlorophyll a benefits from using higher phytoplankton growth and zooplankton grazing rates with less photosynthesis efficiency compared to the original implementation of ECOSMO II, which was valid for the North Sea and the Baltic Sea representing coastal domains. Thus, for open ocean modeling studies, we suggest the use of the parameterization sets presented in this study.

scholarly journals Contrasting trends in sea ice and primary production in the Bering Sea and Arctic Ocean

2012 ◽  
Vol 69 (7) ◽  
pp. 1180-1193 ◽  
Author(s):  
Zachary W. Brown ◽  
Kevin R. Arrigo
Keyword(s):  
Sea Ice ◽  
Primary Production ◽  
Arctic Ocean ◽  
Bering Sea ◽  
Net Primary Productivity ◽  
Remote Sensing Data ◽  
Ice Cover ◽  
The Arctic ◽  
Light Limitation ◽  
The Bering Sea

Abstract Brown, Z. W., and Arrigo, K. R. 2012. Contrasting trends in sea ice and primary production in the Bering Sea and Arctic Ocean. – ICES Journal of Marine Science, 69: . Satellite remote sensing data were used to examine recent trends in sea-ice cover and net primary productivity (NPP) in the Bering Sea and Arctic Ocean. In nearly all regions, diminished sea-ice cover significantly enhanced annual NPP, indicating that light-limitation predominates across the seasonally ice-covered waters of the northern hemisphere. However, long-term trends have not been uniform spatially. The seasonal ice pack of the Bering Sea has remained consistent over time, partially because of winter winds that have continued to carry frigid Arctic air southwards over the past six decades. Hence, apart from the “Arctic-like” Chirikov Basin (where sea-ice loss has driven a 30% increase in NPP), no secular trends are evident in Bering Sea NPP, which averaged 288 ± 26 Tg C year−1 over the satellite ocean colour record (1998–2009). Conversely, sea-ice cover in the Arctic Ocean has plummeted, extending the open-water growing season by 45 d in just 12 years, and promoting a 20% increase in NPP (range 441–585 Tg C year−1). Future sea-ice loss will likely stimulate additional NPP over the productive Bering Sea shelves, potentially reducing nutrient flux to the downstream western Arctic Ocean.

Spatial variability in rates of Net Primary Production (NPP) and onset of the spring bloom in Greenland shelf waters

2021 ◽  
pp. 102655
Author(s):  
Maria Vernet ◽  
Ingrid Ellingsen ◽  
Christian Marchese ◽  
Simon Bélanger ◽  
Mattias Cape ◽  
...  
Keyword(s):  
Spatial Variability ◽  
Primary Production ◽  
Spring Bloom ◽  
Net Primary Production

Size-fractionated surface phytoplankton in the Kara and Laptev Seas: environmental control and spatial variability

2021 ◽  
Vol 664 ◽  
pp. 59-77
Author(s):  
AB Demidov ◽  
IN Sukhanova ◽  
TA Belevich ◽  
MV Flint ◽  
VI Gagarin ◽  
...  
Keyword(s):  
Spatial Variability ◽  
Primary Production ◽  
Water Temperature ◽  
Environmental Control ◽  
Size Structure ◽  
Total Carbon ◽  
The Arctic ◽  
Size Groups ◽  
Phytoplankton Size ◽  
Phytoplankton Size Structure

Climate-induced variability of phytoplankton size structure influences primary productivity, marine food web dynamics, biosedimentation and exchange of CO2 between the atmosphere and ocean. Investigation of phytoplankton size structure in the Arctic Ocean is important due to rapid changes in its ecosystems related to increasing temperature and declining sea ice cover. We estimated the contribution of surface micro-, nano- and picophytoplankton to the total carbon biomass, chlorophyll a concentration and primary production in the Kara and Laptev Seas and investigated the relationships of these phytoplankton size groups with environmental factors which determine their spatial variability. Additionally, we compared chlorophyll specific carbon fixation rate, specific growth rate and carbon to chlorophyll ratios among different phytoplankton size groups. The investigation was carried out from August to September 2018. Generally, picophytoplankton was dominant in terms of chlorophyll a and primary production in the whole study area. The spatial variability of phytoplankton size classes was influenced by river discharge and relied mainly on water temperature, salinity and dissolved silicon concentration. Microphytoplankton prevailed across the river runoff region under conditions of low salinity and relatively high water temperature, while picophytoplankton was predominant under conditions of high salinity and low water temperature. Our study is the first to characterize size-fractionated phytoplankton abundance in the Kara and Laptev Seas, and provides a baseline for future assessment of the response of Kara and Laptev Sea ecosystems to climate-induced processes using phytoplankton size structure.

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