Global patterns of phytoplankton nutrient and light colimitation inferred from an optimality‐based model

Arteaga, Lionel; Pahlow, Markus; Oschlies, Andreas

doi:10.1002/2013gb004668

Cited by 47 publications

(59 citation statements)

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“…The mean meridional trend of ANCP increases south of the STF (∼ 40°S), associated with an increase in the surface concentration of nitrate and silicate (Figure ). The STF marks the transition from nitrate‐limited to nitrate‐replete conditions for phytoplankton growth (Arteaga et al, ; Moore et al, ). Paradoxically, the increase in ANCP estimates also occurs over an area of the Southern Ocean where the surface iron concentration decreases to its lowest values (Figure b).…”

Section: Resultsmentioning

confidence: 99%

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Nutrient Controls on Export Production in the Southern Ocean

Arteaga

Pahlow

Bushinsky

et al. 2019

Global Biogeochemical Cycles

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We use observations from novel biogeochemical profiling floats deployed by the Southern Ocean Carbon and Climate Observations and Modeling program to estimate annual net community production (ANCP; associated with carbon export) from the seasonal drawdown of mesopelagic oxygen and surface nitrate in the Southern Ocean. Our estimates agree with previous observations in showing an increase in ANCP in the vicinity of the polar front (∼3 mol C m−2 y−1), compared to lower rates in the subtropical zone (≤ 1 mol C m−2 y−1) and the seasonal ice zone (<2 mol C m−2 y−1). Paradoxically, the increase in ANCP south of the subtropical front is associated with elevated surface nitrate and silicate concentrations, but decreasing surface iron. We hypothesize that iron limitation promotes silicification in diatoms, which is evidenced by the low silicate to nitrate ratio of surface waters around the Antarctic polar front. High diatom silicification increases the ballasting effect of particulate organic carbon and overall ANCP in this region. A model‐based assessment of our methods shows a good agreement between ANCP estimates based on oxygen and nitrate drawdown and the modeled downward organic carbon flux at 100 m. This agreement supports the presumption that net biological consumption is the dominant process affecting the drawdown of these chemical tracers and that, given sufficient data, ANCP can be inferred from observations of oxygen and/or nitrate drawdown in the Southern Ocean.

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Section: Resultsmentioning

confidence: 99%

“…In the Southern Ocean, biological productivity is limited primarily by nitrate (NO 3 ) in the subtropical zone (STZ), north of the subtropical front (STF) (∼40°S) (Arteaga et al, ; Moore et al, ). South of 40°S, iron (Fe) is considered the main limiting nutrient of phytoplankton growth (Boyd et al, ; Martin et al, ; Moore et al, ).…”

Section: Introductionmentioning

confidence: 99%

Nutrient Controls on Export Production in the Southern Ocean

Arteaga

Pahlow

Bushinsky

et al. 2019

Global Biogeochemical Cycles

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“…Our findings suggest that the steep chlorophyll gradients across the coastal transition zone are mainly driven by the nutrient gradients, but they are first amplified by the acclimative capacity, and then further by higher Chl : C ratios at the coastal waters. The large variations in simulated Chl : C ratios within the SNS, both in space and time, indicate that ignoring photoacclimation can lead to potentially flawed estimates for primary production or phytoplankton biomass as was recently pointed out by Arteaga et al (2014) and Behrenfeld et al (2015), based on the variability of Chl : C ratios at global scales. Here we show that this warning applies especially in the coastal environments characterized by steep resource gradients, which may be critical, given the increasing recognition of the role of coastal-shelf systems in the global carbon and nutrient cycling (Fennel, 2010;Bauer et al, 2013).…”

Section: Discussionmentioning

confidence: 99%

The acclimative biogeochemical model of the southern North Sea

Kerimoglu¹,

Hofmeister²,

Maerz³

et al. 2017

Biogeosciences

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Abstract. Ecosystem models often rely on heuristic descriptions of autotrophic growth that fail to reproduce various stationary and dynamic states of phytoplankton cellular composition observed in laboratory experiments. Here, we present the integration of an advanced phytoplankton growth model within a coupled three-dimensional physicalbiogeochemical model and the application of the model system to the southern North Sea (SNS) defined on a relatively high resolution ( ∼ 1.5-4.5 km) curvilinear grid. The autotrophic growth model, recently introduced by Wirtz and Kerimoglu (2016), is based on a set of novel concepts for the allocation of internal resources and operation of cellular metabolism. The coupled model system consists of the General Estuarine Transport Model (GETM) as the hydrodynamical driver, a lower-trophic-level model and a simple sediment diagenesis model. We force the model system with realistic atmospheric and riverine fluxes, background turbidity caused by suspended particulate matter (SPM) and open ocean boundary conditions. For a simulation for the period 2000-2010, we show that the model system satisfactorily reproduces the physical and biogeochemical states of the system within the German Bight characterized by steep salinity; nutrient and chlorophyll (Chl) gradients, as inferred from comparisons against observation data from long-term monitoring stations; sparse in situ measurements; continuous transects; and satellites. The model also displays skill in capturing the formation of thin chlorophyll layers at the pycnocline, which is frequently observed within the stratified regions during summer. A sensitivity analysis reveals that the vertical distributions of phytoplankton concentrations estimated by the model can be qualitatively sensitive to the description of the light climate and dependence of sinking rates on the internal nutrient reserves. A non-acclimative (fixed-physiology) version of the model predicted entirely different vertical profiles, suggesting that accounting for physiological flexibility might be relevant for a consistent representation of the vertical distribution of phytoplankton biomass. Our results point to significant variability in the cellular chlorophyll-to-carbon ratio (Chl : C) across seasons and the coastal to offshore transition. Up to 3-fold-higher Chl : C at the coastal areas in comparison to those at the offshore areas contribute to the steepness of the chlorophyll gradient. The model also predicts much higher phytoplankton concentrations at the coastal areas in comparison to its non-acclimative equivalent. Hence, findings of this study provide evidence for the relevance of physiological flexibility, here reflected by spatial and seasonal variations in Chl : C, for a realistic description of biogeochemical fluxes, particularly in the environments displaying strong resource gradients.

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“…Instead, such global models tend to rely on identifying the most limiting resource that then governs carbon fixation rates. While some models are moving away from using the external nutrient concentration of resources to drive growth rates (Arteaga et al, ; Aumont et al, ), they still rely on a limited suite of resources and on “law of the minimum” parameterizations. In the future, it is important for models to expand their scope beyond N, P, Si, and Fe to consider other important resources, such as Co, that are known to be depleted in seawater (Moore et al, ) and to revisit the resource limitation parameterizations to account for the potentially important colimitation between different resources.…”

Section: Toward Quantifying the Biological Role Of Cobaltmentioning

confidence: 99%

The Role of External Inputs and Internal Cycling in Shaping the Global Ocean Cobalt Distribution: Insights From the First Cobalt Biogeochemical Model

Tagliabue

Hawco

Bundy

et al. 2018

Global Biogeochemical Cycles

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Cobalt is an important micronutrient for ocean microbes as it is present in vitamin B 12 and is a co‐factor in various metalloenzymes that catalyze cellular processes. Moreover, when seawater availability of cobalt is compared to biological demands, cobalt emerges as being depleted in seawater, pointing to a potentially important limiting role. To properly account for the potential biological role for cobalt, there is therefore a need to understand the processes driving the biogeochemical cycling of cobalt and, in particular, the balance between external inputs and internal cycling. To do so, we developed the first cobalt model within a state‐of‐the‐art three‐dimensional global ocean biogeochemical model. Overall, our model does a good job in reproducing measurements with a correlation coefficient of >0.7 in the surface and >0.5 at depth. We find that continental margins are the dominant source of cobalt, with a crucial role played by supply under low bottom‐water oxygen conditions. The basin‐scale distribution of cobalt supplied from margins is facilitated by the activity of manganese‐oxidizing bacteria being suppressed under low oxygen and low temperatures, which extends the residence time of cobalt. Overall, we find a residence time of 7 and 250 years in the upper 250 m and global ocean, respectively. Importantly, we find that the dominant internal resupply process switches from regeneration and recycling of particulate cobalt to dissolution of scavenged cobalt between the upper ocean and the ocean interior. Our model highlights key regions of the ocean where biological activity may be most sensitive to cobalt availability.

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Global patterns of phytoplankton nutrient and light colimitation inferred from an optimality‐based model

Cited by 47 publications

References 45 publications

Nutrient Controls on Export Production in the Southern Ocean

Nutrient Controls on Export Production in the Southern Ocean

The acclimative biogeochemical model of the southern North Sea

The Role of External Inputs and Internal Cycling in Shaping the Global Ocean Cobalt Distribution: Insights From the First Cobalt Biogeochemical Model

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