Plankton community properties determined by nutrients and size-selective feeding

Fuchs, Heidi L.; Franks, Peter J. S.

doi:10.3354/meps08716

Cited by 105 publications

(158 citation statements)

References 118 publications

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“…This is consistent with general observations that the ODB of copepods span nearly 3 orders of magnitude (Fuchs & Franks 2010), and are food-limited with half saturation constants of the order of 200 mgC m −3 (Hansen et al 1997). That is, copepods live in a dilute environment (Kiørboe 2011) and simply cannot afford to be too selective; they should consume most of what they encounter.…”

Section: Should Zooplankton Be Selective In Their Diet?supporting

confidence: 73%

“…While the general concept of prey selectivity in terms of profitability can be applied to any number of cases, we wish to highlight its role in determining a grazer's size preference and size class breadth of diet (Hansen et al 1997, Fuchs & Franks 2010, Wirtz 2012b. Size after all is the key trait governing trophic interactions, particularly in determining the carbon and energy content of a prey item.…”

Section: Size-based Applicationmentioning

confidence: 99%

“…In choosing this example, we are mindful that in a full size-based ecosystem model (e.g. Fuchs & Franks 2010), the actual size spectrum will be dynamic, being governed by the trophic interactions of growth and mortality within and between prey size classes. Provided we choose the width of each size class to be small (i.e.…”

Section: Size-based Applicationmentioning

confidence: 99%

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Optimal foraging in marine ecosystem models: selectivity, profitability and switching

Visser¹,

Fiksen²

2013

Mar. Ecol. Prog. Ser.

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One of the most troubling aspects of ecosystem models is the use of rather arbitrary feeding and preference functions. The predictions of plankton functional type models have been shown to be highly sensitive to the choice of foraging model, particularly in multiple prey situations. Here we propose ecological mechanics and evolutionary logic as a solution to diet selection in ecosystem models. When a predator can consume a range of prey items, it has to choose which foraging mode to use, which prey to ignore and which ones to pursue, and animals are known to be particularly skilled in adapting their diets towards the most profitable prey items. We present a simple algorithm for plankton feeding on a size-spectrum of prey with particular energetic content, handling times and capture probabilities. We show that the optimal diet breadth changes with relative densities, but in a different way to the preference functions commonly used in models today. Indeed, depending on prey class resolution, optimal foraging can yield feeding rates that are considerably different from the 'switching functions' often applied in marine ecosystem models. Dietary inclusion is dictated by 2 optimality choices: (1) the diet breadth and (2) the actual feeding mode. The optimality model does not generate 'safety in low densities' for prey, as the 'switching function' does in ecosystem models, unless predators are shifting feeding mode adaptively. The actual diet, feeding rate and energy flux in ecosystem models can be determined by letting predators maximise energy intake or more properly, some measure of fitness where predation risk and cost are also included. An optimal foraging or fitness-maximising approach will give marine ecosystem models a sound principle to determine trophic interactions.

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Section: Should Zooplankton Be Selective In Their Diet?supporting

confidence: 73%

Section: Size-based Applicationmentioning

confidence: 99%

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Optimal foraging in marine ecosystem models: selectivity, profitability and switching

Visser¹,

Fiksen²

2013

Mar. Ecol. Prog. Ser.

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“…Phytoplankton are consumed by small, medium, and large zooplankton groups (SZ, MZ, and LZ), where small zooplankton are microzooplankton < 200 µm in equivalent spherical diameter (ESD), medium zooplankton are smallto medium-bodied copepods (200 µm-2 mm ESD), and large zooplankton are large copepods and euphausiids (2 mm-2 cm ESD). Predator-prey size ratios were chosen based on typical ratios observed for ciliates and copepods (Fuchs and Franks, 2010;Hansen et al, 1994). Feeding is modeled as a type II saturating response with weak densitydependent switching between herbivory and carnivory (Stock et al, 2008).…”

Section: (Cmip5;mentioning

confidence: 99%

Drivers of trophic amplification of ocean productivity trends in a changing climate

2014

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Abstract. Pronounced projected 21st century trends in regional oceanic net primary production (NPP) raise the prospect of significant redistributions of marine resources. Recent results further suggest that NPP changes may be amplified at higher trophic levels. Here, we elucidate the role of planktonic food web dynamics in driving projected changes in mesozooplankton production (MESOZP) found to be, on average, twice as large as projected changes in NPP by the latter half of the 21st century under a high emissions scenario in the Geophysical Fluid Dynamics Laboratory's ESM2M-COBALT (Carbon, Ocean Biogeochemistry and Lower Trophics) earth system model. Globally, MESOZP was projected to decline by 7.9 % but regional MESOZP changes sometimes exceeded 50 %. Changes in three planktonic food web properties -zooplankton growth efficiency (ZGE), the trophic level of mesozooplankton (MESOTL), and the fraction of NPP consumed by zooplankton (zooplankton-phytoplankton coupling, ZPC), explain the projected amplification. Zooplankton growth efficiencies (ZGE) changed with NPP, amplifying both NPP increases and decreases. Negative amplification (i.e., exacerbation) of projected subtropical NPP declines via this mechanism was particularly strong since consumers in the subtropics have limited surplus energy above basal metabolic costs. Increased mesozooplankton trophic level (MESOTL) resulted from projected declines in large phytoplankton production. This further amplified negative subtropical NPP declines but was secondary to ZGE and, at higher latitudes, was often offset by increased ZPC. Marked ZPC increases were projected for high-latitude regions experiencing shoaling of deep winter mixing or decreased winter sea iceboth tending to increase winter zooplankton biomass and enhance grazer control of spring blooms. Increased ZPC amplified projected NPP increases in the Arctic and damped projected NPP declines in the northwestern Atlantic and Southern Ocean. Improved understanding of the physical and biological interactions governing ZGE, MESOTL and ZPC is needed to further refine estimates of climate-driven productivity changes across trophic levels.

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“…A quantitative measure termed ''edibility'' not only depends on prey properties, but also on predator preferences, thus denotes a predator-specific feature. In sizebased models, trophic linkages are therefore formulated as a function of both body-size as the basic prey trait and optimal prey size as the major consumer trait (Armstrong 2003;Fuchs and Franks 2010;Baird 2010;Banas 2011).…”

Section: Introductionmentioning

confidence: 99%

Mechanistic origins of variability in phytoplankton dynamics. Part II: analysis of mesocosm blooms under climate change scenarios

Wirtz

Sommer²

2013

Mar Biol

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Driving factors of phytoplankton spring blooms have been discussed since long, but rarely analyzed quantitatively. Here, we use a mechanistic size-based ecosystem model to reconstruct observations made during the Kiel mesocosm experiments (2005)(2006). The model accurately hindcasts highly variable bloom developments including community shifts in cell size. Under low light, phytoplankton dynamics was mostly controlled by selective mesozooplankton grazing. Selective grazing also explains initial dominance of large diatoms under high light conditions. All blooms were mainly terminated by aggregation and sedimentation. Allometries in nutrient uptake capabilities led to a delayed, post-bloom dominance of small species. In general, biomass and trait dynamics revealed many mutual dependencies, while growth factors decoupled from the respective selective forces. A size shift induced by one factor often changed the growth dependency on other factors. Within climate change scenarios, these indirect effects produced large sensitivities of ecosystem fluxes to the size distribution of winter phytoplankton. These sensitivities exceeded those found for changes in vertical mixing, whereas temperature changes only had minimal impacts.

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Plankton community properties determined by nutrients and size-selective feeding

Cited by 105 publications

References 118 publications

Optimal foraging in marine ecosystem models: selectivity, profitability and switching

Optimal foraging in marine ecosystem models: selectivity, profitability and switching

Drivers of trophic amplification of ocean productivity trends in a changing climate

Mechanistic origins of variability in phytoplankton dynamics. Part II: analysis of mesocosm blooms under climate change scenarios

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