Perturbation dynamics of a planktonic ecosystem

Healey, Katherine; Monahan, Adam H.; Ianson, Debby

doi:10.1357/002224009791218841

Cited by 5 publications

(7 citation statements)

References 58 publications

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“…Lab experiments and field programs show that sinking velocities of diatoms and their associated aggregates exhibit sinking velocities between 10 and 1000 m/d [ Iverson and Ploug , ; Ivers e n and Ploug , 2010]. Aggregates likely form within the large blooms of the region, and have been shown to contribute significantly to the sinking flux of organic matter [ Jackson et al ., ; Healey et al ., ; Ianson et al ., ]. At the bed, all detritus respires and returns to the nutrient pool as in Fennel et al .…”

Section: Methodsmentioning

confidence: 99%

Seasonal and interannual oxygen variability on the Washington and Oregon continental shelves

et al. 2015

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The coastal waters of the northern portion of the California Current System experience a seasonal decline in oxygen concentrations and hypoxia over the summer upwelling season that results in negative impacts on habitat for many organisms. Using a regional model extending from 43 N to 50 N, with an oxygen component developed in this study, drivers of seasonal and regional oxygen variability are identified. The model includes two pools of detritus, which was an essential addition in order to achieve good agreement with the observations. The model was validated using an extensive array of hydrographic and moored observations. The model captures the observed seasonal decline as well as spatial trends in bottom oxygen. Spatially, three regions of high respiration are identified as locations where hypoxia develops each modeled year. Two of the regions are previously identified recirculation regions. The third region is off of the Washington coast. Sediment oxygen demand causes the region on the Washington coast to be susceptible to hypoxia and is correlated to the broad area of shallow shelf (<60 m) in the region. Respiration and circulation-driven divergence contribute similar (60, 40%, respectively) amounts to the integrated oxygen budget on the Washington coast while respiration dominates the Oregon coast. Divergence, or circulation, contributes to the oxygen dynamics on the shelf in two ways: first, through the generation of retention features, and second, by determining variability.

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Section: Methodsmentioning

confidence: 99%

Seasonal and interannual oxygen variability on the Washington and Oregon continental shelves

et al. 2015

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“…But the linear perturbation method without accounting for the effects of nonlinear processes tells us that the optimal perturbation structures are independent from the magnitude of the perturbation, as mentioned by Healey et al . []. The above differences indicate that the structures of the optimal perturbations obtained from the linear method and the CNOP method are different, which implies that nonlinear processes have important effects on the perturbation structures.…”

Section: Resultsmentioning

confidence: 99%

“…Healey et al . [] did an interesting work on the perturbation dynamics of ocean planktonic ecosystem using linear perturbation theory. The present study overcomes the limitations of the linear theory.…”

Section: Discussionmentioning

confidence: 99%

“…So Healey et al . [] linearized a simple nonlinear model around a steady state and then examined the responses of the linearized model to optimally initial perturbations to reveal the basic dynamics of the model. They regarded the perturbations as small changes to the stable state that may be induced by eddy advection, mixing, or mixed layer depth variability and so on.…”

Section: Introductionmentioning

confidence: 99%

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Responses of the ocean planktonic ecosystem to finite‐amplitude perturbations

Wang

2014

JGR Oceans

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The responses of the ocean planktonic ecosystem to finite-amplitude perturbations are investigated using an ocean planktonic ecosystem model. Through changing the higher predation rate on zooplankton, multiple equilibria of the model, namely ''high-nutrient'' and ''low-nutrient'' states, are obtained under certain parameter values. Based on these states, the perturbations with maximum nonlinear growth are determined using the conditional nonlinear optimal perturbation (CNOP) method. The linear and nonlinear evolutions of the CNOP perturbation are compared. The results show that the nonlinear evolution of the perturbation leads to predator-prey oscillations with larger amplitude than the linear evolution. Besides, after the perturbation amplitude exceeds a critical value, the nonlinear evolution of the perturbation will induce the linearly stable ecosystem state to lose the stability and become nonlinearly unstable. This implies that nonlinear processes have important impacts on the stability of the ecosystem. Specifically, we identify the nonlinear processes related to zooplankton grazing to impact the stability most for the high-nutrient state, while for the low-nutrient state the main nonlinear process affecting the stability is the uptake process. These results help to improve our understanding of the sensitivity of the oceanic ecosystem model to finite-amplitude perturbations and the underlying nonlinear stability properties.

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“…where i ρ denotes the optimum growth temperature for the biomass of functional type and is a temperature sensitivity parameter quantifying the increase in the densityindependent growth rate for a 1°C change in temperature towards the optimum temperature i ρ and vice-versa. Saturating functions of irradiance and nutrient concentration and their combination with a minimum function are commonly used to moderate growth rate (Denman & Peña 1999, Healey et al 2009). The net growth rate is the density-independent growth rate of the i th functional type at optimal temperature, irradiance and nitrogen concentration.…”

Section: The Modelmentioning

confidence: 99%

Phytoplankton traits from long-term oceanographic time-series

Mutshinda

Finkel

Widdicombe

et al. 2017

Preprint

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Trait values are usually extracted from laboratory studies of single phytoplankton species, which presents challenges for understanding the immense diversity of phytoplankton species and the wide range of dynamic ocean environments. Here we use a Bayesian approach and a trait-based model to extract trait values for four functional types and ten diatom species from field data collected at Station L4 in the Western Channel Observatory. We find differences in maximum net growth rate, temperature optimum and sensitivity, half-saturation constants for light and nitrogen, and density-dependent loss terms across the functional types. We find evidence of very high linear loss rates, suggesting that grazing may be even more important than commonly assumed and differences in densitydependent loss rates across functional types, indicating the presence of strong niche differentiation among functional types. Low half-saturation constants for nitrogen at the functional type level may indicate widespread mixotrophy. At the species level, we find a wide range of density-dependent effects, which may be a signal of diversity in grazing susceptibility or biotic interactions. This approach may be a way to obtain more realistic and better-constrained trait-values for functional types to be used in ecosystem modeling.

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Perturbation dynamics of a planktonic ecosystem

Cited by 5 publications

References 58 publications

Seasonal and interannual oxygen variability on the Washington and Oregon continental shelves

Seasonal and interannual oxygen variability on the Washington and Oregon continental shelves

Responses of the ocean planktonic ecosystem to finite‐amplitude perturbations

Phytoplankton traits from long-term oceanographic time-series

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