Phytoplankton production modelling in three marine ecosystems—static versus dynamic approach

Abstract

Phytoplankton productivity is usually determined from water samples incubated at a number of irradiance levels during several hours. The resultant productivity-irradiance (P-E) curves are then used to estimate local and/or global phytoplankton production. However, there is growing evidence that these curves, referred as static, underestimate phytoplankton photosynthesis to a great deal, by assuming a stable response to light over the incubation period. One of the drawbacks of static P-E curves is the overestimation of photoinhibition.In this work, three one-dimensional vertically resolved models were developed as simply as possible, to investigate differences between static and dynamic phytoplankton productivity in three marine ecosystems: a turbid estuary, a coastal area and an open ocean ecosystem. The results show that, when photoinhibition development time is considered (dynamic model), the primary production estimates are always higher than when calculated with the static model. The quantitative importance of these differences varies with the type of ecosystem and it appears to be more important in coastal areas and estuaries (from 21 to 72%) than in oceanic waters (10%). Thus, these results suggest that primary production estimates, obtained under the assumption of a static behaviour response to light, may underestimate the real values of global phytoplankton primary production. Calculations suggest that the quantitative importance of this underestimation may be larger than the global missing carbon sink.

Reevaluating the Generality of an Empirical Model for Light-Limited Primary Production in the San Francisco Estuary

“…Volumetric determinations of primary production (in milligrams of carbon per cubic meter per day) were fit to a three-parameter function of PAR (Macedo and Duarte 2006):…”

Short-Term and Interannual Variability in Primary Production in the Low-Salinity Zone of the San Francisco Estuary

“…Although photoinhibition was usually observed in data from the incubations, it may be uncommon in the field because individual cells in a turbulent water column may be exposed to bright light for only limited periods (Macedo and Duarte 2006). The time constant for onset of photoinhibition is~1 h (Pahl-Wostl and Imboden 1990).…”

“…We fit the productivity vs. light data for each individual set of measurements to the three-parameter function of Macedo and Duarte (2006) using the measured productivity at each light level and the PAR data from the incubation site:…”

Climate Change Impacts on Seagrass Meadows and Macroalgal Forests: An Integrative Perspective on Acclimation and Adaptation Potential

“…Productivity models aim at describing the growth of algae and plants in a specific system, either through static (Eilers and Peeters, 1988) or dynamic (time-dependent) (Duarte and Ferreira, 1997) approaches, whereby the underlying mathematics is either empirical (Adams et al, 2017) or mechanistic (for a review see Macedo and Duarte, 2006). A major complication of the mechanistic approach is that its implementation requires extensive knowledge on the physiology and life history of the modeled species.…”