A multicomponent model of phytoplankton size structure

Abstract

Size-fractionated filtration (SFF) is a direct method for estimating pigment concentration in various size classes. It is also common practice to infer the size structure of phytoplankton communities from diagnostic pigments estimated by high-performance liquid chromatography (HPLC). In this paper, the three-component model of Brewin et al. (2010) was fitted to coincident data from HPLC and from SFF collected along Atlantic Meridional Transect cruises. The model accounted for the variability in each data set, but the fitted model parameters differed for the two data sets. Both HPLC and SFF data supported the conceptual framework of the three-component model, which assumes that the chlorophyll concentration in small cells increases to an asymptotic maximum, beyond which further increase in chlorophyll is achieved by the addition of larger celled phytoplankton. The three-component model was extended to a multicomponent model of size structure using observed relationships between model parameters and assuming that the asymptotic concentration that can be reached by cells increased linearly with increase in the upper bound on the cell size. The multicomponent model was verified using independent SFF data for a variety of size fractions and found to perform well (0.628 r 0.989) lending support for the underlying assumptions. An advantage of the multicomponent model over the three-component model is that, for the same number of parameters, it can be applied to any size range in a continuous fashion. The multicomponent model provides a useful tool for studying the distribution of phytoplankton size structure at large scales.

Phytoplankton Size Structure in Association with Mesoscale Eddies off Central-Southern Chile: The Satellite Application of a Phytoplankton Size-Class Model

“…is similar to that found in the Atlantic Ocean by Brewin et al [44] (C NP m~2 .78 mg m −3 ), both using the in situ SFF method to derive size-specific Chl-a concentrations (Table 1). In contrast, Ward [46] found a lower asymptotic value (C NP m : 0.79 mg m −3 ) using the same technique, but the measurements excluded eutrophic and coastal areas.…”

“…In all cases, duplicate or triplicate samples were taken at different depths within the upper 100 m depth; samples collected within the first 10 m of the upper layer were used in this study. Total in situ Chl-a concentration for the subsequent analyses was calculated as the sum of the Chl-a values contributed by each PSC [41,43,44]. .…”

“…Most of the previous studies using the three-component model have been based on Chl-a data from oceanic waters, e.g., [41,43,44,48,52] and very few have included data from coastal waters [50,51]. Total Chl-a values in this study (0.1 to 18 mg m −3 ) include coastal and coastal transition waters in the Humboldt EBCS [74].…”

“…These approaches have been based on (i) the optical signatures of phytoplankton groups using the spectral shape of phytoplankton absorption (a ph : Phytoplankton Absorption spectra) to characterize the PSC, e.g., [36,42]; (ii) the relationship between Chl-a concentration by each PSC with total Chl-a (as an index of phytoplankton abundance or biomass) using high performance liquid chromatography [HPLC] pigment and/or size-fractionated filtration (SFF) in situ data e.g., [43][44][45]; and (iii) the relationship between the phytoplankton groups and environmental factors (sea surface temperature or irradiance) e.g., [41,46]. Most of these approaches have been applied to open ocean waters, e.g., [41][42][43][44][45]47,48], while fewer ones have been including more information of coastal waters and have been mainly based on pigments or absorption spectra from in situ data [49][50][51]. Furthermore, only one recent study has used satellite estimates of PSC to infer shifts in the phytoplankton community related to a cyclonic eddy in oceanic waters [52].…”

A Consumer's Guide to Satellite Remote Sensing of Multiple Phytoplankton Groups in the Global Ocean

“…The PSC output is most commonly grouped as pico-(0.2-2 µm), nano-(2-20 µm), and/or microplankton (>20 µm) following the size classification scheme proposed by Sieburth et al (1978). However, a few models allow for multicomponent size classes not constrained by the traditional size groupings (Roy et al, 2013;Brewin et al, 2014b). The PSD satellite output (Kostadinov et al, 2009(Kostadinov et al, , 2010Roy et al, 2013) can conform to the Sieburth et al (1978) size classification.…”