Dimensions of Marine Phytoplankton Diversity

Abstract

<p><strong>Abstract.</strong> Biodiversity of phytoplankton is important for ecosystem stability and marine biogeochemistry. However, the large scale patterns of diversity are not well understood, and are often poorly characterized in terms of statistical relationships with environmental factors (e.g. latitude, temperature, productivity). Here we use ecological theory and a global trait-based ecosystem model to provide mechanistic understanding of patterns of phytoplankton diversity. Our study suggests that phytoplankton diversity across three dimensions of trait space (size, biogeochemical function, and thermal tolerance) is controlled by a disparate combinations of drivers: the supply rate of the limiting resource, the imbalance in different resource supplies relative to competing phytoplanktons’ demands, size-selective grazing, and transport by the moving ocean. Using sensitivity studies we show that each dimension of diversity is controlled by different drivers. Models including only one (or two) of the trait dimensions will have different patterns of diversity than one which incorporates another trait dimension. We use the results of our theory/model exploration to infer the controls on the diversity patterns derived from field observations in meridional transects of the Atlantic and to explain why different taxa and size classes have differing patterns. These results suggest that it is unlikely that any single or even combination of environmental variables will be able to explain patterns of diversity.</p>

Temporal and Spatial Scales of Correlation in Marine Phytoplankton Communities

“…We also examine how cell size impacts our results and differentiate “small” (≥3 μm) and “large” (>3 μm) phytoplankton (Figures c, d, and S1). We separate phytoplankton by size in this manner because the allometric scaling for specific growth rates has a unimodal shape: it peaks for cells approximately 3 μm in equivalent spherical diameter but decreases for smaller and larger cells (Dutkiewicz et al, ; Marañón et al, ). Much like for gleaners and opportunists, small phytoplankton dominate in oligotrophic regions while larger phytoplankton dominate in more seasonal and eutrophic regions (Figures c and d).…”

“…Phytoplankton cell sizes increase logarithmically from 0.6 to 228 μm in equivalent spherical diameter, with each functional group having a characteristic range of sizes (Figure S1). Cell size determines differences in maximum growth rates, grazing, and sinking, as described in Dutkiewicz et al (). Following observations, the smallest phytoplankton (the prokaryotes and picoeukaryotes) have the lowest nutrient affinity, and the fastest growing are in the 3 μm cell size range (Marañón et al, ).…”

Large seasonal and spatial variation in nano- and microphytoplankton diversity along a Baltic Sea—North Sea salinity gradient

“…This may be due the greater impact of currents and stratification in the Skagerrak-Kattegat compared to the Baltic Sea 23 which may enhance species richness of plankton due to, for example, advection from the North Sea. Including water transport in ecological models was recently demonstrated important in order to attain a high diversity of phytoplankton 24 . Mean α (alpha) species richness and α ENS, which represent the diversity of an interacting ecological assemblage, also increased with salinity but the increases were more modest.…”

“…Our study provides insights into spatial and temporal variation in phytoplankton community structure and abundance along a broad salinity gradient. By simultaneously examining grazing, nutrients, and water transport, a recent ecosystem model demonstrated that phytoplankton diversity is sensitive to all these factors 24 . Here, we combined multiple environmental factors such as nutrients, temperature, and salinity, but could not identify the drivers of the seasonal variation in phytoplankton diversity.…”

Microbial diversity-informed modelling of polar marine ecosystem functions

“…Most existing models parameterize the complex bacterial remineralization processes of the (sinking) organic matter with depth as a function of POC concentration and temperature, or by fitting with power law functions. Cellular functions, taxa, and functional gene expression of other prokaryotes, such as cyanobacteria (Hellweger 2010;Martín-Figueroa, Navarro, and Florencio 2000;Miller et al 2013), or a diverse suite of microbial functional groups (Coles et al 2017;Dutkiewicz et al 2020) have been modelled so far; however, our study is the first to explicitly model bacterial groups of different physiological traits.…”