Decoding Size Distribution Patterns in Marine and Transitional Water Phytoplankton: From Community to Species Level

Abstract

Understanding the mechanisms of phytoplankton community assembly is a fundamental issue of aquatic ecology. Here, we use field data from transitional (e.g. coastal lagoons) and coastal water environments to decode patterns of phytoplankton size distribution into organization and adaptive mechanisms. Transitional waters are characterized by higher resource availability and shallower well-mixed water column than coastal marine environments. Differences in physico-chemical regime between the two environments have been hypothesized to exert contrasting selective pressures on phytoplankton cell morphology (size and shape). We tested the hypothesis focusing on resource availability (nutrients and light) and mixed layer depth as ecological axes that define ecological niches of phytoplankton. We report fundamental differences in size distributions of marine and freshwater diatoms, with transitional water phytoplankton significantly smaller and with higher surface to volume ratio than marine species. Here, we hypothesize that mixing condition affecting size-dependent sinking may drive phytoplankton size and shape distributions. The interplay between shallow mixed layer depth and frequent and complete mixing of transitional waters may likely increase the competitive advantage of small phytoplankton limiting large cell fitness. The nutrient regime appears to explain the size distribution within both marine and transitional water environments, while it seem does not explain the pattern observed across the two environments. In addition, difference in light availability across the two environments appear do not explain the occurrence of asymmetric size distribution at each hierarchical level. We hypothesize that such competitive equilibria and adaptive strategies in resource exploitation may drive by organism’s behavior which exploring patch resources in transitional and marine phytoplankton communities.

Abiotic Changes Driving Microphytoplankton Functional Diversity in Admiralty Bay, King George Island (Antarctica)

“…The use of classification schemes based on functional groups to determine the ecological dynamics of phytoplankton is a growing theme in environmental sciences (Kruk et al, 2002;Litchman et al, 2010;Moser et al, 2014;Roselli and Basset, 2015;Moser et al, 2017;Roselli et al, 2017). Such schemes can help explain the distribution of species along environmental gradients, as well as phytoplankton diversity and community structure (Litchman et al, 2010;Naselli-Flores et al, 2007).…”

Body size evolution and habitat colonization across 100 million years (Late Jurassic–Paleocene) of the actinopterygian evolutionary history

“…Ecological adaptations and body size impact the evolutionary history of clades (Sibly & Brown, 2007), but the effects of habitat over body size evolution remain poorly known. To date, the effect of habitat on body size evolution has been addressed for phytoplankton groups where marine species show larger sizes than non-marine species, probably in response to different chemical and physical properties of habitats (Litchman, Klausmeier, & Yoshiyama, 2009;Nakov, Theriot, & Alverson, 2014;Roselli & Basset, 2015). Yet, the effect of habitat on size remains uncertain within vertebrates and clades encompassing large taxic diversities in different habitat are scarce.…”

Complementarity of the multidimensional functional and the taxonomic approaches to study phytoplankton communities in three Mediterranean coastal lagoons of different trophic status

“…These approaches were based on (1) the known responses of species to environmental conditions, including abiotic, biotic parameters, and disturbances; and (2) their role in ecosystem functioning. More recently, studies have used multivariate statistics to uncover the links between the community composition in terms of functional groups and the environmental conditions (Kruk et al, 2010;Palffy et al, 2013;Roselli & Basset, 2015;Weithoff & Gaedke, 2017). So far, functional approaches in phytoplankton ecology have been mainly based on allocating species into functional groups without observing the traits of individual organisms.…”