Phytoplankton traits from long-term oceanographic time-series

Abstract

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.

Responses of phytoplankton communities to the effect of internal wave‐powered upwelling

“…7e,f), and physical transport would have resulted in a dilution of the concentrations at shallower depths. Physiologically, high abundances of Synechococcus are often associated with high-temperature and high-irradiance niches (Flombaum et al 2013;Chen et al 2014;Xiao et al 2018b); dinoflagellates are better adapted to high temperature and low phosphate conditions (Irwin et al 2012;Xiao et al 2018a); haptophytes_6 have a low half-saturation constant for uptake of nitrate (Litchman et al 2007;Mutshinda et al 2017) and thus are usually abundant in oligotrophic waters (Brun et al 2015); and high abundances of chlorophytes are usually associated with freshwater (Carstensen et al 2015), perhaps a consequence of their stenohaline nature. Although for different reasons, the upwelling of cold, salty, and nutrient-rich waters could have had a negative effect on these phytoplankton.…”

Investigating equations for measuring dissolved inorganic nutrient uptake in oligotrophic conditions

“…I assumed that uncertainty in a was equal to AE 0.5. For ρ 0,is , ρ kan,is , and ρ reg,is , I assumed (regardless of what half-saturation constant was used in the model) that K NO3 = 0.1 μmol L −1 and K NH4 = 0.05 μmol L −1 based on prior data syntheses (Harrison et al 1996;Edwards et al 2012;Beltrán-Heredia et al 2017;Mutshinda et al 2017). It must be noted, however, that some studies have called into question the applicability of assuming any Michaelis-Menten half-saturation constant (Bonachela et al 2011;Tang and Maggi 2012), and that even if this approach is an accurate model, half-saturation constants vary by several of orders of magnitude.…”