Environmental control of open‐ocean phytoplankton groups: Now and in the future

Abstract

Climate change will alter concurrently many environmental factors that exert control over oceanic phytoplankton. Recent laboratory culture work, shipboard experiments, and field surveys reveal many remaining unknowns about the bottom-up controls for five globally important algal groups. Increasing uncertainties exist, respectively, for picocyanobacteria, diatoms, Phaeocystis spp., N 2 -fixing cyanobacteria, and coccolithophores. This missing information about current environmental controls will hinder progress in modeling how these phytoplankton will be influenced by climate change. A review of conceptual approaches used to elucidate the relationship between environmental controls and phytoplankton dominance, from Margalef's mandala to functional traits, uncovered limitations regarding their application to climate-change scenarios. For example, these previous approaches have insufficient scope or dimensions to take into account the confounding effects of synergistic and antagonistic interactions of multiple environmental change variables. A new approach is needed that considers all of the different environmental properties altered by climate change and their interactions while at the same time permitting a subset of the most significant controls for a specific phytoplankton group to be isolated and evaluated in factorial matrix perturbation experiments. We advocate three new interlinked approaches, including environmental clusters that incorporate all factors (temperature, CO 2 , light, nutrients, and trace metals), which both exert control over present-day floristics and will be altered by climate change. By carefully linking a holistic conceptual approach to a reductionist experimental design, the future responses of open-ocean phytoplankton groups to a complex, rapidly changing environment can be better predicted.

Phytoplankton community dynamics during late spring coccolithophore blooms at the continental margin of the Celtic Sea (North East Atlantic, 2006–2008)

“…The general scenario for phytoplankton bloom development and species succession in the NE Atlantic (Leblanc et al, 2009 and references therein): the replacement of early spring diatom blooms by coccolithophores, most probably occurs as a result of changing light conditions, mixed layer shoaling, and depletion of dSi levels (Boyd et al, 2010). Our data show that this generally accepted diatom-to-coccolithophore succession scenario is not universal, and that diatom and coccolithophore growth can (Fig.…”

“…(Gomez et al, 2005;Bar Zeev et al, 2008). In that case their growth would have been limited by low PO 4 and dSi concentrations rather than NO x , or possibly the availability of trace metals such as iron (Boyd et al, 2010), for which coccolithophores, on the other hand, were shown to have low requirements and high affinity (Sunda and Huntsman, 1995;Muggli and Harrison, 1996).…”

“…While the annual occurrence of extensive coccolithophore blooms in late spring in the NE Atlantic is well-documented (Leblanc et al, 2009 and references therein), there is no consensus on the factors triggering coccolithophorid blooms and modulating the turnover time of the calcite they produce (Lessard et al, 2005;Poulton et al, , 2010Boyd et al, 2010). Changes in environmental control factors such as light intensity, water column stability, temperature, CO 2 concentration, nitrate and phosphate levels and their ratio, and the concentration trace metals (e.g.…”

“…Changes in environmental control factors such as light intensity, water column stability, temperature, CO 2 concentration, nitrate and phosphate levels and their ratio, and the concentration trace metals (e.g. Fe, Zn, and Mn) have been shown to influence coccolithophore physiology and control phytoplankton community assemblage to various extents (Nanninga and Tyrrell, 1996;Zondervan, 2007;Boyd et al, 2010, and references therein). However, only few studies have described the structure and the spatial and temporal dynamics of phytoplankton communities during these blooms along the western European continental margin (Head et al, 1998;Joint et al, 2001;Fileman et al, 2002;Lampert et al, 2002).…”

Processes and patterns of oceanic nutrient limitation

“…The availability of nutrients may thus also set a limit on the overall community biomass yield (Box 1) 18,19 . Within the diverse microbial communities that characterize oceanic systems, the degree of growth rate limitation may vary between populations [20][21][22] , for example because of differences in cell size 23,24 and cellular element requirements 8,25 (Box 2).…”