Phytoplankton community structuring and succession in a competition-neutral resource landscape

Abstract

Phytoplankton community composition and succession affect aquatic food webs and biogeochemistry. Resource competition is commonly viewed as an important governing factor for community structuring and this perception is imbedded in modern ecosystem models. Quantitative consideration of the physical spacing between phytoplankton cells, however, suggests that direct competition for growth-limiting resources is uncommon. Here we describe how phytoplankton size distributions and temporal successions are compatible with a competition-neutral resource landscape. Consideration of phytoplankton-herbivore interactions with proportional feeding size ranges yields small-cell dominated size distributions consistent with observations for stable aquatic environments, whereas predator–prey temporal lags and blooming physiologies shift this distribution to larger mean cell sizes in temporally dynamic environments. We propose a conceptual mandala for understanding phytoplankton community composition where species successional series are initiated by environmental disturbance, guided by the magnitude of these disturbances and nutrient stoichiometry, and terminated with the return toward a ‘stable solution’. Our conceptual mandala provides a framework for interpreting and modeling the environmental structuring of natural phytoplankton populations.

Protoplasmic streaming of chloroplasts enables rapid photoacclimation in large diatoms

“…The populations collapse at the end of the season when physical forces change the UML, and reintroduce nutrients to support the success of other species growing in the decreasing sunlight of autumn. As for the new mandala for diatom success (Behrenfeld et al 2021b), our photo-energetic concept complements it with another energetic coordinate and shows that the evolution towards large diatoms was due to a new vector-the ability of cells to change the absorbed energy of light by changing the specific absorption coefficient, not changing the cell concentration of chlorophyll.…”

“…For those that graze on these large diatoms, their lowered gC: cell-volume also makes them a lower-value food package than similarly sized other plankton (McBeain and Halsey, 2018). In addition, a new hypothesis proposes that a niche for large diatoms exists because of the non-static dynamics of the predator-prey ratio (Behrenfeld et al, 2021a(Behrenfeld et al, , 2021b; the existence of some lag time before the appearance of an adequatesized predator allows large diatoms to grow intensively. It is also likely that large-celled phytoplankton are relatively less susceptible to virus attack because although larger cells are more likely to encounter viruses, the decreased cell abundance provides insufficient hosts to support high rates of virus attack (Flynn et al, 2021).…”

“…Hypotheses centered on an abiotic regulation of phytoplankton structure imply that large cells can only be successful in a dynamic environment (Margalef, 1978;Villamaña et al, 2019). In the modern interpretation of the Margalef mandala, one of the coordinates is duration and magnitude of change in limiting resources (Behrenfeld et al, 2021b). Thus, with weak changes in limiting resources, small diatoms are suggested to gain the advantage; large diatoms are more successful with significant environmental change.…”

Editorial: Unraveling Mechanisms Underlying Annual Plankton Blooms in the North Atlantic and Their Implications for Biogenic Aerosol Properties and Cloud Formation

“…The NAAMES experience also yielded a variety of higherlevel syntheses regarding phytoplankton bloom hypotheses (Behrenfeld and Boss, 2018), diatom ecology and evolution (Behrenfeld et al, 2021a), phytoplankton size distributions and succession (Behrenfeld et al, 2021c), and a new interpretation of Hutchinson's (1961) "Paradox of the Plankton" regarding the unexpected diversity of phytoplankton species in water columns with few readily identifiable niches (Behrenfeld et al, 2021b).…”

Annual Dynamics of Phytoplankton in the Black Sea in Relation to Wind Exposure

“…The central biotic regulators of phytoplankton structure and productivity are considered to be the pressure of herbivores [13][14][15] or the influence of viruses [16]. Recently, hypotheses have emerged that suggest a change in the structure of phytoplankton due to non-static predator-prey dynamics [17,18].…”