Cell size trade‐offs govern light exploitation strategies in marine phytoplankton

Abstract

Marine phytoplankton show complex community structures and biogeographic distributions, the net results of physiological and ecological trade-offs of species responses to fluctuating, heterogeneous environments. We analysed photosynthesis, responses to variable light and macromolecular allocations across a size panel of marine centric diatoms. The diatoms have strong capacities to withstand and exploit fluctuating light, when compared with picophytoplankton. Within marine diatoms, small species show larger effective cross-sections for photochemistry, and fast metabolic repair of photosystem II after photoinactivation. In contrast, large diatoms show lower susceptibility to photoinactivation, and therefore incur lower costs to endure short-term exposures to high light, especially under conditions that limit metabolic rates. This size scaling of key photophysiological parameters thus helps explain the relative competitive advantages of larger versus smaller species under different environmental regimes, with implications for the function of the biogenic carbon pump. These results provide a mechanistic framework to explain and predict shifts in marine phytoplankton community size structure with changes in surface irradiance and mixed layer depth.

Size-fractionated phytoplankton biomass and production in the tropical Atlantic

“…However, variability in K d did not significantly influence the P/B of surface phytoplankton >2 mm, which typically have a higher package effect, lower susceptibility to photoinactivation and better photosynthetic performance in surface waters under high irradiance levels (Hashimoto and Shiomoto, 2002;Raven et al, 2005;Cermeño et al, 2005;Finkel et al, 2010). Therefore, the phytoplankton in this larger size class are likely to incur lower costs to endure exposures to high light, especially under conditions that limit metabolic rates (Key et al, 2010;Finkel et al, 2010).…”

Growth form defines physiological photoprotective capacity in intertidal benthic diatoms

“…Various morphological and physiological traits have been shown to define the ecological niches of phytoplankton species, including size, temperature response and resource acquisition and utilization traits. For example, in planktonic diatoms, which have a key role in marine primary production and biogeochemical cycling (Armbrust, 2009), pronounced species-specific differences in photosynthetic architecture and photophysiological strategies have been documented (for example, Dimier et al, 2007;Key et al, 2010;Schwaderer et al, 2011;Wu et al, 2012) and related to their in situ light environment (Strzepek and Harrison, 2004;Lavaud et al, 2007;Dimier et al, 2009;Petrou et al, 2011). A high capacity for physiological photoprotection is generally observed in highly fluctuating light climates and/or under on average high irradiances.…”

Scaling of growth rate and mortality with size and its consequence on size spectra of natural microphytoplankton assemblages in the East China Sea

“…In general, large phytoplankton exhibit a lower photosynthesis rate because of the package effect (Berner et al, 1989) and a lower nutrient uptake rate because of lower surface-to-volume ratio (Kiørboe, 1993). However, when light and nutrients are sufficient, large individuals could have competitive advantages over small individuals (Maguer et al, 2009) due to their low susceptibility to light damage and higher carbon-specific photosynthesis rates (Cermeño et al, 2005;Key et al, 2010).…”

“…This could stem from the following features possessed by the larger phytoplankton to overcome their geometric constraints: (1) in terms of nutrient acquisition, large phytoplankton show isometric scaling relationship between nutrient uptake rate and body size (Marañón et al, 2013); (2) in terms of photosynthesis, chl a content of phytoplankton scaled isometrically with body size (Marañón et al, 2007), and (3) the large phytoplankton exhibit higher carbon fixation to chl a ratio (Huete-Ortega et al, 2011). Although the large phytoplankton would exhibit the package effect (Berner et al, 1989), they would be less susceptible to light damage and photoinactivation, which is commonly observed in small phytoplankton (Key et al, 2010). The large phytoplankton could overcome constraints of the transportation network by increasing their vacuole size to elevate storage ability (Latasa et al, 2005;Stolte et al, 1994;Thingstad et al, 2005) and by attaining higher photosynthetic efficiency (Cermeño et al, 2005).…”