Temperature response of photosynthetic capacity and carboxylase activity in Arctic marine phytoplankton

Abstract

The temperature response of photosynthetic capacity was compared to that of 3 carboxylating enzymes in Arctic marine phytoplankton. Only the activity of ribulose-1.5-bisphosphate carboxylase (RuBPC) consistently exhibited an apparent activation energy equivalent to that of photosynthetic capacity. This is the first indication from field samples of phytoplankton that changes in the activity of RuBPC may be closely associated with changes in photosynthetic capacity. The maximum photosynthetic capacity attained by Arctic phytoplankton at a given in situ temperature appeared to increase from about 0.4 mg C mg Chl a-' h-' at -1.5 ' C to an apparently constant value of about 2.0 mg C mg Chl a-' h-' at temperatures equal to and greater than 0.0 "C.

Light and nutrient control of photosynthesis in natural phytoplankton populations from the Chukchi and Beaufort seas, Arctic Ocean

“…This is consistent with previous studies of the region (Carmack et al 2006;Tremblay et al 2008;Lee et al 2010), which suggested that P-E parameters in the ice-associated region of the Chukchi Sea vary primarily based on nutrients, because shade-adapted phytoplankton can utilize light at much lower levels than can their high-light adapted counterparts. However, our results do not as closely support the temperature-and light-control theory of some earlier studies of the region (Li et al 1984;Harrison and Platt 1986;Harrison and Cota 1991), hinting at the possibility that recent changes in sea ice and environmental conditions may be altering phytoplankton growth and photosynthesis in several fundamental and important ways, and/or that the data sets are not as comparable as we are assuming in this study (e.g., possibly because of biases in sampling location, timing, methodology, etc.). More work is needed to fully understand the effects of changing environmental conditions on P-E parameters of natural phytoplankton populations from this dynamic region.…”

“…This is contrary to what would be expected if temperatures controlled primary productivity through the regulation of enzymatic activity (Li et al 1984). Although the regression analysis does show that temperature was a key factor in the prediction of five of the eight parameters analyzed, we suggest that the importance of the temperature term was exaggerated because of its tendency toward co-variation with both light (positively correlated) and nutrient concentration (inversely correlated).…”

“…For example, NO 3 limitation reduces growth rates and photosynthetic rates, both of which are linked to the reduction in protein synthesis through a reduction in functional reaction centers (Falkowski 1992). Temperature is thought to be a key factor limiting primary production in the Arctic, because photosynthetic rates are influenced by the activity of specific enzymes, whose activity is reduced at low temperatures (Li et al 1984;Falkowski 1992;MorganKiss et al 2006).…”

“…However, it is unknown whether there are differences in acclimation between phytoplankton groups from different environments. Moreover, it is unknown how future changes in sea ice and climate may affect the physical marine environment and thus phytoplankton distributions, although it has been suggested that a surface freshening would favor communities dominated by smaller algal species (Li et al 2009). This has important implications for the entire food web as different taxa play different ecological and biogeochemical roles and link primary production to marine mammals, birds, fish, and benthic communities (Stirling 1997;Grebmeier et al 2006;Wassmann 2006).…”

Strategies of thermal adaptation by high‐latitude cyanobacteria

“…For example, cyanobacteria may adjust their photosynthetic apparatus in order to acclimate to the prevailing temperature. They tend to have decreased photosynthetic capacity (P max ) at low temperatures due to depressed activity of ribulose-1,5-bisphosphate carboxylase (Rubisco) (Li et al, 1984 ;Raven & Geider, 1988). Therefore, a potential adaptive strategy for polar cyanobacteria would be to decrease their concentrations of chlorophyll a and light harvesting pigments (Geider, 1987 ;Davison, 1991) while increasing the activity of Rubisco (Li & Morris, 1982).…”