Photosynthesis and net primary productivity in three Antarctic diatoms: possible significance for their distribution in the Antarctic marine ecosystem

Abstract

Photosynthesis and net primary productivity were measured in 3 Antarctic diatoms, Fragilariopsis cylindrus, Pseudo-nitzschia subcurvata and Chaetoceros sp., exposed to rapid changes in temperature and salinity representing a range of conditions found during a seasonal cycle. Measured differences in fluorescence-derived photosynthetic activity and oxygen evolution suggested that some alternative electron cycling activity was present under high irradiances. F. cylindrus displayed the highest rates of relative electron transport and net primary productivity under all salinity and temperature combinations and showed adaptive traits towards the sea-icelike environment. P. subcurvata displayed a preference for low saline conditions where production rates were greatest. However, there was evidence of photosynthetic sensitivity to the lowest temperatures and highest salinities, suggesting a lack of adaptation for dealing with sea-ice-like conditions. Chaetoceros sp. showed high plasticity, acclimating well to all conditions but performing best under pelagic conditions. The study shows species-specific sensitivities to environmental change, highlighting photosynthetic capacity as a potentially important mechanism in ecological niche adaptation. When these data were modelled over different seasons, integrated daily net primary production was greatest under summer pelagic conditions. The findings from this study support the general observations of light control and seasonal development of net primary productivity and species succession in the Antarctic marine ecosystem. KEY WORDS: Net primary productivity · Antarctic diatoms · Ecological niche adaptation · Chl a fluorescence Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 437: [27][28][29][30][31][32][33][34][35][36][37][38][39][40] 2011 display high photoprotective capabilities. However, it is unknown whether differences in photoprotective capacity among Antarctic diatom species can be linked with specific niche environments.Antarctic marine phytoplankton are exposed to large changes in ecosystem conditions during an annual cycle (Fig. 1). In winter, phytoplankton are rapidly incorporated into the sea ice matrix where they are confined to tiny brine channels (salinities up to 145) at freezing temperatures . Initially incoming solar irradiance is very high in the developing sea ice, as a result of being constrained close to the surface, but as the ice thickens, irradiance declines, often to levels of less than 1% surface irradiance (Palmisano et al. 1987). In the austral spring, the ice begins to melt, and the microalgae are washed out of the brine channels into a surface lens of hyposaline water. The meltwater environment, characterised by low salinities (typically below 33), a stable water column and shallow mixed layer, forms an ideal environment for the development of phytoplankton blooms (Dierssen et al. 2002). In summer, the Southern Ocean mixes phytoplankton from the surface waters to the deep, delivering ...

Effect of continental shelf canyons on phytoplankton biomass and community composition along the western Antarctic Peninsula

“…However, photophysiology, nutrient uptake rates, and grazing preferences are all taxon-specific, which can affect the community composition of phytoplankton, particularly in highly variable environments such as the Southern Ocean (e.g. Petrou & Ralph 2011). Furthermore, iron limitation, light limitation, and temperature stress may disproportionately affect diatoms (e.g.…”

Southern Ocean phytoplankton physiology in a changing climate

“…Only a few however, have linked a species physiology and photosynthetic plasticity to its observed distribution and abundance (Kropuenske et al, 2009Petrou et al, 2011a;Petrou and Ralph, 2011). Comparison of the photoacclimation strategies of F. cylindrus and P. antarctica provides an excellent example of how the photoprotective capacity of these two important SO species can be linked with their ecological niche occupancy.…”

Phenotypic Plasticity of Southern Ocean Diatoms: Key to Success in the Sea Ice Habitat?

“…Consequently, diatoms experience rapid fluctuations in physical and chemical conditions associated with the transition from sea ice to meltwater and pelagic habitats (Figure 1) [8]. This highly variable habitat has driven the evolutionary adaptation of extremophile diatoms, which are capable of growing and photosynthesising under conditions that lie at the ends of temperature, pH and salinity tolerance scales [8,9]. …”