Response of intertidal benthic microalgal biofilms to a coupled light–temperature stress: evidence for latitudinal adaptation along the Atlantic coast of Southern Europe

Abstract

Although estuarine microphytobenthos (MPB) is frequently exposed to excessive light and temperature conditions, little is known on their interactive effects on MPB primary productivity. Laboratory and in situ experiments were combined to investigate the short-term joint effects of high light (HL) and high temperature (37 °C versus 27 °C) on the operating efficiency of photoprotective processes [vertical migration versus non-photochemical quenching (NPQ)] exhibited by natural benthic diatom communities from two intertidal flats in France (FR) and Portugal (PT). A clear latitudinal pattern was observed, with PT biofilms being more resistant to HL stress, regardless the effect of temperature, and displaying a lower relative contribution of vertical migration to photoprotection and a stronger NPQ in situ. However, higher temperature leads to comparable effects, with photoinhibition increasing to about three times (i.e. from 3% to 10% and from 8% to 22% in PT and FR sites respectively). By using a number of methodological novelties in MPB research (lipid peroxidation quantification, Lhcx proteins immunodetection), this study brings a physiological basis to the previously reported depression of MPB photosynthetic productivity in summer. They emphasize the joint role of temperature and light in limiting, at least transiently (i.e. during emersion), MPB photosynthetic activity in situ.

Differential photosynthetic responses of marine planktonic and benthic diatoms to ultraviolet radiation under various temperature regimes

“…also showed sensitivity to temperature change (Sobrino and Neale, 2007). The repair rates (r) and the ratio of r to k further demonstrated that the planktonic species had a relatively lower optimal temperature in response to UVR, with the highest r : k and lowest UV inhibition at 25 • C. In contrast, in the benthic species r and r : k increased steadily and reached relatively stable values at the highest temperature, and this coincided with lower UV inhibition, implying that although acclimated in laboratory conditions for weeks, this species still had an active mechanism to respond to high temperature and UVR, as might occur in its natural niche environment (Laviale et al, 2015).…”

“…These findings imply that temperature is a key factor that mediates the response of diatoms to UVR, while different species have developed distinct mechanisms in response to their particular niche environments (Laviale et al, 2015).…”

“…The planktonic diatom, however, only performed better under short-term elevated temperature. This suggests that the benthic species could have broader adaptability to cope with the highly varied temperature environment they frequently experience (Laviale et al, 2015).…”

“…The photochemical damage is mainly determined by the intensity and spectrum of light (Heraud and Beardall, 2000) and is temperature insensitive, while the repair process is driven by a series of enzyme-catalyzed reactions and is thus potentially sensitive to temperature changes (Melis, 1999). Previous studies revealed that high temperature alleviated UV inhibition of PSII in green algae (Wong et al, 2015), while it interactively decreased photosynthetic activity in microphytobenthos under excessive PAR conditions (Laviale et al, 2015).…”

Physiological responses of coastal and oceanic diatoms to diurnal fluctuations in seawater carbonate chemistry under two CO<sub>2</sub> concentrations

“…This striking contrast of physiological traits in coastal and oceanic diatoms suggests that the ability to cope with fluctuating carbonate chemistry may play a role in influencing the geographic distributions of species under OA conditions. It is possible that this ability, together with the abilities to cope with nutrient (Irwin et al, 2006), light (Lavaud et al, 2007;Lavaud and Lepetit, 2013;Laviale et al, 2015), and predation pressure (Irigoien et al, 2005), will determine the spatial distribution patterns of species in the future oceans. However, phytoplankton are known to exhibit species-specific response to environmental factors (including OA, fluctuating carbonate chemistry, etc.…”