Combined effect of high light and high salinity on the regulation of photosynthesis in three diatom species belonging to the main growth forms of intertidal flat inhabiting microphytobenthos

Abstract

International audienceThe strong biological production of estuarine intertidal flats is mainly supported by benthic diatoms in temperate areas. Their photosynthetic productivity is largely driven by changes in light intensity and temperature at the surface of sediment flats during emersion. The impact of an increase in salinity of the upper-layer sediment pore-water during emersion, which is often coupled with high light (HL), has been less studied. Furthermore, benthic diatoms show several growth forms which inhabit specific sediment types where the pore-water salinity can differentially vary due to the degree of cohesion of sediment grains. So far, no study explored if the main growth forms of benthic diatoms (i.e. epipelon, epipsammon and tychoplankton) show different photophysiological response to a combine high salinity-HL stress. Based on field monitoring, we compared the photophysiology (photosynthetic efficiency and photoprotection) of three representatives of the main growth forms during a short high salinity coupled with a moderate HL stress and stable optimal temperature, i.e. experimental conditions reproducing Spring environmental conditions in intertidal flats by the Atlantic French coast. Our results show that all growth forms reacted to HL exposure alone, as expected. While the epipelon representative was relatively insensitive to high salinity alone and combined with HL, the tychoplankton representative was highly sensitive to both, and the epipsammon representative was sensitive mainly to the stress combination. These specific responses fitted well with i) their natural habitat (i.e. more or less cohesive sediment) for which light climate and changes in salinity are different, ii) their growth form (i.e. motile, immotile or amphibious) which determines their probability to be confronted to a combined high salinity-HL stress. Hence, the negative effect of high salinity on photosynthetic efficiency of benthic diatoms appears to be mostly restricted to epipsammon and tychoplankton, and in field conditions, its effect probably remains negligible compared to HL stress

Contrasting NPQ dynamics and xanthophyll cycling in a motile and a non‐motile intertidal benthic diatom

“…In contrast, an epipelic species, Seminavis robusta, shows a less dynamic NPQ, despite concerted de novo synthesis of both Dtx molecules and LHCX proteins. Our findings add to the physiological underpinning of the differential response of motile and non-motile diatom species Juneau et al 2015) and of benthic diatom communities in sediment Pniewski et al 2015;Cartaxana et al 2016b) to their environment.…”

Photosystem II repair in marine diatoms with contrasting photophysiologies

“…An increasing number of reports suggest that diatom/microalgal interspecies differences in NPQ are involved in the differential colonization of marine habitats based on the light climate combined or not with other environmental factors including nutrients, temperature, and salinity (Strzepek and Harrison 2004;Lavaud et al 2007;Dimier et al 2007;Kropuenske et al 2009;Bailleul et al 2010;Mills et al 2010;Petrou et al 2011;van de Poll et al 2011;Wu et al 2012;Lavaud and Lepetit 2013;Barnett et al 2015;Juneau et al 2015). Induction of NPQ nonetheless can impose opportunity costs upon microalgal productivity, since a sustained NPQ that persists after a downward shift in irradiance can lower achieved productivity at the new, lower light level (Raven 2011).…”

Growth and potential purification ability of Nitzschia sp. benthic diatoms in sea cucumber aquaculture wastewater

“…Benthic diatom growth is restricted by various factors, including ecological and nutritional factors (Viçose, Porta, Viera, Fernández‐Palacios, & Izquierdo, ; Sui et al., ; Juneau, Barnett, Méléder, Dupuy, & Lavaud, ) . In addition, the salinity of seawater affects diatomaceous osmotic pressure and nutrient absorption (Juneau et al., ). In this study, the growth of Nitzschia sp.…”