Photosynthetic traits of freshwater lichens are consistent with the submersion conditions of their habitat

Abstract

OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. This is an author-deposited version published in : http://oatao.univ-toulouse.fr/ Eprints ID : 15742 Abstract -In this study, we compared the photosynthetic performance of epilithic freshwater lichens on siliceous stream rock submerged for: more than 9 (hyper-), 6-9 (meso-) or 3-6 months (sub-hydrophilic lichens). In the dry state, neither variable fluorescence nor respiration activity could be detected. In the wet state, rates of dark respiration (O 2 uptake and CO 2 production for immerged and in-air samples) were in the lower range of that reported for non-aquatic lichens. With 200 (under water) or 500 mmol.m , aerial), photosynthesis increased in sub-but became negative in hyper-hydrophilic species. After hydration, dry samples increased photosystem II (PSII) efficiency, which reached near steady state in < 6-7 min. Hyper-hydrophilic lichen took longer than sub-hydrophilic species. A long period of desiccation (4 months) had a negative effect on subsequent PSII photochemistry of hyper-but not of sub-hydrophilic hydrated lichens. When thalli were allowed to dehydrate, all types of lichens lost PSII activity after about 15-20 min. Deactivation was faster in the hyper-than in the sub-hydrophilic species. The metabolic traits presented here are thus consistent with the ecological amplitude of the freshwater lichens studied.

Differential responses to salt concentrations of lichen photobiont strains isolated from lichens occurring in different littoral zones

“…Lichens and plants from shaded habitats generally have lower compensation points and display lower rates of photosynthesis under high irradiance than sun-adapted lichens and plants (Loach 1967;Green et al 1997;Picotto & Tretiach 2010). Coste et al (2016) found a relationship between the length of time that freshwater lichen species are submerged and the decay of photosynthesis activity under high irradiation. In their study, the subhydrophylic lichen Verrucaria praetermissa increased CO 2 assimilation notably when it was exposed to high PPFD (2000 mmol m -2 s -1 , aerial conditions), whereas it became negative in the hyperhydrophilous lichen Verrucaria funckii and in Ionaspis lacustris and Porpidia hydrophila, two mesohydrophilous species.…”

National Ordinary High Water Mark Field Delineation Manual for Rivers and Streams : Interim Version

“…Inundation causes the thallus of most lichens to break down or to be invaded by nonsymbiotic fungi, but survival is prolonged with lower water temperatures (Marsh and Timoney 2005; Sammut and Erskine 2013). Aquatic and amphibious lichens have physiological and anatomical adaptations optimized for permanent or periodic submergence (Thüs et al 2014;Coste et al 2016). Water, therefore, creates a tenuous balance between lichen growth, and survival contributes to their strong zonation pattern.…”

Coastal Lichens

“…Recently, water lichens are becoming the objects of ecological and physiological research. Coste et al (2016) conducted a comparative study of photosynthetic performance of epilithic lichens depending on different times of flooding. Obtained results of this study showed slightly slower activation and higher sensitivity of PSII to desiccation that may be important factors to explain the confinement of the most freshwater-related species to habitats that provide sufficiently long hydration periods (Coste et al 2016).…”