Morpho-functional patterns and zonation of South Chilean seaweeds: the importance of photosynthetic and bio-optical traits

Abstract

We address the question of whether seaweed zonation can be characterized in terms of light absorption, pigmentation, photosynthetic parameters, photoinhibition, and thallus structure. Based on 32 seaweed species from the Pacific coast of southern Chile, intertidal assemblages exhibited higher light requirements for photosynthesis (E k ) and lower thallus light absorptances than subtidal algae. E k values were lower than the highest measured irradiances at the corresponding natural depths, suggesting that photosynthesis in these organisms could potentially occur at lower depths. During summer, 1% of photosynthetically active radiation (PAR) reached a depth of 23 m, while UV-B and UV-A wavelengths were completely attenuated at < 3 and 6 m, respectively. Overall, the photobiological adaptations were associated with depth, morphology, and taxonomic group. Photoinhibition was similar in algae from different depths, although recovery was higher in upper littoral algae than in infra-and sublittoral species. The characteristics conferring competitive abilities in light use and light stress tolerance were not, or only partially, related to the classical Littler form-function model. The filamentous and foliose forms were able to acclimate rapidly to changing light and physical stress in the supralittoral zone. For infralittoral kelps living in a highly dynamic environment, higher cross-sectional area and enhanced in vivo light absorption were coupled with morphological features (e.g. massive thallus) that are advantageous in withstanding e.g. water movement. By contrast, the rapid physiological adjustments that allow algae to endure solar stress (e.g. photochemical down-regulation) were strongly dependent on the position on the shore but not on gross morphology.

Seasonal variation in floating persistence of detached Durvillaea antarctica (Chamisso) Hariot thalli

“…Our data on the photosynthetic performance of D. antarctica are in agreement with those of G ó mez and Huovinen (2011) . This infralittoral kelp had low to moderate light requirements for photosynthesis, as reflected in the initial values for light saturation of the initial individuals (I k = 110 -185 μ mol photons m -2 s -1 ).…”

Latitudinal and seasonal effects on short-term acclimation of floating kelp species from the South-East Pacific

“…Although differences in morphology and tissue structure might affect physiological comparisons between different kelp species, previous studies had shown that small pieces of photosynthetically active tissues are suitable to determine physiological responses to environmental change, thus allowing for interspecific comparisons despite morpho-functional differences (e.g. Bischof et al, 1998;Connan et al, 2004;Rothäusler et al, 2011c;Gómez and Huovinen, 2011;Cruces et al, 2012).…”

Contrasting Responses of Marine and Freshwater Photosynthetic Organisms to UVB Radiation: A Meta-Analysis

“…Our results showed that foliose macroalgae exhibited the greatest improvement in their performance when UVB is reduced. Gómez and Huovinen (2011) described that foliose forms were able to acclimate rapidly to changing light. Therefore, their performance would be expected to improve rapidly when UVB was reduced, as showed in the present study.…”