Abstract
During high tide, macroalgae are submersed, facing adequate environmental conditions, however, at low tide, these species can be exposed to high UV radiation and desiccation, leading to an overproduction of reactive oxygen species, causing oxidative stress. Since intertidal organisms present differential sensitivity to abiotic fluctuations, this study aimed to evaluate the physiological responses [photosynthetic pigments, hydrogen peroxide (H2O2), lipid peroxidation (LP), and thiols and proline] of three macroalgae, from different intertidal levels, towards tidal regimes. Samples of Pelvetia canaliculata, Ascophyllum nodosum, and Fucus serratus were collected from beaches located on the southern limit of distribution in periods of potential stress (Summer and Spring), under low and high tide. The photosynthetic pigments of P. canaliculata and F. serratus were generally higher during low tide, and the oxidative damage evidenced by H2O2 and LP increased in the Summer, while A. nodosum showed greater oxidative damage in the Spring. While thiol content did not change, proline levels were species- and tidal-specific among sampling dates. P. canaliculata presented higher resilience to unfavorable conditions, while F. serratus was the most sensitive species. The physiological responses analyzed were species-specific, pointing to the high susceptibility of low intertidal organisms to expected extreme climatic events.
Highlights
Climate change can exert a significant role in coastal and marine ecosystems, affecting their structure and functioning
Fucus serratus exhibited the highest chlorophyll amount (Figure 1a) at low and high tides in August 2017, being 60% and 100% higher than those observed for P. canaliculata and A. nodosum, respectively
In the last sampling date (August 2018), the levels of chlorophyll of F. serratus and P. canaliculata were 130% and 60% higher at low tide than those of A. nodosum, respectively
Summary
Climate change can exert a significant role in coastal and marine ecosystems, affecting their structure and functioning. Intertidal macroalgae, as sessile organisms, are periodically subjected to UV radiation and high temperatures, due to desiccation during emersion, followed by submersion, where they face homeostasis-promoting conditions. As a consequence of extended desiccation, the efficiency of the photosystems I and II is disturbed, negatively affecting the photosynthetic rate [3]. These physiological disturbances disrupt the redox homeostasis by an overproduction of reactive oxygen species (ROS), that comprise different chemical species, including molecular [hydrogen peroxide (H2O2) and singlet oxygen (1O2)] and radical [superoxide anion (O2.-) and hydroxyl radical (OH.)] forms [2,4]. Lipid peroxidation (LP) can occur, causing damage to the membranes and the photosynthetic apparatus, in addition to promoting the degradation of nucleic acids and proteins [2,4]
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