Fucoid Macroalgae Have Distinct Physiological Mechanisms to Face Emersion and Submersion Periods in Their Southern Limit of Distribution

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.

Decline of a North American rocky intertidal foundation species linked to extreme dry, downslope Santa Ana winds

“…During SAW events occurring during low tide periods, Silvetia is often observed exhibiting severe drying out with fronds turning crispy. Desiccation stress is known to affect various physiological processes and conditions in rockweeds and other fucoids, including oxidative damage (Martins et al, 2021), reduced net photosynthesis, survival, and growth (Dethier et al, 2005), increased susceptibility to loss from wave action (Haring et al, 2002), and limited recruitment success (Dudgeon and Petraitis, 2001). Over time, these effects are likely to cause population declines, as observed at our monitoring sites.…”

Metabolic Adjustment of High Intertidal Alga Pelvetia canaliculata to the Tidal Cycle Includes Oscillations of Soluble Carbohydrates, Phlorotannins, and Citric Acid Content

“…Considerable changes of thallus moisture make any measurements of its physiological or biochemical parameters calculated on the fresh weight (FW) basis inadequate, as it is frequently conducted for other algae or vascular plants. In our study, we calculated all the parameters per dry weight, while FW-based calculations were used in several earlier studies of intertidal seaweeds (e.g., [ 7 , 9 ]), which hampers data comparison.…”

“…Adaptive responses of P. canaliculata to such a complicated environment are expected to require systematic rearrangements of all key physiological processes according to the phase of the tidal cycle. However, the physiological and biochemical mechanisms allowing this alga to tolerate such conditions are still largely unknown, as very few studies of intertidal seaweeds focus on Pelvetia [ 6 , 7 ]. These works and the studies of the mid and low intertidal fucoids ( Fucus vesiculosus , F. serratus , Ascophyllum nodosum ) suggest that fluctuations of physiological parameters and biochemical composition induced by the tidal cycle include changes in photosynthetic performance and pigment content [ 7 , 8 , 9 ], nutrient uptake [ 10 ], reactive oxygen species metabolism [ 7 , 11 ], osmolyte accumulation [ 1 ], and secondary metabolism [ 12 ].…”

“…However, the physiological and biochemical mechanisms allowing this alga to tolerate such conditions are still largely unknown, as very few studies of intertidal seaweeds focus on Pelvetia [ 6 , 7 ]. These works and the studies of the mid and low intertidal fucoids ( Fucus vesiculosus , F. serratus , Ascophyllum nodosum ) suggest that fluctuations of physiological parameters and biochemical composition induced by the tidal cycle include changes in photosynthetic performance and pigment content [ 7 , 8 , 9 ], nutrient uptake [ 10 ], reactive oxygen species metabolism [ 7 , 11 ], osmolyte accumulation [ 1 ], and secondary metabolism [ 12 ]. Moreover, intertidal fucoids were shown to use an adaptive strategy similar to CAM-photosynthesis, storing CO 2 in the form of organic acids during submersion and then consuming it in the Calvin cycle during the first hours of air exposure [ 13 , 14 ].…”

Concise review of the macroalgal species Pelvetia canaliculata (Linnaeus) Decaisne & Thuret

“…In situ, Martins et al (2021) reported up to 60% higher chlorophyll and carotenoid contents in P. canaliculata when collected at low tide, with the xanthophyll cycle constituting an important photoprotective mechanisms in this species (De Martino et al 1997;Harker et al 1999) (see "Light"). Moreover, a de-epoxidation of the xanthophyll cycle (i.e.…”