Physiological responses to environmental variation in intertidal red algae: does thallus morphology matter?

Abstract

Morphological variation within and among many species of algae show correlated life history traits. The trade-offs of life history traits among different morphs are presumed to be determined by morphology Form-function hypotheses also predict that algae of different morphological groups exhibit different tolerances to physiological stress, whereas algae within a morphological group respond similarly to stress. We tested this hypothesis by comparing photosynthetic and respiratory responses to variation in season, light, temperature, desiccation and freezing among the morphologically similar fronds of Chondrus crispus and Mastocarpus stellatus and the alternate stage crust of M stellatus. Physiological differences between fronds of the 2 species and crusts and fronds were consistent with their patterns of distribution and abundance in the intertidal zone. However, there was no clear relationship between algal morphology and physiological response to environmental variation These results suggest that among macroalgae the correlation between life history traits and morphology is not always causal. Rather, the link between life history traits and morphology is constrained by the extent to which physiological characteristics codetermme these features.

Fatty acid and sterol composition of gametophytes and sporophytes of <i>Chondrus crispus</i> (Gigartinaceae, Rhodophyta)

“…However, morphological similarity does not imply physiological or ecological similarity, as rapid growth, reproduction, environmental tolerance, resistance to predation and competition have been observed to differ between isomorphic life stages of macroalgae (Dixon, 1973;Hannach and Santelices, 1985;Juanes and Puente, 1993). Life history traits may be determined at the cellular level by differential allocation of metabolic energy among physiological processes (Dudgeon et al, 1995) Several studies demonstrated variability in ploidy ratios in natural populations of C. crispus, with dominance of haploid or diploid phases and a wide range of intermediate situations, due to physical environment or a differential reproductive and growth capacities (Bhattacharya, 1985;Chopin et al, 1988;Lazo et al, 1989;Mathieson, 1989;Fernández and Menéndez, 1991a, b;Chopin and Floc'h, 1992;Scrosati et al, 1994;Dudgeon et al, 1995;Lindgren and Aberg, 1996), which could reflect different physiological adaptations between the two generations. In addition, in culture, slight differences in growth between both generations were also observed (Chen and Taylor, 1980;Guiry, 1979;McLachlan et al, 1988;Tasende and Fraga, 1999).…”

“…Seaweeds with life stages that differ in ploidy level might express recessive traits during haploid stages, or express other differences, that would allow these stages to vary in adaptability under different environmental conditions. Heteromorphic seaweeds are well know to have variable chemical traits, such as different carrageenan types and chlorophyll a concentrations, associated with their morphological differences (Dudgeon et al, 1995).…”

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

“…When subtidal algae (which are not exposed to high solar radiation) are included, other photobiological capacities, such as low light requirements for photosynthesis, enhanced lightabsorption capacity, and positive metabolic carbon balance, are paramount and set the metabolic depth limits for growth (Markager & Sand-Jensen 1992, Gó-mez et al 1997, Binzer & Sand-Jensen 2002. Clearly, some of the morpho-functional adaptations of algae have developed to cope with variable light availability and can confer advantages when coping with other environmental factors such as desiccation and temperature (Dudgeon et al 1995).…”

“…A rapid recovery of photosynthesis in species from shallower depths would be a general response explained by an increased time-use efficiency of algae exposed for longer periods to enhanced environmental stress (e.g. high solar radiation, desiccation, and temperature; Dring & Brown 1982, Dudgeon et al 1995, Skene 2004.…”

“…These authors indicated that photosynthesis decreased as a function of desiccation stress in all species; however, an effective recovery of photosynthesis after reimmersion was observed only in algae from the upper littoral zones. Further studies focusing on the lightabsorption characteristics, such as optimal thallus optics and light-harvesting capacity, put an emphasis on the internal features of the algae underlying their light adaptations and light-stress tolerance (Ramus 1978, Dring 1981, Lüning & Dring 1985, Henley 1993, Markager 1993, Enriquez et al 1994, Dudgeon et al 1995, Franklin & Forster 1997, Bischof et al 1998. Moreover, morphological characteristics such as canopy structure (e.g.…”