Thermal ecotypes of amphi-Atlantic algae. I. Algae of Arctic to cold-temperate distribution (Chaetomorpha melagonium, Devaleraea ramentacea andPhycodrys rubens)

Abstract

Three species of Arctic to cold-temperate amphi-Atlantic algae, all occurring also in the North Pacific, were tested for growth and/or survival at temperatures of -20 to 30 ~ When isolates from both western and eastern Atlantic shores were tested side-by-side, it was found that thermal ecotypes may occur in such Arctic algae. Chaetomorpha melagonium was the most eurythermal of the 3 species. Isolates of this alga were alike in temperature tolerance and growth rate but Icelandic plants were more sensitive to the lethal temperature of 25 ~ than were more southerly isolates from both east and west. With regard to Devaleraea ramentacea, one Canadian isolate grew extraordinarily well at -2 and 0 ~ and all tolerated temperatures 2-3 ~ higher than the lethal limit (18-20 ~ of isolates from Europe. Concerning Phycodrys rubens, both eastern and western isolates died at 20 ~ but European plants tolerated the lethal high temperature longerl were more sensitive to freezing, and attained more rapid growth at optimal temperatures. The intertidal species, C. melagonium and D. ramentacea, both survived freezing at -5 and -20~ at least for short time periods. C. melagonium was more susceptible than D. ramentacea to desiccation. Patterns of thermal tolerance may provide insight into the evolutionary history of seaweed species.

Physiological responses of the eulittoral macroalgaStictosiphonia hookeri(Rhodomelaceae, Rhodophyta) from Argentina and Chile: salinity, light and temperature acclimation

“…The capability of a single species to exist under a wide range of environmental parameters and over a broad geographical range has been reported for many macroalgae (Bolton, 1983;Karsten et al, 1994). The wide biogeographic occurrence of S. hookeri may be explained by the existence of temperature ecotypes with genetically fixed growth optima for specific temperatures in a specific habitat, as has been demonstrated for the brown alga Ectocarpus siliculosus (Bolton, 1983) and the green alga Chaetomorpha melagonium (Novaczeck et al, 1990). Although in this study ecotypic differentiation has been demonstrated in principle for S. hookeri, caution is necessary since only single isolates from each population were physiologically characterized.…”

Life strategy, ecophysiology and ecology of seaweeds in polar waters

“…The red alga Devaleraea ramentacea, which is distributed from the Arctic to the cold temperate North Atlantic region, grows at up to 10°C with an optimum at 0°C and exhibits an UST of 18-20°C and an LST of £-5°C. The ULG of this species is 8°C (Novaczek et al 1990;Bischoff and Wiencke 1993). Macrothalli of species with a prominent distribution in both, the Arctic and the cold-temperate region, grow at up to 15 or 20 (to 25)°C with optima between 5 and 15 (to 20)°C and exhibit USTs between 17 and 25 (to 26)°C.…”

“…In particular red and brown algal species from both polar regions exhibit temperature growth optima at 0-5°C or even at -2°C tom Dieck 1989, 1990;Novaczek et al 1990;Bischoff and Wiencke 1993;Bischoff-Bä smann and Wiencke 1996;Eggert and Wiencke 2000;McKamey and Amsler 2006). Some species like Georgiella confluens, Gigartina skottsbergii and Plocamium cartilagineum from the Antarctic grow only at 0°C, the lowest temperature tested, but not at 5°C (Bischoff-Bä smann and Wiencke 1996).…”

Thermal ecotypes of amphi-Atlantic algae. II. Cold-temperate species (Furcellaria lumbricalis andPolyides rotundus)

“…We have found ecotypic variation with respect to high-temperature tolerance in one pan-Arctic species (Devaleraea ramentacea) whereas 2 other species (Chaetomorpha melagonium and Phycodrys rubens) were more homogeneous (Novaczek et al, 1990). In the latter species, differences occurred in growth rates and in resistance to sublethal temperatures but not in absolute tolerance limits.…”

“…Algal species currently occupying both sides of the North Atlantic Ocean may have evolved in the Arctic or Atlantic; they may also have been introduced either from the North Pacific via the Arctic Ocean, or from the south Pacific via either the Caribbean or Tethys Seas (Novaczek et al, 1990). For some millions of years, thermal regimes of the eastern and western coasts of the North Atlantic have differed to a relatively large degree.…”