Temperature, light, and photoperiod responses of some Northeast American and West European endemic rhodophytes in relation to their geographic distribution

Abstract

ABSTRACT:The relationship between distributional boundaries and temperature responses of some Northeast American and West European endemic and amphiatlantic rhodophytes was experimentally determined under varying regimes of temperature, light, and daylength. Potentially critical temperatures, derived from open ocean surface summer and winter isotherms, were inferred from distributional data for each of these algae. On the basis of the distributional data the algae fall within the limits of three phytogeographic groups: (1) the Northeast American tropical-to-temperate group; (2) the warm-temperate Mediterranean Atlantic group; and (3) the amphiatlantic tropical-to-warm temperate group. Experimental evidence suggests that the species belonging to the northeast American tropical-to-temperate group (Grinnellia americana, Lomentaria baHeyana, and Agardhiella subulata} have their northern boundaries determined by a minimum summer temperature high enough for sufficient growth and/or reproduction. The possible restriction of 2 species (G. americana and L. baileyana) to the tropical margins may be caused by summer lethal temperatures (between 30 and 35 °C) or because the gradual disintegration of the upright thalli at high temperatures (> 30 °C) promotes an ephemeral existence of these algae towards their southern boundaries. Each of the species have a rapid growth and reproductive potential between 15-30 °C with a broad optimum between 20-30 °C. The lower limit of survival of each species was at least 0 °C (tested in short days only). Growth and reproduction data imply that the restrictive distribution of these algae to the Americas may be due to the fact that for adequate growth and/or reproduction water temperatures must exceed 20 °C. At temperatures _--< 15 °C reproduction and growth are timited, and the amphiatlantic distribution through Iceland would not be permitted. On the basis of experimental evidence, the species belonging to the warm-temperate Mediterranean Atlantic group (Halurus equisetifolius}, Callophyllis laciniata, and Hypoglossum woodwardii}, have their northern boundaries determined by winter lethal temperatures. Growth of H. equisetifolius proceeded from 10-25 °C, that of C. laciniata and H. woodwardii from 5-25 °C, in each case with a narrow range for optimal growth at ca. 15 °C. Tetrasporelings of H. woodwardii showed limited survival at 0 °C for up to 4 d. For all members of the group tetrasporangia occurred from 10-20 °C.

Temperature responses of tropical to warm temperateCladophora species in relation to their distribution in the North Atlantic Ocean

“…Light damage at low temperatures is a well documented phenomenon in higher plants (e.g. see review in Larcher, 1981) and has also been documented for several green and red algae (Cambridge et al, 1984;Yarish et al, 1984Yarish et al, , 1986. In these locations, lethal conditions may occur in early spring rather than in mid winter.…”

“…C. prolifera is not recorded from the central Caribbean. The absence of C. prolifera from the central islands in the Caribbean is hard to explain but it is a similar pattern to the tropicaltemperate N. E. America red alga, Grinellia americana (Yarish et al, 1984). It is perhaps due to the high summer temperatures, as the 29 ~ summer isotherms surround the islands and correspond to locally higher temperatures which would be lethal.…”

“…Studies on other seaweeds have shown that temperature responses (in combination with light and photoperiodic responses) determined in the laboratory can explain distribution patterns along latitudinal gradients (McLachlan & Bird, 1984;Yarish et al, 1984Yarish et al, , 1986; and other studies reviewed in van den Hoek, 1982a, c). Hutchins (1947) proposed that temperature could act as a limiting factor at the poleward and equatorward ends of the distribution range of a marine organism as follows:…”

Temperature responses of some North AtlanticCladophora species (Chlorophyceae) in relation to their geographic distribution

“…Growth responses under constant temperature conditions ranging from 5 °-30 °C were measured on 5 or 10 replicates at short (8:16 h; light:dark) and long (16:8 h) day conditions, photon flux density 40 ~t E m -2 s -1, using cloned material from tip cuttings, except for C. hutchinMae for which sporelings were used. For general methods and equipment for cultivation, see Yarish et al (1984).…”

Life history regulation and phenology of the red algaBonnemaisonia hamifera

“…Cultures were kept in Provasoli's enriched seawater medium with 10 % of the normal P and N concentration (see Lfining, 1980Lfining, , 1981. General methods and equipment for culturing have been described by Breeman and ten Hoopen (1981) and Yarish et al (1984). Procedures to quantify reproduction of the tetrasporophyte were similar to those described previously for Rhodochorton purpureum .…”