. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 230 N. L. LOHRMANN ET AL. March April June July Aug Oct Dec Feb March Month Figure 4. Ascorbate contents, by month for ChonJnis erixpux (dark bars) and sicllum* (white bars I. When analyzed by mean monthly temperature, there were significant differences by temperature (P, ,;5 ) between species in a given month, and an asterisk indicates significant difference (P Mastocarpus stellatus Clioiulrifi crispus 39 ± 6 41 ± 8 59 ± 8 60 ± 4 40 ± 7 46 ± 8 22 ± 4 16 ± 4 Data are means ± standard deviation. There were si
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 230 N. L. LOHRMANN ET AL. March April June July Aug Oct Dec Feb March Month Figure 4. Ascorbate contents, by month for ChonJnis erixpux (dark bars) and sicllum* (white bars I. When analyzed by mean monthly temperature, there were significant differences by temperature (P, ,;5 ) between species in a given month, and an asterisk indicates significant difference (P Mastocarpus stellatus Clioiulrifi crispus 39 ± 6 41 ± 8 59 ± 8 60 ± 4 40 ± 7 46 ± 8 22 ± 4 16 ± 4 Data are means ± standard deviation. There were significant differences in means by month (P, ,6 < ) but not by species (P, ,„ = ). and there was no significant interaction (P, ,„ = ); all differences between months are significant (each u posteriori P < ) except for between March and September (<; posteriori P = ); n = 6. 1993). Such increases are interpreted as a means of com- pensating for the effects of low temperatures on enzyme activities. Increased photosynthetic capacity in winter may also have been influenced by greater nitrogen availability in this season (Topinka and Robbins, 1976). Previous reports that M. stellatus is relatively more re- sistant to freezing damage to the photosynthetic apparatus were based upon freezing regimens imposed experimentally in a laboratory (Dudgeon et ai. 1989. 1990, 1995). It is possible that conditions in the field around the time of our collections were not stressful enough for species to show differences in winter tolerance. Alternatively, since our measurements of photosynthetic capacity were performed in humidified air, whereas macroalgal photosynthesis is typi- cally measured from submerged thalli, it may be that winter rates of photosynthesis for C. crispus and M. stellatus are more similar in air than they are in water. Intertidul algae may perform a significant proportion of total daily photo- synthesis during exposure to air at low
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