| Abstract: | A number of boreal-subarctic crustose corallines were kept in natural seawater tanks at temperatures ranging from 0 to 19 C and, using fluorescent lamps at light intensities, ranging from 7 to 750 lux with periods of 8 and 14 hr/day. The resultant growth rates as a function of temperature and light are presented and discussed in relation to the ecology of the plants. All of the Lithothamnieae studied had growth maxima at temperatures from 9 to 15 C. Growth in these species showed little light dependence below 4–6 C, but had a strong light dependence at higher temperatures. The one Lithophyllum species examined gave a flatter growth-temperature curve than the Lithothamnieae and showed little light dependence. The effects of temperature variation, salinity, and current on growth rates were also examined and are discussed. It was found to be especially important in studying growth rates of crustose corallines to allow time for growth stabilization following temperature change. In general, growth was found to exhibit a hysteresis effect, increased rates with the raising of temperatures 5–10 C and decreased rates with lowering temperatures. |
