Effects of irradiance and temperature on the Mediterranean red algae Eupogo
don spinellus and Eupogodon planus were tested. Growth of both species was
saturated at an irradiance of 10-20 mu mol m(-2) s(-1), which is in accorda
nce with their sublittoral habitat. Eupogodon spinellus and E. planus survi
ved permanently at temperatures between 8 and 30 degrees C. The temperature
optimum for growth was 25 degrees C with suboptimal growth occurring at (1
0-)15 and 30 degrees C in both species. At their collection locality (Corsi
ca), potential monthly growth yields would be highest in summer and in wint
er would be only about 20% of the maximum. Reproductive requirements could
be determined only in E. planus. Gametophytes reproduced both in long and i
n short days but only at 20 degrees C. Tetrasporophytes reproduced at 15-20
degrees C but only in short days. Geographic distribution boundaries are n
ot set by growth or survival limits. However, the reproductive requirements
of E, planus did account for its restricted distribution in the Mediterran
ean and on the Canary Islands.