GROWTH-RESPONSES OF CAULERPA-TAXIFOLIA (ULVOPHYCEAE, CHLOROPHYTA) FROM THE SOUTH-AFRICAN AQUARIST TRADE - A POTENTIAL INVASIVE OF SOUTH-AFRICAN COASTAL WATERS

Caulerpa taxifolia (Vahl) C. Agardh is an invasive marine alga in the northern Mediterranean Sea where it poses a serious threat to indigeno us fauna and flora. Caulerpa taxifolia obtained through the aquarist t rade in South Africa was grown under controlled temperature and irradi ance conditions. Two separate univariate studies were performed: i) Te mperature treatments of 15 degrees, 20 degrees, 25 degrees and 30 degr ees C, all at 90 mu mol photons.m(-2).s(-1) irradiance and ii) irradia nce treatments of 20, 75 and 130 mu mol photons.m(-2).s(-1), all at 25 degrees C. The optimum temperature for maximal stolen and assimilator extension was 25 degrees C; the alga showed growth as high as 30 degr ees C with slight growth occurring as low as 15 degrees C. Growth of C . taxifolia was similar over the range of irradiance values studied. M aximum mean stolen and assimilator extension were recorded at an irrad iance of 75 mu mol photons.m(-2).s(-1). Caulerpa taxifolia commonly av ailable in the South African aquarist trade was shown to have a wide t emperature tolerance range, well within the range experienced by the e ast coast of the country.