ROLE OF CHLOROPHYLL AND CARBOHYDRATE CONTENTS IN SURVIVAL OF POSIDONIA-OCEANICA CUTTINGS TRANSPLANTED TO DIFFERENT DEPTHS

Cuttings of the marine phanerogam Posidonia oceanica (L.) Delile were collected and transplanted in January 1991 at four stations of differe nt depths between 5 and 20 m in the underwater reserve at Monaco (1 ha in area). From January to July, samples of the transplants were colle cted to study the effect of depth on survival and on chlorophyll and c arbohydrate concentrations. In the leaves, chlorophyll concentrations were significantly lower (1.00 mg g(-1) dry wt) in cuttings taken from 5 m depth than in cuttings taken from 20 m (1.99 mg g(-1)). Transplan tation of cuttings from 5 to 20 m or from 20 to 8 m did not significan tly change the chlorophyll concentration in leaves for a period of 6 m o after transplantation. Cutting and transplantation result in stress, as indicated by a decrease in pigment concentration without change of depth. However, the carbohydrate concentration in rhizomes from 5 m ( 32 mg g(-1) dry wt), is significantly higher than in material from 20 m (17 mg g(-1)). Cuttings transplanted from 5 to 20 m lost most of the ir carbohydrate reserves (reaching a minimum of 2.5 mg g(-1) in May); cuttings transplanted from 20 to 8 m maintained higher reserves (with a minimum of 20 mg g(-1) in June). This may explain why material trans planted from 5 to 20 m exhibited only 52% survival, while material tra nsplanted from 20 to 8 m displayed 80 to 92% survival. Material taken from populations adapted to low light at 20 m is probably more resista nt to transplantation stress, particularly when replanted at a higher light intensity in shallow water.