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Trevor Gallant


M.Sc.: 1991 - 1993

Present occupation: Teacher at Kennebecasis Valley High School, Quispamsis, Canada

Thesis: Phosphorus and nitrogen nutrition, and carrageenan production in the red alga Chondrus crispus Stackhouse (Rhodophyceae, Gigartinales)

Trevor Gallant's Photograph Trevor Gallant sampling some Irish moss at Maces Bay, Bay of Fundy, Canada (photo: Thierry Chopin).

Abstract: The possible existence of a phenomenon in phosphorus (P) nutrition comparable to the "Neish effect" in nitrogen (N) nutrition (an inverse relation between seawater N enrichment and carrageenan content) was investigated. The temperate red alga Chondrus crispus was preconditioned for 17 days then cultured under varying enrichments of P (0, 3, 6, 10, 15 µM P/week) and constant N enrichment (53.5 µM N/week) for five weeks. Plants were later analyzed for tissue total P content, tissue total N content, and carrageenan content. Identical experiments were performed using C. crispus collected during the fall, winter, spring, and summer seasons. The procedure was repeated using materials collected during the following fall season, and cultured under conditions of constant P enrichment (6 µM P/week) and varying N enrichments (0, 3, 6, 10, 25 µM N/week).

In the fall (P) experiment, carrageenan content was the highest (53.12 ± 0.33 % DW (dry weight)), and tissue total P content was the lowest (1.71 ± 0.27 mg P/g DW) in plants which received no P enrichment. Carrageenan content was stable (46.15 ± 1.85 % DW) for plants given enrichments of 3 µM P/week and greater. Thus, a decrease in carrageenan content, concomitant with an increase in tissue total P content, was observed, but only at tissue total P levels below 2 mg P/g DW. As these levels were always higher than 2 mg P/g DW in winter, spring, and summer experiments, carrageenan content remained constant, within each season, at 46.25 ± 1.27, 43.10 ± 0.69, and 44.51 ± 0.59 % DW, respectively.

N enrichment of plants collected in the fall did not affect carrageenan content, which was stable at 49.26 ± 0.94 % DW. When these plants were compared with those from the previous fall experiment (6 µM P/week and 53.5 µM N/week), a slight increase in carrageenan content was noted. Thus, at sufficiently high concentration, N also decreased carrageenan content in C. crispus.