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Patricia Marquis


Honours Thesis: 1994

Present occupation: Veterinarian in Florida, U.S.A.

Thesis: Seasonal dynamics of phosphorus and nitrogen contents in the brown alga Ascophyllum nodosum (L.) Le Jolis and its associated species Polysiphonia lanosa (L.) Tandy and Pilayella littoralis (L.) Kjellman from Maces Bay, Bay of Fundy, Canada

Patricia Marquis PhotographPatricia Marquis doing some tissue sampling at the seaweed lab at UNBSJ (photo: UNB).

Abstract: The seasonal variations of tissue total phosphorus and nitrogen contents in Ascophyllum nodosum, sampled at the two extremes of its vertical distributions on the shore at Maces Bay, Bay of Fundy, Canada, were measured at fifteen intervals from May 1992 to December 1993. Concurrently, seawater phosphorus (PO43-) and nitrogen (NH4+ + NO33- + NO22-) concentrations, and tissue total phosphorus and nitrogen contents in two associated species of A. nodosum, Polysiphonia lanosa and Pilayella littoralis, were also determined.

Phosphorus and nitrogen levels varied both spatially (along the plant's axis) and temporally (with season) in A. nodosum. Along the thallus, apical parts contained more phosphorus and nitrogen than intermediate and basal ones. These variations of nutrients may be related to variations in the physiology and metabolism of the different parts of the plant. Seasonal variations, particularly in apical parts, were correlated with those in seawater. A trend was observed where upper parts of low shore plants had higher phosphorus content than those higher on the shore for the first part of the study.

The tissue total phosphorus and nitrogen contents of the associated species were consistently higher than those of A. nodosum, favouring the hypothesis of a parasitic relationship.