Patterns of fucoid reproductive biomass allocation

Abstract

The reproductive biomass allocation patterns (i.e. total reproductive effort) for eight perennial Northwest Atlantic fucoid algae (Ascophyllum nodosum, A. nodosum ecad scorpioides, Fucus distichus ssp. anceps, F. d. distichus, F. d. edentatus, F. d. evanescens, F. spiralis and F. vesiculosus) are compared from a variety of open coastal and estuarine sites. Three major spatial patterns of total reproductive effort were evident along a strong open coastal-estuarine gradient: (1) estuarine enhancement (e.g. A. nodosum and F. d. evanescens); (2) open coastal enhancement (e.g. F. spiralis); and (3) pronounced localized differences. Several plants from high energy environments (e.g. extreme wave action and strong tidal currents) were stunted and had reduced total reproductive effort, while contrasting patterns were evident for sheltered populations. Ascophyllum from exposed open coastal sites was heavily colonized by the obligate epiphyte, red alga Polysiphonia lanosa, with epiphyte density being significantly correlated with the host's total reproductive effort. Except for the salt marsh ecad scorpioides of A. nodosum, which had sporadic and reduced patterns of total reproductive effort (X = 0·4%) vs. its attached “progenitor” A. nodosum (X = 53% or 132 times higher), each fucoid taxa exhibited a pattern of high reproductive biomass allocation (X = 52–62%). The uniformity of total reproductive effort within the F. distichus complex (52–62%) is surprising as its four subspecies exhibit unique distributional patterns. Several spatial and genotypic patterns (i.e. between taxa) are discussed in terms of varying physiological tolerances, recruitment ecologies, selection, and competition for resources.