The ecology of temperate salt-marsh fucoids. I. Occurrence and distribution of Ascophyllum nodosum ecads

The distribution of several free-living Ascophyllum nodosum ecads, including scorpioides and mackaii, in a temperate salt marsh is described. Morphological characterization of these ecads by the presence or absence of air bladders and reproductive receptacles, and size and shape of fronds, indicated that several free-living forms occur throughout the marsh. Plants resembling the ecad mackaii were more closely associated with exposed areas along the low-tide regions, while scorpioides-type ecads prevailed on the Spartina alterniflora-dominated marsh banks and flats in the middle and upper intertidal regions of the marsh. Maximum biomass of ecads occurred during the spring months in the absence of S. alterniflora, whereas minimum ecad biomass was associated with maximum S. alterniflora densities in the late summer and fall months. Morphological differentiation of dwarf-type ecads was related to environmental components other than exposure to low and/or fluctuating salinities.This research was suported by research grant AG-375 from the National Science Foundation and, in part, by the State University of New York Research Foundation and the Energy Research and Development Administration (ERDA).