The coast of the southeastern United States appears barren of seaweeds, but
in fact it supports a great diversity of them. In an early account of the sea-
weeds of the region Harvey (1852) noted that the comparable coast of Europe
had more kinds of seaweeds. He attributed the lower diversity here to the preva-
lence of sandy shores, as contrasted with the rocky coast of Europe. With hun-
dreds of miles of open, sandy beaches, the coast appeared to Harvey as it appears
to others: a region mostly devoid of suitable habitats for seaweeds. Investiga-
tions going back over 100 years have shown, however, that the waters between
Cape Hatteras and Cape Canaveral have a rich and interesting flora of more than
300 seaweed species, even though on some of its shores, particularly the open
beaches, seaweeds are few in number. The increase in our knowledge of the flora
is reflected graphically in figure 1, which indicates an initial flurry of activity
in the mid-nineteenth century, a period of inactivity, and then a steady increase
in knowledge through most of the present century, beginning with W. D. Hoyt's
notable publication in 1920.
The diversity of seaweeds reflects to some degree the diversity of habitats in
the region. Because of the system of barrier islands that fringe the coast and en-
close the shallow-water sounds, there are actually many more miles of shore
than the distance between the two capes defining the region suggests. Natural
rocky shores are almost nonexistent, but in many places jetties, seawalls, groins,
bridge supports, and other semipermanent hard structures have been erected
that may support algal growth (Hay and Sutherland 1988). Furthermore, large
expanses of sheltered, intertidal, and shallow subtidal wetlands lie protected
inside barrier islands. Seaweeds are often plentiful in such habitats; they are
anchored to shells, worm tubes, or other animal remains, and they grow on or
tangled among the marsh grasses and subtidal flowering plants that cover exten-
sive areas in the sounds. These shallow sounds produce large quantities of some
seaweeds-enough Gracilaria, for instance, to support an agar industry during
World War II. In addition, there are areas on the continental shelf offshore where
sedimentary rocks emerge through the mantle of sandy sediment to provide a
habitat within reach of sunlight that supports a substantial growth of seaweeds.
The seaweeds in the region are of great importance to their marine communi-
ties because they provide much of the three-dimensional structure. Along with
the vascular plants of the estuaries and the phytoplankton, the seaweeds are the
source of the primary production which fuels the abundant populations of her-
bivores, carnivores, omnivores, detritivores, commensals, and parasites in these
The geographic extent of the flora covered in this work corresponds with the
warm temperate waters of the southeastern United States (Searles 1984a). The
greatest diversity of seaweeds in this region occurs in North Carolina between
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