The Role of Kelp in the Marine Environment - National Parks ...

them provide lists of species from various phyla for Norwegian waters and record 238
taxa (including fish) from 58 plants examined with an average density of 8,000
individuals per laminarian. Both publications agree that amphipods and gastropods
were the most diverse and numerically dominant groups present but both these
sources underestimate the numbers of polychaete species (see Healy and McGrath
(1998) for a more extensive listing of polychaetes). Birkett et al. (1998) provide
figures for classes and higher taxa and these total to ca. 1,260, some 173 of which are
polychaetes. These same authors list three species of ctenophores; however, as
ctenophores are exclusively planktonic, they cannot be regarded as living in/on (or
dependant upon) kelp forests. Edwards (op. cit.), working in Bantry and Dunmanus
Bays in the south west Ireland, noted that decreases in diversity and depths to which
plants could grow were related to levels of suspended solids. Open water forests
could live in deeper depths and had greater numbers of associated species whereas
inshore kelp communities, living at the ends of bays where freshwater inflow and
wave action increased turbidity, were restricted to ca. < 10 m depth and had few
species. He also noted that suspension feeders dominated these inshore communities,
a feeding group that would benefit from higher levels of suspended material. Moore
(1973) had earlier identified turbidity as an important ecological factor regulating
growth of laminarians.
In contrast, Steneck et al. (2004) observed that kelp forests off the Gulf of Maine are
naturally low in species diversity with only 15 taxa recorded. There are no records of
sponges, coelenterates, polychaetes, cirripeds, isopods, bryozoans or tunicates, all of
which are highly associated with kelp forests in Ireland. Their absence in western
Atlantic kelp forests is hard to understand and pressure from urchin grazing cannot be
used to explain this.
Jones (1973), working off the north east coast of Britain where water quality is
seriously compromised by pollution, found that holdfast communities were less
diverse than at open water sites with ca. 45% of the species complement being absent
from these polluted sites. Species that were rare at the open water sites were absent
from the polluted site, and no new species were recorded at the polluted sites.
However, Abbott and Perkins (1977) and Perkins et al. (1978) report that successive
sampling of laminarian holdfasts over a 6 year period between 1971 and 1976
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