Biology Reference
In-Depth Information
abundance and distribution on the southern half of the western Antarctic Peninsula
describe a drop off in both species richness and biomass as one moves south from
Anvers Island (DeLaca and Lipps
1976
; Moe and DeLaca
1976
; Barnes and
Brockington
2003
; Bowden
2005
). Moe and DeLaca (
1976
) hypothesized that the
decreases in biomass and diversity in more southerly sites are largely due to
increases in annual ice cover. This relative decrease in biomass and coverage is
not unique to the southern Antarctic Peninsula since the same qualitative patterns
are described at other locations of similar latitude throughout most of the coast of
Antarctica (e.g., Zaneveld
1966
; Dhargalkar et al.
1988
; Kirkwood and Burton
1988
; Johnston et al.
2007
). However, even at these locations seaweeds can
dominate their communities. For example in East Antarctica, Irving et al. (
2005
)
reported that
Himantothallus grandifolius
covered approximately 80% of the bot-
tom at 12 m depth at two sites with the red seaweed,
Palmaria decipiens
, covering
nearly all the remaining substrate and in another area Johnston et al. (
2007
) reported
80-90% cover of
Desmarestia
sp. and
P. decipiens
at 6 m depth and approximately
80% cover of
H. grandifolius
at 12 m.
In the southern-most Antarctic seaweed habitats in the Ross Sea, communities
dominated by the frondose red seaweeds
Iridaea cordata
and
Phyllophora
antarctica
and the crustose coralline alga
Phymatolithon foecundum
have been
studied at Terra Nova Bay (74
,40
0
S; reviewed by Cattaneo-Vietti et al.
2000
;
Cormaci et al.
2000
) and in McMurdo Sound (77
40-50
0
S Miller and Pearse
1991
).
I. cordata
is more abundant in the 2-10 m depth range with densities up to
4,000 individuals m
2
and wet biomass levels up to 3.5 kg m
2
(Cattaneo-Vietti
et al.
2000
).
P. antarctica
dominates from 10 to 20 m depth with densities up to
10,000 individuals m
2
, wet biomass levels up to 1.6 kg m
2
, and percent cover up
to 90% of the benthos (Miller and Pearse
1991
; Cattaneo-Vietti et al.
2000
).
P. foecundum
includes several coralline alga species previously reported from the
Ross Sea (Alongi et al.
2002
) and occurs to depths of 70 m (Cormaci et al.
2000
). In
McMurdo Sound, it is present at most sites which have been observed by divers
whereas the foliose red algae occur at only a minority of locations (Miller and
Pearse
1991
; Amsler, personal observations). Both
P. foecundum
(Miller and
Pearse
1991
) and
I. cordata
(R. Robbins, personal communication) occur at Cape
Armitage in McMurdo Sound, which is the southern-most point in the world where
open ocean occurs over waters shallow enough to support seaweeds.
In the Arctic, several studies have documented seaweed communities growing
on boulders as well as smaller rock and shell hard substrates in the Alaskan
Beaufort Sea. These communities are dominated by the kelp
Laminaria solidungula
along with lesser numbers of the kelps
Saccharina latissima
and
Alaria esculenta
,
six species of foliose red seaweeds, and crustose coralline red algae (Dunton et al.
1982
; Busdosh et al.
1983
). Wet biomass values for the kelps range from means of
0.067 kg m
2
where only 10-25% of the bottom is covered by rock to 0.26 kg m
2
where rock covers
25% of the bottom (Dunton et al.
1982
). Kelp densities are
higher in summer than winter, with maximum densities of 6-30 individuals m
2
in
patches with high percentages of rock (Busdosh et al.
1983
). The total mean wet
biomass of red seaweeds is approximately 0.12 kg m
2
>
(Dunton et al.
1982
).
