The Davis Strait - DCE - Nationalt Center for Miljø og Energi

183 macroalgal species (excl. the bluegreen algae, Cyanophyta) are listed for
Greenland according to the compiled checklist from 1976 (Pedersen 1976).
Due to taxonomic and nomenclatural changes the number presently equals
137 species; 37 red algal species, 66 brown and 37 green. Within the assessment
area 34 red algae, 51 brown and 33 green have been recorded.
The brown algae Laminaria solidungula, Punctaria glacialis, Platysiphon vertillatus
and the red algae Haemescharia polygyna, Neodilsea integra, Devalerea ramentacea,
Turnerella pennyi and Pantoneura fabriciana are considered as Arctic
endemics (Wulff et al. 2009). Of these species L. solidungula, D. ramentacea, T.
pennyi and P. fabriciana are present in the assessment area.
On sea floors with soft sediment, as in some places in the fjords around
Nuuk, loose-lying macroalgae, or macroalgae attached to small stones and
shells, may occur. These drifting algae masses are often dominated by
Desmarestia aculeata and other filamentous brown algae. In areas of the fjords
with enriched waters the green algae Enteromorpha spp. may be substantial
(Christensen 1981).
In addition, in the shallow soft bottom areas of some of the inner branches of
the Nuuk fjord system, meadows of eelgrass cover the sea floor and reach
high abundances (Krause-Jensen et al. 2011).
Another interesting feature in the fjords of Nuuk is the sole registration of
the geniculate coralline red algae Corallina officinalis in Greenland
(Christensen 1975).
In proximity to Nuuk, in the assessment area, sea floor covered by coralline
red algae (Fig. 4.3.1) is observed (M. Blicher, pers. comm.). Both encrusting
coralline red algae on stones and the loose-lying, branched forms, rhodliths,
are present. The processes leading to rhodolith accumulations are poorly
understood, but the rhodoliths are most likely derived from branches breaking
off from branched encrusting coralline red algal species or developed as
branched, crusts overgrowing a pebble or a mussel/shell, which may act as
a nodule (Freiwald 1995).
Such areas dominated by encrusting coralline red algae as well as rhodoliths
are reported from a couple of other localities in Greenland; in the Disko
Fjord and close to Qaqortoq. The locality in Qaqortoq is of the same type as
those identified close to Nuuk, i.e. stony sea floor with encrusting coralline
red algae and rhodoliths intermixed (AM Mortensen, pers. comm.). In Disko
Fjord relatively large rhodoliths with diameters of up to 13 cm (Düwel &
Wegeberg 1990, Thormar 2006) are accumulated on a soft and muddy bottom.
The occurrence of coralline red algal dominated habitats seems to be closely
correlated to the presence and frequency of sea urchins. According to Bulleri
et al. (2002) grazing by sea urchins plays a fundamental role in establishing
and maintaining areas dominated by encrusting coralline red algae and
hence rhodoliths. The grazing down of foliose macroalgae by the sea urchins
leaves the calcite incrusted red algal species with available substratum and
optimal light conditions. Thereafter, as investigated in temperate regions,
the coralline red algae covering the available substratum may prevent recruitment
of erect macroalgae, maintaining the alternative habitat (Bulleri et
al. 2002).
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