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

74
trated at the pycnocline, ecological damage from an oil spill on plankton
communities can be assumed to be less severe (Söderkvist et al. 2006).
4.3 Macrophytes
Susse Wegeberg (AU)
Shorelines with a rich primary production are of high ecological significance.
The littoral and sublittoral canopy of macroalgae is important for
higher trophic levels of the food web by providing substrate for sessile animals,
shelter from predation, protection against wave action, currents and
desiccation or directly as a food source (Bertness et al. 1999, Lippert et al.
2001). Because of strong biological interactions in rocky intertidal and kelp
forest communities, cascades of delayed, indirect impacts of oil contamination
(e.g., biogenic habitat loss and changes in prey-predator balances due to
species specific mortality) may be much more severe than a direct impact of
oil contamination as seen after the Exxon Valdez spill (Peterson et al. 2003).
However, some shorelines are highly impacted by natural parameters such
as wave action and ice scouring, and such shorelines will therefore naturally
sustain a relatively lower production or may appear as barren grounds. So,
to identify important or critical areas a robust baseline knowledge on littoral
and sublittoral ecology is essential.
Investigation of the marine benthic flora in the assessment area is scarce and
has mainly been conducted as floristic studies. Marine macroalgae were collected
on different expeditions to Greenland during the 19 th century, and
were identified and described by Rosenvinge (1893, 1898). In addition,
Christensen (1975, 1981) worked in the Nuuk area and an investigation of
marine ecology in the littoral zone (ECOTIDE) has been initiated in Kobberfjord
close to Nuuk. A check-list and distribution of the marine algae of
Greenland for the east and west coast separately was compiled by Pedersen
(1976) (Table 1). Moreover, a recent study assessed the extension and production
of kelp belts along Greenland’s West coast, from Nuuk to north of
Qaanaaq (Krause-Jensen et al. 2011)
4.3.1 General context
The marine macroalgae are found along shorelines with hard and stable
substratum, such as stones, boulders and rocky coast. The vegetation is distinctly
divided in zones, which are most pronounced in areas with high tidal
amplitudes. Some species grow above the high-water mark, the supralittoral
zone, where sea water reaches them as sea water dust, spray or by wave action.
In the littoral zone the vegetation is alternately immersed and emersed,
and characterised by fucoid species. The majority of the macroalgal species,
however, grows below the low water mark within water depths with sufficient
light. In the Arctic, the length of the ice-free period is an important controller
of the light reaching the sea floor and the depth range of the kelp belt
increases from north towards south along Greenland’s coast parallel to the
increase in length of the ice-free period (Krause-Jensen et al. 2011). In north
Greenland, a relatively dense macroalgal flora can be found down to water
depths of about 20 m (Krause-Jensen et al. 2011), while they occur deeper
than 50 m in South Greenland and around Disko (Wegeberg et al. 2005,
Hansen et al. 2012a).