Page 72 - Alderney Regional Environmental Assessment of Renewable Energy: Environmental Report

Alderney Regional Environmental Assessment of Renewable Energy:
Environmental Report
5.1.1.2 Intertidal ecology
Alderney’s coastline consists of a variety of rocky shores, pebble and sandy shorelines and cliff
tops. The high energy marine environment does not favour the deposition of fine-grain
sediments and the intertidal substratum recorded comprises of bedrock, cobbles, boulders,
pebbles and sand (see also Marine Geomorphology Section 4.1 and Terrestrial Ecology
Section 5.7).
A series of intertidal surveys have been conducted around Alderney by Alderney Wildlife Trust
Enterprise (AWTE) between 2010 and 2012 (AWTE, 2011; 2012 a,b; 2013 a,b,c,d,e,f). In
general these survey areas are focussed on five main locations (see Figure 12); Hanaine Bay,
south coast of Alderney, Longis Bay, Brinchetais Ledge and Houmet Herbé. The intertidal
ecology of these areas is described in more detail below. A full list of the intertidal biotopes
recorded around Alderney is provided in Table B3 in Appendix B and is shown in Figure 12.
Hanaine Bay
Hanaine Bay is located along the west coast of Alderney, adjacent to the Swinge tidal stream
and to the south of Fort Clonque and Clonque Bay (Figure 12). The coastline consists of a
variety of rocky shore areas, pebbly beaches with small sandy pockets and cliff tops. An
intertidal habitat biotope survey (AWTE, 2013a) and intertidal phase II fixed photography
monitoring survey (AWTE, 2013f) were undertaken in the summer of 2012. In general, the
Hanaine Bay survey area comprised of three substrate types; bedrock, boulders and sands.
The upper and mid shoreline height regions comprised of large proportions of bedrock, with the
lower shoreline height region consisting of smaller proportions of boulders and sands.
In total 23 intertidal biotopes were recorded during the biotope habitat survey, with the most
predominant biotopes recorded identified as stable bedrock with boulders and rocky shorelines.
Characterising species within these biotopes were primarily seaweeds or barnacles which can
tolerate strong physical factors such as fast flowing tidal conditions, wave action and exposure.
The upper shoreline comprised of biotopes that represented moderate energy types (such as
LR.MLR.BF.PelB), lichen types (such as LR.FLR.Lic.YG) and also the ephemeral macroalgae
biotope, LR.FLR.Eph.Ent. These biotopes represent low ecological status and are commonly
associated with this shoreline height region. In addition, the seaweed biotope
LR.MLR.BF.FspiB was recorded within this shoreline height. This biotope is assigned
moderate ecological status, which is based on this biotope sustaining high proportions of
marine invertebrate species (AWTE, 2012; 2013f).
The mid shoreline height region largely represented high or moderate energy types, such as
the high energy barnacle mosaic LR.HLR.MusB.SemSem. This included the moderate
ecological status biotope LR.MLR.BF.Fser.R, characterised by Fucus spiralis. This biotope is
also regarded as moderately important due to this biotope sustaining high proportions of
marine invertebrate species (AWTE, 2012). In addition, the invasive macroalgae species
Sargassum muticum was also recorded as a rock-pool biotope, within this shoreline height
(AWTE, 2013f).
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