Page 74 - Alderney Regional Environmental Assessment of Renewable Energy: Environmental Report

Alderney Regional Environmental Assessment of Renewable Energy:
Environmental Report
muticum. Biotopes with moderate importance include those found in the littoral caves or
overhangs of the survey area including, LR.FLR.CvOv.AudCla and LR.FLR.CvOv.FaCr. Both
biotopes are rare within the British Isles and are under threat from coastal defence building
works (AWTE, 2012a). Miscellaneous and unidentified habitats such as artificial sea walls and
rock exposures were also identified, predominately around the Cachelier Pier (AWTE, 2012a).
Longis Bay and Associated Areas
Longis Bay is located along the south eastern side of Alderney and is a low lying sheltered bay
surrounded by a variety of rocky shore and cliff top areas (Figure 12). An intertidal habitat
biotope survey, undertaken in 2010, was completed for Longis Bay and Frying Pan Bay plus
the wider coastline from the southern side of the Houmet Herbé fort, extending across all
intertidal areas down towards the island’s refuse site (known locally as the Impo) (AWTE,
2011). An intertidal Phase II fixed photography monitoring survey, undertaken in 2011, was
also completed for Longis Bay and the adjacent Frying Pan Bay only (AWTE, 2012b).
A total number of 49 intertidal biotopes were recorded across the total survey area (AWTE,
2011). The most predominant biotopes recorded within the overall survey area were identified
as stable bedrock and rocky shorelines which exhibit high to moderate exposure levels,
extending from Houmet Herbé to the start of Longis Bay and also further ranging from Frying
Pan Bay to the Impo site area (AWTE, 2011).
Both Longis Bay and Frying Pan Bay survey areas predominately comprised of bedrock and
boulder substrates, with Longis Bay also consisting of coarse sand substrates. Within the
Longis Bay survey area, a total number of 13 associated biotopes were identified, which
consisted of moderately exposed to sheltered biotopes, such as LR.MLR.BF.FspiB and
LR.LLR.F.Fserr.X characterised by seaweeds. A locally important eelgrass biotope (biotope
code: SS.SMp SSgr.Zmar) was also recorded at the mouth of Longis Bay. The biotope is
uncommon within the British Isles and often regarded as being of high or moderately high
ecological significance. However, the biotope identified in this survey portrayed some physical
damage and sustained smaller proportions of marine life when compared to other known Z.
marina beds. Therefore the ecological status for this biotope is described as moderate (AWTE,
2011). A total number of 13 biotopes were also identified within the Frying Pan Bay survey
area, comprising of more highly exposed biotope types such as LR.HLR.FR.Him and
LR.HLR.FR.Mas. Both Bays also consisted of mixed substrate types, lichen types and the
cave biotope, LR.FLR.CvOv.AudCla. The cave biotope is regarded as uncommon, with a
moderate ecological status across the local, regional and national level (AWTE, 2012b).
A total number of 70 marine algal species and four lichen species were recorded across the full
survey site (AWTE, 2011). This included 9 Chlorophyta, 17 Phaeophyta and 44 Rhodophyta
algae species respectively. The majority of the algae and lichen identified were either regarded
as widespread or common status found throughout the Channel Islands and British Isles.
However, a small number of important species were identified within the overall survey area.
This included the UK nationally rare red seaweed Gracilaria bursa-pastoris and the brown
seaweed peacock’s tail, Padina pavonica (Sanderson, 1996; Wood, 2007).
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