Benthic Communities at Horns Rev Before, During and After Con
Benthic Communities at Horns Rev Before, During and After Con
Benthic Communities at Horns Rev Before, During and After Con
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<strong>Horns</strong> <strong>Rev</strong>. <strong>Benthic</strong> communities Page 52<br />
In the splash zone of the monopiles, a dense cover of the filamentous green algae (Urospora<br />
penicilliformis) was only observed in spring 2003 whereas Cladophora was observed<br />
in rel<strong>at</strong>ively low coverage in autumn 2003 <strong>and</strong> autumn 2005. In 2004 <strong>and</strong> 2005, the<br />
veget<strong>at</strong>ion of filamentous algae was generally replaced by a distinct green/brown co<strong>at</strong>ing<br />
of microscopic green algae <strong>and</strong> di<strong>at</strong>oms.<br />
Just bene<strong>at</strong>h the surface to approxim<strong>at</strong>ely 2 metres below the sea surface, r<strong>at</strong>her dense<br />
m<strong>at</strong>s of the filamentous brown algae (Pilayella littoralis/Ectocarpus) were found. The<br />
coverage of Pilayella littoralis was especially high in 2003 <strong>and</strong> 2005 <strong>and</strong> this species was<br />
almost exclusively found in the spring surveys (Figure 3.12). Species of Ulva cl<strong>at</strong>hr<strong>at</strong>a<br />
<strong>and</strong> Ulva prolifera (Enteromorpha spp.) were rel<strong>at</strong>ively domin<strong>at</strong>ing in this zone with the<br />
highest coverage of these species being generally found in the autumn. The green algae<br />
(Ch<strong>at</strong>omorpha linum) <strong>and</strong> the red algae (Polysiphonia fibrillosa) were found <strong>at</strong> most turbine<br />
sites in 2005 with small tufts of the common red porphyra algae (Porphyra umbilicalis)<br />
being found <strong>at</strong> some turbine sites. The seaweeds (Petalonia fascia <strong>and</strong> Petalonia<br />
zosterifolia) were also typically found in this depth zone but in rel<strong>at</strong>ively low coverage.<br />
Veget<strong>at</strong>ion coverage declined with increasing depth, which was pronounced for the most<br />
abundant species, Pilayella littoralis/Ectocarpus <strong>and</strong> Ulva (Enteromorpha) (Figure 3.12),<br />
which were found 4-6 m below the sea surface. In 2005, Ulva lactuca was found 6-8 m<br />
below the sea surface. Petalonia fascia <strong>and</strong> Polysiphonia fibrillosa were occasionally<br />
found 4-6 m <strong>and</strong> 2-4 m below the sea surface.<br />
0-2 m<br />
2-4 m<br />
4-6 m<br />
6-8 m<br />
8-10 m<br />
Ectocarpus/Pilayella Coverage monopiles<br />
March 03<br />
Sept. 03<br />
March 04<br />
Sept. 04<br />
March 05<br />
Sept. 05<br />
0 5 10<br />
Rel<strong>at</strong>ive coverage<br />
15 20<br />
0-2 m<br />
2-4 m<br />
4-6 m<br />
6-8 m<br />
8-10 m<br />
Ulva spp. Coverage monopiles<br />
March 03<br />
Sept. 03<br />
March 04<br />
Sept. 04<br />
March 05<br />
Sept. 05<br />
0 5 10<br />
Rel<strong>at</strong>ive coverage<br />
15 20<br />
Figure 3.12.Depth distribution <strong>and</strong> mean rel<strong>at</strong>ive coverage of filamentous algae (Ectocarpus/Pilayella) <strong>and</strong><br />
Ulva spp. along transects <strong>at</strong> monopiles in 2003-2005.<br />
3.3.2. Epifauna<br />
The total number of species associ<strong>at</strong>ed with the hard bottom structures <strong>at</strong> <strong>Horns</strong> <strong>Rev</strong> has<br />
increased gradually from the first surveys in 2003 to the surveys in 2005.<br />
Of the 111 total invertebr<strong>at</strong>e species registered <strong>and</strong> observed during the monitoring of the<br />
hard bottom structures, only 37 species/taxons could be characteristically found as n<strong>at</strong>ive<br />
infauna or mobile fauna in the area before the establishment of the offshore wind farm <strong>at</strong><br />
<strong>Horns</strong> <strong>Rev</strong>. Only 14 species/taxons were not sampled or identified in the quantit<strong>at</strong>ive<br />
samples. Some of these species were occasionally <strong>and</strong> only observed by divers during the<br />
transect surveys (Appendix 2.1). It was mainly very mobile species such as crabs <strong>and</strong> larger<br />
species like the common whelk. Other very common species, such as the plumose<br />
Doc. No. 2572-03-005 rev. 4