Effects of the water sports on the underwater vegetation in the Orther Reede Bay
The Case study of Fehmarn Island within the Land-Sea-Act project explores various aspects of balancing tourism activities (including water sports) and nature conservation. On Fehmarn island one particular area where nature values are prevalent and water sports are popular is the Orther Bay. To study the impact of surfing activities on nature values macrophytes [an aquatic plant large enough to be seen by the naked eye] were examined.
The influence of water sports on macrophytes in the Orther Reede Bay was studied by comparing the vegetation coverage and thalli length of macrophytes between two surfing areas and one nature reserve area (Figure 1).
Figure 1: Areas of the Orther Reede Bay (Fehmarn) in which macrophytes where investigated
Therefore in July 2020 eight transects in Nature reserve area and Surfing area A and five transects in Surfing area B were investigated. The total coverage of macrophytes, the coverage and thalli length of the ecologically important macrophyte species in different water-depths (0,25 m, 0,5m, 0,75m, 1,0m and 1,5 m) where documented in transects with a minimum length of 200 m (Figure 2).
Figure 2: Transects on which the coverage and thalli length of macrophytes in the Orther Reede Bay (Fehmarn) where documented (A1–A5: Surfing area A; B1–B4: Surfing area B; C1–C4: Nature reserve area)
In the result between different areas hardly any noticeable difference in total coverage of macrophytes was found (Figure 3, Figure 4). The total coverage of macrophytes is a little higher in the nature reserve area than at the surfing areas and only at 0,5 m and 1,0 m water depth (Figure 3). A reason for that might be the occurrence of Zanichellia palustris in the natural reserve area which was hardly found in the two surfing areas (Figure 4).
Figure 3: Coverage of macrophytes in three different areas of the Orther Reede Bay (Fehmarn)
Figure 4: Coverage of different macrophyte species in three different areas of the Orther Reede Bay (Fehmarn)
The examination of the habitus length of different macrophyte species also indicates that there is not much difference between nature reserve area and surfing areas (Figure 5), for example, habitus length of Potamogeton pectinatus is about 20 cm longer in the nature reserve area than in the surfing areas.
Figure 5: Habitus length of different macrophyte species in three different areas of the Orther Reede Bay (Fehmarn)
Even if no major negative effect of surf sports on macrophytes in the Orther Reede Bay was found, still surfing and other watersports should be kept within tight limits. Figure 6 shows an unaffected area where macrophytes occur (left) and an entrance area for surfers where no macrophytes grow. If water sports and therefore entrance areas continue to increase in the Orther Reede Bay there is a risk that macrophytes could disappear in the shallow water areas.
Figure 6: Unaffected area (left) and entrance area for surfers (right)
The next step after the stocktaking in the Orther Bay will be the drafting of action plan in order to coordinate and balance water sports activities with nature conservation.
Figure 7: Study in the process
Read more on German case study Climate change adaptation and sustainable tourism here.
Prepared by Beate Burow (Stadt Fehmarn) /November 2020/