| Bfn Conclusions mastic asphalt | |
|---|---|
| Context | Bfn Building for Nature project |
| Type | Outcome |
| Decompositie type | IOR |
Conclusions of field experiment at Yerseke
The field experiment at Yerseke was set up with the aim to answer the following research question: Which substrate facilitates both the highest biodiversity and coverage in flora and fauna under equal intertidal environmental conditions at the end of the monitored time period (11 months)?
The total coverage (%) between the different substrates after 11 months showed an increase for all, but both mastic asphalt and Elastocoast (average coverage of respectively 13 and 23%) have a significantly lower coverage than the other substrates (average coverage of 83-89%). Total coverage on mastic asphalt substrate was the lowest of all substrates and on cockle shells the highest.
Data on species composition after 11 months on the different substrates indicated that mastic asphalt and Elastocoast had less of the Ulva sp. compared to the other substrates. Especially Elastocoast had a relatively high presence of Austrominius modestus (New Zealand acorn barnacle) compared to the other substrates. Though differences between species composition of substrates were not significant, an MDS plot showed that cockle shells, oyster shells, small lava stone and large lava stone have a relatively high similarity in species composition and Elastocoast and mastic asphalt are more dissimilar. Especially large lava stone has a relatively high contribution of Fucus vesiculosis compared to the other substrates. Although there are no significant differences in the overall species composition between the different substrates after 11 months, there are indications that the different substrates are able to facilitate growth of different species. The highest species richness was found on large lava stone after 11 months. Richness of Elastocoast and mastic asphalt appeared to be lower on average. Large lava stone also had the highest Shannon-diversity, which significantly differed from that of Elastocoast and cockle shells. This is likely due to lower richness and low relative abundance of the species present on Elastocoast and cockle shells respectively.
These results lead to the conclusion that with respect to species coverage especially small lava stone and cockle shells are most promising as a substrate. With regards to species diversity there are no significant differences in species community composition; however large lava stone has shown to be able to facilitate the highest species richness and diversity, whereas cockles and Elastocoast were able to facilitate a lower diversity (Vergouwen et al. 2017).
Conclusions of dyke monitoring study at Zierikzee
In overall the observations on the dyke at Zierikzee match the ones at the tiles in Yerseke. In terms of algal cover the lava stones are colonised quicker and after nine months have a more extensive cover than the other substrates. Bare mastic asphalt took the longest to get colonised and was after nine months not completely colonised, while all the other surfaces reached nearly 100% cover on many of the depth strata. The oyster and cockle top-layers performed intermediately.
In terms of species composition, there were also a few marked differences. Again the bare mastic asphalt showed least diversity, at least in terms of algae. The large lava stones seemed to promote the highest diversity, although specifically the cockle shell top layer appeared to promote Fucus species. On the lava stones, the oyster shells and the bare asphalt, varies Ulvacea appeared to dominate (several Ulva species as well as Blidingia minima). These species are all very small and highly flexible, while members of the Fucus genus are much more rigid and structured. They can ultimately become ecosystem engineers themselves and provide shelter and foraging habitat for other species.
Curiously, the species richness for fauna was highest on the mastic asphalt. The composition of species differed markedly between the bare asphalt and the other top layers. On the other top layers (particularly small lava stones and cockles) the dominant species was identified as the native barnacle (Semibalanus balanoides) (Vergouwen et al. 2017).
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