Environmental impact assessments are conducted to investigate whether human activities, like offshore wind energy production or sand extraction, are carried out in a sustainable way. Such assessments monitor the quality status of the environment by using biotic indices based on macrobenthos communities, which are considered as sensitive impact indicators due to their sessile and sedentary life. Up till now, the characterization of macrobenthic communities is based on morphological species identification and density and biomass measures. This method is time-consuming, labor-intensive and demands specific taxonomic knowledge. Faster and cost-effective determination methods such as DNA metabarcoding exist, but are not yet implemented in biotic indices.Currently, different primer pairs and different numbers of DNA and PCR replicates are used between labs. The genetic monitoring protocols across labs need to be standardized. Therefore, we designed a lab experiment to test five commonly used primer sets for macrobenthos, along with mixtures containing DNA of one to six DNA extractions per bulk macrobenthos sample. We also tested whether PCR replication is needed to obtain an accurate diversity estimate of the bulk samples. The resulting sequence data will be presented and serve as a basis for a standardized protocol applied to a pilot project targeting the impact of sand extraction in the North Sea. Traditional benthic identification (morphological analyses) and genetic identification (metabarcoding) are compared in terms of impact assessment. Therefore, Van Veen grabs were taken at the Thorntonbank in the Belgian part of the North Sea, covering a gradient in sand extraction intensity from zero (reference locations without extraction) to high intensity (daily extracted). Based on traditional morphological macrobenthos data and biotic indices we calculated a moderate, poor and bad status, respectively for the low, medium and high impact zones. Multivariate analysis further showed distinct groups between the high impact and reference samples, while the group of low impact samples was plotted lose to the reference samples, indicating that low intensity of sand extraction only has a limited effect on the macrobenthos community composition. In a following step we will investigate whether the same patterns can be found based on the DNA metabarcoding data. The comparison of the two methods, traditional benthic identification versus identification with metabarcoding, will be presented. |
