Dyrafjorður is a fjord in the northern part of Vestfirðir peninsula (NW-Iceland) that was crossed with a new road in 1991. In 1985, or a few years before the road and bridge construction commenced, there was an extensive ecological survey of invertebrates in the littoral zone and the bottom of the fjord. A later study was carried out in 2006–2007, which followed the same methodology as that used in the 1985 survey. Diversity and similarity indices were calculated between samples taken at the bottom of the fjord in 1985 and those taken in 2007. The similarity between the two stations on mudflats was 43 and 52% and in the littoral zone the similarity was 62–66%. The diversity on the bottom was very high in both surveys: H´=3.3–4.3. The diversity was lower in the littoral zone in 2006 and showed a higher variation between stations: H´=1.9–3.3. Overall, the results suggest that the road building had a limited impact on the ecology of the fjord, with the exception of those stations close to the bridge.

NW - Iceland, Dyrafjordur, Benthic fauna, Littoral zone, Road crossing, Diversity, Similarity.