<p>Left: The sampled regions in the Dutch Delta and the Wadden Sea (shaded area), with the islands Sylt (north) and Texel (south). Above right: Sampling locations around the islands of Sylt and Texel in the Wadden Sea. Below right: Sampling locations in the Dutch Delta. For exact coordinates see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0193354#pone.0193354.s003" target="_blank">S1 Table</a>.</p