Samples were collected at eight different points of the wetland during November 2008. Due to the characteristics of the sediment in the sediment traps (≤0.5 m depth, viscous and thick sludge-like sediment), samples were taken from the surface with a plastic bucket and transferred to a plastic container for their transport. Sampling in the ponds was performed with an Ekman grab from an inflatable boat. Samples were collected on the 4th (the first and the third sediment traps, Pond 1 and Pond 10) and 17th (Pond 3, Pond 8 and the well at the end of the system) of November 2008. The samples taken from the first and the third sediment traps are labelled St1 and St3 respectively. The samples from the ponds are labelled with the pond number and sample nr e.g. P1-1 and P1-2, P3, P8 and P10 and the well at the outlet is labelled W. The sample P1-1 was collected in the centre of the second part of pond 1 and the sample P1-2 was collected at the outflow of pond 1. The other pond water samples were collected around the centre of the ponds. Each sample consisted of several grab samples.
Each sample was sieved (2 mm mesh size) and large elements (rocks, branches, etc.) were removed. The sieve was rinsed with porewater from each sample and collected in the same plastic bottle. The sample was homogenized with manual mixing (shaking and swirling during 30–50 s) and centrifuged during 10 min at 3000 RPM. The supernatant was collected as porewater. It was filtered (0.45 μm Ø filters) and stored in 50 ml Falcon tubes at −20 °C. The sediment was collected in plastic containers, weighed and stored at −20 °C until the toxicity tests were performed to kill infaunal species and preserve samples.