The role of beach nourishment in alterin phosphorus availability in dutch sand dune ecosystems

Abstract

Beach-nourishment is becoming more popular as a method to fight coastal erosion (Speybroeck et al, 2004a). A new form of beach-nourishment, the mega-nourishment is being trialled in the Netherlands as an alternate form of nourishment using the power of nature to defend against coastal erosion (De Zandmotor, 2014). However no research has of yet analysed the role of beach-nourishments in potentially altering the P-availability in a sand dune ecosystem. This paper aims to compare the effects of a mega-nourishment and traditional-nourishment site against a reference site (non-nourishment) to see analyse the effects of differing nourishment techniques on sand dune ecosystem P-availability. Extensive field work and lab analysis of sediment samples collected from sandpits and sand traps revealed the three following major findings: 1) Both mega- and traditional-nourishments can become a potential new source of P when compared to non-nourishment site. At the beach on the non-nourishment site only 0.07 µmol g/ P more Tot-P was found when compared to the established dunes, however at the mega-nourishment and traditional-nourishment site this figure was 9.37 µmol g/ P and 2.54 µmol g/ P more. Secondly it was also found that through the mean of aeolian transportation, high concentrations of P, predominantly in the form of Fe-P, were being transported to the established dunes beach-nourishment sites. Thirdly it was found that the concentration of Fe-P at beach-nourishment sites was strongly related to the proportion of fine grain sediment in the sample, meaning that nourishment samples containing a higher proportion of fine-grain sediment are more likely to alter P-availability at sand dune ecosystems in the future. More research is required to ascertain how this change in P-availability could affect the sand dune ecosystem over time.