Contribution of stormwater ponds for road runoff to aquatic biodiversity

Licentiate thesis, 2017

The increased recognition that roads may impair the aquatic environment and ecosystems has led to a shift from conventional drainage systems toward blue-green solutions such as stormwater ponds. Research on blue-green stormwater solutions has until now mainly focused on water quantity and quality. The goals of this study are to evaluate the influence of environmental factors on the biological community composition in stormwater ponds receiving road runoff and to determine to which extent these green infrastructures can promote and maintain pond dwelling organisms. Biological community composition was investigated in 16 stormwater ponds along the highways E6 and E18 in the counties of Oslo, Akershus and Østfold of Norway. Multivariate statistical methods were used to explore the relationship between the biological community composition and the pollutants in water and sediments, as well as physical factors. Redundancy analysis combined with forward selection showed that the most important water quality and physical variables determining the variation in the biological community composition were pond size, distance to the closest pond from study pond, annual average daily traffic, concentrations of metals, chloride, dissolved oxygen, hydrocarbons and phosphorus. Most taxa were negatively correlated with metals. The results indicate that, compared with smaller ponds, larger ponds are better for supporting aquatic biodiversity due to a more heterogeneous environment and ability to dilute pollutants. Also, the presence of other ponds in the vicinity of the stormwater ponds would facilitate the movement of invertebrates between ponds through increased connectivity. The redundancy analysis showed that different taxa exhibited different responses to pollutants in the sediments, indicating potential differences in pollution tolerance among organisms. Therefore, the factors that may affect pollutant bioavailability in the sediments should be analysed. In addition, since different species, even within one family, responded differently to the same pollutant, it is important to identify organisms to the species level.