MBACI sampling of an episodic disturbance: Stormwater effects on algal epifauna

Potential effects of storm-water run-off on assemblages of mobile invertebrates

“…Overall, as in some previous studies (Maxon et al 1997, Nipper et al 1998, Roberts et al 2007), we did not find evidence to support the model that stormwater run-off has strong, clear negative effects on invertebrate assemblages as suggested by laboratory tests (Skinner et al 1999, Carr et al 2000. Our mensurative sampling using AUHs revealed a pattern of difference in assemblages between locations receiving and those not receiving storm-water run-off.…”

“…Any other variable that differs among locations and that influences assemblages and the distribution of contaminants could also cause the observed correlation. In contrast to most studies, Roberts et al (2007) sampled algalassociated assemblages multiple times before and after storm-water discharges in multiple locations with and without storm-water drains using an MBACI design (Underwood 1994). Although their sampling design increased the power of detecting potential impacts of run-off, it was difficult to link storm-water effects to changes in biota.…”

“…Assemblages were sampled within 4 d of a rainfall event (> 30 mm in total) as the abundance of organisms in algal-associated assemblages appears to be reduced during this period of time (Roberts et al 2007). Second, we transplanted assemblages on AUHs from locations without stormwater drains to locations with storm-water drains.…”

“…Hence, all control locations were (1) at a minimum distance of 300 m from any visible storm-water drain as properties of water quality (i.e. salinity and turbidity) at this minimum distance showed different temporal patterns of changes following rainfall compared to those in locations with storm-water drains (Roberts et al 2007); and (2) surrounded by low density residential/park land areas, which a have a lower impervious surface area than highly urbanised areas (Lee et al 2011). …”

“…Run-off also discharges nutrients and sediments which can directly or indirectly affect habitatforming organisms and associated assemblages (Airoldi 2003, Gorman et al 2009. Moreover, close to the outfalls, the input of fresh-water can reduce salinity for up to 4 d following a rainfall event (Roberts et al 2007), with potential deleterious effects on marine organisms. As urbanisation along coastal areas increases and more intense and frequent rainfall events are expected in the next ABSTRACT: Storm-water run-off is an important source of contamination and cause of water quality degradation in urbanised coastal areas.…”