Aquatic invertebrate communities exhibit both resistance and resilience to seasonal drying in an intermittent coastal stream

Abstract

Species inhabiting intermittent streams must survive flow cessation and drying in situ (resistance) or recolonize temporary habitats when flow returns (resilience). Some studies have found that species are resistant to seasonal drying and can persist in small remnant pools after flow ceases, while others observed rapid declines in species richness when flow ceases. However, relatively few studies have demonstrated both resistance across dry seasons and resilience across multiple wet and dry cycles. Here, we quantify seasonal and interannual changes in aquatic invertebrate community structure from 2009 to 2012 in a coastal California intermittent stream. We predicted that temporary pools and riffles would have lower richness and distinct assemblages when compared to perennial pools, and that richness would decline across the dry season. Temporary riffles exhibited lower richness values than pools, but we found no richness differences, and small compositional differences, between perennial and temporary pools. Furthermore, invertebrate richness, density, and composition changed significantly in temporary pools only immediately before drying, when depths declined >80%. These results suggest that invertebrate communities at John West Fork were not only resilient (exhibiting recovery in <6 months) to flow cessation, but also were resistant to declining water levels across the dry season.