Resilience of fishes and invertebrates to prolonged drought in two California streams

Abstract

Long-term data are needed to assess spatial and temporal variability of communities and their resilience to natural and anthropogenic disturbances, particularly in climatic regions marked by high interannual variability (e.g. mediterraneanclimate). A long-term study at four sites on two streams in mediterranean-climate California (annual sampling over 20 yr) allowed us to quantify the influence of a 5-yr prolonged drought on stream invertebrate and fish communities. Invertebrate community composition did not show recovery following drought. The primary environmental factors influencing community composition, identified through principle components and multiple correspondence analyses were precipitation and flow permanence. Invertebrate taxon richness and abundance exhibited few responses (some site specific) and recovered quickly. Native fish abundance was lowest during the drought period and highest during the wet years that occurred at the end of the study period. Importantly, the prolonged drought facilitated the establishment and success of the invasive green sunfish (Centrarchidae: Lepomis cyanellus) that was then resilient to subsequent large flow events. There was high spatial synchrony in the temporal changes among all four sites, and three distinct periods were identified: early drought, late drought, and post-drought years. However, we still found differences among sites along the flow permanence gradient from temporary to perennial in the response to drought of both invertebrate and fish assemblages likely as a result of changes in substrate, vegetation, and other habitat characteristics. The observed lack of resilience and negative impacts to biodiversity due to prolonged drought associated with long-term habitat changes is important because hydroclimatic extremes are predicted to increase in frequency and magnitude with global climate change.

High Variability Is a Defining Component of Mediterranean-Climate Rivers and Their Biota

“…Comparisons between wet and dry years have shown that richness and exclusive species are higher in wet than in dry years, which has been related to relatively higher habitat availability in wetter years [83]. However, other studies did not observe these differences in macroinvertebrate richness [21]. For macroinvertebrate density, no significant differences between wet and dry years are reported [21,84].…”

“…However, other studies did not observe these differences in macroinvertebrate richness [21]. For macroinvertebrate density, no significant differences between wet and dry years are reported [21,84].…”

“…Feminella and Resh [40], in a Californian stream, reported on average over a two-fold difference in densities for the caddisfly Helicopsyche borealis for wet years compared to dry years and over a four-fold difference for wet years compared to drought years. Many community level studies conducted over multiple years also have documented significant variation in population densities over time (e.g., [21]). …”

Relative influence of local and landscape-scale features on the density and habitat preferences of longfin and shortfin eels

“…Our work suggested that, to adequately represent patterns in densities, models will need to incorporate both local-scale and landscapescale variables that include interactions and nonlinear relationships. Further studies are in progress, but it seems likely that best approaches will require relatively long-term data and sophisticated modelling tools such as mixed-effects models (Beˆche et al 2009), regression trees (Elith et al 2008) or artificial neural networks (Joy & Death 2004). Consideration of diel variations in local-scale habitat preferences, as has been investigated for other New Zealand native fishes (Davey et al 2010), may also be an area which would benefit from further research.…”

Spatial and temporal distribution of native fish larvae in seasonal and perennial tributaries of the Sacramento River, CA, USA

“…The seasonal drying and rewetting pattern produces a wide array of temporarily inundated aquatic habitats, including seasonal floodplains, wetlands, off-channel ponds, and streams (Gasith and Resh 1999;Bonada et al 2008; *Corresponding author. Email: bec.lorig@gmail.com Beˆche et al 2009). The seasonal aquatic habitats generally retain their connection to permanent water sources for a period of three to seven months due to the predictable precipitation patterns.…”