Long‐term effects of climatic–hydrological drivers on macroinvertebrate richness and composition in two Mediterranean streams

Abstract

Summary The unique information provided by multiyear data sets can aid in detecting major long‐term trends and making predictions with respect to environmental and biological variables. These trends are expected to differ among climatic regions but little information exists concerning long‐term variability within a particular climate region. We analysed the long‐term (14‐year time span) patterns in species richness and composition of aquatic insects (EPT: Ephemeroptera, Plecoptera and Trichoptera) in relation to changes in temperature, precipitation and discharge in two reference streams in Catalonia (north‐east Spain). Our study sites were located in the Mediterranean macroclimate region but in different mesoclimatic areas, one in the Wet Mediterranean climate area and the other in the Dry Mediterranean climate area (WM and DM, respectively). At the macroclimate scale, precipitation decreased and the frequency of drought events increased during the 14‐year period. Although the mean number of taxa in each of the two sites remained similar, there was a replacement of species characteristic of riffle‐like conditions by species characteristic of pool‐like conditions over time in both sites. EPT composition differed between sites at the mesoclimate scale, demonstrating the importance of regional factors. In particular, changes in EPT composition were less variable in WM than in DM both in the short term and in the long term, indicating that the WM site was less constrained by climate than the DM site. Such differences between mesoclimates are related to differences in flood magnitude (higher in WM) and drought frequency (more frequent in DM) as well as local hydromorphological differences. Our findings indicate that the streams responded similarly to long‐term patterns in large‐scale variables (i.e. those affecting the overall macroclimatic region), but differed with respect to the effect of local‐scale variables (i.e. those differentially affecting each mesoclimatic area). Predictive bio‐assessment models that use reference conditions must incorporate long‐term variability to accurately assess the ecological status of Mediterranean climate streams.

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

“…There are few datasets available that include more than 10 years of data, which are needed to detect long-term community changes (cf. [26,80,81]). Many of these datasets have been used to relate inter-annual community-changes to climate change, highlighting that the frequency of dry years has increased in more recent years and that communities have changed accordingly.…”

“…Many of these datasets have been used to relate inter-annual community-changes to climate change, highlighting that the frequency of dry years has increased in more recent years and that communities have changed accordingly. For example, Sáinz-Bariáin et al [82] found an increase in Trichoptera richness in high-altitude, mountain Mediterranean rivers after a 20-year period, whereas Pace et al [81] found that riffle species shifted to lentic species during a 14-year period in two Mediterranean streams with different hydrological characteristics. These patterns follow the hydrological changes experienced in these areas that may be the result of a changing climate.…”

Effect of spatial scale on macroinvertebrate assemblages along a Mediterranean river

“…Lenat & Barbour, 1994;Hering et al, 2004;Larsen et al, 2012;Manfrin et al, 2013), and are frequently monitored to detect changes in hydrological and sediment regimes as well as in water quality of river in ecosystems (Boulton et al, 1992;Pace et al, 2013).…”

Drivers of freshwater fish colonisations and extirpations under climate change

“…Climate change is widely recognised as having a profound impact on distribution of species (Pearson and Dawson ), modifying biodiversity patterns in terrestrial (Thuiller et al , Levinsky et al , Huntley et al , La Sorte and Jetz ), marine (Hiddink and ter Hofstede , Cheung et al , Albouy et al ) and fresh water (Buisson et al , Heino et al , Comte et al , Pace et al ) ecosystems. On ecological timescales, species assemblages are the result of a synergic interplay between colonisation and extirpation, two spatial‐ and temporal‐dependent processes influenced by regional and local drivers (He et al , Korhonen et al ).…”