José Barquín

Spatial patterns of macroinvertebrate diversity in New Zealand springbrooks and rhithral streams

Abstract Spatial patterns in macroinvertebrate communities were examined in 4 to 5 rheocrene springbrooks and 4 to 5 nearby rhithral streams in 4 different regions of New Zealand. Physicochemical attributes of springbrooks and rhithral streams were similar, but springbrooks were more stable. Standing crops of periphyton biomass, epilithic C, and organic matter were greater and more variable in springbrooks than in rhithral streams. The number of macroinvertebrate taxa and the total number of individuals were greater at more stable sites. Altitude, habitat stability, and food resource levels were the best predictors of the number of macroinvertebrate taxa, whereas pH, PO4 concentration, habitat stability, and food resource levels were the best predictors of the total number of individuals at a site. Differences in the number of macroinvertebrate taxa between Northern Hemisphere and New Zealand springbrooks may be related to the larger diversity of macroinvertebrate predators in New Zealand springbrooks and to the fact that many New Zealand invertebrates do not use temperature-mediated life-history cues. Altitude, which limits invertebrate dispersal, also may play an important role in determining the maximum number of macroinvertebrate taxa in a given stream. A dispersal–stability framework is proposed to explain the observed patterns of macroinvertebrate diversity in these streams. The general pattern of noninsect dominance in lowland springs may be the result of the interaction between dispersal ability and the effects of the last glaciation.

Patterns of invertebrate diversity in streams and freshwater springs in Northern Spain

Invertebrate diversity patterns were examined in six rheocrene springs and six nearby, runoff-fed streams in Cantabria, Northern Spain. Periphyton biomass, organic matter and biomass of moss were always higher in springs than streams. Species densities (number of species/area) and rarified species richness (number of species/number of individuals) were lower and invertebrate densities greater in spring habitats. Of 22 variables chlorophyll-a was the best predictor of species richness, whereas total organic matter was the best predictor of invertebrate density, although neither relationship was strong. Spring habitats had invertebrate communities dominated by non-insect taxa (e. g., Echinogammarus, and Hydrobiidae and Neritidae snails), in contrast to the insect dominated communities in runoff-fed streams (e. g., Baetis, Ecdyonurus, Elmis, Prosimulium, Scirtes and Chironomidae). Echinogammarus had the highest densities in springs; an order of magnitude greater than any other taxa. The effects of biotic processes, such as predation from Echinogammarus on community structure may be more marked in springs because predated individuals cannot be as readily replaced by drifting animals from upstream reaches. The reduced diversity in springs compared to streams could be a result of several factors including increased predation from animals such as Echinogammarus or the unusually constant thermal characteristics.

Modelling the spatial and seasonal variability of water quality for entire river networks: Relationships with natural and anthropogenic factors.

We model the spatial and seasonal variability of three key water quality variables (water temperature and concentration of nitrates and phosphates) for entire river networks in a large area in northern Spain. Models were developed with the Random Forest technique, using 12 (water temperature and nitrate concentration) and 15 (phosphate concentration) predictor variables as descriptors of several environmental attributes (climate, topography, land-uses, hydrology and anthropogenic pressures). The effect of the different predictors on the response variables was assessed with partial dependence plots and partial correlation analysis. Results indicated that land-uses were important predictors in defining the spatial and seasonal patterns of these three variables. Water temperature was positively related with air temperature and the upstream drainage area, whereas increases in forest cover decreased water temperature. Nitrate concentration was mainly related to the area covered by agricultural land-uses, increasing in winter, probably because of catchment run-off processes. On the other hand, phosphate concentration was highly related to the area covered by urban land-uses in the upstream catchment and to the proximity of the closest upstream effluent. Phosphate concentration increased notably during the low flow period (summer), probably due to the reduction of the dilution capacity. These results provide a large-scale continuous picture of water quality, which could help identify the main sources of change in water quality and assist in the prioritization of river reaches for restoration projects.

Physical and chemical differences in karst springs of Cantabria, northern Spain: do invertebrate communities correspond?

Benthic macroinvertebrate communities were studied and environmental variables were measured in six rheocrene springs in Cantabria, northern Spain. Principal component analysis revealed two different spring types according to their physical and chemical characteristics. Springs from group A (GA) had higher temperature and conductivity, while springs in group B (GB) had higher values of pH, altitude, mean water velocity, percentage of boulders and coarse particulate organic matter. Total number of invertebrate taxa and individuals were not different between GA and GB springs. However, Shannon diversity index was significantly higher for GB springs. Analysis of similarities (ANOSIM) and non-metric multidimensional scaling (NMDS) analysis indicated that invertebrate assemblages from GA and GB springs were different. The snails Theodoxus fluviatilis and Bythinella sp., and the amphipod Echinogammarus spp. had higher densities in GA springs, whereas ephemeropterans, plecopterans, trichopterans and chironomids were more important in GB springs. Higher water velocities in GB springs interacting with predation by Echinogammarus tarraconensis may be responsible for the observed patterns on invertebrate community structure and composition. The taxonomic resolution limited our ability to detect crenobiontic taxa. Sampling aquatic, semi-aquatic and semi-terrestrial habitats are needed to account for the biodiversity patterns of spring habitats.

Microdistribution patterns of macroinvertebrate communities upstream and downstream of organic effluents

The present study analyses the distribution patterns of macroinvertebrate communities in four microhabitats (riffles, glides, leaf litter and bank roots) upstream and downstream of two waste water treatment plant (WWTP) effluents in northern Spain rivers. Macroinvertebrate communities were analysed in November 2006 by taking 5 samples from each of the microhabitats under unaffected (upstream WWTP) and affected (downstream WWTP) conditions, respectively. Water velocity, depth, substrate coarseness and hydraulic stress by means of the Froude number were also estimated at all sampling locations. Under unaffected conditions, the abundance and presence/absence of certain macroinvertebrate taxa were mainly determined by hydraulic characteristics (water velocity and Froude number) and feeding resource availability. However, neither macroinvertebrate richness nor abundance were neither significantly correlated with hydraulic stress nor substrate coarseness, although the number of macroinvertebrate taxa increased in microhabitats with high structural complexity. Macroinvertebrate abundance increased downstream of both WWTPs, while macroinvertebrate richness was not adversely affected by the organic enrichment of water. The structure and composition of macroinvertebrate communities occurring in riffles was similar under unaffected and affected conditions, while communities from leaf litter and submerged bank roots showed important changes above and below the WWTPs, indicating that they are probably the most appropriate communities for water quality assessment.

Macroinvertebrate community dynamics in a temperate European Atlantic river. Do they conform to general ecological theory

Spatial and temporal dynamics of macroinvertebrate communities have usually been linked to several environmental and anthropic factors. The aim of this study is to elucidate how important are these factors in structuring macroinvertebrate communities from temperate regions. Regarding the macroinvertebrate number of taxa, the Habitat Template Model, the Dynamic Equilibrium Hypothesis and the Intermediate Disturbance Hypothesis will be tested in order to know how important the diversity of instream elements and the hydrological disturbance frequency are in defining the macroinvertebrate taxonomic richness. Thus, the structure and composition of macroinvertebrate communities were analysed in nine sites of the Pas River basin, a temperate Atlantic basin in northern Spain, during winter, spring, summer and autumn 2005, together with water physicochemical and environmental characteristics. Macroinvertebrate abundance increased downstream and during summer, probably favoured by lower hydraulic stress and water organic enrichment. As predicts the Habitat Template Model, the macroinvertebrate number of taxa was related to habitat heterogeneity. However, no clear relationship amongst macroinvertebrate richness and water quality was found. The macroinvertebrate taxonomic richness did not correspond exactly with the Dynamic Equilibrium Hypothesis and the Intermediate Disturbance Hypothesis because it was relatively high in the absence of hydrological disturbances (summer). Thus, disturbance events may play a secondary role in determining the seasonal dynamic of the number of taxa. However, hydrological disturbances can be considered the most important factors explaining the seasonal pattern of macroinvertebrate abundance. On the other hand, spatial patterns of macroinvertebrate community structure and composition were mainly determined by resource availability, hydraulic conditions, habitat heterogeneity and human alterations, whilst hydrological predictability and resource availability might play a major role in determining seasonal dynamics.

Building Virtual Watersheds: A Global Opportunity to Strengthen Resource Management and Conservation

Modern land-use planning and conservation strategies at landscape to country scales worldwide require complete and accurate digital representations of river networks, encompassing all channels including the smallest headwaters. The digital river networks, integrated with widely available digital elevation models, also need to have analytical capabilities to support resource management and conservation, including attributing river segments with key stream and watershed data, characterizing topography to identify landforms, discretizing land uses at scales necessary to identify human-environment interactions, and connecting channels downstream and upstream, and to terrestrial environments. We investigate the completeness and analytical capabilities of national to regional scale digital river networks that are available in five countries: Canada, China, Russia, Spain, and United States using actual resource management and conservation projects involving 12 university, agency, and NGO organizations. In addition, we review one pan-European and one global digital river network. Based on our analysis, we conclude that the majority of the regional, national, and global scale digital river networks in our sample lack in network completeness, analytical capabilities or both. To address this limitation, we outline a general framework to build as complete as possible digital river networks and to integrate them with available digital elevation models to create robust analytical capabilities (e.g., virtual watersheds). We believe this presents a global opportunity for in-country agencies, or international players, to support creation of virtual watersheds to increase environmental problem solving, broaden access to the watershed sciences, and strengthen resource management and conservation in countries worldwide.

Geographic location alters the diversity–disturbance response

Abstract.  Despite extensive research on the link between disturbance and diversity in ecology and several eloquent models to describe the relationship, a universally applicable model remains elusive. However, most investigations of the diversity–disturbance relationship have been limited in spatial coverage. Recent theoretical and conceptual advances in macroecology suggest that such spatially constrained studies may limit interpretation. To explore the effect of geographic location on the disturbance–diversity relationship, we examined invertebrate assemblages in streams of northern Spain and New Zealand (NZ) and in multiple regions within NZ. Habitat characteristics were similar across all sites and locations, except that undisturbed sites (springbrooks) differed from disturbed sites (rhithral streams) by having constant thermal and hydrologic regimes. The resource base and the density of invertebrates were greater in the more-stable habitats in all regions. However, patterns of invertebrate species richness differed markedly between locations in the Northern and Southern Hemispheres. Springbrooks in all regions within NZ had greater richness than rhithral streams. In contrast, springbrooks in Spain had considerably lower species richness than rhithral streams. Thus, low hydrological disturbance in Spain yielded low diversity, whereas in NZ it yielded high diversity. Amphipoda dominated the springbrook faunas in Spain, whereas insects dominated in NZ. Thus, differences in the diversity patterns between Spain and NZ are potentially related to phylogenetic differences or environmental constraints on life-history cues. A universal model to link disturbance and diversity is more likely to be successful if it incorporates life-history traits rather than morphological traits.

Modelling macroinvertebrate and fish biotic indices: From reaches to entire river networks

We modelled three macroinvertebrate (IASPT, EPT number of families and LIFE) and one fish (percentage of salmonid biomass) biotic indices to river networks draining a large region (110,000km2) placed in Northern and Eastern Spain. Models were developed using Random Forest and 26 predictor variables (19 predictors to model macroinvertebrate indices and 22 predictors to model the fish index). Predictor variables were related with different environmental characteristics (water quality, physical habitat characteristics, hydrology, topography, geology and human pressures). The importance and effect of predictors on the 4 biotic indices was evaluated with the IncNodePurity index and partial dependence plots, respectively. Results indicated that the spatial variability of macroinvertebrate and fish indices were mostly dependent on the same environmental variables. They decreased in river reaches affected by high mean annual nitrate concentration (>4mg/l) and temperature (>12°C), with low flow water velocity (<0.4m/s) and aquatic plant communities being dominated by macrophytes. These indices were higher in the Atlantic region than in the Mediterranean. This study provides a continuous image of river biological communities used as indicators, which turns very useful to identify the main sources of change in the ecological status of water bodies and assist both, the integrated catchment management and the identification of river reaches for recovery.

Productivity–diversity relationships for stream invertebrates differ geographically

More productive environments typically have more species, although the specific form of this relationship is unclear and can vary with spatial scale. This relationship has received little direct attention in lotic systems, and thus the nature of the relationship is unclear, as is any effect of spatial scale. We examined the link between stream primary productivity and macroinvertebrate diversity in Spain and New Zealand and hypothesized that macroinvertebrate diversity would increase log-linearly with increasing productivity in both regions. We sampled 24 streams in Cantabria, Spain, and 24 in the central North Island, New Zealand. Algal primary productivity was approximately three times higher in Spanish streams, but taxonomic richness of invertebrates did not differ between the regions. Richness and Shannon diversity only responded to productivity in the New Zealand streams, exhibiting the predicted log-linear increase. In the Spanish streams, only the total number of individuals increased with productivity. However, when plotted on the same axes, richness in the Spanish streams simply occurred on the linear portion of the graph to the right of the New Zealand streams. We speculate that productivity in the Spanish streams never became low enough to constrain diversity, but did in the New Zealand streams. Combining results from the two regions, there is no evidence of a decline in diversity with higher productivity.