Measuring the ecological impact of long-term flow disturbance on the macroinvertebrate community in a large Mediterranean climate river

The Feather River is a large flow-regulated river in the Central Valley of California. The Mediterranean climate of the area imposes a natural flow regime for the region that is characterized by predictable high flows in the winter and spring and low flows in the summer and fall. The Oroville Dam complex on the Feather River has created a permanent low-flow section of the river where a base flow is continuous year round but the natural annual variability of flow has been completely eliminated. We used this modified section of the river to examine the ecological impact that removing natural flow variability has on the macroinvertebrate assemblage and how we might measure such a change if it is present. Specifically, we examined whether biodiversity and community similarity differed between the low- and high-flow sections of the river for both benthic and drifting aquatic invertebrates. Using a modified Surber sampler we collected samples at three distinct time periods within a year (January, April, and July) for both drift and benthic fauna. Our results showed little difference between the low- and high-flow assemblages using common measures of diversity (i.e., species richness and Shannon diversity) and a measure of environmental tolerance (Hilsenhoff biotic index). Yet when we employed a multivariate measure of community similarity (i.e., non-metric multidimensional scaling) and associated statistical tests, we found significant assemblage differences between the low- and high-flow sections of the river. This study suggests that flow disturbance of this sort is likely to alter the macroinvertebrate community in ways that are not easily observed using common ecological metrics

Patterns of Freshwater Species Richness, Endemism, and Vulnerability in California.

The ranges and abundances of species that depend on freshwater habitats are declining worldwide. Efforts to counteract those trends are often hampered by a lack of information about species distribution and conservation status and are often strongly biased toward a few well-studied groups. We identified the 3,906 vascular plants, macroinvertebrates, and vertebrates native to California, USA, that depend on fresh water for at least one stage of their life history. We evaluated the conservation status for these taxa using existing government and non-governmental organization assessments (e.g., endangered species act, NatureServe), created a spatial database of locality observations or distribution information from ~400 data sources, and mapped patterns of richness, endemism, and vulnerability. Although nearly half of all taxa with conservation status (n = 1,939) are vulnerable to extinction, only 114 (6%) of those vulnerable taxa have a legal mandate for protection in the form of formal inclusion on a state or federal endangered species list. Endemic taxa are at greater risk than non-endemics, with 90% of the 927 endemic taxa vulnerable to extinction. Records with spatial data were available for a total of 2,276 species (61%). The patterns of species richness differ depending on the taxonomic group analyzed, but are similar across taxonomic level. No particular taxonomic group represents an umbrella for all species, but hotspots of high richness for listed species cover 40% of the hotspots for all other species and 58% of the hotspots for vulnerable freshwater species. By mapping freshwater species hotspots we show locations that represent the top priority for conservation action in the state. This study identifies opportunities to fill gaps in the evaluation of conservation status for freshwater taxa in California, to address the lack of occurrence information for nearly 40% of freshwater taxa and nearly 40% of watersheds in the state, and to implement adequate protections for freshwater taxa where they are currently lacking

Patterns of Freshwater Species Richness, Endemism, and Vulnerability in California.

The ranges and abundances of species that depend on freshwater habitats are declining worldwide. Efforts to counteract those trends are often hampered by a lack of information about species distribution and conservation status and are often strongly biased toward a few well-studied groups. We identified the 3,906 vascular plants, macroinvertebrates, and vertebrates native to California, USA, that depend on fresh water for at least one stage of their life history. We evaluated the conservation status for these taxa using existing government and non-governmental organization assessments (e.g., endangered species act, NatureServe), created a spatial database of locality observations or distribution information from ~400 data sources, and mapped patterns of richness, endemism, and vulnerability. Although nearly half of all taxa with conservation status (n = 1,939) are vulnerable to extinction, only 114 (6%) of those vulnerable taxa have a legal mandate for protection in the form of formal inclusion on a state or federal endangered species list. Endemic taxa are at greater risk than non-endemics, with 90% of the 927 endemic taxa vulnerable to extinction. Records with spatial data were available for a total of 2,276 species (61%). The patterns of species richness differ depending on the taxonomic group analyzed, but are similar across taxonomic level. No particular taxonomic group represents an umbrella for all species, but hotspots of high richness for listed species cover 40% of the hotspots for all other species and 58% of the hotspots for vulnerable freshwater species. By mapping freshwater species hotspots we show locations that represent the top priority for conservation action in the state. This study identifies opportunities to fill gaps in the evaluation of conservation status for freshwater taxa in California, to address the lack of occurrence information for nearly 40% of freshwater taxa and nearly 40% of watersheds in the state, and to implement adequate protections for freshwater taxa where they are currently lacking

Taxonomic grouping and conservation status of freshwater taxa native to California.

<p>Percentage of freshwater species by taxonomic groups that are considered vulnerable (at risk of extinction) in California watersheds, “Insects and other invertebrates” includes the classes Arachnida, Branchiopoda, Insecta and Polychaeta.</p

Taxonomic grouping and conservation rank of freshwater taxa endemic to study area.

<p>Percentage of freshwater endemic species by taxonomic groups that are considered vulnerable (at risk of extinction) in California watersheds. “Insects and other invertebrates” includes the classes Arachnida, Branchiopoda, Insecta and Polychaeta.</p

Location of hotspots.

<p>Comparison of the location of hotspot watersheds (top 5% by richness) for A) listed species with all non-listed species, and B) vulnerable but non-listed species.</p

Patterns of richness and vulnerability of freshwater species endemic to California, watersheds.

<p>Maps of (A) the number of endemic freshwater species in each HUC12 watershed (includes current, historic, range and modeled data). The range of endemic species richness is shown in quintiles, therefore the darkest blue is the top 20% of species richness, the lightest blue the lowest 20%.; (; (B) percentage of endemic species considered vulnerable in each HUC12 watershed; and (C) percentage of endemic species in each HUC12 watershed that are listed as endangered or threatened under state or federal ESA lists. Maps in panels B and C share the legend on the right of the figure. The black lines on the maps represent the major hydrologic regions in the study area.</p

Patterns of richness by data type of California freshwater species.

<p>Maps show the number of native freshwater species when summarized by: (A) observational data recorded after 1980; (B) observational data recorded before 1980 or observations of extirpated populations; and (C) data that includes range maps, historical range maps, modeled habitat, professional judgment, critical habitat designations, and management area designations. Spatial data with an unknown observation date or unknown type are not included in any panel. The black lines on the maps represent the major hydrologic regions in the study area.</p

Patterns of freshwater species richness by taxonomic group.

<p>Maps show richness of: (A) fishes; (B) herpetofauna; (C) birds; (D) mollusks/crustaceans; (E) insects and other invertebrates; (F) plants.</p