Eight new provincial species records of mayflies (Ephemeroptera) from one Arctic watershed river in British Columbia

We repeatedly sampled eight sites on the Crooked River in British Columbia’s Arctic watershed for adult and nymph mayflies (Ephemeroptera) over the course of two years. Using taxonomic keys and DNA-barcoding we report eight new species records for the province. These are five Baetidae (Acerpenna pygmaea, Baetis phoebus, Baetis vernus, Iswaeon anoka, and Procloeon pennulatum), one Heptageniidae (Leucrocuta hebe), one Leptohyphidae (Tricorythodes mosegus), and one Siphlonuridae (Siphlonurus alternatus). Three of these – Acerpenna, Iswaeon, and Leucrocuta – are also new genus records for the province. In total we detected 40 species in eight families as indicated by clustering into BINs (Barcode Index Numbers), by morphological keys, and by matches in the Barcode of Life Database. One of those species, Ameletus vernalis, is of conservation concern. Our analysis indicated that a number of other specimens may represent new species or genus records for BC. In addition this unique and anthropogenically impacted river may contain cryptic species of Baetis tricaudatus (Baetidae), Leptophlebia nebulosa (Leptophlebiidae), and Paraleptophlebia debilis (Leptophlebiidae).

Eight new provincial species records of mayflies (Ephemeroptera) from one Arctic watershed river in British Columbia

We repeatedly sampled eight sites on the Crooked River in British Columbia’s Arctic watershed for adult and nymph mayflies (Ephemeroptera) over the course of two years. Using taxonomic keys and DNA-barcoding we report eight new species records for the province. These are five Baetidae (Acerpenna pygmaea, Baetis phoebus, Baetis vernus, Iswaeon anoka, and Procloeon pennulatum), one Heptageniidae (Leucrocuta hebe), one Leptohyphidae (Tricorythodes mosegus), and one Siphlonuridae (Siphlonurus alternatus). Three of these – Acerpenna, Iswaeon, and Leucrocuta – are also new genus records for the province. In total we detected 40 species in eight families as indicated by clustering into BINs (Barcode Index Numbers), by morphological keys, and by matches in the Barcode of Life Database. One of those species, Ameletus vernalis, is of conservation concern. Our analysis indicated that a number of other specimens may represent new species or genus records for BC. In addition this unique and anthropogenically impacted river may contain cryptic species of Baetis tricaudatus (Baetidae), Leptophlebia nebulosa (Leptophlebiidae), and Paraleptophlebia debilis (Leptophlebiidae).

Grazer–collector facilitation hypothesis supported by laboratory but not field experiments

Grazing invertebrates in streams feed by harvesting algal cells from surfaces, and in doing so release fine particulate organic matter (FPOM). The "grazer–collector facilitation hypothesis" holds that FPOM production by grazers facilitates growth and (or) survival of FPOM-collecting invertebrates. We tested for grazer–collector facilitation in laboratory and field experiments. In recirculating flumes in the laboratory, we tested for facilitation of the collector Hydropsyche slossonae by the grazers Physa gyrina, Glossosoma intermedium, and Baetis tricaudatus. All three grazers increased FPOM levels in flume water, but only Physa facilitated Hydropsyche growth. In the field, we manipulated Physa and Glossosoma densities to test for facilitation (at a local scale) of natural collector assemblages in an eastern Iowa stream. We did not detect facilitation of any collector by either grazer in the field, despite high power to detect such interactions. We suspect that grazer–collector facilitation was not observed in the field because (unlike in our laboratory flumes) field FPOM levels are often high and extremely variable in time and space and because organic particles can arise from sources other than grazer activity (= grazer-independent processing). Therefore, at local scales, collectors may not be significantly limited by the supply of grazer-derived FPOM.

Life history and production of mayflies, stoneflies, and caddisflies (Ephemeroptera, Plecoptera, and Trichoptera) in a spring-fed stream in Prince Edward Island, Canada: evidence for population asynchrony in spring habitats?

We examined the life history and production of the Ephemeroptera, Plecoptera, and Trichoptera (EPT) community along a 500-m stretch of a hydrologically stable cold springbrook in Prince Edward Island during 1997 and 1998. Six mayfly species (Ephemeroptera), 6 stonefly species (Plecoptera), and 11 caddisfly species (Trichoptera) were collected from benthic and emergence samples from five sites in Balsam Hollow Brook. Eleven species were abundant enough for life-history and production analysis: Baetis tricaudatus, Cinygmula subaequalis, Epeorus (Iron) fragilis, and Epeorus (Iron) pleuralis (Ephemeroptera), Paracapnia angulata, Sweltsa naica, Leuctra ferruginea, Amphinemura nigritta, and Nemoura trispinosa (Plecoptera), and Parapsyche apicalis and Rhyacophila brunnea (Trichoptera). Life-cycle timing of EPT taxa in Balsam Hollow Brook was generally similar to other literature reports, but several species showed extended emergence periods when compared with other studies, suggesting a reduction in synchronization of life-cycle timing, possibly as a result of the thermal patterns in the stream. Total EPT secondary production (June 1997 to May 1998) was 2.74–2.80 g·m–2·year–1 dry mass (size-frequency method). Mayflies were dominant, with a production rate of 2.2 g·m–2·year–1 dry mass, followed by caddisflies at 0.41 g·m–2·year–1 dry mass, and stoneflies at 0.19 g·m–2·year–1 dry mass. More than half of the species found in the study stream represented new distribution records for Prince Edward Island.

Ontogenic changes in prey consumption by the stonefly Paragnetina media in relation to temporal variation in prey nutrient content

In Duffin Creek, Ontario, nymphs of the predatory stonefly Paragnetina media (Perlidae) commonly feed on detritus and three prey types: hydropsychid larvae (Hydropsyche sparna and Hydropsyche slossonae), nymphs of the mayfly Baetis tricaudatus, and chironomid larvae belonging to subfamilies Tanypodinae and Orthocladiinae. This study examined temporal changes in the nutrient (lipid and protein) content of these prey to determine if the predator tracks food resources by selecting prey on the basis of nutrient requirements at different stages in its own development. All three common prey types exhibited temporal variation in lipid levels, with peaks occurring at different times: June for the hydropsychids, August for the chironomids, and October for B. tricaudatus. Prey protein levels were less variable. The proportions of the prey types that were eaten varied throughout the year and according to predator size. For example, while small P. media ate mostly detritus, they also consumed early-instar hydropsychids during the larval recruitment period of the latter; mid-sized nymphs included more animal matter in their diet, primarily chironomid larvae; and larger nymphs primarily ate B. tricaudatus. Paragnetina media nymphs in all size categories showed an increase in body lipid level in the autumn, suggesting a general accumulation of lipid reserves in readiness for the winter, although dietary adjustment to accomplish this was detectable only in small P. media. There was no evidence to suggest that P. media selected prey on the basis of the latter's protein content. Male P. media nymphs preyed predominantly on chironomid larvae and included mites in their diet, whereas female nymphs preferred B. tricaudatus and hydropsychids. On a per milligram body mass basis, male nymphs had the higher nutrient gain, since, for both lipid and protein, intake by males was between two and three times that by females. However, male and female bodies had similar lipid contents. We conclude that whereas there is temporal variation both in the nutritional (lipid and protein) content of the common prey of P. media and in this predator's diet, there is only weak evidence for nutrient-resource tracking.

Cumulative effects of multiple effluent and low dissolved oxygen stressors on mayflies at cold temperatures

Effluents produced by pulp mills and sewage plants on northern rivers have the potential for a variety of interacting effects on downstream benthic invertebrates via increased levels of toxicants and nutrients and decreased levels of dissolved oxygen (DO) in the substratum. We experimentally measured the combined effects of these stressors at low temperature (4.5°C) on a common northern river invertebrate, the mayfly Baetis tricaudatus Dodds. Mayflies were exposed in laboratory artificial streams to one of two DO levels (low (5 mg·L-1) versus high (11 mg·L-1)) in the presence and absence of pulp mill and sewage effluent from an Alberta, Canada, mixed-effluent outfall (control river water versus 1% effluent); the DO and effluent treatments bracketed typical field concentrations. In the low-DO treatment, grazing intensity was reduced by 80%, and after 2 weeks of exposure, survival was reduced by 60-90%. Furthermore, 250-350% more mayflies in the low-DO treatment moved upward into regions of greater current velocity close to the surface of the artificial streams, a behavior that would likely make them more susceptible to fish predation in the field. In contrast, the 1% effluent treatment increased mayfly survival (possibly due, in part, to stimulation of increased mayfly grazing intensity by the effluent), although this effect only partly compensated for the pronounced negative impact of low DO levels.