Great Basin Naturalist

Volume 46 Number 4 Article 2

10-31-1986

Composition and abundance of periphyton and aquatic in a Sierra , , stream

Harry V. Leland U.S. Geological Survey, Water Resources Division, Menlo Park, California

Steven V. Fend U.S. Geological Survey, Water Resources Division, Menlo Park, California

James L. Carter U.S. Geological Survey, Water Resources Division, Menlo Park, California

Albert D. Mahood U.S. Geological Survey, Water Resources Division, Menlo Park, California

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Recommended Citation Leland, Harry V.; Fend, Steven V.; Carter, James L.; and Mahood, Albert D. (1986) "Composition and abundance of periphyton and aquatic insects in a , California, stream," Great Basin Naturalist: Vol. 46 : No. 4 , Article 2. Available at: https://scholarsarchive.byu.edu/gbn/vol46/iss4/2

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COMPOSITION AND ABUNDANCE OF PERIPHYTON AND AQUATIC INSECTS IN A SIERRA NEVADA, CALIFORNIA, STREAM

Harry V. Leland', Steven V. Fend\ James L. Carter\ and Albert D. Mahood'

Abstract. —The species composition ofperiphyton and benthic communities and abundances ofcommon taxa (>0.1% of individuals) were examined during snow-free months in Convict Creek, a permanent snowmelt- and spring-fed stream in the Sierra Nevada of California. The communities were highly diverse. The most abundant taxa in the periphyton were diatoms {Achnanthes minutissitna, Cocconeis placentula lineata, Cymbella microcephala, C.

sinuata, Fragilaria construens, F. crotonensis , Navicula spp., Synedra acus, and S. rumpens), except in late spring and summer when several seasonal blue-green algae (Chamaesiphoii incrustans, Lyngbya spp. and Oscillatoria spp.) are at their maximum densities. Most common periphyton taxa vary systematically in abundance with season, but relative abundances of taxa also appear to be influenced by streambed scouring and by concentrations of ambient nutrients. Data on population densities and length frequencies of larval and nymphal stages of common benthic insects and occurrences of pupal and adult stages were examined to determine life history patterns. Taxa hatching in winter and spring and abundant as immatures in late spring include ephemeropterans {Epeortis longimanus, flavilinea and Caudatella heterocaudata), plecopterans (Calineuria californica, Doroneuria baiimanni, and Fteronarcys prin- ceps) and dipterans {Cryptolabis sp.). Common taxa hatching in late spring or summer are the plecopteran Malenka

(californica?) and the trichopterans grandis and Rhyacophila acropedes . Several bivoltine and multi- voltine ephemeropterans (Baetis devinctus and B. tricaudatus) dnd dipterans (Simiiliiim spp. and ) have summer cohorts. Taxa hatching in late summer or autumn and most abundant in autumn include ephemeropterans

{Baetis spp., Ephemerellainfrequens, Epeorus dulciana, Ironodeslepidus , and Paraleptophlebia pallipes), trichopter-

ans (Hydropsyche oslari, Lepidostoma spp. , Glossosoma califica, Micrasema sp. , Brachycentrus americanus, Neophy- lax sp., and Rhyacophila vaccua) and dipterans (Antocha monticola, Pericoma sp., and Chironomidae). Major

recurring events that may influence life history patterns and structure of the benthic insect community are (1) near-freezing, nighttime winter water temperatures and occasional anchor ice, (2) a prolonged period ofhigh discharge in late spring and early summer (3) a brief summer, and (4) a prolonged period of moderate stream discharge in autumn when the substratum is stable and food is abundant.

Despite early biogeographical research on hydrologic extremes on community structure.

aquatic insects of the Sierra Nevada in Cahfor- The ecology of Convict Creek is compared to nia (see Usinger 1956), phenological data and that of other streams at comparable altitudes information on structure of benthic insect in mountain ranges bordering the Great Basin communities in streams of this range are very of the . limited. There is a similar lack of information on production of stream fauna and on the spe- Study Area cies composition and seasonality of stream pe- riphyton. We report results of a four-year in- Convict Creek (Lat. 37° 37' N, Long. 118° vestigation of Convict Creek, a permanent 50' W) is in the Inyo National Forest in Mono snowmelt- and spring-fed stream draining a County, California. The study area lies within 41 km watershed on the steep eastern escarp- Convict Creek basin at an altitude of 2,185 m ment of the Sierra Nevada. The study area in the reserve of the Sierra Nevada Aquatic includes both mesic and xeric terrestrial vege- Research Laboratory. The geology of the up-

tation (Orr 1981). Objectives of this study per part of the basin is unusual for the Sierra were to determine (1) the species composition Nevada in that metamorphic rather than of periphyton and benthic insect communities granitic rocks predominate. The lower part of

of Convict Creek, (2) the temporal variation in the basin, including the study area, is com-

population densities of common taxa, (3) basic posed of alluvium and morainal materials from life histories and annual production of the erosion and glaciation of the area above. The

common benthic insects, and (4) effects of metamorphic rock is of two major types.

U.S. Geological Survey, Water Resources Division, 345 Middlefield Road, Menlo Park, California 94025.

595 596 Great Basin Naturalist Vol. 46, No. \ siliceous horniels and siliceous calc-homfels low the surface of the streambed. A water (Rinehart and Ross 1964). The granitic rock is stage servo-manometer with nitrogen-purge primarily quartz monzonite and granodiorite. system (bubble gage— U.S. Geological Sur- Sandstones in the vicinity of Convict Creek vey 1962) was used to determine discharge are primarily quartz sandstone and calcareous from 1978 through 1980. Stream discharge in quartz sandstone. Mineralogic analyses of fine 1977 was estimated from records maintained sand and silt (fraction <74 |xm) in the sedi- by the Los Angeles Department of Water and ments of Convict Creek indicate an abun- Power at a site approximately 2 km upstream dance of feldspar, quartz, and calcite. of the study area. Degree-day estimates were A Great Basin sagebrush community domi- calculated from 1 January. nated by big sagebrush, Artemisia tridentata Samples of benthic algae were scraped from Nutt., rabbit brush, Chrysothamnus nau- 5x5 cm delineated areas of the upper surfaces seosus (Pall.) Britt. , and antelope bitterbrush, of three separate cobbles (approximately 8 to Piirshia tridentata (Pursh) DC, covers much 12 cm diameter) from the middle of the stream of the study area (Orr 1981). High desert ri- in unshaded riffles. Six samples (three per parian woodland occurs along the stream; site) were taken from the same two riffles dominant species of this community are quak- (each approximately 3 m by 30 m) each date. ing aspen, Popidus tremuloides Michx. , water Sampling was approximately monthly from birch, Betula fontinalis Sarg. and willows, June through November in 1979 and 1980. Salix spp. Riparian meadow vegetation char- Only algae with chloroplasts and intact cell acterized by sedges, Carex spp., rushes, Jun- walls were included in the counts (Leland and cus spp., and various grasses occur along the Carter 1984). Numbers of individuals record- banks in low-lying areas of poorly drained soils. ed for each taxon were cells for free and colo-

Convict Creek is a perennial riflne-pool nial species and filament fragments for fila- stream. Fluctuations in discharge are moder- mentous forms (according to the methods of ated by Convict Lake 4 km upstream and a Greeson et al. 1977, section 7.3). Most di- bypass channel permitting diversion of flood atoms were identified to species, whereas green water around the study area. The streambed and blue-green algae were identified to genus. is rocky, ranging primarily from coarse sand Sampling of aquatic insects was conducted and pebbles to cobbles. The water is clear; monthly to bimonthly from late spring suspended sediment concentrations are typi- through autumn of the years 1977 through cally < 1 mg/liter. The stream is oligotrophic, 1980. The same riffle (approximately 3 m by with nitrate concentrations typically less than 50 m) was sampled each date. An invertebrate 10 |xg/liter NO3-N and ortho-phosphate con- box sampler (Ellis-Rutter)" with a net of 0.35 centrations not exceeding 0.2 (xg/liter mm mesh and sampling area of 0. 1 m^ was PO] - P (Leland and Carter 1985). Silica con- used. Sampling was from the middle of the centrations range from 7.1 to 8.3 mg/liter stream and included both upstream and

SiOo. The water is alkaline (pH 7.9 to 8.5) and downstream areas of the riffle. Three samples always at or near saturation with respect to were taken each sampling date to permit esti- dissolved oxygen. Major ionic constituents (in mation of mean population densities. Samples mg/liter) determined during a period of base were preserved in 70% ethanol and sorted in flow were: Csr\ 23; Mg'", 0.3; K", 0.7; Na", the laboratory with the aid of sugar flotation

1.4;S04 , ll;andCl , 0.2. (Anderson 1959). All aquatic insects were The study area is the 340 m reach of Convict identified to the lowest taxonomic level prac- Creek that was used as a control section in tical (genus or species). Observations on time experimental studies of Leland and Carter of adult emergence, composition of the drift,

(1984, 1985) and Leland et al. (1986). For a and rearing of later instars were conducted to map of the area, see Leland and Carter (1984). provide additional life history information. Abundance data are expressed as popula- Materials and Methods tion densities (individuals/cm" of benthic al- gae and individuals/0. 1 m" of benthic insects). Water temperature and stream discharge in the study area were monitored continuously. "Use of brand names is for identification only does not constitute The temperature sensor was located 5 cm be- t-ndorsenient liy the U.S. Geological Survey. October 1986 Leland et al. : Sierra Nevada Aquatic Insects 597

Temperature Discharge

High flow period

.-^S-^-i\r, 0^

i20

i

'A. / JFMAMJ JASONDJ^/t)U}H>^FMAMJ JASOND MONTH

Fig. 1. Mean daily water temperature and mean daily diseharge of'Convict Creek.

Abundant taxa are defined as those with den- period of high discharge begins in May or sities greater than about 2% of the individuals June and lasts one or two months. Peak dis- of all taxa. Common taxa are those with densities charge (in mVs) was 0.50 in 1977, 1.30 in 1978, greater than 0. 1% of the individuals of all taxa. 1. 15 in 1979, and 2. 14 in 1980. A second high Secondary production was estimated using discharge period occurred in early September the size-frequency method (Hynes and Cole- 1978 due to unseasonably heavy rains accom- 1969, man 1968, Hamilton ' Benke 1979, panying Hurricane Norman. Stream dis- Krueger and Martin 1980), with computations charge generally declines during late summer based on body lengths and dry weights of and autumn and reaches baseflow in October. common taxa. Cohort production intervals, in Mean daily water temperatures in winter days from hatching to the attainment of the ranged from 0.6 to 3.6 C in 1979 and 1980

largest aquatic size class, were determined (Fig. 1). Winter air temperatures were gener- from life history and abundance data summa- ally lower in 1978 and 1979 than in 1977 (a rized in Figure 4. Sampling began in August mild winter) or in 1980 (when an exceptionally 1979 and continued until June 1980. Intervals heavy snow cover was present). Anchor ice between samples were 24, 38, 41, 166, and 39 formed more frequently during the winters of days. 1978 and 1979 than during the other two years. Mean daily water temperatures during Results and Discussion summer (July-August) were higher in 1977 and 1979 than in 1980. Daily means in Octo- Environmental Variables ber did not vary substantially among years. Continuous records of stream discharge Periphyton and water temperature were obtained for most of 1977 through 1980 (Fig. 1). Convict Community Composition. —The periphy- Creek is typically at or near base flow in win- ton of Convict Creek is highly diverse (Table

ter (December to mid-March). The stream 1). A total of 30 genera (at least 104 species) of discharge increases in late spring due to diatoms, 24 genera of green algae, and 29 snowmelt higher in the basin. This annual genera of blue-green algae were identified 598 Great Basin Naturalist Vol. 46, No. 4

Table 1. Benthic algae of Convict Creek Table 1 continued.

Denticula spp. Chlorophyta Diatoma hiemale (Lyngb.) Heib. Ankistrodesmus falcatiis (Corda) Ralfs D. vulgare Bory Carteria spp. Diploneis ovalis oblongella (Naeg.) Cl. Chaetophora spp. Epithemia adnata adnata (Kutz.) Breb. Characium spp. E. sorex Kutz. Cladophora spp. £. turgida (Ehr.) Kutz. Closterium spp. £. turgida granulata (Ehr.) Brun Coelastrtim spp. Fragilaria brevistriata inflata (Pant.) Hust. Coleochaete spp. F. construens (Ehr.) Grun. Cylindrocapsa spp. F. construens binodis (Ehr.) Grun. Dictyosphaerium spp. F. crotonensis Kitton Draparnaldia spp. F. leptostauron (Ehr.) Hust. Elakatothrix spp. F. pinnata Ehr. Gloeocystis spp. Frustulia spp. Mougeotia spp. Gomphoneis herculeana (Ehr.) Cl. Oedogonium spp. Gomphonema acuminatum Ehr. Oocystis spp. G. dichotomum Kutz. Pediastrum spp. G. olivaceum (Lyngb.) Kutz. Protoderma spp. G. paruw/um (Kutz.) Rhizoclonium spp. G. subclavatum (Grun.) Grun. Spirogyra grantiana Transeau G. truncatum Ehr. Stigeoclonium spp. Hantzschia spp. Ulothrix spp. Melosira various Ag. Zygnema spp. Navicula arvensis Hust. EUGLENOPHYTA N. aurora Sov. Euglena spp. N. bacillum Ehr. Trachelomonas spp. iV. capitata Ehr.

iV. cocconeiformis Greg, ex Grev. Pyrrophyta N. cryptocephala Kutz. Ceratium hinindinella (O.F. Mull) Dujardin N. hambergii Hust. Chrysophyta N. lanceolata (Ag.) Kutz. Xanthophyceae N. pupula Kutz. Vaucheria spp. N. radiosa Kutz. Chrysophyceae N. rhynchocephala Kutz. Dinobryon cylindricum Imhof ex Ahlstrom N. salinarum Grun. D. sertularia Ehr. N. seminulum Grun. N. tripunctata (O.F. Mull.) Bory Bacillariophyceae Neidium spp. Achnanthes bergiani Cleve-Euler Nitzschia acicularis W . Sm. A. exigua Grun. IV. actinastroides (Lemm) v. Goor A. lanceolata Breb. gx Kutz. N. amphibia Grun. A. /mecm(W. Sm.) Grun. N. dissipata (Kutz.) Grun. A. minutissima Kutz. N. frustulum (Kutz.) Grun. Amphora ovalis (Kutz.) Kutz. N. /ineamW. Sm. A. perptisilla (Grun.) Grun. N. pa/cfl (Kutz.) W. Sm. Amphipleura pellucida Kutz. N. stgJTMi (Kutz.) W. Sm. Asterionella formosa Hass. /v. uifrea Norman Ceratoneis (=Hannaea) arciis Ehr. Kutz. Pinnularia nodosa (Ehr.) W. Sm. Cocconeis pediculus Ehr. P. rupestris Hantz. C. placentula euglypta (Ehr.) CI. Rhopalodia gibba (Ehr.) O. Mull. C. placentula lineata (Ehr.) V. H. Stauroneis spp. Cyclotella comta (Ehr.) Kutz. Stephanodiscus spp. C. kutzingiana Thwaites Surirella spp. C. stelligera CI. and Grun. Synedra acus Kutz. Cymbella affinis Kutz. S. radians Kutz. C. brehmii Hust. S. rumpens Kutz. C. lanceolata (Ag.) Ag. S. rumpens fragilaroides Grun. C. mexicana (Ehr.) CI. S. u/na(Nitz.)Ehr. C. microcephala Grun. S. u/na oxyrhynchus Kutz. C. minuta minuta Hilse ex Rabh. S. uina spathulifera (Grun.) V. H. C. perpusilla Cl. Tabellaria fenestrata (Lyngb.) Kutz. C. prosfrato (Berk.) Cl. C. sinuata Greg. Rhodophyta C. fiimida (Breb ex Kutz.) V.H. Batrachospermum spp. October 1986 Leland et al.; Sierra Nevada Aquatic Insects 599

Table 1 continued. abundant in autumn. The major exceptions Cyanophyta were Fragilaria crotonensis, characteristi- Amphithrix spp. cally a planktonic species and perhaps an op- Anabaena spp. portunist in the periphyton of Convict Creek Anabaenopsis spp. (Convict Lake is 4 km upstream), and Fragi- Aphanocapsa spp. Calothrix spp. laria construens. Both taxa were highly vari- Chamaesiphon incrustans (Grun. able spatially. Chroococcus spp. Late spring-summer: The principal species Coelosphaerhim spp. of Gomphone7na (parvulwn, subclavatum, Colosterium spp. and truncatum ) in Convict Creek were Cylindrospermum spp. appar- Dactylococcopsis spp. ently most abundant in winter and early Dichothrix spp. spring. The dominant algae in late spring and Gloeotrichia spp. summer were the diatom Achnanthes Hapalosiphon spp. minutissima and the blue-green Lyngbya Lyngbya spp. spp. population densities Merismopedia spp. ; of the two co-domi- Microcystis spp. nants declined markedly by early autumn. Nodularia spp. Densities ofA. minutissima and Lyngbya spp. Nostoc spp. were 3 and 11 times higher, respectively, in Oscillatoria spp. late spring 1980 than in late spring Phormidium spp. 1979, Plectonema spp. which accounted for a higher standing stock Raphidiopsis spp. (total number of individuals of all taxa) in Rivularia spp. 1980. Other diatoms that had population max- Sc/iizof/in'.T spp. ima in late spring-summer are Synedra acus, Scytonema spp. S. Spirulina spp. rumpens, and S. ulna. These species are Stigonema spp. early colonizers of denuded surfaces in Con- Tolypothrix spp. vict Creek (Leland and Carter 1984). The highly invasive blue-green Chamaesiphon in- crustans was also most abundant in late during the study. All of the most abundant spring-summer. taxa are diatoms, except for a few blue-greens Late summer-early autumn: Stream dis- that attain high abundance in late spring- charge was substantially higher in late summer. The composition of benthic algae in spring-summer 1980 than during the same Sierra Nevada streams is poorly known. Hoff- period in 1979. By early August between-year man (1978) provided a partial inventory (23 differences in periphyton assemblages were species) of diatoms in Martis Creek, a peren- apparent. The blue-green Oscillatoria spp. nial stream in the Truckee River Basin. was ver\' abundant in the summer of 1979 but Twelve of the 23 species, all cosmopolitan in not in 1980. The lower population density of their distribution, are common in both Martis Oscillatoria spp. in summer 1980 may have Creek and Convict Creek. Sanford (1972) been related to the higher stream discharge. hsted the conspicuous benthic algae in However, the rate of primary production was streams draining Feeley Lake and Round lower in 1980 (Leland and Carter 1985). Pri- Lake in Tahoe National Forest; the dominant mary production (estimated from three-week taxa in these streams are not abundant in Con- accumulations of autotrophic biomass on arti- vict Creek. ficial substrates) ranged from 0.22 to 0.58 mg

Seasonal Abundances of Common C/m'/hr in summer-autumn 1979, but it de- Taxa.— Mean population densities of 22 com- chned to 0.08 to 0.28 mg C/m%r after peak mon benthic algae in Convict Creek from late discharge in summer 1980, apparently due to spring through autumn are presented in Fig- phosphorus-limited growth. Oscillatoria spe- ure 2. An ordination method (detrended cor- cies are generally abundant only in areas of respondence analysis [Hill 1979, Hill and nutrient enrichment (VanLandingham 1982). Gauch 1980, Leland and Carter 1986]) was The decrease in density of this taxon in sum- used to objectively order the taxa. The order- mer 1980 may have been attributable to ing emphasizes the seasonal progression from slower growth in a phosphorus-deficient envi- taxa most abundant in spring to taxa most ronment. 600 Great Basin Naturalist Vol. 46, No. 4

Lyngbya spp. Cocconeis placenta Ia

Gomphonema spp. Cymbella sinaata

Synedra acus Cymbella minuta

CeratoneIs areas Calothrix spp. O Nitzschia spp. Cymbella microcephala -J < ^ 12 Cladophora spp. Frag 11aria constraens

Achpanthes minutissima FragliarI a crotonensis

o Oscillatoria spp. Navlcala spp.

Synedra rumpens Amphlpleara pelladda

Mougeotia spp. Cyclotella comta

Synedra ulna Spirogyra spp.

I I I I I I I LLi I I I I I I I I I I I I I JJASON JJASON JJASON JJASON 1979 1980 1979 1980

Fig. 2. Mean population densities (n 6) of'eomnion benthic alt^ae on sti lanihed col)ble of'Convict Creek. Densities were normalized by natural logarithmic transformation prior to takulating m»'ans and standard errors. Seasonal population trends identified in the text are based on mean densities ditVering b\ at least the sum of the standard errors of the means. October 1986 Leland et al. : Sierra Nevada Aquatic Insects 601

Table 2. Benthic insects of Convict Creek. Table 2 continued.

Ephemeroptera * Hydropsyche oslari (Banks) Siphlonuridae Rhyacophilidae + Ameletus sp. * Rhyacophila acropedes Banks Baetidae Rhyacophila angelita Banks * Rhyacophila Baetis devinctus Traver vaccua Milne + sp. Baetis tricaudatus Dodds Rhyacophila + Baetis spp. Clossosomatidae + Calllhaetis pacifictis Seeman Agapetus taho Ross * Heptageniidae Glossosoma califica Denning Cinygmula sp. Hydroptilidae + Epeorus dulciana (McDunnough) + Agraylea saltesa Ross * Epeorus longimanus (Eaton) + Hydroptila spp. Ironodes lepidus Traver + Oxyethira sp. Rhithrogena sp. Brachycentridae * Brachycentrus americanus (Banks) * Caudatella heterocaudata (McDunnough) + Micrasema sp. * Caudatella hystrix (Traver) Lepidostomatidae Drunella doddsi (Needham) * Lepidostoma cascadense (Milne) * Drunella flavilinea (McDunnough) * Lepidostoma rayneri Ross Drunella grandis (Eaton) + Lepidostoma sp. * Drunella pelosa (Mayo) Limnephilidae * Epheinerella infrequens McDunnough + Dicosmoecus atripes (Hagen) Serratella tibialis (McDunnough) + Neophylax sp. Tricorythidae Tricorythodes minutus Traver Leptoceridae Triaenodes sp. Leptophlebiidae * Paraleptophlebia pallipes (Hagen) Lepidoptera Pyralidae undetermined genus Pteronarcidae * Pteronarcys princeps Banks Coleoptera Dytiscidae * Pteronarcella regularis Hagen Agabus obsoletus (LeConte) Peltoperlidae Bidessus sp. Yoraperla brevis (Banks) Deronectes striatellus (LeConte) Nemouridae Deronectes sp.

Malenka sp. , probably californica (Claassen) Hydroporus sp. * Zapada cinctipes (Banks) Laccophilus decipiens LeConte Rhantus binotatus Harris * Calineuria californica (Banks) Hydrophilidae Doroneuria baumanni Stark & Gaufin Ametor scabrosus (Horn) * Hesperoperla pacifica (Banks) Berosiis sp. Chloroperlidae Laccobius ellipticus LeConte * undetermined genus Sweltsa sp. , probably pacifica (Banks) Hydraenidae Hemiptera Hydraena vandykei d'Orchymont Belostomatidae Ochthebius interruptus LeConte Belostonia bakeri Montd. Corixidae Cleptelmis addenda (Fall) Corisella inscripta Uhler + Lara avara LeConte Sigara washingtonensis Hungerford Narpus sp. Megaloptera divergens (LeConte) Corydalidae Optioservus quadrimaculatus (Horn) Orohermes crepusculus (Chandler) Zaitzevia parvula Horn Trichoptera Diptera Philopotamidae Deuterophlebiidae * Wormaldia sp. gabriella * Deuterophlebia nielsoni Kennedy , probably Banks Polycentropodidae Blephariceridae + Polycentropus sp. Agathon comstocki Kellogg Tipulidae * Arctopsyche grandis (Banks) * Antocha monticola Alexander 602 Great Basin Naturalist Vol. 46, No. 4

Table 2 continued. Nitzschio fnistidum , and N. pa/ea . The green

Crijptolabis sp. algae Moiigeotia spp. and Cladophora spp. + Dicranota sp. were also abundant at this time. Cymbella Gonomijia sp. microcephala and C. sinuata were early colo- + Hexatoma sp. nizers in late summer, whereas the other taxa Pedicia sp. were later successional species. Tipula spp. Autumn: Common taxa with population + Psychodidae Pericoma sp. maxima in autumn were the diatoms Cy- Maruina sp. clotella cortita, Navicula spp. (principally + Ceratopogonidae cryptocephala, rhynchocephala and arven- spp. Palpomijia or Bezzia sis), and Amphipleura pellucida , the green Simuliidae alga Spirogyra spp. (principally grantiana), * Simtiliwn aureum Fries and the blue-green Calothrix spp. By mid- * Simulium arcticum Malloch October 1979 Spirogyra spp. was a co-domi- + Simulium spp. Prosimulium dicum Dyar & Shannon nant but in 1980 it was never very abundant, whereas Lynghya spp., Achnanthes minutis- Chironomidae Tanypodinae sima, Cocconeis placentula lineata, Cymbella Tamjpus sp. microcephala, C. sinuata, Fragilaria con- Thienemannimyia group struens, Navicida spp. and Synedra rumpens Diamesinae were abundant both years. By mid-November + sp. Diamesa A. minutissima, F. construens, and F. cro- Diamesa latitarsus (Goetghebuer) tonensis were the most abundant diatoms. Pagastia sp. Prodiamesa sp. Calothrix spp. was abundant in late autumn 1979 but not in 1980. Spirogyra spp. was the Chaetocladius spp. principal green alga in late autumn 1979, Corynoneura spp. whereas Cladophora spp. was more abundant + Cricotopus spp. in 1980. Cricotopus hicinctus group + Eukiefferiella spp. Benthic Insects Eukiefferiella bavarica group Eukiefferiella brevicalcar group Community Composition. —Comprehen- Eukiefferiella potthasti group sive lists of benthic insects exist for several Krenosmittia sp. Nanocladius sp. streams of the eastern Sierra Nevada at ap- Orthocladius spp. proximately the same altitude as Convict Orthocladius (Euorthocladius) sp. Creek. Three streams in the Truckee River Pseudorthocladius sp. Basin, Sagehen Creek (Card 1961, Siegfried Thienemanniella sp. 1 Thienemanniella spp. and Knight 1975), Berry Creek (Siegfried and Knight 1975), and Prosser Creek (Needham Chironominae Dicrotendipes sp. and Usinger 1956), have faunal compositions Polypedilum laetum (Meigen) (comparing genera) similar to that of Convict Polypedilum (Tripodura sp. ) Creek (Convict Creek taxa are listed in Table Polypedilum spp. 2). However, the Truckee River Basin Pseudochironomus sp. streams have higher densities of the eph- Empididae emeropterans Cinygmula and Rhithrogena, Chelifera sp. + Wiedemannia sp. their species of Ephemerellidae are mostly undetermined genus different, and we did not collect the ple- Muscidae copteran families Leuctridae, Capniidae, and Limnophora sp. Perlodidae (but Kennedy [1967] did report * Species reported by Kennedy (1967) Leuctridae and Capniidae in Convict Creek). +Genus or family reported by Kennedy (1967) Maciolek and Tunzi (1968) listed the fauna of

Laurel Creek, which is near Convict Creek Common diatoms in Convict Creek with but at a higher elevation. Fewer taxa are population maxima during late summer-early present in Laurel Creek, but benthic insect autumn were Cocconeis placentiila lineata, compositions of the two streams are similar. Cymbella microcephala, Cipnhella sinuata. Kennedy (1967) listed the benthic insects of —

October 1986 Lelandetal: Sierra Nevada Aquatic Insects 603

Convict Creek during 1961-1963 but pre- most individuals emerge later in the summer. sented little information on population densi- Slow growth or a diapause in autumn and ties; most of the common taxa we observed in early winter for eggs and early instars, fol-

1977-1980 were also found by Kennedy lowed by a rapid development in spring, is (Table 2). Some apparent differences in the suggested for all three species. This corre- stream fauna between the early 1960s and late sponds to the "fast seasonal" type of life history 1970s are due to difficulties in identifying im- described by Hynes (1970). Similar life histo- mature stages and differences in sampling ries have been reported for D. flavilinea in method. Kennedy (1967) collected exten- Idaho (Andrews and Minshall 1979) and E. sively only from riffles, whereas midriffle ben- longimanus in Alberta (Hartland-Row 1964). thos and drift were sampled in the present Early instars of the plecopterans C. califor- study. Notable differences between our spe- nica, D. haumanni, and P. princeps are most cies list and that of Kennedy (1967) are (1) that abundant in late spring. These species typi- Optioservtis divergens, Ironodes lepidus, cally have a two- or three-year life cycle, and Doroneuria bawnanni, and Malenka {califor- egg development requires as long as 8 to 10 nica?) are common taxa now but were not months (Siegfried and Knight 1977, Barton reported in 1961-1963 and (2) that Kennedy 1980). Hatching of C. californica und D . hau- (1967) found three winter stoneflies (Leuctri- manni extends over several months since dae and Capniidae) not observed in 1977- early instars are also present in autumn. Rates 1980. These stoneflies typically develop in of development of all three species are proba- winter-spring and may have been missed in bly highest during late spring and summer our sampling program. (Heiman and Knight 1975, Siegfried and Seasonality and Life Histories of Com- Knight 1977). mon Taxa. —Mean population densities of 28 Cryptolabis sp. is the most abundant tip- common benthic insects in Convict Creek are ulid in Convict Creek and is especially preva- given in Fig. 3. The taxa are ordered by their lent in late spring. Development occurs pri- location on the primary axis in ordination marily between August and May and space (detrended correspondence analysis individuals overwinter as middle to late in- see Leland et al. 1986). Seasonality of taxa is stars; pupation occurs in July. The relative emphasized in the ordering. Data on popula- scarcity of early instars indicates that at this tion densities (which emphasize early and stage Cryptolabis sp. may be hyporheic or middle instars) are supplemented with obser- inhabit regions of slower current. Two other vations on the occurrences of late instars, pu- common dipterans, Deuterophlebia nielsoni pae, and adults and on length-frequency data and Palpomyia spp., are most abundant dur- to determine life histories (Fig. 4). ing late spring, but their population densities

Late spring (400 to 1,200 degree-days): are never high. Deuterophlebia nielsoni is Taxa most abundant during May and June are multivoltine (Kennedy 1967); however, we considered late-spring fauna. Species in this did not observe larvae of this species after assemblage include ephemeropterans (Epe- September. orus longimanus, Drunella flavilinea, and Su7nmer (1 ,200 to 2,200 degree-days): Pop- Caudatella heterocaudata), plecopterans ulation densities of many common taxa in {Calineuria californica, Doroneuria hau- Convict Creek are lowest in early summer. manni, and Pteronarcys princeps), and This is generally true for temperate streams dipterans (Cryptolabis sp. and Palpomyia (Hynes 1970) and is due at least in part to the spp.). The three ephemeropterans occur as lag between spring adult emergence and middle to late instars in late spring. Their hatch of the next generation. Nighttime air major period of growth and development is temperatures generally remain above freez- early to late spring, and adults appear during ing during late spring and early summer, and late spring and summer (Fig. 4). Nymphs are emergence of most species occurs at this time not common in autumn, so most early instars (see Fig. 4). Scouring of the streambed during must first appear during winter (as early as periods of high discharge in late spring- December for D. flavilinea) or early spring. summer also appears to contribute to popula- Caudatella heterocaudata develops some- tion declines. Other authors (Gaufin 1959, what later than the other two species, and Canton and Ward 1978, Minshall 1981) have 604 Great Basin Naturalist Vol. 46, No. 4

Epeorus longimanus

[; October 1986 Leland etal.: Sierra Nevada Aquatic Insects 605

tpeonis loiigimanus Arclopsychc grandis 606 Great Basin Naturalist Vol. 46, No. 4

Simulium spp. and Chironomidae are usually ford 1982). Many other trichopterans also most abundant from August through Novem- have peak abundances in autumn. Early in- ber. These taxa include a large number of stars of Lepidostoma spp. are common in species (see Table 2 for a list of the Chironomi- riffles in autumn, but the taxon is rarely found dae and Kennedy 1967 for a list of Simulium there in spring. Larvae apparently move into species.) Because of our inability to identify areas of slower current in later developmental early instars, these taxa were enumerated by stages. Glossosoma califica and Micrasema family; therefore, life histories cannot be de- sp. develop slowly during autumn, overwin- scribed. The family Simuliidae was repre- ter as early to middle instars, and pupate in sented only by Simulium spp. in riffle sam- late spring-summer. Brachycentrus ameri- ples, but a few adult Prosimulium dicum canus and Neophylax sp. develop to middle appeared in drift samples. A major emergence instars by December, but emergence does of Simulium spp. occurred in September not occur until late spring or summer. Rhya- 1980, but emergence was not as synchronous cophila vacciia hatches during summer and in other years. autumn, overwinters primarily as middle in- Auturnn (2,200 to 3,100 degree-days): Peak stars, and emerges in early summer. densities of many common taxa in Convict Chironomidae are abundant throughout Creek occur in autumn. The community con- autumn. Two other dipterans, Antocha mon- sists largely of early instars of "slow seasonal" ticola and Pericoma sp. , also are at their maxi- species (Hynes 1970), insects that hatch mum densities in autumn but neither is ever quickly, develop partially during autumn, and abundant. Antocha monticola completes most emerge in spring (Fig. 4). Although some taxa of its development in late summer and au- are probably detritivores (for example, Para- tumn. Although larvae were uncommon in leptophlebia pallipes and Lepidostoma spp.) riffles in summer, a large number of adults in and may have life histories timed to periods of August 1980 emergence samples indicates that leaf fall (Anderson and Cummins 1979), most emergence occurs throughout the summer. are generalists and relative amounts of de- Late winter/early spring (0 to 400 degree- tritus and algae ingested vary seasonally days): Samples of benthic insects were not

(Chapman and Demory 1963, Gray and Ward taken from January through April. This is ap- 1979). Food quality probably influences life parently an active period for many species. history patterns, but a more significant factor Many late spring species must develop in Convict Creek may be that autumn is a rapidly after overwintering as eggs or early period when the stream is typically at or near instars. The autumn taxa are present primar- base flow. The moderate stream velocities ily as later instars, and many of these emerge may enhance survival of early instars by in the spring. providing suitable substratum. ^^Aseasonal" taxa : Some taxa are abundant Ephemerella infrequens and Epeorus dul- throughout the snow-free months of the year, ciana are common ephemeropterans in Con- and population densities do not show strong vict Creek with autumn and early spring de- seasonal trends. Baetis spp. (principally B. velopment. Ephemerella infrequens has a devinctus and B. tricaudatus) is the most similar life history in Colorado (Ward and abundant ephemeropteran taxon most of the

Berner 1980). Ironodes lepidus is less abun- year. Both species are bivoltine, with emer- dant in Convict Creek, but our limited data gences in May-June and September. The au- indicate a similar life history. Paralep- tumn cohort is larger. Approximately 1,400 tophlebia pallipes grows most rapidly in au- degree-days accumulate during development tumn, but hatching is apparently delayed in of a generation. The elmid Optioservus diver- some individuals since recruitment continues gens appears to have a two-year life cycle (as through autumn. Low numbers of these taxa was also described for O. ampliatus in eastern in June indicate a spring emergence. Canada by Le Sage and Harper 1976). Peak

Hydropsyche oslari is the dominant tri- numbers of early instars occur between Au- chopteran by late autumn. Most individuals gust and October, and most of this cohort overwinter as third to fifth instars. This spe- reaches middle-instar stages by December. cies overwinters at an earlier stage (first and Plecopterans in Convict Creek show less second instars) in Montana (Hauer and Stan- seasonal variation in abundance than do other October 1986 Leland et al. : Sierra Nevada Aquatic Insects 607

discharge accompanying Hurricane Norman in early autumn 1978 probably caused the low autumn densities of Glossosoma califica, Paraleptophlebia pallipes, Epeorus dulciana,

Optioservus divergens , and some of the larger plecopterans. The severe winter conditions of early 1978 may have contributed to the popu- J JASONDJASONJASONDMJ JASON lation declines of the semivoltine O. diver- 1977 1978 1979 1980 gens, Pteronarcys princeps , and Doroneuria

Fig. 5. Total densities (n = 3) of benthic insects in riffle baumanni . Severe winters appear to result in areas of Convict Creek. Densities were normalized by a high mortality of benthic insects. Reimers natural logarithmic transformation prior to calculating (1957) found that populations of ephemerop- means and standard errors. terans and elmid in Convict Creek are reduced more by unusually cold winters than orders of benthic insects. Calineuria Califor- are populations of dipterans and trichopter- nia, Doroneuria baumanni, and Pteronarcys ans. princeps all are semivoltine. However, the Winter air temperatures remained low population density of Sweltsa sp., which is longer (through March) in 1980 than in other probably univoltine, did not vary much ei- years, but a heavy snow cover and unusually ther. This may be due to the presence of more high winter baseflow prevented much anchor than one species. ice formation. The late spring-summer period Yearly Variation in Relative Abun- of high discharge began late and continued dances OF Taxa. —Population densities of through early August. Summer water temper- many common benthic insects in Convict atures were generally lower than in 1977 and Creek varied substantially among years. Be- 1979. Several taxa, including most plecopter- cause our sampling interval was wide and sea- ans, were more abundant than in other years. sonal changes in population density were pro- These included Doroneuria baumanni, Cal- nounced, only major among-year differences ineuria californica, Pteronarcys princeps, can be defined with certainty. Rhyacophila vaccua, and possibly Micrasema The total number of individuals of all ben- sp., Palpomyia spp., Malenka (californica?),

thic insect taxa was unusually high in late and Sweltsa pacifica . The greater abundances autumn 1977 (Fig. 5), a year of low discharge of these taxa in autumn 1980 may be the result during all seasons and relatively high summer of a more effective sorting of streambed sedi- water temperatures (Fig. 1). Population den- ments due to the unusually high discharge in sities of Baetis spp., Paraleptophlebia pal- late spring-summer (DeMarch 1976). The ab- lipes, Epeorus dulciana, and Antocha monti- sence of anchor ice in winter may have con- cola, which hatch in autumn, were highest in tributed to the increased survival rate of the late autumn 1977. Reproduction and survival 1979 cohorts of D. baumanni, C. californica, of early instars of these taxa were apparently and P. princeps . favored by the relatively mild hydrologic and Benthic Insect Production climatic conditions. Except for P. pallipes, these taxa are all clinging, epilithic grazers The total annual production of herbivorous (Merritt and Cummins 1984) and thus benefit and detritivorous benthic insects in Convict from nondisruptive stream flows. Pericoma Creek riffle areas was an estimated 3.9 g/m^ sp., which typically resides in fine sediments (dry weight) (Table 3). Not included in this or algal mats (Usinger 1956, Merritt and Cum- estimate is the contribution of oligochaetes mins 1984), was also common in riffles in au- and molluscs, which is approximately 10%- tumn 1977. Ephemerella infrequens , another 20% of the mean annual standing stock. The autumn-hatching ephemeropteran, was less total annual production of benthic insect abundant in 1977 than other years. predators was an estimated 1.7 g/m^. These Sampling of benthic insects was not ini- annual production estimates compare favor- tiated until August in 1978, so any effects of ably with the values of Krueger and Waters the severe winter conditions on winter and (1983) for the Caribou River and Blackhoof spring fauna could not be observed. The high River, streams in Minnesota with similar sub- 608 Great Basin Naturalist Vol. 46, No. 4

Table 3. Annual production, mean annual standing stock, and cohort production interval (CPI) for the more abundant benthic insects in 1979—80. October 1986 Leland et al. ; Sierra Nevada Aquatic Insects 609 laria, and Gomphonema) and primary pro- primary productivity is at its annual maxi- duction is low. It is a period of activity for mum. Some bivoltine and multivoltine ben- many benthic insects, with taxa that repro- thic insects have summer cohorts and grow duce in autumn present primarily as later in- more rapidly than do individuals of the au- stars. Unusually cold winters cause a high but tumn cohorts. selective mortality of benthic insects (Reimers Autumn is a season of declining water tem- 1957). Despite low water temperatures, perature and stream discharge, and baseflow brown trout {Salmo trutta L.) feed throughout is reached in October. Leaf-fall occurs from the season (Jenkins 1969). mid-September through October, with leaf The water temperature begins to rise about litter in the stream most abundant in October. mid-March and increases through June or Between-year differences in periphyton com- July. Snowmelt in higher areas of Convict position were large, apparently due to envi- Creek Basin causes a substantial increase in ronmental factors influencing the relative discharge, beginning in May or June, which abundances of taxa at earlier successional lasts for one to two months. In early summer a stages (see also Leland and Carter 1986). Most dense riparian canopy dominated by willows slow-seasonal and multivoltine insects hatch and quaking aspen develops in some stream during autumn, so this is a period of high reaches. The high discharge in late spring- abundance of early instars. Some of these are summer is accompanied by declines in stand- detritivorous (for example Paraleptophlebia ing crops of periphyton and benthic insects. pallipes and Lepidostorna spp.) and may have Succession in the periphyton community is life histories timed to the autumn abundance interrupted by scouring of the streambed in of leaf litter. late spring and early summer. Relative abun- dances of periphyton taxa in late summer and Acknowledgments autumn appear to reflect the magnitude of discharge in late spring-summer and the The contributions of Charles B. Doherty, availability of nutrients (see also Leland and Thomas L. Dudley, and William H. Peeler in Carter 1985). When stream discharge in late fieldwork and in the identification and enu- spring was exceptionally high and primary meration of benthic insects are gratefully ac- productivity relatively low, the community knowledged. The identifications were con- was dominated by early-colonizing diatoms firmed whenever possible using museum during summer; diatoms and filamentous specimens of the California Academy of Sci- green and blue-green algae were all abundant ences, San Jose State University, and Oregon in autumn. When stream discharge in late State University. Rearing of specimens was spring was only moderately high and the rate done in some instances to aid in the identifica- of production relatively high, blue-green al- tions. Larry Tilley and Suzanne F. Muzzio gae dominated in summer and remained J. verified identifications of the Chironomidae. abundant in autumn. All the above individuals are or were em- There is a total emergence (hence repro- of the U.S. Geological Survey at the ductive) period of at least seven months ployees L. (April-October) for benthic insects, but most time the work was done. Sam VanLanding- early identifica- species emerge in late spring and early sum- ham, consulting biologist, did mer. Low population densities during late tions of the green algae and blue-green algae. spring and early summer are thus due at least The program for computing secondary pro- in part to the lag between emergence and duction was obtained from Charles C. hatch of the next generation. Scouring of the Krueger (Department of Entomology, Fish- streambed also appears to contribute to the eries and Wildlife, University of Minnesota). population declines. Permission to conduct studies in Convict

Summer is the only season when nighttime Creek was granted by the governing board of air temperatures consistently remain above the Sierra Nevada Aquatic Research Labora- freezing; stream discharge declines progres- tory, University of California at Santa Bar- sively during this period. Later successional bara. Scott D. Cooper, Frank F. Hooper, species of periphyton are relatively more Allen W. Knight, and Keith V. Slack reviewed abundant in summer than in late spring, and the manuscript. 610 Great Basin Naturalist Vol. 46, No. 4

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