The reproductive ecology of the Tahoe sucker, Catostomus tahoensis, in Pyramid Lake, Nevada

The Tahoe sucker spawns in Pyramid Lake from April to August at lake temperatures of 11.7 to 22.7 C. The spawning population is comprised of a large lake spawning group and a numerically smaller river running group. The river running group is smaller in length and was not considered during this study. The sex ratio of sampled suckers significantly favored the females. This is the result of the longer life of females and greater mortality of males during spawning.   Pyramid Lake Tahoe suckers reach sexual maturity at two to three years of age; however, those in Lake Tahoe do not mature until four or five years of age. The size at sexual maturity is different in both populations, which suggests that size or rate of growth rather than age determines sexual maturity.   The fecundity of Tahoe suckers is positively correlated with fork length, weight, and age. Additional analysis showed that a better correlation occurred between fish size (either length or net weight) and total ovary weight. We believe that fish size is primarily correlated with total reproductive tissue produced and secondarily with fecundity. A comparison of the Pyramid Lake population and the Lake Tahoe population demonstrated that size, not age, is the most important determinant of Tahoe sucker fecundity.     

Population structure and ecological effects of the crayfish Pacifastacus leniusculus in Castle Lake, California

The recent appearance of the ""California crayfish,"" Pacifastacus leniusculus , in Castle Lake, California, and interest in its potential impacts on the lake ecosystem provided motivation for a study of the population structure and habitat use of this species and its effects on aquatic macrophytes. Mark-recapture studies indicated that the total number of adult (3 + yr or older) crayfish in the lake was ca 10,100 individuals, yielding an estimate of lakewide crayfish density in preferred crayfish habitats of 0.13 adults m -2 . Using mean body mass of individuals, we estimated that ambient biomass density was 5.9 g m -2 . Length-weight relationships determined for captured individuals were sex dependent, with males having greater body mass for a given carapace length. Length-frequency and weight-frequency diagrams indicated that P. leniusculus reaches larger sizes in Castle Lake than do populations of P. leniusculus in ultraoligotrophic Lake Tahoe. Population-wide, males were significantly larger in both carapace length and body mass than females. We also examined sex dependence of interhabitat differences in crayfish body size by comparing animals trapped in rocky areas with those from areas with macrophytes and soft sediments. No significant differences in overall body size were found between habitats, but a significant habitat-sex interaction term occurred because the sex-dependent size differences were more pronounced in sediment than in rocky areas. Exclosure and enclosure experiments indicated that crayfish had large but differential impacts on Castle Lake macrophyte species, as the abundance of two of the dominant species ( Chara sp., Potamogeton richardsonii ) declined in the presence of crayfish and, in one case, increased in exclosures. These effects occurred via both consumptive and nonconsumptive mechanisms. These studies indicate that and expanding population of P. leniusculus in Castle Lake may be producing sizable impacts on the littoral zone habitat.     

Life history of the cui-ui, Chasmistes cujus Cope, in Pyramid Lake, Nevada: a review

The cui - ui, Chasmistes cujus Cope, a member of the sucker family and endemic to Pyramid Lake, Nevada, is listed as endangered by the U.S. Fish and Wildlife Service. Cui - ui was once a major source of sustenance for native Americans, who have inhabited the Lahontan region for at least 11,000 years. The Northern Paiutes developed sophisticated fishing technology to harvest this resource. The original distribution of cui - ui was the ancient Lake Lahontan complex, but as a result of climatic changes it was restricted to the Pyramid – Winnemucca – Truckee system by the turn of the 20th century. Transbasin water diversions (1905 to present) have resulted in further restrictions of habitat. The species is now limited to Pyramid Lake and the lower Truckee River. Reproduction is from hatcheries as well as limited natural reproduction. Females produce more than 40,000 2 - mm eggs per year. The normal development is described from the unfertilized egg through 912 hours post - hatching, when the fry are actively feeding and approaching adult body form. The unusual feature of adult cui - ui morphology is the relatively large ventro - terminal mouth, with thin and obscurely papillose lips. Cui - ui grow slowly and may live 18 years or possibly much longer; females generally live longer and attain a greater size than males. The highest adult mortality probably occurs during spawning runs. At this time they are vulnerable to predation, stress, and sometimes environmental degradation. The highest larval mortality probably occurs from predation when they are planted or migrate into the lake. The trophic ecology of the species is poorly understood, but they are known to ingest algae and zooplankton. Spawning behavior is documented. At present, natural reproduction is probably still the limiting factor for the cui - ui population. Cui - ui composed less than one percent of the total fish in Pyramid Lake during 1975–1977. During 1982 the largest cui - ui spawning run (13,000) in recent years occurred. The activity of cui - ui in the lake closely resembles that of the Tahoe sucker being most active during the spawning season each spring. Cui - ui inhabit the inshore - benthic zone and the pelagic waters of Pyramid Lake (         

First documentation of Salmincola californiensis in Lake Tahoe, CA–NV, USA

Salmincola californiensis is a parasitic copepod in the Lernaeopodidae family that commonly parasitizes salmonid fishes ( Oncorhynchus spp.) by attaching near the fins and on gill filaments. Historically their distribution was limited to streams that emptied into the Pacific Ocean. During the summer of 2006, several rainbow trout ( Oncorhynchus mykiss ) captured in Lake Tahoe were infested with S. californiensis . This is the first known record of S. californiensis in Lake Tahoe.     

Habitat and distribution of pygmy rabbits ( Sylvilagus idahoensis ) in Oregon

Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 st1\:*{behavior:url(#ieooui) } /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} An investigation to determine the location and extent of populations of pygmy rabbits ( Sylvilagus idahoensis ) in Oregon, and to describe several biotic and physical components within communities that include pygmy rabbits, was conducted from October 1981 to September 1983. Of 211 sites suspected of supporting the species based on interpretation of museum records, aerial photographs, soil maps, and interviews with biologists and area residents, 51 exhibited evidence of being inhabited when examined in summer 1982. Soil and vegetation components were sampled at 15 sites occupied by pygmy rabbits and 21 sites adjacent thereto. At inhabited sites, mean soil depth (51.0 ± 2.3 cm), mean soil strength of surface (0.8 ± 0.2 kg/cm 2 ) and subsurface (3.8 ± 0.3 kg/cm 2 ) horizons, shrub height (84.4 ± 5.8 cm), and shrub cover (28.8 ± 1.4%) were significantly greater ( P 2 ), density of forbs (3.4 ± 0.6/1,000 cm 2 ), and cryptogam cover (2.4 ± 0.5%) were not. Except for the clay component of subsurface soils, texture of surface and subsurface soils were not significantly different between sites occupied by pygmy rabbits and adjacent sites. The affinity of pygmy rabbits for areas with greater shrub cover, shrub height, soil strength, and soil depth, and, to a small degree, coarser soil texture possibly was related to availability of forage, security from predation, and ease of burrow construction. Analysis of 472 samples of sagebrush ( Artemisia tridentata ) collected at and near sites inhabited by pygmy rabbits indicated their distribution was not dependent upon the presence of specific subspecies of sagebrush. A marked decrese in evidence of occupancy of sample sites and of pygmy rabbit activity at occupied sites in 1983 indicated that populations of pygmy rabbits were susceptible to rapid declines and possible local extirpation. Fragmentation of sagebrush communities poses a potential threat to populations of pygmy rabbits, but the severity of the threat presently is unknown.     

Status and life history notes on the native fishes of the Alvord Basin, Oregon and Nevada

Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 st1\:*{behavior:url(#ieooui) } /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Three fishes, two species of Gila, and an undescribed subspecies of cutthroat trout, are endemic to the Alvord Basin. Historically, the Alvord cutthroat trout, Salmo clarki ssp., inhabited the larger creeks of the basin but has been extirpated in pure form because of introgression with introduced rainbow trout, Salmo gairdneri. Gila boraxobius is restricted to the thermal waters of Borax Lake and its outflows in the northern part of the basin. This species is endangered because of alteration of its fragile habitat. The Alvord chub, G. alvordensis, is recorded from 16 localities throughout the basin, including springs, creeks, and reservoirs. Although G. alvordensis as a species is not in jeopardy, many populations are small and could be easily eliminated by habitat destruction or by the introduction of exotic fishes. Competition with exotic guppies, Poecilia reticulata, has extirpated the Thousand Creek Spring population of Alvord chubs. Both species of Gila are opportunistic omnivores, consuming primarily chironomids, microcrustaceans, and diatoms. The Borax Lake chub also consumed large numbers of terrestrial insects, but specialized feeding on molluscs was noted in the West Spring population of Alvord chubs. Borax Lake chubs spawn throughout the year; however, most spawning occurs in early spring. Borax Lake chubs mature at a small size, occasionally less than 30 mm standard length, and seldom live more than one year. Alvord chubs are typically much larger than the Borax Lake species and live at least into their fifth year.     

Timing, distribution, and abundance of kokanees spawning in a Lake Tahoe tributary

We counted kokanee spawners and carcasses every 1-7 days from mid-September through mid-November in 1991 and 1992 in Taylor Creek, a tributary to Lake Tahoe, California-Nevada. Less than 1% of the spawning run entered Taylor Creek before flow from Fallen Leaf Lake was increased on 2 October 1991; in 1992 the peak occurred on 30 September or 1 October after flows increased on 29 September. In both years spawners concentrated in the middle three of five stream reaches below the impassable Fallen Leaf Lake dam. From tab-and-recovery experiments, the average longevity of male spawners in the stream was 3.5 days in 1991 and 2.8 days in 1992, whereas the average female longevity was 2.0 days in 1991 and 2.3 days in 1992. Observed carcasses accounted for less than 10% of spawners counted, suggesting removal by scavengers or high predation on prespawners. An estimated 1928 males and 1309 females spawned in 1991, and 8021 males and 8712 females spawned in 1992. Our estimate of 3237 spawners in 1991 compared favorably to our estimate of 3520 ± 1474 prespawners staging in Lake Tahoe in mid-September. An index of kokanee abundance in Lake Tahoe has historically been based on 1-day surveys every 1 November since 1960; however, estimated total spawner abundance was 19 times higher than the annual index of 158 spawners in 1991, 141 times higher than the index count of 100 spawners in 1992. The index count and mean fork lengths of spawners (278 ± 10 mm [2 SE] for males, and 248 ± 3 mm for females) in 1991 and 1992 were the lowest on record.     

The marine red algae of Rodrigues (Mauritius,Indian Ocean)

This paper reports on the red algae of Rodrigues, collected in the framework of the Shoals of Capricorn Programme (10 September to 5 October 2001). In total 68 species are reported, of which 65 represent new records for the island. Although most taxa represent rather common species, which are generally widespread in the Indian and western Pacific Ocean, some are of special interest to algal systematists and biogeographers. Renouxia antillana is reported for the first time for the Indian Ocean. The presence of Renouxia also constitutes the first record of the order Rhodogorgonales for the entire Indian Ocean. A few species have interesting distribution patterns. Halydictyon sp. is restricted in its distribution to South Africa, Mauritius and Australia. Despite these interesting records, the red algal flora of Rodrigues is most remarkable by the absence of several ‘ubiquitous' species.     

New records and comprehensive list of the algal taxa of Utah Lake, Utah, USA

Utah Lake is a slightly saline ecosystem containing more than 700 algal taxa. During the past decade a total of 106 algal taxa has been found that has not previously been reported in this water. These new records are reported herein, together with a comprehensive listing of all algal taxa reported from Utah Lake to date.         

Distribution of the milliped Virgoiulus minutus (Brandt, 1841): first records from Mississippi, Oklahoma, and Texas (Julida: Blaniulidae)

Virgoiulus minutus (Brandt 1841) (Julida: Blaniulidae), the only indigenous representative of the family in the New World, occurs, or can be expected, in parts or all of 24 states east of the Central Plains plus the District of Columbia; it is documented for the 1st time from Mississippi, Oklahoma, and Texas. The northern-, southern-, and westernmost localities are in Berrien County, Michigan; Putnam County, Florida; and Angelina/Rusk Counties, Texas, respectively. New England, Utah, Wyoming, Canada, and Mexico are deleted from the range, and specific localities are reported to augment previous generalized citations; those from Mexico represent misidentifications of Nopoiulus kochii (Gervais, 1847), an introduced European species that is recorded from Mexico City, Distrito Federal. Records of V. minutus from Pennsylvania, Virginia, South Carolina, Georgia, Alabama, West Virginia, Ohio, Illinois, Michigan, and Missouri are the 1st definite localities from these states; a sample from ""Anechar,"" believed to be a misspelling of ""Arrochar,"" a neighborhood in Staten Island, is considered the 1st definite record from New York. The published statement of occurrence in Delaware in general is the only known record of an indigenous diplopod from this state.     

Littoral heterogeneity and diel behavior of white bass ( Morone chrysops ) and carp ( Cyprinus carpio ) in Utah Lake, Utah

Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 st1\:*{behavior:url(#ieooui) } /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Diel activity and association patterns of white bass ( Morone chrysops ) and carp ( Cyprinus carpio ) in Utah Lake, Utah, were studied over four 24-hr periods during August 1980. Fish were concurrently sampled from two adjacent littoral habitats. Significant differences existed in diel activity patterns in two of three size classes of white bass and in diel association patterns of white bass and carp between the two habitat areas. Differences in habitat structure, and in biological activity between the habitat types, are implicated as the primary determinants of overall diel activity of fish in these littoral areas.        

Microbial spatial heterogeneity in microbiotic crusts in Colorado National Monument. I. Algae

Spatial heterogeneity in visually similar sites under Utah juniper canopy in Colorado National Monument was examined. Sample sites were arranged in a transect 24 m long, such that distances between samples were 0.013 m, 0.03 m, 1.0 m, 12 m, and 24 m. Twenty-five taxa of algae were observed, mostly belonging to Cyanophyta. Algal density varied by more than an order of magnitude within the 46 samples examined. The coefficients of variation for each distance class were very similar, demonstrating that algal patchiness can be as significant on a scale less than 0.013 m as it is on a scale of 24 m. Goodall's random pairing analysis of spatial pattern supported this conclusion by indicating that the minimal area for sampling soil algal crust populations at this site was equal to or less than 0.013 m. Because of the microscale heterogeneity in algal communities in this study, we recommend that future researchers take composite samples if they wish to quantify algae of microbiotic crusts.     

Mass mortality of salamanders ( Ambystoma tigrinum ) by bacteria ( Acinetobacter ) in an oligotrophic seepage mountain lake

Of the 13 lakes in the central Wasatch Mountains with tiger salamander ( Ambystoma tigrinum ) populations, salamander mass mortalities occurred in four seepage lakes that experienced extensive lowering of the water levels during the summer. The largest of these lakes, the oligotrophic Desolation Lake, was studied to determine the cause of the mortality phenomenon. The recurrent annual mass mortality involved both breeding adults and young-of-the-year. Rate kinetics suggest that mortality rate doubles with a fivefold increase in the number of aquatic young salamanders. The proximate cause of the mass mortality was identified as a bacterium, Acinetobacter sp. Desolation Lake and a seepage lake that did not experience the mass mortality were studied for the presence of Acinetobacter . Both lakes experienced two bacteria cycles: the first in early summer involved gram-positive bacteria, and the second in late summer involved gram-negative bacteria (mostly coliform bacteria and Acinetobacter ). The mass mortalities were associated with the late-summer gram-negative bacterial bloom, and Acinetobacter was found in large numbers in Desolation Lake. Algae, as well as other photosynthetic plants, were not present in large numbers. Since these lakes are growth-limited with respect to nitrogen and not with respect to phosphate, and since Desolation Lake had extensive lowering of the lake level during the summer, the biological cycle of the lake is proposed to be due to atmospheric and sheep-produced nitrogen products within the watershed. In this unstable lake system, bacteria are primarily responsible for incorporation of nitrogen in the food chain. The timing of the cyclical events depends on total winter precipitation.     

Species composition and habitat associations of benthic algal assemblages in headwater streams of the Sierra Nevada, California

Despite their trophic importance and potential importance as bioindicators of stream condition, benthic algae have not been well studied in California. In particular there are few studies from small streams in the Sierra Nevada. The objective of this study was to determine the standing crop of chlorophyll- a and benthic algal species assemblages present in the small 1st- and 2nd-order streams of the Kings River Experimental Watersheds (KREW, watersheds of Bull, Providence, Duff, and Teakettle Creeks) and determine the associations of these measures with stream habitat. We collected samples of benthic algae from rock substrata in September 2002 (7 sites) and 2005 (the same 7 sites plus 5 additional sites). Habitat and water-quality data were collected concurrently. Chlorophyll- a values ranged from 0.2 to 3.2 mg ? m –2 . Chlorophyll- a in the Bull Creek watershed was generally lower than in the other watersheds. Benthic algal assemblages were dominated by diatoms and cyanobacteria. We collected 79 taxa of diatoms in 2002 and 126 taxa in 2005. Diatom taxa richness in individual samples ranged from 15 to 47. Nonmetric multidimensional scaling analysis of arcsine square-root transformed proportional abundances of diatoms identified 3 groups of sites. Bull Creek sites were generally different from other sites (group 1), and the sites from Bull Creek were different in 2002 (group 2) and 2005 (group 3). Five taxa appeared to be particularly important in distinguishing groups: Achnanthidium minutissimum , Cocconeis placentula , Eunotia incise , Eunotia pectinalis var. minor , and Planothidium lanceolatum . Elevation, water temperature, pH, specific conductance, and canopy were habitat variables correlated with the differences in diatom assemblages among sites. Our results provide a valuable baseline for future studies of benthic algae in Sierra Nevada headwater streams and will be particularly important in understanding the effects of different forest restoration management strategies being tested in the KREW project.     

Cryptogamic soil crusts: recovery from grazing near Camp Floyd State Park, Utah, USA

The effects of grazing on the cryptogamic and vascular plant communities at two sites near Camp Floyd State Park, Utah County, Utah, were studied. The grazed site was subject to heavy grazing up until seven years prior to the study. The ungrazed site within the park boundaries had been protected from grazing for 20 years prior to the study and had a well-developed algal-lichen-moss crust. We found that the algae of the grazed site had recovered in terms of degree of crusting. There were no significant differences in the algal communities of the two sites when prevalent species were used as blocks in the ANOVAR analysis. However, when major algal groups were used as blocks, the analysis was significant, with the more recently grazed site having lower algal frequency. This difference, together with a few compositional differences, indicates that, although the algal community seven years following grazing is very similar to the algal community free of grazing for 20 years, the seven-year site is still in the process of recovery and community development. The diatom collections had a higher density in the grazed site, though the difference was not significant. Recovery of the lichen and moss community was not complete. The lichen Collema tenax and the mosses Bryum pallescens and Tortula ruralis were all significantly more abundant in the ungrazed area. Total cover of the lichen and moss components of the soil crusts was significantly lower in the more recently grazed area. Vascular cover was also lower.     

Birds of the desert region of Uintah County, Utah

Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 st1\:*{behavior:url(#ieooui) } /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} The Common Loon, White Pelican, Double-crested Cormorant, recurvirostrids, and most grebes, waterfowl, gulls, and terns have become more abundant in Uintah County, Utah, since 1937 (Twomey 1942) due to the establishment of Pelican Lake and adjacent water bodies and the ponds and marshes at Ouray National Wildlife Refuge and Pariette Wetlands Wildlife Management Area. The incidence of herons, egrets, thrushes, nuthatches, and icterids has generally remained about the same since 1937. Diurnal raptors have largely declined in abundance in the desert region of Uintah County since Twomey’s (1942) study. Plovers, sandpipers, phalaropes, and the White-faced Ibis were generally less common in 1977–1982 than in 1937, perhaps chiefly due to their displacement from wintering grounds by human population expansion and agricultural and industrial development. The incidence of owl species remains constant. Most flycatchers, swallows, warblers, vireos, orioles, and emberizids have diminished in number since 1937, probably because of the shrinkage of their winter habitats in Latin America and the southwestern U.S. The Blue Grosbeak and Black-throated Sparrow were not recorded in Uintah County in 1937 but were found there during this study and may represent a range extension northward since 1937. The Blue-gray Gnatcatcher is more common now than in 1937 due to the northward extension of its range. The Starling and Rock Dove and, more recently, the Common Grackle, Great-tailed Grackle, and Cattle Egret have invaded Uintah County due to the expansion of their ranges. It is not clear why the Pine Siskin, House Finch, and most corvids are presently less common than in 1937.        

The marine green and brown algae of Rodrigues (Mauritius,Indian Ocean)

The marine benthic green and brown macroalgae of Rodrigues, collected during an expedition in October 2001, are documented and 18 of the 60 taxa of Chlorophyta (53 species) and 18 species of Phaeophyceae are illustrated. Fifty taxa of green and 12 taxa of brown algae are added to the existing species list of the island. Turf algae and smaller epiphytic species are not or are only sporadically included in this study. All records are listed with bibliographic, biogeographic, taxonomic and nomenclatural comments. Infrageneric identification keys are included. The new combination Caulerpa mexicana var. exposita is proposed and the discovery of a new Udotea species is mentioned. The algal flora of Rodrigues is of a typical Indian Ocean composition but appears to be relatively poor when compared to the nearby island of Mauritius.     

Environmental interaction in summer algal communities of Utah Lake

Utah Lake is a shallow eutrophic lake in central Utah. It is characterized by high nutrient and silt loads and by large algal blooms in late summer and early fall. Phytoplankton samples and environmental data were taken from June through August 1974. Phytoplankton species were identified and then quantified in a Palmer counting cell. Environmental continuum theory was employed to describe algal succession, and regression analysis was used to discover interactions between algal communities and the environment. Phytoplankton communities in June were characterized by high species diversity. As the lake environment became stressed in late summer due to higher turbidity, nutrient levels, pH, and available inorganic carbon species diversity decreased. By August, the phytoplankton flora was composed essentially of only two species, Ceratium hirundinella and Aphanizomenon flos - aquae.     

Effects of 2,4-D on a Populus tremuloides community in the western United States-22 years after treatment

Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 st1\:*{behavior:url(#ieooui) } /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Quaking aspen ( Populus tremuloides Michx.) stands were accidentally sprayed with 2,4-D in a sagebrush control program in western Wyoming in 1958. We visited the site during the summer of 1981 to evaluate the long-term effect on the aspen trees and the associated vegetation. Initially, some observers believed that the aspen had been “destroyed.” Subsequent data indicate just the opposite—aspen stocking appeared to have been improved by the treatment. On two of the sampled clones, 22 years after spraying, there were approximately 17,000 more suckers/ha on the sprayed than on the unsprayed plots. These are adequate numbers to restock the site to pretreatment densities. Although undergrowth vegetation appeared to be changed as a result of the treatment, this cannot be attributed solely to the herbicide because heavy grazing, mostly by domestic livestock, has occurred on the grazing allotment. A similarity index was calculated between sprayed and unsprayed portions of the same aspen clones. Forbs were still less on the sprayed areas, whereas grasses were similar on the sprayed and unsprayed areas. Spraying apparently does not have as adverse an effect on aspen communities as some conservationists originally thought.