Thomas H. Sibley

Relationships between Channel Characteristics, Woody Debris, and Fish Habitat in Northwestern Washington Streams

Abstract Relationships between large woody debris (LWD) and pool area or pool spacing varied with channel slope and channel width for streams in second-growth forests in northwest Washington. Pool spacing (expressed as the number of channel widths between pools) decreased as number of woody debris increased in both moderate-slope (0.02 < slope < 0.05) and low-slope (0.001 < slope ≤ 0.02) channels, but the relationship was stronger in moderate-slope channels. Percent pool was also more strongly correlated with woody debris volume in moderate-slope channels than in low-slope channels. Multiple-regression analyses showed that pool spacing and percent pool were correlated with an interaction term between LWD abundance and channel slope, suggesting that the influence of LWD on pool formation changes with channel slope. Analysis of pool-forming mechanisms indicated that low-slope channels are less sensitive to LWD abundance because pools are formed by mechanisms other than LWD when LWD abundance is low. Size of...

The adsorption of plutonium IV and V on goethite

Abstract The adsorption of Pu(IV) and Pu(V) on goethite (αFeOOH) from NaNO3 solution shows distinct differences related to the different hydrolytic character of these two oxidation states. Under similar solution conditions, the adsorption edge of the more strongly hydrolyzable Pu(IV) occurs in the pH range 3 to 5 while that for Pu(V) is at pH 5 to 7. The adsorption edge for Pu(V) shifts with time to lower pH values and this appears to be due to the reduction of Pu(V) to Pu(IV) in the presence of the goethite surface. These results suggest that redox transformations may be an important aspect of Pu adsorption chemistry and the resulting scavenging of Pu from natural waters. Increasing ionic strength (from 0.1 M to 3 M NaCl or NaNO3 and 0.03 M to 0.3 M Na2SO4) did not influence Pu(IV) or Pu(V) adsorption. In the presence of dissolved organic carbon (DOC), Pu(V) reduction to Pu(IV) occurred in solution. Pu(IV) adsorption on goethite decreased by 30% in the presence of 240 ppm natural DOC found in Soap Lake, Washington waters. Increasing concentrations of carbonate ligands decreased Pu(IV) and Pu(V) adsorption on goethite, with an alkalinity of 1000 meq/l totally inhibiting adsorption. The Pu-goethite adsorption system provides the data base for developing a thermodynamic model of Pu interaction with an oxide surface and with dissolved ligands, using the MINEQL computer program. From the model calculations we determined equilibrium constants for the adsorption of Pu(IV) hydrolysis species. The model was then applied to Pu adsorption in carbonate media to see how the presence of CO3−2 could influence the mobility of Pu. The decrease in adsorption appears to be due to formation of a Pu-CO3 complex. Model calculations were used to predict what the adsorption curves would look like if Pu-CO3 complexes formed.

Copper Dynamics and the Mechanism of Ecosystem Level Recovery in a Standardized Aquatic Microcosm

The Standardized Aquatic Microcosm (SAM) was used to assess the effects and behavior of copper at the ecosystem level. The concentration of algal cells and Daphnia magna, pH, dissolved organic carbon (DOC), and dissolved and ionic copper concentration were measured for 489 d and used to explain the recovery sequence of a community of organisms. The results indicate that a resistant algal species was crucial for initiating the recovery sequence in these microcosms and that the timing of D. magna blooms was variable but highly correlated with decreasing ionic copper. In order to explain copper toxicity and the success of the recovery phase, a stepwise analysis of the functional role of the resistant algal species Oocystis pusilla, and the tolerance of D. magna was undertaken. These process studies determined that O. pusilla was a suitable food for D. magna, and that this algal species could also act as a major ligand for copper, although sorption was probably important only for a limited time during the bloom. These studies also concluded that copper bioavailability controlled toxicity because it was shown that D. magna from the microcosms exhibited no resistance to copper toxicity, even though the dissolved copper concentration was 5 times the LC50 value (concentration lethal to 50% of the population). DOC and pH, which were controlled by algal metabolism, were probably important for decreasing ionic copper, which allowed the recovery sequence to begin. Additional studies showed that the microcosm-derived DOC was able to complex copper at low pH and that DOC was highly correlated with reduced concentrations of ionic copper.

Impact of Predation by Smallmouth Bass on Sockeye Salmon in Lake Washington, Washington

Abstract In the Lake Washington basin, run sizes of sockeye salmon Oncorhynchus nerka and other anadromous salmon species declined during the 1980s. Reduced survival of juvenile sockeye salmon in the lake suggested that increased predation may have contributed to the decreased run size. Introduced smallmouth bass Micropterus dolomieu were considered to be a potential cause of increased predation on juvenile salmonid populations. Ultrasonic tracking showed limited spatial and temporal overlap between smallmouth bass and juvenile sockeye salmon. Substantial overlap occurred only in the littoral zone during the migration of the sockeye salmon fry from the Cedar River into the lake and during the out-migration of smolts from the lake through the Lake Washington Ship Canal into Puget Sound. Salmonids occurred in smallmouth bass stomachs only during the out-migration of smolts from Lake Washington to Puget Sound. For smallmouth bass larger than 150 mm total length, juvenile salmonids constituted 28% of the diet...

Abundance and distribution of Neomysis mercedis and a major predator, longfin smelt (Spirinchus thaleichthys) in Lake Washington

Seasonal variations in the horizontal and depth distributions of Neomysis mercedis and longfin smelt (Spirinchus thaleichthys) were examined using night-time mid-water trawl and Bongo net samples collected in Lake Washington from July 1989 to February 1992. Mysid density varied spatially, seasonally and yearly. For example, during summer, and fall (odd years), mysid abundance was highest in the northern, and lowest in the southern sections of the lake, except in December 1991 when they were uniformly distributed. In fall (November 1990), mysid density was highest in the central basin of the lake. Furthermore, in winter of even years, highest mysid density occurred in the southern region of the lake, but in the central region in winter (February) of odd year. Longfin smelt horizontal distribution also varied seasonally. For example, density of the 1988 YC smelt (1+) was highest in the northern area of Lake Washington in summer but highest in the southern area in fall. During winter, distribution seemed random. The abundance of the 1990 YC smelt (YoY) was also highest in the northern section of the lake in summer, but highest in the southern section in fall; density remained high in the southern section in winter. But, by late spring when they were more than one year old, the distribution had changed such that highest abundance occurred in the northern and mid-section of the lake. By winter when they were about two years old and about to begin spawning, density had become highest again in the southern section. These suggest extensive movement of mysids and smelt from one area to another, perhaps driven by wind-induced water currents in the lake.Depth distribution patterns of mysids and smelt are discussed. Smelt were captured mainly in the shallow strata (8 m) of the lake during all seasons except during winter when they predominated at 50 m. Mysids were also mainly caught in the shallow strata of the lake during all seasons, although a significant proportion occurred at greater depths (> 30 m).The abundance of both species was positively correlated in spring and summer but negatively correlated in fall. A poor correlation was observed in winter. Negative correlation in fall was primarily due to the occurrence of mysids and smelt in different areas of the lake whereas poor correlation in winter was particularly due to their occurrence at different depths. Because of considerable overlap in the distribution of both species in the lake, mysids face a high risk of predation by smelt. This piece of information is consistent with the hypothesis that smelt control mysid abundance in Lake Washington.

Effects of selected organic compounds on radionuclide adsorption to sediments in freshwater systems

The roles of selected organic compounds on K/sub d/ (distribution coefficients) values of radionuclides in laboratory sediment-water systems was evaluated. The radionuclides /sup 57/Co, /sup 106/Ru, /sup 137/Cs, and /sup 241/Am were used as tracers in the experiments. Five organic compounds: 1)1-nitroso-2-naphthol; 2)1,10-phenanthroline; 3)acetic acid; 4)salicylic acid; and 5)EDTA were evaluated for their effects on the distribution coefficients of the four radionuclides. The results of the study confirmed that organic compounds can affect sediment-water distribution coefficients of radionuclides, however, the magnitudes and directions of these K/sub d/ effects are functions of both the physico-chemical properties of the radionuclide and the specific interactions of the radionuclide and organic compound within a given sediment-water system. The results emphasize the complex variety of interacting factors that can effect sediment-water distributions of radionuclides. Therefore, it is necessary in any adsorption study to characterize, as fully as possible, the chemical parameters of water and sediment that can contribute to the eventual results in any given system. (JMT)

Copper tolerance by the freshwater algal species Oocystis pusilla and its ability to alter free-ion copper

Abstract Previous studies with copper-stressed microcosms found that recovery was dependent on a copper-resistant algal species [Taub, 1989. Aquatic Ecotoxicology: Fundamental Concepts and Methodologies, pp. 47–92. Meador, J.P., Taub, F.B., Sibley, T.H., 1993. Ecol. Appl. 3, 139–155]. One algal species, Oocystis pusilla, was able to bloom in microcosms that had been devoid of organismal activity for several weeks due to the addition of copper at a high concentration (31.5 μM). In the present study, experiments were performed to characterize the range in tolerance of O. pusilla to copper, determine its growth under low and high pH regimes as a function of copper exposure, and to examine its ability to alter pH and ionic-copper activity (ICu) over time. Total-copper (TCu) concentrations up to 78.7 μM and ICu values as high as 0.9 μM had no negative effects on O. pusilla, indicating that it is highly copper-tolerant. The best growth for O. pusilla generally occurred in the range of 8–20 μM (total or dissolved copper), indicating a hormetic effect (enhanced response at intermediate concentrations). Even though its abundance was severely depressed in a TCu solution of 157.5 μM, this species was able to increase fourfold in 14 days. O. pusilla increased its numbers at a faster rate in high pH (≈9) solutions; however, it was able to propagate when pH was lower (≈7) and copper was high. These characteristics would allow this species to bloom in highly copper-stressed environments that would characteristically have a low pH. From this work, and related studies, we concluded that the primary mechanism allowing O. pusilla to reduce ionic-copper activity in culture solutions and microcosms was the release of organic copper-complexing ligands and that biomass sorption may have been important only at very high cell densities.

Feeding ecology of longfin smelt (Spirinchus thaleichthys Ayres) in Lake Washington

Abstract Stomach contents of longfin smelt collected in Lake Washington, 1985–1991, were analyzed to assess feeding habits. Copepod species dominated prey biomass consumed by young of the year smelt in summer whereas Daphnia, chironomid larvae, and copepod species were the most important prey in fall. Diet of 1+ smelt, expressed in terms of percent dry weight, consisted mainly of mysids, amphipods, and Daphnia. The mean number of mysids observed in smelt stomachs in this study was about 50% lower than in the 1960s. This change in smelt diet is related to changes that have occurred in the Lake Washington watershed, and in the zooplankton composition in the lake following recovery from eutrophication; a reduction in growth of smelt accompanied this.

Biometrical relationships, energy content and biochemical composition of Neomysis mercedis from Lake Washington

Morphometric relationships, caloric content and biochemical composition of Neomysis mercedis were determined for freshly caught mysids. Strong positive correlations between telson length, carapace length, dry weight, energy content and total length are described by the equations: Ln (Dry weight) = −5.02 + 2.57*Ln (Total Length), Telson Length = 0.13* Total Length, and Energy (Calories) = −37.13 + 4.85* Mean Total Length. Energy (4.92 cal mg−1 AFDFW), ash (8.61% dry weight) and total Kjeldahl nitrogen (10.6% dry weight) content are comparable to values reported for other species. A comparison of the length-weight relationship for N. mercedis with similar equations published previously for other mysid species indicated that the predicted mean dry weight at any particular length varied among species.

Accumulation of Am-241 and Cm-244 from water and sediments by Hyalella sp. and Tubifex spp

This paper reports on the bioaccumulation of americium and curium by freshwater invertebrates in laboratory experiments. Uptake by benthic invertebrates will affect both the biogeochemical cycling of these elements and the potential exposure of man through accumulation in aquatic food chains. Am and Cm isotopes are produced by nuclear reactions in commercial reactors and are major components of high level wastes. Both elements bind strongly to sediments which may be the principal source for uptake by benthic organisms in freshwater and marine environments. The principal objectives of this research were: (1) to determine the extent of bioaccumulation of Am and Cm for freshwater species; (2) to compare bioaccumulation from water with bioaccumulation from various types of sediment particles; and (3) to evaluate the similarities and differences in the behavior of Am and Cm.