An in situ bioassay experiment using Diacyclops bicuspidatus thomasi, Daphira rosea, Diaptomus novamexicanus, and Holopedium gibberum single-species treatments was conducted to assess the influence ...of these zooplankters on the ciliate community structure of Castle Lake, California. At peak ambient abundances for adult individuals, these zooplankters all strongly depressed ciliate population growth rates. The ranking of the zooplankton-imposed ciliated death rates, from least to most severe, was Holopedium << Daphnia = Diaptomus <<< Diacyclops. The ranking of ciliate-taxa-response death rates to the zooplankton treatments was Halteria = Mesodinium < Askenasia = Urotricha = (Askenasia <) Strobilidium << Strombidium. As total ciliate abundance was depressed by the zooplankton treatments, the relative frequency of the small ciliates $(\thicksim 5,000 \mu m^3)$ increased, and the relative frequency of the larger ciliates $(\thicksim 20,000 \mu m^3)$ decreased. These results suggest that both seasonal and long-term shifts in zooplankton community structure have the potential to dramatically alter the dynamics and structure of ciliate communities.
Monthly diel monitoring studies for phosphorus content were conducted (1995–1996 period) for multiple stations on Incline Creek, a mountain stream in the Lake Tahoe basin (California‐Nevada). Large ...discharge and particulate P (PP) concentration fluctuations occurred during June in the early evening as snowmelt from higher elevations arrived at the lower stream reaches. June diel dissolved organic P (DOP) concentrations steadily increased, while soluble reactive P (SRP) concentrations remained constant. June diel PP concentrations associated with sand‐sized particles (PPsand: >63 μm) exhibited a clockwise hysteresis, indicating possible sediment source depletion on a daily timescale. June diel PP associated with silt‐ and clay‐sized particles (PPSC: >0.45 μm and <63 μm) exhibited counterclockwise hysteresis behavior, suggesting a potential groundwater contribution to PPSC. PPSC comprised the majority of PP concentration, except during high‐discharge events when PPsand concentration was dominant. Areal PP loading, specifically PPsand, appears to originate primarily from the lower eastern branch of Incline Creek during the spring snowmelt season. Possible sources include a ski resort/parking lot and a golf course. DOP and SRP areal loads were greatest from the undeveloped upper subwatershed, suggesting that natural factors such as slope are influencing loading of small‐sized P fractions.
We examined whether seston food quality was a significant factor to predict zooplankton, specifically Daphnia pulex, biomass dynamics in Lake Berryessa, California, U.S.A. The seston composition ...changed dramatically during the study period. Total macrozooplankton to seston biomass ratios were high during the springtime, as was D. pulex biomass. In monthly growth experiments using natural seston, eicosapentaenoic acid (EPA) concentration was best in explaining D. pulex growth, although α-linolenic acid (ALA) also showed considerable relationship with D. pulex growth. We built D. pulex growth models using combinations of EPA concentration, C:P ratio, and water temperature. The model using EPA concentration, C:P ratio and water temperature was best in explaining D. pulex biomass in springtime in Lake Berryessa. However, this model did not work for other seasons, suggesting that resource control via seston food quality was prevalent in springtime, but other factors may also become important in other seasons in this reservoir.PUBLICATION ABSTRACT
To investigate the potential for heterotrophic organisms to upgrade the food quality of seston, we performed decay experiments using a non-toxic Microcystis aeruginosa (cyanobacteria) monoculture. ...The experiment was performed in darkness with aeration using a microbial inoculum collected from a hypereutrophic pond. Chlorophyll a concentrations decreased throughout the decay experiment. In contrast, eicosapentaenoic acid (EPA, 20:5 omega 3) and docosahexaenoic acid (DHA, 22:6 omega 3) concentrations increased and peaked on Day 5, while alpha -linolenic acid ( alpha -LA, 18:3 omega 3) and stearidonic acid (18:4 omega 3) gradually decreased, suggesting that EPA and DHA might be converted from alpha -LA and stearidonic acid. Microscopic examination revealed that a heterotrophic nanoflagellate (HNF) and the ciliate Vorticella sp. dominated the biological community during this experiment. Further examination using scanning electron microscopy (SEM) identified the HNF as Paraphysomonas vestita ssp. vestita, whose biovolume was very strongly correlated with EPA concentrations. Size-fractionized fatty acid determinations carried out on Day 6 showed that approximately two-thirds of the seston's total EPA content was in the <5 mu m size fraction, which corresponded to the P. vestita size fraction. This size fraction also had a fatty acid content (relative to carbon content) 3 times higher than the 5 to 10 or >10 mu m seston size fractions.
Lake Tahoe is undergoing the initial stages of cultural eutrophication due to human alteration of the airshed and watershed. The lake's switch from nitrogen (N) to phosphorus (P) limitation has been ...attributed primarily to atmospheric N loading. This places an increased importance on controlling watershed movement of P to the lake. A stream water quality monitoring data set consisting of nine streams in the Lake Tahoe basin has been analyzed to characterize the spatiotemporal variation of P delivery to the lake. This data is from the Lake Tahoe Interagency Monitoring Program (LTIMP), which provides scientific data for planning and regulatory agencies to address environmental problems in the Lake Tahoe basin. Results indicate that P delivery (concentrations, loads) varies greatly at interannual, seasonal, and spatial scales. Annual and seasonal total P (TP) concentrations can vary up to three orders of magnitude in a given stream and are strongly associated with suspended sediment. Particulate P is the major form of P transported by Tahoe streams and was strongly correlated with percent surficial geologic deposits, which are primarily located near streams. Tahoe streams with the highest annual P concentrations often had the lowest annual P loads, and visa versa. P loading is greatest during the spring snowmelt (75% of annual average). Potential watershed parameters influencing P delivery to Lake Tahoe have been identified as precipitation, basin area, basin steepness, and road and human development coverage. Results also suggest that human development impacts on stream P loads are most prevalent during high precipitation years. Identification and quantification of stream sediment and P sources such as streambanks and impervious surface is necessary to aid in watershed restoration efforts.
Stocking of the dominant planktivore of Castle Lake (rainbow trout) was discontinued to examine the impact of food web interactions on zooplankton communities and inter— and intra—annual dynamics of ...ecosystem properties (light penetration, primary productivity). Dynamics of zooplankton and ecosystem processes were examined for 3 yr following the manipulation and compared to 2—3 yr of premanipulation data. Sampling of vertebrate and invertebrate planktivores documented shifts in other members of the zooplanktivore guild as rainbow trout declined. Reduction of rainbow trout densities led to compensatory responses in other components of the Castle Lake fish assemblage as brook trout and golden shiners increased in abundance. This compensation resulted in increased rates of vertebrate planktivory on daphnids within 2 yr after trout stocking was discontinued. Zooplankton shifts in response to discontinuance of trout stocking were more rapid, particularly an immediate increase in a previously rare invertebrate predator (Diacyclops thomasi). Other limnological parameters also responded rapidly following the manipulation: water transparency declined and primary productivity (PPr) increased. In addition, intra—annual patterns (i.e., seasonal development) and the vertical distribution (shallow vs. deep) of PPr appeared to be affected by the food web manipulation. Our results indicate that complexities of real food webs complicate the prediction of the outcome of food web perturbations. Reduction of the previously dominant planktivore (rainbow trout) led to increases in other zooplanktivores (Diacyclops, golden shiners, brook trout) that resulted in enhanced predation pressure on zooplankton herbivores. Our results also indicated that alterations in water quality parameters (transparency, PPr) in response to food web alterations need not necessarily be mediated through changes in the abundance of Daphnia, as strong limnological responses preceded reductions in Daphnia by a year. We hypothesize an alternative mechanism for food—web—induced changes in lake ecosystem dynamics: changes in water clarity and productivity can result when cyclopoid predation strongly affects micrograzers.
Because of major biochemical imbalances between plants and animals, ecological efficiency at this interface may have a major impact on overall energy flow in ecosystems. In order to study ...relationships between seston food quality and energy transfer between primary producers and herbivores, we conducted five microcosm experiments in Castle Lake, California, USA during the summer of 1996. We simultaneously performed life table experiments to determine the effects of highly unsaturated fatty acids (HUFA) on Daphnia rosea growth, reproduction and survival. The results of these experiments suggest strong energy limitation of D. rosea growth in Castle lake during the study. D. rosea production was coupled with primary production in Castle Lake and in the microcosm experiments. D. rosea production efficiencies, i.e., the ratios of D. rosea productivity to primary productivity, decreased towards the end of the summer. A food quality index based on phytoplankton species composition and seston carbon to phosphorus (C:P) ratio were good predictors of D. rosea production efficiencies. The predicted D. rosea production pattern based on phytoplankton composition and primary productivity matched the zooplankton biomass dynamics in Castle Lake during 1991. Life table experiments showed HUFA effects on D. rosea population growth rates, reproduction and survival in support of the HUFA limitation hypothesis.
BURDENS AND GRATIFICATIONS OF CAREGIVING Bulger, Michael W; Wandersman, Abraham; Goldman, Charles R
American journal of orthopsychiatry,
April 1993, Volume:
63, Issue:
2
Journal Article
Peer reviewed
The caregiving experiences of 60 parents of adults with schizophrenia were investigated for the presence of gratification; the role of the interpersonal caregiver-child relationship; and the effects ...of burden, gratification, conflict, and intimacy. Results indicate that relationships, as measured by intimacy and conflict, were more highly associated with burden and gratification than were severity of schizophrenic symptoms or degree of caregiving involvement. Implications for therapeutic interventions are discussed.
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