Browsing by Author "Lowe, Rex L."

Now showing 1 - 4 of 4
  • Thumbnail Image
    Algal periphyton growth on nutrient-diffusing substrates: an in situ bioassay
    Fairchild, G. Winfield; Lowe, Rex L.; Richardson, William B. (Ecological Society of America, 1985)
    Differences in nutrient limitation for dominant species within an algal periphyton community were determined using additions of N and P supplied by nutrient-diffusing artificial substrates. Sealed clay flowerpots were filled with 2% agar and one of nine nutrient treatments (all combinations of K2HPO4 at 0.0, 0.05, and 0.5 mol/L with NaNO3 at 0.0, 0.05, and 0.5 mol/L). The pots were submerged at 0.5 m depth in Douglas Lake, Michigan, and diffused N and P to their outer surfaces in proportion to internal concentrations. After 51 d the pots were scraped and analyzed for attached algae. Total algal biomass as chlorophyll a on the pots ranged from 0.17 - 0.02 (SE) mg/cm2 for pots without added nutrients to 15.7 - 2.0 mg/cm2 for pots with K2HPO4 at 0.05 mol/L and NaNO3 at 0.5 mol/L. chlorophyll a on pots containing just P (0.05, 0.5 mol/L) increased 6- to 10-fold over controls. The diatoms Epithemia adnata and Rhopalodia gibba and the blue-green alga Anabaena increased significantly on the P-only pots; these species are suspected of N-fixing capability. Chlorophyll a on pots containing just N (0.05 mol/L) increased 1.5- to 2-fold, though this increase was nonsignificant; Achnanthes minutissima, Gomphonema tenellum, and Cocconeis placentula showed enhanced growth on these pots. Combinations of N and P caused heavy growth of the filamentous alga Stigeoclonium tenue. Naviculoid diatoms were also most abundant on the N + P pots. Average nutrient levels in Douglas Lake during the study were: NH3, 2.02 _mol/L; NO3, 0.44 _mol/L; and PO4, 0.06 _mol/L. The low ambient concentrations of both N and P, together with results of the periphyton bioassay, indicate that the two nutrients may jointly limit overall growth, and that the form of growth limitation differs by species within the periphyton community.
  • Thumbnail Image
    Diatom and protozoan community analysis and colonization on artificial substrates in lentic habitats
    Stewart, Paul M. (Virginia Polytechnic Institute and State University, 1985)
    The purpose of this research was to examine the colonization process and relationship of physico-chemical parameters to diatom and protozoan communities colonizing polyurethane foam (PF) artificial substrates in lentic habitats. This was the first study to utilize multivariate techniques for comparison of protozoan and diatom communities The following hypotheses were examined in this study: 1. diatom and protozoan species accrual is similar because the organisms are approximately the same size and share similar ecological conditions, 2. protozoan assemblages are influenced by the physicochemical parameters of their environment, and 3. diatoms and photosynthetic protozoans are more closely related to the physico-chemical parameters of their environment than are the protozoans of all trophic groups. PF substrates were placed in the littoral zone of lentic habitats. Substrates were sampled through a time series and examined for their diatom and protozoan species' presence-absences. The first hypothesis was tested by using the MacArthur-Wilson equilibrium model and by fitting the data to the model by non·linear least squares regression. Protozoan species accrual fit the model in most cases, while diatom species accrual did not. The second part of the research dealt with five lentic habitats in northern lower Michigan which were sampled as described above and concurrent with organismal sampling several physico-chemical parameters were sampled. These environmental parameters included pH, alkalinity, conductivity, temperature, and concentrations of dissolved oxygen, chloride, silica, ammonia, and total and ortho-phosphate. Protozoan communities were examined using reciprocal averaging ordination. It was found that the bog and marsh had distinct communities, while the three lakes did not. Several physicochemical parameters and factors correlated significantly with axes generated by samples in species space. The final section tested the degree of relationship among diatoms, autotrophic protozoans, and protozoans to the physicochemical parameters and factors. pH had the highest correlations with the first axes for each group. Diatom communities had the greatest degree of relationship to the physico-chemical parameters, evidence for this is provided by the greatest number of correlations between ordination axes and the physico-chemical parameters and factors.
  • Thumbnail Image
    Functional and pathological responses of selected aquatic organisms to chrysotile asbestos
    Belanger, Scott E. (Virginia Tech, 1985-09-01)
    Functional and pathological responses of larval, juvenile, and adult Asiatic clams (Corbicula sp.), juvenile and adult fathead minnows (Pimephales promelas), and egg, larval and juvenile Japanese Medaka (Oryzias latipes) to chrysotile asbestos were investigated in 96-hour to 91-day tests. Chrysotile significantly reduced siphoning activity and shell growth of adult clams and siphoning, shell growth, and weight gain of juveniles at 10⁵ fibers/liter during 30-day tests. Larval Corbicula suffered significantly greater mortality and lower release by brooding adults at 10²-10⁸ fibers/liter. Adult and juvenile Corbicula exposed to 10⁸ fibers/liter for 30 days exhibited deteriorated gill tissue and significantly greater tissue water content. Corbicula accumulated up to 1000 fibers/mg in visceral tissue at 10⁸ fibers/liter. Clams collected from the California Aqueduct System exposed to 10⁹ fibers/liter accumulated up to 10⁵ fibers/mg in viscera. Corbicula can be used as a monitor for chrysotile contamination due to its ability to concentrate fibers. Adult and juvenile fathead minnows did not suffer acute toxicity at 10¹² fibers/liter and differential mortality relative to controls up to 10⁸ fibers/liter for 30 days. At the conclusion of the 30-day tests the length, weight, and swimming performance of adult minnows exposed to asbestos were not significantly affected relative to controls. Juvenile minnows exposed to 10⁶-10⁸ fibers/liter had significantly lower weight. Fish exposed to 10⁸ fibers/liter for 30 days accumulated up to 390 fibers/mg in kidney tissue. Egg and larval Medaka were exposed to 0-10¹⁰ fibers/liter of chrysotile until hatching and for thirteen weeks, respectively. Eggs responded erratically to asbestos exposure and no conclusive trends could be drawn. Larval Medaka exposed to 10⁶-10¹⁰ fibers/liter had reduced growth by 14 days. Fish exposed to 10¹⁰ fibers/liter suffered 100% mortality by 60 days. Fish exposed to asbestos developed epidermal tumors, thickened epidermal tissue, increased mucous cell density in the intestinal tract, constricted kidney tubules, and abnormal levels of lipid and endoplasmic reticulum in the liver. Maximum asbestos uptake occurred in fish exposed to 10⁸ fibers/liter for 91 days (400 fibers/mg). The extent of damage to fish and clams at levels greater than 10⁴ fibers/liter in the laboratory suggests that aquatically transmitted asbestos is a potential hazard to these species in the field.
  • Thumbnail Image
    Population and community changes of attached-algae to zinc stress alone and in combination with selected environmental variables
    Genter, Robert B. (Virginia Polytechnic Institute and State University, 1986)
    Four experiments were performed to test the feasibility of using taxonomic composition and abundance of attached algae to identify treatments of zinc (Zn) alone and in combination with treatments of phosphate, snail grazing, and pH. In the experiment presented in chapter 2, three treatments of zinc (0.05, 0.5, 1.0 mg Zn•l⁻¹) and a control could be identified by different algal communities in outdoor, flow-through, stream mesocosms. Established communities were continuously exposed to Zn, and samples were collected on days 0, 2, 5, 10, 20, and 30 after treatment began. Experiments were conducted in spring, summer, and fall 1984. Control stream mesocosms could be identified by diatoms in all seasons. The 0.05 mg Zn•l⁻¹ treatment could be identified by certain diatom taxa being more abundant than in the control in all seasons and by a filamentous green·alga in summer and fall. The 0.5 mg Zn•l⁻¹ treatment could be identified a filamentous green alga in fall. The 1.0 mg Zn•l⁻¹ treatment could be identified by unicellular green-algae in all seasons and by a filamentous blue-green alga in summer. A similarity index (SIMI) indicated that Zn stressed samples generally became less similar to control samples as Zn concentration increased from 0.05 to 1.0 mg Zn•l⁻¹. Total biovolume·density of all taxa responded more slowly than did individual taxa in spring and failed to distinguish between Zn treatments in summer and fall. Zn bound to periphyton (microbial community on solid substrates) was more reliable than total Zn in water for identifying Zn treatments. Zn treatments as low as 0.05 mg Zn•l⁻¹ changed algal species composition. This conflicts with the criterion (0.047 mg Zn•l⁻¹) of the U. S. Environmental Protection Agency for the 24-hour average of total recoverable Zn. ln the experiment presented in chapter 3, individual and combined effects of phosphate (P) and zinc (Zn) on the abundance of dominant algae and protozoa in a community were observed. Nutrient·diffusing artificial substrates were colonized in Douglas Lake, Michigan, and then placed in laboratory microcosms containing one of five Zn treatments (control, 0.1, 1.0, 3.0, and 10.0 mg Zn•l⁻¹). After one week of exposure in the laboratory the substrates were scraped and algal and ciliated protozoan abundances determined. Ten of thirteen algae and five of eight ciliated protozoa responded to experimental treatments. Some algae (diatoms and green algae) and ciliated protozoa were stimulated by high P, some stimulated by intermediate P, and some inhibited by high P. One alga and four protozoa responded positively to Zn. Two algae and three protozoa responded to a significant interaction between P and Zn so that abundances were from 3 to 19 times higher than the added effects of individual P and Zn treatments. Total algal abundance was increased by high P and total protozoan abundance was increased by intermediate P but at control levels for high P. The number of protozoan species was increased by P. Total algal abundance was increased by · combinations of Zn P and the number of protozoan species was decreased by Zn P. Altered abundance by combinations of Zn and P had not been demonstrated for a community of algae and protozoa previously. Although concentrations of Zn were initially above the level considered safe by the U.S. Environmental Protection Agency, many factors may prevent Zn stress. In the experiment presented in chapter 4, effects of 0.5 mg Zn•l⁻¹ and snail grazing (400 snails m⁻²) on density of dominant algal taxa were examined using established (12-day colonization) periphyton communities in flow-through stream mesocosms with four treatments (Zn, snails, Zn and snails, control) for 30 days. Grazing and Zn similarly reduced the abundance of 5 of 10 dominant taxa during the first 10 days of treatment. Temperature may play a very important role in determining the effect of snail grazing on attached algal communities. Cold temperatures (< 15 C) may have inhibited snail grazing to the extent that abundance of four taxa increased to levels found in non·snail treatments. However, one diatom was more than twice as abundant in snail treatment over non-snail treatment -- apparently stimulated by the presence of snails during cold conditions; and two diaoms remained at low abundance in snail treatment despite rapid growth in non-snail treatment -- apparently inhibited or selected as a food source by snails during cold con- ditions. No algal taxa replaced the diatoms inhibited by 0.5 mg Zn•l⁻¹ in this October-November, 1984, experiment by day 10. This is in contrast to an experiment performed one month earlier, in September-October, in which a community characteristic of this treatment developed by day 5. Testing individual and combined variables that affect attached algal communities will enhance understanding of population dynamics in algal ecology and pollutant assessment. In the experiment presented in chapter 5, attached-algal communities were employed to test the US Environmental Protection Agency’s (USEPA) guidelines for zinc (Zn) and pH. The experiment was designed to determine whether algal community composition and abundance would be altered by (a) ph 6 or 9, (b) 0.05 mg Zn•l⁻¹, or (c) the combination of ph 6 or 9 and 0.05 mg Zn•l⁻¹. Stream mesocosms were continuously supplied with natural water from the New River, VA, USA. Established (12-day colonization) communities on artificial substrates were sampled on days 0, 5, 10, 20, and 30 after treatment began on 9 July 1985. Zinc and pH treatments changed algal community composition from diatoms and a filamentous blue-green alga to different diatom taxa, green algae, or a coccoid blue-green alga. Total algal abundance was moderately increased by pH 6 treatment. Treatments of pH 6 and 0.05 mg Zn•l⁻¹ significantly altered attached-algal community composition even though these levels are considered "safe' by the USEPA. The pH 9 treatment did not significantly alter community composition, most likely because ambient pH was near this level.