Known as Golden Algae in popular media, Prymnesium parvum causes harmful algal blooms. When stressed, it secretes increased amounts of toxic chemicals called prymnesins, which have resulted in major fish kills in Texas. Although many options exist for mitigation of blooms, a feasible protocol for control of blooms on large-scale impoundments has yet to be identified. Chemical control of P. parvum using six different enzyme inhibiting aquatic herbicides was explored in laboratory experiments. Of the six chemicals screened, one (Flumioxazin) was selected for further study due to a significant decrease in P. parvum cell numbers with increasing chemical concentration. It was applied to natural plankton communities during in-situ experiments (Lake Granbury, Texas). The first experiment was conducted during a period of P. parvum bloom initiation (March) and the second experiment conducted during a post bloom period (April). Experiments were carried out in 20 L polycarbonate carboys covered in 30% shade cloth to simulate natural light, temperature and turbulence conditions. Flumioxazin was additionally screened in the laboratory on the common game/forage fish bluegill sunfish (Lepomis macrochirus) for six weeks with weekly re-application of flumioxazin to treatment tanks. Cell counts via light-microscopy, showed the chemical flumioxazin caused significant decreases in P. parvum, but no significant differences in zooplankton abundance during the period of bloom initiation. However, significant decreases in adult copepods were observed during the post bloom period, most likely due to decreased light penetration and inhibition of the photosensitive mode of action, but no significant decreases in P. parvum. No significant effects of flumioxazin were observed on growth, survival or feed conversion ratio for L. macrochirus.

Abstract Polycyclic aromatic hydrocarbons (PAHs) are hydrophobic organic pollutants. Because of their highly hydrophobic property, PAHs easily absorbed by organic matters. They also display highly biological accumulation ability and toxicity. PAHs can interrupt organism¡¦s endocrine systems and some are considered bearing mutagenic or carcinogenic potentialities. Because of industrialigation, the extent of accumulated PAHs in the environment at present is significantly higher than those in the past. Therefore, while it is best to avoid further producing of these compounds if at all feasible; efforts to limit the introduction of these compounds into the environment by treating point pollution sources should always be made. The traditional approach to treat organic pollutants, including PAHs, in wastewater is mainly microbial based degradation. But recently due to its low cost and relatively high efficiency, treatment using aquatic plants combined with microbial degradation became popular. However, there have not much work done in using aquatic plant alone to treat PAHs. To study the sorption of PAHs by aquatic plant can provide information regarding the role of plant and microbial actions, and to enable such bioremediation technology more flexibile and feasible in application. Therefore, the forcus of this research is using plant solely to remove PAHs in a man-made wastewater. In this study, an aquatic plant, Ceratophyllum demersum, was used to sorb phenanthrene (Phe) with a continuous flow device. The competition effect in sorption by another PAHs, pyrene (Pyr), was also studied. In addition, another aquatic plant, Naja gramunea Del., was tested using the same system. In the batch experiment, the sorption kinetic constants of phenanthrene and pyrene for Ceratophyllum demersum are 0.19 and 0.22, respectively. Compared with Ceratophyllum demersum, Naja gramunea Del. has a higher kinetic constant. The sorption equilibrium constants of phenanthrene and pyrene for Ceratophyllum demersum are 1.36 and 19.24, respectively. Compared with Naja gramunea Del., Ceratophyllum demersum has a higher equilibrium constant for phenanthrene, but with a lower equilibrium constant for pyrene. A competition effect was observed by the delayed phenanthrene¡¦s saturation time by using pyrene as the possible background pollutant in the continuous flow system. Naja gramunea Del. was also applied in the same system for treating phenanthrene and pyrene in the same way. In conclusion, these two aquatic plants demonstrated great potentials in applications used for treating wastewaters containing PAHs due to low energy and cost of the device.

This study was to explore: Taiwan's aquatic products breeding of whether the seasonal price changes, the paper through the season factor into the dummy variable in inverse demand function, by percentage of RMS error (RMSPE) method to verify the good or bad of model , recognition of changes in the prices of aquatic products with seasonal.

Thesis (Ph. D.)--University of Oklahoma, 1999. / Includes bibliographical references.

<p> This thesis qualifies functional and ecological aspects of mucus trails deposited by <i>Elimia potosiensis</i> collected from the Meramec River. Freshwater snails are most often recognized for their significant role in river and stream ecosystem function as primary consumers and prey items. However, their form of locomotion is the most energetically expensive found in the animal kingdom. Found in large numbers and densities, <i> E. potosiensis</i> is capable of coating large swaths of substratum with carbohydrate- and protein-rich mucus. This has the potential to affect ecosystem function at the most basal trophic level both energetically, by contributing nutrients and energy to the surrounding water body, and functionally, as a sticky substance to which microheterotrophs become adhered. </p><p> In marine studies, researchers have found that bacteria can readily degrade gastropod mucus and that it can act as the basis for biofilm formation. There have also been studies that show unique employment of energy saving strategies by snails that use their trails to capture food items and to reduce production needs by following trails laid by conspecifics. Very little research has been conducted on freshwater gastropods. This study is the first to focus solely on the ecological and functional aspects of freshwater snail mucus. </p><p> For this study, collections of <i>E. potosiensis</i> were made from a single site along the Meramec River to qualify the effect deposited mucus has on the adherence of microalgae and its potential for formation of biofilms. Overall, mucus-coated surfaces significantly more particles in flow than non-coated surfaces. The water velocity at which a trail is laid was not found to have an affect on the thickness, adhesive ability or persistence of a trail. However, the water velocity in which a trail is incubated in stream does have effect on the adherence rate of a trail. In this study, it was found that this was most likely due to the fact that trails in high water velocity come into contact with more particles during a given period of time due, in part, to its higher carrying capacity.</p>

No description available.

No description available.

<p>Dover sole (<i>Microstomus pacificus</i>) is a commercially important, slope dwelling flatfish of the northeast Pacific coast. Its genetic diversity at the mitochondrial DNA control region appears substantially lower than another commercially important flatfish, Pacific sanddab (<i>Citharichthys sordidus</i>). I designed a comparative study along depth and latitudinal gradients using five flatfishes and one brotula. In the control region's left domain, genetic diversity of six species trended lower with increasing habitat depth at Palos Verdes: shallow species had high genetic diversity and deep dwelling species (ex. Dover sole) had low genetic diversity. This diversity gradient may follow decreases in mass specific metabolic rates as Dover sole grow, invade the oxygen minimum zone and assume higher tissue water content. The left domain from 64 Dover sole specimens was compared across 4 latitudinal locations. Genetic diversity trended higher with increasing latitude, possibly due to cold water emergence as biomass shift shallower with increasing latitude. </p>

The effects of pollutant burdens on natural cyclic patterns in aquatic ecosystems have been studied, to test the hypothesis that a parameter or parameters describing the <I>pattern of variation </I>in a single determinant, such as DO or pH, may be used to describe the status of a body of water more meaningfully than results from single spot measurements. In this study the background water quality in a Scottish and a Ghanaian lake was assessed, then <I>rafts </I>were built on the lakes (Myrtle Dam and Weija Lake respectively) creating three small lakes to test the effects of pollutant loads (<I>e.g. </I>organics and nutrients) on them. Laboratory investigations to study the behaviour of the pollutants on DO or pH cycles were carried out, and then a dynamic DO model was developed to describe the cyclic behaviour of DO. Finally, the model was used to investigate the effects of added pollutant burdens on the DO cycles. Water quality assessment of Myrtle Dam and Weija Lake by using the <I>Weighted Water Quality Index </I>proved that Weija Lake has doubtful quality with WQI 51, which needs improvement. Myrtle Dam WQI of 73 shows that the lake waters are unpolluted (or recovered from pollution). It is also well oxygenated at the surface and receives no toxic discharge. The <I>raft</I> experiments for Myrtle Dam and the Weija Lake have been used to demonstrate that, in the raft tubes, organic loadings do have effects on the oxygen cycles, and showed that there are two effects. One is that, with a small organic loading, the mean DO value dropped, then increased as the organic loading was consumed. The second is that the amplitude of the DO cycle increased as the organic loading increased from 2.5 to 5.0 mg L^-1 TOC for Myrtle Dam, and decreased for Weija Lake as the organic loading increased from 2.5 to 5.0 mg L^-1 TOC. The laboratory experiments in both Ghana and Aberdeen proved to be useful in explaining the effects of nutrients and trace elements on the DO cycles. It was evident that the higher the algal concentration, the greater was the DO cycle and 30% v/v (<I>c.a. </I>254 mg L^-1 chlorophyll 'a' content ≍ 17 g L^-1 biomass aqueous algal suspension) proved to be the most suitable concentration for investigations, because, with higher organic loadings, the 100% aqueous algal suspension proved to be too concentrated and caused total deoxygenation.

An experimental study was made of accumulation and loss of heavy metals by the aquatic moss Rhynchostegium riparioides and of the processes involved. The information gained were used to assess the effectiveness of this species as a monitor. Growth of Rhynchostegium continued throughout the year with peaks in spring and autumn. There were positive correlations between growth and water and air temperatures. Strong differences in growth rates in the four streams were not related to nutrient or heavy metal concentrations. Various patterns of mesh bag were tested as containers for transplanted Rhynchostegium to be used as a monitor. No significant differences in accumulation by moss were found between boulders or bags, or in accumulation with different patterns of bags. Accumulation was reduced slightly at the centre of bags packed with large quantities of moss. The physiology of Zn accumulation was also studied. A large part of accumulation (> 70%) in the early stages (< 12 h) was in a form readily exchanged for competing cations such as Ca and Ni; over longer time periods there was significant accumulation into a more tightly bound compartment. There was no evidence that uptake into this latter compartment was under the direct control of the plant's metabolism. There was differential accumulation of Cr(III) and Cr(VI) in laboratory experiments; during a case study it was possible to "predict" the speciation of Cr in the water by the concentrations accumulated by the moss. These results confirm that bryophytes are useful as monitors of heavy metal pollution in a wide range of circumstances. A range of such applications are outlined, along with recommendations for standard methods for using moss bags.