Thesis (M.S.)--Utah State University. Dept. of Wildlife Resources, 1968. / Includes vita. Includes bibliographical references (leaves 68-71).

Thesis (M.S.)--Utah State University, 1968. / Title from title screen (viewed Aug. 14, 2009). Department: Wildlife Resources. Includes vita. Includes bibliographical references. Archival copy available in print.

No description available.

The lack of cost-effective, reliable sampling methods for many wetland characteristics hinders efforts to describe the structural and functional properties of wetlands. This study evaluated techniques for sampling the subsurface hydrology and invertebrates of freshwater wetlands. The depth of rusting on mild steel rods was compared with water well measurements to determine the reliability of rust depth as a predictor of subsurface water levels. An emergence trap and a benthic coring device were compared to determine the utility of each for sampling the invertebrate fauna of a wetland. Accuracy of the rods in estimating different water table measurements (average, lowest, most recent) and comparability of rod data (within sets of five rods) were investigated for different reference points on the rods, residence times, and wetland soils. The effect of the presence of vegetation in a soil low in organic matter on rod accuracy also was evaluated. The depth of lowest formation of a rust band on the rods predicted average and most recent water table depths in peat soil (r² for regressions of rust band depth on water table depth ranged from 0.71-0.95). Estimates of average water table depths were most precise for peat soil. Accuracy and precision were considerably lower in sand and clay soils, but significant relationships (P < 0.10) between depth of rust band formation and water table depth were found for all soils (r² values for sand and clay ranged from 0.13-0.55). The presence of vegetation had no effect on rod accuracy in the sand soil. Differences in rod performance between residence times were not apparent. However, a rod residence time of 4-6 weeks is recommended to balance the time necessary for adequate rust formation on the rods and to minimize the chance of exposure to large changes in water levels. A decrease in water table depth of approximately 40 cm in one month in the clay wetland caused a month lag time in rust formation. Differences in depth of rust band formation between the five rods within replicate sets were greatest for rods from clay (mean SD = ±7.9 cm). Variability of rust band measurements within replicate sets was lower in peat (mean SD = ±2.3 cm) and sand (mean SD = ±2.6 cm). The results indicated that the rusty rod technique has serious limitations and should be applied only in situations where the use of standard methods must be restricted. Emergence traps and a benthic coring device were used to sample the invertebrates of a freshwater, emergent wetland during late spring and summer, 1989. The fauna captured by each technique, disparities between the techniques in sampling certain taxa, and factors potentially affecting abundance estimates were examined. In addition, the efficiency of each technique, expressed as the number of samples required to achieve a desired level of precision, in estimating mean abundances of the dominant invertebrate group, the Chironomidae, was evaluated. Total and monthly estimates of insect family richness were higher for continuous sampling of emergence than for monthly core samples of the benthos. Emergence traps also caught a greater variety of the insect taxa inhabiting the wetland. The precision and efficiency of each technique in estimating abundances of the dominant group, the Chironomidae, varied between months and habitats (open water; vegetation). The variation was most likely due to the natural spatial and temporal variations inherent in invertebrate populations. The number of samples required (n[subscript r]) to estimate mean Chironomidae abundances for the entire summer, June-September, to a precision of D= 0.20 (equivalent to a standard error equal to 20% of the mean), varied between techniques. Fewer sampling stations would have been required to estimate mean adult abundances using emergence traps than would have been required for estimates of larval abundances using benthic core samples. Large numbers of benthic cores (27-208 individual cores per habitat) would have generally been required for both monthly and seasonal estimates of non-insect invertebrate abundances. Labor costs for processing emergence samples were about 30% of those for benthic samples. Subsampling of dominant groups in the emergence samples would have further reduced costs. Frequent sampling throughout a season, with several different techniques, is required to completely characterize the invertebrate community of a wetland. This study compared two quantitative techniques for sampling wetland insects. Continuous sampling with emergence traps provided higher estimates of insect family richness and more precise estimates of Chironomidae abundances at a lower cost per sample than monthly core samples of the benthos. / Graduation date: 1992

published_or_final_version / Zoology / Doctoral / Doctor of Philosophy

In near-shore marine environments, two of the most prevalent anthropogenic disturbances affecting ecosystem diversity and function are the invasion of exotic species, and the release of toxic chemicals. Estuarine and harbour environments worldwide are dually subjected to high levels of toxic disturbance and ever increasing rates of invasion, via activities such as boating and shipping. It is not clear, however, whether the success of invasive species is influenced by the presence of toxic contaminants in these impacted environments. In particular, nonindigenous marine species (NIS) may be advantaged in chemically disturbed environments if they are more tolerant of toxicants. This thesis examines whether nonindigenous and native sessile invertebrate species have differential tolerance to a common aquatic contaminant, copper (Cu), which has links to both the invasion process (via its use in antifouling paints and the vector of hull fouling) and the modification of recipient environments (via human-mediated pollution). A series of laboratory- and field-based experiments showed that the cosmopolitan invasive bryozoans Watersipora subtorquata, Bugula neritina and Schizoporella errata are highly tolerant of copper pollution. The larvae and adults of W. subtorquata and B. neritina in particular were able to survive and grow in copper-polluted environments far exceeding most observed real-world levels (< 100 /??g 1-1). These nonindigenous species also showed very strong postexposure recovery. In contrast, the co-occurring native bryozoans Celleporaria nodulosa and Fenestrulina mutabilis demonstrated comparatively low tolerance to copper, with markedly reduced survival and fitness under Cu contaminated conditions, and inferior recovery abilities post-exposure. These findings were further supported by a long-term manipulative field experiment, examining the effect that varying levels of Cu exposure have on the structure and diversity of developing sessile invertebrate assemblages. Cu exposure decreased native species diversity by up to 50%, yet had no effect on NIS numbers. Consequently, in the presence of copper contamination, NIS dominated sessile communities, often resulting in substantial changes to community structure. Important insights were also gained into the nature of metal tolerance in NIS. Toxicity studies on larvae of the introduced bryozoan Bugula neritina revealed intraspecific differences in tolerance to Cu, associated with the level of pollution experienced by the adult source populations. There was also evidence of fitness costs related with increased Cu tolerance. In summary, we have found evidence that the success of invasive species is influenced by chemical contamination. NIS may be advantaged in contaminated estuaries relative to native species and this may assist in their establishment and persistence in new habitats.

It can be difficult to disentangle the factors that determine population success in freshwater systems, particularly for organisms with disturbance-resistant life stages like aquatic invertebrates. Nevertheless, the effects of environmental variation and habitat structure on animal population success in wetlands are important for understanding both trophic interactions and biodiversity. I performed two experiments to determine the factors limiting crayfish (Procambarus fallax) and dragonfly (Family: Libellulidae) populations in wetland environments. A simulation of a dry-disturbance and subsequent sunfish (Family: Centrarchidae) re-colonization revealed that crayfish populations are sensitive to sunfish, while dragonfly naiads seemed to be limited by other drying-related factors. A second manipulation revealed that small-bodied fishes and habitat structure (submerged vegetation) shaped dragonfly communities primarily through postcolonization processes. / by Natalie Knorp. / Thesis (M.S.)--Florida Atlantic University, 2013. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

This research investigated the impact of invertebrates to four species of native aquatic macrophytes: V. americana, P. nodosus, P. illinoensis, and N. mexicana. Two treatments were utilized on each plant species, an insecticide treatment to remove most invertebrates and a non-treated control. Ten herbivore taxa were collected during the duration of the study including; Synclita, Paraponyx, Donacia, Rhopalosiphum, and Hydrellia. Macrophyte biomass differences between treatments were not measured for V. americana or N. mexicana. The biomasses of P. nodosus and P. illinoensis in non-treated areas were reduced by 40% and 63% respectively. This indicated that herbivory, once thought to be insignificant to aquatic macrophytes, can cause substantial reductions in biomass.

Species that are introduced outside of their native ranges are an important threat to biodiversity. In southwestern Alberta, Canada, sport and bait fish have been introduced into most waterbodies. I examined the effects of introduced trout and minnows on the distribution, demography and behaviour of larval long-toed salamanders through a combination of field surveys, laboratory experiments and an outdoor mesocosm experiment. Results from field surveys at 30 high-elevation (>1500m) lakes confirmed previous studies showing an allopatic distribution of trout and long-toed salamanders. The same pattern was also documented at 27 low-elevation (<1500m) ponds. In a mesocosm experiment, salamander survival was significantly reduced in ponds containing trout or minnows. Surprisingly, larvae exposed to minnows were 28-65% smaller than larvae in control ponds, suggesting strong interspecific competition for zooplankton prey. In a series of laboratory studies, trout preyed directly on salamander hatchlings and larvae, whereas minnows injured hatchlings but did not consume them. In laboratory aquaria, salamander larvae spent significantly more time within a refuge when exposed to minnow cues, but showed no behavioural response to trout. This confirmed my expectation that long-toed salamanders lack specific behavioural responses to trout, but respond generally to disturbances within the water column. Thus, direct predation and a lack of specific antipredator behaviour are among the likely mechanisms responsible for the observed allopatic distribution of trout and long-toed salamanders. My data also show that gape-limited fish reduce growth and survival of salamanders, perhaps more so than trout, through mechanism such as competition and behavioural alteration. / ix, 76 leaves : ill., map ; 29 cm.

M.Sc. (Zoology) / The Limpopo Province covers an area of 12.46 million hectares and these accounts for 10.2 per cent of the total land area of the Republic of South Africa. The province is endowed with abundant agricultural resources and it is one of the country’s prime agricultural regions noted for the production of fruits and vegetables, cereals, tea, and sugar. A key feature of the agricultural industry of Limpopo Province is its dualism. There are two distinct types of agricultural production systems. The large scale commercial farming system occupies approximately 70% of the total land area. The smallholder farms are located mostly in the former homeland areas and they cover approximately 30% of the provincial land surface area. The town of Thohoyandou, with its surrounding villages, is the area of greatest human concentration in the Luvuvhu Catchment and subsistence farming is about a third of the total agricultural component. It is important to study the effects of agricultural inputs (e.g. fertilizers and sediment loads) on aquatic ecosystems in order to fully understand the processes involved of these stresses on aquatic ecosystems. Knowledge of these impacts toward the environment and human health is often limited due to lack of capacity building, especially among small scale farmers. Ten bio-monitoring sites were studied on five systems in the Vhembe district. The sites were sampled during the low flow period of November 2011 and the high flow period of April 2012. Sampling sites were selected to present conditions in the Mutale, Mutshindudi and Tshinane Rivers upstream and downstream of the potential influence of small scale agricultural activities...