Nickel (Ni) is a metal that is anthropogenically enriched in aquatic settings. It has been reported as having three main modes of toxicity in freshwater animals (ionoregulatory disturbance, respiratory impairment, and the generation of oxidative damage), but there is little understanding of Ni toxicity in marine and estuarine environments. The mechanism(s) of Ni uptake and toxicity were investigated using three model species (adult green shore crab, Carcinus maenas; adult Atlantic killifish, Fundulus heteroclitus; early life-stages of the New Zealand sea urchin Evechinus chloroticus). In crabs, sea water protected against Ni accumulation and toxicity. In more dilute salinities, however, all three modes of Ni toxicity were identified at a sub-lethal level, with effects noted at Ni exposure levels as low as 8.2 µg/L, the US EPA environmental regulatory limit. In killifish, similar protective effects of SW were observed, however this species was much more resilient to Ni toxicity, with only minor changes in ionoregulation and oxidative stress noted, and no evidence of respiratory toxicity. Sea urchin larvae were found to be the most sensitive marine organisms to Ni toxicity yet reported, with a 96 h median effect concentration of 14.1 µg/L measured. Toxicity in this species was related to Ni impairment of calcium influx, consistent with proposed mechanisms of uptake observed in the other two models. Overall, the elevated ion levels associated with salinity were shown to be protective, suggesting a role for water chemistry in modifying Ni accumulation. However, physiology, which varies between species, developmental stages, and as a function of environmental salinity, also influenced organism sensitivity to Ni. These data contribute novel information regarding the relationships between water chemistry, Ni accumulation, and Ni toxicity, and as such, will be integral in the future development of predictive modelling tools for protecting marine and estuarine animals against environmental Ni. / Thesis / Doctor of Science (PhD)

Although nearshore macroinvertebrates are integral members of high mountain lentic systems, knowledge of ecological factors influencing their distributions is limited. Factors affecting distributions of nearshore macroinvertebrates were investigated, including microhabitat use and vertebrate predation, in the oligotrophic lakes of North Cascades National Park Service Complex, Washington, USA, and the conformity of distribution with a lake classification system was assessed (Lomnicky, unpublished manuscript; Liss et al. 1991). Forty-one lakes were assigned to six classification categories based on vegetation zone (forest, subalpine, alpine), elevation, and position relative to the west or east side of the crest of the Cascade Range. These classification variables represented fundamental characteristics of the terrestrial environment that indirectly reflected geology and climate. This geoclimatic perspective provided a broad, integrative framework for expressing the physical environment of lakes. Habitat conditions and macroinvertebrate distributions in study lakes were studied from 1989 through 1991. Distributions varied according to vegetation zone, elevation, and crest position, and reflected the concordance between habitat conditions and organism life history requirements. Habitat parameters affecting distributions included water temperature, the kinds of substrates in benthic microhabitats, water chemistry, and, to a limited extent, the presence of vertebrate predators. The number of taxa per lake was positively correlated with maximum temperature and negatively correlated with elevation. Forest zone lakes tended to have the highest number of taxa and alpine lakes the lowest. Substrates in nearshore microhabitats varied with vegetation zone. Organic substrates were more predominant than inorganic substrates in forest zone lakes. Organic substrates declined and inorganic substrates increased in the subalpine zone. There were virtually no organic substrates in alpine lakes. Taxa were placed into groups based on substrate preference. Ordinations indicated that the proportion of taxa in inorganic and organic-based substrate preference groups paralleled vegetation zone-substrate relationships. Lake water hardness and pH, as well as the presence of vertebrate predators affected the distribution of several taxa. Gastropods were limited to three forest lakes by their water hardness and pH requirements, and the dytiscid beetle, Potamonectes qriseostriatus appeared to be absent from forest lakes due, in part, to the pH requirements of this taxon. The distribution of three taxa (Taenionema, Ameletus, Desmona) appeared to be affected by the presence of vertebrate predators (salamanders and trout). Discriminant analysis was used to test the reliability of lake classification based on terrestrial characteristics. Discriminant analysis assigned lakes to categories based on similarities in kinds of substrates, substrate preference groups, and taxa. Strong concordance between both methods of lake classification supported the interconnection between terrestrial characteristics and processes and the abiotic and biotic conditions in lakes. / Graduation date: 1994

Thesis (M. Phil.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 100-125) Also available in print.

Thesis (M.S.)--Michigan State University. Dept. of Fisheries and Wildlife, 2008. / Title from PDF t.p. (viewed on Aug. 10, 2009) Includes bibliographical references (p. 64-68). Also issued in print.

The aim of the project was to determine factors which explain the distribution of macroinvertebrates in two Melbourne streams both drastically affected by urbanisation. A detailed description is given of Dandenong Creek, flowing through the south-eastern suburbs, and Darebin Creek, in the northern suburbs, emphasising stream features likely, or known, to influence the drift and benthic fauna. Faunal sampling was carried out in Dandenong Creek from June 1992 until July 1993, and in Darebin Creek from February 1995 until March 1998. Physicochemical parameters were also recorded. The collected data, together with previously existing data, were analysed using multivariate analyses: non-metric multi-dimensional scaling (NMDS); analysis of similarities (ANOSIM); matching biotic and abiotic variables using BIOENV, and principal component analysis (PCA). Various biotic and diversity indices were calculated in an attempt to identify the major factors responsible for the failure of the fauna to recover from previously more seriously degraded water quality. The contribution of drift to the colonisation potential in Dandenong Creek appeared to be impacted by retarding basins, underground barrel-draining and channelization. Results also indicated that increased conductivity adversely affected the fauna in the lower reaches of Dandenong Creek. It was concluded that in Darebin Creek, high nutrient levels, as well as other pollutants, had resulted in low macroinvertebrate diversity in both the drift and benthos. If, as this study suggests, faunal diversity is a valid measure of stream health, the following factors need to be addressed for catchment-wide, stream management: lack of riparian zone vegetation (increasing bank erosion and making the benthic habitat unstable, with greater temperature variability); control of stormwater runoff (flow variability, increased conductivity, nutrient levels, sediment loads, sewage effluent, industrial discharges and heavy metals), and to modify retarding basins to increase stream continuity.

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

Activities associated with agricultural land use intensification, one of the primary sources of anthropogenic stress to aquatic ecosystems, degrade freshwater stream health and present a significant challenge to resource managers in terms of monitoring and remediation. Biomonitoring of benthic macroinvertebrates, a common method of measuring the impact of anthropogenic stress on freshwater stream health, has been used to characterize the impact of agricultural activities. However, in order for this technique to be useful to resource managers in the protection of freshwater streams from agricultural degradation, reliable methods are needed not only to determine the impact of agricultural stress on benthic macroinvertebrate communities, but also whether agriculture best management practices (BMP's) mitigate those impacts ...

Thesis (M.S.)--University of Wisconsin--Stevens Point, 2007. / Includes bibliographical references (leaves 62-66).

Thesis (M.A.)--Humboldt State University, 2009. / Includes bibliographical references (leaves 58-61). Also available via Humboldt Digital Scholar.

Thesis (M. Sc.)--University of Canterbury, 2006. / Typescript (photocopy). Includes bibliographical references (leaves 79-84). Also available vis the World Wide Web.