Genetics - Theses
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ItemBiological monitoring of the Yarra River macroinvertebrates, (December 1983 - December 1986)(University of Melbourne, 1990)This thesis details the first phase of a monitoring programme of the aquatic macroinvertebrates of the Yarra River which aims to detect and assess long term trends in the condition of the River and its tributaries. Spatial and temporal trends identified in the fauna over the first phase of this study are identified and related to various physico-chemical parameters and catchment activities. The project design of this study is assessed in terms of whether it appears to be able to meet the project objectives and whether it can be operated in a more efficient and effective manner. In addition, areas that require further investigation in lieu of the findings of this study are discussed. The condition of the macroinvertebrates was assessed by investigating faunal composition and structure through the use of diversity indices, multivariate analyses (direct gradient analysis, ordination and cluster analysis), and dietary analysis of selected taxa. Observed spatial changes in the communities were associated to physico-chemical data by describing any patterns observed and by using a step-wise discriminant analysis. The frequency of structural abnormalities in two species of chironomids was assessed as a means of determining whether they were stressed by toxic contaminants, and the value of this technique in biological assessment is also evaluated. The macroinvertebrate fauna was quantitatively sampled at nine locations on the Yarra River (Upper Yarra, Upper Woori Yallock, Lower Woori Yallock, Healesville, Coldstream, Warrandyte, Alphington and Dights Falls) and one location on Woori Yallock Creek (Yarra!ock) on seven occasions between December 1983 and December 1986. The analyses indicated that a considerable deterioration exists in the condition of the fauna progressively downstream and was associated with water quality (nutrients, turbidity, organic enrichment, and toxicants at Alphington) and physical characteristics of individuals sites (water depth, the type of substratum and surrounding riparian vegetation). Specific findings included: . A large faunal change was apparent between riffle sites at Upper Yarra and Upper Woori Yallock, possibly due to higher levels of nutrients and the more open riparian vegetation present at the Upper Woori Yallock site. . A considerable change in the fauna occurred between pool sites at Healesvilie and Coldstream: a more depauperate Coldstream fauna was attributed to increased organic enrichment and turbidity levels, which probably originated from Olinda Creek. . Considerable differences were found between the faunal composition of the Warrandyte pool site and that of other pool communities upstream. Although nutrient and turbidity levels were higher at Warrandyte, the faunal changes were primarily attributed to physical differences, in particular the study area at Warrandyte had greater water depth and less organic material than upstream pool sites. . The macroinvertebrates communities at Alphington appeared to be markedly more stressed than those of the pool communities investigated. Some changes can be attributed to the physical condition of this site, but the very low numbers of taxa recorded and the high frequency of abnormal mandibles and menta detected in populations of the chironomid Polypedilum tonnoiri from this site, strongly suggest that one or more toxic substances may be also stressing the fauna. - The high flows that prevailed in the Yarra from July to December 1986 appeared to have a large impact on the number of taxa and individuals present at most of the lowland sites. The way in which the fauna responded to these high flows varied between sites as a result of their different physical attributes and whether or not the high flows had a large impact on water quality. - The fauna at Yarra!ock on the Woori Yallock Creek appeared to be primarily affected by high turbidities and nutrient levels and it was not possible to elucidate the impact of toxic pollution, although biocides were widely used in the catchment for various types of intensive agriculture. It is likely that future monitoring of the Yarra River macroinvertebrates will be successful if: . Eight replicates continue to be collected from each site sampled. . The fauna from both the pool and riffle habitats continue to be monitored (as they provide a broader insight into the various factors influencing the condition of the fauna than assessing only one type of habitat). . The fauna is also collected during February/March (when the fauna may be most stressed by various water quality parameters), in addition to the fauna being sampled between April to June and late November to January. . The frequency of structural abnormalities in selected species continue to be monitored (as it is a unique means of determining whether or not the fauna appears to stressed by toxicants). . That the macroinvertebrates of the major tributaries are surveyed to determine what impact they these tributaries may have on the condition of the Yarra River. Highest priority should be given to those streams that appear to be strongly influencing the condition of the Yarra River. . that additional sites be located in areas where there appeared to be a large change in the condition of the fauna. - Several areas for future investigation have been identified that will help substantiate whether the factors that appeared to be influencing species abundance and distribution are in some way responsible for the changes observed in the fauna. These areas are: . An assessment of the benthic flora. . An investigation of the microdistribution of the fauna, particularly in relation to the importance of near-bed flows. . Research into the taxonomy of groups that are currently not well known, particularly those groups that appear to sensitive to changes in the condition of the stream (eg Oligochaeta). . An investigation of the relationship between the amount of sediment and the abundance of individuals in an airlift sample. . An assessment of the importance of drift at certain sites where it could help explain variation in species diversity and abundance. . An investigation of the impact of turbidity on macroinvertebrate composition and structure. Furthermore, there is a need to determine the importance of rare taxa in interpreting the invertebrate data as this may influence whether subsampling and some techniques used to assess the data can be used in future monitoring of the Yarra macroinvertebrates.