The ecological effects of mine effluents on the South Esk River were investigated over 2 years on a 170-km section of the river. Quantitative samples of benthic macroinvertebrates were collected at eight sites (three above the trace metal inflow and five below) using an air-lift sampler. Drifting fauna were also collected in the river adjacent to the point of trace metal inflow and in a tributary entering the contaminated section. As far as 80 km downstream from the source of trace metals; the numbers of individuals and the numbers of taxa were reduced in relation to upstream sites. From the 29 most commonly occurring taxa, three groups have been defined by clustering strategies: (a) taxa that were abundant at both contaminated and uncontaminated sites (a leptocerid caddisfly and a baetid mayfly); (b) taxa that were most abundant at sites upstream of the contaminated section of river (two mollusc species, four species of leptophlebiid mayfly and five species of caddisfly); (c) taxa whose numbers were highest at sites below the source of contamination (six dipteran species, four species of caddisfly, one mollusc species, one amphipod species and one species of water mite). Factors likely to be important in determining the harmful effects of trace metal contamination in the field include the particular metals under consideration, flow rate and stability of the substrata. There is little agreement between the acute lethal concentrations of metals determined by other workers in laboratory studies and the concentrations found to produce harmful effects in the South Esk River. The multivariate approach proved to be a sensitive means for the detection of trace metal contamination. Thecomposition of the drifting fauna was also altered by the trace metal contamination. Thenumbers of rhyacophilidcaddisflies were higher in the contaminated section of river and those of the baetid mayflies and helminthid beetles were lower.

Ecological effects of mine effluents on the South Esk River, North-eastren Tasmania. III. Benthic Macroinvertebrates.

The vegetation associated with sandy alkaline pans and surrounding acidic peats in south-west Tasmania is described. The upper margins of the pans are characterized by sharp environmental discontinuities, with pH changes of more than 3 units in only 20 cm being recorded. Classification and ordination of quadrats by plant species associated with a typical pan showed that five distinct communities are evident, but that these form a gradational series which reflects the altering edaphic status of the sites during infilling of the pans. The pH, drainage and redox characteristics of the substrates are among the factors determining the frequency of particular species at any stage of the progression. Frequency histograms for plant species in and around the pans indicate that many of the species respond individually to changing pH.

Vegetation of an alkaline pan — acidic peat mosaic in the Hardwood River Valley, Tasmania

In 'Jonathan' apples grown in Israel, the incidence of senescent breakdown after 5 months of storage at 0C was not correlated with total or water-soluble Ca content at harvest. Likewise, no other assayed component of the water-soluble or total mineral content (P, Mg, K) of the fruit pulp at harvest correlated with the disorder after storage. After storage, a general decrease in the solubility of Ca was observed. However, this decrease was not uniform in all fruit and, as a result, the correlation between water-soluble and total Ca content, which was high at harvest, diminished after storage. Water-extractable Ca from stored fruit was negatively correlated and water-soluble K/Ca was positively correlated with the incidence of senescent breakdown, whereas total Ca was not correlated. Low Ca concentration s in apple at harvest have often been associated with fruit susceptibility to senescent breakdown, a disorder that may develop during cold storage (Dewey et al., 1981; Fukuda, 1972; van Goor, 1971; Ratkowsky and Martin, 1974). However, fruit with low Ca concentrations do not always show breakdown (Perring and Preston, 1974), and breakdown has sometimes been reported in fruit with high Ca levels (Per- ring and Plocharski, 1975a). In such instances, low P appeared to be involved in the development of the disorder (Perring and Plocharski, 1975a). In previous experiments we observed that occurrence of senescent breakdown did not correlate with Ca or P levels in the fruit at harvest and the disorder was even aggra- vated by application of calcium phosphate (unpublished results). One possible explanation for this apparent inconsistency with re- gard to Ca is that the physiological disorder is related only to a certain fraction of the cell Ca, which is not always directly cor- related with total content. This possibility was suggested previ- ously in relation to bitter pit, another storage disorder (van Lune

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Senescent Breakdown of 'Jonathan' Apples in Relation to the Water-soluble Calcium Content of the Fruit Pulp before and after Storage

SummaryExperiments with Cleopatra apple trees growing on Mailing 7 rootstocks in pot culture were conducted over a period of seven years. The trees were subjected over the years to a wide variety of treatments related to the nutrient supply, consisting of various levels and combinations of calcium, magnesium, phosphorus, nitrogen and potassium. The study considered the influence of nutrition on the mineral element composition of the fruit and on the storage disorders bitter pit, breakdown, scald and fungal rotting. Statistical analysis of the results indicated a predominant role for calcium in inhibiting bitter pit development, and also showed that calcium was the only mineral element of importance as an indicator of other storage disorders. Under conditions of adequate nutrition, a direct role for magnesium and potassium is unlikely. Principal component analysis, followed by varimax rotation of the first three component axes, proved to be a most useful mathematical technique for studying interrelationshi...

The Predominant Role of Calcium as an Indicator in Storage Disorders in Cleopatra Apples

SummaryMerton Worcester apple trees in pot culture were supplied for four consecutive years with N, P, Ca and K at two rates. Apples of this cultivar differed from those of cvs Cleopatra and Jonathan both in their response to nutrient supply variations and in the interrelationships among the levels of mineral elements in the fruit and bitter pit incidence at harvest. The association between fruit levels of N, P, K and Mg previously observed in the other two cultivars was absent in Merton. In two years a positive association appeared in Merton between K level and bitter pit incidence. Doubling the K supply reduced fruit Ca level and increased protein N level and bitter pit incidence. A threefold increase in the Ca supply had the opposite effect on each of these variables. Bitter pit incidence was not affected by doubling the P supply, but was increased by supplying extra N, some of which was in the form of ammonium ion. The differences found between Merton Worcester and the two cultivars studied previously...

The Effects of Increasing the Supply of Nitrogen, Phosphorus, Calcium and Potassium to the Roots of Merton Worcester Apple Trees on Leaf and Fruit Composition and on the Incidence of Bitter Pit at Harvest

The use of principal component analysis, followed by rotation of a reduced number of component axes, and its role in the identification and interpretation of relationships between disorder and mineral content in apple research is described. The relationship among bitter pit incidence, calcium deficiency and mean fruit weight per tree is illustrated by using data obtained on Jonathan apples from potted trees. Principal component analysis must be performed on unstructured data, and emphasis is placed upon the removal of treatment and block effects when constructing the correlation matrix upon which the analysis is performed. The mathematical techniques described are applicable to a wide range of agricultural experimentation.

D Martin

Papers

The use of multivariate analysis in identifying relationships among disorder and mineral element content in apples