Vessel-related contamination of Southern California harbours by copper and other metals

A number of trace contaminants appear to be introduced to nearshore marine waters as a result of vessel-related activities. Such inputs are clearly reflected by elevated concentrations of these constituents in several tissues of the bay mussel Mytilus edulis. Comparative studies using this bioindicator suggest that harbour-related activities can be as important a source as coastal wastewater discharges in the contamination of nearshore marine ecosystems.     

Government assistance and the changing distribution of dairyfarming in Australia

An important proportion of Australian dairy production has been destined for export markets, where prices are below those received on the home market. This degree of dependence on international prices has adversely affected dairy farm incomes and thereby influenced both Government responses to the industry's problems and dairymen's decisions about levels of production and farm viability. Examination of the spatial impact on the now declining Australian dairy industry of Government-funded subsidies and of schemes for reconstruction of non-viable dairy farms, has indicated that withdrawal of farmers from the industry has not been areally uniform at the national level; but study of a major dairying region whose industry has undergone substantial decline suggests that this uneven pattern reflects industry and regional characteristics more than the deliberate or inadvertent results of Government intervention. Although Government policy has been broadly directed towards reducing the numbers of dairymen, and hence dependence on overseas prices for production surpluses, industry change has been greatest in regions where viable economic alternatives have been available for low-income dairymen.     

Sediment budget analysis of slope–channel coupling and in-channel sediment storage in an upland catchment, southeastern Australia

Slope–channel coupling and in-channel sediment storage can be important factors that influence sediment delivery through catchments. Sediment budgets offer an appropriate means to assess the role of these factors by quantifying the various components in the catchment sediment transfer system. In this study a fine (< 63 µm) sediment budget was developed for a 1.64-km² gullied upland catchment in southeastern Australia. A process-based approach was adopted that involved detailed monitoring of hillslope and bank erosion, channel change, and suspended sediment output in conjunction with USLE-based hillslope erosion estimation and sediment source tracing using ¹³⁷Cs and ²¹⁰Pb_ex. The sediment budget developed from these datasets indicated channel banks accounted for an estimated 80% of total sediment inputs. Valley floor and in-channel sediment storage accounted for 53% of inputs, with the remaining 47% being discharged from the catchment outlet. Estimated hillslope sediment input to channels was low (5.7 t) for the study period compared to channel bank input (41.6 t). However an estimated 56% of eroded hillslope sediment reached channels, suggesting a greater level of coupling between the two subsystems than was apparent from comparison of sediment source inputs. Evidently the interpretation of variability in catchment sediment yield is largely dependent on the dynamics of sediment supply and storage in channels in response to patterns of rainfall and discharge. This was reflected in the sediment delivery ratios (SDR) for individual measurement intervals, which ranged from 1 to 153%. Bank sediment supply during low rainfall periods was reduced but ongoing from subaerial processes delivering sediment to channels, resulting in net accumulation on the channel bed with insufficient flow to transport this material to the catchment outlet. Following the higher flow period in spring of the first year of monitoring, the sediment supplied to channels during this interval was removed as well as an estimated 72% of the sediment accumulated on the channel bed since the start of the study period. Given the seasonal and drought-dependent variability in storage and delivery, the period of monitoring may have an important influence on the overall SDR. On the basis of these findings, this study highlights the potential importance of sediment dynamics in channels for determining contemporary sediment yields from small gullied upland catchments in southeastern Australia.     

Microchemistry of small desert varnish samples,western New South Wales,Australia

The chemistry of varnish scrapings from within and adjacent to rock engravings on sandstone outcrops in semiarid Australia was analysed using an electron microprobe (WDS mode). Small-area analyses were used to reduce potential contamination from identifiable within-varnish detrital grains and from substrate material. Ratios of (Ca + K):Ti were compared for rock engravings on older and younger rock surfaces, and between different engraving styles. Although ratios from varnish on the older surface were lower than for the younger surface, differences were not statistically significant. Sorting of analyses for potentially anomalous amounts of minor elements had little effect on the ranking of individual ratio values. Rankings of within-engraving ratio values were generally in accord with relative age expectations but differences between samples were not significant, with the chemical variability of varnish being high even without the contribution of discernible detrital inclusions. © 1998 John Wiley & Sons, Ltd.     

Distributed empirical algorithms to estimate catchment scale sediment connectivity and yield in a subtropical region

The intensity of soil loss and sediment delivery, representing hydrologic and geomorphic processes within a catchment, accelerates with rapid changes in land cover and rainfall events. An underlying component of sustainable management of water resources is an understanding of spatial and temporal variability and the adverse influences of regional parameters involved in generating sediment following widespread changes in land cover. A calibrated algorithm of soil loss coupled with a sediment delivery ratio (SDR) was applied in raster data layers to improve the capability of a combined model to estimate annual variability in sediment yields related to changes in vegetation cover identified by analyses of SPOT imagery. Four catchments in Kangaroo River State forest were assessed for annual changes in sediment yields. Two catchments were selectively logged in 2007, while the two other sites remained undisturbed. Results of SDR estimates indicated that only a small proportion of total eroded sediment from hillslopes is transported to catchment outlets. Larger SDR values were estimated in regions close to catchment outlets, and the SDR reduced sharply on hillslopes further than 200–300 m from these areas. Estimated sediment yield increased by up to 30% two years after land cover change (logging) in 2009 when more storm events were recorded, despite the moderate density of vegetation cover in 2009 having almost recovered to its initial pre‐logging (2005) condition. Rainfall had the most significant influence on streamflow and sediment delivery in all catchments, with steeply sloping areas contributing large amounts of sediment during moderate and high rainfall years in 2007 and 2009. It is concluded that the current scenario of single‐tree selection logging utilized in the study area is an acceptable and environmentally sound land management strategy for preservation of soil and water resources. Copyright © 2013 John Wiley & Sons, Ltd.     

Annual and spatial variation in the abundance length and condition of juvenile turbot (Psetta maxima L.) on nursery grounds on the west coast of Ireland: 2000–2007

Turbot (Psetta maxima Linnaeus) is a high value commercially exploited marine flatfish which occurs in European waters, from the Northeast Atlantic to the Arctic Circle, the Baltic and Mediterranean Sea. In Ireland, turbot are the most valuable commercial non-quota species. Very little is known about their population dynamics in the wild, in particular during the sandy beach nursery phase of the life history. In 2000, a survey was established to assess flatfish species on nursery grounds on the west coast of Ireland. Eleven sandy beaches were assessed for 0+ turbot by beach seining, over an eight year period (2000–2007) during the months of August and September. The objective of the study was to estimate juvenile turbot abundance and size structure to determine if any spatial and annual trends existed. Large scale variability in the recruitment of fish to nursery grounds may be indicative of fluctuations in the adult stock. Turbot were found to recruit to five beaches consistently over the eight year period. Temporal and spatial variability in the relative abundance and length of turbot was discerned, with no apparent overall trend. However, certain nursery grounds were shown in most of the years examined to support higher abundances of turbot in comparison to other areas over the eight year period. Turbot abundances on nursery grounds were significantly correlated with mean spring sea temperatures during the pelagic stage. The condition of turbot did not significantly differ on an annual or spatial scale. Mean densities of 0+ turbot along the Irish coast were found to be similar and at times higher than other areas in Europe, ranging from 0.1 (± 0.3) individuals 1000 m^− 2 to 18.5 (± 6.9) individuals 1000 m^− 2. Mean turbot total length on beaches ranged from 3.8 cm (± 0.6) to 6.6 cm (± 4.3). The observed spatial and temporal variability in abundance and length highlights the need for long-term studies when assessing juvenile flatfish populations. Results from the present study have provided much needed baseline data on wild juvenile turbot populations which is severely lacking for this species both on an Irish and on a European scale.     

Sediments as sources of DDT and PCB

Despite major decreases in DDT and PCB emissions over a three year period by the dominant discharger to a coastal marine site, only minor (and very similar) decreases were observed in concentrations of these pollutants in bottom sediments and flatfish from the outfall monitoring zone. These results illustrate how persistant such chlorinated hydrocarbons can be in the marine environment once the bottom sediments have been contaminated.     

Marble weathering in an industrial environment,eastern Australia

Qualitative evidence from monuments and buildings in industrialized countries indicates that rates of stone deterioration rise in the presence of urban and industrial pollutants. Measurements presented here on surface reduction of marble tombstones show that mean weathering rates have increased over the period 1885 to 1955. Weathering rates were lower before the establishment of sulfur dioxide-emitting plants. Marble weathering involved solution etching along grain boundaries and within individual grains, and proceeded by surface roughening and dislodgement of grains with little apparent accumulation of gypsum. Absolute surface reduction of marble was less than that recorded in industrial environments in Europe and North America.