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Water Quality Problems (water + quality_problem)
Selected AbstractsHeavy metal concentrations during storm events in a rehabilitated industrialized catchmentHYDROLOGICAL PROCESSES, Issue 10 2003W. H. Blake Abstract Water quality data collected on a fortnightly or monthly basis are inadequate for assessment and modelling of many water quality problems as storm event samples are underrepresented or missed. This paper examines the stormflow dynamics of heavy metals (Pb, Cu, Cd and Zn) in the Nant-y-Fendrod stream, South Wales, which has been affected by 250 years of metal smelting, followed by 35 years of landscape rehabilitation measures. For storm events of contrasting (very dry and very wet) antecedent conditions in May 2000 and February 2001, respectively, temporal changes in streamwater heavy metal concentrations above and below an in-line flood detention lake are analysed. At the upstream site, peaks in total metal concentration were recorded on the rising limb for Pb (0·150 mg l,1) and Cu (0·038 mg l,1) but on the falling limb for Zn (1·660 mg l,1) and Cd (0·006 mg l,1) in the summer 2000 storm event, yielding clockwise and anticlockwise hysteretic loops respectively. In contrast, metal concentrations, although high throughout the winter storm event, were diluted somewhat during the storm peak itself. The Pb and Cu appear to be supplied by quickflow processes and transported in close association with fine sediment, whereas Zn and Cd are delivered to the channel and lake by slower subsurface seepage in dissolved form. In the winter 2001 event, antecedent soil moisture and shallow groundwater levels were anomalously high and seepage sources of dissolved metals dominated. Downstream of the lake, Pb and Cu levels and suspended sediment were high in the summer storm, but low in the winter storm, suggesting retention with deposition of fine sediment in the lake during the latter. In the winter storm, Zn and Cd levels were higher downstream than upstream of the lake, perhaps because of additional seepage inputs from the surrounding slopes, which failed to have an impact during summer. An understanding of the complex interplay of antecedent soil moisture and the dynamics of subsurface seepage pathways in relation to the three-dimensional distribution of sources is important in modelling heavy metal fluxes and levels in contaminated urban catchments. Copyright © 2003 John Wiley & Sons, Ltd. [source] The dynamics of unattached benthic macroalgal accumulations in the Swan,Canning EstuaryHYDROLOGICAL PROCESSES, Issue 13 2001Helen Astill Abstract It has been suggested that macroalgal accumulations may impact on benthic nutrient cycling by promoting remineralization of sedimentary nutrients, otherwise inaccessible, and act as sinks/sources for dissolved nutrients in the water column. However, little consideration has been given to the time taken for these impacts to occur, and if accumulations persist long enough in a region for impacts to occur. In this study, accumulations were characterized seasonally, according to biomass, height relative to water depth, and organic content of the underlying sediment, from November 1996 to August 1997, in the Swan,Canning Estuary. Persistence of accumulations was measured from late summer to mid-winter in 1997, by tagging individual plants and recording the time tagged plants persisted at 10 sites. In summer 1998, physicochemical profiles of accumulations were measured over 24 h, at two locations: one with relatively low sediment organic content (SOCn) (1·5% LOI) and one with relatively high SOC (6% LOI). Accumulations rarely exceeded 25 cm in height, regardless of water column depth, and ranged between 100 and 500 g dwt m,2. Macroalgae persisted between one week, in relatively well-flushed regions, to one month in areas with poor flushing. Over the entire diurnal period, almost 100% of incident light was attenuated at the bottom of all accumulations. Dissolved oxygen levels at the bottom of accumulations were generally depressed, particularly at night, with hypoxia (1 mg l,1) recorded at the high SOC site at 03 : 00 h. No significant differences in FRP concentrations (approximately 30,60 µg l,1) were recorded between sites, or within accumulation profiles. Ammonium levels were greatly raised inside accumulations at the high SOC site by 03 : 00 h (10 and 300 µg l,1, inside and outside, respectively). The results show that, where SOC is high, conditions within accumulations are affected. Impacts occurred within 24 h; well within the period for which accumulations persist. These results also indicate that regulation of hydrological regimes in estuarine systems may result in increased persistence of macroalgal accumulations, and associated water quality problems. Copyright © 2001 John Wiley & Sons, Ltd. [source] Current issues with fish and fisheries: editor's overview and introductionJOURNAL OF APPLIED ECOLOGY, Issue 2 2003S. J. Ormerod Summary 1.,By any measure, fishes are among the world's most important natural resources. Annual exploitation from wild populations exceeds 90 million tonnes, and fish supply over 15% of global protein needs as part of total annual trade exceeding $US 55 billion. Additionally, with over 25 000 known species, the biodiversity and ecological roles of fishes are being increasingly recognised in aquatic conservation, ecosystem management, restoration and aquatic environmental regulation. 2.,At the same time, substantial management problems now affect the production, exploitable stocks, global diversity, trophic structure, habitat quality and local composition of fish communities. 3.,In marine systems, key issues include the direct effects of exploitation on fish, habitats and other organisms, while habitat or water quality problems arise also from the atmospheric, terrestrial and coastal environments to which marine systems are linked. In freshwaters, flow regulation and obstruction by dams, fragmentation, catchment management, pollution, habitat alterations, exotic fish introductions and nursery-reared fish are widespread issues. 4.,Management responses to the problems of fish and fisheries include aquatic reserves in both marine and freshwater habitats, and their effectiveness is now being evaluated. Policies on marine exploitation increasingly emphasise fishes as integral components of aquatic ecosystems rather than individually exploitable stocks, but the rationalisation of fishing pressures presents many challenges. In Europe, North America and elsewhere, policies on freshwaters encourage habitat protection, integrated watershed management and restoration, but pressures on water resources will cause continued change. All these management approaches require development and evaluation, and will benefit from a perspective of ecological understanding with ecologists fully involved. 5.,Synthesis and applications. Although making a small contribution to the Journal of Applied Ecology in the past, leading work on aquatic problems and fish-related themes appear increasingly in this and other mainstream ecology journals. As this special profile of five papers shows, significant contributions arise on diverse issues that here include the benefit of aquatic reserves, river restoration for fish, the accumulation of contaminants, interactions with predators, and the fitness of salmonids from nurseries. This overview outlines the current context in which papers on the applied ecology of fish and fisheries are emerging, and it identifies scope for further contributions. [source] Evidence that channel catfish, Ictalurus punctatus (Rafinesque), mortality is not linked to ingestion of the hepatotoxin microcystin-LRJOURNAL OF FISH DISEASES, Issue 5 2002G S Snyder Catfish farms located in the south-eastern USA using brackish (3,5 g NaCl L,1) well water experience sporadic fish kills sometimes with high mortality. An investigation of three catastrophic losses occurring in this region identified no involvement of infectious diseases or traditional water quality problems, including oxygen, ammonia or nitrite. The high mortality and time course of the problem was indicative of exposure to a toxin. Attempts by other workers to explain the cause of this unique syndrome (high chloride associated toxicosis of catfish, HCTC), suggested that the losses might be because of microcystin-producing blooms of Microcystis aeruginosa, but our investigations failed to support this conclusion. We found that (1) the liver histology of catfish experimentally exposed to pure microcystin-LR is very different from that of catfish sampled during outbreaks of HCTC; (2) measurements of microcystin-LR concentrations in the three cases were far lower than the concentration required to kill catfish by experimental immersion; (3) the HCTC toxin appears to have a short half-life, whereas microcystin-LR does not; (4) experimental gavage of catfish with massive amounts of microcystin-LR does not cause the acute mortality typical of HCTC; (5) outbreaks of HCTC appear to be associated with heavy blooms of Anacystis marina, a halophytic cyanobacteria, not with blooms of M. aeruginosa. [source] EVALUATION OF COASTAL PLAIN CONSERVATION BUFFERS USING THE RIPARIAN ECOSYSTEM MANAGEMENT MODEL,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 6 2001Richard Lowrance ABSTRACT: Riparian buffers are increasingly important as watershed management tools and are cost-shared by programs such as Conservation Reserve that are part of the USDA Conservation Buffer Initiative. Riparian buffers as narrow as 4.6m (15ft) are eligible for cost-share by USDA. The Riparian Ecosystem Management Model (REMM) provides a tool to judge water quality improvement by buffers and to set design criteria for nutrient and sediment load reduction. REMM was used for a Coastal Plain site to simulate 14 different buffers ranging from 4.6 m to 51.8 m (15 to 170 ft) with three different types of vegetation (hardwood trees, pine trees, and perennial grass) with two water and nutrient loads. The load cases were low sediment/low nutrient-typical of a well managed agricultural field and low sediment/high nutrient-typical of liquid manure application to perennial forage crops. Simulations showed that the minimum width buffer (4.6 m) was inadequate for control of nutrients under either load case. The minimum width buffer that is eligible for cost share assistance on a field with known water quality problems (10.7 m, 35 ft) was projected to achieve at least 50 percent reduction of N, P, and sediment in the load cases simulated. [source] Effects of Periodic Feed Deprivation on Growth, Feed Efficiency, Processing Yield, and Body Composition of Channel Catfish Ictalurus punctatusJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 4 2005Menghe H. Li Two studies were conducted in 110-L flow-through aquaria and 0.4-ha ponds to evaluate effects of periodic feed deprivation on the growth performance of channel catfish Ictalurus punctatus. Fish were deprived of feed 0, 1, 2, or 3 consecutive d/wk, l d per 5-d period, or 3 consecutive d per 10-d period and fed to satiation on days fish were fed. In Experiment 1, fish fed less frequently than daily consumed significantly less feed (over the experimental period) and gained significantly less weight than fish fed daily, except that feed consumption of fish deprived of feed 1 d/wk was not significantly different from that of fish fed daily. Compared with fish fed daily, fish deprived of feed 2 d/wk had significantly lower feed conversion ratio (FCR). Visceral fat of fish deprived of feed 1 or 2 d/wk was similar to that of fish fed daily, but fish deprived of feed for longer periods had significantly lower visceral fat than fish fed daily. Regression analysis indicated that feed consumption, weight gain, and visceral fat increased linearly as the number of days that fish were fed increased. In Experiment 2, there were no significant differences in the amount of feed fed between fish deprived of feed 1 d/wk and those fed daily. Net production of fish deprived of feed 1 or 2 d/wk or 1 d per 5-d period was not significantly different from that of fish fed daily, but fish deprived of feed for longer periods had significantly lower net production than fish fed daily. Visceral fat of fish deprived of feed 1 d/wk or 1 d per 5-d period was similar to that of fish fed daily, but fish on other treatments had significantly lower visceral fat than fish fed daily. Regression analysis showed that as the number of days fed increased the amount of feed fed and net production increased quadratically. Feed conversion ratio, carcass yield, visceral fat, and fillet fat increased, while fillet moisture decreased linearly as the number of days fed increased. Although feeding less frequently than daily may improve feed efficiency, and fish deprived of feed may demonstrate compensatory growth when a full feeding regime is resumed, it may be difficult to provide enough feed to satiate all size-classes of fish under a multiple-batch cropping system without causing water quality problems. Under normal economic conditions, fish should be fed daily to apparent satiation without waste and without causing water quality problems. However, during periods of unfavorable economic conditions, channel catfish raised from advanced fingerlings to market size may be fed less frequently than daily to reduce production cost. Results from the present study indicated that feeding channel catfish to satiation 5 or 6 d/wk (not feeding on one or two weekend days) could provide some benefits in reducing production cost through reduced feed and labor costs for food-sized channel catfish during periods of low fish prices and high feed prices. [source] | |||||||||||||