Bioacciimulation of copper in the tissues of Potamonautes warreni (Calman) (Crustacea, Decapoda, Branchiura), from industrial, mine and sewage-polluted freshwater ecosystems

The copper concentration detected in the water and sediments of the Natalspruit River, Bronkhorstspruit River and Nooitgedacht Dam exceeded certain stated limits for the protection of aquatic life. Despite considerable individual variation, the general ranking of copper concentrations in the various tissues was carapace < muscle < gonads < midgut gland < gills. Seasonal variation was detected in the bioaccumulation of copper in crabs sampled from the Natalspruit River. However, this phenomenon did not occur in crabs from the other two water bodies. A significant increase in copper concentrations was detected with a decrease in size, indicating that the size of the crabs is an important influencing factor in the bioaccumulation of copper. It was also found that more copper accumulated in the ovary than in the testis per unit weight. The bioaccumulation factors (BF) calculated for the different tissues with respect to the water were highest in the gills and midgut gland (785,00 – 1257,50 and 432,00 – 1340,00, respectively). The BF with respect to the copper concentration in the sediments was comparatively low for all the tissues (<0,10 – 2,74). It appears that P. warreni is able to regulate the copper concentrations in its various tissues and is therefore not a suitable indicator of the presence of copper in the aquatic environment

Sublethal effects of manganese on the carbohydrate metabolism of Oreochromis mossambicus after acute and chronic exposure

Carbohydrate metabolism variables of Oreochromis mossambicuswere investigated after acute and chronic sublethal manganese exposure. The sublethal concentrations were determined from the LC50 value of manganese. After the exposures, the fish were carefully netted and blood was drawn from the caudal aorta. The differences in the values of carbohydrate metabolism variables of exposed fish were measured against control values and statistically analysed to prove statistically significant differences in variable values, caused by the metal pollutant (P < 0.05). The results obtained showed changes in the carbohydrate metabolism variables (glucose, lactate, glucose-6-phosphate dehydrogenase and pyruvate kinase concentrations). These alterations are produced as a result of increased levels of Cortisol and catecholamines, as well as hypoxic conditions. The latter induce hyperglycemia and increased lactate levels. Hypoxia may be a result of the damaging effect of manganese on the gills after exposure. The enzymes involved in the carbohydrate metabolism are sensitive to metal exposure and therefore enzyme concentrations fluctuated after the exposure to manganese. Enzyme function plays an important role in the catalysing of chemical reactions in an organism and the disturbance thereof could lead to death. Fish enzyme levels are therefore important biomarkers in the event of metal pollution in a water source

Bioaccumulation of chromium and nickel in the tissues of Barbus marequensis A. Smith, 1841 from the Lower Olifants River, Mpumalanga

Bioaccumulation of chromium and nickel in selected tissues and organs of the freshwater fish Barbus marequensis was investigated. According to the monthly data, the blood accumulated the highest amount of chromium, followed by the bile and vertebrae, while the skin accumulated the lowest amount. Nickel mainly accumulated in the blood, followed by the vertebrae and gills, while the lowest nickel concentrations occurred in the fat tissue. Although significant differences (p ≤ 0,05) between localities were detected, no definite trend as to where the highest bioaccumulation had occurred could be established. The levels in the tissues and organs of B. marequensis suggested no serious chromium or nickel pollution in the study area

The effect of drying the herbage on soluble nitrogen content and partial digestion.

The amount of soluble nitrogen and the effective degradation of fresh and dry herbage of Lolium multiflorum cv. Midmar was determined by the nylon bag technique. In another experiment the digestion and disappearance of organic matter and nitrogen were measured on fresh and dry ryegrass herbage fed to sheep either ad lib or at ad lib-20 per cent. The amount of soluble nitrogen was reduced by drying at 60 degrees Centigrade but the effective degradation remained unaltered; The amount of soluble N and the effective degradation of fresh and dry herbage of Lolium multiflorum cv. Midmar (ryegrass) was determined by the nylon bag technique. In another experiment the digestion and disappearance of organic matter (OM) and nitrogen (N) were measured on fresh and dry ryegrass herbage fed to sheep either ad lib or at ad lib-20%. The amount of soluble N was reduced by drying at 60°C but the effective degradation remained unaltered. The disappearance of OM an N components in the digestive tract was not significantly influenced by treatment but the effect of level of intake was significant. There was, however, no significant treatment x feeding level interaction. The soluble N content of ryegrass did not affect non-ammonia N absorption in the small intestine significantly. It was concluded that amino acid absorption from the small intestine will not be limiting at dry matter contents of Midmar ryegrass of 18-20%.Language: EnglishKeywords: Digestibility; Lolium multiflorum; Nonammonia nitrogen; Nylon bag technique; Ryegrass; Ryegrass intake; Sheep; degradation; intake; nitrogen; nylon bag; utilization; herbage; organic matter; dry matter content; drying; digestion; n; technique; digestive tract; feeding; absorption; hatfield experimental farm; pretoria; south afric

Distribution of the portunid crab Ovalipes punctatus (De Haan) in Algoa Bay and salinity and temperature tolerances of its zoeae

The three-spot swimming crab Ovalipes punctatus is commonly found in surf zones off sandy beaches in Algoa Bay. It is exclusively marine and occurs down to a depth of 38 m. Large crabs were found close inshore while smaller crabs were predominantly found in deeper water, suggesting that settlement mainly occurs offshore in water 25 – 38 m deep. Gravid females were found closer inshore in shallow water. The zoeae could not tolerate high temperatures (>27,5 °C) or low salinities (<15‰). The optimal temperatures and salinities for survival of the zoeae were 15–22 °C and 34–35‰ respectively

Tooth replacement of tigerfish <i>Hydrocynus vittatus</i> from the Kruger National Park

Evidence of tooth replacement was observed in 14 tigerfish which had been caught during the period 1991 - 1993 in the Olifants and Letaba rivers in the Kruger National Park. Replacement of teeth is a quick process (3-5 days) and first replacement of adult coni- cal dentition takes place at six to seven months post hatch, at a body length of 100 mm (FL). Swollen gums are evident prior to tooth replacement and newly erupted teeth are loosely embedded in the gums. Tooth replacement occurs in both the upper and lower jaws simultaneously. It was observed in the laboratory that the feeding behaviour was affected when adult conical dentition was replaced in @ 287 mm (FL) specimens

Utilization of Lolium multiflorum by sheep: 1: Influence of dry matter content and correlated factors on voluntary intake.

The intake by young sheep of Lolium multiflorum cv. Midmar with dry matter contents of between 10.2 per cent and 20.5 per cent was studied. Intake was measured on pasture, while at the same time herbage was cut and fed either fresh or dry indoors. Quality parameters did not change much between DM contents studied; The intake by young sheep of Lolium multiflorum cv. Midmar (ryegrass) with dry matter (DM) contents of between 10.2% and 20.5% was studied. Intake was measured on pasture, while at the same time herbage was cut and fed either fresh or dry indoors. Additional variables were sward height at pasture and chop length indoors. Quality parameters did not change much between DM contents studied. Intake of wet herbage remained fairly constant irrespective of DM content, suggesting that moisture levels exert a controlling influence on intake. Organic matter (OM) intake increased dramatically with DM content, from 47.4 to 87.4 g kg -1W 0.75day -1. Sward height did not influence OM intake significantly, but chop length of cut herbage did. At low DM content the long chop length depressed intake, possibly because of increased chewing and rumination times, while no effect was observed at higher DM contents. It was concluded that if the intake of Midmar ryegrass is to be maximized the DM content or pasture should be at least 18-20%.Language: EnglishKeywords: Chop lengths; Digestibility; DM; Dry matter; Fresh herbage; Lolium multiflorum; Pastures; Ryegrass; Sheep; Sward heights; chop length; herbage; organic matter; pasture; quality; sward height; dry matter content; rumination; hutton soil type; hatfield experimental farm; pretoria; south afric

Lethal copper concentration levels for <i>Clarias gariepinus</i> (Burchell, 1822) @ a preliminary study

Lethal copper concentrations were determined for both adult and juvenile Clarias gariepinus at representative mean summer and winter temperatures. Fish were exposed to copper for 96 hours in an experimental system and mortalities monitored. Toxicity curves of percentage mortality versus actual copper concentration were drawn, and the LC50 calculated for winter and summer temperatures. The lethal copper concentrations, expressed as LC50, found in laboratory exposures, ranged for adults from 1,29 mg/1 during summer to 1,38 mg/1 in winter. These values are considerably higher than the levels of copper in the water of the Olifants River in the Kruger National Park during summer (0,055 @ 0,016 mg/1) and winter (0,085 @ 0,032 mg/1). The derived LC50 values predict the level of copper which should be prevented at all cost. The fish in the Olifants River are already exposed to sublethal concentrations (40 of LC50) of copper. The results can be used as an indication of what the safe concentrations of copper should be

Suspended silt concentrations in the lower Olifants River (Mpumalanga) and the impact of silt releases from the Phalaborwa Barrage on water quality and fish survival

Silt loads in the Olifants and Sabie river systems inside the Kruger National Park, were monitored by collecting water samples every consecutive week for a period of 20 months. The variation in silt concentration, changes in selected physico-chemical water quality variables and fish mortalities during flushing (i.e. release of silt, by sluicing) of the Phalaborwa Barrage, were also monitored. The Olifants River inside the Kruger National Park carried high silt loads in summer; in the dry season the suspensoid load was greatly reduced. A similar pattern was observed in the Sabie River, but the silt loads were generally lower. It was apparent that silt loads released from the Phalaborwa Barrage led to large variations in the natural silt loads of the Olifants River. These increased amounts of silt (25 000 mg/1 to >70 000 mg/1) caused drastic reductions in the dissolved oxygen concentration of the water, ranging from >6 mg/1 to 0 mg/1. Depending on the severity and duration of the flushing, fish succumb to such silt loads. These findings, as well as published information, indicate that the management strategy of flushing to improve storage capacity is ecological unacceptable. It is therefore suggested that the use of the Phalaborwa Barrage as a future reservoir should be critically re-evaluated