The Zooplankton of Mgazana,A Mangrove Estuary in Transkei,Southern Africa

Mgazana, a mangrove estuary inTranskei, was investigated from May 1972 to March 1973 at six-week intervals. Salinities were consistently above 25 parts per thousand in the middle and lower estuary. In the upper estuary the salinity varied between 4 and 29 parts per thousand. Water temperatures varied between I5,5°C and 28°C. One hundred and fifteen taxa of zooplankton organisms were recorded in the samples. The copepods Acartia naialensis and Oithona brevicornis reached high population densities and numbers exceeding 100 000/m³ of water were recorded. Mysids were major contributors to zooplankton biomass. A maximum biomass of I 200 mg/m³ was recorded in February in the middle estuary and was attributed to the mysid Mesopodopsis africana. Species of mysids showed clear seasonal and spatial patterns of distribution in the estuary.     

Mysidacea of the Mtentu River Estuary,Transkei, South Africa

The Mtentu River has a straight open tidal estuary flowing between steep grassy or indigenous forest-covered slopes. Total high-water surface area is about 0,3 km.^a The zooplankton was studied by periodic sampling over a period of thirteen months. Some physical characteristics of the estuary are presented. The seasonal and spacial distribution and relative importance of four species of mysid, is discussed. The most common mysid in the estuary was Mesopodopsis africana, although Rhopalophthalmus terrcmatalis, in view of its larger size, contributed more to the overall mass of mysids in the samples.     

The Zooplankton of Msikaba Estuary

Stratification is well developed in Msikaba estuary and has a major influence on the distribution of the zooplankton. The oligohaline zooplankton component does not become well established, while marine zooplankton organisms penetrate relatively far up the estuary in the high salinity bottom waters. The euryhaline component becomes relatively well established near the mouth and it would appear that these organisms maintain their position within the estuary by vertical migration between inflowing bottom and outflowing surface waters. Seasonal means of zooplankton biomass were similar and ranged between 16 mg/m⁸ of water during winter and 15 mg/m⁸ during summer.     

Episodic recruitment of the rock oyster Saccostrea cuculiata (Born, 1778) on the Transkei coast

An exceptionally good recruitment of the rock oyster Saccostrea cucullata is reported from the Transkei coast. Prior to 1989 individuals smaller than 20 mm accounted for less than 3% of the population. New recruits now account for between 25% and 48% of standing stock. This single recruitment, which is 6 to 31 times the annual mean recorded over the last 6 to 7 years, represents 5 to 37 individuals m^?2. The variable nature of recruitment in this species is discussed in relation to its resistance to exploitation.     

The benthos of South Lake,St Lucia following a period of stable salinities

The invertebrate benthos of South Lake, St Lucia was monitored monthly from August 1981 to July 1982 following a period of stable salinities of approximately 35°/oo. The overall mean biomass for the year (dry mass) was 2,63 g m^-2 with mean values for muddy and sandy substrata of 4,19 g m^-2 and 1,07 g m^-2 respectively. The major contributors to standing stock were the bivalve Solen cytin-draceus and the polychaete Marphysa macintoshi. A total of 37 taxa were recorded compared with 23 in a previous survey in 1972-73. Present results are compared with those of 1972-73 and the differences discussed. The main changes were a decline in Assiminea, Nassarius and Prionospio and an increase in abundance of long-lived bivalves together with larger polychaetes. Species diversity at the sampling sites is analysed and discussed in terms of equitability of distribution.     

The Elimination of Foreign Particles Injected into the Coelom of the Holothurian — Cucumaria Stephensoni D. John

The distribution of Gelidium pristoides, a commercially important seaweed in South Africa, was investigated on St Croix Island in Algoa Bay. Total area of the midlittoral G. pristoides belt was 4241 m² and total summer standing crop of this perennial seaweed was 265 kg (dry mass). Monthly numerical composition of G. pristoides epifauna at three sites on St Croix is presented and discussed. Nematodes dominated the epifauna throughout the year with harpacticoids the second most abundant taxon. The presence of nauplius, annelid and Diptera larvae as well as juvenile amphipods and molluscs in the epifauna indicates the role of seaweeds as nursery areas for littoral fauna. G. pristoides epifauna averaged 1,77 x 10⁵ animals m^-2. Total summer standing stock of G. pristoides epifauna on St Croix was determined by two methods which yielded 6,4 x 10⁸ and 7,3 x 10⁸ animals respectively.     

The ecology of two degraded estuaries on the north coast of Natal,South Africa

The biota of the Tongati and Mdloti estuaries were studied in relation to the environment and human interference. Results are compared with those obtained from a relatively undamaged estuary. The Tongati receives treated sewage effluent, is rarely closed from the sea, has low salinities and low oxygen tensions, but is rich in phosphorus and nitrogen. Energy values of benthic floe from Tongati were high and large quantities of water hyacinth (Eichomia crassipes) occurred. The zooplankton and zoobenthos were impoverished and dominated by freshwater species. The roots of Eichomia provided a habitat for many invertebrates, chiefly insect larvae and the crab Varuna iitterata. The fish fauna was poor and most species were confined to the lagoon near the mouth. Iliophagous species, mainly Mugilidae, were dominant. The Mdloti, frequently closed from the sea but often artificially opened, exhibited typical estuarine salinity patterns, was well oxygenated but relatively poor in phosphorus and nitrogen. Primary production and energy values of benthic floe were low. Zooplankton and zoobenthos were impoverished. The fish fauna, similar to that of Tongati, was dominated by Mugilidae.

The food chain from benthic floe to iliophagous fish remains viable in these degraded estuaries.     

Retrospective comparison of three doses of metronomic chlorambucil for tolerability and efficacy in dogs with spontaneous cancer

The study hypothesis is that higher doses of metronomic (low‐dose) chlorambucil will improve outcome without significantly worsening adverse events (AE). Retrospectively, 88 dogs were screened to assess for tolerability and response to chlorambucil utilizing retrospective and prospective data sets, comparing metronomic oral daily doses 4, 6 and 8 mg m². There were 78 and 70 dogs in the tolerability and efficacy portions, respectively. The severity of gastrointestinal (GI) AE was significantly worse, and time to development of GI events was significantly shorter at 6 mg m² than at 4 mg m² (both P < 0.001). Chlorambucil was discontinued earlier in the dogs treated at the 6 mg m² doses than in the dogs treated at 4 mg m² (P = 0.015). Thrombocytopenia occurred significantly earlier at 8 mg m² than at 4 mg m² (P = 0.017). Higher doses of metronomic (low‐dose) chlorambucil did not provide improved responses and were associated with more AE.     

The population dynamics of the estuarine isopod Exosphaeroma hylocoetes (Barnard, 1940) within three temporarily open/closed southern African estuaries

The population dynamics of the estuarine isopod, Exosphaeroma hylocoetes, was investigated monthly from February 2006 to August 2007 in three temporarily open/closed Eastern Cape estuaries, the East and West Kleinemonde and Kasouga Estuaries. Mean isopod abundances and biomasses ranged between 0 and 4791 ind/m² and 0 and 9.65 mg/dwt/m² in the West Kleinemonde Estuary and between 0 and 108 ind/m² and 0 and 0.318 mg/dwt/m² in the nearby East Kleinemonde Estuary. In the Kasouga Estuary, the values ranged between 0 and 3650 ind/m² and 0 and 5.105 mg/dwt/m². Temporal changes in the abundance and biomass of E. hylocoetes within the three systems was primarily linked to mouth phase, with populations crashing when the mouth was open and to a lesser extent, seasonality. In all three estuaries maximum abundance and biomass was recorded in the middle reaches, which could be ascribed to the presence of submerged macrophytes. E. hylocoetes demonstrates strong sexual dimorphism, with males being significantly larger than females (P < 0.05). Sex ratios were skewed in favour of females in all three estuaries. Females were encountered carrying young from an overall length of 2.5 mm throughout the year     

Ecology of southern African estuaries: Part XIII. The Palmiet River estuary in the south-western Cape

The Palmiet estuary is only 1,67 km in length, but has a relatively large catchment of 539 km². Rain falls largely during winter when it scours the estuary and widens the mouth, but by late summer the mouth narrows and, in some years, may close. The estuary never closes for more than a few months, and salinities are normal. The entire estuary has clear bottom water and high bottom salinities, but the surface waters are usually fresh and darkly stained with humic acid. This permanent stratification allows many marine species to penetrate the estuary.

Owing to the scouring in winter, the sediments are coarse, >98% consisting of sand and gravel, with a low organic content. In situ primary production is low, contributing only about one fifth of the organic material in the system, the rest being imported from the river and the sea. Species richness is low, only 28 species of invertebrates being recorded, but many of these occur in enormous numbers. Callianassa kraussi plays a crucial role, trapping fine particles around its burrows and locally enhancing the organic content of the sediments. Its faeces are an important vehicle for the concentration and turnover of organic matter.

Four of the 19 species of fish recorded breed in the estuary, the rest being represented largely by juveniles or small adults. Only three species occurred in the estuary year-round, the other species being absent during the period that the estuary is in flood.

Floods and a relatively high flow of river water are critical to keeping the estuary open. If, as proposed, a dam is built on the river, steps will have to be taken to ensure that the mouth is kept open. A related problem will be the reduction of organic material entering the estuary from the river and the sea.     

Dose-escalating vinblastine for the treatment of canine mast cell tumour

The purpose of this study was to evaluate the short‐term adverse events (AEs) in dogs with mast cell tumours (MCT) receiving prednisone and dose‐escalating vinblastine (VBL). Twenty‐four dogs were treated with intravenous VBL starting at 2 mg m^?2 and then escalating in weekly increments to 2.33, 2.67 and 3 mg m^?2. AEs were graded using a standardized scoring system. No dogs receiving 2 or 2.33 mg m^?2 experienced grade 3 or 4 AEs. Among the dogs, 9.5 and 5.9% had grade 3 or 4 AEs at dosages of 2.67 and 3 mg m^?2, respectively. Serious AEs included neutropaenia (n = 3) and vomiting (n = 1), only one of which required hospitalization. These data indicate that VBL chemotherapy may be safe to administer at higher than the traditional 2 mg m^?2 dosage for dogs with MCT. Randomized prospective trials are necessary to establish whether dose escalation will translate into improved response rates when compared with the standard 2 mg m^?2 dosage.     

Abundance,Distribution and Species Composition of Fish Larvae in the Swartkops Estuary

A two-year quantitative survey of the ichthyoplankton of the Swartkops estuary has resulted in the identification of 17 larval fish. The ichthyoplankton was present through all months of the year, but was only abundant during the summer months (November-February). During both years sampled, thehighest densities were recorded in December. An attemptwas made to correlate the data with environmental parameters such as temperature, salinity and rainfall. The ichthyoplankton of the Swartkops is dominated by few species. The family Gobiidae (59,44%) and a clupeid species, Gilchristella aestuarius (31,12%), accounted for 90,56% of all the fish larvae sampled. The family Gobiidae were most common in the mouth and lower reaches of the estuary, while G. aestuarius dominated the mid- and upper estuary.     

Monitoring in a complex world — seeking slow variables,a scaled focus,and speedier learning

The nutritive value of four subtropical grasses (Panicum maximum, Anthephora pubescens, Digitaria eriantha and Chloris gayana) standing hay were compared in terms of qualitative intake and partial digestibility by sheep. The species differed significantly in terms of diet quality selected by sheep grazing the standing hay. The rumen ammonia nitrogen (NH₃-N), total volatile fatty acid and propionic acid concentrations of sheep grazing P. maximum and A. pubescens were higher than those sheep grazing D. eriantha and C. gayana standing hay. Organic matter intake (OMI) (g kg^?1 W^0.75 d^?1), nitrogen intake (g d^?1), digesta flow, the total N flow, NH₃-N flow, non-ammonia nitrogen (NAN) flow and NAN disappearance (g d^?1) in the ileum were higher for sheep grazing P. maximum than for those grazing the other standing hays. The organic matter disappearance in the stomach and small intestine of sheep grazing P. maximum and D. eriantha standing hay was higher than for those sheep grazing either A. pubescens or C. gayana standing hay. The NAN flow/N intake were the highest for sheep grazing P. maximum and A. pubescens compared to C. gayana. The NAN digestibility was, however, not significantly different among the four species. The standing hays (except for C. gayana) seemed to have the capacity to meet the N requirement of the sheep for production, but the OMI (g kg^?1 W^0.75 d^?1) was not sufficient to support maintenance requirement of the sheep.     

A survey of the fish fauna of Transkei estuaries Part Four: The Mntafufu and Mzamba River estuaries

The Mntafufu and Mzamba Rivers have small catchment areas (178 and 505 km², respectively) in the forested coastal belt of Transkei and have relatively small estuaries (5 and 2 km long, respectively). Although the annual rainfall is in excess of 1000 mm in this area, the mean annual runoff was less than 70 Mm³ in both cases. Serious floods were not observed during the survey period, while turbidity and sediment loads were usually very low. Salinities were usually high (x? = 30,0-38,0‰) in the bottom water and temperatures in the upper reaches were usually higher than in the lower reaches. The species composition, and seasonal and spatial abundance of the fish fauna of the two estuaries were determined by means of gill nets. A total of 1043 fish (385,8 kg) representing 42 species were caught in the Mntafufu estuary. The orangemouth glassnose Thryssa vitrirostris and V. cunnesius were the most abundant fish in the estuary. Numerically 42% of the catch (46% gravimetrically) belonged to the family Mugilidae (11 species) of which Mugil cephalus, Valamugil buchanani and V. cunnesius were the most important. A total of 389 fish (241,1 kg) were caught in the Mzamba estuary. Twenty-five species were obtained with Hilsa kelee dominating numerically. Seven species of mullet contributed 38,3% of the numbers or 54,2% of the fish biomass. The diamond mullet (Liza alata) and the flathead mullet (Mugil cephalus) were the most abundant in terms of biomass. The highest catches in the two estuaries were taken in the lower reaches. Mean number and biomass of fish taken per net was 20,5 fish and 7,2 kg, and 16,2 fish and 10,1 kg in the Mntafufu and Mzamba estuaries, respectively.     

Effects of different stocking densities on growth performance,antioxidant ability,and immunity of finishing broilers

The study was conducted to evaluate the effects of different stocking densities on growth performance, antioxidant capacity, and immunity of broilers. One thousand four hundred and forty 22‐day‐old Lingnan Yellow broilers were randomly allotted to five different stocking density groups (8, 10, 12, 14, and 16 birds per m²). Each group consisted of three replicates. The results showed that 8 and 10 birds/m² groups had higher average daily feed intake (ADFI) than the others (p < 0.05). Heat shock protein 70 (HSP₇₀) in the group of 16 birds/m² had the highest levels (p < 0.05). The group of 16 birds/m² had the lowest total antioxidant capability (T‐AOC) and total superoxide dismutase (T‐SOD) activities in blood serum (p < 0.05), and significantly increased interleukin‐1β (IL‐1β) and interleukin‐4 (IL‐4) concentration compared to the groups of 8 and 10 birds/m² (p < 0.05). In liver, the group of eight birds/m² had higher T‐AOC levels than that of 12, 14, and 16 birds/m² (p < 0.05) and also higher catalase (CAT) activities than that of 14 and 16 birds/m² (p < 0.05); the group of 10 birds/m² had the highest T‐SOD activities among all groups (p < 0.05). In conclusion, the above results suggest that stocking density of broilers up to 8 or 10 birds/m² can prevent the negative effects on growth performance and welfare parameters in broilers.     

Abiotic and herbaceous vegetational characteristics of an arid rangeland in Kenya

A two-year study was conducted with an overall objective of characterising the structure and function of an arid rangeland in Kenya. A plot measuring 100 × 100m was used for this study. Data on rainfall and temperature were recorded at the plot site whereas data on evaporation rates and relative humidity were obtained from the meteorological office near the study site.

Herbaceous aboveground material was sampled at monthly intervals using a rectangular 0.25m² quadrat frame. Clipped material was separated by species and classified dead or live by physical examination. A 5cm diameter metal soil corer was used to sample belowground plant material, at monthly intervals. The sampled material was washed with running water over 2mm sieves and classified dead or live using the vital staining technique. All weights and calculations were based on organic weight.

Total aboveground standing crop ranged from 84.6g m^?2 to 295.4g m^?2, with a mean of 162.3 ± 60.6g m^?2. Mean monthly aboveground standing crop for 1992 and 1993 was 142.8 ± 53.8 and 178.5 ± 63.3g m^?2 respectively. The two values were significantly different (p<0.10). Aboveground biomass yield ranged from 17.7g m^?2 to 242.7g m^?2, with a mean of 104.3 ± 58g m^?2 and a coefficient of variation of 58%. Mean aboveground standing crop was 59 ± 24g m^?2 Monthly values ranged from 28.8g m^?2 to 120g m^?2, with a 38% coefficient of variation.

The range for total belowground standing crop was from 83.3g m^?2 to 232.7g m^?2, and a mean of 155.2 ± 46g m^?2. The values had a coefficient of variation of 30%. Mean total monthly belowground plant material yield for 1992 and 1993 was 137.6 ± 41g m^?2 and 169.9 ± 46g m^?2 The coefficients of variation were 59% and 28% respectively. The mean monthly belowground biomass yield was 51.6 ± 33g m^?2 with a coefficient of variation of 64%. Mean monthly yield for belowground dead material was 103.7 ± 32g m^?2, with a coefficient of variation of 31%. There was no significant difference (p>0.01) in the mean belowground dead material yield between 1992 and 1993.

In 1992, annual NPP was 439.2g m^?2, giving a net primary productivity of 1.22g m^?2day^?l. Monthly NPP ranged from 17.2g m^?2 to 90.1g m^?2 In 1993, annual NPP was 944.5g m^?2, equivalent to a net primary productivity of 2.62g m^?2 day^?1. Monthly NPP was between 27.4g m^?2 and 548.6g m^?2. Over the 1992–1993 period, NPP was 1 383.7g m^?2, equivalent to a productivity of 1.92g m^?2day^?1. Trends in monthly NPP closely followed the trend in rainfall. On the whole, herbaceous vegetation production and productivity were episodic in nature and closely linked to rainfall. The high primary productivity puts arid and semi-arid rangelands under sharp focus as CO₂ sinks, whose role in the amelioration of greenhouse effect could be more important than is currently appreciated.     

Characteristics of Gas Generation (NH3, CH4, N2O, CO2, H2O) From Horse Manure Added to Different Bedding Materials Used in Deep Litter Bedding Systems

The aim of this study was to analyze the influence of horse manure added to different bedding materials on the generation of gases (ammonia (NH₃), nitrous oxide, carbon dioxide, methane, water vapor) from deep litter bedding under standardized laboratory conditions. Two different types of straw (wheat and rye) and wood shavings were analyzed. The deep litter (substrate) was made of 25 kg of the respective bedding material, 60 kg horse feces, and 60 L ammonium chloride solution (urea), and spread out in identical chambers over 19 days (n = 3). On days 1, 8, 15, and 19, total nitrogen, total carbon, and dry matter content of the substrate, as well as the pH in 500-g samples, were measured along with. At the end of each test period, the nitrite nitrogen, nitrate nitrogen, and ammonium nitrogen contents of the leachate were analyzed. The wheat straw substrate emitted the highest concentration of NH₃ (4.31 mg/m³; P < .0001) and the wood shavings substrate emitted the lowest (1.73 mg/m³; P < .0001); the rye straw substrate generated 3.05 mg/m³. In addition, significant differences occurred during days 1 to 3 with respect to the generation of the gases NH₃, methane, nitrous oxide, carbon dioxide, and water vapor, and after the opening of the chamber on day 15. The nitrogen losses through the leachate occurred mainly in the form of nitrate, where the leachate from the wheat straw substrate had a significantly higher amount of nitrate nitrogen (44.56 mg) as compared with the leachates of the rye straw (14.49 mg; P ≤ .0001) and the wood shaving substrates (22.62 mg; P = .0010).     

Lincomycin and spectinomycin in the treatment of breeding rams with semen contaminated with ureaplasmas

Ureaplasma species were isolated from semen samples collected sequentially from one Awassi and three Assaf breeding rams. Each ram was injected subcutaneously with an aqueous solution of lincomycin and spectinomycin for five consecutive days at a dose equivalent to 4·5 mg kg⁻¹ lincomycin and 9·0 mg kg⁻¹ spectinomycin daily. Serum and semen samples were collected at intervals during the treatment and assayed for lincomycin. No Ureaplasma species were isolated from semen samples collected during the course of the treatment and at intervals for 17 days after the last treatment. The concentration of lincomycin in semen ranged from 0·51 μg ml⁻¹ four hours after treatment to 0·08 μg ml⁻¹ 24 hours after treatment, and these levels were three to nine times higher than the corresponding serum concentrations.     

The Birds of the Alien Acacia Thickets of the South Western Cape

The plough shell, Bullia rhodostoma (Mollusca: Gastropoda), has been studied on an open sandy beach where it is a common scavenger. Samples taken over a year indicate hatching of young individuals from December to February. They reach a length of about 10 mm after 1 year and 40 mm after 10 years. The von Bertalanffy growth equation is L_t = 47 (1 - e^{-0,19(t+0,23)}) and the annual mortality rate is 0,79. Mean decalcified dry biomass is 209 mg m^-2 and production by growth 189 mg m^-2 y^-1 giving a P/B of 0,9. Most production by adults (>15 mm shell length) goes into reproduction, particularly In the females which grow larger than the males. Production by reproduction is estimated to be about 135 mg m^-2 y^-1. Average calorific values are 19,04 kJ g^-1 dry tissue     

The distribution of clostridia in poultry processing plants

An investigation was made of the contamination of poultry carcasses with clostridia during processing. In both chickens and turkeys clostridia were present initially on the feet and breast feathers (geometric mean counts of 10²‐10³/g) and were frequently isolated from the vent area immediately after evisceration. Mean counts from the breast surface just before packaging were < I‐3/10 cm² and there were 31–467/g in samples of neck skin at the same stage. Counts were progressively lower in water samples taken from scald‐tanks, wash‐tanks, spin‐chillers and chill‐tanks.

A large proportion of the isolates obtained from both chicken and turkey plants were haemolytic Clostridium welchii, but a significant number of strains from the turkey plants could not be identified with recognised species.