A review of the importance of freshwater inflow to the future conservation of Lake St Lucia

• 1. Lake St Lucia, the oldest formally protected estuary in the world is under threat from historic and present manipulation of freshwater supplies to the system.
• 2. Constraints to the functioning of the ecosystem began in 1914 with the commencement of draining and canalization of the Mfolozi Swamp to open up the swamp and river floodplain for sugar cane cultivation. Warner's Drain was completed in 1936 and the sediment filtering capability of the swamp on river floodwaters was effectively removed. This resulted in exceptionally high sediment loads from the Mfolozi River entering directly into the St Lucia system and the river was therefore diverted southwards and provided with a separate estuary mouth. This deprived St Lucia of its single largest freshwater supply.
• 3. During the past 50–60 years, increasing freshwater abstractions from the Mkhuze, Mzinene, Hluhluwe and Nyalazi rivers have contributed to the increasingly severe salinity extremes experienced by Lake St Lucia. In the past decade, desiccation of large areas of False Bay, North and South Lake has occurred, due primarily to natural estuary mouth closure combined with a prolonged drought and unnaturally low freshwater inflows during the closed phase. These events have pushed the system into an extreme state that has not been recorded previously and would not have occurred if Mfolozi River water had been available to the St Lucia system over this drought period.
• 4. Forestry plantations have further exacerbated the freshwater supply situation, although recent removal of pine plantations on the eastern and western shores of the lake are likely to help restore groundwater flows to the system.
• 5. This review explores the possibility of relinking the Mfolozi River, once the Mfolozi floodplain swamp has been re‐established, to the St Lucia system, thereby bringing urgently needed fresh water to this threatened World Heritage Site. Copyright © 2009 John Wiley & Sons, Ltd.

     

An index for the management of South African estuaries for juvenile fish recruitment from the marine environment

The release of fresh water from major impoundments to meet the requirements of estuaries has become a recognized need and methodologies to define appropriate release strategies have become an urgent priority in some parts of the world. A recruitment index for juvenile marine fish is presented, based on information relating to the preferred recruitment periods for 27 species, as well as the extent of dependency of these species on estuaries. The status of the estuary mouth (i.e. open or closed) and the longitudinal salinity differences (i.e. the difference between the salinity at the estuary head and the mouth) in the estuary are obtained from a hydrodynamic model of the estuary. The recruitment index integrates this information to provide an indication of potential recruitment (or recruitment opportunity). This index was applied in a case study of the Great Brak Estuary, South Africa, and a distinct decrease in the recruitment index was associated with a reduction in freshwater inflow. In the estuary modelled, annual run-off could be halved without an appreciable decrease in the fish recruitment index (FRI), but with a potentially sharp decline in fish recruitment thereafter. While the index represented recruitment opportunity rather than actual recruitment, it does at least provide an indication of where ecological risk is likely to increase substantially. Since the index integrates the current understanding with respect to the key processes which regulate recruitment of juvenile marine fish into estuaries, it is suggested that it has the potential to fulfil a vital role in identifying appropriate freshwater release policies for impoundments in South Africa.     

Effects of irrigation, nitrogen and gypsum on yield, nitrogen accumulation and water use by wheat

Responses of wheat grown on a heavy clay soil in the Goulburn-Murray Irrigation Region of south-eastern Australia to a factorial combination of three irrigation treatments and nitrogen and gypsum application were investigated.Irrigation treatments included a rainfed control (treatment R_F) and irrigation on either a weekly (treatment I_w) or fortnightly (treatmnt I_F) basis beginning in spring and maintained until physiological maturity. Nitrogen was applied at 0 and 150 kg N ha⁻¹ (treatments N₀ and N₁₅₀, respectively) and gypsum at 0 and 5 t ha⁻¹. Nitrogen and gypsum treatments were applied at sowing.

Yield increased from a mean of 4 t ha⁻¹ treatment R_F to 6.6 t ha⁻¹ in treatments I_F and I_W, largely because of promotive effects of irrigation on kernel weight (increase from 31 mg to 42 mg kernel⁻¹ and kernel spikelet⁻¹ (1.4 as compared with 1.7). Seasonal conditions and the relative fertility of the site were sufficient to maximise spike number and spikelet spike⁻¹. Nitrogen increased kernel spikelet⁻¹ but effects on yield were not significant because of a decrease in kernel weight. Effects of gypsum on yield were not significant.

Water-use efficiency of both rainfed and irrigated treatments was ca. 1.25 g grain kg⁻¹ H₂O. However, transpirational water-use efficiency, calculated after allowing 110 mm water for soil evaporation, fell from 2 g kg⁻¹ in treatment R_F to 1.7 and 1.5 g kg⁻¹ in treatments I_F and I_W, respectively. The decrease was ascribed, in part, to lodging and soil evaporative losses may have been in excess of 110 mm with more frequent irrigation. Effects of N on water use could not be distinguished, again because of the initial fertility of the site, which supported rapid growth and resulted in complete canopy closure.

Nitrogen and irrigation treatments had independent effects on the concentration of N in the grain (%N_G) which increased by a mean of 0.6% with N treatment despite a decrease in N harvest index (HI_N) from 0.77 to .70. Irrigation decreased %N_G by approximately 0.5%. Approximately 90 kg pN ha⁻¹ was found in the grain of treatments R_FN₀, I_WN₀, I_wN₀ and R_FN₁₅₀ and differences in %N_G in these treatments attributed to a ‘dilution’ effect mediated by the increase in yield effected by irrigation. The grain accounted for approximately 115 kg N ha⁻¹ in treatments I_FN₁₅₀ and I_WN₁₅₀, countering the inverse relationship between %N_g and yield despite the increase in HI_N index caused by N application.     

Quantitative histologic evaluation reveals different degree of liver atrophy in cachectic and starved dogs

Cases of neglect in dogs are among the forensic cases submitted most commonly for postmortem examination. Starvation is a form of primary protein-energy malnutrition in which the availability of food is severely restricted or absent; cachexia is a form of protein-energy malnutrition secondary to progressive metabolic derangement during chronic diseases. Despite both conditions leading to an emaciated appearance of the cadaver, discrimination between the two is crucial in forensic cases. We hypothesized that among emaciated dogs, the degree of liver atrophy in starved animals is higher than in cachectic ones, and that this can be investigated microscopically, regardless of the degree of cadaver decomposition. We studied 46 animals: 23 starved, 11 cachectic, and 12 control dogs. Portal tracts were identified by the presence of a bile duct and associated vascular structures recognizable by a thin rim of collagen still visible regardless of the degree of cadaver decomposition. The number of portal tracts per lpf (10×) was used as an indirect measure of atrophy. The number of portal tracts in starved dogs was significantly higher (p < 0.01) compared to both cachectic and control dogs, indicating a higher degree of liver atrophy in starvation. Measuring the density of portal tracts offers a reliable additional tool for discrimination between starvation and cachexia.     

Relationship between endometritis and oxidative stress in the follicular fluid and luteal function in the buffalo

In this study, alteration in the follicular fluid composition and luteal function was investigated in the buffalo with endometritis. Genitalia were classified into cytological and purulent endometritis on the basis of polymorphonuclear cell cut off while non‐endometritis served as control (n = 10/group). In the follicular phase, the number of surface follicles was counted, diameter of the largest follicle was measured and the follicular fluid was assayed for total protein, cholesterol, malondialdehyde (MDA), total antioxidant capacity (TAC), oestradiol (E₂) and progesterone (P₄). The P₄ content of corpus luteum during mid‐luteal phase was estimated by radioimmunoassay. Ovaries from the follicular phase of oestrous cycle showed no significant difference in the total number of surface follicles, size of the largest follicle and volume of follicular fluid in the buffaloes with and without endometritis (p > .05). However, the antral fluid of the largest follicle from the genitalia of buffalo with cytological and purulent endometritis showed a significant decrease in the concentration of total protein, cholesterol, TAC and E₂ and a significant increase in the concentration of MDA and P₄ (p < .05). The results indicated that there is an association between endometritis and decreased ovarian function.     

Outbreak of Salmonella Typhimurium associated with feeder rodents

In December 2012, an increase in human Salmonella Typhimurium cases was identified in the province of Ontario, Canada launching an outbreak investigation. The outbreak spanned 3 years (2012–2014), with 134 cases reported from five Canadian provinces. There was a substantial burden of illness among children: 45% of cases were children 12 years old or under, and 23% of cases were under 5 years old. Epidemiologic, traceback and laboratory findings linked this outbreak to feeder rodents (used to feed snakes) supplied by a network of rodent breeders in Ontario. Cases likely acquired their illness through either direct or indirect contact with feeder rodents. This investigation not only contributes to the weight of evidence on the risk that feeder rodents pose, but also underscores the importance of investigating indirect animal contact and associated risks, especially for high‐risk individuals.     

Distribution of Fishes in the Mhlanga Estuary in Relation to Food Resources

Food resources play an important role in determining the distribution offish species in the Mhlanga estuary. Standing crops of detritus and associated micro-organisms, zoobenthos, zooplankton, epiphytic flora and fauna were measured in the upper, middle and lower reaches of the estuary, and the distribution of 20 fish species related to these resources. The distribution of the majority of species correlated with the abundance of preferred food items, except for the Mugilidae where substrate particle sizes influenced the composition offish in an area.     

Expression of Survivin,Bcl‐2 and Bax Proteins in the Domestic Cat (Felis catus) Endometrium During the Oestrus Cycle

Apoptosis has been shown to be an important regulator of endometrium function. To clarify the regulation of apoptosis in the cat endometrium during the normal oestrus cycle, the expressions of the apoptosis‐related proteins (Bcl‐2 and Bax) and their correlation to the inhibitor of apoptosis protein Survivin were analysed using immunohistochemistry. The TUNEL technique (TdT‐mediated dUTP nick end labelling) was also used to detect DNA fragmentation characteristic of apoptotic cells. The results demonstrated that TUNEL labelling is not effective for the detection of apoptosis in cat endometrium. Survivin was expressed in the luminal and glandular epithelial cells of cat endometrium during all phases of the oestrus cycle. Survivin was localized in both the cytoplasm and nuclei of superficial and deep uterine gland cells during the luteal phase, while only cytoplasmic staining was observed during the follicular and anoestrus phases. Bax immunoreactivity in the cytoplasm of luminal and glandular epithelial cells as well as the smooth muscle cells of blood vessels was weak in the anoestrus phase. Compared with anoestrus, the intensity of Bax immunostaining was moderate in the follicular phase and increased dramatically in the luteal phase. Bcl‐2 immunostaining in the cytoplasm of luminal and glandular epithelial cells was moderate in the anoestrus phase. During the early follicular phase, cytoplasmic Bcl‐2 immunostaining was detected mostly in glandular epithelial cells. In the mid‐follicular phase, in glands, the amount of Bcl‐2 protein increased progressively from the superficial to the deep layer. In contrast, the expression of Bcl‐2 decreased in the secretory phase, being very low or absent in the mid‐ and late luteal phases. The overall results suggest that Survivin, Bax and Bcl‐2 proteins may cooperatively contribute to cell apoptosis and cell proliferation in the cat uterus during the oestrus cycle.     

Vitamin D receptor as an intestinal bile acid sensor

The vitamin D receptor (VDR) mediates the effects of the calcemic hormone 1alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3]. We show that VDR also functions as a receptor for the secondary bile acid lithocholic acid (LCA), which is hepatotoxic and a potential enteric carcinogen. VDR is an order of magnitude more sensitive to LCA and its metabolites than are other nuclear receptors. Activation of VDR by LCA or vitamin D induced expression in vivo of CYP3A, a cytochrome P450 enzyme that detoxifies LCA in the liver and intestine. These studies offer a mechanism that may explain the proposed protective effects of vitamin D and its receptor against colon cancer.