University of Fort Hare

About: University of Fort Hare is a education organization based out in Alice, South Africa. It is known for research contribution in the topics: Population & Higher education. The organization has 2386 authors who have published 4668 publications receiving 69665 citations. The organization is also known as: Fort Hare University & UFH.

Long-term decline in krill stock and increase in salps within the Southern Ocean.

Abstract: Antarctic krill (Euphausia superba) and salps (mainly Salpa thompsoni) are major grazers in the Southern Ocean, and krill support commercial fisheries. Their density distributions have been described in the period 1926-51, while recent localized studies suggest short-term changes. To examine spatial and temporal changes over larger scales, we have combined all available scientific net sampling data from 1926 to 2003. This database shows that the productive southwest Atlantic sector contains >50% of Southern Ocean krill stocks, but here their density has declined since the 1970s. Spatially, within their habitat, summer krill density correlates positively with chlorophyll concentrations. Temporally, within the southwest Atlantic, summer krill densities correlate positively with sea-ice extent the previous winter. Summer food and the extent of winter sea ice are thus key factors in the high krill densities observed in the southwest Atlantic Ocean. Krill need the summer phytoplankton blooms of this sector, where winters of extensive sea ice mean plentiful winter food from ice algae, promoting larval recruitment and replenishing the stock. Salps, by contrast, occupy the extensive lower-productivity regions of the Southern Ocean and tolerate warmer water than krill. As krill densities decreased last century, salps appear to have increased in the southern part of their range. These changes have had profound effects within the Southern Ocean food web.

Fire, resprouting and variability: a recipe for grass–tree coexistence in savanna

Abstract: Summary 1 Savanna ecosystems are characterized by the codominance of two different life forms: grasses and trees. An operational understanding of how these two different life forms coexist is essential for understanding savanna function and for predicting its response to future environmental change. 2 The existing model, which proposes that grasses and trees coexist by a separation of rooting niches, is not supported by recent empirical investigations. Our aim was to define an alternative mechanism of grass–tree coexistence in savanna ecosystems. The model we have built concentrates on life history–disturbance interactions between grasses and trees. 3 The model demonstrates coexistence for a wide range of environmental conditions, and exhibits long periods of slow decline in adult tree numbers interspersed with relatively infrequent recruitment events. Recruitment is controlled by rainfall, which limits seedling establishment, and fire, which prevents recruitment into adult size classes. Decline in adult tree numbers is the result of continuing, but low levels, of adult mortality. Both aspects of the dynamics are consistent with an established non-equilibrium mechanism of coexistence (the storage effect). 4 A sensitivity analysis indicated that data on tree resprouting ability, stem growth rates and the relationship between seedling establishment and wet season drought are essential for predicting both the range of conditions for which coexistence is possible and the response of savanna ecosystems to environmental change. 5 Our analysis suggests that understanding grass–tree interactions in savanna requires consideration of the long-term effects of life history–disturbance interactions on demography, rather than the fine-scale effects of resource competition on physiological performance.

Antibiotic Use in Agriculture and Its Consequential Resistance in Environmental Sources: Potential Public Health Implications

Abstract: Due to the increased demand of animal protein in developing countries, intensive farming is instigated, which results in antibiotic residues in animal-derived products, and eventually, antibiotic resistance. Antibiotic resistance is of great public health concern because the antibiotic-resistant bacteria associated with the animals may be pathogenic to humans, easily transmitted to humans via food chains, and widely disseminated in the environment via animal wastes. These may cause complicated, untreatable, and prolonged infections in humans, leading to higher healthcare cost and sometimes death. In the said countries, antibiotic resistance is so complex and difficult, due to irrational use of antibiotics both in the clinical and agriculture settings, low socioeconomic status, poor sanitation and hygienic status, as well as that zoonotic bacterial pathogens are not regularly cultured, and their resistance to commonly used antibiotics are scarcely investigated (poor surveillance systems). The challenges that follow are of local, national, regional, and international dimensions, as there are no geographic boundaries to impede the spread of antibiotic resistance. In addition, the information assembled in this study through a thorough review of published findings, emphasized the presence of antibiotics in animal-derived products and the phenomenon of multidrug resistance in environmental samples. This therefore calls for strengthening of regulations that direct antibiotic manufacture, distribution, dispensing, and prescription, hence fostering antibiotic stewardship. Joint collaboration across the world with international bodies is needed to assist the developing countries to implement good surveillance of antibiotic use and antibiotic resistance.