Seasonal variation of mercury concentrations in organisms of the Cilician Basin

Total mercury concentrations in organisms typical of those found in the Cilician Basin of the northeastern Mediterranean have been measured from 1977 to the present. These concentrations show seasonal variations. Shrimp shows an approximately constant concentration of mercury which might testify to the regulation capacity of shrimp for mercury. Crab, and particular fish, show a seasonal variation which may be correlated with the local application of mercury fungicide, rainfall, and the physiology of the organisms. The rapidity with which mercury applied to the land causes increased concentrations in fish is noteworthy.     

Helpers in colonial cooperatively breeding sociable weavers <Emphasis Type="Italic">Philetairus socius</Emphasis> contribute to buffer the effects of adverse breeding conditions

Some studies on the effects of helpers in cooperatively breeding vertebrates show a positive effect of helper presence on reproductive output whereas others find no effect. One possibility for this discrepancy is that helpers may have a positive effect when breeding conditions are adverse, while their effect might go unnoticed under good conditions. We investigate this hypothesis on sociable weavers Philetairus socius, a colonial cooperatively breeding passerine that inhabits a semi-arid region where breeding conditions vary markedly. We used multivariate mixed models to analyse the effect of helpers on reproduction under contrasting environmental and social conditions while controlling for parental and colony identity. We found that reproductive success in sociable weavers was primarily influenced by nest predation and rainfall. In addition, colony size was negatively associated with hatching and fledging success and number of young fledged per season. Helpers had a less prominent but significant influence on feeding rates and reproductive outcome. In agreement with expectations, the presence of helpers counteracted some of the negative effects of breeding in periods of low rainfall or in large colonies and was also associated with an increased number of young fledged per season. Our results illustrate that the effect of helpers might be detectable mostly under unfavourable conditions, but can contribute to improve reproductive performance in those situations.     

A Protocol for Plant Conservation by Translocation in Threatened Lowland Fynbos

Abstract: A form of lowland, sandplain Fynbos restricted to the Cape Flats near the city of Cape Town is the South African vegetation type most threatened by urban and agricultural development. Cape Flats Fynbos remnants, totaling 4.8 km², contain 14 plant species endemic to the Cape Flats scattered through four protected areas and 11 unprotected vegetation fragments on public land. Despite their small size and management problems, the remaining protected areas are under pressure from the public and developers to function as "lifeboats," or places of safety, for attractive indigenous plant species from the unprotected areas destined for development because the popular perception is that any indigenous plant population threatened by habitat destruction should be saved by being transplanted into a protected area. The urgency for dealing with the issue of plant rescue in the Cape Town metropolitan area was the catalyst for a workshop held at the University of Cape Town in 1998 to develop protocols for Fynbos plant species translocations. We report on points raised by managers and academics at the workshop, including the selection of target taxa, individuals, and establishment sites, and methods for introduction, and present case histories illustrating possible solutions to the problems encountered.     

The return of the giants: ecological effects of an increasing elephant population

Northern Botswana and adjacent areas, have the world's largest population of African elephant (Loxodonta africana). However, a 100 years ago elephants were rare following excessive hunting. Simultaneously, ungulate populations were severely reduced by decease. The ecological effects of the reduction in large herbivores must have been substantial, but are little known. Today, however, ecosystem changes following the increase in elephant numbers cause considerable concern in Botswana. This was the background for the "BONIC" project, investigating the interactions between the increasing elephant population and other ecosystem components and processes. Results confirm that the ecosystem is changing following the increase in elephant and ungulate populations, and, presumably, developing towards a situation resembling that before the reduction of large herbivores. We see no ecological reasons to artificially change elephant numbers. There are, however, economic and social reasons to control elephants, and their range in northern Botswana may have to be artificially restricted.     

Foraminiferal proxies for pollution monitoring in moderately polluted harbors

Benthic foraminifera are increasingly used as environmental bio-indicators, especially in polluted environments where their sensitivity to pollutants may be expressed by a modification of the assemblages. Eighteen sediment samples were collected in September 2000 in five harbors located in moderately polluted estuaries on the coast of Vendée (France) for the study of foraminiferal assemblages. Ten heavy metals and 13 PAH have been analyzed from the sediments. The marine to continental estuarine gradient has a prevalent influence on the foraminiferal distribution. However, the results show that foraminiferal density and species richness of the assemblages decrease with an increase in heavy metal and PAH concentration, and therefore may be used as pollution indicators. Moreover, the more polluted areas are dominated by the tolerant pioneer species Haynesina germanica that may be used as bio-indicator of pollution, mainly in the uppermost areas.     

The effect of helpers on artificially increased brood size in sociable weavers (Philetairus socius)

In cooperatively breeding birds, the presence of helpers is expected to increase the reproductive success of the breeding pair. However, some studies fail to find this effect. A positive effect of helpers may be restricted to cases in which a breeding pair has a poor likelihood of raising the entire brood on its own, as would be the case under stressful environmental conditions or with enlarged brood sizes. We conducted brood size manipulations in a cooperative breeder, the sociable weaver, Philetairus socius, to investigate the relationship between the difficulty of raising nestlings and the effort and impact of helpers. Overall, sociable weavers did not work harder to raise the enlarged broods. However, the presence of helpers significantly increased the feeding rates at enlarged nests, but not controls. This was insufficient to prevent generalised brood reduction in enlarged broods, whether attended by pairs alone or with helpers. Nonetheless, the presence of helpers was associated with decreased nestling mortality and an increase in the numbers of young fledged. Our results suggest that groups are better able to respond to the needs of enlarged broods than pairs alone and that the presence of helpers has a beneficial effect on overall reproductive success.Communicated by J. Dickinson     

The mutagenic effect of tobacco smoke on male fertility

Despite the association between tobacco use and the harmful effects on general health as well as male fertility parameters, smoking remains globally prevalent. The main content of tobacco smoke is nicotine and its metabolite cotinine. These compounds can pass the blood-testis barrier, which subsequently causes harm of diverse degree to the germ cells. Although controversial, smoking has been shown to cause not only a decrease in sperm motility, sperm concentration, and an increase in abnormal sperm morphology, but also genetic and epigenetic aberrations in spermatozoa. Both animal and human studies have highlighted the occurrence of sperm DNA-strand breaks (fragmentation), genome instability, genetic mutations, and the presence of aneuploids in the germline of animals and men exposed to tobacco smoke. The question to be asked at this point is, if smoking has the potential to cause all these genetic aberrations, what is the extent of damage? Hence, this review aimed to provide evidence that smoking has a mutagenic effect on sperm and how this subsequently affects male fertility. Additionally, the role of tobacco smoke as an aneugen will be explored. We furthermore aim to incorporate the epidemiological aspects of the aforementioned and provide a holistic approach to the topic.

     

A review of plastic pollution in aquatic ecosystems of Turkey

Environmental Science and Pollution Research - Turkey is one of the major plastic pollution sources in the Mediterranean and the Black Sea. This review summarizes present information, data, and...