Discriminating the pH toxicity to Poecilia reticulata Peters, 1859 in the Dunas Lake (Camaçari, BA, Brazil)

Toxic potential of the pH reduction to fingerlings of Poecilia reticulata, through acute toxicity bioassays, as well as the influence of increased pH on the toxicity were assessed. Acid lake samples (Dunas Lake) were collected during 19 months, and assessed with following treatments: water at local pH (+/-3.0) and samples with modified pH to 3.5, 3.8, 4.0, 4.3, 4.6, 5.0, 5.5, 6.0, and 6.5. Culture water samples with pH reduced to 3.0 were also assessed. Newborn P. reticulata were exposed during 96h, and dead/immobile organisms were counted at various time intervals during exposure (short intervals in the beginning and long towards the end). Mean results of LT(50) and confidence intervals from the Dunas Lake and control water with reduced pH were 1.36 (+/-0.48)h, and 1.03 (+/-0.50)h, respectively, with no statistical difference. Samples with increased pH showed a significant reduction in toxicity, with no toxicity detected at pH 6.0 and higher. Relationship between pH and lethal toxicity for fingerlings of P. reticulata demonstrated that pH exerted a strong effect on the survival of this species at the Dunas Lake, explaining about 80% of the toxicity observed.     

In situ and laboratory bioassays using Poecilia reticulata Peters, 1859 in the biomonitoring of an acidic lake at Camaçari, BA, Brazil

The suitability and viability of acute in situ bioassays were investigated in the biomonitoring program of an acidic lake contaminated with sulphur residues. Responses of organisms observed in laboratory and in situ bioassays were also assessed to determine whether or not they were similar and comparable, regarding accuracy and precision. Newborn Poecilia reticulata were employed as test organisms and exposed to the same water samples under in situ and laboratory conditions. Mortality/immobility was the endpoint assessed and dead/immobile organisms were counted at various time intervals during exposure. The mean calculated LT50 values and 95% confidence intervals were 1.61 (1.36-1.87) h in the laboratory bioassays and 0.72 (0.55-0.89) h in the in situ bioassays. Statistical comparison of these values revealed a significant difference (p<0.05). In situ bioassays were more accurate than those carried out in the laboratory, demonstrating higher sensitivity and better reproduction of what occurs in nature, while laboratory bioassays were more precise.     

Potential re-colonisation by cladocerans of an acidic tropical pond

To predict how re-colonisation of acidified lakes will proceed, at least two approaches are possible: (i) to compare the life history traits of candidate species and determine which one has the highest fitness, and (ii) to simulate a more realistic scenario carrying out experiments with the grouping of the candidate species, so that the intrinsic rate of natural increase of each species is integrated with its sensitivity to low pH and its ability to compete with the other candidate populations. The objective of the present study was to investigate the future re-colonisation of such acidified systems, taking as case-study a tropical pond (Lagoa das Dunas, Camaçari, BA, Brazil) and four species of cladocerans occurring in nearby water bodies (Ceriodaphniacornuta, Ceriodaphniasilvestrii, Latonopsisaustralis and Macrothrix elegans), by comparing the two above mentioned approaches. The second approach included two sets of in situ microcosms experiments, one simulating the re-colonisation by immigrating ephippia, thus using neonates of each species as colonisers, and another simulating the immigration of adults. Both these simulations followed nearly the same trends. The integration of the effects of a higher temperature, a different photoperiod and species competition determined differences in the species densities ranking between the two approaches: life history versus microcosms. The densities of C.cornuta in the microcosms matched the biphasic concentration/response hormetic model, in the simultaneous presence of two increasingly intense stressors (interspecific competition and acidity), with a low-dose stimulation and a high-dose inhibition. The present study provided, thus, a further support to the acceptance of hormesis in ecotoxicology, also at the population level in multispecies experiments.     

The first world conservation lecture

Summary This, The First World Conservation Lecture, was presented at the Royal Institution, London, UK, on 12 March 1981. The Lecture celebrated the 20th anniversary of the World Wildlife Fund, and the first anniversary of the World Conservation Strategy. The Lecture was organized by the World Wildlife Fund, UK.Published with the kind permission of the World Wildlife Fund, UK.Edward Max Nicholson, CB, CVO, Commandeur (Netherlands), Order of the Golden Ark, holds honorary doctorates from the University of Aberdeen, and The Royal College of Art London. He was educated at the University of Oxford, and was a member of the University's expeditions to Greenland (1928) and to British Guiana (1929). He was General Secretary (until 1940), later Chairman of PEP (Political and Economic Planning): now Vice-President of its successor body, the Policy Studies Institute. From 1945 to 1952 he was Secretary of the Office of the Lord President of the Council, then Deputy Prime Minister of the United Kingdom. He was member of the Advisory Council on Scientific Policy from 1948–1964. In 1952 he was leader of the joint UN/FAO Development Team in Baluchistan. Charter Member from 1949, and Director-General (1952–1966) of the Nature Conservancy, London, UK. From 1963 to 1974 he was Convenor of the Conservation Section of the International Council of Scientific Unions' International Biological Programme. President of the IUCN Technical Meeting in Edinburgh in 1956, concerned with rehabilitation of areas biologically devastated by human disturbance, and relation of ecology to landscape planning. Member, Panel on Landscape Action Program, The White House Conference (USA) on Natural Beauty (1965). Secretary, HRH The Duke of Edinburgh's Study Conference on The Countryside in 1970 (1963 and 1965). Council and Board Member of IIED. Godman-Salvin Medallist British Ornithologist Unions. Phillips Medallist and Member of Honour IUCN, Geoffroy St. Hilaire Gold Medal, Société Nationale de Protection de Nature de France, Premio Europeo Cortina-Ulisse (1971), Europa Preis für Landespflege (1972), Hon Member of World Wildlife Fund, Chairman Ecological Parks Trust, President RSPB, 1980. Principal Consultant and Chairman of Land Use Consultants Ltd (London) since 1966. Author of many books,Birds and Men (1951);Britain's Nature Reserves (1958),The System (1967);The Environmental Revolution (1970).