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  • 1
    Electronic Resource
    Electronic Resource
    Community development following removal of urchins, Strongylocentrotus droebachiensis, from the rocky subtidal zone of the St. Lawrence Estuary, Eastern Canada (1983)
    Springer
    Oecologia 59 (1983), S. 27-39 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The role of sea urchins, Strongylocentrotus droebachiensis, in structuring the rocky subtidal community was examined at Anse aux Basques on the north shore of the St. Lawrence Estuary, Québec. In an experimental area, measuring 20x20 m and extending from 0 to 10 m in depth, we greatly reduced the intensity of urchin grazing by eliminating all urchins larger than 10 mm in test diameter. This area was observed for two years and compared to an adjacent control area. In the upper portion of the experimental area during the first month after urchin removal, mid-July to mid-August 1978, a dense diatom cover developed, and during the second month the diatoms were overgrown by Ulvaria obscura. After four months (November) an Alaria esculenta overstory was present from near low water level to 3 m deep. Community development was much slower at greater depths and it took a year for the Alaria zone to extend to 4–5 m deep, and two years to extend to 6 m deep. The low light penetration at this estuarine location was probably the main factor for the slow algal development at 6–10 m deep. At the end of the experiment Agarum cribrosum was second in importance after Alaria and was most common at 3 to 6 m in depth. Laminaria spp. was found in low numbers in the first year and did not show an increase during the second year. There was a dramatic increase in the number of species and abundance of algae in the experimental area. Also, there was a marked increase in many animal species, particularly Acmaea testudinalis, Mytilus edulis and Margarites helicinus, and a decrease in Metridium senile. By contrast, in the control area, the number of algal and invertebrate species remained low. In the experimental area a sharp increase in the growth rate of a cohort of very small urchins, which was not eliminated by our removal effort, demonstrated that there is strong intraspecific competition amongst urchins when the food supply is limited. In the St. Lawrence Estuary, there are few predators of urchins and the urchin dominated community appears to be a stable situation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00388068
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    A commentary on current approaches in the aquatic sciences (1995)
    Springer
    Hydrobiologia 300-301 (1995), S. 1-16 
    Details
    ISSN: 1573-5117
    Keywords: Experiments ; spatial patterns ; limnology ; oceanography ; philosophy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Résumé L'auteur passe en revue quelques-unes des pratiques habituelles en limnologie et en océanographie et discute des possibilités d'amélioration dans ces domaines. L'examen de 253 articles parus dans le périodique Limnology and Oceanography en 1980, 1985 et 1990 montre que la majorité de ceux-ci (〉60%) est à dominante descriptive, et que l'approche expérimentale n'est utilisée que dans 30% des cas. Parmi les 27% d'articles présentant des modèles, seuls 3% valident ces modèles en utilisant des données de terrain. Un seul parmi les 253 articles présente des critères biologiques de rejet des hypothèses. La discussion porte sur l'importance des études descriptives en limnologie et en océanographie, l'emploi des techniques numériques pour détecter des phénomènes spatio-temporels dans les données, la signification du réductionnisme dans les sciences aquatiques, l'introduction d'hypothèses ad hoc, les critères de choix des sites d'études, des stations et des échantillonnages dans les études littorales et pélagiques, et les stratégies valables lorsqu'une approche expérimentale ne peut être employée en raison de facteurs environnementaux non contrôlables.
    Notes: Abstract This paper reviews some of the current practices in limnology and oceanography and discusses ways to improve our habits in these fields. A survey of all 253 articles published in the journal Limnology and Oceanography in 1980, 1985, and 1990 indicates that the majority of papers (〉60%) were predominantly descriptive, only about 30% used an experimental approach. Of the 27% articles presenting models, only 3% validated these models using field data. Only one out of 253 papers presented biological criteria to reject hypotheses. We discuss the significance of descriptive studies in the fields of limnology and oceanography, the use of numerical techniques to detect spatio-temporal patterns in the data, the significance of reductionism in aquatic sciences, the introduction of ad hoc hypotheses, the problem of selecting study sites, stations, and sample locations in shore and pelagic studies, and strategies available when an experimental approach cannot be used because environmental factors cannot be controlled.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00024444
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    Paper (German National Licenses)
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