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  • 1985-1989  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Long-term trends in algal-dominated rocky subtidal communities on the Swedish west coast — a transitional system? (1986)
    Springer
    Hydrobiologia 142 (1986), S. 81-95 
    Details
    ISSN: 1573-5117
    Keywords: rocky subtidal communities ; algae ; eutrophication ; long-term change ; predation ; Skagerrak
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Rocky subtidal communities on the Swedish west coast were monitored over approximately 16 years (1970–1985) by means of stereophotographic recordings, at intervals, of fixed sites. Dominating elements of community structure were studied at the 5- and 10 m depth levels of an outer archipelago locality. Excluding seasonal variations, the basic community structure, largely dominated by the perennial phaeophycean Halidrys siliquosa (L.), remained relatively stable over the first 7–8 years of study, but with an increasing trend in cover of filamentous epiphytic red algae. Later, the structure of the studied communities changed radically. The changes initially involved intense settling of the blue mussel Mytilus edulis L. and reduced cover of red algae. The mussels settled largely on Halidrys plants which eventually broke down almost completely. Later, there was intensive predation on Mytilus by the starfish Asterias rubens Linné. After the elimination of Mytilus, the studied test areas were dominated by filamentous ephemeral red algae for the rest of the study period, but with some regeneration of Halidrys at the 5 m level. The observed changes were thought to be indicative of a major disturbance in the coastal ecosystems off the Swedish west coast during the studied period. This notion is discussed in relation to studies of other components of the ecosystem during the same time period and in relation to possible causes. Among the latter may be mentioned a suspected eutrophication process, long-term temperature anomalies and resulting effects on biological interrelationships such as competition, predation and chemical defense. The observed trends included a shift in dominance from slow-growing perennial algae to fast-growing ephemeral algae. If this shift was a general phenomenon, for which there is some circumstantial evidence, it could have important repercussions on the cycling of nutrients and organic matter in the coastal ecosystem. Possible effects are discussed on hypothetical terms in relation to observed anomalies in phytoplankton blooms and benthic oxygenation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00026749
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Comparative trends and ecological patterns of rocky subtidal communities in the Swedish and Norwegian Skagerrak area (1986)
    Springer
    Hydrobiologia 142 (1986), S. 71-80 
    Details
    ISSN: 1573-5117
    Keywords: rocky subtidal community ; long-term ; fluctuations ; recruitment ; predation ; common trends
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Inside the COST 647 Rocky Subtidal Programme, as well as before this came into operation, a cooperation has been developed between Swedish and Norwegian groups working with rocky subtidal ecology in the Skagerrak area. Along a coastline of more than 300 km, and additional large fjord systems, natural fixed-site rocky subtidal communities have been stereophotographically recorded more or less seasonally over a considerable number of years (15 in Sweden and 7 in Norway). Additional experimental studies have been undertaken in situ. Inter-site comparisons revealed many examples of co-variation in long-term population fluctuations. A common 7-year cyclic pattern was clearly illustrated for the ascidian Ciona intestinalis and the echinoid Echinus esculentus. Similar long-term trends were found in populations of Asterias rubens, Ascidia mentula, Sabella penicillus, Crania anomala and Protantea simplex over the time periods available for comparison. Locally deviating populations were also found, however. Major structuring factors, as well as key species, appeared to be largely the same over the geographic range studied. By comparing all of our results (mostly based on already published data), recruitment and predation were found to be the most important locally organizing factors. Recruitment strategies and patterns influenced both community structure and long-term trends. Predation by echinoderms and gastropods modified the structure of established communities. The common key predator in the area, Asterias rubens, largely influenced community structure by selective predation on the dominant competitors Ciona intestinalis and Mytilus edulis which, in the absence of predation, appeared to be highly capable of substrate monopolization in various parts of the studied communities, depending on depth and exposure. The results indicate the existence of large-scale structuring factors, probably linked to climatic events. This is considered as an important pre-requisite for the future recognition and understanding of local deviations, e.g. as results of pollution. This study also pinpoints some species and processes that should be focussed upon in monitoring programs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00026748
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
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