摘要:

AbstractThe restoration of a 1.3 km straightened and channelized reach of the River Gelså to a new 1.9 km meandering course is one of the largest river restoration projects so far undertaken in Denmark. In order to elucidate the ecological impact of restoration, the macroinvertebrate community present in the reach prior to and following its restoration was compared with that in an upstream reach that remained straight and channelized.Two years after restoration of a meandering course, macroinvertebrate density and diversity was greater than in the upstream control reach,Gammarus pulexL. being particularly abundant in the restored reach. In general, species preferring a stony habitat seemed to favour the new reach;Heptagenia sulphureaMüll. was only found on stones in the restored reach, and was totally absent from the control reach. Two other stone‐preferring species,Ancylus fluviatilisMüller andHydropsyche pellucidulaCurtis, were found in higher density in the control reach; however, this probably reflects competition for the limited space available on stones.The study shows that river restoration can have a positive impact on macroinvertebrate community structure, and probably higher trophic levels also, such as fish, due to increased numbers of potential prey organisms. In addition, the study suggests that the impact of restoration projects on the macroinvertebrate community is best understood by undertaking both qualitative and quantitative stu

ISSN:1052-7613    

DOI:10.1002/aqc.3270040402

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe effects of catchment liming, used to restore acidified streams, are still only partially known. In particular, the impact on aquatic bryophytes remains unappraised.Six upland streams were surveyed for aquatic bryophytes from 1987–93, and three of their catchments limed experimentally in 1987–88 so that the resulting changes in the abundance and distribution of common bryophyte taxa could be assessed. An additional nine streams were surveyed during 1987–89, 1992 and 1993 using the same methods to give a wider indication of the bryophyte communities in streams where liming might occur.Twenty‐nine bryophyte species were recorded from the wetted margins of these 15 upland streams. Percentage cover by individual species varied markedly, and was highest inNardia compressa(up to 71%). Cover by most other species was limited to less than 5%.Total bryophyte cover, and cover byScapania undulatafluctuated from year to year so that no responses to liming could be detected. However, cover byNardia compressadeclined significantly from 39% ± 21% SD to 5% ± 2% SD in treated streams following lime addition. Reference streams showed no such change, and no other taxa increased in abundance to replace the lostNardiain the 5 years after liming.Changes of this type, and their possible ramifications for invertebrates, will have to be considered where catchment liming i

ISSN:1052-7613    

DOI:10.1002/aqc.3270040403

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractLittoral microcrustacean (Ctenopoda, Anomopoda, Onchyopoda) samples, aquatic macrophyte data and chemical measurements were collected from 51 freshwater lochs in the Isle of Skye, Scotland, during the summer of 1989.Canonical correspondence analysis was employed to investigate correlations between the environmental data, the microcrustacean assemblages, and the aquatic macrophyte community types used for floristic classification of standing waters. Cluster analysis was used to classify lochs based on their microcrustacean assemblages.The major trends in microcrustacean distributions were related to pH, catchment area, macrophyte diversity and the distance from the sea.There was little correlation between the plant community types and microcrustacean assemblages.These results support the case for the development of an integrated approach to lake surveys so that correlations can be made between environmental variables and the distribution and abundance patterns of the plant and animal taxa of conservation interest.

ISSN:1052-7613    

DOI:10.1002/aqc.3270040404

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe study assessed differences that have occurred in macrofaunal assemblages of tidal flats subject to anthropomorphic impacts in north‐east England between 1931, when they were surveyed by Brady (1943), and 1991.The dominant members of the assemblages were the same for both surveys, and almost all the taxa recorded by Brady were present in 1991. There were also similar groupings of data from individual sampling stations by MDS ordination of the 1931 and and 1991 results.There is nevertheless evidence of change of two kinds. First, theArenicola/Scoloplos/Cerastoderma/Macomacommunity, which was characteristic of the entire tidal flats at Budle Bay in 1931, had been replaced in north‐west corner of the Bay by an oligochaete‐dominated community in 1991. Second, numerical densities of macrofauna were much higher in 1991 than in 1931 at each of the study

ISSN:1052-7613    

DOI:10.1002/aqc.3270040405

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractConservation principles developed for terrestrial habitats are frequently inapplicable in marine situations. This dichotomy arises because of different characteristics of the substratum and the existence of water as a ubiquitous marine dispersal medium. Physical differences are manifest in biological differences including reproductive mode, range requirements and levels of endemism. Marine systems differ further from terrestrial ones in that they have been subject to a very limited anthropogenic fragmentation, in contrast to land where many habitats have become highly fragmented. Estuaries and coral reefs, however, are naturally fragmented and particularly vulnerable because their substrata are strongly influenced by biological processes which are easily disrupted.One of the greatest threats to life in the sea is resource exploitation by man. In Africa, marine conservation is secondary to terrestrial conservation—only four countries in sub‐Saharan Africa have marine reserves. Marine reserves are effective in increasing population sizes of exploited stocks and supplementing stocks in adjacent areas through emigration. They also have the potential to provide recruits to exploited areas.Biogeographic patterns can be used to site marine reserves. We propose a middle/edge arrangement of ‘biodiversity reserves’, linked to biogeographical regions. Such reserves would achieve conservation of both representativeness (middle) and high diversity areas (edge). As a necessary corollary, we also suggest a second tier of reserves which has the specific purpose of improving local yields of exploited species.The sizes of biodiversity reserves should be determined by local habitat heterogeneity. Second‐tier reserves should be designed to maximize their benefit to adjacent areas while minimizing t

ISSN:1052-7613    

DOI:10.1002/aqc.3270040406

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe last population of the Nore freshwater pearl musselMargaritifera durrovensiswas surveyed each year from 1990 to 1994 in the River Nore, southern Ireland.The population has fallen from a ‘flourishing colony’ in the 1920s to an estimated 2000 in 1990 and 420 in 1994. No juvenile mussels were observed in any of the surveys.If life history data forMargaritifera margaritiferaare applicable toM. durrovensis, the population would need to be 20 times greater for successful recruitment.Although given special mention in the Bern Convention,M. durrovensiswas omitted from the European Union Habitats Directive, perhaps due to uncertainty regarding its taxonomic status as it shares characteristics with bothM. margaritiferaandM. auricularia.Immediate measures are required to prevent the extinction ofM. durrovensisincluding, (a) a captive breeding programme, (b) habitat restoration, and (c) formal recognition of its priority status within the Habitats Direct

ISSN:1052-7613    

DOI:10.1002/aqc.3270040407

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

ISSN:1052-7613    

DOI:10.1002/aqc.3270040408

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

ISSN:1052-7613    

DOI:10.1002/aqc.3270040409

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

ISSN:1052-7613    

DOI:10.1002/aqc.3270040401

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY