| 1. |
- Andre, C., et al.
(författare)
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Fertilization efficiency and gamete viability of a sessile, free-spawning bivalve, Cerastoderma edule
- 1995
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Ingår i: Ophelia. - : Informa UK Limited. - 0078-5326. ; 43:3, s. 215-227
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Tidskriftsartikel (refereegranskat)abstract
- The fertilization biology of the free-spawning bivalve Cerastoderma edule was studied in the laboratory. Fertilization success declined drastically with decreasing sperm concentration. Viability of both eggs and sperm decreased with age so that no fertilization took place after 4-8 hours. A dilution model suggests that in the field sperm is rapidly diluted to concentrations that would result in very low fertilization efficiencies. The dilution process thus operates on a much smaller time scale than gamete ageing, indicating that most eggs are fertilized close to spawning males. However, it is also shown that under certain circumstances high concentrations of sperm may accumulate over dense populations of bivalves.
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| 2. |
- Andre, C., et al.
(författare)
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Species identification of bivalve larvae using random amplified polymorphic DNA (RAPD): differentiation between Cerastoderma edule and C-lamarcki
- 1999
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Ingår i: Journal of the Marine Biological Association of the United Kingdom. - 0025-3154. ; 79:3, s. 563-565
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Tidskriftsartikel (refereegranskat)abstract
- The polymerase chain reaction (PCR) was used to produce species-specific DNA markers (RAPDs) from two sibling cockle species and five other co-occurring intertidal bivalves. Amplification reactions with one single primer readily distinguished larvae and adults of Cerastoderma edule from larvae and adults of C. lamarcki, and from adults of Mya arenaria Macoma balthica, Scrobicularia plana, Venerupis pulastra and Mytilus edulis. Random amplified polymorphic DNA (RAPD) is suggested as a simple and quick method to determine species identity in taxa that are difficult to identify on the basis of morphological characters alone, such as marine bivalve larvae.
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| 3. |
- Lindegarth, Mats, 1965, et al.
(författare)
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Analysis of the Spatial Variability in Abundance and Age Structure of 2 Infaunal Bivalves, Cerastoderma-Edule and C-Lamarcki, Using Hierarchical Sampling Programs
- 1995
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Ingår i: Marine Ecology-Progress Series. - 0171-8630. ; 116:1-3, s. 85-97
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Tidskriftsartikel (refereegranskat)abstract
- Spatial variability in abundance and age distribution of 2 infaunal bivalves, Cerastoderma edule (Linnaeus, 1785) and C. lamarcki (Reeve, 1845), were quantified using hierarchical sampling programs. The scales investigated ranged between 100 and 10(5) m. Analyses of variance revealed significant variability in abundance among sites within bays (similar to 100 m apart) for both species and also among bays (similar to 1 km apart) for C. lamarcki. Mean age varied at several spatial scales. For both species, however, the scale contributing most to the variation was bays, which provided about 40 % of the total variation for each species. Randomization procedures were used to test the generality of previous observations of non-random distributions of year classes (namely number of year classes and dominance by single year classes). These analyses showed that for both species a spatial unit contained significantly fewer year classes and the most abundant year class was significantly more abundant than expected by chance. These results were consistent for all spatial scales except among plots (similar to 10(1) m apart) in C. lamarcki. The necessity to assess spatial patterns at a wide range of spatial scales is emphasized. Potentially important processes (focusing on larval supply and recruitment) which generate the observed patterns and general implications of spatial variability are discussed.
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| 4. |
- Lindegarth, Mats, 1965, et al.
(författare)
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Effects of trawling disturbances on temporal and spatial structure of benthic soft-sediment assemblages in Gullmarsfjorden, Sweden
- 1998
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Ingår i: ICES Journal of Marine Science. - 1054-3139 .- 1095-9289. ; 57, s. 1369-1376
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Tidskriftsartikel (refereegranskat)abstract
- Hypotheses on the effects of shrimp trawling on large benthic macrofauna in a previously protected Swedish fjord were tested in a manipulative experiment. Three trawled sites and three untrawled (control) sites were sampled 1-4 months before, and 8-12 months after, experimental trawling on a weekly basis. Multivariate analyses indicate large temporal changes in assemblages of benthic fauna at both types of sites. The Bray-Curtis dissimilarity measure was used to test the hypothesis that changes in assemblages through time at trawled sites were different from those at untrawled sites. Although changes in average assemblages (centroids) from the start to the end of the experiment were larger at trawled sites, Ihc re were marked differences among sites, and differences between trawled and untrawled sites were not significant. There were, however, differences in temporal and spatial variability in structure of benthic assemblages. Variability at untrawled sires tended to be smaller. Thus, spatial and temporal variability in the structure of assemblages after one year of trawling was larger at the trawled sites than at the untrawled sites. Trawling with this particular type of gear at the experimental frequency for approximately one year appears to cause relatively subtle changes in the overall structure of assemblages of large macrofauna compared with changes caused by other factors. Furthermore, the results suggest that tests of hypotheses of changed patterns of variability may be sensitive to detecting effects of impacts of disturbance from trawling. (C) 2000 International Council for the Exploration of the Sea.
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| 5. |
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| 6. |
- Lindegarth, Mats, 1965, et al.
(författare)
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Using an experimental manipulation of contaminants in intertidal sediments
- 1999
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Ingår i: Ecotoxicology. - 0963-9292. ; 8:6, s. 495-501
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Tidskriftsartikel (refereegranskat)abstract
- Manipulative experiments in the field are important tools, for improving understanding of disturbances, such as contaminants, causing environmental impacts. We tested a method to create patches of increased concentrations of metals in intertidal sediments. The method produced persistent concentrations of metals, which were as large as those observed in contaminated areas and it appears to be applicable in different habitats. The utility of this technique as a tool to improve predictions about environmental effects needs to be evaluated by repeated experimentation.
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| 7. |
- Roegner, C., et al.
(författare)
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Transport of Recently Settled Soft-Shell Clams (Mya Arenaria L.) in Laboratory Flume Flow
- 1995
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Ingår i: Journal of Experimental Marine Biology and Ecology. - 0022-0981. ; 187:1, s. 13-26
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Tidskriftsartikel (refereegranskat)abstract
- A laboratory flume was used to examine the retention of juvenile soft-shell clams (2 wk postsettlement) in sediment when exposed to flow. Clams resisted erosion until the initiation of sediment transport, after which they were rapidly advected from sections of test substrate. Comparisons between living and killed clams indicated that burrowing behavior was instrumental for maintaining position in flow I the critical erosion velocity for sediment movement. The ability of low density, shallow-burrowing juvenile bivalves to avoid transport as bedload or resuspended particles is probably minimal during erosional periods, despite that fact that the position of larger, deeper living individuals may be unaffected, In energetic regimes, infaunal recruitment patterns can be dominated by hydrodynamic forces affecting juveniles.
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| 8. |
- Viejo, Rosa M., et al.
(författare)
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The interactive effects of adult canopy, germling density and grazing on germling survival of the rockweed Ascophyllum nodosum
- 1999
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 187, s. 113-120
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Tidskriftsartikel (refereegranskat)abstract
- Mortality soon after settlement is typically high and spatial distribution of germlings is usually very variable in seaweeds. This is the case for Ascophyllum nodosum (L.) Le Jol, which is a very common brown alga on sheltered rocky shores of the northern Atlantic. In this paper, the interactive effects of several factors on the survival of germlings of A. nodosum were investigated using an experiment carried out on the Swedish west coast. The general hypothesis that the combination of littorinid grazing, adult canopy and germling density affect the survival of germlings was tested. Two densities of zygotes were seeded onto small outplant discs in the laboratory. After 4 wk, the discs were transplanted onto the shore in plots, which were composed of all possible combinations of adult canopy and Littorinid grazing. Germling survival was calculated at 2 different points in time (after 5 and 23 d on the shore). After 5 d, there was no effect of grazers in the presence of canopy. In contrast, in areas cleared of canopy, survival was extremely low where grazers were present, but high where grazers were removed. At this stage, higher survival was observed at low density under an adult canopy and the opposite trend was observed in cleared areas. Mortality rates were not constant over time. In the presence of gastropods, instantaneous mortality rates were higher during the first 5 d than over the whole experimental period. Thus, the first period constituted the mast vulnerable phase for A. nodosum germlings. After 23 d, there was a trend far germling survival to decrease in the presence of grazers, regardless of other factors. This result suggests that grazers may affect the patterns of recruit distribution at later stages and the transition probabilities to macrorecruits.
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