| 1. |
|
|
| 2. |
- Labrune, C., et al.
(författare)
-
Characterization of the ecological quality of the coastal Gulf of Lions (NW Mediterranean). A comparative approach based on three biotic indices
- 2006
-
Ingår i: Marine Pollution Bulletin. - : Elsevier BV. - 0025-326X. ; 52:1, s. 34-47
-
Tidskriftsartikel (refereegranskat)abstract
- The ecological quality of the Gulf of Lions coast was assessed using three biotic indices (H', AMBI and BQI). The three indices correlated positively. The positive correlation between AMBI and BQI was surprising and was mostly due to the fact that the dominant species Ditrupa arietina featured a low ES50(0.05) but was classified in GI by AMBI. Both H' and BQI were efficient in distinguishing impacted from un-impacted sites but AMBI was not. Differences between H' and BQI were mainly due to the scale used to translate indices in terms of EcoQ. The three indices were able to detect the major changes in macrofauna composition, which occurred in the Bay of Banyuls-sur-Mer during the last 40 years. However, the interpretations of such changes in terms of EcoQ differed between indices. These results are discussed relative to the characteristics of the tested indices. (c) 2005 Elsevier Ltd. All rights reserved.
|
|
| 3. |
- Riisgard, H. U., et al.
(författare)
-
Comparative study of water-processing in two ciliary filter-feeding polychaetes (Ditrupa arietina and Euchone papillosa) from two different habitats
- 2002
-
Ingår i: Marine Ecology-Progress Series. - 0171-8630. ; 229, s. 113-126
-
Tidskriftsartikel (refereegranskat)abstract
- A comparative study of feeding rates and structures was made with the 2 ciliary filter-feeding polychaetes Ditrupa arietina and Euchone papillosa from the Mediterranean Sea (Gulf of Lions, France) and the Gullmarsfjord (Sweden), respectively. The feeding rate (clearance) was measured as the volume of water cleared of 6 pm diameter flagellate cells (Rhodomonas sp.) per unit Lime. Most experiments were conducted at algal concentrations equivalent to about 0.4 to 3.8 mug chlorophyll a l(-1). The clearance rates of 'standard' 1.5 mg dry wt E. papillosa and 'standard' 3.0 mg dry wt D. arietina showed that the maximum weight-specific clearance rate was 114.7 ml h(-1) mg(-1) for E. papillosa and about 7 times lower, 15.7 ml h-1 mg-1, for D. arietina. A relative large tentacle crown in E. papillosa, resulting in the higher specific clearance rate, may be the evolutionary result of 'minimal scaling' and adaptation to extremely low food concentrations. When the algal concentration was increased from 2000 to 10 000 cells ml(-1) a 50% decrease in the clearance rate was observed in D. arietina, presumably because the gut capacity was exceeded. A more pronounced tendency to become satiated was found for E. papillosa. No tendency to reduce the filter-feeding activity at even very low algal concentrations was noticed in the 2 polychaetes, and the filtering activity of both worms seems to be a basically continuous process. Video-microscope observations of E. papillosa showed that suspended algal cells approaching the pinnules suddenly accelerate and move through an arc of over 180degrees to be delivered on the frontal side of the pinnule. The transfer takes place at a maximum distance (radius) of about 25 mum from the pinnule. Scanning micrographs show the compound lateral cilia to be 20 to 25 mum long in both D, arietina and E, papillosa and to consist of 1 row of 4 cilia. The feeding current is generated by these compound cilia, which, during their power stroke, catch up with the particles.
|
|
| 4. |
- Rosenberg, Rutger, 1943, et al.
(författare)
-
Benthic habitats in the northwest Mediterranean characterised by sedimentary organics, benthic macrofauna and sediment profile images
- 2003
-
Ingår i: Estuarine Coastal and Shelf Science. - 0272-7714. ; 57:1-2, s. 297-311
-
Tidskriftsartikel (refereegranskat)abstract
- A total of 36 benthic stations were studied in four areas in the oligotrophic Gulf of Lions and in one area of the severely disturbed Berre Lagoon in the northwest Mediterranean in October 2001. The study included analysis of sediment characteristics, particularly organic matter, and analyses of macrofauna and sediment profile images (SPIs). In the Gulf of Lions, values of superficial sediment biochemical characteristics were similar to available literature data, with the important exception of enzymatically hydrolysable amino acids (EHAA) and enzymatically to total amino acid ratios (EHAA/THAA) off the Rhone River and the city of Saint-Cyprien. All biochemical concentrations, but not EHAA/THAA ratios, were higher in the Berre Lagoon. A total number of 190 taxa were recorded, generally occurring in low density and biomass. In most SPIs from the Gulf, a deep infaunal bioturbation was observed, i.e. burrows and feeding voids were recorded in 85 and 62% of the images, respectively. This infaunal activity was associated with a mean depth of the apparent redox potential discontinuity (aRPD) in the sediment at 2.1-3.5 cm in the gulf and 0.2 cm in the lagoon. The benthic habitat quality (BHQ) index, summarising surface structures, subsurface structures and the depth of the aRPD, assigned most benthic stations in the Gulf to the benthic successional stages 11 or 111, i.e. fairly undisturbed habitats. Demersal trawling, however, probably was a disturbance to most muddy superficial sediments in the Gulf. Multivariate analysis (MDS) of the macrofauna and the SPIs both separated three groups of stations: muddy, sandy and those that were disturbed from the lagoon, but a few stations showed dissimilarities to this general pattern. Principal component analysis (PCA) resulted in the best correlation between faunal abundance and biomass and enzymatically available amino acids in the sediment. PCA grouped almost all stations into three separate groups: muddy, sandy and severely disturbed habitats, and the muddy habitat group was associated with high aRPDs and BHQ indices. It is concluded that SPI is useful for in situ analysis of infaunal bioturbation activity and redox conditions, and for benthic habitat classification in the oligotrophic northwestern Mediterranean and the disturbed Berre Lagoon. (C) 2003 Elsevier Science B.V. All rights reserved.
|
|
| 5. |
- Rosenberg, Rutger, 1943, et al.
(författare)
-
Effects of demersal trawling on marine sedimentary habitats analysed by sediment profile imagery
- 2003
-
Ingår i: Journal of Experimental Marine Biology and Ecology. - 0022-0981. ; 285, s. 465-477
-
Tidskriftsartikel (refereegranskat)abstract
- Demersal trawling causes one of the most widespread physical and biological changes in marine shallow and shelf sedimentary habitats: trawl otter boards may create furrows in the sediment surface, while trawl nets and attached weights scrape the sediment surface. As a consequence, benthic animals are disturbed or killed, and resuspension of particles increase. The impact of trawling on benthic animals has traditionally been analysed by changes in species composition and abundance, whereas frequency and distribution of trawl tracks are frequently analysed by side-scan sonar. We have used sediment profile images (SPIs) (30 x 22 cm) and observed furrows and other physical disturbances on the sediment surface that we attribute to trawling. In a manipulative experimental trawl study in Sweden (BACI design), significant impacts were found in trawled benthic habitats (73-93 m deep) compared with pre-trawling conditions and with reference areas. In particular, furrows from trawl boards had a severe ecological impact. In the Gulf of Lions (northwest Mediterranean), similar patterns were observed in the vast majority of 76 images taken at random at depths between 35 and 88 m in four different areas. Epifauna and polychaete tubes were generally either rare or not observed at all on trawled sediment surfaces. Burrows and feeding voids were, however, frequently present in some trawled areas and seemed to be comparatively less affected. Such biogenic structures in the sediment were generally associated with rather deep (3-4 cm) mean apparent redox profile discontinuities (aRPDs), which were measured digitally as the visible division zone between oxidised (sub-oxic) and reduced sediments. Increased roughness caused by the trawl boards acting on the sediment surface, e.g. depressions and protrusions, could have effects on sediment solute fluxes. (C) 2002 Elsevier Science B.V. All rights reserved.
|
|
