Feeding behaviour of adult Centropages hamatus (Copepoda, Calanoida): Functional response and selective feeding experiments     

Andrea Saage  Olav Vadstein  Ulrich Sommer 《Journal of Sea Research》2009,62(1):16-21

The feeding behaviour of adults of the marine calanoid copepod Centropages hamatus was studied in laboratory experiments with ciliates and phytoplankton as food sources. The ingestion rate of algal (flagellates, diatoms) and ciliate prey (oligotrichs) as a function of prey concentration could be described by a Holling type III functional response, with close to zero ingestion rates at concentrations below 5 µg C l^− 1. In general, ingestion of ciliates was higher than ingestion of algae, and maximum feeding rates by adult males reached were half the feeding rates of adult females at prey concentrations exceeding 50 µg C l^− 1. When diatoms and ciliates were offered together C. hamatus (both sexes) fed exclusively on ciliates as long as they contributed with more than 5% to the mixture. This indicates the capability of active prey selection and switching between suspension feeding and ambush predation. Therefore, the feeding behaviour of adult C. hamatus can be characterised as omnivorous with a preference for larger motile prey. This implies a trophic level above two, if there is a sufficient abundance of protozoan food available.  相似文献   

Suspended sediment balance for the mainstem of Changjiang (Yangtze River) in the period 1964–1985     

Marwan A. Hassan  Michael Church  Yunxia Yan  Olav Slaymaker  Jiongxin Xu 《水文研究》2011,25(15):2339-2353

Suspended sediment dynamics during the period 1964–1985 are examined along the mainstem of Changjiang (Yangtze River). The period represents a basin condition prior to major changes in land management policy and dam building on the river's mainstem. The downstream sediment dynamics reflect basin geology and topography and channel morphology. Sediment exchange within the mainstem was calculated by the development of reach sediment balances that reveal complex temporal and spatial patterns. There is relatively little sediment exchange in the upper, bedrock‐controlled reaches, with systematic increases in the downstream alluvial reaches. Degrading, transfer, and aggrading reaches were identified. Relations between input and output in all reaches were significant but no relation was found between sediment exchange and input/output. Comparison between ‘short‐term’ (22 years) and ‘long‐term’ (52 years) records demonstrates the importance of the record length in studying the suspended sediment dynamics in a large fluvial system. The longer record yielded better correlation and different trends than the shorter record. Sediment transfer (output/input ratio) changes downstream: the dominance of the upstream contributing area in sustaining the appearance of net degradation through most of the river system highlights the importance of reach length on characterisation of suspended sediment dynamics in large fluvial systems. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Projective ordination by SIMCA: A dynamic strategy for cost-efficient environmental monitoring around offshore installations     

Bernard G. J. Massart  Olav M. Kvalheim  Fred Olav Libnau  Karl I. Ugland  Kjell Tjessem  Karl Bryne 《Aquatic Sciences - Research Across Boundaries》1996,58(2):120-138

A method for environmental monitoring using benthic species profiles as input is developed in this work. The method, referred to as projective ordination, utilises local principal component modelling (SIMCA) to obtain a cross-validated model which spans the natural variation in a region around offshore oil-producing installations. The borderline between regions with disturbed and non-disturbed species communities is subsequently decided from the residual distribution. This distribution is used to design an approximate F-test for assessing whether a community at a particular sampling location is disturbed or not. If so, the nature of the disturbance is determined by projecting the data on the PC model.Projective ordination utilises information from previous surveys to define the permissible variation in species communities, i.e. the limit of the natural variation. In addition, the method is dynamic, in a sense that the sampling locations may vary from survey to survey.Furthermore, our analysis shows that the customary number of replicate samples per station can be reduced. Modelling with only four randomly chosen replicates out of the complete set of five for each sampling location, does not affect the model significantly. On the other hand, taking only 3 replicates into account leads to significant divergences.A model based on the 1990 and 1993 surveys at the Statfjord field is presented as an example of the technique.  相似文献   

Pre-23 magnetic anomalies between Jan Mayen and Greenland-Senja fracture zones in the Norwegian sea     

Terje Hagevang  Olav Eldholm  Inge Aalstad 《Marine Geophysical Researches》1983,5(4):345-363

Analysis of magnetic data between the Jan Mayen and Senja fracture zones indicates that the anomaly 24A-B sequence extends from the Lofoten Basin onto the outer Vøring Plateau. Anomaly patterns, including those on the conjugate margin, suggest that the pre-23 sea floor spreading was characterized by an unstable plate boundary between fracture zones. The pre-23 spreading rate was at least 2.5 cm yr^-1 which is remarkably high compared with the post-23 rates. An evolutionary model which assumes Cenozoic oceanic crust as far landward as the Vöring Plateau and Greenland escarpments is suggested.  相似文献   

Monitoring changes in abundance of gadoids with varying availability to trawl and acoustic surveys     

Godo  Olav Rune; Wespestad  Vidar G. 《ICES Journal of Marine Science》1993,50(1):39-51

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Tagging and recapture of Atlantic halibut (Hippoglossus hippoglossus) in Norwegian waters     

Godo  Olav Rune; Haug  Tore 《ICES Journal of Marine Science》1988,44(2):169-179

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Structural geology of the Huldra Field, northern North Sea—a major tilted fault block at the eastern edge of the Horda Platform     

Haakon Fossen  Jonny Hesthammer  Tord Erlend Skeie Johansen  Trond Olav Sygnabere 《Marine and Petroleum Geology》2003,20(10):1105-1118

The Huldra fault block is a rotated major fault block on the east margin of the Viking Graben in the northern North Sea. Unlike the rest of the Horda Platform area, the Jurassic section in the Huldra fault block was rotated more than 20° during slip on the listric Huldra fault, which forms a low-angle detachment beneath the Huldra fault block. The fault block is interpreted as resulting from marginal collapse of the Horda Platform after relief along the eastern margin of the Viking Graben built up in early parts of the middle to late Jurassic rifting history. The collapse resulted in NW directed transport of the Huldra fault block, consistent with a previously postulated change in extension direction from W–E to NW–SE toward the end of the Jurassic period. Minor faults within the Hulrda fault block are consistent with E–W extension and thus may have formed early during the late Jurassic rifting phase. Nevertheless, the crest (Huldra Field) seems surprisingly intact, considering its proximity to a major fault zone. Deformation bands studied from core material are non-cataclastic and concentrated in zones. Evidence for smearing along a cored fault surface indicates that minor subseismic faults may be sealing. Production data from the field indicate good communication between most wells, suggesting that the subseismic faults and deformation band zones that are present in the reservoir have relatively small influence on the flow of gas in the reservoir.  相似文献   

Relict Shorelines and Ice Flow Patterns of the Northern Puget Lowland From Lidar Data and Digital Terrain Modelling   总被引：1，自引：0，他引：1  

Dori J. Kovanen  Olav Slaymaker 《Geografiska Annaler: Series A, Physical Geography》2004,86(4):385-400

Airborne lidar data from the northern Puget Lowland provide information on the spatial variability and amplitude of raised postglacial shorelines, marine deltaic features and glaciomarine sediments deposited between approximately c. 12 920 and 11 050 ¹⁴C yr BP (15 960‐12 364 cal yr BP). Relict shorelines preserved in embayments on Whidbey and Camano islands (between 47°54′N and 48°24′N) are found up to an altitude of c. 90 m and record glacio‐isostatic movements attributed to postglacial rebound. The tilt of the regional minimum highstand sea level surface to the north of 0.80 m km^?1, with local variability from 0.25 m km^?1 to 0.77 m km^?1, is consistent with previous studies (Thorson 1989; Dethier et al. 1995). The local variability is related to the uncertainty in the depth of the water column above these features at the time of deposition and probable tectonic deformation. The information generated by these lidar data is most valuable in posing new research questions, generating alternative research hypotheses to those already formulated in the northern Puget Lowland.  相似文献   

Studies in the Welsh Quaternary: Vol. 4, No. 1. D. Q. Bowen (ed.). Cambria, 124 pp., Dept. of Geography,St. David's University College,Lampeter, Dyfed,Wales. £1.00     

Olav Slaymaker 《Quaternary Research》1978,9(2):261-262

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On the prograde rotation of asteriods     

Olav Hansen 《Icarus》1977,32(4):458-460

Sets of diameter determinations before and after opposition for the asteriods Ceres, Pallas, Vesta, and Fortuna have been studied statistically for indications of spin direction. All four asteriods are tentatively found to have prograde spin. For Ceres, that conclusion is virtually certain.  相似文献