Macrofauna impact on Ulva rigida C. Ag. production and relationship with environmental variables in the lagoon of Venice   总被引：2，自引：0，他引：2  

Balducci C  Sfriso A  Pavoni B 《Marine environmental research》2001,52(1):27-49

The grazing pressure of the macrofaunal invertebrates associated with the biomass of Ulva rigida in the Venice lagoon, their species composition and relationship with environmental variables have been studied. Fifteen sampling campaigns were carried out during different seasons both in the central basin of the lagoon, dominated by macroalgae (especially U. rigida C. Ag.) and in the southern basin, prevalently populated by seagrasses (especially Zostera marina L.). Replicate experiments were conducted in the field by exposing Ulva fronds in net cages of 10 and 1 mm (control) mesh-sizes to allow or prevent grazer entrance. The grazing pressure was determined as Ulva growth rate difference in the cages. In the absence of invertebrate herbivores, Ulva exhibited per cent relative growth rates (%RGRs) ranging from 1.5 to 9.5% day(-1), whereas in their presence the %RGRs were significantly lower (from -2.5 to 3.4% day(-1)) and frequently negative, especially in the station dominated by macroalgae. In this area, peak grazing rates and macrofauna biomasses of up to 8.6% day(-1) and 1,480 g m(-2) fwt (84.4 ash-free dry weight), respectively, were found. On the whole, during in field experiments in the Ulva-dominated station, herbivores removed an amount of biomass whose percentage ranged from 59 to 165% (mean: 103%) of the biomass yield (grazers excluded) found in the cages. These results suggest the possibility that grazers could act as an important factor affecting Ulva production in the Venice lagoon. Macrofauna populations were analysed by means of multivaliate techniques applied to biological variables only and biological and environmental variables together. Data of individual abundance, after a log(x + 1) transformation and the calculation of the Bray-Curtis matrix, were classified using the Cluster Analysis and ordinated by means of the Non-Metric Multidimensional Scaling (MDS) technique, in accordance with the strategies used in the study of multispecies distributions. Finally, biological and environmental variables were analysed together by means of correlation matrices and the Principal Component Analysis.  相似文献   

Wind-induced eddy motion in the lower St. Lawrence Estuary     

G. Mertz  V.G. Koutitonsky  Y. Gratton  M.I. El-Sabh 《Estuarine, Coastal and Shelf Science》1992,34(6)

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Numerical modelling of the seasonal variability of the North and Tropical Atlantic currents using an adaptation approach     

V. I. Klimok  G. Friedrich 《Physical Oceanography》1990,1(6):519-527

The paper reports computed data on the seasonal variability of the Atlantic Ocean currents which were obtained through numerical integration (using conservative difference schemes) of non-linear equations of hydrothermodynamics taking into account an upper quasi-homogeneous layer and the bottom topography. The seasonal variability of the meridional heat transfer is discussed. The results were obtained using an adaptation approach.Translated by Vladimir A. Puchkin.  相似文献   

JGOFS studies in the equatorial Pacific     

James W. Murray  Robert Leborgnelt  Yves Dandonneau 《Deep Sea Research Part II: Topical Studies in Oceanography》1997,44(9-10)

This special issue is the third and final volume containing results from the JGOFS Process Study in the equatorial Pacific. Most of the Study in the equational Pacific. Most of the contributions evolved either from the US JGOFS workshop in 1994 on the equatorial Pacific in Scottsdale, AZ or from the NATO Advanced Research Workshop on the Carbon Cycle of the Equatorial Pacific in 1995 in Noumea, New Caledonia.  相似文献   

A detailed survey near Mount Eratosthenes Eastern Mediterranean     

S. J. Tanner  C. A. Williams 《Marine Geophysical Researches》1984,6(2):205-222

A detailed marine survey made to the South West of Mount Eratosthenes is described. The results show the existence of a narrow zone of WNW trending deformed sediment west of the mount surrounded by an evaporite sequence in different stages of deformation.This work was intended to settle the conflict between the results of three previous interpretations of the tectonic structure of this area. We see the area being characterised by five areas with different degrees of tectonic deformation yet showing little causal relationship to overburden of Nile Cone sediments. A fault controlled cliff coincides with the previously described salt wall and strike slip fault yet we see no evidence for its diapiric origin nor positive evidence for strike slip motion along it. We concur with the previously observed area of higher free-air gravity anomalies termed the Eratosthenes tectonic zone, although it is traversed by several boundaries between areas of different deformation. Our results thus show some agreements and some re-interpretations of the observations. This complicated region is not yet fully understood however.  相似文献   

Concentration du chrome dans deux profils de l'ocean pacifique     

D. Grimaud  G. Michard 《Marine Chemistry》1974,2(3):229-237

Determination of total chromium on two profiles and chromium III on four samples of equatorial Pacific Ocean water have been carried out using coprecipitation of chromium from sea water with hydrous iron oxides, followed by ion-exchange separation and isotope dilution mass spectrometry. Results for two Pacific profiles show increasing total chromium concentration from surface to 250 m. The Cr concentration appears to be different below 1,000 m, with nearly homogeneous concentrations for the first profile and regularly increasing Cr concentrations from 0.330 to 0.550 μg/l at 3,900 m for the second one. Results for Cr(III) show that trivalent species are dominant in these samples.  相似文献   

Advances in Vent, Seep, Whale- and Wood-Fall Biology     

Lisa A. Levin  James P. Barry  Horst Felbeck  Craig R. Smith  & Craig M. Young 《Marine Ecology》2007,28(1):1-2

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Algorithm for non-hydrostatic dynamics in the Regional Oceanic Modeling System     

Y. Kanarska  A. Shchepetkin  J.C. McWilliams 《Ocean Modelling》2007,18(3-4):143-174

A non-hydrostatic algorithm for the Regional Oceanic Modeling System (ROMS) is proposed. It is based on a decomposition technique for hydrostatic and non-hydrostatic pressure. The algorithm has a pressure-correction scheme with split-explicit time-stepping for baroclinic and barotropic vertical modes with a free surface. The algorithm implementation requires solving a Poisson equation for a non-hydrostatic pressure that has a non-symmetric matrix in discrete form. The efficiency of a different class of solvers and preconditioners were tested. The algorithm is successfully implemented with several examples where non-hydrostatic effects are important. These include standing external gravity waves; strongly nonlinear internal wave generation and transformation; stratified shear instability and its associated mixing; and nonlinear internal tidal generation over a ridge. The corresponding changes in the pre-processing and post-processing infrastructure in the existing hydrostatic ROMS code were performed to implement parallel elliptic solvers and a new set of dynamical equations.  相似文献   

Comparison between zooplankton data collected by the Continuous Plankton Recorder survey in the English Channel and by WP-2 nets at station L4, Plymouth (UK)     

Eurgain H. John  Sonia D. Batten  Roger P. Harris  Graeme C. Hays 《Journal of Sea Research》2001,46(3-4)

Zooplankton sampling has been carried out by the Continuous Plankton Recorder (CPR) survey since the 1930s enabling the study of long-term changes in plankton populations, the elucidation of seasonal patterns of abundance, and more recently providing zooplankton biomass estimates for ecosystem models. Data for zooplankton abundance collected by CPR tows in the Western English Channel (between 1988 and 1998) were compared to vertically integrated samples collected from station L4 off Plymouth, UK. Comparisons were made for locally abundant copepods (including Acartia, Calanus, Para/Pseudocalanus, Centropages, Oithona and Temora) collected by CPR and WP-2 nets. All dominant species recorded at L4 were also common to the CPR data. However, the position of the taxa in the two datasets was not equivalent. Seasonal cycles revealed by CPR data were significantly similar to those recorded throughout the water column at L4 for most taxa. However, absolute levels of abundance differed for the two datasets: abundances were underestimated by CPR samples when compared to those of vertically integrated samples by a factor of between 2 and 35, with the exception of Centropages. The differing mesh sizes (200 and 270 μm) of the WP-2 net and CPR mesh could only partially explain these differences in abundance, implying that the behaviour of individual taxa and their depth in the water column also influenced the abundance recorded.  相似文献   

Measurement of DNA single-strand breaks in gill and hemolymph cells of mussels, Mytilus sp., collected on the French Atlantic Coast     

Akcha F  Tanguy A  Leday G  Pelluhet L  Budzinski H  Chiffoleau JF 《Marine environmental research》2004,58(2-5):753-756

DNA single-strand breaks were measured by the comet assay in both gill and hemolymph cells of mussels collected in 3 sampling areas of the French coast (Pointe du Castelli, Pen Bron and Saint-Nazaire Harbour). Whole mussel tissue samples were also collected for the chemical determination of PAH, PCB and heavy metal concentrations. In mussel, a higher level of DNA strand breaks was measured in gill than in hemolymph cells (p < 0.01). Despite a factor of contamination from 2 to 3 between sites, no difference in the extent of mussel DNA strand breaks was shown between sampling locations (p > 0.05), questioning the sensitivity of the assays used in biomonitoring studies.  相似文献