摘要:

AbstractThe relationship between two commonly co‐occurring filter‐feeders;Bosmina longirostrisandEudiaptomus gracilisat different nutrient levels, was investigated in bag experiments in Lake Gjersjøen. At the start of the experiment, the numerical relationship betweenBosminaandEudiaptomuswas less than 1 : 10, but during the experimental period, a strong increase inBosminaand a corresponding decrease inEudiaptomusand medium‐sized algae (5–25 μm) was observed. The shift fromEudiaptomustoBosminawas probably due to strong competition on mediumsized algae whileBosminain addition may utilize smaller algae and bacteria, not available toEudiaptomus. Their coexistence in the lake at much lower densities is probably due to a strong selective fish predation, suppressingBosmina.Daphnia longispina, not naturally occurring in the lake, showed strong competitive abilities in a fish

ISSN:0020-9309    

DOI:10.1002/iroh.19860710102

出版商:Akademie Verlag, Berlin    

年代:1986

数据来源: WILEY

摘要:

AbstractQuantitative zooplankton samples were obtained at four regular stations and one irregular station in Placentia Bay, Newfoundland between mid June 1974 and mid May 1976. Sampling was attempted fortnightly as regularly as weather conditions and competition from other ship users would allow. The results are compared with those obtained and previously published in a similar study from Conception Bay, Newfoundland in 1977 to 1978. There was a greater diversity of species in Placentia Bay, and for most species the numbers/m3were greater. The two bays are influenced by somewhat different current systems, and climatic conditions are a little milder and foggier in Placentia Bay. The same species were common in both bays, with copepods usually being the most important.Among copepods, two of the most important species namelyPseudocalanussp. andOithona similiswere less abundant in Placentia Bay, but this was offset by a greater abundance ofTemora longicornis.A few of the problems that require further investigation are outlined.

ISSN:0020-9309    

DOI:10.1002/iroh.19860710103

出版商:Akademie Verlag, Berlin    

年代:1986

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19860710105

出版商:Akademie Verlag, Berlin    

年代:1986

数据来源: WILEY

摘要:

AbstractThis account describes the comparative response of four species of benthic invertebrates to burial in terms of vertical migration and mortality, and provides a synthesis of studies and recommendations upon which to assess future impacts. The species featured were the bivalveMercenaries mercenaria, the amphipod crustaceanParahaustorius longimerus, and the polychaetesScoloplos fragilisandNereis succinea.There was evidence of synergistic effects on burrowing activity and mortality with changes in time of burial, sediment depth, sediment type and temperature. In sediment with silt‐clay,N. succineawas the most resistant species followed byM. mercenaria, S. fragilisandP. longimerus. In sediment without silt‐clay the order of percent mortality was reversed.Studies of surface water chemistry and sediment geochemistry showed that dissolved oxygen decreased significantly and ammonia and sulfide increased significantly between the surface and below 2.0 cm within a 15‐day period. Based on these results and physiological tolerances from the literature it was concluded thatM. mercenariaandN. succineawould be relatively resistant to chemical effects of spoil disposal, whereasS. fragilisandP. longimeruswould be less resistant to such effects.Vertical migration of benthic invertebrates through dredge disposal can be a viable mechanism of recolonization under certain conditions. Some effects of burial of benthos can be predicted based on morphology, behavior and physiology. These biological features were discussed with examples dealing with molluscs, crustaceans, and polychaetes. Finally, recommendations were made concerning the type of studies to provide additional data to aid management agencies in decision making about future dredging and disposal prac

ISSN:0020-9309    

DOI:10.1002/iroh.19860710106

出版商:Akademie Verlag, Berlin    

年代:1986

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19860710107

出版商:Akademie Verlag, Berlin    

年代:1986

数据来源: WILEY

摘要:

AbstractIn order to obtain a better understanding on the relationship between salt and fresh‐water masses in an estuary on the Northern Brittany coast, a study on the tidal dynamics has been carried out. A simple model for the calculation of the mean current velocities is proposed taking into account the estuarine topography, tidal parameters and river discharge. The model also estimates the Richardson, Froude and Reynolds estuarine numbers. These can be used in further studies on the particle transport in this estuar

ISSN:0020-9309    

DOI:10.1002/iroh.19860710108

出版商:Akademie Verlag, Berlin    

年代:1986

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19860710109

出版商:Akademie Verlag, Berlin    

年代:1986

数据来源: WILEY

摘要:

AbstractThe concern of this study has been the chemical composition ofDaphnia magna, the algae (Selenastrum capricornutum, Ankistrodesmus convolutus) it was fed, the two growth media in which the algae were cultured and the water (Lake Huron, Michigan, USA) in whichD. magnawas reared. A synthetic diet (fish chow + alfalfa) was used as a control. The effectiveness of these five diets on the health of theD. magnapopulations was ascertained by the weight and number of neonates thus produced. The diet,S. capricornutumcultured in an organic medium, produced the largest mean brood size and the heaviest neonates in unstressed populations. The synthetic diet produced the smallest mean brood size and the lightest neonates. Stressed organisms may produce smaller broods with heavier neonates than unstressed organisms. The evolutionary significance of this observation is discussed. Statistical studies suggest that daphnids maintained on the synthetic diet derived no demonstrable nutritive value from the diet in terms of elemental composition or amino acid production. A great similarity in patterns of amino acid quantity and type was noted in the algae and the daphnids. On further examination it was discovered that this pattern was widespread in other aquatic forms, bacteria, fungi, yeasts, casein and was common to a variety of birds and mammals. It may be suggested that products that are made and stored, such as lipids, are less uniform in pattern among widely diverse species than those that have to be produced and are not stored, such as amino acids.

ISSN:0020-9309    

DOI:10.1002/iroh.19860710111

出版商:Akademie Verlag, Berlin    

年代:1986

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19860710113

出版商:Akademie Verlag, Berlin    

年代:1986

数据来源: WILEY

摘要:

AbstractThe depth profiles and seasonal abundance of fatty acids in lipids from the particulate organic matter in the eutrophic Lake Nakanuma, Japan, were closely related to both photosynthetic activity and the distribution of phytoplankton. The changes in the relative proportions of the fatty acids suggest that their synthesis is directly related to the photosynthetic activity of phytoplankton.

ISSN:0020-9309    

DOI:10.1002/iroh.19860710114

出版商:Akademie Verlag, Berlin    

年代:1986

数据来源: WILEY