摘要:

AbstractThe purpose of this study was to determine the composition of the associated fauna of Delaware's oyster beds. Moreover the relative position of Delaware's oyster producing tributaries lends itself to testing the classic hypothesis concerning the effect of salinity on faunal distribution. Interaction of substrate was also studied. The local oyster beds are termed the bay beds which include planted and natural populations, and the river beds. From 1967 to 1971 approximately 800 samples have been collected and the majority of these were from the bay beds. In 1968 and 1969, 132 samples were systematically collected from the river beds and 19 from the bay beds. These were returned to the laboratory for special care in identification. Samples from fouling panels and oyster rafts provided additional species. 152 species were identified but only 133 species were statistically analysed because they were from the systematic collections. Nonparametric statistics were used. In order to facilitate analysis the top 23 species were selected for special treatment. In order of decreasing frequency of occurrence the species were:Sabellaria vulgaris, Conopeum tenuissimum, Panopeus herbsti, Nereis succinea, Palaemonetes vulgaris, Crassostrea virginica, Nassarius obsoletus, Polydora websteri, Membranipora tenuis, Garveia fransiscana, Bulanus improvisus, Diadumene leucolena, Aiptasiomorpha luciae, Melita nitida, Obelia longicyatha, Alcyonidium polyoum, Sertularia argentea, Crangon septemspinosa, Hydroides dianthus, Eurypanopeus depressus, Modiolus demissus, Parapleustessp., andHartlaubella gelatinosa.The diversity of species decreases up the estuary with decreasing salinity. Substrate can alter this pattern in particular cases. Within a given salinity range the presence of any firm substrate or mud influenced the nature of the community from epifaunal to infaunal. Four faunal units were recognized: the planted and natural beds, the four southern rivers, the Leipsic River, the Woodland Beach area. The Leipsic River area marks a critical transition zone with a rapid reduction in species. North of Woodland Beach brackish water conditions begin to prevail. The fauna was more diverse in late spring than in the fall but seasonality was not as marked as expected. The faunal composition of Delaware's oyster beds agrees with the cosmopolitan view of estuaries. The stability — time hypothesis proposed by SANDERS provides a theoretical basis to explain faunal distributions in Delaware's oyster community. The hardy nature and geologic history of this oyster community makes it a likely candidate as a sensitive indicator of environmental degradation in the estuar

ISSN:0020-9309    

DOI:10.1002/iroh.19730580202

出版商:Akademie Verlag, Berlin    

年代:1973

数据来源: WILEY

摘要:

AbstractTen cultures of phytoplankters, including four strains ofSkeletonema costatumfrom different origins, were used to improve some aspects of the bioassay technology. Special attention was paid to the preliminary nutrient limitation of the inocula.When the cells are maintained in nutrient starvation, their carbon, nitrogen, carbohydrates, proteins and above all chlorophyllacontents decrease. The minimum appears after a range of 2–7 days, according to species. The survival of these limited cells and their capacity to give rise to active growing cultures when sub‐cultured are different with species, but efficiency in the inocula they provide usually can occur only until the minimum content in cellular components appears.Starved cells and enriched cultures ofChaetoceros lauderiandSkeletonema costatumwere used to inoculate several samples of sea water, in order to test the effect of the starvation on the experimental results. It appears that the starved cells increase the sensitivity of the method, but they are more susceptible to substances limiting their growth. In the opinion of the authors the best way would be to use both starved and enriched cells as inocula, but, when this is impossible, cautiously starved cells should be used with unpolluted sea wat

ISSN:0020-9309    

DOI:10.1002/iroh.19730580203

出版商:Akademie Verlag, Berlin    

年代:1973

数据来源: WILEY

摘要:

AbstractComparative studies of the three known species ofEurycercus(including the new speciesmacrocanthusfrom Eastern Siberia described herein) demonstrate thatmacrocanthusis much more closely related tolamellatusthan toglacialisin many details of morphology, ontogeny, and biology. Its most distinctive character is a great enlargement of the middle clasping hook on the first trunk limb, with the front end of the animal being completely restructured to accomodate its function. Bothmacrocanthusandlamellatusbecome reproductive at a small size and have a high reproductive potential, enabling them to survive heavy predation, as by fish, selective for large individuals, which the size‐frequency distributions of the populations suggest is occurring. On the other hand,glacialisdoes not become reproductive until a much larger size, and its reproductive potential is smaller than in the other species, making it extremely vulnerable to predation concentrated on large individuals. Significantly, where it occurs in the coastal North Sea region, Iceland, and Greenland it is virtually restricted to water bodies without fish. The taxonlamellatussens. lat. appears to be a complex of closely related specie

ISSN:0020-9309    

DOI:10.1002/iroh.19730580204

出版商:Akademie Verlag, Berlin    

年代:1973

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19730580205

出版商:Akademie Verlag, Berlin    

年代:1973

数据来源: WILEY

摘要:

AbstractThe present paper deals with the Testacea living in several Mexican and Central American high‐mountain waters. A total of 127 species, varieties and forms including 11 new ones are detected. Faunistical, ecological, zoogeographical and taxonomical notes are given. The results of investigation are represented as diagrams and extensive illustrations are provide

ISSN:0020-9309    

DOI:10.1002/iroh.19730580206

出版商:Akademie Verlag, Berlin    

年代:1973

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19730580207

出版商:Akademie Verlag, Berlin    

年代:1973

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19730580201

出版商:Akademie Verlag, Berlin    

年代:1973

数据来源: WILEY