摘要:

AbstractThe effects of the planktonic blue‐green algae,Aphanizomenon gracile, Synechococcus elongatus, andMicrocystis aeruginosa, on survival, growth, and food uptake ofDaphnia pulicariawere determined.SynechococcusandAphanizomenonwere unsuitable food when offered alone, but did not affect the daphnids negatively when mixed withScenedesmus. Microcystiswas the only one found to be toxic. In pure suspensions of this blue‐green, the daphnids did not survive more than 48 hours; they lived a little longer ifScenedesmuswas supplied additionally. Growth was markedly reduced when only 50 μg carbon/l ofMicrocystiswas added to the normalScenedesmusfood. It ceased at a concentration of 250 μg C/l. This can be explained by the reduction of food uptake. Very small quantities ofMicrocystis(10 μg C/l) present in the normal food caused a significant reduction of the filtering rate. Filtering inhibition was associated with the cells. Filtrate ofMicrocystissuspensions was not effective. Thus, the daphnids must ingest the blue‐green cells in order to become toxified. Dual‐labelling experiments showed thatMicrocystiscells are filtered from the medium by Daphnia with the same efficiency asScendesmusand are not rejected. Toxicity ofMicrocystisis considered to be an effective defence mechanism against grazin

ISSN:0020-9309    

DOI:10.1002/iroh.19810660302

出版商:Akademie Verlag, Berlin    

年代:1981

数据来源: WILEY

摘要:

AbstractStudies had been carried out on the local non‐migratory whitefish. Spawning behaviour and light conditions on the spawning ground are recorded. After artificial spawning, embryonal development took place under controlled conditions and the larvae were reared. Detailed characteristics of swim bladder creation and differentiation of the digestive tract are given. Distribution and number of pollan larvae near the spawning area and in the open lake were examined. Data are presented concerning the growth rates of larvae and fry in captivity and under lake conditions. Ecological data related to other coregonids are discussed and compared with the present stud

ISSN:0020-9309    

DOI:10.1002/iroh.19810660303

出版商:Akademie Verlag, Berlin    

年代:1981

数据来源: WILEY

摘要:

AbstractThe Morphoedaphic Indices for several Sri Lanka inland water bodies (mostly ancient man‐made reservoirs) were calculated using conductivity and depth data. The relationship between Morphoedaphic IndexMEIand the annual catch of fishCwas found to be\documentclass{article}\pagestyle{empty}\begin{document}$$ C{\rm = 19}{\rm .0677 }MEI^{{\rm 0}{\rm .7050}} $$\end{document}.Using this equation, the annual potential yields were calculated. The stocking densities ofTilapiafingerlings needed to be stocked were then estimated taking into consideration the natural recruitment of fingerlings from the already existing stocks of reproducingTilapi

ISSN:0020-9309    

DOI:10.1002/iroh.19810660304

出版商:Akademie Verlag, Berlin    

年代:1981

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19810660306

出版商:Akademie Verlag, Berlin    

年代:1981

数据来源: WILEY

摘要:

AbstractSignificant differences were found in the extent to which massive coral species at Enewetak are excavated by boring organisms:Goniastrea retiformis, 7.9%;Porites lutea, 2.5%; andFavia pallida, 1.2%.While polychaetes constituted the most abundant and diverse group of coral associates, clionid sponges accounted for approximately 70–80% of skeletal damage. Clionid boring rates are initially very high but burrowing ceases when a particular burrow size (˜0.6 cm) or distance from the surface (≦2 cm) is reached.Most coral skeletal excavation occurs within 2 cm of a dead surface. Therefore, bioerosional damage to corals depends primarily on the amount of skeletal surface not covered by live coral tissue. Damage to skeletons is inversely correlated with colony size but is not correlated with coral growth rates or water depth. Massive corals have a potential escape in size from catastrophic bioerosion.Models relating 1) coral growth forms to skeletal density and stability in currents, 2) resistance of coral skeletons to breakage by water movement and suspended rubble, and 3) dead surface area on coral heads to bioerosional damage and consequent probability of detachment from the substrate, are prop

ISSN:0020-9309    

DOI:10.1002/iroh.19810660307

出版商:Akademie Verlag, Berlin    

年代:1981

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19810660309

出版商:Akademie Verlag, Berlin    

年代:1981

数据来源: WILEY

摘要:

AbstractA quantitative study of the phytoplankton and nutrients in Goat Island Bay, northern New Zealand, was carried out at two stations of depths 7 m and 20 m in 1966‐69. There were significant differences in the concentrations of the phytoplankton at the two stations, the deeper station having, in general, higher concentrations than the shallower.Low phytoplankton standing crops were found in winter when the increased run‐off from the land resulted in lower salinities, higher turbidity, and higher dissolved silicate levels. The spring growth of diatoms was dominated by small diatoms (Cylindrotheca closterium, Leptocylindrus danicus, Nitzschia pseudoseriata, Phaeodactylum tricornutum, andRhizosolenia delicatula). Occasionally it was dominated by a population of large centric diatoms (Chaetocerosspp.,Coscinodiscusspp.,Thalassiosiraspp.), but these appeared to be found in a separate water mass which entered the bay and displaced the resident water mass. A third water mass entered the bay in spring and was characterised by the coccolithophore Emiliana huxleyi and a lower temperature.During the summer diatoms dominated the phytoplankton population, but were replaced by dinoflagellates for a short period in aut

ISSN:0020-9309    

DOI:10.1002/iroh.19810660310

出版商:Akademie Verlag, Berlin    

年代:1981

数据来源: WILEY

摘要:

AbstractIn order to determine the efficacy of sampling benthic invertebrates to a depth of 100 mm as compared with 200 mm, the gravel substratum of an experimental recirculating stream was sampled to both depths. Except for 6 taxa which were significantly more numerous in the shallower samplers, there was no significant difference between the densities determined from the two depths.

ISSN:0020-9309    

DOI:10.1002/iroh.19810660311

出版商:Akademie Verlag, Berlin    

年代:1981

数据来源: WILEY

摘要:

AbstractThe genusCyprettaVAVRA, 1895 from Malaysia, Indonesia and the Philippines is reviewed. Currently, eleven species are known from these areas. Two new species are described and two species are redescribed. Remarks and diagnostic illustrations are given for the known species.

ISSN:0020-9309    

DOI:10.1002/iroh.19810660312

出版商:Akademie Verlag, Berlin    

年代:1981

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19810660313

出版商:Akademie Verlag, Berlin    

年代:1981

数据来源: WILEY