摘要:

AbstractAnalyses were made of subfossilEubosminaremains from two Berlin Lakes. The first postglacial eubosminid wasB. (E.) longispina.In Tegeler See it occurred from the Alleröd to Atlantic 2. In Lake Unterhavel it disappeared earlier in the Boreal.Bosmina (E.) longicornisoccurred in early Atlantic 1 resp. at the end of Atlantic 2 (Tegeler See).Bosmina (E.) c. coregoniappeared in Lake Unterhavel at the end of the Boreal, in Lake Tegeler See at early Boreal.Bosmina (E.) c. thersitesoccurred only in sediments of Lake Unterhavel beginning in Atlantic 2.No sign of a “morphological transition” between taxa found by HOFMANNcould be found in the two investigated lakes. The succession ofEubosminataxa seems to be mainly the result of immigra

ISSN:0020-9309    

DOI:10.1002/iroh.19930780102

出版商:Akademie Verlag, Berlin    

年代:1993

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19930780103

出版商:Akademie Verlag, Berlin    

年代:1993

数据来源: WILEY

摘要:

AbstractWe examined the diel vertical migration (DVM) of zooplankton in three lakes of western New York; Lakes Conesus, Lime, and McCargo. In all three lakes, the dipteran predatorChaoboruswas a more dramatic migrator than any of the cladocerans or copepods. In contrast, another invertebrate predator,Leptodora, seemed to have the least vertical dispersal. In Conesus Lake, following the evening ascent and upper‐water night‐positioning ofChaoborus flavicans, Daphnia pulicariaexpanded its own vertical range of dispersal thereby decreasing its degree of overlap withChaoborus.The vertical distribution ofDiaptomus siciliswas mostly below that ofDaphnia pulicaria, thus reducing possible competition for food resources. Poor oxygen conditions in the lower waters of Lakes Lime and McCargo restricted all zooplankton (exceptChaoborus) to an epilimnetic zone where the regions of niche overlap and predation were narrowed. Such annually‐induced restrictions on vertical dispersal are probably common features of numerous stratified lakes with hypolimnetic reducing conditions. No fixed pattern of vertical dispersal or migration is likely in lakes where stratification and non‐stratification follow each other seasonally. Vertical migration does provide some flexibility in niche separation, but the potential for chaotic behavior in interacting predators and prey may confound simple explanations

ISSN:0020-9309    

DOI:10.1002/iroh.19930780104

出版商:Akademie Verlag, Berlin    

年代:1993

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19930780105

出版商:Akademie Verlag, Berlin    

年代:1993

数据来源: WILEY

摘要:

AbstractSedimentation of phytoplankton was studied in the meso/eutrophic reservoir Saidenbach for two years and measured as biovolume in a sedimentation trap near the bottom. It comes to an annual average of 2.76cm3/m2× d (0.4… 10.9) and is statistically significant dependent on the free water concentration measured 14 days before. This allows flux to be reliably calculated without any direct measurement. The bottom is reached above all by diatoms which form 90% of the deposited algae. The sinking velocity of the diatoms is mainly determined by their physiological state: During growth phases low sinking velocities (0.1 … 2m/d) were found, while in decline phases they increased considerably (>6m/d). The highest average sinking velocities found among large diatoms were calculated forFragilaria crotonensis(3…4m/d), the lowest forMelosira italica(1.5…2m/d). The values forAsterionella formosa, Synedra acusandDiatoma elongatumwere between them. Turbulence has no influence on sinking velocity (usually, spring full circulation sees the highest sedimentary losses), but plays an essential part in the survival of the population in free water. Permanent redistribution prevents diatoms from sinking out from the euphotic layer, this “inoculation” making further development possible. On an annual average, phytoplankton forms approximately only one quarter of the whole trap sediment (max. 62%). The flux of the dry weight of seston (2.33g/m2x d on an average) reflects the changes in phytoplankton flux negligibly only and does not reveal any relation to it. so that seston flux is not suitable for determining phytoplankton sedimentation. But it is possible to calculate this at a probability of 65 to 94%, by using the free water concentration measured 14

ISSN:0020-9309    

DOI:10.1002/iroh.19930780106

出版商:Akademie Verlag, Berlin    

年代:1993

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19930780107

出版商:Akademie Verlag, Berlin    

年代:1993

数据来源: WILEY

摘要:

AbstractThe composition of the macrozoobenthic assemblages of the Evros Delta (North Aegean Sea) has been investigated by means of 4 replicate quantitative samples, collected at 35 sites. The information obtained from the numerical analysis of the faunal samples and the analysis of other data (values of the main physico‐chemical parameters) revealed the presence of a single community. The faunal composition of this community varies locally according mainly to the salinity and secondly to the particle size of the substrate. The community is described on the basis of its biological parameters and compared with corresponding assemblages from other area

ISSN:0020-9309    

DOI:10.1002/iroh.19930780108

出版商:Akademie Verlag, Berlin    

年代:1993

数据来源: WILEY

摘要:

AbstractInvestigations on the life histories of two cladocerans,Moina brachiataandDaphnia obtusa, in a small, nearly temporary pond in South Germany revealed thatM. brachiatais better adapted to fluctuating environmental conditions; the species dominated from May to October.D. obtusawas present in spring and autumn/winter but disappeared completely during the summer months. Both species coexisted for extended periods in spring and autumn; abundance ofD. obtusawas generally by an order of magnitute lower. Four periods of low water level were slightly preceded by or coincided with a decrease of clutch size, a decrease of the proportion of egg bearing females indicating that both species suffered from food shortage.Laboratory investigations on life history parameters showed that the two species have different temperature tolerances and preferences.M. brachiatashowed its highest reproductive success at 25 and 30°C but died at temperatures<15°C and ≥ 35°C.D. obtusaexperienced a broader temperature range (2 to 25°C) but could not withstand temperatures ≥ 30°C. Short term starvation periods (3d) caused the death ofM. brachiatafemales, whileD. obtusasoon recovered and reproduced when being refed.M. brachiatais a typicalr‐species with early reproduction, rapid development, high population growth rates and a high tendency to produce resting eggs;D. obtusapursues more the concept ofk

ISSN:0020-9309    

DOI:10.1002/iroh.19930780109

出版商:Akademie Verlag, Berlin    

年代:1993

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19930780110

出版商:Akademie Verlag, Berlin    

年代:1993

数据来源: WILEY

摘要:

Differences in Egg‐biology and Habitat Binding betweenProsimulium tomosvaryi(Prosimuliini) and Simuliini (Diptera, Simuliidae)Oviposition of the mountain black flyProsimulium tomosvaryi(Enderlein, 1921) (tribe Prosimuliini) takes place in May in the „Niederbergisch‐Märkisches Hügelland”︁ (North Rhine‐Westphalia). The eggs aestivate until late November. They differ in morphology, egg‐layers and germ band‐formation from tribe Simuliini. The development is negatively correlated with temperature: the embryo develops slowly, but without a pause at low temperatures (12°C) prevent development (temperature controlled dormancy). It is explained that distribution ofProsimuliumspecies in Central Europe is limited by the potency of the te

ISSN:0020-9309    

DOI:10.1002/iroh.19930780111

出版商:Akademie Verlag, Berlin    

年代:1993

数据来源: WILEY