摘要:

AbstractThe introduction of P and N loads exceeding 4‐14 and 1‐2 times, respectively, the amount of these nutrients stored in the waters of four lakes (dystrophic and eutrophic, stratified and unstratified) resulted in stronger, two‐phased changes in Ptotstanding stock and in rather insignificant and non‐directed changes in Ntotin all lakes. In the waters there was the immediate increase of Ptotfollowed by a decrease (together with a decrease in the N : P ratio) but the final level was still higher than in the control. In the top layer of off‐littoral sediments there was a temporary accumulation of nutrients followed by their release to a level significantly lower than that in the control year. Visible changes in the nutrient content and total biomass of above‐ground parts of macrophytes were noted only in the lake which was previously highly dystrophic, after it had been limed. This lake reacted strongest to the P load, and the release of nutrients from its deposits started simultaneously with fertilization. It is hypothesized that the reduction in the N : P ratio in the lake waters was mainly responsible for the lack of assimilation of further doses of P and that the acceleration of denitrification process caused by the higher overall lake productivity was responsible for the stabilization and removal of the N load. The activation of bacterial decomposition in the sediments due to the increase in lake productivity and sedimentation rate was considered as the probable reason for the acceleration of the nutrients release from the top layers of the sediments and their further physical transport to de

ISSN:0020-9309    

DOI:10.1002/iroh.19830680202

出版商:Akademie Verlag, Berlin    

年代:1983

数据来源: WILEY

摘要:

AbstractMicro‐ and meiofauna are the predominant consumers of diatoms on a brackish intertidal mudflat. The impact of grazing on the benthic diatom populations was studied by field observations and feeding experiments on a few abundant members of the community. Only small fractions of the microphytobenthic biomass and production are converted by herbivores. A hypothesis is presented explaining the growth kinetics and productivity of diatom populations and the inefficient transfer of carbon into herbivore foodchains. Data on feeding rate and population dynamics of the nematode species,Eudiplogaster pararmatus, are discussed in view of the seasonal succession of edible diatom specie

ISSN:0020-9309    

DOI:10.1002/iroh.19830680203

出版商:Akademie Verlag, Berlin    

年代:1983

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19830680204

出版商:Akademie Verlag, Berlin    

年代:1983

数据来源: WILEY

摘要:

AbstractMacrobenthic invertebrates of an industrialized seaport ecosystem were studied seasonally from October, 1977 through July, 1978. Five stations were selected along the Southern Branch of the Elizabeth River, Virginia. The benthic community was dominated by eurytopic species that were not affected by minor to moderate stresses induced by man's activities in the seaport. Caution is required when benthic communities of the lower polyhaline to mesohaline zones of an estuary are used to indicate the effects of anthropomorphic alterations.

ISSN:0020-9309    

DOI:10.1002/iroh.19830680205

出版商:Akademie Verlag, Berlin    

年代:1983

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19830680206

出版商:Akademie Verlag, Berlin    

年代:1983

数据来源: WILEY

摘要:

AbstractThe recovery of a temperate zone biotic community in a lotic freshwater habitat after acute chlorine poisoning was nearly completed in four months (May to September). This was facilitated by the water flow, which rapidly removed the toxic residues of the chlorine and transported organisms from the intact community upstream into the impoverished habitat. The first aggregation in the ditch after the chlorine was eliminated consisted of survivors, including members of species that failed to produce new generations. These were joined by pioneer species of the families Simuliidae and Chironomidae, the larvae of which appeared in massive numbers. This aggregation was displaced by a more diverse fauna as the macroflora and microbiota re‐established themselves, providing food and anchorage for the invertebrates. The populations of large fishes are slowest to return because a considerable amount of time is required for the migration and growth of the recruits. While the chronic intoxication of a habitat produces changes in community structure, an acute poisoning is followed by a nearly complete restoration of the original biota, the recovery time being determined by the proximity of recruits for resettlemen

ISSN:0020-9309    

DOI:10.1002/iroh.19830680207

出版商:Akademie Verlag, Berlin    

年代:1983

数据来源: WILEY

摘要:

AbstractFiltering rates of three species ofDaphniawere studiedin situby the14C technique during the summer in a lake with a water temperature of 20‐25°C (Lake Balaton, Hungary). The renewal time of gut contents proved to be 3‐5 min in each of the three species whether fed on natural or artificial food. From May to September, filtering rates ofD. cucullata, D. hyalinaandD. galeataaveraged 7.8, 10.3 and 9.2 ml ind.−1day−1, respectively. Identically long individuals of all three species had almost the same filtering rates in spring, whereas in summer animals of identical weights had similar filtering rates regardless of species because of the length variability of the helmets. The grazing rate of adult filter‐feeding crustaceans is suggested to be approximately 7

ISSN:0020-9309    

DOI:10.1002/iroh.19830680208

出版商:Akademie Verlag, Berlin    

年代:1983

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19830680209

出版商:Akademie Verlag, Berlin    

年代:1983

数据来源: WILEY

摘要:

AbstractThe seasonal succession of members of the invertebrate community of a temporary vernal pond in southern Ontario is described. Although succession was essentially continuous, 5 faunal groups are suggested, based on time of appearance and duration of active forms in the pond. Some species were found during virtually the entire aquatic phase, while others completed their life cycles in only 2‐3 weeks. Analysis of growth rates revealed many different patterns between species and groups. Analysis of community structure in terms of trophic status indicated shifts which coincided with the seasonal occurrence of the pond's potential food resources. Comparison of this fauna with that of a similar pond on Vancouver Island, British Columbia (some 2,400 km to the west) showed many similarities in niche occupancy, including 6 species in common. The biological characteristics leading to the success of these cosmopolitan species in temporary aquatic habitats is discusse

ISSN:0020-9309    

DOI:10.1002/iroh.19830680210

出版商:Akademie Verlag, Berlin    

年代:1983

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19830680211

出版商:Akademie Verlag, Berlin    

年代:1983

数据来源: WILEY