摘要:

AbstractFactorial enrichment experiments with nitrate‐N, phosphate‐P and selenite‐Se, were conductedin situ, with natural phytoplankton assemblages, during two consecutive spring‐bloom periods (1983 and 1984) in Lake Erken, Sweden. Nutrient conditions, biomass indicators and algal physiological status, in experiments and in lake water, were compared. Characteristic peaks of phytoplankton, dominated by diatoms, developed in the lake in both years. In 1984, chlorophyllabiomass (30 μgl−1) reached almost twice that of 1983 (17 μgl−1). Inorganic P resources were depleted in both years, but inorganic N was exhausted only in 1984. In 1983,Stephanodiscus hantzschiiGRUNv.pusillusGRUN. KRIEGERcompletely dominated the biomass peak. In 1984,Melosira islandicav.helveticaO. MÜLLoccurred in great numbers along withS. hantzschiiv.pusillus.The growth rate ofS. hantzschiiv.pusillus, surplus phosphorus dynamics and potential alkaline phosphatase activity were different during the two spring periods. In the experiments, eight alternative nutrient situations were tested during four phases of the natural phytoplankton development. The algae responded to enrichments during the entire phytoplankton bloom in 1983 and 1984. Nutrient interactions were important, especially in 1983, and occurred most frequently during the late exponential phase, biomass maximum and declining phase in both years. Interactions between N and P were most common in 1983, occurring during the late exponential phase and biomass maximum. N and Se interaction occurred occasionally. Interactions between P and Se were more frequent in 1983 than in 1984. When nutrients interacted, the combined effect was generally smaller than the sum of their individual effects. P deficiency indicators and the experiments showed clearly that the bloom of 1983 was P limited. In 1984 no such clear pat

ISSN:0020-9309    

DOI:10.1002/iroh.19920770402

出版商:Akademie Verlag, Berlin    

年代:1992

数据来源: WILEY

摘要:

AbstractThe crustacean zooplankton in Lake Mahinerangi, a polymictic, mesotrophic reservoir, were studied for 19 months. The cladocerans,Bosmina meridionalisandCeriodaphnia dubia, had unimodal patterns of abundance with peak densities in summer; cyclopoids had a single peak of maximum abundance in autumn andDaphnia carinatashowed a bimodal pattern with peak densities in early summer and early winter. The strong seasonality in abundance of zooplankton in Lake Mahinerangi distinguishes this lake from other temperate lakes in New Zealand and may reflect its cool winter temperatures (<5 °C for 2 months). A calanoid,Boeckella hamata, bred throughout the year and was the dominant species numerically. Instar analysis indicated that there were at least three, and possibly four, generations per year. Instantaneous birth and death rates were low with annual mean values (0.036 and 0.057, respectively) that were 2‐3.5 times less than those recorded in a population of the same species in Lake Pounui, but within the range of those recorded in calanoid populations elsewhere in New Zealand. TheBoeckellapopulation in Lake Mahinerangi appears to be controlled largely by temperature, parasitism and food, with predation having no, or a negligible, effe

ISSN:0020-9309    

DOI:10.1002/iroh.19920770403

出版商:Akademie Verlag, Berlin    

年代:1992

数据来源: WILEY

摘要:

AbstractSeasonal succession of phytoplankton was studied in a eutrophic lake (Lake Aydat, Massif Central, France), from March to November 1985.An attempt is made to check the succession stages of the concept of ecological succession theory using either the H‐diversity index of SHANNONand WEAVERor the FRONTIER'Srank‐frequencies diagrams. A description of a stage 3 community was only possible through the use of the latter diagr

ISSN:0020-9309    

DOI:10.1002/iroh.19920770404

出版商:Akademie Verlag, Berlin    

年代:1992

数据来源: WILEY

摘要:

AbstractWater quality was determined on the Mahakam River floodplain from 1980 to 1987. Five water‐body types were distinguished, i.e. slow‐flowing and faster‐flowing rivers, lakes, small waterbodies and swamps. Water quality in large rivers was stable in the short but not the long term. In all other ecotypes variability was higher, with marked fluctuations being recorded in small waterbodies.A total of 147 indigenous freshwater fish species have so far been identified from the Mahakam. The zoogeographical consequences are discussed.Migratory patterns were inferred for four fish species,Helostoma temmincki, Leptobarbus hoe‐venii, Puntius schwanenfeldiiandThynnichthys vaillanti. JuvenileH. temmincki(<3 cm SL) migrate at the surface in schools of 40‐80 individuals at speeds of 0.48‐1.08 km · h−1, travelling 3.8‐8.6 km · h−1. Fecundities forP. schwanenfeldii(7,900–16,000 eggs),T. vaillanti(2,900–24,000 eggs) andH. temmincki(6,200–9,

ISSN:0020-9309    

DOI:10.1002/iroh.19920770405

出版商:Akademie Verlag, Berlin    

年代:1992

数据来源: WILEY

摘要:

AbstractThe associated macrofauna of four Aegean Sea sponge species (Agelas oroides, Petrosia ficiformis, Ircinia variabilisandAplysina aerophoba) was compared. The total number of individuals and species was found to be related to sponge volume for all sponge species.The associated macrofaunal weight per individual on all sponge species was negatively correlated with sponge volume. Sponge complexity, as measured by sponge surface area to biomass ratio, was not a consistent predictor of associated macrofauna abundance or diversity. Sponge macrofauna species were not host specific and their relative abundances differed among sponge species.

ISSN:0020-9309    

DOI:10.1002/iroh.19920770406

出版商:Akademie Verlag, Berlin    

年代:1992

数据来源: WILEY

摘要:

AbstractLaboratory investigations on life history parameters of 2 coexisting cladocerans (Daphnia obtusa. Moina brachiata) from a nearly temporary pond in South Germany revealed that the species have different temperature tolerances and temperature optima.D. obtusaexperienced the highest reproductive success at 15 and 20 °C and was able to survive and to reproduce at 2 °C but died at 30 °C. The reproductive success ofM. brachiatawas highest at 25 and 30 °C and the species could not withstand temperatures<15 °C and ≥35 °C. At temperatures between approximately 20 and 25 °C, where both cladocerans coexisted in nature,M. brachiatashowed a faster population growth due to its approximately twofold higher egg production rates (10–12 eggs female−1day−1compared to approximately 5 eggs female−1day−1in D. obtusa) and its shorter juvenile development (3.3 and 2.4 days compared to 6.3 and 5.3 days inD. obtusa);M. brachiataneeds generally only 3 molts to reach maturity whileD. obtusa

ISSN:0020-9309    

DOI:10.1002/iroh.19920770407

出版商:Akademie Verlag, Berlin    

年代:1992

数据来源: WILEY

摘要:

AbstractThe population dynamic of coexistingHydroporus‐species(adults) living in 2 secondary bog pools is described. Both pools are charakterized by a typical community structure, persisting over a period of 4 years. They also differ in physical and chemical properties. None of the 5 coexisting populations in a shaded pool is dispersed equally. Most individuals were kept in an area of 0–20 cm water depth. On an average 42–100 individuals/m2were recorded from a pool lying in a secondary birch swamp (Betuletum pubesce

ISSN:0020-9309    

DOI:10.1002/iroh.19920770408

出版商:Akademie Verlag, Berlin    

年代:1992

数据来源: WILEY

摘要:

AbstractThe growth of the skleleton and changes in biochemical constituents (proteins, carbohydrates and lipids) were observed in embryos (days 0 and 1) and larvae (2‐8 days) of the sea urchinParacentrotus lividusthat were starved (C 0) or fed low (1,000 cells ofHymenomonas elongata, C 1) or high (5,000 cells, C 5). Different batches of C 1 and C 5 larvae were fed first the 2nd, 3rd, 4th or 5th day after fertilization. Initiation of feeding 24 h after hatching slowed down the rate of increase in length of the larval appendages. A differential growth of skeletic rods (somatic and postoral rods) and variations in proteins weights shows the existence of a mixotrophic phase between endotrophic and planktotrophic phases. Best development occured in larvae which were first fed at the lower food level 24 h after hatching.On the 2nd and the 3rd day the somatic/postoral rod ratio is ≥1. This higher ration can be used to estimate the age of natural populations of lar

ISSN:0020-9309    

DOI:10.1002/iroh.19920770409

出版商:Akademie Verlag, Berlin    

年代:1992

数据来源: WILEY

摘要:

AbstractA comparison of two methods of zooplankton feeding experiments was performed in the Gulf of Finland. One was the advanced twin‐bathometer method (in situtechnique), the other — the “bottle method”. The main difference between the two methods is that it is not necessary to manipulate zooplankton to start an experiment in a twin bathometer, while manipulation is inevitable if the second method is used. In cases when the onset of the grazing experiment requires the manipulation of animals, the adaptation period lasts 2–4 hours and the optimal duration of experiment is 6–10 hours. If animals are not manipulated at the beginning of experiment, the adaptation period does not exist, the exposition time should not exceed 10 hours and the optimal duration of experiment is 2–4 hours. In long‐term experiments (up to 24 hours) the fertilization effect of the excretion of concentrated zooplankton may cause underestimation

ISSN:0020-9309    

DOI:10.1002/iroh.19920770410

出版商:Akademie Verlag, Berlin    

年代:1992

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19920770401

出版商:Akademie Verlag, Berlin    

年代:1992

数据来源: WILEY