摘要:

AbstractA survey of the phytoplankton and nutrient levels in Goat Island Bay, northern New Zealand was carried out in 1981–82 and the data compared with an earlier survey in 1966–69. The contribution of nutrients from the inflowing creek was also measured. The only significant change was a doubling of the dissolved nitrate levels in the sea, which appeared to be related to increased nitrate levels in the freshwater creek. It is suggested that the increase is due to an increase in the farming and recreational use of the catchment area.The standing crops of phytoplankton in the bay showed no correlation with nutrient levels, but there were significant correlations with the radiation recei

ISSN:0020-9309    

DOI:10.1002/iroh.19850700202

出版商:Akademie Verlag, Berlin    

年代:1985

数据来源: WILEY

摘要:

AbstractThe Saguenay Fjord is characterized by very high run‐offs. The annual flow varies between 1.2 and 4.2 × 103m3. s−1. During the summer the surface salinity shows a sharp horizontal gradient (from 1 0/00 to 20 0/00). The surface phytoplankton, mainly freshwater and even some euryhaline species is submitted to salinity stress. Continuous culture experiments were conducted to study the susceptibility of this freshwater phytoplankton under different salinity conditions. Some pennate diatoms (dominant group) are found as relatively tolerant to salinity. Microflagellates have been found to be resistant to salinity up to 26 0/00. Chlorophyll concentrations and rates of primary production of those organisms are as high as those of the con

ISSN:0020-9309    

DOI:10.1002/iroh.19850700203

出版商:Akademie Verlag, Berlin    

年代:1985

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19850700204

出版商:Akademie Verlag, Berlin    

年代:1985

数据来源: WILEY

摘要:

AbstractLoop analysis is a qualitative network technique which is useful for delineating pelagic foodwebs and for predicting production relationships. Loop models were fitted to data sets for three lakes in Kejimkujik National Park, Nova Scotia. Using qualitative correlation signs, there was 80–89 percent agreement of model predictions and data values. Individual networks were integrated by summarizing linkages between pairs of variables. The resultant core network is a three‐layered structure with 5 nutrient, 4 algae, 1 detritus and 10 zooplankton variables. The phytoplankton components utilize different types of nutrient complexes in each lake. Bluegreen algae have a special relationship to ammonia in Beaverskin Lake. Crustacean zooplankton consume phytoplankton directly whereas rotifers are connected to the foodweb via the detrital pool.In contrast to the multivariate statistical results reported by Blouinet al.(1984), loop analysis furnished some robust evidence of the inherent structure in these plankton communities. Qualitative methodology also helps identify casual pathways in the ecological networks. The analysis illustrated which links are oscillating the most and which are expected to remain resilient with increasing perturbation. The models suggest several aspects of these communities that could be verified experimenta

ISSN:0020-9309    

DOI:10.1002/iroh.19850700205

出版商:Akademie Verlag, Berlin    

年代:1985

数据来源: WILEY

摘要:

AbstractPhysical‐chemical conditions, phytoplankton productivity, community structure and productivity of the macroinvertebrate benthic community were determined during 1976–77 in a subtropical reservoir. Physical‐chemical results revealed high nitrate and phosphate concentrations with highest values in the riverine segment. Large phytoplankton populations were present during most of the year. Phytoplankton productivity was high, producing an annual mean of 87 mg C · m−3· h−1(12 hours light day). High turbidity in the riverine segment limited phytoplankton productivity during winter and spring. Macrobenthos was dominated by chironomids (Chironomus, Procladius, CoelotanypusandTanypus) and oligochaetes (Limnodrilus). The annual mean benthic population was estimated at 1,626 · m−2with a mean dry weight of 0.66 g · m−2. Mean benthic species diversity was 1.80. A lacustrine‐riverine community gradient was revealed. Benthic productivity was 6.8 g · m−2· yr−1(dry weight) with aP:Bratio of 10. A low correlation was observed between benthic and phytoplankton productivity, and between phytoplankton standing crop and benthic macroinvertebrate numbers throughout the reservoir. Algal food supplies had little impact on the benthic community which was composed predominately of species which fed mostly on organic detritus. Stressful conditions caused by low dissolved oxygen concentrations probably inhibited development of the benthic community throughout the reservoir during summer months, while high sedimentation rates limited devel

ISSN:0020-9309    

DOI:10.1002/iroh.19850700206

出版商:Akademie Verlag, Berlin    

年代:1985

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19850700207

出版商:Akademie Verlag, Berlin    

年代:1985

数据来源: WILEY

摘要:

AbstractThe photosynthetic activity of dominant phytoplankton in eutrophic shallow lake was investigated by the autoradiographic method in 1979 and 1980. It was shown by light and dark field microscopy that all species of Cyanophyta (Oscillatoria redekei, Oscillatoria agardhii, Aphanizomenon flos‐aquae) were characterized by a continuously high uptake of NaH14CO3. Similarly high photosynthetic activity was observed during the occurrence ofCryptomonassp. and nanoplankton. Contrary to these observations, diatoms showed remarkably high portions of photosynthetically inactive biomass when their development was abundant. The reasons for this discrepancy between high biomass of diatoms and relatively low primary production (measured by the14C‐method and autoradiography) are discus

ISSN:0020-9309    

DOI:10.1002/iroh.19850700208

出版商:Akademie Verlag, Berlin    

年代:1985

数据来源: WILEY

摘要:

AbstractPrimary production was used to measure the response of phytoplankton to entrainment in once‐through cooling water at thermal electric generating stations. Ambient lakewater temperatures ranged from 1.0 to 20.5 °C. The maximum discharge temperature was 32.0 °C. There was no chlorination of cooling water at the stations studied. On a few occasions, primary production was stimulated following station passage by discharge temperatures which were approximately 10 °C above ambient lakewater temperatures of 4.5 to 8.5 °C. Differences in production levels were not apparent, however, following the return of discharge water to ambient lakewater temperature. There was no consistent response of phytoplankton to the temperature regimes tested, with production levels generally differing by less than 20 % as a result of station passage or temperature elevation alone. Entrainment was considered to have minimal impact on phytoplankton productivity in large open water bodies such as the Great

ISSN:0020-9309    

DOI:10.1002/iroh.19850700209

出版商:Akademie Verlag, Berlin    

年代:1985

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19850700211

出版商:Akademie Verlag, Berlin    

年代:1985

数据来源: WILEY

摘要:

AbstractFortnightly records of the biotic and abiotic conditions in a subtropical natural pond were made over a period of 14 months with a view to find out the abiotic causes of fluctuations in the zooplanktonic populations. Statistical analysis of simple correlations among the abiotic factors revealed direct relationships between water temperature, DO and pH and an inverse relationship between DO and ‐PO4at statistically significant levels (P<0.01). The relationships between the physical and chemical factors and the zooplanktonic groups were evaluated by partial and multiple correlation coefficients. The causes for variation in the populations were established by stepwise multiple regression analysis. The populations of copepods and rotifers, respectively, were correlated at the 5 % and 1 % levels of significance to conductivity and ‐PO4which might be indirectly affected by bicarbonates and phytoplankton growth. The occurrence of two peaks of zooplankton, one in winter and another in postsummer, were observed to follow theMicrocystis aeruginosabl

ISSN:0020-9309    

DOI:10.1002/iroh.19850700212

出版商:Akademie Verlag, Berlin    

年代:1985

数据来源: WILEY