摘要:

AbstractLake Mikolajskie is seriously affected by Mikolajki town and tourism. The amount of sewage entering the littoral zone is increasing as also is the area of the artificially transformed shore. During the past 20 years the area occupied by macrophytes has decreased markedly. The decline ofPhragmites australis, changes in species composition, and reductions in biomass and in the depth‐range colonized by submerged plants have been observed. Simultaneously the biomass of algae has increased markedly. Animals characteristic of polluted sites have become more abundant. Changes in animal numbers result to a great extent from changes in the availability of natural substrates.Zonation of the occurrence of organisms has been observed for years on sites directly affected by sewage—quantitatively and qualitatively poor communities are found at sewage discharge points and the richer ones at a greater distance in the zone fertilized by diluted sew

ISSN:0020-9309    

DOI:10.1002/iroh.19880730402

出版商:Akademie Verlag, Berlin    

年代:1988

数据来源: WILEY

摘要:

AbstractSeasonal and vertical distribution, migratory patterns and reproductive effort in coexisting cladocerans were investigated in three humic lakes with different, but low phytoplankton abundances and varying fish predation pressure. Seasonal and vertical habitat or niche overlap varied, but were high within most pairs of species in all localities. Migration was conspicuous in presence of planktivorous fish, less so in the fish free lake. Despite algal densities below incipient limiting level (30–200 μg C I−1) and a low ratio (3–10) of algal to cladoceran biomass, zooplankton distribution and reproductive parameters were not clearly related to algal biomass.Bacterial biomass equalled 10–50% of phytoplankton biomass, while detritus by far was the largest of the particulate compartements. It was concluded that with a possible exception of the early summer algal bloom, additional carbon sources (bacteria, detritus) are important to cladoceran nutrition in these humic lakes. A large share of N‐ and P‐poor detritus in the diet would give zooplankton productivity limitation by food quality in terms of elemental composition rather than food quantity. This would permit coexistence even of species with rather high food overlap, but give low production rates for all species in agreement with the

ISSN:0020-9309    

DOI:10.1002/iroh.19880730403

出版商:Akademie Verlag, Berlin    

年代:1988

数据来源: WILEY

摘要:

AbstractAnin situmesocosm experiment was performed at neutral pH Lake O'Woods, West Virginia, to assess the impacts of acidification on the common planktonic rotiferKeratella cochlearis.This rotifer is typically replaced byK. taurocephaladuring the acidification of North American lakes. Despite a rapid pH reduction in this experiment (from 7.0 to 4.8 in 14 days), the abundance, mean body length and egg ratio ofK. cochlearisdid not decline in the acid treatment as compared to the untreated control. These results support the hypothesis thatK. cochlearisis acid‐tolerant, and suggest that its disappearance from acid lakes is the result of biotic interactions within the plankton, rather than the result of toxic effects of altered water chemistr

ISSN:0020-9309    

DOI:10.1002/iroh.19880730404

出版商:Akademie Verlag, Berlin    

年代:1988

数据来源: WILEY

摘要:

AbstractSeasonal and local chlafluctuations were examined at two depth ranges in Shoal Lake, a productive Precambrian Shield system. Water residence time in the study area was short, without permanent summer stratification. Chlafluctuations were significantly correlated with total molybdenum reactive phosphorus (MRP) and total inorganic nitrogen (TIN), but the types of relationships were different for the two nutrients. Chlawas also significantly positively correlated with total alkalinity and temperature, and inversely correlated with oxygen and light. MRP and dissolved organic matter appeared to be more important for near‐bottom chl than for surface chl. Principal component analysis identified 4 major dimensions in which the different locations could be compared in terms of seasonal chlafluctuation

ISSN:0020-9309    

DOI:10.1002/iroh.19880730405

出版商:Akademie Verlag, Berlin    

年代:1988

数据来源: WILEY

摘要:

AbstractMonthly sampling of calcium and magnesium in the in‐ and outflows of Dal Lake revealed high concentrations of both during summer. The monthly inputs, outputs and retentions of these alkaline earths were estimated. The lake on an overall basis showed the retention of calcium but not of magnesium. This was suspected to be related and affected by variable flushing rates of water. Most of the calcium and magnesium was present in sediments and only a small fraction in the water and in macrophytes. The calcium balance is discussed in relation to the P‐bala

ISSN:0020-9309    

DOI:10.1002/iroh.19880730406

出版商:Akademie Verlag, Berlin    

年代:1988

数据来源: WILEY

摘要:

AbstractThe benthic assemblages in two Central Chile nearby embayments were studied from quantitative samples collected from 15 sites at depths of 8–65 m. The macrobenthic infauna (<0.5 mm) of both bays was greatly dominated by polychaetes. Some 93 taxa were identified, of which 51 were polychaetes. The average macrofaunal abundance for all stations (15,021 ind. m−2) is very close to the values reported for the neighboring areas. Numerical classification and ordination (DCA) of sites resulted in three site‐groups mostly reflecting differences in the bottom sediments: the muddy‐bottom stations of Concepción Bay and the shelf‐associated stations, the sandy‐bottom stations of San Vicente Bay and an heavily polluted station at San Vicente port. Classification of species showed that the muddy‐bottom stations and the sandy‐bottom sites had characteristic species assemblages. The macrofaunal assemblages presented high dominance values, which were due to the high numerical abundances of a few species in

ISSN:0020-9309    

DOI:10.1002/iroh.19880730407

出版商:Akademie Verlag, Berlin    

年代:1988

数据来源: WILEY

摘要:

AbstractPotential nitrogen limitation to chlaproduction in surface waters of Saronicos Gulf, Aegean Sea was assayed using the algaPavlova lutherias the test organism. The oligotrophic and eutrophic water types of this area were compared byin situandin vitrochl a production estimations. Additions of ammonium alone as well as in combination with complete nutrient enrichment were made to the oligotrophic waters and the algal growth yield was determined and compared with the corresponding yield in unenriched water cultures. The results from routine nutrient analysis and bioassay experimentation support the view that nitrogen has a priority among the factors limiting phytoplankton growth in the Eastern Mediterranean Sea.

ISSN:0020-9309    

DOI:10.1002/iroh.19880730408

出版商:Akademie Verlag, Berlin    

年代:1988

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19880730409

出版商:Akademie Verlag, Berlin    

年代:1988

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19880730410

出版商:Akademie Verlag, Berlin    

年代:1988

数据来源: WILEY

ISSN:0020-9309    

DOI:10.1002/iroh.19880730411

出版商:Akademie Verlag, Berlin    

年代:1988

数据来源: WILEY