Wyniki wyszukiwania - Biblioteka Nauki

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Ecological indices as a tool for assessing pollution in El-Dekhaila Harbour (Alexandria, Egypt)

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Ismael A. A. , Dorgham M. M.

Oceanologia

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2003

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tom No. 45 (1)

121-131

EN

Statistical analyses of data concerning the phytoplankton standing crop and biomass were applied as a tool for assessing pollution in El-Dekhaila Harbour. Univariate and multivariate analysis showed a succession of three clusters associated with salinity and temperature variations. The first and third clusters comprised mainly diatoms and dinoflagellates. The second cluster, richer in species, was dominated by brackish water cyanophytes, chlorophytes and euglenophytes. The diversity index ranged from 0.08 to 2.41. A high diversity was associated with high evenness, reflecting the multidominance pattern of cluster (2). On the other hand, multiple correlations between salinity and standing crop, richness and evenness, were negative and significant, but positive with the diversity index. The ABC curve showed that the k-dominance curve for numerical abundance extends above that for the biomass when clusters 1 and 3 are dominant. Both curves coincide more or less for another segment of the curve but when cluster 2 becomes dominant the numerical abundance curve runs below that of the biomass. Such a pattern may indicate unpolluted or moderate to heavily polluted conditions in El-Dekhaila Harbour. The present study reveals that the combination of univariate and multivariate analysis with the ABC curve provides a promising tool for the characterization of phytoplankton dynamics under stress conditions. On the other hand, the phytoplankton community in El-Dekhaila Harbour is stressed not by the inflow of brackish water but rather by the inflow of sea water. This is indicated by the higher diversity and evenness, and by the ABC curve during the dominance of cluster (2).

2

Different Tillage and Residue Management Practices Affect Soil Biological Activities and Microbial Culturable Diversity in Rice-Wheat Cropping System Under Reclaimed Sodic Soils

88%

Chandra P. , Fagodiya R. K. , Rai A. K. , Singh R. , Sheoran P. , Prajapat K. , Singh A. , Verma K. , Verma V. K. , Yadav R. K. , Biswas A. K.

Journal of Ecological Engineering

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2024

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tom Vol. 25, nr 5

193--207

EN

Agricultural management practices alter soil characteristics and influence soil biological properties. Hence, a field trial was carried out to assess the 14-year long-term impact of tillage and residue management practices on soil biological activities and microbial population in a rice-wheat cropping system in two depths viz., 0–15 and 15–30 cm. Soil organic carbon levels differed significantly (p>0.05) across various treatments. Microbial biomass carbon, microbial quotient, and soil enzymatic activities were significantly greater (10–82%) in crop residue incorporation/retention treatments. Zero tillage with residue retention (ZT+R) had the greatest bacterial, actinomycetes, and fungi population, followed by reduced tillage with residue incorporation (RT+R). The ZT+R treatment had the greatest value of K-strategist and r-strategist, and was equivalent to RT+R across both soil depths. When compared to conventional tillage (CT), zero tillage (ZT) increased wheat yield by 9%. However, compared to CT, rice and rice-wheat systems had lower grain yields, whereas crop residue increased wheat and rice-wheat system yields by 10% and 6%, respectively. The findings of this long-term study show that residue management and tillage practices can enhance soil biological attributes while also supporting microbial diversity.

3

Short-term variation of zooplankton community in Cintra Bay (Northwest Africa)

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Berraho A. , Abdelouahab H. , Baibai T. , Charib S. , Larissi J. , Agouzouk A. , Makaoui A.

Oceanologia

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2019

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tom No. 61 (3)

368--383

EN

This is the first study that describes the spatial-temporal distributions of the zooplank- ton community and potential control factors in Cintra Bay. Zooplankton were sampled using a bongo net, 150 μm mesh size, during two surveys, in autumn 2015 and spring 2016, extending from the coast to the open sea. Fourteen zooplankton groups were identified, where copepods represented 49.1% and 92.5% of the total abundance in autumn 2015 and spring 2016, respectively. Tintinnids accounted for 39.7% and 4.7%, respectively. The total zooplankton abundance was higher in autumn (55 992 ind m-3) than in spring (2123 ind m-3). Nineteen species of copepods, belonging to 14 families, were identified. Euterpina acutifrons and Oithona nana were the most common and abundant species. The Acartiids were represented by three species (Acartia clausi, A. tonsa and A. bifilosa) in autumn and one species in spring (A. clausi). The copepods diversity was significantly different between the two seasons showing high values at the entrance and the center of the bay in autumn 2015 and in the southern half of the bay in spring 2016. The copepod structure was characterized by 13 species at different degrees of contribution in autumn 2015. In spring 2016, only four species qualified as indicator species although their contribution was not significant. Given its large opening on the ocean, Cintra Bay benefits largely from the conditions of the oceanic environment, particularly the upwelling. This situation is likely to have an impact on the spatiotemporal variability of the composition and distribution of zooplankton, especially the copepods.

4

Effects of some abiotic factors on the occurrence of aquatic mycobiota in lakes of the Drawa National Park

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Mazurkiewicz-Zapałowicz K. , Silicki A. , Gregorczyk A. , Biedunkiewicz A. , Wolska M.

Oceanological and Hydrobiological Studies

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2012

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tom Vol. 41, No. 4

8-16

EN

Effects of environmental factors, including acidity, temperature, oxygen, nitrogen, phosphate and total iron content, on the diversity of aquatic mycobiota in lake water were studied in two lakes in Northern Poland in 2005-2007. Fifty four species of fungi and fungus-like organisms were recorded in the sub-surface and benthic of both lakes. There were 36 and 45 species in Lakes Marta and Sitno, respectively. The greatest species diversity was observed with a higher content of oxygen and biogenic compounds in the surface water. Temperature and oxygen content were the most important factors affecting the distribution of mycobiota in lake water.

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Post-drainage secondary succession of soil nematodes on fen peat meadows in Biebrza Wetlands, Poland

63%

Wasilewska L.

Polish Journal of Ecology

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2002

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tom Vol. 50, nr 3

269-300

EN

After the drainage of fens and their permanent use as meadows, peat-forming process is being replaced by moorshing (mucking) process (mineralization and humification of peat), and then by turf-forming process. Secondary succession of soil nematodes was examined by using the chronosequence of meadow sites (period I: 1978-1983) and also by analysing the same sites 15-17 years later (period II: 1994-1997). The analysis was focused on the taxa (genera) of nematodes and on 19 to 29 parameters describing the community as total density, density of trophic groups, diversity indices and maturity indices. The pattern of successional changes was obtained for periods from 2 to 117 years after drainage. Natural not-drained fens were used for comparison. Soil structure and soil processes occuring over the time considered can be characterized as follows: soil moisture (by weight) 80-52% total soil porosity 90-77%, bulk density 0.16-0.44 (to 0.92) g cm^-3, total C content in soil 47-7% total N content in soil 4.4-0.5%, ranges in the sequence from Mt I (poorly moorshified soils) to Mt III (strongly moorshified soils). In natural fens, soil moisture was 80%, soil porosity 90%, bulk density 0.15-0.35 g cm^-3, and peat-forming processes (Pt) were continued. As compared with natural fens, drainage and management of fens was associated with increasing density of total nematodes and their components such as bacterivores, fungivores, facultative plant feeders, obligate plant feeders, omnivores, and predators. In drained fens the density of nematodes declined with succession with the exception of omnivores. The increase in the density of omnivores was positively correlated with the number of years after drainage (r=0.48, P<0.01). The indices of taxa diversity and maturity indices were postively correlated with years after drainage (P<0.001-0.05). In natural fens, ranges of density of all trophic groups were lower, and maturity indices higher than in drained peat meadows. The The mechanisms driving the first stage of succession in nematode communities (until about 30 years after the drainage of fens) seem to be tolerance to the droughts and to the excess of nitrogen what was accompanied with higher density of herbivores (mainly Paratylenchus). In later stages, interspecific competition is likely to play a more important role. Also a statistically significant relation was found of some taxa and parameters to peat type.