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Seasonal characteristics of nutrient and nutrient structure in the Yangtze River estuary

Li Lei, Xv Guodong, Zheng Yingjie, Jiang Mei

Archives of Environmental Protection

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2023

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Vol. 49, no 3

115--122

EN

This data article aimed to evaluate the influencing mechanisms of the nutrients and the level of eutrophication in the Yangtze River estuary. The seasonal characteristics of nutrients (dissolved inorganic nitrogen (DIN), SiO3-2–Si, and PO43-P) in the seawater of the Yangtze River estuary were analyzed by conducting surveys in spring and summer of 2019. The findings revealed that the concentrations of all nutrient at the surface and bottom layers were lower in spring compared to summer. NO3–N was typically the major form of DIN. Runoff was identified as the primary source of DIN and SiO32−–Si, while PO43−–P originated from a various sources. The SiO32−–Si, while PO43−–P values in the surface and bottom layers during the spring and summer were higher than the Redfield values, indicating an imbalanced nutrient distribution. Furthermore, discrepancies were observed in the distributions of DIN/PO43−–P, SiO32−–Si/DIN, and SiO32−–Si/PO43−–P in the Yangtze River estuary. Through an examination of the ratio of DIN/PO43−–P absorbed by phytoplankton, PO43−–P was identified as a potential limiting factor for nutrition in the sea area of the Yangtze River estuary during spring and summer. The Eutrophication Index (E) values for both spring and summer were found to be higher than the eutrophication threshold, indicating severe eutrophication in the studied sea area.

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Zabieg krótkoterminowej biomanipulacji ekologicznej zastosowany w trzech śródleśnych płytkich jeziorach

Czerniawski R., Sługocki Ł, Domagała J., Pilecka-Rapacz M.

Rocznik Ochrona Środowiska

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2015

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Tom 17, cz. 2

1207--1223

EN

A crucial factor affecting the rate of eutrophication is the characteristics of the catchment area of lakes. The most visible result of excessive eutrophication is rapidly deteriorating transparency of waters in the summer which is caused by rapid development of planktonic algae. Another symptom of this process is gradual overgrowth of water reservoirs and watercourses by macrophytes. Hence, in order to improve the quality of water in these lakes the renovation treatment is applied. Lakes restoration can be made in many ways: physical, chemical and biological. The chemical and physical methods of lakes restoration are invasive and controversial. However, one of the relatively not invasive methods of lakes restoration is ecological biomanipulation. The goal of biomanipulation is to reduce the concentration of harmful phytoplankton, by the stocking of predatory fish triggers a trophic cascade with decreases in the biomass of smaller-bodied fish, e.g. cyprinids, increases in the biomass of herbivorous zooplankton, and decreases in the biomass of harmful phytoplankton. In some cases plankton-eating fish have been removed directly by lake managers. In addition, the removal of bottom-feeding fish from shallow lakes leads to increases in rooted vegetation and increased water clarity as the rooted plants stabilize the sediments. This transition involves a trophic cascade, as herbivorous zooplankton increase in biomass and consume phytoplankton, but also involves the direct effects of rooted vegetation on sediment stability and nutrient cycling. The most frequent cause of fast eutrophication is the runoff of untreated sewage directly into the waters of lakes and rivers or the excessive runoff of biogenic compounds from agricultural catchment areas. Forest lakes because of far distance from agglomeration and agricultural areas are in lesser extent exposed on the human pressure. Generally, one unfavorable variable affected these lakes is angling pressure. Thus, due to the lack of pollution and the relative stabilization of the mid-forest lakes they are a good place to conduct the ecological biomanipulation. The aim of the present study was to determine the short-term biomanipulation effectiveness in three shallow forest lakes. Biomanipulation was performed by stocking in 2012 to these lakes a summer fry of pike (200 ind. ha-1) and zander (150 ind. ha-1). Before the biomanipulation (in 2011) a control study of physic-chemical parameters, ichthyofauna and zooplankton composition were made. After the biomanipulation (in 2014) the same control study were conducted. Before and after the biomanipulation period significant changes in values of physic-chemical variables were not observed. Similarly, a slight changes in ichthyofauna composition between these two period occurred. The roach and bream were the biomass dominants. Only the zooplankton composition obtained pronounced changes, but statistically not significant. The most visible differences in zooplankton abundance concerned cladocerans – group that the most affect the phytoplankton decreasing. After the biomanipulation abundance of cladocerans increased from 31% to 67%. According to the results, it can be concluded that the biomanipulation time in study lakes was too short to make significant changes. To get a better effect of biomanipulation a successive stocking with summer or autumn fry of pike and zander should be conducted, even in 1000 ind. ha-1. Finally, we can assume that in the forest, shallow, highly eutrophic lakes a biomanipulation with predatory fish may be sufficient for their effective restoration.

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Restoration of subalpine species-rich grasslands: short-term vs long-term changes in the density and diversity of above-ground insects

Karg J., Kujawa K., Manhart C., Marschalek H., Neugebauer K. R., Sachteleben J.

Polish Journal of Ecology

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2015

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Vol. 63, nr 1

142--158

EN

Due to decrease in the area of extensively managed, semi-natural grasslands, that contribute to high biodiversity level preservation, the conversion of highly productive meadows to extensively managed, species-rich grasslands is now regarded as an important task for nature conservation. The aim of this long-term study was to assess the significance of restoration measures for diversity and trophic structure of above-ground insect community. That study challenges some weaknesses of previous studies as it was conducted with the use of suction trap enabling quantitative analyses of the changes in most insect taxa, and in a long time-span (1992–2005) in a set of permanent plots. The study area was located in a subalpine zone in Bavaria, near Laufen (Germany). The restoration process was initiated in 1996 by a cessation of fertilization and reduction of number of mowing to 1–2 per year. The changes in insect density and diversity (number of families) were monitored in ten restored and two reference plots with the aid of a suction trap. The changes in the insect community recorded during 14 years support findings from other studies that response of insect community to restoration process is usually slow on average. The short-term comparison in 2004–2005 between the restored and reference plots show that the first ones were characterized by more diverse (in term of family number) insect communities (as a whole as well as in guilds of predatory and parasitic species). From the other side, the long-term trend analysis shows that since 1998–2000 insect diversity and abundance was declining. Also trophic structure is fluctuating without clearly defined trend. These findings are in line with the results of the analyses of taxonomic composition similarity. They did not support the expectations neither that difference between initial and current taxonomical composition in a restored plot increases in time (mainly because of incoming new species), nor that spatial heterogeneity of insect assemblages should increase. However, spatio-temporal insect interactions between sample plots (located close to each other), linked to high movement ability of many insect taxa, could mask the changes in insect community caused by restoration.

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The structure of psammic rotifer communities in two boreal lakes with different trophic conditions : Lake Võrtsjärv and Lake Saadjärv (Estonia)

Lokko K., Virro T.

Oceanological and Hydrobiological Studies

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2014

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Vol. 43, No. 1

49--55

EN

Psammon communities are still poorly studied worldwide. The aim of the present study was to establish the structure of psammic rotifer communities including their diversity and quantitative parameters. A total of 41 rotifer taxa were found in hydro-, hygro-, and euarenal zones of eutrophic Lake Võrtsjärv and mesotrophic Lake Saadjärv during the study carried out in Estonia in 2008, including 11 rotifer species new to Estonia. In L. Võrtsjärv, the predominant rotifer taxa were Bdelloidea and Lecane psammophila. L. psammophila dominated in July and August and bdelloids prevailed in the rest of the year. In L. Saadjärv, the most abundant taxa were Lepadella ovalis, Keratella hiemalis, and Cephalodella megalocephala. The psammic rotifer community of L. Saadjärv proved to be more diverse than that of L. Võrtsjärv. Microphagous rotifers were dominant in L. Võrtsjärv. Raptorial feeders dominated in L. Saadjärv in summer and autumn and were more abundant at sites with coarser sand and low plant density.

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Soil and litter macrofauna in shelterbelts and in adjacent croplands: changes in community structure after tree planting

Olechowicz E.

Polish Journal of Ecology

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2007

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Vol. 55, nr 4

647-664

EN

Studies were carried out in the vicinity of Turew near Poznań (Western Poland) in the years 2003 and 2004 in three midfield shelterbelts of different age (150, 11, 6 years old) and along two transects across shelterbelt (6 and 11 years old) >ecotone> field at distance 15 and 50 m from the shelterbelt. The field located in deforested area was treated as the control. The studies were aimed at estimating the changes in community structure (composition, density, biomass) of soil and litter macrofauna, (mainly dipteran larvae), related to shelterbelt age both within shelterbelts as in adjoining fields. The results were compared to previous studies carried out in 1999-2000 in the same agricultural landscape. The density and biomass of soil and litter macrofauna were many times higher in shelterbelts (2824-870 ind. m[^-2] and 3782-521 mg.d.wt. m[^-2]) than in fields (483-53 ind. m[^-2] and 101-12 mg.d.wt. m[^-2]) and increased with the age of planted trees. The same was true for taxonomic richness. Ecotone zone of both transects was characterised by the greatest density and biomass of animals, mainly those of mobile epigeic animals, particularly the ants. The density and biomass values were declining in the field with the increasing distance from the shelterbelt. Across the transect of an older (10-11 years old) shelterbelt and adjacent field the density and biomass of studied animals were higher in all plots than across the younger (5-6 years old) one. It can be concluded, that the effect of the shelterbelt increases with age of planted trees. The results confirm the previous suggestions of the enhancement of the field macrofauna by forested strips. The highest similarity in taxonomic and dominance structure was found between the shelterbelts and their ecotones and they differed significantly from those in the field.

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Soil-litter macrofauna in the mixed forest and midfield shelterbelts of different age (Turew area, West Poland)

Olechowicz E.

Polish Journal of Ecology

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2004

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Vol. 52, nr 4

405-419

EN

The paper deals with the composition, density and biomass of soil-litter macrofauna in four midfield shelterbelts of different age and, comparatively, in the neighbouring mixed forest. The increase was observed along with the shelterbelt ageing of: 1) numbers of all macrofauna and particularly of some taxa (Symphyla, Chilopoda, coleopteran larvae and imagines and some dipteran larvae), 2) biomass of all macrofauna, of soil fauna (Group I) and of coleopteran larvae, 3) share of zoophages in all macrofauna and in dipteran larvae, 4) share of phytophages in coleopteran larvae communities, 5) average individual biomass, 6) taxonomic richness and the biodiversity (H'), 7) similarity of composition and domination structure of all macrofauna and of dipteran larvae to those in forest communities. The decrease of density of dipteran larvae, particularly of Chironomidae and Sciaridae and the share of saprophages in all macrofauna and in dipteran larvae was also observed. Successional stages of more numerous invertebrate taxa in newly established woodlots are described. Dipteran larvae were the pioneers in colonising newly established shelterbelts, particularly larvae from two families: Chironomidae and Sciaridae. Their combined contribution to the total density of dipteran larvae was 92%.

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Nematofauna of the shelterbelts in the agricultural landscape

Wasilewska L.

Polish Journal of Ecology

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2004

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Vol. 52, nr 2

99-113

EN

Trophic structure, number and density of taxa, generic diversity, and maturity indices were compared for soil nematode communities inhabiting a 170-year-old shelterbelt, 6-year-old shelterbelt, and a maize field adjacent to the younger shelterbelt. The study was conducted in an area of long-term research near Turew (Wielkopolska Region, West Poland). Sampling sites in the crop field were located at distances of 0.5 m, 10 m and 50 m from the younger shelterbelt. In the soil of shelterbelts more taxa occurred in comparison with the cropland, the index of generic diversity was higher, the dominance of nematodes of the class Secernentea (r-strategists s.l.) over Adenophorea (K-strategists s.l.) was lower, community maturity indices and bacterivore maturityindex were higher, and the ratio of plant parasite index to maturity index was lower, providing evidence for a more advanced stage of succession in the shelterbelts. In the maize field, fungivorous and plant feeding nematodes predominated, with a strong dominance of one of the taxa pathogenic to plants (Pratylenchus). The effect of 6-year old shelterbelt on nematode community in maize crop field was observed in the field part closes to the shelterbelt.

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Community structure of soil-litter macrofauna in shelterbelt and adjacent crop field

Olechowicz E.

Polish Journal of Ecology

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2004

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Vol. 52, nr 2

135-153

EN

Studies were carried out in 1999 and 2000 in the vicinity of Turew near Poznań (West Poland) and dealt with the composition, density and biomass of soil-litter macrofauna with special reference to dipteran larvae in the agricultural landscape. Sites were located on a 7-years old mid-field shelterbelt and on adjacent field with maize crop in the first and wheatcrop in the second year of study and - on 9 various patches of vegetation within the mid-field shelterbelt. Studies carried out along the transect: the shelterbelt (S) - ecotone (E) - field 10 m (F 10) - field 50 m (F 50) demonstrated a decline of: 1) animal density (10 times) and biomass (30 times) of total macrofauna and (80 times) of dipteran larvae, 2) taxonomic richness and biodiversity measured with the H` index, 3) individual weight of the entire macrofauna, of dipteran larvae,saprophagous animals and predators so that the individuals became smaller with the distance from the shelterbelt, 4) similarity of macrofauna communities in terms of composition and dominance structure, with increasing distance between plots. Close relationship was found between plant cover and soil-litter macrofauna. Species composition, density, biomass and trophic structure of soil invertebrate community depended on tree or herb species. Those soil animals and especially dipteran larvae were a sensitive indicator of small-scale habitat changes.