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1.
During the period 1981–1990 the functioning of microphytobenthos in the carbon cycle was studied in the Oosterschelde, a mesotidal, euhaline estuary (SW Netherlands), both before and after completion of a storm-surge barrier in the sea ward entrance of the estuary in 1986, which reduced the tidal range to 88% and current velocities to 70% of their former values on average.The annual biomass cycle has changed from small spring and autumn peaks into a much larger summer peak. The average biomass during summer has increased from 70 to 170 mg Chlorophyll-a m2. The average annual biomass has increased from 115 to 195 mg Chlorophyll-a m2. As a consequence the (calculated) primary production by microphytobenthos has increased also, from 150 to 242 gC m–2 y–1 (14 045 to 22 265 tonnes C y–1), and its share in the total primary production of the Oosterschelde has increased from 16 to 30%. These increases in biomass and primary production are mainly ascribed to a decrease in the dynamic forces (water current velocities) over the intertidal flats in most parts of the basin. Increased water transparency in parts of the estuary and increased import of inorganic carbon from the water column towards shoals may have contributed as well.The rate of reworking of the top layer of the soil (0–10 cm) has not changed significantly, as the decrease in Chlorophyll-a biomass with depth has hardly changed. 相似文献
2.
Einar Kärgenberg Finn Økland Mart Thalfeldt Eva B. Thorstad Odd Terje Sandlund Meelis Tambets 《Journal of fish biology》2020,97(4):996-1008
Potamodromous fishes require safe migration routes between spawning, feeding and wintering habitats to complete their life cycle. As knowledge on asp migrations is restricted, this work investigated the movements of adult asp tagged with acoustic transmitters for 3 years in the large Peipsi-Emajõgi-Võrtsjärv lake–river system, Estonia, which is free of migration barriers. Asp showed complex migration patterns, moving between and within different waterbodies (lakes, river, tributaries) in all seasons, but with a tendency to repeat habitat use patterns between years. Lakes were mainly used for feeding during spring and summer (after spawning 65% of the fish migrated to Lake Peipsi), and more so by large fish. The majority (80–96%) of the fish spent the winter in the rivers, mostly close to their subsequent spawning area. Spawning areas were in swift-flowing waters in tributaries and the main river. The results indicate that asp may benefit from an extensive and diverse complex of habitats, and any migration barrier during any season may restrict the natural habitat use by asp. Maintenance and restoration of habitat heterogeneity and connectivity is critical to protect behaviourally diverse fish populations and increase resilience in rivers negatively impacted by various human activities. 相似文献
3.
Zooplankton in the River Rhine was surveyed for five years at the Dutch sampling stations, Lobith (German/Dutch border) and
Maassluis (at the point of discharge of the river into the North Sea). The zooplankton abundance showed an apparent seasonal
pattern at both stations, characterized by low densities during the winter period, and higher densities during the summer
period, with a spring peak. Zooplankton was dominated by rotifers at both stations, although during the winter periods the
contribution of copepods was considerable. The rotifers were dominated byBrachionus angularis, B. calyciflorus, Keratella cochlearis andK. quadrata; the copepods by cyclopoid nauplii; the cladocerans by small-sized species mainly belonging toBosmina. At Maassluis the relative contribution of copepods was higher than at Lobith. Furthermore, the zooplankton at Maassluis
included the speciesEurytemora affinis, characteristic for estuarine conditions. In spring, the rotifer density and water temperature and rotifer density and chlorophylla concentration were positively correlated. Furthermore, both rotifer density and chlorophylla were inversely correlated with discharge. The possible role of environmental factors (water temperature, chlorophyll content,
discharge and biotic factors) controlling the river zooplankton dynamics is indicated. 相似文献
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The composition and distribution of the macroinvertebrate fauna of the shallow part of De Gijster, a medium sized water storage lake in The Netherlands, has been studied during 1984. The numerous individuals collected belong mainly to the Oligochaeta, Diptera (Chironomidae larvae) and Mollusca. Amongst them are elements of both the former polder fauna and the river fauna. A quantitative analysis revealed data on the horizontal distribution of several taxa within the lake as well as data on the influence of the lifecycle of some taxa on the annual composition of the fauna. 相似文献
6.
Nhlabane coastal lake and estuary system in South Africa is divided by a permanent barrage constructed at the outlet of the
lake. This study compared the zooplankton assemblages of the lake and estuary systems after 15 years of separation. Before
sampling commenced the mouth of the estuary closed and remained so throughout the duration of the study. The lake was completely
fresh and the estuary had a low salinity not exceeding 4‰. Both the estuary and lake are shallow systems (less than 2 m) and
were well mixed. Turbidity levels were generally below 10 NTUs. Temperature fluctuated seasonally between 18.5 and 30°C. Oxygen
levels ranged between 4.3 and 9.9 mg/l but were mostly above 5 mg/l for both systems. The estuarine and lake plankton was
dominated by copepod instars, especially of the calanoid Pseudodiaptomus hessei. During the entire study period the lake also
supported high densities of rotifers. Rotifers only appeared in the estuarine plankton at the end of the sampling period.
During the first sampling sessions zooplankton diversity in the estuary was higher but declined thereafter to levels within
the range calculated for the lake. Estuarine relict species recorded reflect the estuarine history of the lake. Multivariate
analyses indicated a change in the composition of the zooplankton community in the estuary during the duration of the study,
while that of the lake remained comparatively stable. Species composition analyses showed that this change in the estuary
was due to a shift from an estuarine to a more freshwater zooplankton assemblage. During this change some estuarine species
declined in abundance or were not recorded anymore. These changes in the zooplankton community of the estuary may well illustrate
the changes that occurred in the lower (south) section of the lake after completion of the barrage which isolated it from
the estuary.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
S. Parma 《Hydrobiologia》1982,95(1):1-9
This paper marks the silver jubilee in 1982 of the Limnological Institute, The Netherlands. It describes the history, present research programme and organisation of the Institute, as well as its cooperative studies with other institutes and its training facilities.Some remarks about its future plans of work are made. 相似文献
8.
E. B. Fefilova O. N. Kononova O. P. Dubovskaya L. G. Khokhlova 《Inland Water Biology》2012,5(4):333-341
The current state of zooplankton in the large lake system of Bol??shezemel??skaya tundra was determined in comparison with data from the 1960s. It was found that the annual dynamics of plankton communities took place, but their composition and structure were saved. However, some current features of tundra-lake zooplankton can be indicative of the directed development of ecosystems and the start of their eutrophication. These processes take place against the background of the attenuation of the anthropogenic impact on water bodies and certain trends in climate change. The studied lakes were oligo- and mesotrophic. 相似文献
9.
L. P. M. J. Wetsteyn J. C. H. Peeters R. N. M. Duin F. Vegter P. R. M. de Visscher 《Hydrobiologia》1990,195(1):163-177
Phytoplankton primary production, nutrient concentrations and turbidity were monitored at three stations in the Oosterschelde during 1980–1984 as part of an ecosystem study.From comparisons of dissolved nutrient ratios with the nutrient requirements of phytoplankton, and of ambient nutrient concentrations with half-saturation constants for nutrient uptake by natural phytoplankton populations it was concluded that silicate was a limiting nutrient for diatoms after the spring bloom until the end of the summer. Dissolved inorganic nitrogen and phosphate were not considered to be limiting to phytoplankton growth.In general, the phytoplankton growing season started during the first fortnight of April and ended at the end of September. Column production in the whole Oosterschelde varied between 201 and 540 g C m–2 yr–1 and was, on average, 25% higher in the western part than in the eastern part. Basin production in the Oosterschelde varied between 120 and 466 g C m–2 yr–1 and was, on average, 55% higher in the western part than in the eastern part; this difference could be explained by differences in the ratio of euphotic depth to mean depth of the compartments.Estimated carbon-specific growth rates in the eastern part varied between < 0.1 and 3 d–1 and in the western part between < 0.1 and 1 d–1. This difference could be explained by the great differences in depth of the compartments. Carbon-specific growth rates are discussed in relation to phytoplankton loss rates. It is suggested that in the eastern part sedimentation must be an important sink for phytoplankton.Communication no. 473 of the Delta Institute for Hydrobiological Research, Yerseke, The Netherlands. 相似文献
10.
《Trends in molecular medicine》2023,29(8):599-621
Ubiquitin–proteasome system (UPS) is a selective proteolytic system that is associated with the expression or function of target proteins and participates in various physiological and pathological processes of breast cancer. Inhibitors targeting the 26S proteasome in combination with other drugs have shown promising therapeutic effects in the clinical treatment of breast cancer. Moreover, several inhibitors/stimulators targeting other UPS components are also effective in preclinical studies, but have not yet been applied in the clinical treatment of breast cancer. Therefore, it is vital to comprehensively understand the functions of ubiquitination in breast cancer and to identify potential tumor promoters or tumor suppressors among UPS family members, with the aim of developing more effective and specific inhibitors/stimulators targeting specific components of this system. 相似文献
11.
László G.-Tóth Sandra Poikane W. Ellis Penning Gary Free Helle Mäemets Agnieszka Kolada Jenica Hanganu 《Aquatic Ecology》2008,42(2):265-275
The Water Framework Directive (WFD 2000) defines macrophytes as one of the biological groups required for the ecological assessment of European surface waters. Several
indices for macrophyte assessment have been proposed or are currently in use by different European states. As a first step
towards performing an intercalibration of these indices a common dataset was developed. This dataset contains abundance data
on 789 macrophyte species from 316 different lake sites in ten European countries. Various common species and genera were
identified as indicators of reference and impacted conditions within the dataset. Cluster analysis of macrophyte data, supported
by non-metric multidimensional scaling, indicated that clusters formed were more reflective of their source country rather
than lake type. This might be caused by differences in regional climate, biogeography, monitoring techniques, or a combination
of these factors. A total of six national indices were applied to assign quality classes to the lakes. However, this produced
results that often differed by one or two quality classes for the same site. We foresee that a more precise intercalibration
exercise is necessary, and it should be based on more detailed data considering both seasonality and the latitudinal differences
within the area covered. 相似文献
12.
Pearson James Dunham Jason Ryan Bellmore J. Lyons Don 《Wetlands Ecology and Management》2019,27(5-6):663-682
Wetlands Ecology and Management - The introduction of Common Carp (Cyprinus carpio) into North American waterways has led to widespread alteration of aquatic ecosystems. Control of this invader has... 相似文献
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There is an autonomous renin–angiotensin system (RAS) in the adult ovary. Renin is present in the primitive kidney, and the fetal ovary develops from the nephrogenic ridge. We hypothesised that components of the ovarian RAS would be present from early gestation, with potential roles in ovarian development. We studied fetal pig ovaries from approximately day 45 (~0.39 gestation) to term and measured mRNA (RT-PCR) for prorenin, angiotensinogen and the angiotensin II (AngII) Type 1 and 2 receptors (AT1 and AT2), and protein expression (Western blot) and localization (immunohistochemistry) of the AT1 and AT2 receptors. mRNA for prorenin was present in relatively low abundance from at least day 45 and rose to ~day 75 of gestation, whilst mRNA for angiotensinogen rose steadily. mRNA for the AT1 receptor was present from approximately day 45 and did not alter significantly with increasing gestation but AT2 receptor mRNA was initially high, falling sharply through pregnancy. The AT1 receptor protein abundance fell steadily to term, whereas the AT2 receptor protein did not change during gestation. Both receptors were localised in the surface epithelium and egg nests, the granulosa cells of primordial, primary and secondary follicles, and the oocytes of all except the secondary follicles. Collectively, our results support the hypothesis that there is a functional RAS in the fetal ovary from at least approximately day 45 of gestation until term and that it may have a paracrine role in ovarian growth and development. 相似文献
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The human impact in the German Bight, in the form of anthropogenic eutrophication, has been documented by a 30-year time-series
measurement near the island of Helgoland. Since 1962, the Biologische Anstalt Helgoland has measured inorganic nutrients and
phytoplankton abundance from daily samples at Helgoland Roads, a position 60 km off the main source of eutrophication, the
River Elbe. Since the early sixties, phosphate concentrations rose for about a decade, levelling off to about twice the former
concentrations for another decade, and then decreasing (since 1982) as a result of phosphate-reducing measures. Nitrate concentrations,
however, have only increased since 1980/81, following Elbe river flood events. In 1987, three times the former concentrations
were reached. A decrease has been observed only since 1991. This different development of phosphorus and nitrogen eutrophication
led to a shift of inorganic N/P-ratios in the German Bight. The phosphate increase was more pronounced in the late summer
“regeneration mode” conditions, the nitrate increase in the winter months. The eutrophication is not restricted to the inner
German Bight and coastal waters of a salinity of <33, but has also occurred in more saline waters at S>33 psu (practical salinity
unit), as characteristic for the outer German Bight. In this more saline water, phosphate and nitrate maximum levels occurred
three years later, compared with the average Helgoland data, which are more representative of the inner German Bight. It is
suggested that suspended particulate organic matter, as a long-distance carrier of nutrients, might have caused this delayed
eutrophication in the outer German Bight waters. While the human impact is obvious as to nutrient concentrations, it is less
obvious in phytoplankton stock enhancement. A general increase in phytoplankton biomass (about 3–4 times) was found, but this
was mainly due to unidentified nanoflagellates of unknown trophic state, and subject to methodological errors. The causal
relationships of phytoplankton stocks and eutrophication are not clearly understood, as natural variability is large and hydrographical
factors possibly dominate. Additional nutrient input by Elbe river floods did not always result in elevated phytoplankton
stocks near Helgoland, while extended periods of vertical density stratification of the German Bight water caused large plankton
blooms. 相似文献
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Marta Recio Baltasar Cabezudo María del Mar Trigo Francisco Javier Toro 《Aerobiologia》1998,14(2-3):101-107
A pollen calendar has been constructed for Malaga (Southern Spain) based on the data obtained during 5 years (1991–95) using
a Burkard spore trap set up approximately 1 km west of the city. The calendar only reflects taxa which showed a 10-day mean
pollen concentration equal to or greater than 1 grain of pollen/m3 of air. Twenty nine taxa are included, of which the three commonest (Olea europaea, Cupressaceae andQuercus) represent approximately 54% of the total annual count and the following four (Chenopodiaceae-Amaranthaceae, Gramineae, Urticaceae
andPlantago) represent 21.3%. The greatest diversity of pollen types occurs during Spring and the highest concentrations from February
to June, when approximately 85% of the total annual pollen is registered. Several peaks occur during the year principally
due to Cupressaceae in February,Quercus in April,Olea europaea in May andCasuarina in October, although substantial quantities of Urticaceae, Chenopodiaceae-Amaranthaceae,Plantago and Gramineae are also detected in April and May. The pollination of important allergy-producing taxa such as olive and grass
takes place earlier in Malaga than in cities more inland, so that the data presented here may be useful in predicting the
beginning of the pollination season of these localities. 相似文献