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51.
Hydrological cycle and interannual variability of the aquatic community in a temporary saline lake (Fuente de Piedra,Southern Spain) 总被引:4,自引:2,他引:2
García Carlos M. García-Ruiz Roberto Rendón Manuel Niell F. Xavier Lucena Juan 《Hydrobiologia》1997,345(2-3):131-141
Fuente de Piedra is a shallow, temporary saline lake whoseseasonal behavior is strongly dependent on the annual hydrologicalbudget. In this study, we outline the characteristics of Fuente dePiedra Lake for two years that had different hydrological budgets.The high precipitations in 1989–90 caused the lake not to dry asusual, and decreased both salinity and the amplitude of changes.There were also differences in nutrient dynamics, with generallylower concentrations of soluble reactive phosphorus and ammonium,whereas in the more humid year nitrate showed a distinct maximum inwinter. Winter bloom chlorophyll a concentrations were alsomuch higher in 1989–90 (>600 g l-1) but there wasalso a winter productive phase that was presumably poorly coupledwith consumption processes that predominate in spring. Planktonicassemblages were different between years. Highly halotolerantphytoplankton species (Dunaliella salina and D. viridis) became scarcer, and especially two previouslyunrecorded diatoms (Cyclotella sp. and Chaetoceros sp.)became dominant in the bloom time in the wet year. The speciesrichness of the zooplankton increased in the wet year, with newspecies appearing that were not collected during 1987–88(Branchinectella media, Daphnia mediterranea, Macrothrix sp.,Arctodiaptomus salinus, Cyclops sp., Sigara sp...).There was also a much higher development of macrophytes (Ruppiadrepanensis, Althenia orientalis, Lamprothamnium papulosum)and bird populations, especially flamingoes (Phoenicopterusruber).Important interannual variations in this sort of system pointto the need for long term studies to observe the whole range ofstates that define the lake as an entity. 相似文献
52.
Karl E. Havens 《Hydrobiologia》1991,215(1):21-29
The limnetic and littoral zooplankton were studied during summer 1989 in Triangle Lake, a humic acid (pH 4.9) bog lake in Ohio, USA. The limnetic zooplankton showed low species richness and biomass, and dominance by the rotifers Kellicottia bostoniensis and Polyarthra vulgaris. In the littoral, species richness and biomass were markedly higher, and the crustaceans Alona guttata, Ceriodaphnia quadrangula, Chydorus sphaericus, Simocephalus serrulatus and Tropocyclops prasinus, and the rotifer Ascomorpha ecaudis were the dominants. The extreme rotifer dominance and lack of cladocerans in the limnetic zone were likely the result of Chaoborus predation. A pronounced mid-summer decline in cladoceran biomass in the littoral was likely due to predation by T. prasinus and Utricularia (bladderwort). 相似文献
53.
D. S. Gillieson 《Hydrobiologia》1991,214(1):327-331
The Larsemann Hills are a series of rocky peninsulas and islands in Prydz Bay at 69° 24 S and 76° 20 E. There is about 2000 km2 of ice free land with well over 150 freshwater lakes spread evenly over the granite and gneiss hills. The nearshore islands were ice free by 9500 BP, while the present coastline was exposed by 4500 BP. A relatively steady rate of ice retreat is indicated, around 0.3 ma–1. The two freshwater lakes studied so far have evolved from oligotrophic, proglacial lagoons to fresh or brackish lakes affected by periodic influxes of salt water from sea spray and surges produced by glacial calving. The diatom assemblages increase in species diversity following marine incursion or influence. The major changes are therefore due to the postglacial recovery of sea level, rather than any intrinsic chemical evolution of the lake waters. 相似文献
54.
Bosherston Lakes are a series of interconnected, mesotrophic to hypereutrophic, artificially-created coastal marl lakes in Dyfed, South West Wales. Progressive eutrophication of the lake system has been produced by a high external phosphorus loading which includes phosphorus-rich effluent from a sewage treatment works (STW) in the catchment of the Lakes.Cores were taken from four sites of varying eutrophic status within the Lakes. In the surface sediment layer, organic C, N and P concentrations generally correlate directly with trophic status and reflect distance from the source of P input. At one site, sediment stratigraphy records a clear transition at 20–15 cm depth, marked by a sharp upward increase in porosity, organic C, N, and P, and iron-associated-P; decreases in organic matter C/N, C/P and N/P ratios; a sharp decrease in carbonate, and a change in the subfossil diatom assemblage. Lead-210 dating indicates that this change occurred in the period 1919 to 1938.The diatom stratigraphy and sediment geochemistry suggest that this transition reflects an increase in trophic status at this site, probably as a result of the influx of nutrient-rich water. This took place when the management of the Stackpole estate surrounding the lake system, fell into decline during the period 1919–1938. 相似文献
55.
Nutrient enrichment experiments in three central Florida lakes of different trophic states 总被引:1,自引:1,他引:0
Seasonal nutrient enrichment experiments (short-term bioassays) were conducted in three Florida lakes of different trophic
states to determine the effects of addition of various nutrient combinations upon chlorophyll a and phytoplankton standing crops. Nutrient enriched surface water samples with crustacean zooplankton removed were incubated
in situ in clear polyethylene bags for 3 to 6 days. The 25 factorial design employed two levels (ambient and enriched) of each of five nutrients [NH4
+, PO
inf4
sup3−
, Fe− -EDTA, SiO
inf3
sup2−
and a cation (Ca2+ or K+) or trace elements]. Ammonium produced significant increases in chlorophyll a and phytoplankton standing crops in all experiments. Phosphate produced similar results in the mesotrophic lake, but the
eutrophic lakes had both positive and nonsignificant responses which varied seasonally between lakes. Iron increased chlorophyll
a in most experiments but affected total phytoplankton standing crop only during the summer and fall. Silicon had negative
effects in some experiments. Cations and trace elements produced marked differences between lakes for chlorophyll a, but total phytoplankton standing crop showed few significant responses. Synergistic responses to two- and three-factor interactions
were observed in all lakes. Differences in the responses of phytoplankton taxonomic divisions to enrichment may be responsible
for much of the between lake variation in chlorophyll a and total phytoplankton volume responses. Nutrient limitations in these lakes are discussed and related to limnological factors
and predictive models. 相似文献
56.
Inland salt waters of southern Africa 总被引:5,自引:5,他引:0
Inland salt lakes are widely distributed in southern Africa: they are particularly common in South Africa, but many occur
in Namibia and Botswana. All are shallow, and most are ephemeral with salinities that are not very high (mostly < 50 g l−1). Fringing zones of halophytes or submerged macrophytes are neither well-developed nor taxonomically diverse. The Cyanobacteria,
especially Nodularia spumigena, often dominate the phytoplankton. The fauna of the Makgadikgadi area (northeast Botswana) is diverse and is similar to that
of East African salt lakes. The aquatic fauna of salt water south of the Makgadikgadi Basin, on the other hand, is extremely
depauperate, has no well-defined assemblage confined to saline waters, and appears mostly to comprise tolerant freshwater
forms. Lovenula falcifera and Metadiaptomus transvaalensis (diaptomid copepods), Moina micrura (Cladocera) and Brachionus plicatilis (Rotifera) are frequently encountered zooplankton species, a few species of insects (Anisops sp., beetles, chironomids and ephydrids) are the principal non-planktonic macroinvertebrates. Artemia ‘salina’ is occasionally present, but may be an introduced form. The avifauna, in contrast to the aquatic macroinvertebrate fauna,
is rich, with the greater and lesser flamingo often common. 相似文献
57.
Bledius (Elbidus) bicornis (Germ.) and B. (Eucerotobledius) furcatus (Oliv.) (Coleoptera: Staphylinidae) are the most important burrowing species in the emergent areas and shores in the athalassic
lake of Fuente de Piedra (Málaga, S. of Spain).
A first estimate of the importance of these organisms in this system is presented. These insects kick out sediment during
their burrowing activity, which accumulates on the surface near the burrows as tumuli which can be easily eroded. The lake
perimeter (17 km) is densely colonized (usual densities from 1700 to 2500 ind m−2). The amount of granulated material that can be potentially kicked out was 46.22 g dry wt m−2 day−1. At the same time, the material that constitutes the tumuli shows different characteristics from the compact ground below
the surface. Thus, it is relatively enriched with organic matter (6.15 g per square meter), soluble phosphate (406.5 μg m−2) and ammonium (4856 μg m−2), whereas it lacks nitrate. Results of a transect from uninhabited areas to zones of maximum population density also show
a similarity between the higher ground level of ammonium and phosphate concentrations and population density. 相似文献
58.
Wolfgang Hofmann 《Hydrobiologia》1991,214(1):207-211
Sediments from maar lakes in the periglacial area were analysed to obtain information about the limnetic fauna of Pleniglacial lakes. On the basis of abundance and species composition of the subfossil chironomid and cladoceran assemblages, three major zones were biostratigraphically separated: the Upper Pleniglacial, the Middle Pleniglacial, and the Eem Interglacial. 相似文献
59.
The chemistry and crustacean zooplankton of the Seewinkel pans: a review of recent conditions 总被引:2,自引:1,他引:1
A number of shallow pans was investigated between May 1982 and May 1985 in the Seewinkel region between Neusiedlersee and
the Hungarian border. Chemical and zooplankton samples were obtained at three monthly intervals. Analyses indicated some changes
during the past decades. Human activity has resulted in some changes to water chemistry and zooplankton composition in a few
pans, and many smaller pans have now disappeared. 相似文献
60.
Blom Gerard Van Duin Elisabeth H. S. Aalderink R. Hans Lijklema Lambertus Toet Christian 《Hydrobiologia》1992,(1):153-166
In shallow, wind exposed lakes, the light conditions, the cycling of nutrients, heavy metals and organic micro-pollutants and changes in the local composition of the sediment top layer can be dominated by resuspension/erosion of bottom sediment and sedimentation of suspended solids. A 2 dimensional model for Sediment Transport, Resuspension and Sedimentation in Shallow lakes (STRESS-2d), based on an existing transport model, is discussed. In the model, mass balance equations for the water compartment and the bottom sediment are solved numerically. Up to 7 sediment fractions can be taken into account, each having a specific set of resuspension/erosion and sedimentation parameter values. Several options for modelling the changes in the bottom sediment composition are available.A simulation experiment for Lake Veluwe (The Netherlands), in which model options with and without the distinction of sediment fractions were used, showed that using sediment fractions to account for the variability in the sediment composition leads to an improvement of the model results, particularly the simulated phosphorus sediment-water exchange fluxes. For Lake Ketel (The Netherlands) two options for modelling changes in the bottom sediment composition are compared. It is shown that an option in which a thin water-sediment layer on top of the more consolidated bottom sediment is simulated provides an improvement in the simulation of the suspended solids concentration. 相似文献