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1.
Fossil diatom assemblages preserved within the sedimentary record in Arctic lakes provide the potential to reconstruct past
changes in important limnological variables. During the summers of 1992 and 1993, we examined previously unstudied freshwater
ecosystems on Cornwallis Island, Arctic Canada, with the specific objectives of (1) documenting the limnology and modern diatom
assemblages from this region, and (2) determining which environmental variables most influence diatom species distributions.
The Cornwallis Island study sites displayed the least amount of variance in measured water chemistry variables in comparison
to nearly all of our labs’ previous freshwater surveys in the Arctic. The small limnological gradients precluded the development
of a statistically robust diatom inference model, but perhaps more importantly, allowed us to explore variations in diatom
composition in the absence of marked variations in water chemistry. Diatom species turnover was minimal, with the most common
diatom taxa being Achnanthidium minutissima, Nitzschia perminuta, N. frustulum, with lesser percent abundances of Chaemaepinnularia soehrensis, Navicula chiarae, Psammothidium marginulata, and A. kryophila. A small number of study sites differed from the majority with respect to water chemistry (e.g., coastal sites with high
specific conductivities) and habitat availability (e.g., ephemeral ponds with extensive moss habitats), and these sites had
markedly different diatom assemblages. These data reinforce previous observations that water chemistry and other climate-related
factors are the primary environmental controls influencing diatom distributions at high latitudes.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
2.
Gengo Tanaka 《Hydrobiologia》2008,598(1):271-284
One hundred and sixty-seven species of podocopid ostracods are reported from 26 recent surface sediment samples collected
on the shelf of the Tsushima Strait in the southwestern Sea of Japan. Four biofacies (A–D) are recognised based on Q-mode
cluster analysis. Among these, biofacies B is distributed along the Tsushima Warm Current and includes typical East China
Sea species. This fact suggests that the migration of the shelf-living ostracods between the open sea and the adjacent semi-enclosed
marginal sea mainly occurs in association with the inflow of this sea current. The distribution of the recent ostracod assemblages
from the Tsushima Strait are expected to be a sensitive indicator of past and future changes in the Tsushima Warm Current.
One new ostracod species of the family Trachyleberididae, Trachyleberis ikeyai, is described and illustrated herein.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Handling editor: K. Martens 相似文献
3.
The spatial and temporal distributions of the epiphytic diatom flora on Thalassia testudinum was described within the Florida Bay estuary and at one Atlantic site east of the Florida Keys over a 1-year period. Species
of the genus Mastogloia dominated the epiphytic diatom flora (82 out of 332 total species). Nonmetric Multidimensional Scaling (NMDS) and Analysis
of Similarity (ANOSIM) revealed four distinct spatial assemblages and two temporal assemblages. Eastern and western Florida
Bay assemblages were identified within the estuary. The eastern diatom assemblage was characterized by high relative abundances
of Brachysira aponina and Nitzschia liebetruthii, while the western assemblage was characterized by the abundance of Reimerothrix floridensis, particularly during summer. Two diverse and distinct marine assemblages, one located in the Gulf of Mexico along the western
edge of Florida Bay and the other behind the Florida reef tract in the Atlantic Ocean, were also identified. Analysis of the
spatial distribution of diatoms and water quality characteristics within Florida Bay suggest that these assemblages may be
structured by salinity and nutrient availability, particularly P. The Gulf of Mexico and the western Florida Bay assemblages
were associated with higher water column salinities and TP concentrations and lower DIN concentrations and TN:TP ratios relative
to the eastern Florida Bay assemblage. The temporal variation in diatom assemblages was associated with water temperature,
though temporal indicator species were few relative to the number of spatial indicators.
Electronic supplementary material Electronic supplementary material is available for this article at
and accessible for authorised users. 相似文献
4.
Development of diatom-based tools for assessing stream water quality in south-eastern Australia: assessment of environmental transfer functions 总被引:1,自引:0,他引:1
Models were developed of relationships among water quality, geospatial and species-level diatom data for 465 samples collected
from stream sites across south-eastern Australia. Transfer functions were derived from weighted averaging and artificial neural
network approaches. Analysis of spatial variations in species assemblages was used to divide the sites into two groups according
to site elevation. The strongest predictive models for the upland group associated diatom assemblages with conductivity, longitude,
altitude, and to a lesser extent pH, NO
x
and TKN. The strongest predictors for the lowland group were longitude and conductivity, but artificial neural network models
performed well for NO
x
and temperature. The importance of the geospatial variables suggests that there may be a capacity to develop diatom sub-regions
within which robust models for other water quality variables important to management can be generated.
Electronic supplementary material Electronic supplementary material is available for this article at
and accessible for authorised users.
Handling editor: R. Norriss 相似文献
5.
Increasing degradation of the water quality, caused by overuse and salinization, leads to considerable changes of the phytoplankton
composition in Kenyan Rift Valley lakes. Exemplarily, the phytoplankton communities and biomasses of deteriorating freshwater
Lake Naivasha and salinizing Lake Oloidien were studied between 2001 and 2005, accompanied by physico-chemical measurements
(pH, total phosphorus and nitrogen, alkalinity, conductivity). Over the last three decades, the ecology of these two water
basins has been subjected to dramatic changes, caused by excessive use of water and catchment area by man. In L. Naivasha
a shift in the dominance of coccoid cyanobacteria towards dominance of Chlorophyceae (Botryococcus terribilis) was observed. Lake Oloidien exhibited a shift in the dominance of coccoid Chlorophyceae towards dominance of cyanobacteria
(Arthrospira fusiformis, Anabaenopsis elenkinii). Phytoplankton findings and chemical data demonstrate that L. Naivasha has developed towards a eutrophic freshwater lake
while L. Oloidien has progressed towards a hypereutrophic alkaline-saline lake.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Handling editor: J. Padisak 相似文献
6.
Late Quaternary palaeohydrology of Lake Huinaymarca (Bolivia) 总被引:1,自引:0,他引:1
Ph. Mourguiart P. Carbonel J. -P. Peypouquet D. Wirrmann C. Vargas 《Hydrobiologia》1986,143(1):191-197
In lake Titicaca, the distribution of the modern ostracod fauna appears to be controlled by a combination of two factors: a) the equilibrium between carbonates and organic matter, b) the ionic composition of the lake water and its tributaries. Therefore, the Limnocythere-Pampacythere group generally predominates on an alkaline-carbonate lake floor. In parts of the lake receiving an NaCl input from tributaries, Cyprideis and Cyprinotus occur. These are generally absent elsewhere. The Candonopsis group is found in the deepest part of the lake.Analysis of ostracod assemblages recovered from a number of cores permitted the reconstruction of the hydrological evolution of lake Huinaymarca for the last 10000 years. This included: low water levels, variations of oxygenation related to the position of the thermocline, and interconnections between different basins of the lake. 相似文献
7.
Jutta Günther 《Hydrobiologia》1986,143(1):411-416
About 4000 ostracod valves have been analysed from a sediment core of a cultivated bog NW of Hamburg. The deepest deposits are sands free of subfossils, the uppermost layers consist of peat. In the sediment in between, there are three layers containing undestroyed valves. The ostracod assemblies of the older claygyttja (Late-glacial) and the two younger, fine detritus deposits (Post-glacial) are strikingly different.
Cytherissa lacustris, Candona neglecta, Ilyocypris bradyi, Herpetocyrpis reptans, and two Limnocythere species were found in the Late-glacial layers. Changes in abundance of these species indicate alterations in climate, lake ground, water inflow and waterlevels. Postglacial layers are rich in Metacypris cordata valves associated with numerous Candona species, L. inopinata, Darwinula stevensi, and Cyclocypris laevis. These species are characteristic of a small lake with a large littoral zone. A similar development in ostracod assemblages is found in middle Europe by Absolon (1973), although the main Candona species is not C. neglecta but C. candida. Ostracod analysis cannot demonstrate an influence of anthropogenic impacts on ostracod successions. 相似文献
8.
Chris Gouramanis Patrick De Deckker 《Palaeogeography, Palaeoclimatology, Palaeoecology》2010,297(1):223-237
A 4 m long core taken from the freshwater Blue Lake crater near the township of Mount Gambier in southeastern South Australia provided a high-resolution palaeoclimatic record for the last six millennia. Accelerator Mass Spectrometry (AMS) radiocarbon (14C) dates were obtained from organic plant fibres and biogenic carbonates from the laminated sequence of the core and from a modern water sample. Large discrepancies between the radiocarbon ages determined from plant fibres and biogenic carbonates indicate the presence of a time-variable lacustrine reservoir, which is consistent with what is known of the lake's hydrology.Ostracod assemblages, associated with stable isotope (δ13C, δ18O) analyses and, in combination with Mg/Ca, Sr/Ca and Na/Ca analyses done on ostracod valves, infer salinity, temperature and water level changes in Blue Lake over the last 6 millenia. The influence of local aquifers through time has also been determined from the Na/Ca of ostracod valves. Approximately 900 year cycles are evident in the δ13C record from 5.4 ka to 1.8 ka.The history of Blue Lake records an initial period of high hydrological variability around 6 ka, becoming increasingly deeper as groundwater flowed into the basin. By 4 ka, the lake had reached steady state with the lake level fluctuating by as much as 9 m, although significant geochemical variations represent temperature fluctuations until European settlement near the lake in 1839. 相似文献
9.
Seventeen ostracod species were recorded from Lake Gölköy (Bolu, Turkey) between January 2000 and December 2001. Limnocythere inopinata is a new record for the Bolu region. Canonical Correspondence Analysis (CCA) explained 73% of the correlation between species and environmental variables, suggesting that the occurrence of many species is temporally variable, and is related to seasonal changes in physico-chemical conditions. The four most frequently occurring cosmopolitan ostracod species (Candona neglecta, Darwinula stevensoni, Physocypria kraepelini, and Cypridopsis vidua) accounted for more than 70% of the species recorded. Water temperature, dissolved oxygen (DO), and redox potential were the most affective variables on the species occurrence. Two species (C. vidua, I. bradyi) were positively correlated to redox potential, while such a correlation was negative for P. kraepelini. The most frequently occurring species C. neglecta was most closely related to the changes in redox potential, whereas C. vidua and D. stevensoni showed a positive correlation to water temperature. Negative strong correlation (p<0.01) was found between pH and I. bradyi, but correlation was positive and weak for C. vidua. Some species (e.g. L. inopinata) showed no clear relationship with any of those environmental variables. UPGMA clustering of species based on their occurrence in different ecological conditions revealed three main species assemblages. Analysis of species phenology using the ‘Ostracod Watch Model’ showed that temporal patterns of occurrence could be similar among species with similar ecological preferences. The current status of the lake is
discussed based on the present study. 相似文献
10.
Agnieszka Szlauer‐ukaszewska 《International Review of Hydrobiology》2012,97(4):262-275
The aims of this study included: specifying values of ecological parameters and Ostracoda species characteristic for different types of plant habitats occurring in lake systems, determining the impact of mud presence on the taxonomic structure and density of the ostracods, tracing seasonal changes in the structures of Ostracoda assemblages identifying the species typical of particular seasons. Various types of rushes and underwater meadows were taken into consideration as lake microhabitats. The research was conducted in the shallow Lake Œwidwie (NW Poland). Multivariate (constrained) ordination methods were used to analyse the relationships between species composition and environmental variables. In the lake and its margins 31 species of the Ostracoda were identified. The development of water vegetation during the vegetation season was conducive to growth in ostracod density. The accessibility of mud in plant habitats had a favourable effect on the general density of ostracods. Species which preferred a high mud content in their habitats included: Cypria ophtalmica, C. exsculpta and Physocypria kraepelini. Species typically encountered in underwater meadow habitats were: Cyclocypris ovum and Cypridopsis vidua. Underwater meadows of charophyte were characterized by the highest ostracod density in the whole lake system, with the average of 7860 ind. m–2 and the maximum of 17 470 ind. m–2. Species typically encountered in rush habitats included Notodromas monacha, Dolerocypris fasciata and Metacypris cordata. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
11.
Diatom analysis of surface sediments and two sediment cores from different sedimentation areas of a small closed lake was
undertaken with the aim of acquiring knowledge on the dependence of the distribution of diatom assemblages on lake bathymetry.
Lake Juusa was selected for the study because we have for this lake a large data set about the lithological composition of
sediments and macrofossil and cladoceran records for the Holocene. A high carbonate content (20–60%) in the sediment sequence
indicates high carbonacity and relatively stable pH values during the Holocene. On the basis of comprehensive analysis, abrupt
water-level fluctuations and changes in the trophic status were established. Results of this study showed that the fluctuations
of the water-level were the leading factor determining the habitats of diatom assemblages in the lake. In the surface sediment
samples planktonic species such as Cyclotella spp., Stephanodiscus spp. and Aulacoseira spp. had a depth optimum at 3–4 m and the most abundant periphytic taxa were distributed mostly at depths shallower than
3.5 m. The same regularity was established in sediment cores where a good correlation between planktonic species and lake
water depth was found in sediments accumulated at water depths >4 m. Lake Juusa appears to be a proper site for detailed environmental
reconstructions over the Holocene, and the results will give us a good opportunity to analyse the history of water-level fluctuations
in other small Estonian lakes.
Electronic Supplementary Material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Handling editor: K. Martens 相似文献
12.
Non-native aquatic macrophytes have invaded different types of ecosystems all over the world. The exotic submersed macrophyte
Hydrilla verticillata recently invaded the Paraná basin, Brazil, being recorded by the first time in the natural habitats of this river in 2005.
We investigated the effects of this species on ostracod assemblages and compared the abundance, richness, and Shannon–Wiener
diversity of ostracod assemblages that colonize the invading species with those that colonize Egeria najas, a native submersed species with similar architecture and physical complexity. Fragments of these two species were left for
28 days in tanks to root and grow and then they were transferred to a floodplain lake where they remained in pairs (one plant
of each species; N = 7) during 30 days for colonization by ostracods. A detrented correspondence analysis was used to summarize ostracod assemblage
composition. Although there were no significant differences in ostracod abundance, richness and Shannon diversity when analyzed
separately, cumulative curves, which permit to eliminate effects of abundance on richness, indicated a significantly higher
number of ostracod species on H. verticillata. Assemblage composition was significantly different between both plant species, as shown by the first DCA axis. Our results
show that H. verticillata might provide favorable habitats for native ostracod assemblages. 相似文献
13.
Kevin Keatings Jonathan Holmes Roger Flower David Horne John E. Whittaker Ramadan H. Abu-Zied 《Hydrobiologia》2010,654(1):155-176
We present an ostracod record covering the past two millennia from an 8.25-m core taken from Lake Qarun, in the Faiyum Depression of Egypt. The occurrence of ostracod species in the lake is controlled primarily by variations in solute composition, which are in turn related to shifts in catchment land use. At times when the Faiyum Depression supported thriving agriculture, lake water contained Na+–Cl? brine, and Cyprideis torosa dominated the ostracod assemblage. When the Faiyum Depression experienced periods of environmental and economic decline, lake water contained Na+–HCO3 ? brine, and Limnocythere inopinata dominated. The relative abundance of other ostracod species provides additional information about past conditions in Lake Qarun including salinity and lake level changes. Overall, the ostracod assemblages provide evidence for human influences in the Faiyum, which extend back before instrumental or detailed observational records began. 相似文献
14.
We compare lizard assemblages of Cerrado and Amazonian savannas to test the ecological release hypothesis, which predicts
that niche dimensions and abundance should be greater in species inhabiting isolated habitat patches with low species richness
(Amazonian savannas and isolated Cerrado patches) when compared with nonisolated areas in central Cerrado with greater species
richness. We calculated microhabitat and diet niche breadths with data from 14 isolated Cerrado patches and Amazon savanna
areas and six central Cerrado populations. Morphological data were compared using average Euclidean distances, and lizard
abundance was estimated using the number of lizards captured in pitfall traps over an extended time period. We found no evidence
of ecological release with respect to microhabitat use, suggesting that historical factors are better microhabitat predictors
than ecological factors. However, data from individual stomachs indicate that ecological release occurs in these areas for
one species (Tropidurus) but not others (Ameiva ameiva, Anolis, Cnemidophorus, and Micrablepharus), suggesting that evolutionary lineages respond differently to environmental pressures, with tropidurids being more affected
by ecological factors than polychrotids, teiids, and gymnophthalmids. We found no evidence that ecological release occurs
in these areas using morphological data. Based on abundance data, our results indicate that the ecological release (density
compensation) hypothesis is not supported: lizard species are not more abundant in isolated areas than in nonisolated areas.
The ecology of species is highly conservative, varying little from assemblage to assemblage. Nevertheless, increases in niche
breadth for some species indicate that ecological release occurs as well.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
15.
Ostracods are important members of the benthos and littoral communities of lake ecosystems. Ostracods respond to hydrochemistry
(water chemistry) which is influenced by climatic factors such as water balance, temperature, and chemicals in rainfall runoff
from the land. Thus, at local scales, environmental preferences of ostracods and characteristics of lakes are used to infer
changes in climate, hydrology, and erosion of lake catchments. This study addresses potential drivers of ostracod community
structure and biodiversity at multiple spatial scales using NMS, CART?, and multiple regression models. We identified 23 ostracod species from 12 lake sites. Lake area, maximum depth, spring conductivity,
chlorophyll a, pH, dissolved oxygen, sedimentary carbonate, and organic matter all influence ostracod community structure based on our
NMS. Based on regression analysis, lake depth, chlorophyll a, and total dissolved solids best explained ostracod richness and abundance. Land uses are also important community structuring
elements that varied with scale; locally and regionally agriculture, wetlands, and grasslands were important. Nationally,
using regression tree analysis of lakes sites in the North American Non-marine ostracod database (NANODe), row-crop agriculture
was the most important predictor of biodiversity. Low agriculture corresponded to low species richness but greater landscape
heterogeneity produced sites of high ostracod richness. 相似文献
16.
To trace environmental changes in water hydrology and salinity in the Late Glacial to Holocene of the Gulf of Gdańsk, a south‐eastern bay of the Baltic Sea within the maritime zone of Poland, the distribution of ostracod valves was studied in 20 sediment cores collected from both the shallow‐ and deep‐water zones (depth 10.9–67.5 m). The studied sediment sequences yielded ca. 3000 valves of 21 ostracod species, of which only five are known to live today in the Gulf, which has a present maximum depth of 118 m and water salinity up to 7–8‰. The majority of the studied sediment layers that contained ostracod valves corresponded to the period of the Late Glacial to Mid‐Holocene and was dominated by non‐marine species, of which the most common were Candona neglecta (present in 17 cores), Cytherissa lacustris (15 cores) and Candona candida (14 cores). By clustering classification five major ostracod assemblage types were recognised in the studied cores. Initial assemblage types dominated mostly by inhabitants of the profundal/sub‐littoral zones of modern oligo‐mesotrophic lakes (C. lacustris and C. neglecta) in some sediment sequences were replaced in stratigraphical order by the assemblages dominated by brackish‐water species (Cyprideis torosa or Cytheromorpha fuscata). The structure and species composition of the distinguished ostracod assemblage types as well as their successional transitions indicate that the studied sediments were deposited initially in the Late Glacial in freshwater lacustrine conditions, and subsequently, during the Holocene marine transgression, covered by marine sands. The present results confirm and consolidate inferences based on previously published data on ostracods from the western part of the Gulf of Gdańsk as well as on other biotic (molluscs, diatoms) and abiotic (seismoacoustic) indices from this area (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
17.
Gary L. Larson C. David McIntire Mark W. Buktenica Scott F. Girdner Robert E. Truitt 《Hydrobiologia》2007,574(1):217-233
The zooplankton assemblages in Crater Lake exhibited consistency in species richness and general taxonomic composition, but
varied in density and biomass during the period between 1988 and 2000. Collectively, the assemblages included 2 cladoceran
taxa and 10 rotifer taxa (excluding rare taxa). Vertical habitat partitioning of the water column to a depth of 200 m was
observed for most species with similar food habits and/or feeding mechanisms. No congeneric replacement was observed. The
dominant species in the assemblages were variable, switching primarily between periods of dominance of Polyarthra-Keratella cochlearis and Daphnia. The unexpected occurrence and dominance of Asplanchna in 1991 and 1992 resulted in a major change in this typical temporal shift between Polyarthra-K. cochlearis and Daphnia. Following a collapse of the zooplankton biomass in 1993 that was probably caused by predation from Asplanchna, Kellicottia dominated the zooplankton assemblage biomass between 1994 and 1997. The decline in biomass of Kellicottia by 1998 coincided with a dramatic increase in Daphnia biomass. When Daphnia biomass declined by 2000, Keratella biomass increased again. Thus, by 1998 the assemblage returned to the typical shift between Keratella-Polyarthra and Daphnia. Although these observations provided considerable insight about the interannual variability of the zooplankton assemblages
in Crater Lake, little was discovered about mechanisms behind the variability. When abundant, kokanee salmon may have played
an important role in the disappearance of Daphnia in 1990 and 2000 either through predation, inducing diapause, or both.
Electronic supplementary material Electronic supplementary material is available for this article at
and accessible for authorised users. 相似文献
18.
Mohammed Ramdani Roger J. Flower Najat Elkhiati with contributions from Hilary H. Birks Mohammed M. Kraïem Adel A. Fathi 《Aquatic Ecology》2001,35(3-4):389-403
Palaeolimnological studies were carried out on sediment cores from nine North African wetland lakes. The lakes represented a variety of habitats ranging from freshwater to mixohaline conditions and with and without direct connections to the sea. Sediment cores were examined for records of recent environmental change during the 20th century period. Faunal remains analysed in the sediments included those of Cladocera, Ostracoda, Chironomidae, Mollusca and, at the sites with marine connections, Foraminifera.
Cyprideis
torosa littoralis was the most common ostracod, occurring in sediments from the seven sites linked with the sea and also in brackish water Sidi Bou Rhaba. In acid Megene Chitane ostracods were scarce, being represented by a single species (Cypria ophtalmica).
Candona neglecta completely disappeared at two sites (Sidi Bou Rhaba and Bokka) during the 20th century. Of the Cladocera, Chydorus sphaericus was common in the moderately mixohaline sites and but Heterocypris salina occurred only where marine salinities were occasionally achieved (in Zerga, Ichkeul and Korba). Microinvertebrate assemblages in the Nile Delta lake cores and to a less extent in Zerga showed a clear response indicative of more fresher conditions occurring during the latter part of the 20th century. However the freshening trend began prior to construction of the Aswan High Dam (mid 1960s).With the exception of the most saline site (Korba), microinvertebrate communiuties at all the CASSARINA sites have experienced major disturbances during the 20th century. Changes in freshwater availability associated with increased human usage of water resources is perceived as a major factor regulating the abundance and occurrence of aquatic microinvertebrate species at these sites 相似文献
19.
Ostracod diversity and abundance was studied in 10 different types of water bodies of Belarus (bogs, brooks, canals, oxbows,
ponds, reservoirs, rivers, springs, shoal of lake and temporary pools). Hydrochemical variables, sediment, and vegetation
were analyzed. In total 156 different localities were investigated. Habitat diversity was based mainly upon the closely correlated
hydrochemical variables of mineralization (hardness total and carbonate, conductivity, total value of dissolved substances),
although bottom, vegetation characteristics and other factors (pH, dissolved oxygen, nutrients) were also significant. The
ostracods found included 62 species in 27 genera comprising 8 cosmopolitan, 17 Holarctic, 13 Palearctic species; 21 of these
species are known from central and southern Europe and adjacent areas, while 3 are characteristic for eastern Europe. The
distribution of freshwater ostracod assemblages reflected the habitat and depended on water body type. Heterogeneous oxbows
and temporary pools supported 37 species, while other types of pool maintained only 27–14 species. The population density
of different species varied from 0.5 to more than 10 000 ind./m2. Indices of local alpha diversity were significantly correlated with the number of species and temperature and were maximal
in heterogeneous habitats. The variation of population density was not connected with habitat patterns but appeared to be
regulated by the biotic interactions in the community. Habitat diversity, verified by the beta-diversity indices, enabled
us to find localities with a similar heterogeneity level and species richness. Beta-diversity values were independent of species
number as well as abundance but a significant positive correlation (p < 0.05) was found with temperature, pH and dissolved oxygen. This index probably reflected the general patterns of different
localities. 相似文献
20.
Abstract
The non-native rusty crayfish (Orconectes rusticus) has invaded many lakes of northern Wisconsin, profoundly changing littoral zones in the process. There are other lakes that
have been invaded, but do not exhibit these changes. We hypothesized that endogenous feedbacks could form involving rusty
crayfish, the macrophytes they destroy, and Lepomis species whose abundance is positively related to macrophyte abundance and also consume juvenile crayfish. We assessed this
proposal with long-term data from one lake, a regional comparative study, and a case study of Lepomis predation on crayfish. Through time and across lakes, abundances of rusty crayfish, littoral macrophytes and species of the
genus Lepomis were related in a fashion that indicated a set of feedbacks that regulate the abundance of all three. Intense predation on
juvenile crayfish by abundant Lepomis is capable of maintaining some crayfish populations at low abundance. Thus, some lakes display profound ecological changes
where crayfish achieve high abundance, and others sustain crayfish at low abundance. Consequently, lakes invaded by rusty
crayfish may take on the appearance of alternative ecological regimes. Direct experimentation is necessary to determine if,
and under what conditions, a lake can exist in either regime.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献