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991.
The impact of regulation and salinisation on floodplain lakes: the lower River Murray,Australia 总被引:1,自引:1,他引:0
Floodplain lakes along the lower River Murray are subject to a wide range of human impacts including regulation, abstraction,
elevated saline groundwater tables, increased nutrient and sediment fluxes and introduced biota. These perturbations are superimposed
on those arising from high inter-annual rainfall variability, driven, at least in part, by variations in the southern oscillation.
Sediment-based archives from two lakes within a complex of wetlands, situated near to the first site of irrigation development
in the lower River Murray, reveal substantial changes over the last 800 years. While high levels of salinity are not foreign
to the sites, the recent trend is towards sustained high salinity levels. As a result of European impact, freshwater diatom
plankton now dominates Loch Luna, whilst Loveday Wetland is both more saline and nutrient rich than in the pre-European period.
In Loveday Wetland, the post-1960 increase in Haslea spicula (Hickie) Lange-Bertalot, may be driven by increases in sulphur salt concentrations that are believed to be a cause of recent
acidification episodes. A recent increase in more salt tolerant diatoms in Loch Luna suggests that this site, which has been
largely buffered from substantial change, is becoming more vulnerable to perturbation.
Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users. 相似文献
992.
To achieve robust simulations of past and future climate and their effect on aquatic biota, it is desirable to integrate results
from palaeolimnology, contemporary monitoring and process modelling. Here we analyse over 15 years of water quality monitoring
data from three lakes, Purrumbete, Colac and Bullen Merri from Western Victoria, Australia and their relationship to climate.
In the context of a large number of limnological and palaeoenvironmental studies from the region, we seek to refine understanding
of the primary forcing mechanisms that explain present, past and potentially future water quality variability in the lakes.
Our analysis shows that there are strong relationships between climate and water quality in these lakes of varied size and
salinity (average conductivity range 740–14,000 μS cm−1). The strongest climate–water quality relationship exists between air and water temperature, particular during the colder
months. Strong relationships also exist with air temperature and other parameters, most notably nutrient concentrations. Effective
precipitation also appears to exert a strong influence on water quality in these lakes. This influence is, by contrast with
the influence of air temperature, less direct. Nevertheless, these lakes of varying salt concentration exhibit a coherent
pattern of conductivity response to variation in effective precipitation, particularly during times of high moisture stress. 相似文献
993.
Phosphorus (P) dynamics in large shallow lakes are greatly influenced by physical processes such as wind-driven sediment resuspension,
at times scales from hours to years. Results from long-term (30 year) research on Lake Okeechobee, Florida (area 1,730 km2, mean depth 2.7 m) illustrate key features of these P dynamics. Variations in wind velocity result in changes in water column
transparency, suspended solids, and total P (TP). In summer there are diurnal changes in TP associated with afternoon winds,
and in winter, when strong winds occur for multiple days, monthly average TP remains high compared to summer. The magnitude
of daily and seasonal TP changes can exceed 100 μg l−1. Hurricanes and tropical storms also cause extreme changes in TP that are superimposed on seasonal dynamics. When a hurricane
passed 80 km south of the lake in October 1999, mean pelagic TP increased from 88 to 222 μg l−1. During large resuspension events, light attenuation is substantially increased, and this influences the biomass and spatial
extent of submerged plants, as well as water column TP. In Lake Okeechobee, TP concentrations typically are ∼20 μg l−1 when submerged plants are dense, and soluble reactive P concentrations are reduced below detection, perhaps by the periphyton
and plant uptake and by precipitation with calcium at high pH. In contrast, TP exceeds 50 μg l−1 when submerged plants and periphyton are absent due to prolonged deep water, and phytoplankton biomass and algal bloom frequency
both are increased. In Lake Okeechobee and other large shallow lakes, complex models that explicitly consider wind-wave energy,
hydrodynamics, and sediment resuspension, transport, and key biological processes are needed to accurately predict how lake
water TP will respond to different management options. 相似文献
994.
Kristen M. Reifel Brandon K. Swan Errel Olivo James M. Watts Charles C. Trees Stuart H. Hurlbert 《Hydrobiologia》2007,576(1):167-183
The influence of river inflows (2.5–5 g l−1) on phytoplankton and zooplankton was assessed with samples collected at 17 sites around the 50 km perimeter of the southern
basin of the Salton Sea (41–45 g l−1) along the 5 m isobath on 2 September and 11 December 2000. Phytoplankton generally increased in abundance downcurrent of
the points of inflow, but patterns in downcurrent abundance varied widely among species. Several diatom species showed large
increases; Chaetoceros muelleri var subsalsum, Cylindrotheca closterium and Thalassionema sp. increased up to 800-fold in abundance by ca. 20 km downcurrent from inflow points in September. In contrast, the dinoflagellates
Gyrodinium uncatenum and Prorocentrum minimum increased 6- and 4-fold, respectively, in December, and Gonyaulax grindleyi actually decreased downcurrent of the rivers in September. In September, patterns in downcurrent abundance were correlated
with the ratio of cell surface area to cell biovolume, with species with high ratios showing the largest increases. Zooplankton
abundances did not show regular trends downcurrent of river inflows except for the larvae of Balanus amphitrite, which increased in density ca. 100-fold. This increase most likely reflected the abundance of adult-colonized rocky substrates
near river inflow points. The strong upcurrent trends documented for some species seemed to have been due to the injection
of nutrient-rich water from central to nearshore areas and near-site mortality due to the presence of hydrogen sulfide. This
study gives a first glimpse of the complexity of the responses of nearshore plankton to river inflow and provides evidence
for how changes in factors such as current speed, nutrient supply and salinity stratification may influence plankton dynamics.
Guest Editor: John M. Melack
Saline Waters and their Biota 相似文献
995.
This work constitutes the first floristic and ecological analysis of the phytoplankton community of a volcanic freshwater
lake in Deception Island (62°57′S, 60°38′W, South Shetland Islands, Antarctica). The main limnological features and phytoplankton
size fractions were analyzed. Samples were taken during the austral summer of 2002 at two opposite sites. According to ANOVA
results performed with abiotic variables, no significant differences between sites were found. The phytoplankton community
showed low algal species richness, with an important contribution of the tychoplanktonic taxa. In terms of species number,
Bacillariophyceae was the dominant class. Autotrophic picoplankton registered the highest densities from the second sampling
date onwards. Nanophytoplankton was represented by unidentified chrysophycean organisms, which showed different distribution
patterns between sites. The net phytoplankton abundance remained low during the sampling period and was strongly correlated
with chlorophyll a concentration. Both nutrient concentrations and chlorophyll a values indicated oligotrophic conditions. 相似文献
996.
Gretchen J. A. Hansen Jordan S. Read Jonathan F. Hansen Luke A. Winslow 《Global Change Biology》2017,23(4):1463-1476
Temperate lakes may contain both coolwater fish species such as walleye (Sander vitreus) and warmwater fish species such as largemouth bass (Micropterus salmoides). Recent declining walleye and increasing largemouth bass populations have raised questions regarding the future trajectories and management actions for these species. We developed a thermodynamic model of water temperatures driven by downscaled climate data and lake‐specific characteristics to estimate daily water temperature profiles for 2148 lakes in Wisconsin, US, under contemporary (1989–2014) and future (2040–2064 and 2065–2089) conditions. We correlated contemporary walleye recruitment and largemouth bass relative abundance to modeled water temperature, lake morphometry, and lake productivity, and projected lake‐specific changes in each species under future climate conditions. Walleye recruitment success was negatively related and largemouth bass abundance was positively related to water temperature degree days. Both species exhibited a threshold response at the same degree day value, albeit in opposite directions. Degree days were predicted to increase in the future, although the magnitude of increase varied among lakes, time periods, and global circulation models (GCMs). Under future conditions, we predicted a loss of walleye recruitment in 33–75% of lakes where recruitment is currently supported and a 27–60% increase in the number of lakes suitable for high largemouth bass abundance. The percentage of lakes capable of supporting abundant largemouth bass but failed walleye recruitment was predicted to increase from 58% in contemporary conditions to 86% by mid‐century and to 91% of lakes by late century, based on median projections across GCMs. Conversely, the percentage of lakes with successful walleye recruitment and low largemouth bass abundance was predicted to decline from 9% of lakes in contemporary conditions to only 1% of lakes in both future periods. Importantly, we identify up to 85 resilient lakes predicted to continue to support natural walleye recruitment. Management resources could target preserving these resilient walleye populations. 相似文献
997.
Seventy‐five years of biodiversity decline of fish assemblages in Chinese isolated plateau lakes: widespread introductions and extirpations of narrow endemics lead to regional loss of dissimilarity
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Chengzhi Ding Xiaoming Jiang Zhicai Xie Sébastien Brosse 《Diversity & distributions》2017,23(2):171-184
998.
Cynthia Gerlein‐Safdi Paul P. G. Gauthier Craig James Sinkler Kelly Krispin Caylor 《Plant, cell & environment》2017,40(10):2095-2108
Spatial patterns of leaf water isotopes are challenging to predict because of the intricate link between vein and lamina water. Many models have attempted to predict these patterns, but to date, most have focused on monocots with parallel veins. These provide a simple system to study, but do not represent the majority of plant species. Here, a new protocol is developed using a Picarro induction module coupled to a cavity ringdown spectrometer to obtain maps of the leaf water isotopes (18O and 2H). The technique is applied to Colocasia esculenta leaves. The results are compared with isotope ratio mass spectrometry. In C. esculenta, a large enrichment in the radial direction is observed, but not in the longitudinal direction. The string‐of‐lakes model fails to predict the observed patterns, while the Farquhar–Gan model is more successful, especially when enrichment is accounted for along the radial direction. Our results show that reticulate‐veined leaves experience a larger enrichment along the axis of the secondary veins than along the midrib. We hypothesize that this is due to the lower major/minor vein ratio that leads to longer pathways between major veins and sites of evaporation. 相似文献
999.
Biogeochemical studies were undertaken of a 65-cm long sediment core from Lake Cantara South, South Australia. 14C determinations indicated that the sediments had been deposited over 2000 years. Changes with sediment depth in the concentration or ratio of the following were determined: (i) total organic carbon, total carbonate (inorganic) carbon, total sulfur, total carbon, total inorganic and organic sulfur, atomic C/N, and sulfate/chloride; (ii) n-alkanes; (iii) a highly branched isoprenoid alkane, and (iv) steroids. Interpretation of the changes with sediment depth indicated the nature of changes that took place when the system changed from a protected marine lagoon to an isolated (athalassic) saline lake. This change took place about 1000 years ago. 相似文献
1000.
Nutrient limitation of bacterioplankton and phytoplankton in humic lakes in northern Sweden 总被引:2,自引:0,他引:2
Mats Jansson Ann-Kristin Bergström Stina Drakare & Peter Blomqvist 《Freshwater Biology》2001,46(5):653-666
1. Two small humic lakes in northern Sweden with concentrations of dissolved organic carbon (DOC) between 15 and 20 mg L–1 were fertilized with inorganic phosphorus (P) and inorganic nitrogen (N), respectively. A third lake was unfertilized and served as a control. In addition to this lake fertilization experiment, data from different regional surveys were used to assess the role of different limiting factors.
2. The P fertilization had no effects on bacterioplankton or phytoplankton, while phytoplankton were significantly stimulated by N fertilization. Inorganic nutrient limitation of bacterioplankton was a function of DOC concentration in water of the investigated region and nutrient-limited bacteria were found only in lakes with DOC concentrations less than around 15 mg L–1
3. The fertilization experiments demonstrated that the DOC-rich experimental lakes contained a bioavailable pool of P that was not utilized to its full potential under natural conditions. The overall mobilization of energy (bacterioplankton plus phytoplankton) in the experimental lakes was restricted by lack of inorganic N. 相似文献
2. The P fertilization had no effects on bacterioplankton or phytoplankton, while phytoplankton were significantly stimulated by N fertilization. Inorganic nutrient limitation of bacterioplankton was a function of DOC concentration in water of the investigated region and nutrient-limited bacteria were found only in lakes with DOC concentrations less than around 15 mg L
3. The fertilization experiments demonstrated that the DOC-rich experimental lakes contained a bioavailable pool of P that was not utilized to its full potential under natural conditions. The overall mobilization of energy (bacterioplankton plus phytoplankton) in the experimental lakes was restricted by lack of inorganic N. 相似文献