Lake Nutrient Concentrations Research Articles

Multitrophic biodiversity patterns and environmental descriptors of sub‐Arctic lakes in northern Europe

Abstract Arctic and sub‐Arctic lakes in northern Europe are increasingly threatened by climate change, which can affect their biodiversity directly by shifting thermal and hydrological regimes, and indirectly by altering landscape processes and catchment vegetation. Most previous studies of northern lake biodiversity responses to environmental changes have focused on only a single organismal group. Investigations at whole‐lake scales that integrate different habitats and trophic levels are currently rare, but highly necessary for future lake monitoring and management. We analysed spatial biodiversity patterns of 74 sub‐Arctic lakes in Norway, Sweden, Finland, and the Faroe Islands with monitoring data for at least three biological focal ecosystem components (FECs)—benthic diatoms, macrophytes, phytoplankton, littoral benthic macroinvertebrates, zooplankton, and fish—that covered both pelagic and benthic habitats and multiple trophic levels. We calculated the richnessrelative (i.e. taxon richness of a FEC in the lake divided by the total richness of that FEC in all 74 lakes) and the biodiversity metrics (i.e. taxon richness, inverse Simpson index (diversity), and taxon evenness) of individual FECs using presence–absence and abundance data, respectively. We then investigated whether the FEC richnessrelative and biodiversity metrics were correlated with lake abiotic and geospatial variables. We hypothesised that (1) individual FECs would be more diverse in a warmer and wetter climate (e.g. at lower latitudes and/or elevations), and in hydrobasins with greater forest cover that could enhance the supply of terrestrial organic matter and nutrients that stimulated lake productivity; and (2) patterns in FEC responses would be coupled among trophic levels. Results from redundancy analyses showed that the richnessrelative of phytoplankton, macrophytes, and fish decreased, but those of the intermediate trophic levels (i.e. macroinvertebrates and zooplankton) increased with decreasing latitude and/or elevation. Fish richnessrelative and diversity increased with increasing temporal variation in climate (temperature and/or precipitation), ambient nutrient concentrations (e.g. total nitrogen) in lakes, and woody vegetation (e.g. taiga forest) cover in hydrobasins, whereas taxon richness of macroinvertebrates and zooplankton decreased with increasing temporal variation in climate. The similar patterns detected for richnessrelative of fish, macrophytes, and phytoplankton could be caused by similar responses to the environmental descriptors, and/or the beneficial effects of macrophytes as habitat structure. By creating habitat, macrophytes may increase fish diversity and production, which in turn may promote higher densities and probably more diverse assemblages of phytoplankton through trophic cascades. Lakes with greater fish richnessrelative tended to have greater average richnessrelative among FECs, suggesting that fish are a potential indicator for overall lake biodiversity. Overall, the biodiversity patterns observed along the environmental gradients were trophic‐level specific, indicating that an integrated food‐web perspective may lead to a more holistic understanding of ecosystem biodiversity in future monitoring and management of high‐latitude lakes. In future, monitoring should also focus on collecting more abundance data for fish and lower trophic levels in both benthic and pelagic habitats. This may require more concentrated sampling effort on fewer lakes at smaller spatial scales, while continuing to sample lakes distributed along environmental gradients.

Spring to summer nitrogen level in a brackish lake is higher in abundant snowmelt years: Correlation and causation.

Eutrophication is an issue of concern in many brackish lakes with an agricultural watershed. The amount of snowfall in snowy areas is anticipated to decline because of global climate change. The aim of this study was to assess the impact of changes in the inflow of snowmelt on the nutrient concentrations of a downstream brackish lake. In Lake Ogawara, a brackish lake in a snow-covered agricultural area of Japan, we examined the relationships between inflowing river discharge (D/C) during spring and total nitrogen (TN) and total phosphorus (TP) concentrations in the mixolimnion of the lake ([TNmix ] and [TPmix ], respectively) using 29yr of monitoring data. In addition, we assessed the causal relationship between the D/C and the lake nutrient concentrations. There was large year-to-year variation in D/C during April (D/CApr ), which accounted for 7-31% of the mixolimnion volume. Significant positive correlations were observed between D/CApr and [TNmix ] from the ensuing April to September. On an annual basis, 49% of the interannual variation of the mean [TNmix ] during the ensuing April to September was explained by the interannual variation of D/CApr . Therefore, D/CApr could be useful as a simple index to [TNmix ] in the ensuing spring to summer. It is notable that the relationships between D/CApr and [TNmix ] from April to September was indicated to be acausal by statistical causal inference. Common climate conditions that increase D/CApr (i.e., a cold winter with a high level of precipitation) were found to drive other biogeochemical processes that increased [TNmix ] during the ensuing spring to summer.

Variation in phytoplankton pigment composition in relation to mixing conditions in temperate South-Central Chilean lakes

Thermal lake properties are sensitive to changes in windiness and precipitation, and affect the physical and chemical properties of the water column, which in turn control phytoplankton dynamics and primary production. We assessed the use of phytoplankton pigment profiling as a potential indicator of stratification conditions in temperate lakes in South-Central Chile. Spring and early summer phytoplankton pigment profiles and the physical and chemical limnology were analyzed in 43 lakes ranging in size, depth, altitude and catchment characteristics. Eleven lakes were sampled during both seasons. Variation in pigment composition between lakes was primarily related to stratification conditions and mixed layer light availability at the time of sampling. The dinoflagellate marker pigment peridinin was more abundant in more deeply mixed lakes with a lower mean irradiance, while chlorophyte pigments (chlorophyll b, lutein) tended to be higher in shallow (high-light) epilimnia. Diatom and chrysophyte pigments (fucoxanthin) dominated under less thermally stable and more variable light conditions. Cyanobacteria pigments (zeaxanthin), probably derived from picocyanobacteria, were relatively more abundant in very transparent, low productive lakes. Lakes in close vicinity of active volcanoes were enriched in silica and PO4-P and characterised by elevated chlorophyte marker pigments. Within strongly stratified lakes, in which the euphotic zone extended into the hypolimnion, cryptophyte pigments (alloxanthin) characterized the deep chlorophyll maxima while the epilimnion was consistently enriched with the photoprotective xanthophyll-cycle pigment violaxanthin. We conclude that major algal groups, represented by pigment biomarkers, are largely driven by changes in lake water column stratification and related mixed layer light availability as well as nutrient concentrations in temperate Chilean freshwater lakes.

Can the watershed non-point source phosphorus flux amount be reflected by lake sediment?

An understanding of the quantitative relationship between watershed non-point source (NPS) pollution and lake nutrient enrichment is essential for the environmental management of water bodies. However, a lack of data availability and integration limit our understanding of this relationship. The most critical bottlenecks are the lack of adequate support for watershed-lake integrated data, a lack of data of the nutrient loading from watersheds into a lake as NPS, and the long-term time series data of lake nutrient concentrations. Since lake sediment is the ultimate destination of watershed nutrients, this study aimed to reveal the relationship between watershed phosphorus (P) concentrations that are transported into lakes and lake P concentrations by using inlet sediments as an indicator. Three typical sub-basins within Hongze Lake, China were selected as the study site, and 30-year dataset was calculated using the technology integration of remote sensing, sediment chemical analysis and SWAT model assessment. It can be concluded that, first, the Mineral-P (Min-P) accounted for nearly 65% of the watershed Total P (TP) loss, which varied over different basins and temporal periods. Second, the relationship between watershed P loss into lakes and sediment P concentrations represented obvious variation among different basins, sediment depths and P states. With respect to different basins, the highest correlation appeared in Basin 1, which had a R2 value of 0.65 for Min-P. With respect to different P states, the Inorganic-P (IP) showed a closer relationship between watershed and lake P than Organic-P (OP), and the correlation coefficient (r) was higher than 0.6 in Basin 1 and Basin 3 for IP. In addition, the calcium-phosphorus ratio (Ca-P), which is largely sourced from watershed rock detritus by eroded runoff, played the most critical role among different Min-P states in the relatively ideal relationship of IP. With respect to different sediment depths, a stratification phenomenon existed in Basin 2 and Basin 3, which differed at specific depths. In particular, the ideal relationship only existed within the 7 cm depth from the bottom in basin 2, and this value expands to 10 cm for basin 3. This diversity was influenced by the integration roles from external and endogenous sources. All the findings indicated that lake surface sediment can be used as a proxy to represent NPS P loading under specific conditions. The relationship between watershed P loss and lake sediment P concentration was largely decided by land use/cover change (LUCC), meteorological conditions, and lake resuspension.

Influence of land use and rainfall variability on nutrient concentrations in Florida Lakes

Xiong C, Hoyer MV. Influence of land use and rainfall variability on nutrient concentrations in Florida lakes. Lake Reserv Manage. 35:25–37.This research examined impacts of regional differences (total phosphorus zones [TP Zones]), land uses within watersheds (agriculture, urban, forest and wetland), and rainfall variability on nutrient concentrations (phosphorus and nitrogen) in Florida lakes (n = 87). Nutrient concentrations varied directly with TP Zones, which can be used as background nutrient concentrations within regions of Florida. After accounting for regional differences, lakes within watersheds with high percent agriculture tended to have higher nutrient concentrations, though relationships with nitrogen were strongest, suggesting different nutrient-transport mechanisms. Lakes within watersheds with high percent urban development showed no significant effect on nutrient concentrations, suggesting good nutrient management in urban areas. Lakes in watersheds dominated by forested land cover had low nitrogen concentration reflecting nutrient-buffering capabilities of forest stands. Lakes in watersheds with greater wetland coverage tended to have high nutrient concentrations, conflicting with previous studies and reflecting the complex nutrient-related processes that occur within wetlands. Cumulative rainfall deviations measured over a 20 yr period were significantly correlated (both positively and negatively) with nutrient concentrations within approximately 40% of the study lakes and the mechanisms driving these relations may overshadow impacts of land use within watersheds and changes in land use over time on lake nutrient concentrations. A thorough investigation of watershed land uses and relations between rainfall and limnological mechanisms must be considered before applying a nutrient management strategy to individual lakes.

Parasitic versus nutritional regulation of natural fish populations.

Although parasites are expected to affect their host's fitness, quantitative proof for impacts of parasitism on wild populations is hampered by confounding environmental factors, including dietary resource. Herein, we evaluate whether the physiological conditions of European perch (Perca fluviatilis) in three large peri‐alpine lakes (Geneva, Annecy, and Bourget) depend on (a) the nutritional status of the juvenile fish, as revealed by stable isotope and fatty acid compositions, (b) the prevalence of the tapeworm Triaenophorus nodulosus, a parasite transmitted to perch through copepod preys, or (c) interactive effects of both factors. At the scale of lake populations, the deficit in growth and fat storage of juvenile perch during their first summer coincides with a high parasite prevalence and also a low quality of dietary resource. Yet, at the individual level, parasites had no evident effect on the growth of the juvenile perch, while impacts on fat storage appeared only at the highest prevalence of the most infected lake. Fatty acid and stable isotope analyses of fish tissue do not reveal any impact of T. nodulosus on diet, physiology, and feeding behaviour of fish within lakes. Overall, we found a low impact of parasitism on the physiological condition and trophic status of juvenile perch at the end of their first summer. We find instead that juvenile perch growth and fat storage, both factors tied to their winter survival, are under strong nutritional constraints. However, the coinciding nutritional constraints and parasite prevalence of perch juveniles in these three lakes may result from the indirect effect of lake nutrient concentrations, which, as a major control of zooplankton communities, simultaneously regulate both the dietary quality of fish prey and the host–parasite encounter rates.

Declining ambient water phosphorus concentrations in Massachusetts’ rivers from 1999 to 2013: Environmental protection works

Over the last century, nutrient concentrations in streams, rivers, lakes and ponds have increased substantially in the United States. Elevated phosphorus levels are a concern due to their ability to cause changes in freshwater ecosystems that are detrimental to humans and wildlife. In the present study, long-term trends in total phosphorus (TP) concentrations from 20 rivers in central Massachusetts from 1999 to 2013 were investigated. Kendall's correlation coefficients were used to demonstrate that 18 of the 20 rivers had significant reductions in TP concentrations (P < 0.05). A similar trend was found when flow-adjusted TP concentrations were analyzed. At the beginning of monitoring activities, the average TP concentration in 9 of the 20 rivers was greater than 0.05 mg/L and 6 of these 9 rivers contained TP concentrations greater than 0.1 mg/L; about fifteen years later, only 3 rivers contained TP greater than 0.05 mg/L and none had concentrations> 0.1 mg/L. TP decreases were greater in rivers with more anthropogenic inputs. Principal component analysis (PCA) revealed that the decline of TP in these Massachusetts streams is likely the result of advancements in wastewater treatment and implementation of effective non-point source management practices.

The potential of Earth Observation in modelling nutrient loading and water quality in lakes of southern Québec, Canada

Phosphorus and nitrogen are key nutrients that affect abundance and growth of aquatic primary producers but cannot be directly remotely sensed as their dissolved or organic forms do not interact with the remote sensing signal. In addition, other lake water quality variables such as chlorophyll a and Secchi disk depth, have been previously successfully estimated with remote sensing, but the retrieval algorithms are site-, season-, and/or scene-specific. Such algorithms do not take into account lake typological features, which can affect the sensitivity of lake to change, or catchment characteristics, for example, land cover that is a major driver of lake water quality change. Here we propose a novel approach that utilises remotely sensed land cover information in the catchment to estimate phosphorus, nitrogen and chlorophyll a concentrations in lake waters. We use land cover type-specific nutrient export coefficients and the NASA MODIS (Moderate Resolution Imaging Spectroradiometer) Land Cover Type product showing that nutrient loading based on remote sensing can explain up to 75% of variability in lake nutrient concentrations and 58% of variability in lake chlorophyll a concentrations. In addition, we show that land cover information, supplemented by satellite measurements and lake morphometry data are good predictors of chlorophyll a (R2 = 0.77) and Secchi disk depth (R2 = 0.87) in lakes with different trophic statuses and in different months and years.

Lake nutrient stoichiometry is less predictable than nutrient concentrations at regional and sub-continental scales.

Production in many ecosystems is co-limited by multiple elements. While a known suite of drivers associated with nutrient sources, nutrient transport, and internal processing controls concentrations of phosphorus (P) and nitrogen (N) in lakes, much less is known about whether the drivers of single nutrient concentrations can also explain spatial or temporal variation in lake N:P stoichiometry. Predicting stoichiometry might be more complex than predicting concentrations of individual elements because some drivers have similar relationships with N and P, leading to a weak relationship with their ratio. Further, the dominant controls on elemental concentrations likely vary across regions, resulting in context dependent relationships between drivers, lake nutrients and their ratios. Here, we examine whether known drivers of N and P concentrations can explain variation in N:P stoichiometry, and whether explaining variation in stoichiometry differs across regions. We examined drivers of N:P in ~2,700 lakes at a sub-continental scale and two large regions nested within the sub-continental study area that have contrasting ecological context, including differences in the dominant type of land cover (agriculture vs. forest). At the sub-continental scale, lake nutrient concentrations were correlated with nutrient loading and lake internal processing, but stoichiometry was only weakly correlated to drivers of lake nutrients. At the regional scale, drivers that explained variation in nutrients and stoichiometry differed between regions. In the Midwestern U.S. region, dominated by agricultural land use, lake depth and the percentage of row crop agriculture were strong predictors of stoichiometry because only phosphorus was related to lake depth and only nitrogen was related to the percentage of row crop agriculture. In contrast, all drivers were related to N and P in similar ways in the Northeastern U.S. region, leading to weak relationships between drivers and stoichiometry. Our results suggest ecological context mediates controls on lake nutrients and stoichiometry. Predicting stoichiometry was generally more difficult than predicting nutrient concentrations, but human activity may decouple N and P, leading to better prediction of N:P stoichiometry in regions with high anthropogenic activity.

Lake Nutrient Responses to Integrated Conservation Practices in an Agricultural Watershed.

Watershed-scale management efforts to reduce nutrient loads and improve the conservation of lakes in agricultural watersheds require effective integration of a variety of agricultural conservation best management practices (BMPs). This paper documents watershed-scale assessments of the influence of multiple integrated BMPs on oxbow lake nutrient concentrations in a 625-ha watershed of intensive row-crop agricultural activity during a 14-yr monitoring period (1996-2009). A suite of BMPs within fields and at field edges throughout the watershed and enrollment of 87 ha into the Conservation Reserve Program (CRP) were implemented from 1995 to 2006. Total phosphorus (TP), soluble reactive phosphorus (SRP), ammonium, and nitrate were measured approximately biweekly from 1996 to 2009, and total nitrogen (TN) was measured from 2001 to 2009. Decreases in several lake nutrient concentrations occurred after BMP implementation. Reductions in TP lake concentrations were associated with vegetative buffers and rainfall. No consistent patterns of changes in TN or SRP lake concentrations were observed. Reductions in ammonium lake concentrations were associated with conservation tillage and CRP. Reductions in nitrate lake concentrations were associated with vegetative buffers. Watershed simulations conducted with the AnnAGNPS (Annualized Agricultural Non-Point Source) model with and without BMPs also show a clear reduction in TN and TP loads to the lake after the implementation of BMPs. These results provide direct evidence of how watershed-wide BMPs assist in reducing nutrient loading in aquatic ecosystems and promote a more viable and sustainable lake ecosystem.

Sensitivity of plankton indices to lake trophic conditions.

Herein, we report the response of indices based on phytoplankton and zooplankton and their combination to different nutrient concentrations in lakes. The study was carried out in ten lakes in northeastern Poland. Integrated samples were collected from the epilimnion during the summer of 2012–2013. Secchi disk visibility (SD), total phosphorus (TP), total nitrogen (TN), and chlorophyll a were used as proxies for eutrophication. We calculated 16 plankton indices: two phytoplankton indices, six crustacean indices, five rotiferan indices, two zooplankton diversity indices, and one combined phytoplankton and zooplankton index. Among them, nine indices with the strongest correlations with TP were selected: percentage share of Crustacean species indicative of high trophy in the indicative group’s numbers (IHTCRU), percentage share of Rotifera species indicative of high trophy in the indicative group’s numbers IHTROT, Crustacean ratio of biomass to numbers B/NCRU, phytoplankton trophic index (TITP+TN), Margalef’s index, percentage share of cyclopoid biomass in total biomass of Crustacea (CB), Rotifera numbers (NROT), biomass of Cyclopoida (BCY), and ratio of the cyclopoid biomass to the biomass of Cladocera (CY/CL). The sensitivity of the normalized values of these indices to proxies of eutrophication was tested. IHTCRU, IHTROT, and B/NCRU were the most sensitive and gave the strongest responses at lower TP concentrations (<35 μg/L). The phytoplankton trophic index, TITP+TN, together with the zooplankton-based Margalef’s index and CB were very sensitive in both low (<35 μg/L) and high (>60 μg/L) TP conditions. On the other hand, NROT, BCY, and CY/CL were slightly sensitive at low TP concentrations while their reaction was notable at high TP concentrations. A similar pattern of response was observed for TN concentration and SD visibility.

Source water inputs and catchment characteristics regulate limnological conditions of shallow subarctic lakes (Old Crow Flats, Yukon, Canada)

Climate variations exert rapid and strong control on the hydrology of shallow lake-rich subarctic landscapes, but knowledge of the associated effects on limnological conditions remains limited. Based on analysis of water isotope compositions and water chemistry at 56 lakes across Old Crow Flats (Yukon), a large thermokarst landscape, we assess if differences in source water inputs (snowmelt versus rainfall) affect limnological conditions during the ice-free season of 2007 and explore influences of catchment features. Results demonstrate that lakes with snowmelt-dominated source waters, situated in catchments that support tall shrub and woodland vegetation, possess significantly higher (p &lt; 0.05) nutrient (N, P, SiO2) and dissolved organic carbon concentrations than lakes with rainfall-dominated source waters. Conversely, rainfall-dominated lakes, located in catchments dominated by dwarf shrubs and sparse vegetation, have significantly higher concentrations of major ions (Mg2+, Na+, SO42−) and pH. These limnological differences persisted throughout the ice-free season. We suggest that interaction of snowmelt with organic-rich detritus raises nutrient concentrations in snowmelt-dominated lakes and that evaporative-concentration, shoreline erosion and possibly rainfall runoff are processes that raise the ionic content of lakes with rainfall-dominated source waters. Knowledge of these relations improves the ability to anticipate limnological responses to ongoing and future climate and hydrological change in Arctic and subarctic regions.

Impact of glacier changes on ecosystem of proglacial lakes in high mountain regions of East Siberia (Russia)

Mountain lakes in East Siberia have been studied for recent changes in water chemistry, turbidity and diatom assemblages preserved in bottom sediments. We performed a regional analysis of the relative effect of climate and glacier changes on change in diatom diversity and supply of meltware in proglacial lakes. We analysed sediment records from East Siberian glacier lakes using geochemical and diatoms proxies. We found that dramatic changes in communities and abundance of diatoms and biogenic proxy could be induced by low nutrient concentrations in glacial lakes and high turbidity due to active degradation of glaciers and snow patches as a result of the global increase in temperature in the Northern Hemisphere. Our evidences show that diatoms have been gradually decreased since ca. the 1880s. A significant tendency towards diatom reducing occurred at high summer regional temperatures. This tendency may be attributed to the fact that glaciers and snow patches thawed actively in East Siberia during ca. 1880–1958, which was induced by the beginning of the Recent Warming (ca. 1850–1860) and a long period of relatively warm regional climate from ca. 1900 to 1960.

Geographic patterns of lake macrophyte communities and species richness at regional scale

AbstractQuestionsAre community composition and species richness of aquatic macrophytes determined primarily by local (habitat heterogeneity and water quality) or regional (climate) patterns at regional scale? Do two macrophyte functional groups (i.e. emergent and submerged macrophytes) respond similarly to local and regional patterns? Are lake macrophytes and explanatory variables geographically structured?LocationThe US state of Minnesota.MethodsThe community composition and species richness of aquatic flora was studied using presence–absence data in 454 lakes, covering the entire US state of Minnesota. In addition, community composition and species richness of emergent and submerged macrophytes was investigated separately. Variation partitioning based on partial redundancy analysis and partial linear regression was used to study the relative roles of water quality, habitat heterogeneity, climate and sampling effort in explaining community composition and species richness of lake macrophytes, respectively.ResultsMacrophyte community composition and species richness (all taxa and two functional groups) were explained by water quality and climate. Alkalinity and total phosphorus were water quality variables that most affected community composition of aquatic flora, and macrophyte species richness decreased with increasing concentrations of these two variables. Maximum temperature of the warmest month and mean annual temperature most affected plant community composition, whereas species richness had a negative relationship with minimum temperature of the coldest month. Most significant explanatory variables (e.g. alkalinity, total phosphorus and temperature) were geographically structured, showing a latitudinal change.ConclusionsCommunity composition and species richness of macrophytes were congruently influenced by regional (climate) and local patterns (water quality) at regional scale. Community composition and species richness of helophytes and submerged macrophytes were equally explained by environmental gradients. The latitudinal change in these most significant environmental variables was related to calcareous soils and intensive agriculture, which were situated in the southern part of the state. Macrophyte species richness showed a reverse latitudinal gradient, which was likely due to high nutrient concentrations in southern latitude lakes. Water quality primarily filters species from the regional species pool, allowing only species tolerating high nutrient concentrations, e.g. invasive plants, to survive at southern latitudes.

Regulatory protection and definition for recreational uses of Florida lakes

National- and state-level water quality policies clearly set forth the intention to protect recreational uses of lakes. Nevertheless, the Clean Water Act, the Florida Water Resources Act, and Florida's Surface Water Quality Standards fail to define recreational uses of lakes. This research presents a generalized definition for recreational uses of Florida lakes and a quantification of the proportion of Floridians that recreate in lakes. Data collected from a survey of 503 Floridians indicate that approximately 23% of Floridians participate in lake-based recreation. A derived definition for the recreational use of Florida lakes, in order of reported use frequency, is “recreation activities of Florida lakes include, but are not limited to, relaxing, boating, fishing, viewing nature, picnicking, swimming, camping, tubing, hunting, wakeboarding, diving, and water skiing.” This generalized definition highlights the diversity of activities occurring in Florida lakes and can inform the regulatory process related to the management of lake water nutrient concentrations. As Florida moves forward in establishing management strategies for its surface waters, defining recreational uses for its diverse set of lakes is imperative to their protection.

Estimating Summer Nutrient Concentrations in Northeastern Lakes from SPARROW Load Predictions and Modeled Lake Depth and Volume

Global nutrient cycles have been altered by the use of fossil fuels and fertilizers resulting in increases in nutrient loads to aquatic systems. In the United States, excess nutrients have been repeatedly reported as the primary cause of lake water quality impairments. Setting nutrient criteria that are protective of a lakes ecological condition is one common solution; however, the data required to do this are not always easily available. A useful solution for this is to combine available field data (i.e., The United States Environmental Protection Agency (USEPA) National Lake Assessment (NLA)) with average annual nutrient load models (i.e., USGS SPARROW model) to estimate summer concentrations across a large number of lakes. In this paper we use this combined approach and compare the observed total nitrogen (TN) and total phosphorus (TN) concentrations in Northeastern lakes from the 2007 National Lake Assessment to those predicted by the Northeast SPARROW model. We successfully adjusted the SPARROW predictions to the NLA observations with the use of Vollenweider equations, simple input-output models that predict nutrient concentrations in lakes based on nutrient loads and hydraulic residence time. This allows us to better predict summer concentrations of TN and TP in Northeastern lakes and ponds. On average we improved our predicted concentrations of TN and TP with Vollenweider models by 18.7% for nitrogen and 19.0% for phosphorus. These improved predictions are being used in other studies to model ecosystem services (e.g., aesthetics) and dis-services (e.g. cyanobacterial blooms) for ~18,000 lakes in the Northeastern United States.

Stable isotopic analysis of fossil chironomids as an approach to environmental reconstruction: state of development and future challenges

Remains of chironomid larvae, especially their strongly sclerotized head capsules, can be found abundantly and well preserved in most lake sediment records. These remains mainly consist of chitin and proteins and, since their chemical composition does not seem to be strongly affected by decompositional processes, they can be used to develop palaeoenvironmental reconstructions based on their stable isotopic composition. Here we review available stable isotope studies based on fossil chironomids and indicate future research necessary to further develop this still relatively new research approach. Efforts to produce stable isotope records based on fossil chironomids have mainly examined the elements H, N, C, and O. They have focussed on (1) developing the methodology for preparing samples for isotopic analysis, (2) laboratory studies cultivating chironomid larvae under controlled conditions to determine the factors affecting their stable isotopic composition, (3) ecosystem-scale studies relating stable isotopic measurements of fossil chironomid assemblages to environmental conditions, and (4) developing first down-core records describing past changes in the stable isotopic composition of chironomid assemblages. These studies have shown that chemical sample pretreatment may affect the isotopic composition for some elements. Laboratory runs suggest that the diet of the larvae influences their stable isotopic composition for H, N, C and O, whereas stable isotopes in the ambient water also strongly influence their oxygen and to a lesser extent hydrogen isotopic composition. These experiments also indicate only minor offsets between the nitrogen and carbon isotopic composition of chironomid soft tissue and the fossilizing head capsules, whereas for hydrogen and oxygen this offset remains to be explored. Though few datasets have been published, the available ecosystem studies and developed down-core sediment records indicate that stable isotopes in chironomid remains have the potential to provide reconstructions of past climatic change (H, O) and insights into past food web structure, methane production and pollution of lake ecosystems (N, C). Future efforts will be necessary to develop these approaches including more detailed analyses of the effects of sample pretreatment on stable isotope measurements on chitinous fossils, more extensive laboratory studies constraining the effects of external factors (e.g., isotopic composition of food and ambient water, temperature) on stable isotopes in chironomid larvae, and surveys exploring seasonal changes in the isotopic composition of chironomid larvae and assessing how this seasonality influences fossil assemblages. Finally, multi-site field studies relating chironomid δD, δ15N, δ13C and δ18O to parameters such as δ18O of precipitation, air and water temperatures, and nutrient and greenhouse gas concentrations in lakes will be necessary to assess the extent to which these stable isotopic approaches can provide quantitative reconstructions of parameters of interest for palaeoclimatological and palaeoenvironmental research.doi: 10.5324/fn.v31i0.1436.Published online: 17 October 2012.

Past and current trophic development in Lake Ammersee - Alterations in a normal range or possible signals of climate change?

In the past decades, nutrient concentrations in several pre-Alpine lakes in central Europe have increased due to human activity in the catchment area. Here, we examine whether this trend will continue in the future, through our analysis of the development of the trophic status, over a period of 25 years (1984 – 2009), of the pre-Alpine, dimictic tempered Lake Ammersee (South-Eastern Germany). The lake showed signs of an elevated eutrophic status until the 1990s. Immense management activities in the catchment area led to a reduction in the nutrient load in the tributaries. The study of dissolved oxygen, total phosphorus (TP) and chlorophyll-a revealed a substantial improvement in the trophic conditions of the lake. We identified a transition period in the development of trophic levels during the years 1996/1997. Therefore, our investigation is divided into two periods: 1984 –1996 and 1997– 2009. By comparing values during these two periods, we found that the annual mean TP concentrations of the complete water column declined from 18.2 μg l (1984 –1996) to 8.8 μg l (1997–2009). During this period the chlorophyll-a values are in relationship to other trophic variables such as TP, dissolved oxygen and sight depths (R between 0.41 and 0.56). At the same time, during the summer months, the surface temperature in the epilimnion increased (by about 0.8 K per decade), which was approximately in line with the thermal increase (about 0.6 K per decade) in the northern hemisphere (Pearson’s correlation coefficient, omitting 2006, of 0.81). In conclusion, in the case of Lake Ammersee, a decrease in nutrient input has led, most recently (1997– 2009), to a substantial improvement in the trophic state. This improvement is fundamentally a result of measures taken to correct any anthropogenic impact. Nevertheless, we show that the thermal stability of the lake reacts to climate-triggered alterations. Therefore it seems that the impact of recent climate change on trophic conditions will have to be monitored closely

中国中东部平原亚热带湿润区湖泊营养物生态分区

PDF HTML阅读 XML下载 导出引用 引用提醒 中国中东部平原亚热带湿润区湖泊营养物生态分区 DOI: 10.5846/stxb201011241668 作者: 作者单位: 中国科学院地理科学与资源研究所,北京;咸宁学院,中国科学院地理科学与资源研究所,北京,咸宁学院资源与环境科学学院,湖北咸宁 作者简介: 通讯作者: 中图分类号: 基金项目: 国家水体污染控制与治理科技重大专项(2009ZX07106-001-03, 2009ZX07106-001-07);国家科技支撑项目(2008BAC43B01) Lake nutrient ecosystems in the east-central moist subtropical plain of China Author: Affiliation: Institute of Geographical Sciences and Natural Resources Research,Chinese Academy of Science,Beijing,Institute of Geographical Sciences and Natural Resources Research,Chinese Academy of Science,Beijing,School of Resources Environment Science,Xianning College,Xianning,Hubei Province Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:湖泊营养物生态分区是实现湖泊分区控制的前提和基础。以中国中东部平原亚热带湿润区为案例区,根据区域特点,从自然地理要素、生态系统和人类活动三方面建立指标体系,对各指标进行归一化得到各指标数据的分值;采用AHP方法确定各指标的权重值,结合各指标分值计算栅格尺度上湖泊营养物生态分区综合评价分值;根据研究区域DEM数据划分小流域,将栅格尺度的湖泊营养物生态分区综合评价分值投影到小流域尺度上,采用双约束空间聚类算法对小流域尺度上湖泊营养物生态分区评价分值进行聚类得到湖泊营养物生态分区结果。结果表明:(1)AHP可以用来确定复杂指标体系中各指标的权重,适合用于确定湖泊营养物生态分区指标体系中各指标的权重;(2)采用双约束空间聚类进行湖泊营养物生态分区,保证了分区结果在空间上的连续性和评价分值上的接近性;(3)根据自然地理条件、土地利用和人类活动强度的不同,可以将中东部平原亚热带湿润区划分为长江中下游平原湖区、湘赣平原丘陵湖区、湘渝山地湖区、四川盆地湖区、川西-大巴山山地湖区5个营养物生态区。 Abstract:Our study objective was to investigate the factors creating spatial variation in lake nutrient concentrations, and the formation of ecological zones. Nutrient enrichment (eutrophication) has been observed in lakes in China, and it can be caused by multiple factors including physical, chemical, and biological factors. Ecological zoning of lakes according to nutrient concentration can be useful for the development and application of nutrient control standards and measures specific to each zone. We studied nutrients and the effects of nutrient concentrations in the eastern Lake Plain to aid in the development of control measures by the district government. We used an index based on three aspects: physical environment, ecological characteristics and human activities. Our study area was the east-central subtropical plains of China. The physical environment factors in the index, which were considered as most important for the ecological effects of nutrients, included annual precipitation, annual temperature, elevation, landform type, soil nitrogen and soil phosphorus content. Ecological characteristics that were included were the proportions of forest land, grassland, water area and unused land. In terms of human activities, we selected the proportions of developed land and cultivated land, and the specific proportion of GDP and population density. For each of the physical, ecological and human indices, we normalized the index data to obtain an index evaluation score. The analytic hierarchy process (AHP) method was used to determine the weight of each index and evaluate the importance of different scores in a matrix that made pairwise comparisons of the evaluation scores of each index. The watershed of the lake was divided into small partitions according to a digital elevation model and the total score on the grid scale was projected onto the small watershed partitions using dual-constrained spatial clustering. The results from the clustering analysis provide some preliminary results on the nutrient zonation within the lake. Based on these results, and the views of economic experts, the results of the initial partition appropriate adjustments, Case finally get the lakes nutrient ecoregion results. We suggest that AHP is a useful method that allows policymakers to develop rationales and engage in quantitative decision-making. Particularly for complex systems such as the lake nutrient system, AHP can be used to decide the relative importance of the multiple factors involved. Ecological zonation of lakes by nutrient concentration as revealed by the dual-constrained spatial clustering algorithm ensures spatial continuity and score proximity in the partition results. The spatial clustering analysis as applied to the two bound lake ecological zones of this paper can also be used in other regions or at a national scale to define the zonation in lakes. Using the nutrient level data from this study, the east-central subtropical plain of China can be divided into the middle and lower lake plains of the Yangtze River ecoregion, the hilly plains Lake ecoregion in Hunan and Jiangxi, the Hunan and Chongqing Mountain Lakes ecoregion, the Lakes Basin ecoregion, and in western Sichuan, the Daba Mountain Lakes ecoregion. 参考文献 相似文献 引证文献

Long-term changes in lake sediments and their infl uences on lake water quality in Japanese shallow lakes

In order to elucidate the nutrient dynamics in lakes with special reference to sediments, the changes in vertical distributions of sediment nutrients over 20 years were analyzed with the aid of sediment dating at the centers of two shallow, eutrophic lakes in Japan, i.e. Lakes Kasumigaura and Suwa. Peaks of 137 Cs and apparent density gave estimated sedimentation rates of around 1 and 2 kg m -2 y -1 in Lakes Kasumigaura and Suwa, respectively. Slight decreases of TP and TN contents (0.07 and 0.63 mg g -1 for TP and TN, respectively, in Lake Kasumigaura and 0.90 mg g -1 for TN in Lake Suwa) were observed by comparison between the cores obtained around 1980 and those of recent years except for a considerable decrease in TP in Lake Suwa (1.0 mg g -1 ). This decrease probably came from the higher percentage of easily releasable phosphorus in the past sediments of Lake Suwa. Using the TP and TN increases in lake waters during summer, the averaged nutrient release rates were estimated to be within the ranges of those observed by laboratory core experiments and by measuring the vertical profiles of interstitial concentrations except for a smaller estimation of TN in Lake Kasumigaura. On the other hand, the nutrient release rates were also determined using the long-term changes in sediment nutrient contents. The estimated rates were a little lower than the rates determined by the method using the increase in lake nutrient concentrations other than the higher ones for TP in Lake Suwa, which were originally based on the higher percentage of easily releasable phosphorus as mentioned above. Net sedimentation rates for 24 years in Lake Kasumigaura and those for 26 years in Lake Suwa calculated as the sum of new sedimentation and changes in old sediments during these periods were compared with the net input loads based on the per capita/exporting method. In the case ofTP, we observed a fairly good agreement because of its conservation, whereas the residuals were larger for TN due to denitrification in the overlying waters of sediments. The rates estimated from the imbalances in TN were in the ranges of the measured denitrification rates in laboratory tests with the sediments. Thus, the information on the long-term changes in sediment nutrients could provide the average rates of these fundamental processes in lake environments.