ArticlePublisher preview available

The influence of nutrient loading, climate and water depth on nitrogen and phosphorus loss in shallow lakes: a pan- European mesocosm experiment

DOI:10.1007/s10750-015-2505-9
Authors:
Jan Coppens at Flanders Environment Agency
Jan Coppens
Josef Hejzlar at Biology Centre CAS
Josef Hejzlar
Michal Šorf at Mendel University in Brno
Michal Šorf
Erik Jeppesen at Aarhus University
Erik Jeppesen
Show all 15 authorsHide
Read publisher preview
Download citation
To read the full-text of this research, you can request a copy directly from the authors.

Abstract and Figures

Losses of phosphorus (P) and nitrogen (N) have important influences on in-lake concentrations and nutrient loading to downstream ecosystems. We performed a series of mesocosm experiments along a latitudinal gradient from Sweden to Greece to investigate the factors influencing N and P loss under different climatic conditions. In six countries, a standardised mesocosm experiment with two water depths and two nutrient levels was conducted concurrently between May and November 2011. Our results showed external nutrient loading to be of key importance for N and P loss in all countries. Almost all dissolved inorganic nitrogen (DIN) and soluble reac-tive phosphorus (SRP) were lost or taken up in biomass in all mesocosms. We found no consistent effect of temperature on DIN and SRP loss but a significant, though weak, negative effect of temperature on total nitrogen (TN) and total phosphorus (TP) loss in the deeper mesocosms, probably related to higher organic N and P accumulation in the water in the warmer countries. In shallow mesocosms, a positive trend in TN and TP loss with increasing temperature was observed, most likely related to macrophyte growth.
Figures - available from: Hydrobiologia
This content is subject to copyright. Terms and conditions apply.
  • A preview of this full-text is provided by Springer Nature.
  • Learn more
Preview content only
Content available from Hydrobiologia
This content is subject to copyright. Terms and conditions apply.
SHALLOW LAKES
The influence of nutrient loading, climate and water depth
on nitrogen and phosphorus loss in shallow lakes: a pan-
European mesocosm experiment
Jan Coppens .Josef Hejzlar .Michal S
ˇorf .Erik Jeppesen .
S¸ eyda Erdog
˘an .Ulrike Scharfenberger .Aldoushy Mahdy .Peeter No
˜ges .
Arvo Tuvikene .Didier L. Baho .Cristina Trigal .Eva Papastergiadou .
Kostas Stefanidis .Saara Olsen .Meryem Bekliog
˘lu
Received: 24 August 2015 / Revised: 14 September 2015 / Accepted: 18 September 2015 / Published online: 27 October 2015
ÓSpringer International Publishing Switzerland 2015
Abstract Losses of phosphorus (P) and nitrogen
(N) have important influences on in-lake concentra-
tions and nutrient loading to downstream ecosystems.
We performed a series of mesocosm experiments
along a latitudinal gradient from Sweden to Greece to
investigate the factors influencing N and P loss under
different climatic conditions. In six countries, a
standardised mesocosm experiment with two water
depths and two nutrient levels was conducted concur-
rently between May and November 2011. Our results
showed external nutrient loading to be of key impor-
tance for N and P loss in all countries. Almost all
dissolved inorganic nitrogen (DIN) and soluble reac-
tive phosphorus (SRP) were lost or taken up in
biomass in all mesocosms. We found no consistent
effect of temperature on DIN and SRP loss but a
significant, though weak, negative effect of tempera-
ture on total nitrogen (TN) and total phosphorus (TP)
loss in the deeper mesocosms, probably related to
higher organic N and P accumulation in the water in
the warmer countries. In shallow mesocosms, a
positive trend in TN and TP loss with increasing
temperature was observed, most likely related to
macrophyte growth.
Keywords Nutrient retention Nutrient budget
Shallow lake Organic matter Temperature
Guest editors: M. Bekliog
˘lu, M. Meerhoff, T. A. Davidson,
K. A. Ger, K. E. Havens & B. Moss / Shallow Lakes in a
Fast Changing World
J. Coppens (&)S¸ . Erdog
˘an M. Bekliog
˘lu (&)
Limnology Laboratory, Department of Biology, Middle
East Technical University, Universiteler Mahallesi,
Dumlupinar Bulvarı, No. 1, 06800 Ankara, Turkey
e-mail: jan.coppens@metu.edu.tr
M. Bekliog
˘lu
e-mail: meryem@metu.edu.tr
J. Hejzlar M. S
ˇorf
Institute of Hydrobiology, Biology Centre of the Czech
Academy of Sciences, Na Sa
´dka
´ch 7,
370 05 Ceske Budejovice, Czech Republic
M. S
ˇorf
Faculty of Science, University of South Bohemia,
Branis
ˇovska
´31, 370 05 Ceske Budejovice, Czech
Republic
E. Jeppesen S. Olsen
Department of Bioscience, Aarhus University, Vejlsøvej
25, 8600 Silkeborg, Denmark
E. Jeppesen S. Olsen
Sino-Danish Centre for Education and Research, The
University of Chinese Academy of Sciences, Beijing,
China
S¸ . Erdog
˘an
Department of Biology, Faculty of Science and Art,
Bozok University, 66900 Yozgat, Turkey
U. Scharfenberger
Leibniz-Institute of Freshwater Ecology and Inland
Fisheries, Mu
¨ggelseedamm 310, 12587 Berlin, Germany
123
Hydrobiologia (2016) 778:13–32
DOI 10.1007/s10750-015-2505-9
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... Both %R TN and %R DIN correlate positively with the water residence time (τ) and negatively with the mean depth of the water column (Z ) (Molot and Dillon, 1993). τ and Z affect the duration and the extent of the contact between the water column and the sediment surface influencing the N uptake by the sediment (Coppens et al., 2015). ...
... Some of these relations have been used to make predictions of N retention rates at regional and global scales Beusen et al., 2016;Harrison et al., 2009;Seitzinger et al., 2010;Wollheim et al., 2008). Several studies suggested that parameters other than τ and Z may significantly influence the proportion of N retained in lakes: in-lake concentration of P (Berge et al., 1997;Coppens et al., 2015;Kaste and Lyche-Solheim, 2005) and nitrate (Mulholland et al., 2008), the TN:TP ratio (Guildford and Hecky, 2000), temperature (Coppens et al., 2015;Rissanen et al., 2013), the presence of organic matter and the quality of the N loads (i.e. less easily recyclable inorganic N; Rissanen et al., 2013). ...
... Some of these relations have been used to make predictions of N retention rates at regional and global scales Beusen et al., 2016;Harrison et al., 2009;Seitzinger et al., 2010;Wollheim et al., 2008). Several studies suggested that parameters other than τ and Z may significantly influence the proportion of N retained in lakes: in-lake concentration of P (Berge et al., 1997;Coppens et al., 2015;Kaste and Lyche-Solheim, 2005) and nitrate (Mulholland et al., 2008), the TN:TP ratio (Guildford and Hecky, 2000), temperature (Coppens et al., 2015;Rissanen et al., 2013), the presence of organic matter and the quality of the N loads (i.e. less easily recyclable inorganic N; Rissanen et al., 2013). ...
Improved empirical models for predicting nitrogen retention in lakes and reservoirs
Article
Anthropogenic activities have significantly increased the movement of nitrogen (N) from land to freshwaters and to coastal waters and have led to severe environmental consequences. The flow of N is moderated by retention processes in terrestrial, freshwater and marine ecosystems. Freshwater ecosystems have the highest areal N retention rates. The proportion of N retained in aquatic ecosystems depends on the areal hydraulic load and is described by relatively simple semi-empirical or strictly empirical models. Here I compared the predictive power of several models, that predict the annual mean proportion of total N (TN) and dissolved inorganic N (DIN) retained in lakes and reservoirs and developed an improved version of the models currently in use by inclusion of additional relevant parameters. The study shows that models derived from mass balances describing the proportion of annual mean retention of TN and DIN as a sigmoid function of the areal hydraulic load can be approximated by a linear function on the logarithm of the areal hydraulic load. Stepwise multiple linear regression analyses identified the logarithm of the areal hydraulic load as the main explanatory variable for the proportion of retained TN, followed by the ratio between the DIN and the TN load and the ratio between in-lake concentrations of TN and total phosphorus (TP). The logarithm of the areal hydraulic load, the ratio between the DIN and the TN load and the logarithm of the in-lake concentration of TP explained the largest proportion of retained DIN. Addition of the second and third explanatory variable decreased the normalized root mean square deviation between the observed and predicted proportion of retained TN from 37%, to 31% and to 30% and between the observed and predicted proportion of retained DIN from 39%, to 35% and to 32%.
View
... Nutrient conditions were experimentally manipulated in the water layer, the sediment, or in both the water and sediment, as in eutrophicated water bodies nutrient enrichment may result from external loading in the water column (Coppens et al. 2016), internal loading from the sediment (Fisher et al. 2005, Immers et al. 2015 or both. We tested how this affected plant growth, stoichiometry and subsequent palatability to the generalist consumer Lymnaea stagnalis (Gastropoda). ...
... The two external nutrient loading treatments were with external nutrient loading to the water layer (W1), and without external nutrient loading to the water layer (W0). The nutrient solution was made by dissolving NH4NO3 and KH2PO4 powder into demi water, and its addition simulated a highlevel nutrient loading of 0.5 mg L -1 Nitrogen (N) and 0.05 mg L -1 Phosphorus (P) per week, the dosing level and ratio followed those of experiments in Sagrario et al. (2005), Jeppesen et al. (2007) and Coppens et al. (2016). In order to prevent that the plants would be outcompeted by phytoplankton at the start of the experiment, the treatment of nutrient loading to the water started half way (after four weeks) of the culturing and was applied four times during the experiment. ...
View
... We cultured the plants at three different water temperatures (20, 24, and 28°C) and four distinct nutrient conditions (nutrient-poor and nutrient-rich sediments, with and without external nutrient loading) in a full-factorial design. Nutrient conditions were experimentally manipulated in the water column, the sediment, or both, because nutrient enrichment in eutrophic water bodies can result from external loading into the water column (Coppens et al., 2016), internal loading from the sediment (Fisher et al., 2005;Immers et al., 2015), or a combination thereof. We also monitored nutrient availability for the plants, and the development of competing primary producers (e.g. ...
... Nutrients were added weekly, simulating a high-level nutrient loading of 0.5 mg L −1 N and 0.05 mg L −1 P per week. The dosing level and ratio followed those of experiments in Sagrario et al. (2005); Jeppesen et al. (2007) and Coppens et al. (2016). These nutrient treatments are in the suitable range of the growth of the plant, as only high ammonia concentrations (> 5 mg L −1 ) can have toxic effects on the growth of submerged plants (Cao et al., 2004;Yu et al., 2015). ...
Interactive Effects of Rising Temperature and Nutrient Enrichment on Aquatic Plant Growth, Stoichiometry, and Palatability
Article
Full-text available
  • Feb 2020
The abundance and stoichiometry of aquatic plants are crucial for nutrient cycling and energy transfer in aquatic ecosystems. However, the interactive effects of multiple global environmental changes, including temperature rise and eutrophication, on aquatic plant stoichiometry and palatability remain largely unknown. Here, we hypothesized that (1) plant growth rates increase faster with rising temperature in nutrient-rich than nutrient-poor sediments; (2) plant carbon (C): nutrient ratios [nitrogen (N) and phosphorus (P)] respond differently to rising temperatures at contrasting nutrient conditions of the sediment; (3) external nutrient loading to the water column limits the growth of plants and decreases plant C:nutrient ratios; and that (4) changes in plant stoichiometry affect plant palatability. We used the common rooted submerged plant Vallisneria spiralis as a model species to test the effects of temperature and nutrient availability in both the sediment and the water column on plant growth and stoichiometry in a full-factorial experiment. The results confirmed that plants grew faster in nutrient-rich than nutrient-poor sediments with rising temperature, whereas external nutrient loading decreased the growth of plants due to competition by algae. The plant C: N and C: P ratios responded differently at different nutrient conditions to rising temperature. Rising temperature increased the metabolic rates of organisms, increased the nutrient availability in the sediment and enhanced plant growth. Plant growth was limited by a shortage of N in the nutrient-poor sediment and in the treatment with external nutrient loading to the water column, as a consequence, the limited plant growth caused an accumulation of P in the plants. Therefore, the effects of temperature on aquatic plant C:nutrient ratios did not only depend on the availability of the specific nutrients in the environment, but also on plant growth, which could result in either increased, unaltered or decreased plant C:nutrient ratios in response to temperature rise. Plant feeding trial assays with the generalist consumer Lymnaea stagnalis (Gastropoda) did not show effects of temperature or nutrient treatments on plant consumption rates. Overall, our results implicate that warming and Frontiers in Plant Science | www.frontiersin.org
View
... There were 12 treatments in total and four replicates for each treatment, and all treatments were randomly assigned to the 48 mesocosms. Doses of 0.5 mg L −1 N (NaNO 3 ) and 0.05 mg L −1 P (KH 2 PO 4 ) were added weekly to the selected mesocosms to simulate eutrophication (E), similar to those used in previous studies (Coppens et al., 2016;Jeppesen et al., 2007). W and H treatments were achieved by a computer-controlled temperature system with two digital temperature sensors (DS18B20, Risym, China) and a heating element (600 W in power) in each mesocosm. ...
Stoichiometric stability of aquatic organisms increases with trophic level under warming and eutrophication
Article
The balance of stoichiometric traits of organisms is crucial for nutrient cycling and energy flow in ecosystems. However, the impacts of different drivers on stoichiometric (carbon, C; nitrogen, N; and phosphorus, P) variations of organisms have not been well addressed. In order to understand how stoichiometric traits vary across trophic levels under different environmental stressors, we performed a mesocosm experiment to explore the impacts of warming (including +3 °C consistent warming above ambient and heat waves ranging from 0 to 6 °C), eutrophication, herbicide and their interactions on stoichiometric traits of organisms at different trophic levels, which was quantified by stable nitrogen isotopes. Results showed that herbicide treatment had no significant impacts on all stochiometric traits, while warming and eutrophication significantly affected the stoichiometric traits of organisms at lower trophic levels. Eutrophication increased nutrient contents and decreased C: nutrient ratios in primary producers, while the response of N:P ratios depended on the taxonomic group. The contribution of temperature treatments to stoichiometric variation was less than that of eutrophication. Heat waves counteracted the impacts of eutrophication, which was different from the effects of continuous warming, indicating that eutrophication impacts on organism stoichiometric traits depended on climate scenarios. Compared to environmental drivers, taxonomic group was the dominant driver that determined the variations of stoichiometric traits. Furthermore, the stoichiometric stability of organisms was strongly positively correlated with their trophic levels. Our results demonstrate that warming and eutrophication might substantially alter the stoichiometric traits of lower trophic levels, thus impairing the nutrient transfer to higher trophic level, which might further change the structure of food webs and functions of the ecosystems.
View
... We applied a crossed design of three temperature scenarios (C: ambient; W: continuous warming by +3 • C; H: warming with multiple heatwaves), and four pollution levels (control, nitrogen and phosphorus addition, glyphosate addition, and a combination of nutrient and herbicide addition), resulting in a total of 12 treatments with four replicates each, and all treatments were randomly assigned to the 48 mesocosms. Doses of 0.5 mg/LN (NaNO 3 ) and 0.05 mg/LP (KH 2 PO 4 ) were added weekly to the selected mesocosms to simulate nutrient loading, similar to those used in previous studies (Coppens et al. 2016;Jeppesen et al. 2007). Warming (W) and heat wave (H) treatments were achieved by a computer-controlled temperature system with two digital temperature sensors (DS18B20) and a heating element (600 W in power) in each mesocosm. ...
Heat waves rather than continuous warming exacerbate impacts of nutrient loading and herbicides on aquatic ecosystems
Article
Full-text available
Submerged macrophytes are vital components in shallow aquatic ecosystems, but their abundances have declined globally. Shading by periphyton and phytoplankton/turbidity plays a major role in this decline, and the competing aquatic primary producers are subject to the complex influence of multiple stressors such as increasing temperatures, nutrient loading and herbicides. Their joint impact has rarely been tested and is difficult to predict due to potentially opposing effects on the different primary producers, their interactions and their grazers. Here, we used 48 mesocosms (2500 L) to simulate shallow lakes dominated by two typical submerged macrophytes, bottom-dwelling Vallisneria denseserrulata and canopy-forming Hydrilla verticillata, and associated food web components. We applied a combination of nutrient loading, continuous warming, heat waves and glyphosate-based herbicides to test how these stressors interactively impact the growth of submerged macrophytes, phytoplankton and periphyton as competing primary producers. Warming or heat waves alone did not affect phytoplankton and periphyton abundance, but negatively influenced the biomass of V. denseserrulata. Nutrient loading alone increased phytoplankton biomass and water turbidity and thus negatively affected submerged macrophyte biomass, particularly for V. denseserrulata, by shading. Glyphosate alone did not affect biomass of each primary producer under ambient temperatures. However, heat waves facilitated phytoplankton growth under combined nutrient loading and glyphosate treatments more than continuous warming. As a consequence, H. verticillata biomass was lowest under these conditions indicating the potential of multiple stressors for macrophyte decline. Our study demonstrated that multiple stressors interactively alter the biomass of primary producers and their interactions and can eventually lead to a loss of macrophyte communities and shift to phytoplankton dominance. These results show the risks in shallow lakes and ponds in agricultural landscapes and underline the need for multiple stressor studies as a base for their future management.
View
... The nutrient solution used for the nutrient loading treatment (E1) was made by dissolving NaNO 3 and KH 2 PO 4 salts in demineralized water. Nutrients were added once a month to these E1 containers, simulating a high-level nutrient loading of 2 mg L −1 N and 0.2 mg L −1 P, a eutrophic state, in the range of concentration and ratio of earlier experiments by Coppens et al. (2016) and Jeppesen et al. (2007). For the herbivory treatment, adult snails (n = 5, size ranged from 1 to 3 cm) were added to each herbivory treatment container (H1), a density of snails similar to natural lakes around the Yangtze River (Wang, Pan, et al., 2010), and no extra snails were added to the rest of the containers (H0). ...
Interactive effects of light and snail herbivory rather than nutrient loading determine early establishment of submerged macrophytes
Article
Full-text available
  • Jul 2022
Submerged macrophytes play a key role in maintaining a clear‐water phase and promoting biodiversity in shallow aquatic ecosystems. Since their abundance has declined globally due to anthropogenic activities, it is important to include them in aquatic ecosystem restoration programs. Macrophytes establishment in early spring is crucial for the subsequent growth of other warm‐adapted macrophytes. However, factors affecting this early establishment of submerged macrophytes have not been fully explored yet. Here, we conducted an outdoor experiment from winter to early spring using the submerged macrophytes Potamogeton crispus and Vallisneria spinulosa to study the effects of shading, nutrient loading, snail herbivory (Radix swinhoei), and their interactions on the early growth and stoichiometric characteristics of macrophytes. The results show that the effects strongly depend on macrophyte species. Biomass and number of shoots of P. crispus decreased, and internode length increased during low light conditions, but were not affected by nutrient loading. P. crispus shoot biomass and number showed hump‐shaped responses to increased snail biomass under full light. In contrast, the biomass of the plant linearly decreased with snail biomass under low light. This indicates an interaction of light with snail herbivory. Since snails prefer grazing on periphyton over macrophytes, a low density of snails promoted growth of P. crispus by removing periphyton competition, while herbivory on the macrophyte increased during a high density of snails. The growth of V. spinulosa was not affected by any of the factors, probably because of growth limitation by low temperature. Our study demonstrates that the interaction of light with snail herbivory may affect establishment and growth of submerged macrophytes in early spring. Macrophyte restoration projects may thus benefit from lowering water levels to increase light availability and making smart use of cold‐adapted herbivores to reduce light competition with periphyton. Our study demonstrates that the interactions of light with snail herbivory, but not nutrient loading, may affect establishment and growth of submerged macrophytes in early spring. Our study thus has implications for recovery of submerged macrophytes in deteriorative water bodies.
View
... These two aspects of light availability are particularly critical at the beginning of the growing season for short-growing plants but also for tall-growing ones because MAL is likely decisive for whether the entire water volume can be used for efficient photosynthesis and the formation of dense macrophyte stands (Chen et al., 2016;Lauridsen, Mønster, Raundrup, Nymand, & Olesen, 2020). Empirical evidence from various climate regions including subtropical (Havens, East, & Beaver, | 3 ERSOY Et al. Bucak et al., 2012;Coppens, Özen, et al., 2016;Özkan, Jeppesen, Johansson, & Beklioğlu, 2010) confirms a positive effect of a water level decline on submerged macrophyte growth due to improved light conditions in the water column and expansion of the littoral zone (Beklioğlu et al., 2006;Beklioğlu & Tan, 2008;Coppens, Hejzlar, et al., 2016;Kosten et al., 2009;Stefanidis & Papastergiadou, 2013). ...
Impact of nutrients and water level changes on submerged macrophytes along a temperature gradient: a Pan-European mesocosm experiment
Article
Full-text available
Submerged macrophytes are of key importance for the structure and functioning of shallow lakes and can be decisive for maintaining them in a clear water state. The ongoing climate change affects the macrophytes through changes in temperature and precipitation, causing variations in nutrient load, water level and light availability. To investigate how these factors jointly determine macrophyte dominance and growth, we conducted a highly standardised pan-European experiment involving the installation of mesocosms in lakes. The experimental design consisted of mesotrophic and eutrophic nutrient conditions at 1 m (shallow) and 2 m (deep) depth along a latitudinal temperature gradient with average water temperatures ranging from 14.9 to 23.9 °C (Sweden to Greece) and a natural drop in water levels in the warmest countries (Greece and Turkey). We determined Percent Plant Volume Inhabited (PVI) of submerged macrophytes on a monthly basis for five months and dry weight at the end of the experiment. Over the temperature gradient, PVI was highest in the shallow mesotrophic mesocosms followed by intermediate levels in the shallow eutrophic and deep mesotrophic mesocosms, and lowest levels in the deep eutrophic mesocosms. We identified three pathways along which water temperature likely affected PVI, exhibiting: (1) a direct positive effect if light was not limiting, (2) an indirect positive effect due to an evaporation driven water level reduction, causing a non-linear increase in mean available light, (3) an indirect negative effect through algal growth and, thus, high light attenuation under eutrophic conditions. We conclude that high temperatures combined with a temperature-mediated water level decrease can counterbalance the negative effects of eutrophic conditions on macrophytes by enhancing the light availability. While a water level reduction can promote macrophyte dominance, an extreme reduction will likely decrease macrophyte biomass and, consequently, their capacity to function as a carbon store and food source.
View
Integration of pen aquaculture into ecosystem-based enhancement of small-scale fisheries in a macrophyte dominated floodplain wetland of India
Article
Full-text available
The rapid degradation, overexploitation, and encroachment of floodplain wetlands have led to considerable decline in fish diversity and production from these invaluable aquatic resources threatening livelihood of the dependent fishers. The climate change evident in the fast few decades has further aggravated the problem of eutrophication causing water stress and sedimentation leading to rampant macrophyte proliferation affecting ecological and economic functioning of these ecosystems. Macrophyte control and management needs serious attention for sustaining ecosystem services provided by these resources. In this direction, pen culture of grass carp Ctenopharyngodon idella as a biocontrol for macrophytes along with Indian major carps was implemented in a co-management mode in Beledanga, a typical floodplain wetland, a gradually shrinking, macrophyte dominated floodplain wetland in lower Ganga basin. Indian major carps Labeo catla (6.28±0.23g), Labeo rohita (5.1±0.12g), Cirrhinus mrigala (3.5±0.08g) were stocked in the ratio 4:3:3 at the rate of 20 Nos.m⁻² in pens (0.1ha each) in triplicate. Grass carp (7.1±0.42g) was stocked in pen at the rate of 20Nos.m⁻² in duplicate. The fishes were fed with pelleted feed twice a day at the rate of 2–3% of body weight. The seed was overwintered in pens for a period of 90 days from November 2019 to January 2020. Average weight recorded at the end of culture period was 25.13±1.70g, 18.11±0.63g, 14.53±0.87g, and 39.20±1.90g in L. catla, L. rohita, C. mrigala, and C. idella, respectively. The survival of fish ranged from 70 to 81%. Growth performance and feed utilization efficiency of grass carp were significantly higher (p<0.05) compared to other carp species. The pen culture was found to be economically viable with a benefit cost ratio of 1.53. The fishes produced were released back into the open wetland as an additional input for culture-based fisheries. The intervention along with niche-based enhanced stocking led to 24% increase in the fish production from the wetland with grass carp contributing 20–22% of the total catch with 32% increase in revenue generated by the sale of fish within a short span of 1 year. The study successfully demonstrated technological suitability and economic feasibility of pen culture in this wetland and role of grass carp as a potential biocontrol species for macrophyte management. Grass carp stocked in open wetland grew to 0.8 to 1kg within 6 months and 2–2.3kg within a year and could utilize 40–45% of the submerged and emergent macrophytes. Integration and optimization of grass carp will not only aid in habitat management of macrophyte-choked wetlands but will also boost their small-scale fisheries by converting standing macrophyte biomass into protein-rich fish biomass. The enhanced production will also cater to nutritional and livelihood security of the dependent fishers.
View
Effects of a microplastic mixture differ across trophic levels and taxa in a freshwater food web: In situ mesocosm experiment
Article
The ubiquitous presence of microplastics (MP) in aquatic ecosystems can affect organisms and communities in multiple ways. While MP research on aquatic organisms has primarily focused on marine ecosystems and laboratory experiments, the community-level effects of MP in freshwaters, especially in lakes, are poorly understood. To examine the impact of MP on freshwater lake ecosystems, we conducted the first in situ community-level mesocosm experiment testing the effects of MP on a model food web with zooplankton as main herbivores, odonate larvae as predators, and chironomid larvae as detritivores for seven weeks. The mesocosms were exposed to a mixture of the most abundant MP polymers found in freshwaters, added at two different concentrations in a single pulse to the water surface, water column and sediment. Water column MP concentrations declined sharply during the first two weeks of the experiment. Contrary to expectations, MP ingestion by zooplankton was low and limited mainly to large-bodied Daphnia, causing a decrease in biomass. Biomass of the other zooplankton taxa did not decrease. Presence of MP in the faecal pellets of odonate larvae that fed on zooplankton was indicative of a trophic transfer of MP. The results demonstrated that MP ingestion varies predictably with MP size, as well as body size and feeding preference of the organism, which can be used to predict the rates of transfer and further effects of MP on freshwater food webs. For chironomids, MP had only a low, short-term impact on emergence patterns while their wing morphology was significantly changed. Overall, the impact of MP exposure on the experimental food web and cross-ecosystem biomass transfer was lower than expected, but the experiment provided the first in situ observation of MP transfer to terrestrial ecosystems by emerging chironomids.
View
Is There a Pattern for Occurrence of Macrophytes in Polish Ponds?
Article
Full-text available
  • Aug 2019
Although ponds are common elements in the environment, dependences occurring in these ecosystems have not been fully investigated. Our study focuses on the correlation between environmental factors and changes occurring in ponds—mostly the distribution of macrophytes in space and time. The aim of our analyses was to indicate which physicochemical variables were characteristic of ponds in specific habitats (forest, agriculture field, and village) and whether they could associate the distribution of vegetation in these ponds. Thirteen ponds differing in morphometric parameters and location in landscape (ponds located in agriculture fields, forests, and villages) were analyzed. Our research was based on data covering a period of 10 years (2008–2018). The following parameters were analyzed: the water content of NH4+, NO3−, NO2−, TP, PO43−, Na, K, Mg, Ca, and Fe, pH, temperature and morphometric parameters. Macrophytes were observed during the growing season in July 2008, 2010, 2012, 2014, 2016 and 2018. Three homogeneous species groups were distinguished in statistical analyses and the dominance of selective environmental factors was assigned to them. The first group consisted of indicator species for forest ponds. Their waters were characterized by a low content of Ca, Mg, and Na as well as an increased content of NH4+ and Fe. The second group was composed of indicator species for field ponds, where the highest NO3− concentrations were found. The third group was formed by indicator species for village ponds. Water of these ponds was characterized by higher concentration levels of K, Na, and total P.
View
Human Influences on Nitrogen Removal in Lakes
Article
Full-text available
Unlucky Lakes The negative consequences of increased loading of nitrogen and phosphorus into aquatic ecosystems are well known. Management strategies aimed at reducing the sources of these excess nutrients, such as fertilizer runoff or sewage outflows, can largely mitigate the increases in nitrogen and phosphorus levels; however, it is unclear if these strategies are influencing other spects of these ecosystems. Using a global lake data set, Finlay et al. (p. 247 ; see the Perspective by Bernhardt ) found that reducing phosphorus inputs reduced a lake's ability to export reactive nitrogen, exacerbating nitrate pollution.
View
Shallow lake restoration by nutrient loading reduction—some recent findings and challenges ahead
Article
  • Jun 2007
Shallow lakes respond to nutrient loading reductions. Major findings in a recent multi-lake comparison of data from lakes with long time series revealed: that a new state of equilibrium was typically reached for phosphorus (P) after 10–15 years and for nitrogen (N) after <5–10 years; that the in-lake Total N:Total P and inorganic N:P ratios increased; that the phytoplankton and fish biomass often decreased; that the percentage of piscivores often increased as did the zooplankton:phytoplankton biomass ratio, the contribution of Daphnia to zooplankto biomass, and cladoceran size. This indicates that enhanced resource and predator control often interact during recovery from eutrophication. So far, focus has been directed at reducing external loading of P. However, one experimental study and cross-system analyses of data from many lakes in north temperate lakes indicate that nitrogen may play a more significant role for abundance and species richness of submerged plants than usually anticipated when total phosphorus is moderate high. According to the alternative states hypothesis we should expect ecological resistance to nutrient loading reduction and P hysteresis. We present results suggesting that the two alternative states are less stable than originally anticipated. How global warming affects the water clarity of shallow lakes is debatable. We suggest that water clarity often will decrease due to either enhanced growth of phytoplankton or, if submerged macrophytes are stimulated, by reduced capacity of these plants to maintain clear-water conditions. The latter is supported by a cross-system comparison of lakes in Florida and Denmark. The proportion of small fish might increase and we might see higher aggregation of fish within the vegetation (leading to loss of zooplankton refuges), more annual fish cohorts, more omnivorous feeding by fish and less specialist piscivory. Moreover, lakes may have prolonged growth seasons with a higher risk of long-lasting algal blooms and at places dense floating plant communities. The effects of global warming need to be taken into consideration by lake managers when setting future targets for critical loading, as these may well have to be adjusted in the future. Finally, we highlight some of the future challenges we see in lake restoration research.
View
View
View
View
View
View
View
Factors influencing nitrogen processing in lakes: An experimental approach
Article
1. To help improve our understanding of the nitrogen cycle in lakes, particularly in the context of climate change, we analysed total nitrogen (TN) and nitrate (NO À 3 -N) data from six mesocosm experi-ments (in Denmark, U.K., China and Turkey) covering different climatic regions. We assessed the effects of nitrogen (N) and phosphorus (P) loading, temperature, salinity and water level on N processing. 2. Water column N loss (defined as the nitrogen processed in and lost from the water column in units of net amount processed per unit area and per unit of time, or in relative terms as the percentage loss of the total pool in 2 weeks) was particularly sensitive to external nutrient loading to the mesocosms. Mean water column TN loss at high N loading varied from 111 to 250 mg m À2 day À1 and increased with N loading. High P loading resulted in increased water column N loss, possibly because of increased uptake into plants and attached algae and sedimentation of the increased algal crop. High salinity generally decreased water column TN loss; on average, 10% more TN was in the water column at 12& salinity than at 2& salinity, while no significant effect of water level was found. 3. Only weak relationships were observed between N processing and temperature, and mesocosms limited by P accumulated more nitrogen in their water columns than those with high P loadings. Our results suggest that N processing in lakes appears to be more sensitive to features of the catchment, such as hydrology and loading, than to climatic effects related to temperature, salinity and water level.
View
Climate change effects on shallow lakes: Design and preliminary results of a cross-European climate gradient mesocosm experiment
Article
  • Jun 2014
Climate change is expected to profoundly affect both temperature and net precipitation, with implications for lake water level. We describe the design of a harmonized, simultaneous, cross-European mesocosm experiment to elucidate the effects of climate change on community structure, functioning, and metabolism in shallow lakes at low and high nutrient levels with contrasting depths (1 and 2 m). We used cylindrical (D = 1.2 m) tanks that were either 1.2 or 2.2 m high, each having a 10-cm sediment layer. We inoculated the mesocosms with a mixed sample of sediment and plankton from lakes with contrasting nutrient concentrations and added macrophytes and planktivorous fish. Sediment was pre-equilibrated to the required experimental nutrient concentration. During the experiment the water level decreased with increasing temperature (up to 90 cm in the Mediterranean mesocosms) while conductivity increased. The average chlorophyll a concentration increased with temperature in the deep mesocosms but was more variable in the shallow mesocosms. Macrophyte
View