Effects of climate and nutrient load on the water quality of shallow lakes assessed through ensemble runs by PCLake
Nielsen, A. ; Trolle, D. ; Bjerring, R. - \ 2014
Ecological Applications 24 (2014)8. - ISSN 1051-0761 - p. 1926 - 1944.
ecosystem model pclake - danish lakes - phosphorus - state - eutrophication - restoration - equifinality - uncertainty - sensitivity - management
Complex ecological models are used to predict the consequences of anticipated future changes in climate and nutrient loading for lake water quality. These models may, however, suffer from nonuniqueness in that various sets of model parameter values may yield equally satisfactory representations of the system being modeled, but when applied in future scenarios these sets of values may divert considerably in their simulated outcomes. Compilation of an ensemble of model runs allows us to account for simulation variability arising from model parameter estimates. Thus, we propose a new approach for aquatic ecological models creating a more robust prediction of future water quality. We used our ensemble approach in an application of the widely used PCLake model for Danish shallow Lake Arreskov, which during the past two decades has demonstrated frequent shifts between turbid and clear water states. Despite marked variability, the span of our ensemble runs encapsulated 70–90% of the observed variation in lake water quality. The model exercise demonstrates that future warming and increased nutrient loading lead to lower probability of a clear water, vegetation-rich state and greater likelihood of cyanobacteria dominance. In a 6.0°C warming scenario, for instance, the current nutrient loading of nitrogen and phosphorus must be reduced by about 75% to maintain the present ecological state of Lake Arreskov, but even in a near-future 2.0°C warming scenario, a higher probability of a turbid, cyanobacteria-dominated state is predicted. As managers may wish to determine the probability of achieving a certain ecological state, our proposed ensemble approach facilitates new ways of communicating future stressor impacts.
Determinants of biodiversity in subtropical shallow lakes (Atlantic coast, Uruguay)
Kruk, C. ; Rodriguez-Gallego, L. ; Meerhoff, M. ; Quintans, F. ; Lacerot, G. ; Mazzeo, N. ; Scasso, F. ; Paggi, J.C. ; Peeters, E. ; Marten, S. - \ 2009
Freshwater Biology 54 (2009)12. - ISSN 0046-5070 - p. 2628 - 2641.
aquatic macrophyte richness - species richness - community structure - natural-waters - danish lakes - top-down - diversity - gradient - zooplankton - phosphorus
P> Shallow lakes and ponds contribute disproportionally to species richness relative to other aquatic ecosystems. In-lake conditions (e.g. presence of submerged plants) seem to play a key role in determining diversity, as has been demonstrated for temperate lakes. When water quality deteriorates and turbidity increases, conditions in such lakes are affected drastically resulting in a loss of diversity. However, it is not clear whether subtropical lakes show the same pattern and whether the richness of all groups reacts similarly to environmental changes. Our aim was to analyse the main factors explaining patterns of species richness in plankton, fish and submerged macrophyte assemblages in both turbid and clear subtropical shallow lakes. We analysed abiotic and biotic features of 18 subtropical, small- to medium-sized, shallow lakes along the Uruguayan coast. We compared both turbid and clear ecosystem states and evaluated the relative variance explained by the factors measured. Variables describing lake and catchment morphology, as well as the percentage of the water column occupied by submerged macrophytes (%PVI) and water turbidity, had strong effects on taxon richness. Interestingly, individual biotic groups had dissimilar richness patterns. Macrophyte %PVI decreased with increasing lake area, while fish species richness showed the opposite pattern. Phytoplankton species richness increased with macrophyte %PVI, while the zooplankton richness pattern varied depending on the taxonomic group considered. Overall, our results indicate that, as found for temperate lakes, a greater submerged plant cover promotes higher species richness in several groups, and that this may overwhelm the otherwise expected positive effect of lake size on species richness. On the other hand, small-bodied zooplankton predominated in lakes with high plant abundance. Our findings concur with recent studies, indicating that refuge capacity of aquatic plants might be weaker in (sub)tropical than in temperate shallow lakes. The extremely high plant cover, frequently observed in warm lakes, could potentially lead to different richness patterns in some groups. This conclusion has important consequences for local managers and conservationists.
Lake and watershed characteristics rather than climate influence nutrient limitation in shallow lakes
Kosten, S. ; Huszar, V.M. ; Mazzeo, N. ; Scheffer, M. ; Sternberg, L.S.L. ; Jeppesen, E. - \ 2009
Ecological Applications 19 (2009)7. - ISSN 1051-0761 - p. 1791 - 1804.
waterkwaliteit - voedingsstoffen - meren - stikstof - fosfor - cyanobacteriën - eutrofiëring - herstel - klimaat - zuid-amerika - primaire productie - water quality - nutrients - lakes - nitrogen - phosphorus - cyanobacteria - eutrophication - rehabilitation - climate - south america - primary production - phytoplankton community structure - fresh-water - meteoric precipitation - nitrogen-retention - subtropical lakes - trophic state - danish lakes - n-p - denitrification
Both nitrogen (N) and phosphorus (P) can limit primary production in shallow lakes, but it is still debated how the importance of N and P varies in time and space. We sampled 83 shallow lakes along a latitudinal gradient (5°–55° S) in South America and assessed the potential nutrient limitation using different methods including nutrient ratios in sediment, water, and seston, dissolved nutrient concentrations, and occurrence of N-fixing cyanobacteria. We found that local characteristics such as soil type and associated land use in the catchment, hydrology, and also the presence of abundant submerged macrophyte growth influenced N and P limitation. We found neither a consistent variation in nutrient limitation nor indications for a steady change in denitrification along the latitudinal gradient. Contrary to findings in other regions, we did not find a relationship between the occurrence of (N-fixing and non-N-fixing) cyanobacteria and the TN:TP ratio. We found N-fixing cyanobacteria (those with heterocysts) exclusively in lakes with dissolved inorganic nitrogen (DIN) concentrations of
Assessing ecological quality of shallow lakes: does knowledge of transparency suffice?
Peeters, E.T.H.M. ; Franken, R.J.M. ; Jeppesen, E. ; Moss, B. ; Bécares, E. ; Hansson, I. ; Romo, S. ; Kairesalo, T. ; Gross, E.M. ; Donk, E. van; Noges, T. ; Irvine, K. ; Kornijów, R. ; Scheffer, M. - \ 2009
Basic and Applied Ecology 10 (2009)1. - ISSN 1439-1791 - p. 89 - 96.
meren - eutrofiëring - deskundigen - waterbeheer - modellen - regressieanalyse - voorspelling - herstel - waterkwaliteit - eu regelingen - richtlijnen (directives) - kaderrichtlijn water - aquatische ecosystemen - lakes - eutrophication - experts - water management - models - regression analysis - prediction - rehabilitation - water quality - eu regulations - directives - water framework directive - aquatic ecosystems - hypertrophic lake - expert judgment - danish lakes - fish
The European Water Framework Directive (WFD) requires that all aquatic ecosystems in their member states should reach `good¿ ecological quality by 2015. To assess ecological quality, the WFD requires the definition of reference conditions using biological, physical and chemical indicators and the assignment of each water body to one of five quality classes using these indicators. Elaborate assessment schemes using large sets of variables are now being developed. Here we address the question whether all this is really needed and what the simplest assessment approach would be for the case of shallow lakes. We explore the relationships between the quality class assigned to a lake by experts in shallow lake ecology and a rich set of biological, physical, and chemical data. Multinomial logistic regression analyses were carried out based on data from 86 shallow lakes throughout Europe that were sampled in 2000 and/or 2001. Ecological quality of shallow lakes judged by experts was strongly correlated to physical and chemical variables associated with light regime and nutrients and much less to biological variables. Our regression model showed that ecological quality of this set of shallow lakes judged by experts could be predicted quite well from water transparency expressed as Secchi depth and that other variables did not contribute to it significantly. According to the WFD, lakes should at least have a `good¿ ecological quality. Quality judged by experts and predicted quality were similar for 78% of the lakes with respect to meeting this standard. As a cautionary note we stress that Secchi depth alone will be a less useful indicator if effects of stressors other than eutrophication (e.g. lake acidification and toxic pollution) are to be considered.
Lake restoration: successes, failures and long-term effects
Sondergaard, M. ; Jeppesen, E. ; Lauridsen, T.L. ; Skov, C. ; Nes, E.H. van; Roijackers, R.M.M. ; Lammens, E. ; Portielje, R. - \ 2007
Journal of Applied Ecology 44 (2007)6. - ISSN 0021-8901 - p. 1095 - 1105.
waterkwaliteit - herstel - meren - eutrofiëring - fosfor - effecten - aquatische ecologie - hydrobiologie - evaluatie - kaderrichtlijn water - nederland - denemarken - water quality - rehabilitation - lakes - eutrophication - phosphorus - effects - aquatic ecology - hydrobiology - evaluation - water framework directive - netherlands - denmark - nutrient loading reductions - shallow eutrophic lake - food-web manipulation - of-the-art - submerged macrophytes - danish lakes - planktivorous fish - temperate lakes - top-down - biomanipulation
1. Eutrophication constitutes a serious threat to many European lakes and many approaches have been used during the past 20–30 years to improve lake water quality. Results from the various lake restoration initiatives are diverse and the long-term effects are not well described. 2. In this study we evaluated data from more than 70 restoration projects conducted mainly in shallow, eutrophic lakes in Denmark and the Netherlands. Special focus was given to the removal of zooplanktivorous and benthivorous fish, by far the most common internal lake measure. 3. In more than half of the biomanipulation projects, Secchi depth increased and chlorophyll a decreased to less than 50% within the first few years. In some of the shallow lakes, total phosphorus and total nitrogen levels decreased considerably, indicating an increased retention or loss by denitrification. The strongest effects seemed to be obtained 4–6 years after the start of fish removal. 4. The long-term effect of restoration initiatives can only be described for a few lakes, but data from biomanipulated lakes indicate a return to a turbid state within 10 years or less in most cases. One of reasons for the lack of long-term effects may be internal phosphorus loading from a mobile pool accumulated in the sediment. 5. Synthesis and applications. Lake restoration, and in particular fish removal in shallow eutrophic lakes, has been widely used in Denmark and the Netherlands, where it has had marked effects on lake water quality in many lakes. Long-term effects ( > 8–10 years) are less obvious and a return to turbid conditions is often seen unless fish removal is repeated. Insufficient external loading reduction, internal phosphorus loading and absence of stable submerged macrophyte communities to stabilize the clear-water state are the most probable causes for this relapse to earlier conditions
Eutrophication constitutes a serious threat to many European lakes and many approaches have been used during the past 20-30 years to improve lake water quality. Results from the various lake restoration initiatives are diverse and the long-term effects are not well described. In this study we evaluated data from more than 70 restoration projects conducted mainly in shallow, eutrophic lakes in Denmark and the Netherlands. Special focus was given to the removal of zooplanktivorous and benthivorous fish, by far the most common internal lake measure. In more than half of the biomanipulation projects, Secchi depth increased and chlorophyll a decreased to less than 50% within the first few years. In some of the shallow lakes, total phosphorus and total nitrogen levels decreased considerably, indicating an increased retention or loss by denitrification. The strongest effects seemed to be obtained 4-6 years after the start of fish removal. The long-term effect of restoration initiatives can only be described for a few lakes, but data from biomanipulated lakes indicate a return to a turbid state within 10 years or less in most cases. One of reasons for the lack of long-term effects may be internal phosphorus loading from a mobile pool accumulated in the sediment. Synthesis and applications. Lake restoration, and in particular fish removal in shallow eutrophic lakes, has been widely used in Denmark and the Netherlands, where it has had marked effects on lake water quality in many lakes. Long-term effects (> 8-10 years) are less obvious and a return to turbid conditions is often seen unless fish removal is repeated. Insufficient external loading reduction, internal phosphorus loading and absence of stable submerged macrophyte communities to stabilize the clear-water state are the most probable causes for this relapse to earlier conditions.
The determination of ecological quality in shallow lakes - a tested system (EcoFrame) for implementation of the European Water Framework Directive
Moss, B. ; Stephen, D. ; Alvarez, C. ; Becares, E. ; Bunt, W. van de; Collings, S.E. ; Donk, E. van; Eyto, E. de; Feldmann, T. ; Fernandez-Alaez, C. ; Fernandez-Alaez, M. ; Franken, R.J.M. ; Carcia-Criado, F. ; Gross, E.M. ; Gyllstrom, M. ; Hansson, L. ; Irvine, K. ; Jarvalt, A. ; Jenssen, J.P. ; Jeppesen, E. ; Kairesalo, T. ; Kornijow, R. ; Krause, T. ; Kunnap, H. ; Laas, A. ; Lill, E. ; Lorens, B. ; Luup, H. ; Miracle, M. ; Noges, P. ; Noges, T. ; Nykannen, M. ; Ott, I. ; Peczula, W. ; Peeters, E.T.H.M. ; Phillips, G. ; Romo, S. ; Russell, V. ; Salujoe, J. ; Scheffer, M. ; Siewertsen, K. ; Smal, H. ; Tesch, C. ; Timm, H. ; Tuvikene, L. ; Tonno, I. ; Virro, T. ; Vicente, E. ; Wilson, D. - \ 2003
Aquatic conservation: marine and freshwater ecosystems 13 (2003)6. - ISSN 1052-7613 - p. 507 - 549.
phosphorus transfer-functions - trophic structure - temperate lakes - danish lakes - top-down - land-use - zooplankton - management - phytoplankton - conservation
1. The European Water Framework Directive requires the determination of ecological status in European fresh and saline waters. This is to be through the establishment of a typology of surface water bodies, the determination of reference (high status) conditions in each element (ecotype) of the typology and of lower grades of status (good, moderate, poor and bad) for each ecotype. It then requires classification of the status of the water bodies and their restoration to at least 'good status' in a specified period. 2. Though there are many methods for assessing water quality, none has the scope of that defined in the Directive. The provisions of the Directive require a wide range of variables to be measured and give only general guidance as to how systems of classification should be established. This raises issues of comparability across States and of the costs of making the determinations. 3. Using expert workshops and subsequent field testing, a practicable pan-European typology and classification system has been developed for shallow lakes, which can easily be extended to all lakes. It is parsimonious in its choice of determinands, but based on current limnological understanding and therefore as cost-effective as possible. 4. A core typology is described, which can be expanded easily in particular States to meet local conditions. The core includes 48 ecotypes across the entire European climate gradient and incorporates climate, lake area, geology of the catchment and conductivity. 5. The classification system is founded on a liberal interpretation of Annexes in the Directive and uses variables that are inexpensive to measure and ecologically relevant. The need for taxonomic expertise is minimized. 6. The scheme has been through eight iterations, two of which were tested in the field on tranches of 66 lakes. The final version, Version 8, is offered for operational testing and further refinement by statutory authorities. Copyright (C) 2003 John Wiley Sons, Ltd.