Ecological effects of water-level fluctuations in lakes. The impact of water-level regulation on littoral macroinvertebrate assemblages in boreal lakes Jukka Aroviita , Heikki O. References Publications referenced by this paper.
Importance of Long-Term Cycles for Predicting Water Level Dynamics in Natural Lakes
Diversity of invertebrate fauna in littoral of shallow Myczkowce dam reservoir in comparison with a deep Solina dam reservoir T. Blackwell , Oxford. C Valdovinos. Restoring ecological integrity of great rivers: historical hydrographs aid in defining reference conditions for the Missouri River David L. Galat , Robin Lipkin. This emphasizes the importance of including detailed vertical sampling in metabolic studies of water bodies, an approach that has been overlooked in many studies See Table 4.
Besides providing insight into vertical changes themselves, detailed vertical measurement of production and respiration rates is important in obtaining realistic and representative area-based integrations, useful for assessing exchange fluxes of water bodies with the atmosphere and sediments Valdespino-Castillo et al. We estimate that integrated rates can be biased by up to one order of magnitude when based on single-depth measurements. Systems are ordered by mean value of GPP. Zpl, depth of the production layer. Dash — indicates when the number of sampled levels, or the depth of the production layer, where not specified by the authors.
Means and P:R were calculated from the original data when not reported and converted from O 2 to C units when necessary. In VB, the vertical variation of metabolic rates was closely coupled to the vertical changes in limnological parameters and processes. The sharp decrease of production within a few meters is likely caused by the sharp decrease in light availability in this ecosystem where Secchi depth is on average only 1.
The separation between the depths of these two layers allows the existence of a broad aerobic respiration layer in VB, in which there is not enough light for photosynthesis, but there is still oxygen that is supplied by the mixing processes of the surface layer.
During the stratification months, this respiration layer is in the deeper half of the epilimnion, but during circulation periods it extends all the way to the reservoir bottom Figs. It is notable that the respiration in this layer outbalances the otherwise autotrophic production layer of this highly eutrophic system. Although data on the organic matter content of the water column of VB have not been published, using the dissolved organic nitrogen measurements done by Barjau-Aguilar , we estimate the mean DOC to have been 7.
Such an amount of organic matter is probably a factor in the oxygen under-saturation found in VB during the circulation periods. The vertical distribution of temperature in VB found during — confirms the continuity of a monomictic behavior of the reservoir, as found before Merino-Ibarra et al.
Hypolimnetic temperatures increased in VB during each stratification period during —, confirming the persistence of this trend in VB during the stratification, as reported for previous years Merino-Ibarra et al. Maximum temperatures in the hypolimnion occurred during the stratification periods when the water level of the reservoir was lowest i.
Additionally, the — time series here described also shows the interannual variability of temperature in VB, particularly during the circulation periods, when the full water column is affected by heat exchange through the surface, and the water temperature is likely to be directly related to the coldness of each winter. Oxygen vertical distribution was consistent with the temperature distribution and the monomictic behavior confirmed for VB during the decade sampled.
The mainly anoxic hypolimnions Fig. Secchi depth was also a simple but very useful tool to extend the assessment of the vertical range of production Z pl throughout the full sampled period Fig. Hence, the use of Secchi depth to estimate Z pl can be a useful tool to manage large datasets containing vertical assessments of GPP and R , and to improve their yield of integrated rates. It is notable that among the metabolic studies in tropical lakes or reservoirs summarized in Table 4 , fewer than half report on the measurement of metabolism at multiple water depths, and only one in four reports on the determination of the depth of the production layer.
This demonstrates the need for studies that deal in detail with vertical variations of the metabolic rates and therefore offer reliable integrated rates. Although temperature is the ultimate driver of metabolic rates at organism level, at the ecosystem scale its effect can be hindered by the many other changes that can occur simultaneously. In particular, unlike marine systems, cf. Downing, , monomictic inland systems exhibit contrasting physicochemical conditions coupled to the seasonal variations of temperature, which are mainly dependent on the variable intensity and spatial extent of mixing processes.
All of these processes and conditions can affect production and respiration rates, hindering the effect of concomitant temperature changes. This apparently was the case in the initial assessment of Valdespino-Castillo et al. In contrast, the long-term data now reported reveal a positive correlation of respiration with temperature when circulation and stratification periods were analyzed separately.
In the case of the circulations, having data from a series of years allowed enough thermal variability to reveal the expected direct effect of temperature on metabolic rates, and particularly on respiration. Additionally, this expected correlation could also be identified in the case of the stratifications within the lower part of the epilimnion Fig. Because of the wide water-level fluctuations in VB during —, this data set allowed assessment of the effects of these variations, parameterized here as RLLF.
In turn, it has also been shown by Valeriano-Riveros et al. This would mean that water-level fluctuations could affect the food web through changes in mixing. Hence, the impact of water-level fluctuations on metabolic rates likely involves its effect over multiple processes, including mixing itself, changes in the planktonic food web and an increase in nutrient availability to the surface layer.
In our — metabolic data set, where ten stratifications with different water levels could now be compared, both Secchi depth and GPP decreased significantly as a function of the RLLF. The decrease of Secchi depth could be due to the increase in nutrient supply to the surface layer through hypolimnetic entrainment and boundary mixing, where nutrients might be limiting the expansion of phytoplankton. That there may be a certain degree of nitrogen limitation during the stratification in VB was suggested by Valeriano-Riveros et al.
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Another process that could be causing decreased Secchi depth and GPP during periods of lower water-levels could be resuspension of fine sediment along the new shorelines; sediments that had settled under conditions of higher water levels would be increasingly exposed as water levels fell. The energy needed for this is available at VB, where strong winds blow daily, but the relative abundance of the sediments suspended in the water column under different water-level conditions still needs to be measured to verify the importance of this possibility.
In either case, these results are consistent with those previously found by Valdespino-Castillo et al. Altogether, this pattern is also important to direct the needed reassessment of the contribution of reservoirs and lakes to the global carbon cycle Cole et al. The high GPP found in VB throughout the decade confirms that it has remained a very productive system, in spite of the wide water-level fluctuations and other changes. In fact, its C fixation rates are higher that those found during the initial assessment of — and are now within the range 2.
Hence, our results in terms of primary production indicate that VB would now be more accurately classified as hypertrophic than as eutrophic. Although productivity in VB is high, and nearly half of it is net production -which can be exported from the production layer to the sediments and become sequestered C- our respiration data and the comparison with net C burial assessed through independent radiometric methods of Carnero-Bravo et al.
Furthermore, because the total respiration in this ecosystem is also very high -nearly doubling GPP rates- the system has a net heterotrophic metabolism. These results are consistent with the findings of Gupta et al. More metabolic studies on tropical systems that include detailed measurements of vertical variation and respiration are needed, to reassess the contribution of epicontinental water bodies to global carbon balance Cole et al. It is expected that long-term data will be key to assessing metabolic variability Staehr et al.
Our results show that a decade of metabolic records can be enough to start identifying trends, as recently found by Agusti et al. Furthermore, the correlations found here with environmental drivers allow the exercise of simple predictions for VB that can inform global expectations. Similarly, our results on the inverse relationship between GPP and water level decrease RLLF also demonstrate that the water deficiency expected for the latitude of VB—if coupled with the intensification of its use as a source of fresh water—could enhance its role as a carbon source, a process that may also occur in the numerous water reservoirs that will be more intensively used throughout similar latitudes.
Production and respiration records for VB over the course of a decade show that high respiration of eutrophic tropical reservoirs can surpass their high production and carbon burial rates, and therefore these reservoirs likely act as important atmospheric carbon sources. Temperature and water level variations significantly affect metabolic rates in VB. Mixing, food web changes and nutrient limitation likely play a role that needs to be further investigated. The metabolism of more tropical systems must be studied, in order to improve global budgets, and to build more long-term series to support the prediction of future trends.
Our results point to an increase in net heterotrophy of deep eutrophic reservoirs as temperatures increase and as their water levels fluctuate in response to climate change and increased exploitation of their water for human use. Common use cases Typos, corrections needed, missing information, abuse, etc. Our promise PeerJ promises to address all issues as quickly and professionally as possible.
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Keto et al. They showed that the of drawing water from lakes resulting in their community patterns of the drift line were influenced shrinkage and increased eutrophication. The combi- by the previous water level. WLF accounted for most nation of summer drought and intense water use of the variation in these benthic communities. This reinforces the severity of this problem. Skoulikidis finding was corroborated by White et al. They found such as arsenic and chrome in a deep lake in Greece significant correlations between water quality para- as well.
WLF potentially interfere with the influences that Balogh et al. In Swedish lakes that experienced small WLF, , which exposed most of the rip-rap substrates. However, Pabst et al. These WLF often cause etation establishment. Lastly, an overarching freezing of the exposed littoral. In Finland, over concept Wantzen et al. In spite of finding large differences in density These articles show the large variety of issues that When attempting to summa- really significant, because variables such as nutrient rise the manuscripts for the current article, we found level and lake size affected the fish communities.
In this article, Konstanz, Sparks, The flood pulse concept in river-floodplain systems. Canadian Special Bjelke, U. Herrmann, Temporal niches Publication of Fisheries and Aquatic Sciences of shredders in lake littorals with possible implications on — Aquatic Ecology 41— Junk, W. Wantzen, The flood pulse concept: Bond, R.
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