Trophic State in Voyageurs National Park Lakes before and after Implementation of a Revised Water‐Level Management Plan

2014 ◽  
Vol 51 (1) ◽  
pp. 99-111 ◽  
Author(s):  
Victoria G. Christensen ◽  
Ryan P. Maki
2021 ◽  
Author(s):  
Evie S Brahmstedt ◽  
Carla N Ayala Crespo ◽  
Thomas M Holsen ◽  
Michael Twiss

Abstract Legacy mercury (Hg) exists in Upper St. Lawrence River wetland hydric soils and is impacted by a new water level management plan (established in 2017) implemented to restore biodiversity and reduce the monotypic nature of riparian wetlands, currently dominated by Typha spp.. The distribution of Hg within the various components of a riparian wetland provides insight into potential impacts of water level fluctuations. Hydric soil represents 83% of the wetland Hg burden while wetland plant biomass contributed 17%, mostly due to organic detritus (13%). Although Typha roots had a bioconcentration factor of 1.2 (relative to hydric soils) and had the highest total Hg among living tissues (25 ± 9.3 ng/g dry wt.), detritus had the highest overall Hg content (110 ± 53 ng/g dry wt.). While root tissue Hg correlated significantly with soil Hg (p = 0.045), it was determined here that Typha spp. has limited use as a biomonitor in wetlands with low levels of Hg contamination, as in this ecosystem. Hg contained within the organic detritus contributed more to the overall Hg burden in these monotypic Typha wetlands than any other tissue or biomass component analyzed. Consequently, shifts in the plant community that are expected to result from a new water level management plan may alter Hg storage within these wetlands and affect its mobility in this ecosystem.


2021 ◽  
Vol 24 (5) ◽  
pp. 469-483
Author(s):  
Soo-Dong Lee ◽  
Han Kim ◽  
Bong-Gyo Cho ◽  
Gwang-Gyu Lee

Background and objective: If the Nelumbo nucifera spreads in a wetland at a high density, it can have considerable positive and negative ecological effects on habitats. For this reason, it is necessary to precisely investigate the impacts of its rapid proliferation. This study was conducted to propose the distribution and management of N. nucifera, which can cause the degradation of wildlife habitats due to the rapid spread of internal and external environmental factors that may affect the Junam wetland ecosystem. Methods: For the investigation and analysis of physical and ecological characteristics, factors of the abiotic environment such as general weather conditions, topography and water depth structure, and soil and water quality analysis, and bioenvironment characteristics such as changes in the N. nucifera community distribution were evaluated. To assess whether the differences in the soil depth and physicochemical characteristics between the N. nucifera community and the aquatic plant community are statistically significant, a One-way ANOVA was executed. Results: N. nucifera was presumably introduced in approximately 2007 and observed at a prevalence of only 0.8% in 2009, but had expanded to 11.1% in 2014. After that, the area was increased to 19.3% in 2015 and 40.0% in 2017, about twice that of the previous survey year. The rapid diffusion of an N. nucifera colony can have adverse effects on wildlife habitats and biodiversity at Junam Wetland. To solve these problems, four management methods can be proposed; water level management, mowing management, installation of posts and removal of lotus roots. Control of the N. nucifera community using these methods was judged to be suitable for cutting and water level management when considering expansion rate, water level variation, and wildlife habitat impacts. Conclusion: As the biotic and abiotic environmental factors are different for each wetland, it is necessary to determine the timing and method of management through a detailed investigation.


1995 ◽  
Vol 31 (8) ◽  
pp. 239-243 ◽  
Author(s):  
W. Ligtvoet ◽  
S. A. de Jong

In the 6000 ha Lake Volkerak-Zoom, a new freshwater system in the estuarine southwest of The Netherlands, biomanipulation is used as a tool in ecosystem development. The basic ecological concepts for ecosystem development are described. Key factors in the integrated water management are fish stock management and water level management, geared towards creating optimal conditions for northern pike, the dominant predator in mesotrophic waters. The main aspects of the water level management and the fish stock management are outlined.


2021 ◽  
pp. 1-8
Author(s):  
Zilca Campos ◽  
Fábio Muniz ◽  
William E. Magnusson ◽  
Guilherme Mourão

Abstract The Belo Monte hydroelectric dam on the Xingu River has the third largest generating capacity of any hydroelectric dam in the world. We conducted surveys of crocodilians (Caiman crocodilus, Paleosuchus trigonatus) by boat in the Xingu River at the site of the dam prior to (2013-2015), and after filling (2016-2017). While the number of C. crocodilus sighted decreased with increasing water level, there was no difference in numbers prior to, and after reservoir filling. The number of P. trigonatus was unaffected by both water level prior to and after reservoir filling. Reservoir filling had little effect on the number of crocodilians using the forest around the Xingu River reservoir. Most crocodilians seen in forest surveys were P. trigonatus, both before and after reservoir filling, but C. crocodilus was recorded occasionally in the forest. It seems that most Amazonian crocodilians are sufficiently generalist to adapt to the new conditions created by the construction of dams, at least in the short-term. However, there may be long-term collateral effects on crocodilian populations from dams, due to as deforestation and improved access for hunters.


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