Abstract
Submerged macrophytes are subjected to potential mechanical stresses associated with fluctuating water levels in natural conditions. However, few experimental studies have been conducted to further understand the effects of water level fluctuating amplitude on submerged macrophyte species and their assemblages or communities. We designed a controlled experiment to investigate the responses of three submerged macrophyte species (Hydrilla verticillata, Ceratophyllum demersum and Elodea nuttallii) and their combinations in communities to three amplitudes (static, ± 30 cm, ± 60 cm) of water level fluctuations. Results showed that water level fluctuating amplitude had little effects on the community performance and the three tested species responded differently. H. verticillata exhibited more growth in static water and it was negatively affected by either of the water level fluctuations amplitude, however, growth parameters of H. verticillata in two fluctuating water level treatments (i.e., ± 30 cm, ± 60 cm) were not significantly different. On the other hand, the growth of C. demersum was not significantly correlated with different amplitude treatments. However, it became more abundant when water levels fluctuated. E. nuttallii was inhibited by the two fluctuating water level treatments, and was less in growth parameters compared to the other species especially in water level fluctuating conditions. The inherent differences in the adaptive capabilities of the tested species indicate that C. demersum or other species with similar responses may be dominant species to restore submerged macrophyte communities with great fluctuating water levels. Otherwise, H. verticillata, E. nuttallii or other species with similar responses could be considered for constructing the community in static water conditions.
Highlights
Submerged macrophytes play an important role in aquatic ecosystems [1,2,3] as they mediate some significant ecological processes such as purifying water, increasing nutrient retention and providing refuge or food for some organisms [3,4,5]
We addressed the following questions: (1) how did the performance and structure of simulated and real submerged macrophyte communities respond to water level fluctuating amplitude? (2) how did the growth of each species respond to fluctuating amplitude when they are in monoculture or in mixture, respectively?
The growth parameters of the two types of communities did not vary with different water level fluctuating amplitude treatments (Fig 3)
Summary
Submerged macrophytes play an important role in aquatic ecosystems [1,2,3] as they mediate some significant ecological processes such as purifying water, increasing nutrient retention and providing refuge or food for some organisms [3,4,5]. Submerged macrophyte communities are heavily influenced by both abiotic and biotic factors in their immediate environment like water. Effects of Amplitudes of Water Level Fluctuations on Submerged Macrophytes level fluctuations [6,7], light intensity [2], nutrient availability [5,8], dreissenid invasion [9], and the algae cover [2]. Amplitude of water level fluctuations may significantly change light availability, water pressure and other stability of factors in the aquatic environment [12,15]. The variation of water level fluctuating amplitude caused by both natural and human factors may greatly influence the performance of submerged macrophyte species and their communities [10,16]
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