Abstract
Aquatic ecosystems are particularly vulnerable to anthropogenic activity and climate change. The changes in flow regimes in Lithuanian lowland rivers due to the operation of hydropower plants (HPPs) and the impact of altered flow on some fish species have already been studied. The impact of climate change on future natural river runoff and the structure of fish assemblages was also investigated. However, it is still unknown how the combined effect of climate change and flow regulation related to hydropower generation may affect fish assemblages in the downstream river reaches below the Lithuanian HPPs. In this study, the physical habitat modelling system MesoHABSIM was used to simulate spatial and temporal changes in aquatic habitats availability for different fish species under the influence of HPP at different climate change scenarios. Changes in the available habitat were assessed for common fish species in four HPP-affected rivers representing different hydrological regions of Lithuania. The modelling results showed that the operation of HPP under climate change conditions in most rivers could be beneficial for small benthic fish species such as gudgeon Gobio gobio and stone loach Barbatula barbatula. Meanwhile, for larger fish species (e.g., chub Squalius cephalus and vimba Vimba vimba) the alteration in the temporal availability of suitable habitat was relatively higher.
Highlights
In the modern world, humankind is changing the natural environment at an unprecedented rate
Aquatic ecosystems are vulnerable to climate change because (i) many species within these fragmented habitats have limited abilities to disperse as the environment changes; (ii) water temperature and habitat availability are climate-dependent; and (iii) many systems are already exposed to numerous anthropogenic stressors [4]
Climate-induced changes in flow regimes cause additional stress to river systems that are already severely affected by anthropogenic activities such as hydropower production and dams [10,11]
Summary
Humankind is changing the natural environment at an unprecedented rate. Aquatic ecosystems are vulnerable to climate change because (i) many species within these fragmented habitats have limited abilities to disperse as the environment changes; (ii) water temperature and habitat availability are climate-dependent; and (iii) many systems are already exposed to numerous anthropogenic stressors [4]. It is common to mention rising water temperatures when it comes to the effects of climate on river ecosystems, changes in flow variability are no less important but more difficult to predict. Climate-induced changes in flow regimes cause additional stress to river systems that are already severely affected by anthropogenic activities such as hydropower production and dams [10,11]. The EU Member States point out that hydropower and dams are major contributors to the deterioration of the aquatic environment [12,13]. Forty-eight percent of rivers (expressed as river volume) globally are moderately to severely impacted by either flow regulation, fragmentation, or both [14], yet the hope for the sustainable development of dams remains [15]
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