The effect of altered flow regimes on aquatic primary producer communities: Diatoms and macrophytes

Abstract

Rivers are intensively managed worldwide through unprecedented flow regime alterations on a global scale. This has led to an increasing interest in the development of quantitative tools to assess the ecological response of organisms to flow alteration. To date, studies reflect a large diversity of responses that make the intensity and prevalence of effects difficult to generalize. The present study analysed how flow alterations caused by dams affect the structure, composition and traits of diatoms and macrophytes in three Spanish river basins (Cantabric, Ebro and Duero). By using a control‐impact design based mainly in hydrological similarity, our results showed consistent patterns of change in diatom and macrophyte communities. Our study showed a shift from resistant traits such as non‐colonial diatom forms and crust‐forming algae, which are adapted to the extreme events and natural dynamism of unregulated rivers, towards planktonic diatoms, free‐floating algae and the mass development of aquatic plants in hydrological altered sites. Both communities shared common thresholds of response to altered hydrological attributes that could be considered in a flow management context. The hydrological indices that impacted diatom and macrophyte communities the most were related with the magnitude and duration of minimum flows. However, our results also show that it is important to consider the interrelationships between the different hydrological attributes such as the seasonal variability of monthly flows, the magnitude of maximum annual extremes, the timing of flow events, and the frequency and rate of flow changes.

Assessing the effects of irrigation and hydropower dams on river communities using taxonomic and multiple trait-based approaches

“…2). Small-sized diatoms and low profile (adnate and pedunculate life forms, mostly represented in our dataset by Cocconeis euglypta and Achnathidium pyrenaicum, respectively) were replaced by planktonic and large-sized diatom cells in sites affected by irrigation dams, in agreement with Goldenberg-Vilar et al (2021) and Wang et al (2022). In NC2, the planktonic guild was linked to irrigation-impacted sites, while larger cell sizes and low profile adnate diatoms were more abundant in sites affected by hydropower dams.…”

Assessment of dam-induced changes in ecogeomorphological behaviour and fluvial functionality in the Damodar River, West Bengal, India

“…Most of the world's major rivers are being intensively modified (Goldenberg-Vilar et al 2021) by water resource management tools such as dams and barrages through which an altered seasonal flow regime and peak flow discharge is obtained on a global scale. Flow discharge is a vital element that significantly impacts the aquatic habitat, river morphology, biotic life, river connectivity, and water quality (Mitra & Singh 2018).…”

Flow pulses shape periphyton differently according to local light and nutrient conditions in experimental lowland streams

“…Even small changes in light availability, resulting from forest clearing, can have profound effects on in-stream primary production (Graça et al, 2018). Moreover, increased use of fertilisers and other agrochemicals inevitably leads to higher phosphorus (P) and nitrogen (N) loads to streams by surface and subsurface runoff, depending on the local current and future climate (Gao et al, 2014;Goyenola et al, 2015Goyenola et al, , 2020Jeppesen et al, 2009;Ockenden et al, 2016). This may result in a wide range of environmental, social and economic problems, as diffuse source-induced eutrophication is one of the main causes of the deterioration of aquatic ecosystems across the stream-to-marine continuum (Jabłońska et al, 2020;Kronvang et al, 2007).…”

“…Understanding the effects of temporary abrupt flow pulses, and their interaction with light and nutrient availability on the periphyton community is needed to allow predictions of effects on ecosystem functioning under future scenarios of riparian cover loss, accelerated eutrophication and increased discharge variability that can serve to inform stream management under climate change. To date, several studies have investigated the effects of light, nutrients and flow pulses as single factors or combining two of the parameters as stressors (Adámek et al., 2016; Bækkelie et al., 2017; Bondar‐Kunze et al., 2016; Goldenberg‐Vilar et al., 2021; Wu et al., 2019), but less is known about the simultaneous effects of the three factors.…”