The effects of storm-induced events on the seasonal dynamics of epilithic algal biomass in subtropical mountain streams

Abstract

Abstract. Information concerning the drivers of seasonal variation in algal biomass in subtropical mountain streams is limited. To identify the drivers of biomass dynamics for epilithic algae, a 20-month study was conducted in mountain streams in Taiwan, an area characterised by different levels of riparian vegetation coverage and agricultural activity, in which a process-based model was optimally fit to field data. We found that episodic typhoon-induced floods were the major drivers shaping the seasonal variations in algal biomass. Flow-induced detachment was frequently observed in periods of higher algal biomass. In contrast, an increased flow stimulated algal growth during periods with slower flow rates. Increased temperature stimulated algal growth at sites with an open canopy cover and higher light availability but constrained biomass at sites with dense canopy shading. Overall, scraper biomass exerted less influence on algal biomass than did environmental factors. The effects of grazing were visible only at the pristine, low-stream-order site in winter. The effects of minimal algal biomass required for recovery was comparable to environmental factors only at sites with intermediate canopy cover, moderate discharge, and higher nutrient concentrations. We suggest that agricultural activity and riparian vegetation can affect epilithic algal biomass in subtropical mountain streams.

Benthic algal biomass and assemblage changes following environmental flow releases and unregulated tributary flows downstream of a major storage

“…Benthic algae are the dominant primary producers in most upland stream ecosystems (Biggs 1995;Biggs and Smith 2002) and are one of the main sources of energy for higher trophic levels (Minshall 1978;Thorp and Delong 2002). Disturbances such as floods are one of the most important regulators of spatial and temporal variability in benthic communities of rivers (Davis and Barmuta 1989;Tsai et al 2014) and are a central structuring element for benthic algal assemblages (Duncan and Blinn 1989;Downes et al 1998;Biggs and Smith 2002). Such phenomena, depending on magnitude, can temporarily reduce stream primary production (Tett et al 1978;Uehlinger et al 2003) and benthic algal abundance (Biggs and Close 1989;Grimm and Fisher 1989) and alter benthic algal assemblage composition (Peterson 1996;Biggs et al1999).…”

Factors Controlling Changes in Epilithic Algal Biomass in the Mountain Streams of Subtropical Taiwan

“…Water velocity was the important variable regulating epilithic algal composition [43]. Tsai et al [44] developed a process-based model to investigate how storm-induced velocity influenced the variations of epilithic algal biomass in the CCW Stream. They determined that the algal biomass was considerably reduced by a high storm-induced velocity.…”

Benthic algal resilience to frequent wet-season storm flows in low-order streams in the Australian tropical savanna

“…Most field studies have involved tracking responses of benthic algae to storm flows and floods in temperate rivers and streams (Biggs and Close 1989, Grimm and Fisher 1989, Uehlinger et al 1996, Riseng et al 2004). In subtropical and tropical studies, re-E-mail addresses: 2 simon.townsend@nt.gov.au; 3 michael.douglas@cdu.edu.au searchers have identified the wet season as a period of lower benthic algal biomass compared to other periods because of frequent storms (Mosisch and Bunn 1997, Yang et al 2009, Kohler et al 2012, Tsai et al 2014.…”