Flow extremes and benthic organic matter shape the metabolism of a headwater Mediterranean stream

Acuña, Vicenç; Giorgi, Adonis; Muñoz, Isabel; Uehlinger, Urs; Sabater, Sergi

doi:10.1111/j.1365-2427.2004.01239.x

Cited by 174 publications

(164 citation statements)

References 48 publications

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“…In this context, we predicted that the intermittent stream would experience more frequent periods of imbalance between R and U gross than the perennial stream because larger hydrological fluctuations at the former may favor less-steady-state conditions. In fact, dramatic changes in the temporal pattern of water chemistry, algal composition, organic matter accumulation, stream metabolism, and nutrient retention efficiency have been reported after hydrological disturbances in the intermittent stream (Acuña et al 2004, von Schiller et al 2008, Bernal et al 2013. Nonetheless, our results did not support our prediction.…”

Section: Discussioncontrasting

confidence: 57%

A round-trip ticket: the importance of release processes for in-stream nutrient spiraling

Schiller¹,

Bernal²,

Sabater³

et al. 2015

Freshwater Science

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Most nutrient-spiraling studies have focused on estimates of gross uptake (U gross ), which show that streams take up dissolved inorganic nutrients very efficiently. However, studies based on estimates of net uptake (U net ) emphasize that streams tend to be at biogeochemical steady state (i.e., U net ≈ 0), at least on a time scale of hours. These findings suggest that streams can be highly reactive ecosystems but remain at short-term biogeochemical steady state if U gross is counterbalanced by release (R), a process that remains widely unexplored. Here, we propose a novel approach to infer R by comparing U net and U gross estimated from ambient and plateau concentrations obtained from standard short-term nutrient additions along a reach. We used this approach to examine the temporal variation of R and its balance with U gross in 2 streams with contrasting hydrological regime (i.e., perennial vs intermittent) during 2 years. We focused on the spiraling metrics of NH 4 + and soluble reactive P (SRP), essential sources of N and P in stream ecosystems. R differed substantially between the 2 streams. The perennial stream had a higher proportion of dates with R > 0 and a 2× higher mean R than the intermittent stream for both nutrients. Despite these differences, the magnitude of R and U gross tended to be similar for both nutrients within each stream, which lead to U net ≈ 0 in most cases. A notable exception occurred for SRP in the intermittent stream, where R tended to be higher than U gross during most of the winter period, probably because of desorption of P from stream sediments. Together, our findings shed light on the contribution of release processes to the dynamics of nutrient spiraling and support the idea that streams can be active ecosystems with high spiraling fluxes while simultaneously approaching short-term biogeochemical steady-state.

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Section: Discussioncontrasting

confidence: 57%

A round-trip ticket: the importance of release processes for in-stream nutrient spiraling

Schiller¹,

Bernal²,

Sabater³

et al. 2015

Freshwater Science

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“…In open canopy streams, maximum values of GPP and ER occur in summer and spring when temperature and radiation are high (Velasco et al, 2003). However, in closed canopy streams, GPP is maximum in early spring when light incidence on the stream surface increases, while the maximum ER occurs in autumn when organic matter accumulations are highest (Acuña et al, 2004). During the study, stream production predominated over stream consumption reflecting that Rambla Salada is an autotrophic ecosystem with a positive mean MDN and a mean P/R higher than 1.…”

Section: Seasonal Variation Of Metabolic Ratesmentioning

confidence: 98%

“…These floods are very important for benthic primary producers in open streams in terms of habitat suitability, biomass and distribution (Biggs, 1996). Floods reduce algal biomass and macroinvertebrate density, in addition to carrying high concentrations of suspended solids that reduce both primary production and ER (Acuña et al, 2004;Uehlinger, 2006;Roberts et al, 2007). In Rambla Salada, the intense rains occurring in December 2003 produced a moderate flood that caused a strong reduction in GPP and ER rates (99% and 97%, respectively), helped by the low temperature and radiation.…”

Section: Seasonal Variation Of Metabolic Ratesmentioning

confidence: 99%

“…Streams in Mediterranean climate regions are influenced by a sequence of regular and often extreme flooding and drying (Gasith & Resh, 1999). These hydrological extremes have great influence on the dynamics of metabolic rates (Acuña et al, 2004(Acuña et al, , 2005. On the other hand, intensive agriculture and industrial and urban sewage are the main human stressors in the Mediterranean region that increase nutrient concentrations in the streams stimulating both primary production and ER .…”

Section: Introductionmentioning

confidence: 99%

“…Several studies have determined the factors controlling metabolic rates in Mediterranean streams (Mollá et al, 1994;Mollá et al, 1996;Velasco et al, 2003;Acuña et al, 2004Acuña et al, , 2005, but the effects of salinity on stream functioning have not been studied.…”

Section: Introductionmentioning

confidence: 99%

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Effects of dilution stress on the functioning of a saline Mediterranean stream

2008

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The effects of seasonality and dilution stress on the functioning of Rambla Salada, a hypersaline Mediterranean stream in SE Spain, were evaluated. The stream is subject to diffuse freshwater inputs from the drainage of intensively irrigated agriculture in the catchment and periodic losses of water through an irrigation channel. Metabolic rates and the biomass of primary producers and consumers were estimated over a 2-year period. During the first year several dilution events occurred, while during the second year the salinity recovery reached predisturbance levels. Functional indicators were compared in the disturbance and recovery salinity periods. Primary production and respiration rates in the Rambla Salada ranged between 0.07-21.05 and 0.19-17.39 g O 2 m -2 day -1 , respectively. The mean values for these variables were 7.35 and 5.48 g O 2 m -2 day -1 , respectively. Mean net daily metabolism rate was 1.87 ± 0.52 g O 2 m -2 day -1 and mean production/respiration ratio was 2.48 ± 1.1, reflecting autotrophic metabolism. The metabolic rates showed the typical seasonal pattern of Mediterranean open canopy streams. Therefore, gross primary production (GPP) and ecosystem respiration (ER) registered maximum values in summer, intermediate values in spring and autumn and minimum values in winter. The metabolic rates and biomass of consumers were greater in the disturbance period than in the recovery period. However, they did not show significant differences between periods due to their important dependence on seasonal cycle. Seasonality accounted for much of the temporal variability in GPP and ER (76% and 83% in the multiregression models, respectively). Light availability seems to be the most important factor for GPP and ER in the Rambla Salada. Autotrophic biomass responded more to variations in discharge and conductivity than to seasonal variations. In fact, it was severely affected by freshwater inputs after which the epipelic biomass decreased significantly and Cladophora glomerata proliferated rapidly. Epipelic algal biomass was the most sensitive parameter to dilution disturbance.

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Ecosystem respiration increases with biofilm growth and bed forms: Flume measurements with resazurin

et al. 2014

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In a set of streamside mesocosms, stream ecosystem respiration (ER) increased with biofilm biomass and flow heterogeneity (turbulence) generated by impermeable bed forms, even though those bed forms had no hyporheic exchange. Two streamside flumes with gravel beds (single layer of gravel) were operated in parallel. The first flume had no bed forms, and the second flume had 10 cm high dune-shaped bed forms with a wavelength of 1.0 m. Ecosystem respiration was measured via resazurin reduction to resorufin in each flume at three different biomass stages during biofilm growth. Results support the hypothesis that ER increases with flow heterogeneity generated by bed forms across all biofilm biomass stages. For the same biofilm biomass, ER was up to 1.9 times larger for a flume with 10 cm high impermeable bed forms than for a flume without the bed forms. Further, the amount of increase in ER associated with impermeable bed forms was itself increased as biofilms grew. Regardless of bed forms, biofilms increased transient storage by a factor of approximately 4.

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Flow extremes and benthic organic matter shape the metabolism of a headwater Mediterranean stream

Cited by 174 publications

References 48 publications

A round-trip ticket: the importance of release processes for in-stream nutrient spiraling

A round-trip ticket: the importance of release processes for in-stream nutrient spiraling

Effects of dilution stress on the functioning of a saline Mediterranean stream

Ecosystem respiration increases with biofilm growth and bed forms: Flume measurements with resazurin

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