Tracing dissolved organic matter (DOM) from land-based aquaculture systems in North Patagonian streams

Nimptsch, Jorge; Woelfl, Stefan; Osorio, Sebastian; Valenzuela, J.; Ebersbach, Paul; Tuempling, Wolf von; Palma, Rodrigo; Encina, Francisco; Figueroa, David; Kamjunke, Norbert; Graeber, Daniel

doi:10.1016/j.scitotenv.2015.07.160

Cited by 87 publications

(53 citation statements)

References 60 publications

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“…Finally, we compared the observed DOM decline along a reach downstream of the aquaculture in the Molco River10 with the measured rates of DOM degradation (estimated from BP in the present study). A 2700-meter stretch of the Molco River, with a stream width of 5 m and a factor of two for the top and bottom surface areas of gravel stones, resulted in a total biofilm area of 27,000 m 2 .…”

Section: Discussionmentioning

confidence: 99%

“…In Chile, pristine streams with otherwise rarely observed intact natural organic CHNO cycles9 occur in spatial proximity to anthropogenically affected streams. Land-based aquaculture has recently been shown to impact streams with high levels of altered DOM in northern Patagonia in Chile10. Chilean salmon production is economically important, contributing ~25% of the worldwide salmon yield (Chile ranks second of the world’s salmon-producing countries11).…”

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confidence: 99%

“…One aquaculture in northern Patagonia was estimated to release DOM amounting to 21% of the carbon applied as feed and 76% of the annual fish production10. However, limited detailed information on the DOM composition associated with fish aquaculture is available.…”

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confidence: 99%

“…However, limited detailed information on the DOM composition associated with fish aquaculture is available. The DOM leached from decaying carcasses after salmon spawning has been characterized by fluorescence measurements1415, but only two studies have applied this method to assess DOM quality from aquacultures: one study on rainbow trout in Denmark16 and one on salmon in Chile10. The latter study demonstrated that aquaculture DOM was dominated by protein-like fluorescence, which quickly degraded downstream within 2700 m10; however, advanced DOM specification and measurement of bacterial activity were not performed.…”

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confidence: 99%

“…The DOM leached from decaying carcasses after salmon spawning has been characterized by fluorescence measurements1415, but only two studies have applied this method to assess DOM quality from aquacultures: one study on rainbow trout in Denmark16 and one on salmon in Chile10. The latter study demonstrated that aquaculture DOM was dominated by protein-like fluorescence, which quickly degraded downstream within 2700 m10; however, advanced DOM specification and measurement of bacterial activity were not performed. No in-depth molecular characterization of DOM associated with aquaculture effluent has been conducted using ultrahigh-resolution Fourier transform ion cyclotron mass spectrometry (FTICR MS)171819, nuclear magnetic resonance spectroscopy (NMR)202122, or a combination of these techniques with excitation-emission matrices (EEM)23.…”

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confidence: 99%

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Land-based salmon aquacultures change the quality and bacterial degradation of riverine dissolved organic matter

Kamjunke

Nimptsch

Harir

et al. 2017

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Aquacultures are of great economic importance worldwide but pollute pristine headwater streams, lakes, and estuaries. However, there are no in-depth studies of the consequences of aquacultures on dissolved organic matter (DOM) composition and structure. We performed a detailed molecular level characterization of aquaculture DOM quality and its bacterial degradation using four salmon aquacultures in Chile. Fluorescence measurements, ultrahigh-resolution mass spectrometry, and nuclear magnetic resonance spectroscopy of the DOM revealed specific and extensive molecular alterations caused by aquacultures. Aquacultures released large quantities of readily bioavailable metabolites (primarily carbohydrates and peptides/proteins, and lipids), causing the organic matter downstream of all the investigated aquacultures to deviate strongly from the highly processed, polydisperse and molecularly heterogeneous DOM found in pristine rivers. However, the upstream individual catchment DOM signatures remained distinguishable at the downstream sites. The benthic algal biovolume decreased and the bacterial biovolume and production increased downstream of the aquacultures, shifting stream ecosystems to a more heterotrophic state and thus impairing the ecosystem health. The bacterial DOM degradation rates explain the attenuation of aquaculture DOM within the subsequent stream reaches. This knowledge may aid the development of improved waste processing facilities and may help to define emission thresholds to protect sensitive stream ecosystems.

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confidence: 99%

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Land-based salmon aquacultures change the quality and bacterial degradation of riverine dissolved organic matter

Kamjunke

Nimptsch

Harir

et al. 2017

Sci Rep

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Shifts in the Source and Composition of Dissolved Organic Matter in Southwest Greenland Lakes Along a Regional Hydro‐climatic Gradient

et al. 2017

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Dissolved organic matter (DOM) concentration and quality were examined from Arctic lakes located in three clusters across south‐west (SW) Greenland, covering the regional climatic gradient: cool, wet coastal zone; dry inland interior; and cool, dry ice‐marginal areas. We hypothesized that differences in mean annual precipitation between sites would result in a reduced hydrological connectivity between lakes and their catchments and that this concentrates degraded DOM. The DOM in the inland lake group was characterized by a lower aromaticity and molecular weight, a low soil‐like fluorescence, and carbon stable isotope (δ13C‐DOC) values enriched by ~2‰ relative to the coastal group. DOC‐specific absorbance (SUVA254) and DOC‐specific soil‐like fluorescence (SUVFC1) revealed seasonal and climatic gradients across which DOM exhibited a dynamic we term “pulse‐process”: Pulses of DOM exported from soils to lakes during snow and ice melt were followed by pulses of autochthonous DOM inputs (possibly from macrophytes), and their subsequent photochemical and microbial processing. These effects regulated the dynamics of DOM in the inland lakes and suggested that if circumpolar lakes currently situated in cool wetter climatic regimes with strong hydrological connectivity have reduced connectivity under a drier future climate, they may evolve toward an end‐point of large stocks of highly degraded DOC, equivalent to the inland lakes in the present study. The regional climatic gradient across SW Greenland and its influence on DOM properties in these lakes provide a model of possible future changes to lake C cycling in high‐latitude systems where climatic changes are most pronounced.

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Bioavailable DOC: reactive nutrient ratios control heterotrophic nutrient assimilation—An experimental proof of the macronutrient-access hypothesis

et al. 2021

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We investigate the "macronutrient-access hypothesis", which states that the balance between stoichiometric macronutrient demand and accessible macronutrients controls nutrient assimilation by aquatic heterotrophs. Within this hypothesis, we consider bioavailable dissolved organic carbon (bDOC), reactive nitrogen (N) and reactive phosphorus (P) to be the macronutrients accessible to heterotrophic assimilation. Here, reactive N and P are the sums of dissolved inorganic N (nitrate-N, nitrite-N, ammonium-N), soluble-reactive P (SRP), and bioavailable dissolved organic N (bDON) and P (bDOP). Previous data from various freshwaters suggests this hypothesis, yet clear experimental support is missing. We assessed this hypothesis in a proof-of-concept experiment for waters from four small agricultural streams. We used seven different bDOC:reactive N and bDOC:reactive P ratios, induced by seven levels of alder leaf leachate addition. With these treatments and a stream-water specific bacterial inoculum, we conducted a 3-day experiment with three independent replicates per combination of stream water, treatment, and sampling occasion. Here, we extracted dissolved organic matter (DOM) fluorophores by measuring excitation-emission matrices with subsequent parallel factor decomposition (EEM-PARAFAC). We assessed the true bioavailability of DOC, DON, and the DOM fluorophores as the concentration difference between the beginning and end of each experiment. Subsequently, we calculated the bDOC and bDON concentrations based on the bioavailable EEM-PARAFAC fluorophores, and compared the calculated bDOC and bDON concentrations to their true bioavailability. Due to very low DOP concentrations, the DOP determination uncertainty was high, and we assumed DOP to be a negligible part of the reactive P. For bDOC and bDON, the true bioavailability measurements agreed with the same fractions calculated indirectly from bioavailable EEM-PARAFAC fluorophores (bDOC r2 = 0.96, p < 0.001; bDON r2 = 0.77, p < 0.001). Hence we could predict bDOC and bDON concentrations based on the EEM-PARAFAC fluorophores. The ratios of bDOC:reactive N (sum of bDON and DIN) and bDOC:reactive P (equal to SRP) exerted a strong, predictable stoichiometric control on reactive N and P uptake (R2 = 0.80 and 0.83). To define zones of C:N:P (co-)limitation of heterotrophic assimilation, we used a novel ternary-plot approach combining our data with literature data on C:N:P ranges of bacterial biomass. Here, we found a zone of maximum reactive N uptake (C:N:P approx. > 114: < 9:1), reactive P uptake (C:N:P approx. > 170:21: < 1) and reactive N and P co-limitation of nutrient uptake (C:N:P approx. > 204:14:1). The “macronutrient-access hypothesis” links ecological stoichiometry and biogeochemistry, and may be of importance for nutrient uptake in many freshwater ecosystems. However, this experiment is only a starting point and this hypothesis needs to be corroborated by further experiments for more sites, by in-situ studies, and with different DOC sources.

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Tracing dissolved organic matter (DOM) from land-based aquaculture systems in North Patagonian streams

Cited by 87 publications

References 60 publications

Land-based salmon aquacultures change the quality and bacterial degradation of riverine dissolved organic matter

Land-based salmon aquacultures change the quality and bacterial degradation of riverine dissolved organic matter

Shifts in the Source and Composition of Dissolved Organic Matter in Southwest Greenland Lakes Along a Regional Hydro‐climatic Gradient

Bioavailable DOC: reactive nutrient ratios control heterotrophic nutrient assimilation—An experimental proof of the macronutrient-access hypothesis

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