Dissolved organic carbon mobilisation in relation to variable discharges and environmental flows in a highly regulated lowland river

Westhorpe, Douglas P.; Mitrovic, Simon M.

doi:10.1071/mf12122

Cited by 27 publications

(24 citation statements)

References 72 publications

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“…A significant increase in organic nutrients (DOC and DON) and FRP was observed in the Hunter and Paterson rivers. Up to 8-fold increases in DOC concentrations have been observed during flood conditions in river and estuarine systems (Westhorpe & Mitrovic 2012), and we observed DOC concentrations in the Hunter River to increase from less than 5 mg l −1 to above 15 mg l −1 at Sites 3, 4, 6 and 7.…”

Section: Changes In Physical and Chemical Conditions During Inflow Evmentioning

confidence: 68%

“…Turbidity measurements were taken using a Hach turbidity Meter (Hach Company). Surface samples for dissolved organic carbon (DOC) were collected in triplicate and immediately filtered through 0.45 µm cellulose acetate filters (Sartorius Stedim Biotech) into pre-combusted 200 ml glass bottles, refrigerated and then acidified with 2N hydrochloric acid before analysis on a Shimadzu TOC-VCSH analyser using the High Temperature Combustion Method (Eaton et al 1995, Westhorpe & Mitrovic 2012. Nutrient samples (50 ml) were separately analysed for total nitrogen (TN), dissolved organic nitrogen (DON), oxidised nitrogen (NO x ), ammoniacal nitrogen (NH 4 ), total phosphorus (TP) and filtered reactive phosphorus (FRP).…”

Section: Author Copymentioning

confidence: 99%

“…Physical and chemical conditions within lotic systems can shift slowly, such as between seasons, or very abruptly, particularly following precipitation events that lead to high inflows and flooding (Westhorpe & Mitrovic 2012). As the foundation of lotic food webs, microbes are among the first organisms to experience and respond to changes in the dynamic physicochemical environment of rivers and their estuaries (Kirchman et al 2004, Wear et al 2013.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

River bacterioplankton community responses to a high inflow event

Carney¹,

Mitrovic²,

Jeffries³

et al. 2015

Aquat. Microb. Ecol.

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Microbes drive chemical cycling and productivity within river ecosystems, but their influence may shift when intense allochthonous inputs accompany high freshwater inflow (flood) events. Investigating how floods influence microbial processes is fundamentally important for our understanding of river ecology, but is generally overlooked. We analysed bacterioplankton community composition (BCC) and abundance over 4 mo following an enormous flood event in the Hunter River, Australia, that resulted in a major fish kill. Concentrations of dissolved organic carbon (DOC) and inorganic nutrients (N and P) were up to 3 times higher during the flood event compared to prior and subsequent months. Bacterial cell abundances were up to 10 times higher at impacted sites during the flood event. Using Automated Ribosomal Intergenic Spacer Analysis we found significant shifts in BCC between the flood impacted month and subsequent months (p < 0.05). Distance linear modelling indicated that DOC and dissolved N and P correlated most strongly with BCC patterns during the high inflow, whereas community dynamics correlated most strongly with nitrogen oxides and ammonium during the river's recovery phase. 16S rRNA amplicon pyrosequencing revealed that common soil-associated and facultative anaerobic genera of Proteobacteria were most dominant during the flood period, suggesting that a proportion of the bacterial community observed during this event were potentially inactive soil microbes transported into the river via terrestrial runoff. During the recovery period, Cyanobacteria and freshwater-associated genera of Actinobacteria and Proteobacteria became dominant in 16S rRNA pyrosequencing profiles. These observations indicate that allochthonous nutrients delivered via floods can significantly stimulate bacterial growth, underpinning substrate-controlled succession of bacterial communities and ultimately shaping the ecology within river ecosystems.

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Section: Changes In Physical and Chemical Conditions During Inflow Evmentioning

confidence: 68%

Section: Author Copymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

River bacterioplankton community responses to a high inflow event

Carney¹,

Mitrovic²,

Jeffries³

et al. 2015

Aquat. Microb. Ecol.

View full text Add to dashboard Cite

show abstract

“…Allochthonous DOC is one of the largest organic carbon fluxes from catchments to aquatic systems and is influenced by many factors including rainfall, hydrologic flow paths, catchment land use, flooding, leaching and presence of wetlands (Hinton et al 1998;Westhorpe and Mitrovic 2012). Understanding the processes controlling the transfer of DOC from terrestrial to aquatic environments is of fundamental importance to aquatic sciences (Wilson et al 2016).…”

Section: Transport Of Allochthonous Docmentioning

confidence: 99%

Allochthonous dissolved organic carbon in river, lake and coastal systems: transport, function and ecological role

Mitrovic

Baldwin

2016

Mar. Freshwater Res.

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“…The majority of allochthonous carbon enters rivers, and in turn estuaries, during episodic flow events (Hinton et al, 1997;Raymond and Saiers, 2010;Webster et al, 1987;Westhorpe and Mitrovic, 2012). A number of studies have conceptualised hydrologic conditions in the rivers as 'storm flow' and 'base flow' which has been useful in demonstrating that whilst storm flow conditions only occur for short periods of time, they disproportionally account for a large portion of organic carbon exported from the catchment (Buffam et al, 2001;Hinton et al, 1997;Raymond and Saiers, 2010).…”

Section: Introductionmentioning

confidence: 99%

Highs and lows: The effect of differently sized freshwater inflows on estuarine carbon, nitrogen, phosphorus, bacteria and chlorophyll a dynamics

Hitchcock

Mitrovic

2015

Estuarine, Coastal and Shelf Science

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Freshwater inflows play a key role in the delivery of organic carbon to estuaries. However, our understanding of the dynamics between discharge and carbon globally is limited. In this study we performed a 30-month monitoring study on the Bega and Clyde River estuaries, Australia, to understand the influence that discharge had on carbon, nitrogen, phosphorus, bacteria and chlorophyll a dynamics. We hypothesised that 1) discharge would be the most important factor influencing carbon and nutrient concentrations, though during low flows chlorophyll a would also be positively related to carbon, 2) bacteria would be related to dissolved organic carbon (DOC), and chlorophyll a to temperature, nitrogen and phosphorus, and 3) that concentrations of carbon, nitrogen, phosphorus, bacterial biomass and chlorophyll a would be significantly different between large 'flood flows', smaller 'fresh flows' and base flow conditions. We found that discharge was always the most important factor influencing carbon and nutrient concentrations, and that primary production appeared to have little influence on the variation in DOC concentration even during base flow conditions. We suggest this relationship is likely due to highly episodic discharge that occurred during the study period. Bacteria were related to DOC in the lower estuary sites, but phosphorus in the upper estuary. We suggest this is likely due to the input of bioavailable carbon in the upper estuary leading bacteria to be P limited, which changes downstream to carbon limitation as DOC becomes more refractory. Chlorophyll a was positively related to temperature but not nutrients, which we suggest may be due to competition with bacteria for phosphorus in the upper estuary. Carbon, nitrogen and phosphorus concentrations were different under flood, fresh and base flow conditions, though these differences sometimes varied between estuary locations for different resources. Overall, the results demonstrate that discharge plays an important structuring role for carbon, nutrient and bacteria dynamics on the Bega and Clyde Rivers, and that the differences observed between flood and fresh inflows suggest that further study into the influence of differently sized inflow events is important.

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Dissolved organic carbon mobilisation in relation to variable discharges and environmental flows in a highly regulated lowland river

Cited by 27 publications

References 72 publications

River bacterioplankton community responses to a high inflow event

River bacterioplankton community responses to a high inflow event

Allochthonous dissolved organic carbon in river, lake and coastal systems: transport, function and ecological role

Highs and lows: The effect of differently sized freshwater inflows on estuarine carbon, nitrogen, phosphorus, bacteria and chlorophyll a dynamics

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