Estimating nutrient budgets in tropical estuaries subject to episodic flows

Webster, Ian T.; Ford, Phillip W.; Tillman, Pei

doi:10.1016/j.marpolbul.2004.10.027

Cited by 15 publications

(8 citation statements)

References 11 publications

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“…The coastal waters of the Gulf of Carpentaria are N depauperate so N loads from the catchment are likely to have a significant effects on water column and nearshore benthic productivity (Burford et al, 2009). Nutrient loads from the estuary in the current study were comparable with discharges from another tropical dryland river system with an agricultural catchment, the Fitzroy River (Webster et al 2005). Downing et al (1999) found that, globally, tropical rivers had higher N discharge than temperate systems, and estimated a discharge range of 200 -1000 kg N km 2 catchment y -1 .…”

Section: Discussionsupporting

confidence: 51%

“…A second one-dimensional model was developed to simulate horizontal solute transport (Webster et al, 2005). This model averaged over the tides and solved the advection-diffusion equation.…”

Section: N and P Budgetsmentioning

confidence: 99%

“…This is most pronounced in the subtropics and tropics where the magnitude and duration of flow events are much higher, due to monsoonal weather patterns. Freshwater flow can play an important role in increasing nutrient concentrations and loads to estuaries (Eyre, 2000;Eyre and Ferguson, 2006;Webster et al, 2005). Additionally, flow events change water residence times which can have negative effects on phytoplankton productivity.…”

Section: Introductionmentioning

confidence: 99%

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Controls on phytoplankton productivity in a wet–dry tropical estuary

Burford

Webster

Revill

et al. 2012

Estuarine, Coastal and Shelf Science

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Flood events typically enhance primary productivity in estuaries via the increased nutrient inputs from land runoff. This study examined the drivers of phytoplankton biomass accumulation and productivity in a tropical estuary with a distinct wet-dry seasonality, i.e. months of little or no rainfall, and a highly episodic extended wet season. The study found that over two wet seasons, there was little evidence of freshwater inputs increasing nutrient concentrations, and chlorophyll a concentrations and phytoplankton productivity rates decreased in the water column, probably due to low water residence times. The magnitude and duration of freshwater flows in the wet season appeared to affect the scale of reduction of phytoplankton productivity and biomass accumulation. In contrast to many studies, there was also no evidence of post-flooding stimulation of chlorophyll a concentration with net export of nutrients in both the wet and dry seasons. Nitrogen (N) and light appeared to be key limiting factors for phytoplankton growth with estuarine DIN rapidly turned over by phytoplankton, no evidence of N fixation by phytoplankton, and a response to N, but not phosphorus (P), in algal bioassays. Tidal resuspension of sediments was an important physical process that limited light availability for primary productivity. The lack of higher nutrient concentrations as a result of freshwater inputs, and lack of post-flood algal growth stimulation contrasts with the findings of studies in eutrophied systems. in turn, fuel primary production in the months during and post-flooding once flow and turbidity have decreased, and salinity has increased (Mallin et al., 1993; Gillanders and Kingsford, 2002; Murrell et al., 2007). Wet and dry tropical/subtropical river systems account for 68% of Australian estuaries, meaning that they are an important contributor to the productivity of estuarine and coastal systems (Bucher and Saenger, 1994). Indeed studies have shown a correlation between catches of estuarine fish and crustaceans, and measures of freshwater flow which suggests that freshwater inputs may be providing nutrients and carbon to fuel productivity in estuaries (Gillanders and Kingsford, 2002; Robins et al., 2005). Conversely, estuarine productivity appears to be negatively affected if the upstream river is regulated, reducing the magnitude of high flow events (Kenyon et al., 2004; Burford et al., 2011). Eyre (2000) has proposed that estuaries of the wet and dry tropics/subtropics have four regime states throughout a typical year. During floods, freshwater flushes nutrients and sediments out to sea. This is followed by a recovery phase where turbidity begins to decrease, however low light availability prevents phytoplankton growth. In the medium flow phase, increasing light and nutrient availability stimulates phytoplankton biomass. Finally, in the dry season, phytoplankton become nutrient limited again, with a resulting decrease in biomass. This study therefore examined the role of freshwater nutrient inputs in stimulating phytopl...

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Section: Discussionsupporting

confidence: 51%

“…A second one-dimensional model was developed to simulate horizontal solute transport (Webster et al, 2005). This model averaged over the tides and solved the advection-diffusion equation.…”

Section: N and P Budgetsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Controls on phytoplankton productivity in a wet–dry tropical estuary

Burford

Webster

Revill

et al. 2012

Estuarine, Coastal and Shelf Science

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“…During our study period, maximum flow occurred in February and March with flow peaking at close to 60 000ml d À1 (690 m 3 s À1 ). When compared with the 11 years of data presented by Webster et al (2005), this flow is relatively minor. For example, flows of 30 000-40 000 m 3À s À1 have occurred earlier every few years.…”

Section: Introductionmentioning

confidence: 84%

“…The third and final stage is after a prolonged period of low flow when the estuary reaches a state where salinities close to seawater prevail along its length. Webster et al (2005) showed that the median flow within the Fitzroy estuary is 7 m 3 s À1 with a 25th percentile of only 0.7 m 3 s À1 , thus for much of the year there is little or no flow. During our study period, maximum flow occurred in February and March with flow peaking at close to 60 000ml d À1 (690 m 3 s À1 ).…”

Section: Introductionmentioning

confidence: 99%

Archaeal ammonia oxidizers and nirS-type denitrifiers dominate sediment nitrifying and denitrifying populations in a subtropical macrotidal estuary

et al. 2009

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Nitrification and denitrification are key steps in nitrogen (N) cycling. The coupling of these processes, which affects the flow of N in ecosystems, requires close interaction of nitrifying and denitrifying microorganisms, both spatially and temporally. The diversity, temporal and spatial variations in the microbial communities affecting these processes was examined, in relation to N cycling, across 12 sites in the Fitzroy river estuary, which is a turbid subtropical estuary in central Queensland. The estuary is a major source of nutrients discharged to the Great Barrier Reef nearshore zone. Measurement of nitrogen fluxes showed an active denitrifying community during all sampling months. Archaeal ammonia monooxygenase (amoA of AOA, functional marker for nitrification) was significantly more abundant than Betaproteobacterial (b-AOB) amoA. Nitrite reductase genes, functional markers for denitrification, were dominated by nirS and not nirK types at all sites during the year. AOA communities were dominated by the soil/sediment cluster of Crenarchaeota, with sequences found in estuarine sediment, marine and terrestrial environments, whereas nirS sequences were significantly more diverse (where operational taxonomic units were defined at both the threshold of 5% and 15% sequence similarity) and were closely related to sequences originating from estuarine sediments. Terminal-restriction fragment length polymorphism (T-RFLP) analysis revealed that AOA population compositions varied spatially along the estuary, whereas nirS populations changed temporally. Statistical analysis of individual T-RF dominance suggested that salinity and C:N were associated with the community succession of AOA, whereas the nirS-type denitrifier communities were related to salinity and chlorophyll-a in the Fitzroy river estuary.

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Biogeochemical Budgeting in Estuaries

Swaney

2011

Treatise on Estuarine and Coastal Science

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Estimating nutrient budgets in tropical estuaries subject to episodic flows

Cited by 15 publications

References 11 publications

Controls on phytoplankton productivity in a wet–dry tropical estuary

Controls on phytoplankton productivity in a wet–dry tropical estuary

Archaeal ammonia oxidizers and nirS-type denitrifiers dominate sediment nitrifying and denitrifying populations in a subtropical macrotidal estuary

Biogeochemical Budgeting in Estuaries

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