Extreme Eutrophication in Shallow Estuaries and Lagoons of California Is Driven by a Unique Combination of Local Watershed Modifications That Trump Variability Associated with Wet and Dry Seasons

Kennison, Rachel L.; Fong, Peggy

doi:10.1007/s12237-013-9687-z

Cited by 15 publications

(11 citation statements)

References 95 publications

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“…Over the past few decades, reactive nitrogen production has increased by 120%, and global nitrogen overload has become an emerging environmental issue in this century [Piña-Ochoa and Álvarez-Cobelas, 2006;Galloway et al, 2008;Virdis et al, 2010;Bu et al, 2011]. Increasing input of nitrogen (mainly in the form of nitrate) is an important driver of ecoenvironmental questions in estuarine and coastal ecosystems [Seitzinger and Sanders, 1997;Vermaat et al, 2012;Kennison and Fong, 2014], by altering food-web structure, decreasing biodiversity, causing widespread anoxia, and increasing frequency of algal blooms [Carstensen et al, 2007;Hautier et al, 2009;Howarth et al, 2011]. An improved understanding of nitrogen transformation is thus required to assess nitrogen fate and control nitrogen pollution in these aquatic environments.…”

Section: Introductionmentioning

confidence: 99%

Dissimilatory nitrate reduction processes and associated contribution to nitrogen removal in sediments of the Yangtze Estuary

et al. 2015

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Dissimilatory nitrate reduction processes, including denitrification, anaerobic ammonium oxidation (ANAMMOX), and dissimilatory nitrate reduction to ammonium (DNRA), play an important role in controlling the nitrate dynamics and fate in estuarine and coastal environments. We investigated potential rates of denitrification, ANAMMOX, and DNRA in the sediments of the Yangtze Estuary via slurry incubation experiments combined with isotope-tracing techniques to reveal their respective contributions to total nitrate reduction in this hypereutrophic estuarine ecosystem. Measured rates of denitrification, ANAMMOX, and DNRA ranged from 0.06 to 4.51 μmol N kg À1 h À1, 0.01 to 0.52 μmol N kg À1 h À1, and 0.03 to 0.89 μmol N kg À1 h À1, respectively. These potential dissimilatory nitrate reduction process rates correlated significantly with salinity, sulfide, organic carbon, and nitrogen. Denitrification contributed 38-96% total nitrate reduction in the Yangtze Estuary, as compared to 3-45% for DNRA and 1-36% for ANAMMOX. In total, the denitrification and ANAMMOX processes removed approximately 25% of the external inorganic nitrogen transported annually into the estuary. In contrast, most external inorganic nitrogen was retained in the estuary and contributes substantially to the severe eutrophication of the Yangtze Estuary.

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Section: Introductionmentioning

confidence: 99%

Dissimilatory nitrate reduction processes and associated contribution to nitrogen removal in sediments of the Yangtze Estuary

et al. 2015

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“…Estuaries are highly productive ecosystems that support diverse communities and are subject to high resource loading, making them ideal systems to examine the effects of natural and anthropogenically enhanced subsidies. In estuarine systems, both natural pulses of nutrients, such as upwelling and nitrogen fixation (Kiirikki and Blomster , Brown and Ozretich ) and anthropogenic enrichment (Kennison and Fong ) stimulate blooms of drift macroalgae that can raft onto benthic communities (Schein et al ). These macroalgal subsidies support diverse terrestrial (Spiller et al ) and aquatic (Kennish and Williams , Tallis ) communities including infauna and epifauna (Marsden and Maclaren , Bishop and Kelaher ).…”

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confidence: 99%

The good, the bad and the Ulva: the density dependent role of macroalgal subsidies in influencing diversity and trophic structure of an estuarine community

Green¹,

Fong²

2015

Oikos

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Worldwide, ecological subsidies enhance ecosystem productivity and therefore trophic support for greater biodiversity of taxa. While studies in terrestrial and aquatic ecosystems demonstrate that the magnitude of subsidies into ecosystems diff ers widely, the thresholds where subsidies may switch from exerting positive to negative eff ects are poorly understood. In estuaries, eutrophication promotes drift macroalgae that deposit on the benthos, cover intertidal fl ats for months and serve as pressed resource subsidies for benthic consumers. We hypothesized there would be a critical threshold of macroalgal biomass where ecosystem-level eff ects would turn from positive to negative. We used manipulative fi eld experiments varying macroalgal mat thickness (0.5, 1.5 and 4 cm) over eight weeks and quantifi ed eff ects on macrofauna on a lagoon mudfl at in California. We documented that plots with mat depths of 0.5 and 1.5 cm had higher diversity by supporting both surface feeding and burrowing detritivores. Non-metric multidimensional scaling showed that the benthic community diverged with mat depth over the course of the experiment. After eight weeks, surface deposit feeders were associated mainly with 0.5 cm macroalgal subsidies, whereas subsurface deposit feeding capitellids were closely linked with 4 cm mats. Depth profi les of pore water sulfi de concentration collected from 4 cm mats were 7622 Ϯ 5294 μ M, mean Ϯ SE, (mean of means across depth profi les), whereas 0.5 cm treatments resulted in sulfi de concentrations that were 0.25% of the 4 cm treatments. Th is suggests that the mechanism of negative eff ects for elevated macroalgal subsidies was development of anoxic conditions promoting sulfi de accumulation. Th us, our study was the fi rst to fi nd a critical threshold, or ecological tipping point, beyond which the eff ects of anthropogenically enhanced subsidies to estuarine mudfl at communities switched from positive to negative and to describe the mechanism by which elevated subsides altered the abiotic environment and likely reduced ecosystem functioning.

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“…Similarly hypereutrophied estuaries with more than 20 µmol L −1 phosphate and or 300 µmol L −1 nitrate have been found in all of the main Israeli coastal streams , in Lebanon (Baydoun et al, 2016), California (Kennison Krista Kamer and Fong, 2003;Kennison and Fong, 2014), and Spain (Velasco et al, 2006). The combination of arid conditions and increased anthropogenic water demand is likely to lead to the spreading of estuarine hypereutrophication (Kennison and Fong, 2014). Anecdotal observations suggest that micro-estuaries also exist in many other countries but hard data regarding the status of those systems is hard to obtain, likely due to the lack of awareness and resources for monitoring programs.…”

Section: Introductionmentioning

confidence: 85%

“…Like many micro-estuaries (and many larger estuaries) in the region and elsewhere, most of the natural freshwater sources in its catchment area have been captured for human use and the residual flow is currently dominated by treated wastewater which makes the system hypereutrophied (Suari et al, 2017). Similarly hypereutrophied estuaries with more than 20 µmol L −1 phosphate and or 300 µmol L −1 nitrate have been found in all of the main Israeli coastal streams , in Lebanon (Baydoun et al, 2016), California (Kennison Krista Kamer and Fong, 2003;Kennison and Fong, 2014), and Spain (Velasco et al, 2006). The combination of arid conditions and increased anthropogenic water demand is likely to lead to the spreading of estuarine hypereutrophication (Kennison and Fong, 2014).…”

Section: Introductionmentioning

confidence: 92%

“…Climate change is expected to cause poleward movement of arid climate zones (Rubel and Kottek, 2010) which will cause expansion of arid region into more populated regions that are currently situated in temperate climate zones. This spread is expected to increase the demand for freshwater and increase the ratio of treated to natural water discharge into coastal stream and estuaries and hence to their eutrophication (Kennison and Fong, 2014). Evidence of this process is described by Ludwig et al (2009).…”

Section: Sandbar Breach Effectsmentioning

confidence: 99%

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Sandbar Breaches Control of the Biogeochemistry of a Micro-Estuary

et al. 2019

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Micro-estuaries in semi-arid areas, despite their small size (shallow depth of a few meters, length of a few kilometers, and a surface area of less than 1 km 2 ) are important providers of ecosystem services. Despite their high abundance, tendency to suffer from eutrophication and vulnerability to other anthropogenic impacts, such systems are among the least studied water bodies in the world. In low tidal amplitude regions, micro-estuaries often have limited rate of sea-river water exchange, somewhat similar to fjord circulation, caused by a shallow sandbar forming at the coastline. The longterm study, we report here was inspired by the idea that, due to their small size and low discharges regime, relatively small interventions can have large effects on micro-estuaries. We used a stationary array of sensors and detailed monthly water sampling to characterize the Alexander estuary, a typical micro-estuary in the S.E. Mediterranean, and to identify the main stress factors in this aquatic ecosystem. The Alexander micro-estuary is stratified throughout the year with median bottom salinity of 18 PSU. Prolonged periods of hypoxia were identified as the main stress factor. Those were alleviated by breaching of the sandbar at the estuary mouth by sea-waves or stormwater runoff events (mostly during winter) that flush the anoxic bottom water. Analysis of naturally occurring sandbar breaches, and an artificial breach experiment indicate that the current oxygen consumption rate of the Alexander micro-estuary is too high to consider sandbar breaches as a remedy for the anoxia. Nevertheless, it demonstrates and provides the tools to assess the feasibility of small-scale interventions to control micro-estuaries hydrology and biogeochemistry.

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Extreme Eutrophication in Shallow Estuaries and Lagoons of California Is Driven by a Unique Combination of Local Watershed Modifications That Trump Variability Associated with Wet and Dry Seasons

Cited by 15 publications

References 95 publications

Dissimilatory nitrate reduction processes and associated contribution to nitrogen removal in sediments of the Yangtze Estuary

Dissimilatory nitrate reduction processes and associated contribution to nitrogen removal in sediments of the Yangtze Estuary

The good, the bad and the Ulva: the density dependent role of macroalgal subsidies in influencing diversity and trophic structure of an estuarine community

Sandbar Breaches Control of the Biogeochemistry of a Micro-Estuary

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