The assessment of benthic phosphorus regeneration in an estuarine ecosystem model

Raaphorst, Wim van; Ruardij, P.; Brinkman, A.G.

doi:10.1016/0077-7579(88)90050-6

Cited by 45 publications

(16 citation statements)

References 29 publications

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“…This, in combination with N lost through denitrification, is a major reason that primary production in Narragansett Bay is predominantly N limited (Nixon et al 1980;Howarth 1988). On the other hand, the P released from sediments in Chesapeake Bay is less than the amount released during decomposition (Boynton and Kemp 1985), and there is evidence of P adsorption and storage in surface sediments in several other estuaries (van Raaphorst et al 1988;Koop et al 1990;Sundby et al 1992). Many of the differences in P uptake and release from sediments in both estuaries and lakes may be explained in part by the extent of eutrophication in those systems.…”

Section: Acknowledgmentsmentioning

confidence: 99%

Nitrogen as the limiting nutrient for eutrophication in coastal marine ecosystems: Evolving views over three decades

Howarth

Marino

2006

Limnology & Oceanography

1,176

733

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The first special volume of Limnology and Oceanography, published in 1972, focused on whether phosphorus (P) or carbon (C) is the major agent causing eutrophication in aquatic ecosystems. Only slight mention was made that estuaries may behave differently from lakes and that nitrogen (N) may cause eutrophication in estuaries. In the following decade, an understanding of eutrophication in estuaries proceeded in relative isolation from the community of scientists studying lakes. National water quality policy in the United States was directed almost solely toward P control for both lakes and estuaries, and similarly, European nations tended to focus on P control in lakes. Although bioassay data indicated N control of eutrophication in estuaries as early as the 1970s, this body of knowledge was treated with skepticism by many freshwater scientists and water-quality managers, because bioassay data in lakes often did not properly indicate the importance of P relative to C in those ecosystems. Hence, the bioassay data in estuaries had little influence on water-quality management. Over the past two decades, a strong consensus has evolved among the scientific community that N is the primary cause of eutrophication in many coastal ecosystems. The development of this consensus was based in part on data from whole-ecosystem studies and on a growing body of evidence that presented convincing mechanistic reasons why the controls of eutrophication in lakes and coastal marine ecosystems may differ. Even though N is probably the major cause of eutrophication in most coastal systems in the temperate zone, optimal management of coastal eutrophication suggests controlling both N and P, in part because P can limit primary production in some systems. In addition, excess P in estuaries can interact with the availability of N and silica (Si) to adversely affect ecological structure. Reduction of P to upstream freshwater ecosystems can also benefit coastal marine ecosystems through mechanisms such as increased Si fluxes.

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Section: Acknowledgmentsmentioning

confidence: 99%

Nitrogen as the limiting nutrient for eutrophication in coastal marine ecosystems: Evolving views over three decades

Howarth

Marino

2006

Limnology & Oceanography

1,176

733

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“…Thus van Raaphorst et al (1988) have described how the bottom sediments buffer the phosphate concentration in the Dutch Wadden Zee. They showed that phosphate is removed from the water column to the sediment in fall and winter when the phosphate concentration is high, and released in spring and summer when phytoplankton growth lowers the phosphate concentration.…”

Section: Methodsmentioning

confidence: 99%

The phosphorus cycle in coastal marine sediments

et al. 1992

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Approximately half of the sedimentation flux of particulate phosphorus in the Laurentian Trough in the Gulf of St. Lawrence is mobilized within the sediment and returned to the water column. In the oxidizing surface sediment, a major portion of the sedimentation flux of organic phosphorus is mineralized, and the released phosphate is partitioned between the pore water and surface adsorption sites. Surface-adsorbed phosphate is released to the pore water as needed to replace dissolved phosphate that escapes to the overlying water. Most of the phosphate is released deeper in the sediment column from iron oxides undergoing reduction. The nonmobilized phosphorus, which is buried with the accumulating sediment, appears to consist mostly of stable minerals such as apatite.The concentration of dissolved phosphate in sediment pore waters increases sharp!y across the sediment-water interface from 2 pmol PO, liter-l in the bottom water to 6+3 pmol PO, liter-' in the top centimeter, remains almost constant at this value down to 5-l 5-cm depth, and then increases rapidly with further depth. In the region of constant concentration, phosphate is buffered by adsorption-desorption equilibria with the sediment. The production rate of phosphate, the buffering capacity of the sediment, and the thickness of the diffusive boundary layer at the sediment-water interface control the shape of the pore-water profile.In the aquatic environment, dissolved phosphate is consumed during the growth of phytoplankton and is regenerated during bacterial decomposition of organic matter. Much of the regeneration takes place in the water, but in relatively shallow environAcknowledgments

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“…Even when PO, concentrations in the pore water of the oxidized surface sediment are only slightly higher than those in the bottom water, the combined effect of rapid adsorption and desorption may allow a very sharp gradient in dissolved PO, to be sustained near the sediment-water interface. This can result in a substantial flux of dissolved PO, to the overlying water (Van Raaphorst et al 1988;Van Rsaphorst and Kloosterhuis 1994).…”

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confidence: 99%

The role of adsorption in sediment-water exchange of phosphate in North Sea continental margin sediments

Slomp¹,

Malschaert²,

Raaphorst³

1998

Limnol. Oceanogr.

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159

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The effect of adsorption on the sediment-water exchange of PO, was investj gated in sediments from four different types of sedimentary environments in the southern and eastern North Sea in August 1991 and February 1992. Nonlinear adsorption isotherms for oxidized sediment from eight stations indicate that North Sea sediments differ widely in their capacity to adsorb PO,. A good correlation between the value of the adsorption coefficient and NH,-oxalate-extractable Fe was observed. A combination of the adsorption data with Porewater PO, profiles, solid phase results, and measured and calculated rates of sediment-water exchange of PO, for 15 stations in both August and February indicates that adsorption plays an important role in controlling sediment-water exchange of PO, during at least a part of the year in three of the four North Sea environments. At most stations, PO, adsorption constrains the flux of PO, to the overlying water. At one station in the depositional environment of the Skagcrrak, however, desorption is responsible for the maintenance of a flux of PO, to the overlying water. A one-dimensional reactiondiffusion model, describing Porewater PO, and solid phase P profiles, was de*deloped and applied to results for two stations. The model results show that both enhanced retention and enhanced release of PO, can be adequately described when simultaneous equilibrium and first-order kinetic reversible adsorptive reactions are assumed.A substantial proportion (lo-50%) of pelagic primary production reaches the sea floor in continental margin environments (Jorgensen 1983). When this organic material is mineralized in the sediment, a release of dissolved PO, to the pore water results. This PO, can be retained in the sediment, but it may also escape to the overlying water, where it once again can become available for uptake by phytoplankton (e.g. Howarth et al. 1995).Phosphorus (P) retention and release in marine sediments on short time-scales are usually considered to be redox-dependent. When an oxidized surface layer is present, substantial amounts of PO, can be retained in the sediment through adsorption to Fe oxides (e.g. Krom and Berner 1980b, 198 1;Sundby et al. 1992;Jensen et al. 1995). This adsorption process generally results in a buffering of Porewater PO, concentrations to low values in the oxidized sediment zone (Froelich 1988;Sundby et al. 1992), thus allowing only limited diffusive transport of PO, to the overlying water. When, in contrast, the oxidized surface layer is thin or absent, the PO, released from organic matter and from Fe oxides upon their reduction can escape to the overlying water. This was first described for lake sediments by Einsele (1936) and Mortimer (1941Mortimer ( , 1942. Redox-dependent sediment PO, re-I Present address: Department of Geochemistry, Institute of Earth Sciences, Utrecht University, Budapcstlaan 4, 3584 CD Utrecht, The Netherlands. AcknowledgmentsWe thank the crew of RV Pehgia for their help during the cruises and A. J. J. Sandcc for the grain size analy...

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The assessment of benthic phosphorus regeneration in an estuarine ecosystem model

Cited by 45 publications

References 29 publications

Nitrogen as the limiting nutrient for eutrophication in coastal marine ecosystems: Evolving views over three decades

Nitrogen as the limiting nutrient for eutrophication in coastal marine ecosystems: Evolving views over three decades

The phosphorus cycle in coastal marine sediments

The role of adsorption in sediment-water exchange of phosphate in North Sea continental margin sediments

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