Abstract
Phosphorus (P) is an essential element for growth in aquatic ecosystems but the dynamics of phosphorus cycling within catchments is poorly constrained. The aim of this study was therefore to develop analytical tools to investigate the release of inorganic and organic phosphorus species in rivers and estuaries during resuspension events such as storm, wind and tidal induced turbulence. To achieve this aim, laboratory simulations using a mini-annular flume coupled with segmented flow analyser detection were performed. To collect SPM (suspended particulate matter), a specially designed specimen box was deployed in the River Tamar (Devon, UK). Inorganic and total phosphorus were determined using segmented flow analyser methods adapted for use with acidified persulfate digests. The segmented flow analyser had a detection limit (3 s.d.) of 0.53 μg P L-1 for inorganic P and 1.5 μg P L-1 for total P. The mini-annular flume provides a suitable method for laboratory simulations, e.g. we managed to get low blanks and good experimental reproducibility, and are also able to see changes in P species within analytical precision. Results showed that increase of shear stress (or SPM) caused release of inorganic P from sediment. This could be used as a fact to build a model to study P dynamics during resuspension events in the river and estuaries environment.
Highlights
IntroductionDissolved inorganic phosphorus (DIP) is the most important form of phosphorus because it can be directly taken up by phytoplankton; dissolved organic phosphorus (DOP) (e.g. phospholipids, phytic acid, ATP) usually cannot be directly utilized by phytoplankton, but can be transformed into a bioavailable inorganic form by physical, chemical or biological processes [2]
The suspended particulate matter (SPM) concentrations were in the range 0 - 400 mg·L−1, which are typical of concentrations found in the Tamar Estuary (40 - 300 mg·L−1 Langston et al, 2003), and the SPM concentration increased linearly with shear stress (R2 = 0.97)
The results suggest that P released from sediment/SPM during turbulent events will remain in the water column for a significant (>18 h) period in a bioavailable form, which has important implications for biomass uptake and growth
Summary
Dissolved inorganic phosphorus (DIP) is the most important form of phosphorus because it can be directly taken up by phytoplankton; dissolved organic phosphorus (DOP) (e.g. phospholipids, phytic acid, ATP) usually cannot be directly utilized by phytoplankton, but can be transformed into a bioavailable inorganic form by physical, chemical or biological processes [2]. Sediment represents both the largest sink and the largest source of P in aquatic systems [3] and the behavior of particle-associated molecules is closely linked with particle dynamics. Increased suspended particulate matter (SPM) concentrations during turbulent episodes in rivers and estuaries could enhance the release of DIP and DOP into the water column
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