Effect of seasonal sediment storage in the lower Mississippi River on the flux of reactive particulate phosphorus to the Gulf of Mexico

Abstract

The annual surface water flux of total reactive (i.e., potentially bioavailable) particulate P from the Mississippi River was estimated by measuring the reactive (including labile, iron, organic, and calcium bound) and nonreactive (detrital) P phases in suspended particulates in the Mississippi River. In addition, the transformation of the major sediment P phases resulting from seasonal channel storage and resuspension was examined. Samples were collected during five cruises over 1 yr at marine and riverine sites. Solid-phase and pore-water nutrients were quantified, and solid-phase P pools were measured using a sequential extraction technique. These results indicate that the Mississippi River exports 134 ϫ 10 6 kg yr Ϫ1 of total reactive P via surface water. Seasonal hydrological forcing controlled the variability in major P phases found in channel sediments through hydrodynamic sorting. Although the 6-9-month time period during which sediments were stored in the river channel was sufficient to see evidence of early diagenesis in the pore waters, no significant net effect was seen on major P phase distribution. The loss of a significant percentage of labile and iron-bound P appears to be occurring only as these riverine sediments are deposited and reworked on the continental shelf.Phosphorus is an important macronutrient that is thought to limit marine primary productivity, particularly on geological timescales (Holland 1994;Tyrell 1999). For this reason, the marine P budget has been the subject of intense study over the past 3 decades, and much effort has gone into estimating inventories and source and sink terms in the budget (Froelich et al.

Impact of Suspended Inorganic Particles on Phosphorus Cycling in the Yellow River (China)

“…30 The Fe−P and OP phase are considered to be most important in the buffering of DIP in natural waters. 2 In comparison, particulate matter in the Nile and Mississippi Rivers contains 43−46% Fe−P 10,31 and in the Amazon River contains 28−33%. 32 The Yangtze River value is closest to the Yellow River with 18%.…”

Chromophoric Dissolved Organic Matter and Dissolved Organic Carbon from Sea-Viewing Wide Field-of-View Sensor (SeaWiFS), Moderate Resolution Imaging Spectroradiometer (MODIS) and MERIS Sensors: Case Study for the Northern Gulf of Mexico

“…The measured DOC concentration was 218. 50 [58] and the associated high DOC [59] pore waters in northern Gulf of Mexico shelf sediments. The better retrieval of a CDOM (412) using R rs (510)/R rs (560) for MERIS than for MODIS (the percentage differences of 16% for MERIS and of 24% for MODIS) could be attributed to the use of the 510 nm band in constructing the CDOM algorithm which is less affected by chlorophyll-a than the 488 nm band used in the MODIS CDOM algorithm.…”

Phosphorus Dynamics in the Water Column and Sediments of Barnegat Bay, New Jersey

“…Fe-P decreased in Mississippi River sediments as they were transported from river to continental shelf (Sutula, Bianchi, and McKee, 2004). Similarly, Fe-P decreased from freshwater to mesohaline water of the Patuxent River, a subestuary of the Chesapeake Bay (Hartzell, Jordan, and Cornwell, 2010).…”

“…Phosphorus release into sediment porewater, and subsequent flux to the overlying water column is associated with changes in pH (Seitzinger, 1991) and anoxic conditions (Callendar, 1982;Sundareshwar and Morris, 1999) that facilitate the dissolution of Fe-P and Ca-P. A decrease in sediment Fe-P along a river to ocean gradient was associated with increasingly anoxic conditions (Adhikari et al, 2015;Sutula, Bianchi, and McKee, 2004). Changes in the ionic composition in sediments, usually associated with changes in salinity, can alter sorption of Ls-P on sediment particles (Fox, 1989;Hawke, Carpenter, and Hunter, 1989;Sundareshwar and Morris, 1999;Weston, Dixon, and Joye, 2006).…”