Potential Sediment Denitrification Rates in Estuaries of Northern Gulf of Mexico

Abstract

The three-season average of sediment potential denitrification rates (PDRs) (i.e., NO, saturated; acetylene blockage method) for five study areas within urban bayous and bays in the Pensacola Bay area, Florida, ranged between 43 and 223 nmol of N g~' h" 1 . Average PDRs extrapolated to a unit area basis approximated 500 to 1000 (xmol of N m 2 h ' that are relatively high values but comparable to those where conditions for denitrification are favorable. A regression model, based on a larger number of measured environmental factors for the spring than fall and winter indicated that N(K + NOf concentrations explained most of the total variability (K 2 -. 27%; P < 0.003) in PDRs. The NO 2~ + NOf concentrations were also predictive of PDRs (R 2 ranged from 0.56-0.98; all /"-values <0.05) on four separate occasions for comparisons made within five study areas and three seasons. Sediment trace metal concentrations (e.g., Ni), based on published values, were high enough to cause reduction in PDRs through direct toxicity to denitrifiers at several stations. Sediment metals toxicities, based on published sediment quality guidelines, could occasionally cause a reduction in macrobenthic infaunal bioturbation and irrigation. Such a reduction could attenuate the flux of dissolved oxygen into sediments and cause a reduction in denitrification rates by limiting the coupled processes of nitrification and denitrification. Also, a reduction in the flux of NO, or NOf, a substrate for denitrification, into sediments can directly limit denitrification rates.

Nutrient cycling and fluxes in Beatrix Bay, Pelorus Sound, New Zealand

“…The range of potential denitrification was 13-828 ng N g -1 h -1 (mean ± SE = 417 ± 153 ng N g -1 h -1 ). These potential denitrification rates were similar to the maximum rate (V max ) found by Billen (1978) in North Sea sediments, and are comparable with denitrification rates in Delaware Inlet, New Zealand (Kaspar 1983), Chesapeake Bay (Kana et al 1998), Aarhus Bight, Denmark (Nielsen & Glud 1996), and Tomales Bay, California (Joye & Pearl 1994), but considerably less than in enriched estuaries such as the Great Ouse, England (Trimmer et al 1998), the Neuse River, North Carolina (Rizzo & Christian 1996), and around the Gulf of Mexico (RiveraMonroy & Twilley 1996;Flemer et al 1998), or Northern Hemisphere areas associated with intensive shellfish farming such as Thau Lagoon, France (Gilbert et al 1997).…”

Nitrate levels modulate denitrification activity in tropical mangrove sediments (Goa, India)

“…At 8-10 cm, the activity decreased to 81.25 (±22.58) μmol N 2 O-N m −2 h −1 . Flemer et al (1998) have reported relatively high potential denitrification rates in estuarine sediments ranging between 500 to 1,000 μmol N m −2 h −1 which were also limited by nitrate availability. Laverman et al (2007) have encountered maximum in situ rates two-fold lower than the maximum potential rate in surficial sediment indicating that in situ denitrification was nitrate limited.…”

The effects of drying on sediment nitrogen content in a Mediterranean intermittent stream: a microcosms study

“…%WFPS is directly related with microbial activity and has been proposed as a good indicator of soil biological properties, such as C and N-mineralization and soil microbial biomass (Franzluebbers, 1999). The % organic matter (%OM) of sediment samples was determined by loss on ignition (Felmer et al, 1998) by burning samples at 550°C for 4 h, expressed as a percentage of dry weight. All the measurements were made with three sediment subsamples per tank.…”