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B. Peterson

Publications and source records attributed to B. Peterson.

6 recordsLinked to original sources
USGS2010

Inter-regional comparison of land-use effects on stream metabolism

1. Rates of whole-system metabolism (production and respiration) are fundamental indicators of ecosystem structure and function. Although first-order, proximal controls are well understood, assessments of the interactions between proximal controls and distal controls, such as land use and geographic region, are lacking. Thus, the influence of land use on stream metabolism across geographic regions is unknown. Further, there is limited understanding of how land use may alter variability in ecosystem metabolism across regions.2. Stream metabolism was measured in nine streams in each of eight regions (n = 72) across the United States and Puerto Rico. In each region, three streams were selected from a range of three land uses: agriculturally influenced, urban-influenced, and reference streams. Stream metabolism was estimated from diel changes in dissolved oxygen concentrations in each stream reach with correction for reaeration and groundwater input.3. Gross primary production (GPP) was highest in regions with little riparian vegetation (sagebrush steppe in Wyoming, desert shrub in Arizona/New Mexico) and lowest in forested regions (North Carolina, Oregon). In contrast, ecosystem respiration (ER) varied both within and among regions. Reference streams had significantly lower rates of GPP than urban or agriculturally influenced streams.4. GPP was positively correlated with photosynthetically active radiation and autotrophic biomass. Multiple regression models compared using Akaike's information criterion (AIC) indicated GPP increased with water column ammonium and the fraction of the catchment in urban and reference land-use categories. Multiple regression models also identified velocity, temperature, nitrate, ammonium, dissolved organic carbon, GPP, coarse benthic organic matter, fine benthic organic matter and the fraction of all land-use categories in the catchment as regulators of ER.5. Structural equation modelling indicated significant distal as well as proximal control pathways including a direct effect of land-use on GPP as well as SRP, DIN, and PAR effects on GPP; GPP effects on autotrophic biomass, organic matter, and ER; and organic matter effects on ER.6. Overall, consideration of the data separated by land-use categories showed reduced inter-regional variability in rates of metabolism, indicating that the influence of agricultural and urban land use can obscure regional differences in stream metabolism. ?? 2010 Blackwell Publishing Ltd.

Freshwater Biology↗
USGS2006

Denitrification across landscapes and waterscapes: A synthesis

Denitrification is a critical process regulating the removal of bioavailable nitrogen (N) from natural and human-altered systems. While it has been extensively studied in terrestrial, freshwater, and marine systems, there has been limited communication among denitrification scientists working in these individual systems. Here, we compare rates of denitrification and controlling factors across a range of ecosystem types. We suggest that terrestrial, freshwater, and marine systems in which denitrification occurs can be organized along a continuum ranging from (1) those in which nitrification and denitrification are tightly coupled in space and time to (2) those in which nitrate production and denitrification are relatively decoupled. In aquatic ecosystems, N inputs influence denitrification rates whereas hydrology and geomorphology influence the proportion of N inputs that are denitrified. Relationships between denitrification and water residence time and N load are remarkably similar across lakes, river reaches, estuaries, and continental shelves. Spatially distributed global models of denitrification suggest that continental shelf sediments account for the largest portion (44%) of total global denitrification, followed by terrestrial soils (22%) and oceanic oxygen minimum zones (OMZs; 14%). Freshwater systems (groundwater, lakes, rivers) account for about 20% and estuaries 1% of total global denitrification. Denitrification of land-based N sources is distributed somewhat differently. Within watersheds, the amount of land-based N denitrified is generally highest in terrestrial soils, with progressively smaller amounts denitrified in groundwater, rivers, lakes and reservoirs, and estuaries. A number of regional exceptions to this general trend of decreasing denitrification in a downstream direction exist, including significant denitrification in continental shelves of N from terrestrial sources. Though terrestrial soils and groundwater are responsible for much denitrification at the watershed scale, per-area denitrification rates in soils and groundwater (kg N·km −2 ·yr −1 ) are, on average, approximately one-tenth the per-area rates of denitrification in lakes, rivers, estuaries, continental shelves, or OMZs. A number of potential approaches to increase denitrification on the landscape, and thus decrease N export to sensitive coastal systems exist. However, these have not generally been widely tested for their effectiveness at scales required to significantly reduce N export at the whole watershed scale.

Ecological Applications↗
USGS2003

Sediment DIN fluxes and preferential recycling of benthic microalgal nitrogen in a shallow macrotidal estuary

Sediment -water fluxes of NH 4 + , NO 3 - , dissolved inorganic carbon, and O 2 were measured in cores collected from the upper Rowley River estuary , Massachusetts, and used to calculate rates of organic nitrogen (N) mineralization, nitrification, and coupled and direct denitrification (DNF). The cores contained 15 N label in benthic microalgae (BMA) and in NO 3 - in the overlying water as a result of an ongoing whole- estuary 15 NO 3 - enrichment study (NISOTREX II). The tracer allowed for estimation of gross NO 3 - regeneration in sediments and the contribution of BMA derived N to total mineralization. The mean mineralization rate between sites was 16.0 ± 2.0 mmol N m -2 d -1 . Approximately 13 to 56% of the mineralized N was nitrified at rates ranging from 1.8 to 10.1 mmol N m -2 d -1 . Total denitrification was dominated by direct DNF (3.6 mmol N m -2 d -1 ) furthest upstream, where NO 3 - concentrations were highest. Coupled DNF was most important (8.0 mmol N m -2 d -1 ) in the sediments with high nitrification and low water column NO 3 - . A gross NO 3 - flux from sediments to water of 0.9 to 2.1 mmol N m -2 d -1 was estimated from the isotope dilution of δ 15 NO 3 - in the overlying water of the cores. The isotope dilution seen in the cores was also detected as a deviation from conservative δ 15 NO 3 - mixing along estuarine transects. Incorporation of this NO 3 - regeneration into the DNF calculations effectively increased the estimate of direct DNF by up to 50% and decreased the coupled DNF estimate by up to 220%. Increasing δ 15 NH 4 + in the water of the cores indicated that the 15 N-labelled BMA were preferentially mineralized over bulk sediment organic N. Additional 15 N enrichments in the sediment bacterial biomarker diaminopimelic acid showed a link among 15 N-labeled BMA, active bacteria, and 15 NH 4 + released to the overlying water. Based on δ 15 NH 4 + enrichments in the cores, BMA accounted for approximately 50 to 100% of the N mineralized. An isotopic enrichment of δ 15 NH 4 + above background in the estuary was observed at a magnitude consistent with the core-based rates of BMA mineralization. These results provide further evidence that BMA are not unidirectional sinks for water column-dissolved organic nitrogen , but instead act to turn over N between sediments and estuarine water on the scale of days.

Marine Ecology Progress Series↗