Transport dynamics of fine particulate organic matter in two Idaho streams

Abstract

Natural suspended fine particulate organic matter (FPOM, was labeled with 14C and reinjected to estimate transport distances in the water column and retention times within the sediments of two Idaho streams. Transport of labeled FPOM particles declined exponentially with downstream distance. yielding mean transport distances of 800 and 580 m in Smiley Creek in 1989 and 1990 at a mean water velocity of 0.27 m ss' and mean depth of 0.34 m in both years, and a distance of 630 m in the upper Salmon River at a mean velocity of 0.29 m s ' and a depth of 0.14 m. These travel distances are equivalent to vertical deposition velocities of 0.7-l .6 mm s I, or -7-12% of the temperature-corrected quiescent-water fall velocities of the FPOM particles. The estimated deposition flux of -1.5 g (AFDM) m 1 d ' would turn over the standing stock of 0.8 g m 1 in surficial sediments twice daily.Sampling of benthic FPOM 24 h after release indicated that -99% of the 14C-labeled FPOM initially deposited in the 1,005-m study reach had been resuspended and exported; subsequent clearing was much slower. An advection-dispersion model satisfactorily simulated the deposition of 14C-labeled particles and their subsequent resuspension and export from the reach. Model-estimated retention times were 1.5-3 h for 99% of deposited sediments and 17 d for the remaining 1%.Thus, particles in surficial sediments exchange rapidly with the water column and migrate downstream several kilometers per day in alternating deposition and resuspension events. These results support the overall concept that conditions throughout a river system are strongly connected longitudinally and that OM introduced in headwater reaches can be transported large distances for later use or storage elsewhere in the river or for eventual export to estuaries. AcknowledgmentsThis work was performed under NSF grant BSR 88-178 19. Many people contributed to the successful labor-intensive field studies; they include Douglas Andrews, M. Arunachalam, James Check, Paul Dey, Peter Koetsier, Deron Lawrence, Michael McIntyre, Janet Mihuc, Tim Mihuc, Judy Minshall, Susannah Minshall, Dan Misner, Gregory Mladenka, Bruce Olenick, Christopher Robinson, George Watters, and the students and associates of the Community School in Ketchum, Idaho. Special recognition is due to C. Robinson for implementing field activities, G. Mladenka for developing dye and particle delivery systems, D. Lawrence for determining rhodamine, and M. Arunachalam and P. Dey for characterizing FPOM and determining respiratory loss of radioactive label. Don Edwards performed the labeling of the FPOM and radioanalyses of the transport samples. Benthic radioanalyses were done by IT Analytical Services. Kathy Lahala did the SEM photography. The manuscript was improved by the comments of the reviewers.

Meiofauna constitute a considerable portion of invertebrate drift among moss-rich patches within a karst hydrosystem

“…This observation diverges from many previous findings on particle transport that showed a strong positive relationship among hydrological predictors (i.e., discharge, flow velocity, shear stress) and transported PM (Maciolek 1966;Naiman & Sedell 1979;Wilcox et al 2008). Besides water column/near-bed hydrological conditions, particle transport in streams is greatly affected by initial benthic material distribution, substratum and channel (geo)morphology, complexity of in-stream retention structures, and biological activity (Cushing et al 1993;Cordova et al 2008;Small et al 2008). It appears that the crucial control mechanism of the in-stream transport capacity is the stream's ability for material retention and resuspension.…”

Deposition, benthic residence, and resuspension of fine organic particles in a mountain stream

“…This approach, however, implicitly assumes that benthic POM in streams and rivers consists of a well-mixed pool that continually and thoroughly exchanges with the overlying suspended POM, and does not address the questions of how frequently exchanges occur and whether the exchange involves the entire stock of benthic POM. Tracer additions of 14 C-labeled natural seston (Cushing et al 1993;Minshall et al 2000) and of surrogates such as spores (Wanner and Pusch 2000), corn pollen (Georgian et al 2003), bacteria (Hall et al 1996), and yeast (Paul and Hall 2002) have shown that there is a rapid and continual deposition of fine particles onto the streambed. The delivery of particles to the bed appears to be governed more by turbulence than by gravitational settling (Hall et al 1996;McNair et al 1997;Thomas et al 2001).…”

“…The ''turnover length'' for a form of organic carbon, or the downstream distance it travels until it is mineralized, can be represented as the product of its biological turnover time and downstream velocity (Newbold et al 1982;Webster et al 1999). Organic particles move downstream as a series of saltations interspersed by stationary periods in the streambed (Cushing et al 1993;Webster et al 1999), so that they migrate downstream at a velocity far slower than that of the Values are averages for the reach unless otherwise stated. From Minshall et al (2000).…”

The influence of filter‐feeding benthic macroinvertebrates on the transport and deposition of particulate organic matter and diatoms in two streams

“…Recently, studies of POM transport and deposition have been conducted using experimental additions of radioactively labeled natural detritus (Cushing et al 1993;Minshall et al 2000;Thomas et al in press), seston analogs (Miller and Georgian 1992;Webster et al 1999), and fluorescently labeled bacteria (Hall et al 1996). Cushing et al (1993) and Minshall et al (2000) observed total instream loss rates ranging from 0.15 to 17.14% per longitudinal meter for POM between 52 and 106 m in size. These values are equivalent to downstream transport distances, S P , of 5.8-667 m, where S P equals the inverse of the longitudinal loss rate (S P ϭ 1/k P ).…”