The influence of particle size on seston deposition in streams

Abstract

We investigated how particle size influences deposition and transport of fine particulate organic matter in streams. Field additions of very fine (VFPOM, 15-52 m), fine (FPOM,, and medium (MPOM, 107-250 m) detritus and live diatoms (Asterionella sp.) were used to quantify the longitudinal loss rate (k P ) of each material type and to derive estimates of mean transport distance (S P ) and field deposition velocity (v dep ). In all experiments, smaller particles deposited more slowly, and thus traveled farther, than larger size classes. Significant differences in k P were detected in four of seven paired FPOM and VFPOM particle additions. v dep estimates were neither equivalent nor closely associated with calculated quiescent water fall velocities (v fall ) for all size classes. Variation in S P and v dep of FPOM and VFPOM were strongly correlated across hydrological conditions (r ϭ 0.94 and 0.92, respectively). Variation in v dep was poorly associated with physical attributes of the stream. Transport distances were positively associated with the cross-sectional area of the transient storage zone (A S ) and the uptake length of water (S W ) for both size classes. We argue that local hydrological and benthic conditions establish a minimum rate of particle deposition and that departures from this rate due to gravitational forces begin to occur at particle diameters similar to the larger size classes used in this study (50-100 m).Fine particulate organic matter (FPOM, 53-106 m) often constitutes a large proportion of organic matter transported by streams (Naiman and Sedell 1979;Wallace et al. 1982;Minshall et al. 1983; Webster and Meyer 1997). FPOM movement in streams is envisioned as a series of transport

Temporal dynamics of seston: A recurring nighttime peak and seasonal shifts in composition in a stream ecosystem

“…Baseflow transport, though comprising a smaller proportion of the total load, delivers upstream POC to relatively close reaches downstream ). From measurements of particle deposition velocities (0.1 to 0.4 mm s 21 ; Thomas et al 2001), WCC mean baseflow water velocity (0.12 m s 21 ), and depth (0.10 m), we can calculate that particles travel between 31 to 124 m on average before they are deposited on the streambed. The short travel distance emphasizes the importance of local reach-scale dynamics on baseflow particle transport.…”

Mass transport of contaminated soil released into surface water by landslides (Göta River, SW Sweden)

“…Thomas et al (2001) found clear influence of fall velocity on deposition velocity for particulate organic matter and suggested that gravitational forces control the deposition for particles >100 µm. Hamm et al (2011) studied silt-sized particles in an open channel flow with permeable beds.…”

“…For fine material, the settling velocity will be low and the influence on the concentration distribution negligible. Thomas et al (2001) performed field measurements in two streams and found poor correlation between the calculated settling velocity and the deposition rate estimated from the collected data. Their assessment was that for sediment sizes below the range of 0.05 to 0.1 mm, gravitational effects might be small.…”

Toxins in transgenic crop byproducts may affect headwater stream ecosystems

“…After harvest, we measured transport distances by releasing painted corn leaves and cobs and measuring distance traveled before retention (24). We measured pollen transport during pollen shed by releasing stained corn pollen and calculating the average distance a grain traveled before settling (particle transport distance, S w ) (19,30). We estimated water transit time in the reach before pollen release by adding a solution of dissolved NaCl and following it with a conductivity meter.…”