Presence Of Fine Sediment Research Articles

Gravel washing as a lacustrine spawning habitat restoration method for smallmouth bass

Smallmouth bass (Micropterus dolomieu) spawn on gravel and cobble in the littoral zone of lakes that may become degraded by the presence of fine sediments and decomposing organic matter. Substrate size and composition have been identified as important variables for nest site selection by male smallmouth bass. We tested whether ‘cleaning’ substrate by removing sediment with a pressure washer would increase the number of bass nests or the average total length (mm) of nesting smallmouth bass in selected areas of Big Rideau Lake, Ontario, Canada the following year using a before-after control-impact design. Treatment was not a significant predictor of nest abundance or average male length. Considering the strength of the experimental design it is reasonable to conclude that this intervention failed to enhance spawning substrate for smallmouth bass. Understanding the factors that maintain productive spawning sites for smallmouth bass is important to restoration effectiveness and determining where habitat enhancement will provide the greatest benefits.

Uncertainties in Models Predicting Critical Bed Shear Stress of Cohesionless Particles

Our data show large scatter in the critical Shields stress values for initial sediment motion. The main sources of dispersion are related to the methodological procedures defining the inception of movement (i.e., visual observations or extrapolation of sediment transport rate) and to the estimation of the bed shear stress. The threshold for sediment motion varies with many factors related not only to grain size but also to bed composition (e.g., presence of fine sediments in a coarse matrix), arrangement (e.g., bed roughness, grain orientation, and characteristic lengths of bed structures) and slope. New models to estimate the critical Shields number are proposed using grain size or bed slope or a combination of both. Model parameters and uncertainty are estimated through Bayesian inference using prior knowledge of these parameters and measured data. Apart from the uncertainty in observations, two types of uncertainty can be evaluated: one related to the parameter estimation (i.e., parametric) and one related to the choice of the model (i.e., structural). Finally, a four-parameter model based on the grain size and bed slope yields the best results and demonstrates potential interaction between these two parameters. Model uncertainty, however, remains large, which indicates that other input parameters may be needed to improve the proposed model.

First occurrence of Tiaracrinus (Crinoidea, Zophocrinidae) in the Devonian of Iberia: Biostratigraphical, palaeoecological, and palaeogeographical implications

Representatives of the crinoid genus Tiaracrinus are known from the Lochkovian to Eifelian (Early–Middle Devonian) of several countries, in Europe and North Africa. In this work, we describe the first occurrence of this taxon in the Devonian period of Iberian Massif (Iberia). Here, we report three specimens (two from the São Pedro da Cova region within Valongo anticline in northwestern Portugal and one from the Cantabrian Mountains in northern Spain), which are described to the type species Tiaracrinus quadrifrons. These new fossil findings provide new knowledge about the stratigraphic and geographic distribution of the genus Tiaracrinus and species T. quadrifrons. The co‐occurrence of T. quadrifrons in the Devonian outcrops of Valongo anticline also more precisely constrains the Devonian formations in age (Emsian–Eifelian) in that Portuguese region. In the palaeoecological and palaeoenvironmental context, this species coexisted with other crinoid species and representatives of several other groups of marine benthic invertebrates in a shallow water coral reef environment, with oxygenated substrates and regular salinity levels (mixoeuhaline environment). In addition, the presence of fine sediments with ripples suggests a low velocity current enough to reorient concentrations of tentaculite shells.

Potential application of oil-suspended particulate matter aggregates (OSA) on the remediation of reflective beaches impacted by petroleum: a mesocosm simulation.

This paper presents the oil-suspended particulate matter aggregate (OSA) resulted from the interaction of droplets of dispersed oil in a water column and particulate matter. This structure reduces the adhesion of oil on solid surfaces, promotes dispersion, and may accelerate degradation processes. The effects of the addition of fine sediments (clay + silt) on the formation of OSA, their impact on the dispersion and degradation of the oil, and their potential use in recovering reflective sandy beaches were evaluated in a mesoscale simulation model. Two simulations were performed (21days), in the absence and presence of fine sediments, with four units in each simulation using oil from the Recôncavo Basin. The results showed that the use of fine sediment increased the dispersion of the oil in the water column up to four times in relation to the sandy sediment. There was no evidence of the transport of hydrocarbons in bottom sediments associated with fine sediments that would have accelerated the dispersion and degradation rates of the oil. Most of the OSA that formed in this process remained in the water column, where the degradation processes were more effective. Over the 21days of simulation, we observed a 40% reduction on average of the levels of saturated hydrocarbons staining the surface oil.

Interactions between fine-grained sediment delivery, river bed deposition and salmonid spawning success

Abstract. Salmonids clean river bed gravels to lay their eggs. However, during the incubation period fine sediment infiltrates the bed. This has been found to limit the success of salmonid spawning, as fine sediment reduces gravel permeability resulting in intra-gravel flow velocities and O2 concentrations decreasing. The success of salmonid spawning is therefore a function of the coincidence of fine sediment delivery and the development of the salmonid eggs. The presence of fine sediment also exerts sub-lethal effects on the rate of egg development with a negative feedback slowing and extending the incubation process meaning the eggs are in the gravels for longer and susceptible to more potential sediment delivery events. The SIDO (Sediment Intrusion and Dissolved Oxygen)-UK model is a physically-based numerical model which simulates the effect of fine sediment deposition on the abiotic characteristics of the salmonid redd, along with the consequences for egg development and survival. This model is used to investigate the interactions and feedbacks between the timing and concentrations of suspended sediment delivery events, and the deposition of fine sediment within the gravel bed, and the consequences of this on the rate of egg development and survival. The model simulations suggest that egg survival is highly sensitive to suspended sediment concentrations, particularly to changes in the supply rate of sand particles. The magnitude, frequency and specific timing of sediment delivery events effects egg survival rates. The modelling framework is also used to investigate the impact of the rate of gravel infilling by sediment. The hypotheses of continual, discrete event and non-linear decline in the rate of infilling are investigated.

Intrusion of fine sediments into river bed and its effect on river environment – a research review

Fine sediments enter into the river through various sources such as channel bed, bank, and catchment. It has been regarded as a type of pollution in river. Fine sediments present in a river have a significant effect on river health. Benthic micro-organism, plants, and large fishes, all are part of food chain of river biota. Any detrimental effect on any of these components of food chain misbalances the entire riverine ecosystem. Numerous studies have been carried out on the various environmental aspects of rivers considering the presence of fine sediment in river flow. The present paper critically reviews many of these aspects to understand the various environmental impacts of suspended sediment on river health, flora and fauna.

Effect of fine sediments on river hydraulics – a research review

Fine sediments that join rivers from various channel and non channel sources considerably affect on the hydraulics of the river. The hydraulics of river carrying water with fine sediment has a different fluid and flow characteristics as compared to that carrying clear water. Basic fluid properties like viscosity and density and flow properties like resistance to flow, bed load carrying capacity, etc. are affected by the presence of fines in suspension. Several studies have been carried out to understand the changes associated with the presence of fine sediment in flow. The present paper presents a comprehensive review of these studies.

Superficial distribution of aromatic compounds and geomicrobiology of sediments from Suruí Mangrove, Guanabara Bay, RJ, Brazil

The distribution of selected aromatic compounds and microbiology were assessed in superficial sediments from Suruí Mangrove, Guanabara Bay. Samples were collected at 23 stations, and particle size, organic matter, aromatic compounds, microbiology activity, biopolymers, and topography were determined. The concentration of aromatic compounds was distributed in patches over the entire mangrove, and their highest total concentration was determinated in the mangrove's central area. Particle size differed from most mangroves in that Suruí Mangrove has chernies on the edges and in front of the mangrove, and sand across the whole surface, which hampers the relationship between particle size and hydrocarbons. An average @ 10% p/p of organic matter was obtained, and biopolymers presented high concentrations, especially in the central and back areas of the mangrove. The biopolymers were distributed in high concentrations. The presence of fine sediments is an important factor in hydrocarbon accumulation. With high concentration of organic matter and biopolymers, and the topography with chernies and roots protecting the mangrove, calmer areas are created with the deposition of material transported by wave action. Compared to global distributions, concentrations of aromatic compounds in Suruí Mangrove may be classified from moderate to high, showing that the studied area is highly impacted.

Assesment of Trace Elements and Organic Pollutants from a Marine Oil Complex into the Coral Reef System of Cayo Arcas, Mexico

Possible contaminants produced by the Petroleos Mexicanos (PEMEX) marine oil complex in the vicinity of the Cayo Arcas (Mexico) coral reef ecosystem were evaluated by analyzing sediments and sea water for hydrocarbons and metal elements. We found that the concentrations of aliphatic hydrocarbons in the sea water were generally low, with the highest values detected near the oil station; the concentration of polycyclic aromatic hydrocarbons (PAHs) was generally below the detection limit. The hydrocarbons found in the sediments seem to have a pyrogenic origin, and were probably produced by marine traffic in the study area. The total PAH concentration did not exceed the NOAA criteria, although levels of some individual PAHs did. The only metal detected in the sea water at high concentrations was nickel. The Ni/V ratio in the sediments indicates the contribution of crude oil to the system. The high content of Ni and Zn was attributed to the ballast waters from the oil tankers that load at the station's monobuoys. The presence of fine sediments that commonly originate from terrestrial ecosystems supported this assumption.

Texture‐based image segmentation applied to the quantification of superficial sand in salmonid river gravels

AbstractThe presence of fine sediment in river gravels is widely recognized as being detrimental to salmonid habitat quality. In order to facilitate quantification of sand presence at larger scales, this paper presents an application of image processing allowing for rapid and accurate assessments of superficial sand presence in dry exposed fluvial gravels. Images for the process are acquired with a 35 mm SLR film camera and then scanned with a desktop scanner. Texture‐based segmentation is then applied to differentiate between sand and clast areas. Results show that the method is accurate and therefore it offers an alternative to bulk sampling in cases where rapid assessments of sand presence are required. Copyright © 2005 John Wiley & Sons, Ltd.

Macroinvertebrates in neotropical streams: richness patterns along a catchment and assemblage structure between 2 seasons

We investigated macroinvertebrate richness in 10 streams of different sizes within the Carmo River catchment in Brazil. Specifically, we tested 2 predictions of the river continuum concept (RCC): 1) within the catchment, mid-sized streams (orders 3–4) have the richest biota, and 2) macroinvertebrate assemblage structure is more stable during the dry season than during the rainy season when natural spates are frequent. We sampled the streams using individual stones as sampling units. Observed and estimated values of richness did not follow the hump-shaped pattern of richness along a gradient of stream size as predicted by the RCC; the richest streams were smaller than those predicted. No difference in assemblage structure between seasons was found on the basis of observed and estimated richness or abundance. The similarity in assemblage structure between the rainy and dry seasons was also supported by multivariate analysis. Observed richness and species composition (reflected in multivariate analysis) were strongly correlated to stream size and the presence of fine sediments over rocks. Assemblage structure in these streams seems to be deterministic, in that richness and species composition are related to physical habitat characteristics.

The structure and sedimentology of relict talus, Knockan, Assynt, N.W. Scotland

A 5 m high section through a talus accumulation reveals a thin layer of openwork debris overlying a predominantly clast‐supported diamicton. Sedimentological and petrological analyses show that the diamicton is composed of rockfall clasts and fines derived by granular disaggregation of the rockwall. Structural discontinuities and fabric analyses indicate periodic redistribution of sediment by debris flow, facilitated by the presence of fine sediment. The characteristics of the deposit thus favour models of talus development that envisage both rockfall accumulation and periodic downslope redistribution of debris, rather than steady‐state accumulation of clasts by discrete rockfall events.

Introduction and Spread of Mangroves in the Hawaiian Islands

Introduction and Spread of Mangroves in the Hawaiian Islands Lyndon Wester* The terrestrial flora of Hawaii was derived from a small number of ancestral species as a result of the archipelago's remote location. Great expanses of open ocean separate Hawaii from continents and other islands, and thus water has acted as an effective barrier even to many widespread drift species whose propagules can float and withstand long immersion in seawater. The intertidal zone in Hawaii lacked vascular plants entirely despite the availability of habitats suitable for many of them (Guppy 1906, Egler 1942). The introduction and subsequent naturalization of mangroves and other exotic species has produced significant changes in the coastal environments. Mangroves are opportunist trees that colonize the tidal zone of tropical coasts. The most extensive stands occur on aggrading shores which receive sediments from large drainage systems, but small colonies also can be found on limestone coasts, coral atolls, sand beaches, and lagoons, suggesting that protection from wave action, rather than the presence of fine sediments, is a prerequisite for seedlings to take root (Sauer 1976). *Dr. Wester is an associate professor, Department of Geography, University of Hawaii, Honolulu, HI 96822. 125 126 ASSOCIATION OF PACIFIC COAST GEOGRAPHERS About 50 mangrove species, belonging in some 12 families, include remarkable cases of possible convergent evolution. Seedlings of all mangrove species are well adapted for dispersal over oceans but, under natural conditions, none were successful in colonizing the islands of the central Pacific (Hawaii, Society, Marquesas, etc.). The taxa of the so-called eastern mangroves of Indo-Malaysia are, with one exception, made up of different species from the western mangroves of tropical America and West Africa. Only Rhizophora mangle L., the most common tropical American species, is also found in the eastern mangrove region, notably in Fiji, Tonga, and New Caledonia (Salvoza 1936, p. 199; Hou 1960). The Introduction of Mangroves into Hawaii The history of the introduction of exotic organisms is usually incomplete. The record of mangroves in Hawaii has been especially confused. Of the seven introduced taxa, only two are currently maintaining themselves (Table 1). Rhizophora mangle is the most common species in Hawaii, and the majority of mangrove communities are dominated by it. The American Sugar Company (Molokai Ranch Co.) first introduced the species in 1902 and planted it on Molokai in the belief that it would retain sediment from the eroded southern slopes of the island and supplement the honey flora (MacCaughy 1917, Degener 1940). Seedlings were intentionally transplanted from Molokai to Oahu (for reasons unknown) and have since volunteered elsewhere, including places on the islands of Hawaii, Maui, Lanai, and Kauai (Fig. 1). The Hawaiian Sugar Planter's Association made two attempts to introduce Old World species from the Philippines. The first, in 1908, Table 1. Mangrove species in the Hawaiian Islands' Species Date Origin Comment Rhizophora mangle R. mucronata Bruguiera gymnorhiza B.parviflora Ceriops tagal Conocarpus erectus C.erectus var. sericeus 1902 1922 1922 1922 1922 Before 1910 1946 Florida Philippines Philippines Philippines Philippines Florida? Bahamas Abundant Last recorded 1928 Established Last recorded 1948 Last recorded 1922 Cultivated Cultivated 'Dates of introduction and last record were obtained from MacCaughy (op. cit.), accession records of the Hawaiian Sugar Planter's Association, and herbarium records. YEARBOOK · VOLUME 43 · 1981127 THE OCCURRENCE OF MANGROVES IN THE HAWAIIAN ISLANDS OAHU ^He eia Swamp Pearl Harbc Waikele Delta-y>;Ui Ui O O d ? O t? O 55 o. o O > Ui H O W O O£T) X m¡? Ui YEARBOOK »VOLUME 43· 1981131 Raddi, Lantana cámara L., and Leucaena leucocephala (Lam.) de Wit are found, with a few herbs and the vines Paederia foetida L. and Ipomea alba L. Where tall trees are cut back from a bridge to prevent fouling, the lower growing B. gymnorhiza, T. populnea, and H. tiliaceus flourish. This would suggest that the success of R. mangle in areas frequently inundated by tidewater may be explained by competition for light, since the Rhizophora can grow taller and possibly more rapidly than its associates. Attenuated, mature specimens of T. populnea and H. tiliaceus are encountered occasionally under a mangrove canopy and may be remnants of an earlier littoral community that has...