Bottom Mud Research Articles

Electricity Generation from Rice Bran by a Microbial Fuel Cell and the Influence of Hydrodynamic Cavitation Pretreatment.

Single-chamber microbial fuel cells (MFCs) were constructed using rice bran (carbon source) and pond bottom mud (microbial source). The total electric charge obtained in the MFC combining rice bran with pond bottom mud was four times higher than that in MFC using only rice bran. Phylogenetic analyses revealed dominant growth of fermentative bacteria such as Bacteroides and Clostridium species, and exoelectrogenic Geobacter species in the anode biofilms, suggesting that mutualism of these bacteria is a key factor for effective electricity generation in the MFC. Furthermore, rice bran, consisting of persistent polysaccharide, was pretreated by the hydrodynamic cavitation system to improve the digestibility and enhance the efficiency in MFC, resulting in 26% increase in the total production of electricity.

Nitrogen Budget in Recirculating Aquaculture and Water Exchange Systems for Culturing Litopenaeus vannamei

In order to investigate the culture characteristics of two indoor intensive Litopenaeus vannamei farming modes, recirculating aquaculture system (RAS) and water exchange system (WES), this study was carried out to analyze the water quality and nitrogen budget including various forms of nitrogen, microorganism and chlorophyll-a. Nitrogen budget was calculated based on feed input, shrimp harvest, water quality and renewal rate, and collection of bottom mud. Input nitrogen retained in shrimp was 23.58% and 19.10% respectively for WES and RAS, and most of nitrogen waste retained in water and bottom mud. In addition, most of nitrogen in the water of WES was TAN (21.32%) and nitrite (15.30%), while in RAS was nitrate (25.97%), which means that more than 76% of ammonia and nitrite were removed. The effect of microalgae in RAS and WES was negligible. However, bacteria played a great role in the culture system considering the highest cultivable cultivable bacterial populations in RAS and WES were 1.03×1010 cfu mL−1 and 2.92×109 cfu mL−1, respectively. Meanwhile the proportion of bacteria in nitrogen budget was 29.61% and 24.61% in RAS and WES, respectively. RAS and WES could realize shrimp high stocking culture with water consuming rate of 1.25 m3 per kg shrimp and 3.89 m3 per kg shrimp, and power consuming rates of 3.60 kw h per kg shrimp and 2.51 kw h per kg shrimp, respectively. This study revealed the aquatic environment and nitrogen budget of intensive shrimp farming in detail, which provided the scientific basis for improving the industrial shrimp farming.

The Permian Minnekahta Limestone: a Saline Lake Gypsum Replaced by Calcite

The late Permian Minnekahta Limestone of the Black Hills of South Dakota is not a typical limestone. Sandwiched stratigraphically between continental redbed siliciclastics, it is distinct in its gray-pink appearance and carbonate mineralogy and is considered a local and regional marker bed. Based on its calcite composition and stromatolites, it has previously been interpreted as a tidal flat deposit, leading to speculation of a regional late Permian marine transgression. Here, we show observations that question the original composition, reexamine and refine the sedimentary and stratigraphic characteristics, and suggest an alternate depositional environment. Petrography and x-ray diffraction indicate that the Minnekahta Limestone is dominated by an interlocking crystal mosaic of calcite and gypsum. We have documented pseudomorphs after bottom-growth gypsum crystals, alternating laminae of mm-scale bottom growth gypsum crystal shapes and mud drapes, as well as mudcracks, raindrop imprints, and stromatolites. No carbonate grains, fossils, or tidal rhythmites were noted. These observations suggest that the carbonate phase is a replacement of gypsum. In addition to the sedimentology and petrography, close stratigraphic association with overlying and underlying continental redbeds indicates that this was likely a shallow saline-lake deposit. Other Permo-Triassic carbonate strata in continental redbed sequences throughout the midcontinent of North America, such as those in the Goose Egg, Chugwater, Nippewalla, and Spearfish strata, may have similar continental origin. This study serves as a lesson that paired petrographic observations and mineral identifications are important data necessary for the best interpretation of depositional environments and diagenetic histories.

Updated database on natural radioactivity in building materials in Europe

The paper presents the latest collection of activity concentration data of natural radionuclides (226Ra, 232Th and 4 K) in building materials. This database contains about 24200 samples of both bulk materials and their constituents (bricks, concrete, cement, aggregates) and superficial materials used in most European Union Member States and some European countries. This collection also includes radiological information about some NORM residues and by-products (by-product gypsum, metallurgical slags, fly and bottom ashes and red mud) which can be of radiological concern if recycled in building materials as secondary raw materials. Moreover, radon emanation and radon exhalation rate data are reported for bricks and concrete.

The role of habitat selection on the diversity of macrobenthic communities in three gulfs of the Cuban Archipelago

Diversity and faunal composition of macrobenthic communities remain poorly known in the Caribbean Sea. Here, we explore the diversity and abundance of marine macrobenthos across three gulfs of the Cuban Archipelago and examine the role of habitat type in determining faunal composition and function. Samples collected from 32 soft-bottom sites across four habitat types (mangroves, seagrass beds, unvegetated mud bottoms, and coral reefs) yielded 4231 individuals representing 22 higher macrobenthic taxa. The most abundant taxa were polychaetes, nematodes, crustaceans, and mollusks. Mollusk fauna was particularly diverse (105 species and 74 genera) despite being dominated by two taxa: a bivalve (Parvilucina sp.) and gastropods (Caecum spp). Habitat type was weakly interrelated with the faunal composition of the entire macrobenthos and its molluscan component (<20% of explained variance, in both cases). This weak correlation might reflect the influence of within-habitat heterogeneity, ecological drift, or dispersal barriers. Functional traits differed among habitats, with infaunal mollusks typically found in mud bottom and carnivores more abundant in mangroves. The regional mollusk species richness (105 species) exceeded the richness observed within individual gulfs (39, 40, and 59 species), highlighting high regional diversity. Anthropogenic factors could also be at play. The results suggest, tentatively, that fisheries might have affected the functional and taxonomic structuring of the sampled macrobenthic communities. This initial survey suggests that habitat selection does not exert a strong effect on the macrobenthos (or its molluscan component), and other assembly processes such as drift, dispersal, and human impacts may be important.

Buenas Prácticas Socioambientales en el Manejo Ecológico del Embalse de la Central Hidroeléctrica Manduriacu

Este trabajo identificó especificaciones y condiciones ambientales favorables para el lavado de los lodos de fondo del embalse de la central hidroeléctrica Manduriacu. La mitigación del impacto negativo del lavado busca apuntar a la responsabilidad con el ambiente, la sociedad, cumplimiento con la normativa ambiental y obligaciones adquiridas en el Estudio de Impacto Ambiental, Plan de Manejo Ambiental y Licencia Ambiental No. 012/12 emitida 2012-05-15. En el proyecto se efectuó una prueba piloto del rescate de peces del embalse; y se elaboró el plan de acción propiamente dicho para este evento. El plan consistió en: análisis de los resultados de la prueba piloto; revisión del equipamiento del sitio de rescate de peces; planificación y comunicación interna y externa; metodología de pesca, traslado, mantenimiento y reintroducción de peces al río.

Cornulitids from the Upper Ordovician of northwestern Russia

Four cornulitid species occur in the Rakvere Regional Stage in NW Russia. The new species Conchicolites rossicus is here described; it is the earliest known Conchicolites from the Ordovician of Baltica. The new species has very small tubes with sharp, strong and regular annulations. The diversity of cornulitids in the Rakvere Regional Stage at the Pechurki quarry is usual for the Upper Ordovician of Baltica. The cornulitids of Pechurki quarry encrusted hard organic substrates in a mud bottom (clay and carbonate clay) environment. Cornulites sterlingensis occurs both in the Upper Ordovician of North America and Baltica, which suggest a short distance between these two paleocontinents and/or similar environmental conditions.

Analysis on Heavy Metal Distribution in Overlying Deposit and Pollution Characteristics in Drainage Basin of Xiaojiang River in Dongchuan District, China

The distribution characteristics of heavy metal (Cu, Zn, As, Pb and Cd) content in overlying deposit in Xiaojiang River is analyzed in this thesis, and potential ecological risk index is adopted to evaluate the potential ecological risk of heavy metal pollution in the overlying deposit. Results indicate that the heavy metal (Cu, Zn, As, Pb and Cd) content in overlying deposit in Xiaojiang River all has exceeded standard, especially the content near diggings which is much higher than the national first standard value. And this will affect the bottom mud and river system of Jinsha River to some extent. Cu and Cd are the key pollutants and should be taken as the key object of study. It can be seen from comparison between samples in wet season and that in dry season that pollutants in bottom mud will be released due to the effect of pH value, and secondary pollution of the river will be caused.

Cuttings transport in maxi HDD boreholes with front reaming and one way drilling mud return technologies

Cuttings transport becomes critical important when horizontal directional drilling (HDD) technology has been used more often in long distance and large diameter oil and gas pipeline construction in rocks. Front reaming (FR) and one way drilling mud return (OWDMR) were not new in oil and gas well drilling, but they were rarely used in HDD industry compared to the traditional back reaming (BR) and two way drilling mud return (TWDMR). FR and OWDMR technologies, when they were used in HDD, were designed mainly for highly non-leveled HDD projects to overcome some difficulties such as the recycling of drilling mud. Along with these technologies is that the cuttings need to travel longer distance to the ground surface. In addition, the effect of the drill rod rotation on the cuttings transport does not exist because hole bottom mud motor is usually used in FR. To find a solution for this problem, the cuttings transport mechanism was analyzed based on the drilling mud hydraulics, and then, an equation of cuttings transport distance was derived. It found that the average drilling mud velocity in the annulus and the consistency index of drilling mud are the two most important factors related to the cuttings transport distance. To help with the cuttings transport, a new MMH drilling mud system, which provides a high consistency index and a low flow index, was used in rock HDD projects, instead of the common Bentonite-water drilling mud system.

New didemnid ascidian spicule records calibrated to the nannofossil data chronostratigraphically in the Quaternary marine deposits of Lake İznik (NW Turkey) and their paleoenvironmental interpretations

This study discusses the detailed chronobiostratigraphic history and paleoenvironmental features in the Quaternary period at Lake İznik (NW Turkey) based on fossil ascidian spicules and nannofossil records. New ascidian spicule data and nannofossils were identified in three lake bottom mud cores, K-1, K-2, and K-3, and in the muddy sediments of two drilled samples, SK-1 and SK-2. In the samples, eleven fossil ascidian spicule species, including two new species, were recorded: Bonetia acuta Varol & Houghton, Bonetia brevis Varol & Houghton, Bonetia quasitruncata Varol & Houghton, Micrascidites vulgaris Deflandre & Deflandre-Rigaud, M. gothicus sp. nov., Monniotia aciformis Varol & Houghton, M. fasciculata Varol & Houghton, M. minutula sp. nov., Rigaudia multiradiata Varol & Houghton, and R. praecisa Varol & Houghton. Ascidian spicules in the core muds probably released from the Didemnum species (i.e., D. candidum) were compared to Holocene nannofossil data, such as Alisphaera sp., Coronosphaera mediterranea, Emiliania huxleyi, small Gephyrocapsa spp., and Scyphosphaera spp., representing the NN21 Emiliania huxleyi zone. Drilling core sediments also include the same ascidian fossils, and also one nannofossil species, Gephyrocapsa oceanica, indicating the NN21 zone of upper Pleistocene stage, as found in sample SK-1.Based on the ascidian spicules and nannofossil records of the coring/drilled muds of Lake İznik was marine, as an inlet or lagoon connected to the modern Gulf of Gemlik, during the Pleistocene to Upper Holocene. It was likely separated from the Marmara Sea and turned into a freshwater lake after the upper Holocene.

Experimental study on the influence of dissolved organic matter in water and redox state of bottom sediment on water quality dynamics under anaerobic conditions in an organically polluted water body

To understand aquatic environmental deterioration due to the anoxic state in an organically polluted water body, water quality dynamics under anaerobic conditions were examined through beaker-scale water quality monitoring. This study focused on the dynamic properties of NO3–N, NH4–N, PO4–P, and sulfide from the biochemical reactions point of view, and based on anaerobic respiration activities, such as denitrification, iron reduction, and sulfate reduction. The specific aims of this study were to quantitatively estimate the impacts of the oxidative/reductive state of the sediment surface and the high/low concentrations of dissolved organic matter on the dynamic properties of water quality under anaerobic conditions. The beaker-scale water quality monitoring was carried out through continuous measurements of dissolved oxygen and oxidation–reduction potential (ORP), as well as periodic observations of water quality parameters for six cases that are composed from combinations of three experimental conditions: (1) concentration of dissolved organic carbon (DOC); (2) redox state of the sediment; and (3) concentration of NO3–N. As a result, the temporal changes in ORP under anaerobic conditions exhibited a five-step process of decline without these conditions. Also, high DOC concentrations and oxidative states of the bottom mud accelerated the release of PO4–P and sulfide generation through promoting biological iron reduction and sulfate reduction, because these conditions increase respiratory substrates for anaerobic microorganisms, such as iron and sulfate-reducing bacteria. It was concluded that our results would provide important information about the mechanisms of aqueous environmental deterioration due to organic pollution in closed water bodies.

Transient reflection from mud during molecular diffusion of salt

Harbor basins and estuarine environments experience drastic salinity fluctuations in the water near the water-sediment interface, which can significantly affect how sound interacts with a low-velocity mud bottom. This presents challenges in applications including mine detection, port protection and shallow water sonar. In a previous investigation of this system, a mud sample that was saturated with fresh water was instantaneously exposed to salt water. Laboratory measurements of plane wave reflection from the water-mud interface were obtained using a time-gated broadband impulse as time evolved. Results suggested molecular diffusion of salt into the sample had altered the reflected pulse’s amplitude and caused a depth-dependent impedance profile in the mud. The sediment was discretized into layers much thinner than a wavelength and a multi-layer steady-state model was used to predict the reflection from the diffusing mud. As the effective diffusion length reached a critical value, predictions of the steady-state model began to deviate from the measurements, indicating that a transient solution was required. A model of the transient reflection of a finite-length pulse from a half space with an arbitrary impedance will be presented and model results compared with laboratory measurements. [Work supported by ONR.]

Numerical study on the dissipation of water waves over a viscous fluid-mud layer

Direct simulations of the Navier–Stokes equations are performed to investigate the interaction between a nonlinear wave at the water surface and an interfacial wave at the fluid-mud layer below. A level-set method is employed to capture the air–water and water–mud interfaces. Despite the nonlinearity of the governing equations, the direct numerical simulation shows that the total wave-damping rate exhibits a remarkable consistency with the prediction of the linear theory. To reveal the underlying mechanism, we analyze the velocity and vortcity fields, energy transfer from the water to the mud, and energy dissipation. The detailed analysis of velocity and vorticity fields shows an appreciable nonlinear effect in the water but a relatively weak nonlinear effect in the fluid mud. The major pathway of transferring energy from the water to the mud is the pressure acting on the water–mud interface. The viscous dissipation of the energy also exhibits a local, significant nonlinear effect in the water. However, the excess and deficiency in the dissipation rate at different wave phases compared with the linear theory largely cancel each other, resulting in an overall wave-damping rate close to the prediction of the linear theory. Furthermore, the analysis of energy budgets elucidates a comprehensive picture of energy transport and dissipation in the wave–mud system. In the water, the horizontal motion first loses energy to the vertical motion through the pressure–strain correlation. The energy of the vertical motion is then transported downwards by the pressure and vertical advection. Across the water–mud interface, the vertical motion of the water transmits energy to the mud through the pressure work. In the mud, the energy of the vertical motion is transported downwards by the pressure and then redistributed to the horizontal motion through the pressure–strain correlation again. The energy of the horizontal motion is transported towards the mud bottom through the viscous diffusion and is finally dissipated.

Brittle stars from the British Oxford Clay: unexpected ophiuroid diversity on Jurassic sublittoral mud bottoms

AbstractThree new ophiuran species, Enakomusium whymanae n. sp., Aspidophiura? seren n. sp., and Ophiotitanos smithi n. sp., and an unnamed specimen assignable to the genus Dermocoma are described from the Callovian to Oxfordian Oxford Clay Formation of Great Britain. These determinations are based on new finds and a critical reassessment of historic specimens. The Oxford Clay ophiuroids represent two loose assemblages, one from the middle Callovian Peterborough Member and the other from the lower Oxfordian Weymouth Member. Both assemblages accord well with coeval midshelf mud bottom ophiuroid communities in terms of taxonomic composition and relative abundance of taxa. The British Oxford Clay ophiuroids are particularly significant as they are one of the rare instances where multiple species are represented, almost exclusively, by exceptionally preserved articulated skeletons. This provides an important window into the understanding of mid-Upper Jurassic ophiuroid paleobiology.

Sponges of the Guyana Shelf.

Sponges collected on the Guyana Shelf, predominantly in Suriname offshore waters, by Dutch HMS 'Snellius' O.C.P.S. 1966, HMS 'Luymes' O.C.P.S. II 1969, and HMS 'Luymes' Guyana Shelf 1970 expeditions are described in this study. Sponges were obtained by trawling, dredging or grabbing on sandy, muddy, shelly, and fossil reef bottoms at 88 stations between 19 and 681 m depth. A total of 351 samples were identified to species level, each consisting of one or more specimens of a given species from each individual station (together comprising 547 individuals and fragments). The collection yielded 119 species together belonging to all sponge classes, but in large majority are Demospongiae. All species are identified to species level, occasionally tentatively, and all are described and illustrated. A new subgenus is proposed, Tedania (Stylotedania) subgen. nov. and a previously synonymized genus, Tylosigma Topsent, 1894 is revived. Thirtysix species were found to be new to science, excluding the first Central West Atlantic record of the genus Halicnemia, not named at the species level because of lack of sufficient material. The new species erected are, in alphabetical order: Amphoriscus ancora sp. nov., Biemna rhabdotylostylota sp. nov., Callyspongia (Callyspongia) scutica sp. nov., Chelonaplysilla americana sp. nov., Cladocroce guyanensis sp. nov., Clathria (Axosuberites) riosae sp. nov., Clathria (Clathria) gomezae sp. nov., Clathria (Microciona) snelliusae sp. nov., Clathria (Thalysias) complanata sp. nov., Clathria (Thalysias) zeai sp. nov., Coelosphaera (Coelosphaera) lissodendoryxoides sp. nov., Craniella crustocorticata sp. nov., Diplastrella spirastrelloides sp. nov., Epipolasis tubulata sp. nov., Erylus rhabdocoronatus sp. nov., Erylus surinamensis sp. nov., Geodia pocillum sp. nov., Geodia sulcata sp. nov., Hemiasterella camelus sp. nov., Hymedesmia (Stylopus) alcoladoi sp. nov., Hymenancora cristoboi sp. nov., Penares sineastra sp. nov., Hymerhabdia kobluki sp. nov., Leucosolenia salpinx sp. nov., Petrosia (Strongylophora) devoogdae sp. nov., Placospongia ruetzleri sp. nov., Pyloderma tropicale sp. nov., Raspailia (Parasyringella) thamnopilosa sp. nov., Raspailia (Raspailia) johnhooperi sp. nov., Sphaerotylus bouryesnaultae sp. nov., Spirastrella erylicola sp. nov., Stelletta vervoorti sp. nov., Suberites crispolobatus sp. nov., Tedania (Stylotedania) folium subgen. nov. sp. nov., Timea tylasterina sp. nov., and Tylosigma ostreicola sp. nov. Two new combinations are proposed: Amphimedon nanaspiculata (Hartman, 1955) comb. nov. and Oceanapia ascidia (Schmidt, 1870) comb. nov. In addition, for two preoccupied combinations, new names, Coelosphaera (Coelosphaera) barbadensis nom. nov. and Hymedesmia (Hymedesmia) rowi nom. nov., are erected. The spatial distribution of the collected specimens over the Guyana Shelf was traced and the results were compared with existing information on bottom conditions. There was a convincing correlation between the location of fossil reefs and other hard substrates such as shell ridges with peaks in the occurrence of species diversity and specimen numbers. Stations made on sand and mud bottoms away from these zones of hard substrates were generally poor in species, but some were found to be rich in individuals of specialized soft bottom dwellers such as Tetilla pentatriaena, Tribrachium schmidtii, Fangophilina submersa, and Oceanapia species. The species composition of the Guyana Shelf was compared with that of neighbouring regions of the Caribbean and from North and East Brazil (Díaz in Miloslavich et al. 2010; Muricy et al. 2011). About 35% of the species encountered are widespread in the Central West Atlantic, occurring both to the north and to the south. Indications that the Guyana Shelf sponge fauna is clearly transitional are southernmost occurrences for Caribbean species (about 30%), and northernmost occurrences of Brazilian species (13%), with a high proportion (25%) of new species, which may be expected to have distributions extending to the Caribbean, to Brazil or both regions.

Performance Assessment of ANN in Estimating Remotely Sensed Extracted Bathymetry. Case Study: Eastern Harbor of Alexandria

The water depth extraction of shallow water plays an important role for marine safety. It is considered a useful reconnaissance tool to save time and cost to be used in preliminary survey. This paper aims to assess the performance of Artificial Neural Networks (ANN) in estimating the bathymetry of the Eastern harbor of Alexandria Egypt as a case study. This area of the case study represents a low turbid, mud bottom and shallow water area. The estimation of shallow water depth is based on ANN fitting algorithms using the logarithms of multispectral bands reflectance value. The estimation of water depths using optical bands of Landsat-8 multispectral images is extracted directly without regard to other environmental factors (bottom type and sea sediments). The images are first corrected for the effects caused by atmospheric conditions and sun specular. The bands are then calibrated using reference measurements obtained using GPS and single beam echo sounder in the study area. The estimated depths using ANN based on bands 1 &3, 3 only and 2 &3 show higher correlations and lower root mean square error compared the estimation made by previously developed statistically equations which were updated using the same data sets used in developing the ANNs. The ANN has a better capability to estimate the bathymetry using remotely-sensed data extracted from Landsat-8 images.

Three Species of &lt;i&gt;Grandidierella &lt;/i&gt;(Crustacea: Amphipoda: Aoridae) from Coastal Areas of the Tohoku and Kanto-Tokai Districts, East Japan, with the Description of Two New Species

Three species of Grandidierella (Crustacea: Amphipoda: Aoridae) were collected from coastal areas of the Tohoku and Kanto-Tokai Districts, East Japan. The first species is G. sanrikuensis sp. nov. from Miyagi Prefecture, which is characterized by the male gnathopod 1 with carpus bearing 3 teeth (only middle tooth large). The second species is G. rubroantennata sp. nov. from Chiba Prefecture. This new species is identical with G. insulae sensu Ariyama (1996) , but is different from the true G. insulae Myers, 1981 in the more flagellar articles of the antennae. The last species is G. osakaensis Ariyama, 1996 , from river mouths in Kanagawa and Shizuoka Prefectures and an anchialine pool in Izu Oshima Island, Tokyo Prefecture. This species can inhabit various sandy mud bottoms in a brackish environment. Including G. japonica Stephensen, 1938, four Grandidierella species occur in the districts.

First Report of the Morphology and rDNA Sequences of Two Pseudopolydora Species (Annelida: Spionidae) from Japan.

The morphology of two Pseudopolydora species, P. cf. reticulata Radashevsky and Hsieh, 2000 and P. achaeta Radashevsky and Hsieh, 2000 are reported from Japan for the first time. Pseudopolydora cf. reticulata was collected from Japanese tidal flats, and individuals possess the characteristic netlike pigmentation on the dorsum of anterior chaetigers and the longitudinal black band along midline of caruncle. Pseudopolydora achaeta was collected from subtidal bottom mud of Onagawa Bay, and individuals have distinctive characteristics, such as intensive black pigmentation on dorsal and ventral sides of the anterior body and nearly straight vertical rows of major spines on the fifth chaetiger. The morphology of P. cf. reticulata is very similar to that of P. cf. kempi, with which it had been confused in Japan. We analyzed the 18S and 28S rRNA gene sequences of all five Pseudopolydora species recorded from Japan and found strong evidence that they are genetically distinct. Our analysis also suggests that boring polydorids have evolved among non-boring ones; the genus Pseudopolydora, which mostly shows the non-boring form, appears to have remained in a more ancestral condition.

Seasonal mesoscale shifts of demersal nekton assemblages in the subtropical South-western Atlantic

ABSTRACTThe present study shows a hitherto undocumented pattern of mesoscale seasonal shifts of teleost fish and cephalopod assemblages along the shelf and upper slope of southern Brazil. Through multivariate techniques we discerned four consistent groups: coastal, warm shelf, cold shelf and upper-slope assemblages. The warm shelf and the upper-slope assemblages were present year round, whereas the cold shelf assemblage occurred almost exclusively in the cold season, and the coastal assemblage expanded toward the south in the warm season. The coastal and shelf nekton fauna was dominated by juveniles and adults of the sciaenid fishes Macrodon ancylodon, Cynoscion guatucupa, Micropogonias furnieri, Umbrina canosai and Paralonchurus brasiliensis, the cutlassfish Trichiurus lepturus and the hake Merluccius hubbsi. The upper-slope assemblage was more diversified and included Polyprion americanus, Urophycis mystacea, the squid Illex argentinus and macrourids. Similar to other subtropical Atlantic ecosystems, the dominance of sciaenids is related to the large areas of sand and mud bottoms, and the low salinity due to the high freshwater runoff of the La Plata River and Patos Lagoon. The choice of seasonal or spatial closures or the planning of marine protected areas may benefit from a greater understanding of the seasonal spatial shifts of the fish assemblages.

Technology to suppress malodor at the watersides from bottom mud dredging

底泥が堆積した水域は，流量や貯水量を低下させ，船舶航行の妨げとなるばかりでなく，底泥から栄養塩が溶出してアオコ等藍藻類の増殖により汚濁化し，悪臭が発生するため，底泥を浚渫除去することが求められている．有機性底泥は，悪臭物質を生成して浚渫工事中に悪臭を発生させ，取り出された底泥からも悪臭がするため，環境対策や再利用のための工事費用が莫大となり浚渫工事の妨げとなる．そこで，効率的かつ経済的に，浚渫底泥の個液分離処理を行い，工事中はもちろん分離した水や土からも悪臭を防止するMSC工法を考察する．