Hydrocarbon Concentrations in Oysters ( Crassostrea virginica ) and Recent Sediments from Three Coastal Lagoons in Tabasco, Mexico

Se realizó una caracterización poblacional del ostión americano Crassostrea virginica existente en tres lagunas costeras de Tabasco. Para esto se determinó la biometría, la estructura poblacional, los parámetros de crecimiento poblacional y el rendimiento durante un ciclo anual. Mensualmente se recolectaron al azar 200 organismos determinándose: frecuencia de tallas, pesos, tasas de crecimiento, expresadas L∞ y K y el rendimiento en carne. Las longitudes totales oscilaron entre 7 y 66 mm, entre 7 y 80 mm y entre 27 y 90 mm, para El Carmen, Machona y Mecoacán, respectivamente, en la mayoría de los meses los organismos fueron mayores a 65 mm, sin embargo, en la laguna El Carmen no alcanzaban la talla de captura permisible para la especie que es de 70 mm. Con relación al peso húmedo total, los organismos de mayor peso, se presentaron en la laguna Mecoacán. El rendimiento en carne mensual presentó su valor mínimo en Enero (51.98 ± 5.23 %) en la laguna de El Carmen y un valor máximo en Mayo (106.29 ± 19.32 %) para la laguna Mecoacán, detectándose diferencias significativas mensuales (Fs = 79.31; P 0.001).

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Spherulitic crystal growth in the prodissoconch larval of Crassostrea virginica

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100076263 ◽

1983 ◽

Vol 41 ◽

pp. 518-519

Author(s):

George G. Cocks ◽

Louis Leibovitz ◽

DoSuk D. Lee

Keyword(s):

Crystal Structure ◽

Crassostrea Virginica ◽

Crystal Orientation ◽

Developmental Changes ◽

Gastrula Stage ◽

Orthorhombic Crystal ◽

Orthorhombic Crystal Structure ◽

Stages Of Growth ◽

Early Stages ◽

Initial Deposition

Our understanding of the structure and the formation of inorganic minerals in the bivalve shells has been considerably advanced by the use of electron microscope. However, very little is known about the ultrastructure of valves in the larval stage of the oysters. The present study examines the developmental changes which occur between the time of conception to the early stages of Dissoconch in the Crassostrea virginica(Gmelin), focusing on the initial deposition of inorganic crystals by the oysters.The spawning was induced by elevating the temperature of the seawater where the adult oysters were conditioned. The eggs and sperm were collected separately, then immediately mixed for the fertilizations to occur. Fertilized animals were kept in the incubator where various stages of development were stopped and observed. The detailed analysis of the early stages of growth showed that CaCO3 crystals(aragonite), with orthorhombic crystal structure, are deposited as early as gastrula stage(Figuresla-b). The next stage in development, the prodissoconch, revealed that the crystal orientation is in the form of spherulites.

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SEM study of quartz grains from recent sediments: Western Iraq

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010017743x ◽

1990 ◽

Vol 48 (4) ◽

pp. 860-861

Author(s):

F. Al-Kufaishi

Keyword(s):

Factor Loading ◽

Fault System ◽

Clay Material ◽

Crustal Material ◽

Factor Analyses ◽

Five Factors ◽

Sem Study ◽

Recent Sediments ◽

Quartz Grains ◽

Positive Factor

Two localities (Al-Marij and Laik) were selected to investigate the type of Quartz Grains from crustal material formed by evaporation of waters discharged by springs in Hit area, western Iraq, Previous studies on the crustal material (1,2) showed that the water discharged by these springs are associated with Abu-Jir fault system which run parallel to the Euphrates river,Factor analyses of the crustal and soil materials (50 samples analysed for 16 variables)(2) showed five factors; the first factor includes SiO2, Al2O3 and TiO2 with positive factor loading, and CaO, L.O.I. with negative loading and hence lead to the conclusion that the distribution of these variables is a reflection of transported clay material.This study concentrates on the use of SEM to investigate the contribution of Quartz grains found in the crustal material on two selected sites.

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Effects of resuspension of eastern oyster Crassostrea virginica biodeposits on phytoplankton community structure

Marine Ecology Progress Series ◽

10.3354/meps13277 ◽

2020 ◽

Vol 640 ◽

pp. 79-105

Author(s):

ET Porter ◽

E Robins ◽

S Davis ◽

R Lacouture ◽

JC Cornwell

Keyword(s):

Water Quality ◽

Community Structure ◽

Crassostrea Virginica ◽

Skeletonema Costatum ◽

Eastern Oyster ◽

Energy Dissipation Rate ◽

Negative Effects ◽

Cell Densities ◽

Sediment Bottom ◽

Nitrite Nitrate

Anthropogenic disturbances in the Chesapeake Bay (USA) have depleted eastern oyster Crassostrea virginica abundance and altered the estuary’s environment and water quality. Efforts to rehabilitate oyster populations are underway; however, the effect of oyster biodeposits on water quality and plankton community structure are not clear. In July 2017, we used 6 shear turbulence resuspension mesocosms (STURMs) to determine differences in plankton composition with and without the daily addition of oyster biodeposits to a muddy sediment bottom. STURM systems had a volume-weighted root mean square turbulent velocity of 1.08 cm s-1, energy dissipation rate of ~0.08 cm2 s-3, and bottom shear stress of ~0.36-0.51 Pa during mixing-on periods during 4 wk of tidal resuspension. Phytoplankton increased their chlorophyll a content in their cells in response to low light in tanks with biodeposits. The diatom Skeletonema costatum bloomed and had significantly longer chains in tanks without biodeposits. These tanks also had significantly lower concentrations of total suspended solids, zooplankton carbon, and nitrite +nitrate, and higher phytoplankton carbon concentrations. Results suggest that the absence of biodeposit resuspension initiates nitrogen uptake for diatom reproduction, increasing the cell densities of S. costatum. The low abundance of the zooplankton population in non-biodeposit tanks suggests an inability of zooplankton to graze on S. costatum and negative effects of S. costatum on zooplankton. A high abundance of the copepod Acartia tonsa in biodeposit tanks may have reduced S. costatum chain length. Oyster biodeposit addition and resuspension efficiently transferred phytoplankton carbon to zooplankton carbon, thus supporting the food web in the estuary.

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