Cultivation of the diatom algae Chaetoceros calcitrans f. pumilus (Paulsen) Takano, 1968 as food for giant oyster larvae Crassostrea gigas (Thunberg)

An impact of modified nutrient media F/2 and Conway on the growth and biomass accumulation of the diatom algae Chaetoceros calcitrans f. pumilus, which is a part of the food for cultivated larvae of the giant oyster Crassostrea gigas in the IMBR RAS nursery, was studied. Maximum values of cell and biomass concentrations were obtained on the modified F/2 nutrient medium (11.22 × 106 cells·ml-1 and 4.93 g·l-1, respectively), and they were much larger than those obtained on Conway medium. Growth parameters of C. calcitrans f. pumilus depended on the ratio of inorganic nitrogen and phosphorus, as well as on the silicon content in nutrient media. The ratio N : P = 12.5 and the silicon concentration of 24 mg·l-1 in the modified F/2 nutrient medium are shown to be approaching the optimal ones for increasing growth rate of diatom algae. It is found that the microalga in concentration 150 × 103 cells·ml-1, cultivated on different nutrient media and included in food composition, has impact on the growth rate of giant oyster larvae. An average daily amount of growth of larvae, whose diet included algae cultivated on modified F/2 nutrient medium, was higher than that of larvae cultivated on Conway medium.

Special Features of Heavy Metals Accumulation in Soft Tissues of Mediterranean Mussel and Giant Oyster Cultivated in the South-East Crimea Coastal Zone

Researchers in the South-East Crimea coastal zone during the past decade indicate that the heavy metals’ ion concentration in the Black Sea waters is growing on as a result of industrial and agricultural operations. Increase of pollution in the off-shore zone bottom sediments is registered as well. In this situation monitoring of the coastal water area with mollusks permanently inhabiting this zone enables to determine the water pollution level. Accumulation of four heavy metals, such as Cd2+, Pb2+, Cu2+, Zn2+ in soft tissues of 18 months old mussels (Mytilus galloprovincialis Lamark,1819) and giant oysters (Crassostrea gigas Thunberg, 1793) introduced in the Karadag Reserve coastal zone. It has been shown that the giant oyster soft tissues accumulate high concentrations of copper and zinc. Only big quantity of zinc was found in the Mediterranean mussel tissues. These metals accumulation in oysters and mussels is stipulated by physiological needs of these bivalves. Low accumulation of the most hazardous pollutants as lead and cadmium states the possibility of mariculture development in studied area.

Age structure, carbonate production and shell loss rate in an Early Miocene reef of the giant oyster <i>Crassostrea gryphoides</i>

We present the first analysis of population structure and cohort distribution in a fossil oyster shell bed based on 1121 shells of the giant oyster Crassostrea gryphoides (von Schlotheim, 1813). Data derive from terrestrial laser scanning of a Lower Miocene shell bed covering 459 m2. Within two transects, individual shells were manually outlined on a digital surface model and cross-checked based on high-resolution orthophotos, resulting in accurate information on center line length and area of exposed shell surface. A growth model was calculated, revealing this species as the fastest growing and largest Crassostrea known so far. Non-normal distribution of size, area and age data hints at the presence of at least four distinct recruitment cohorts. The rapid decline of frequency amplitudes with age is interpreted to be a function of mortality and shell loss. The calculated shell half-lives range around a few years, indicating that oyster reefs were geologically short-lived structures, which could have been fully degraded on a decadal scale. Crassostrea gryphoides reefs were widespread and common along the Miocene circum-Tethyan coasts. Given its enormous growth performance of ∼ 150 g carbonate per year this species has been an important carbonate producer in estuarine settings. Yet, the rapid shell loss impeded the formation of stable structures comparable to coral reefs.

Age structure, carbonate production and shell loss rate in an Early Miocene reef of the giant oyster <i>Crassostrea gryphoides</i>

We present the first analysis of population structure and cohort distribution in a fossil oyster reef based on more than 1121 shells of the giant oyster Crassostrea gryphoides (Schlotheim, 1813). Data derive from Terrestrial Laser Scanning of a Lower Miocene shell bed covering 459 m2. Within two transects, individual shells were manually outlined on a digital surface model and cross-checked based on high-resolution orthophotos, resulting in accurate information on center line length and area of exposed shell surface. A growth model was calculated, revealing this species as the fastest growing and largest Crassostrea known so far. Non-normal distribution of size, area and age data hints at the presence of at least four distinct recruitment cohorts. The rapid decline of frequency amplitudes with age is interpreted to be a function of mortality and shell loss. The calculated shell half-lives range around few years, indicating that oyster reefs were geologically short-lived structures, which could have been fully degraded on a decadal scale. Crassostrea gryphoides reefs were widespread and common along the Miocene circum-Tethyan coasts. Given its enormous growth performance of ~ 150 g carbonate per year this species has been an important carbonate producer in estuarine settings. Yet, the rapid shell loss impeded the formation of stable structures comparable to coral reefs.