Small scale turbulence and mixing in semi-enclosed seas (Persian Gulf)

Turbulence and internal waves are probably important in generating layered structures in frontal region of marine environments (e.g. near river plumes outflow into the sea). Here we investigate the role of normal modes of internal waves in generation of layered structure in a part of Persian Gulf where river plume inters and in some laboratory experiments. The model prediction and observations show that layers so formed have a thickness of about 2m based on salinity variations with depth, but layers (about 5m) based on horizontal velocity profiles. Laboratory experiments with a plume outflow in a Filling Box profile also generate normal mode layered structure with 21H=0.5 (where A is layer thickness and H is the plume depth). In these experiments as Re of the flow is smaller than the Re of field flow. The normal modes are substantially dissipated with depth. Typical values of dissipation factor is about 0(100). This factor for field observation is 0(10) which is still substantial. Qualitative comparison between layered structure in field and laboratory is good. It should be emphasized that field observation is for semi-enclosed seas but the laboratory experiments are for enclosed region. Hence some of the discrepancies in the results of two cases are inevitable. Layered structures in marine environments are also produced by double diffusive convection. In this region this should be studied separately.

Investigations on growth ecology and reproduction of Sargassum sp. and Gracilaria on intertidal region in Bandar Lenge

Investigations on growth and quantity of phycocolloids of Sargassum sp. and Gracilaria corticata was done on field and laboratorial works over one year from January 2003 to May 2004. Sargassum thalli began growth from January. The highest biomass value recorded 1611.04 gm^-2 was obtained in November. The receptacles appeared on November and released eggs. The senescence of Sargassum thalli was in December and the new thallus began to grow from January, The highest relative growth rate (6.74 percent) was in February. The relative growth rate showed significant correlation (p<0,05) with temperature. The highest value of alginate was in November (10.02 percent). Alginat content showed significant correlations (p<0.05) with Sargassum biomass. There was no significant effect of environmental factors on alginate content. The highest biomass of Graciiaria was in Match (49.88 gm^-2). Maximum relative growth rate of Gracilara (2 percent) was in December. Relative growth rate of Gracilaria (2.8 percent) was in December. Relative growth rate of Gracilaria showed significant correlations (p<0.05) with temperature. There was significant effect of ammonium (p<0.05) on growth factors of Gracilaria, maximum agar content was in August {10.005 percent). The yield of agar showed significant correlation (p<0.05) with Gracilaria biomass and ammonium in field and laboratory.

The study of histopathological damage in heart and bulbus arteriosus in rainbow trout

This study investigated the pathological changes of heart and bulbus artrius of rainbow trout breeders in several group of ages and density. The aim of study was to consider the process and the intensity of the heart and bulbus arteriosus damages in accordance to gender, age and stocking density of trout in three fish culture center (Zarghezel, Niyak in Haraz Region,Mazandaran and Espiran in Tabriz city environs). In field research, the all records the feed and feeding type, rate of mortality, stocking density of spawners and per spawners fishes, water chemical and physical specification was screened. Stocking density was considered as the most important stressor. 10 fish specimens from 7 weight groups (less than 90g, 90 to 300g, 300 to 500 g, 500 to 1000g, 1 to 3 kg, 3 to 5 kg, over 5 kg), totally 210 specimens were sampled and heart and bulbus arteriosus were taken. Samples were fixed in 10 % formalin and transferred to pathology laboratory of veterinary faculty of Tabriz Azad University. Histopathological slides and H&E staining were prepared from these samples. In total, 47 male and 73 female samples showed cardiovascular injury (29 cases in extensive system, 41 cases in semi intensive system, 50 cases in intensive system). The most important was damages, edema and hyperemia in spongy layer of atrium and ventricle muscles, but degeneration the muscle fibers, moderate edema , minor vascular damage. Hemorrhage as the effect of severs vascular damage, thrombus, sever inflammation, sever degeneration in muscle fiber, necrosis and fibrose were further pathological changed. The results of this study showed that the severity of damage increased by increasing the age (weight) of fishes. This situation was seen in all three culturing system (extensive system, semi intensive system, recirculation system). Histopathological changes is obviously seen in samples over 500g, therefore the damages were found to be important (P<0.05). Pathological effects and its severity in recirculation system was significantly high (P<0.05). Comparison with two other culturing system, histopathological changed in heart and bulbus arterius between male and female was significantly different.