Journal of the Persian Gulf (Marine Science)
Volume:5 Issue: 16, Summer 2014

Caspian Sea with an average depth of 27m is the largest enclosed water body in the world. Despite its enormity and valuable biotic and economic resources, investigations on the biota and seawater properties are mosaic at best. In previous studies, the monitoring of the chlorophyll-a concentrations in the Southern Caspian Sea was organized based on satellite data sets; however, vertical distribution of chlorophyll-a concentrations and its variations in deeper layers of the southern Caspian seawater are not well known. The aim of this research was to study the variations of seasonal distributions of chlorophyll-a near Anzali Port in northern Iran. Data collection was performed at 23 stations, 2 km apart, along four survey lines perpendicular to the coastline and two transects parallel to the coast every season using a research vessel. Field measurements in the study area were carried out. A portable CTD probe was applied for profiling from sea surface to bottom. Results of seasonal field measurements showed variations of the seawater properties (e.g. temperature, salinity, density and chlorophyll-a). Maximum depth of the profiling stations was more than 470 m and vertical structure of temperature in the southern Caspian Sea waters with a significant seasonal thermocline between 20-50 m depths in summer with a vertical difference of 16oC were characterized. Seasonal average of the salinity was in the range of 12.27-12.37 PSU for the period of measurements. The highest Chlorophyll-a content in the range of 0.2-3.4 mg m-3, was found below that of the sea surface in summer. Variations of the chlorophyll-a concentration in the study area can be attributed to the effect of changes in seawater characteristics in various seasons, stratification and heating of the sea surface layer in the warm seasons and discharge of lagoon and rivers in the study area. The range of the concentrations at the sea surface in August and November were higher than the measured values in April in the study area.

During ROPME Winter Cruise 2006, twenty six surface sediment samples taken from the Northwestern part of the Persian Gulf at depths of 13-77m were analyzed for their foraminifera content. A total of 93 species of benthic foraminifera were found in the study area. The foraminifera assemblages were dominated by Ammonia beccarii, Spiroloculina excavata, S. depressa, Quinqueloculina dimidiata, Q. seminula, Q. costata, Triloculina sp. and Bolivina spp. The dominant species constituted from 52 to 88%, sub- dominant species from 4 to 34% and rare species from 0.27 to 1.37%. Compound diversity (H) was uniformly low at all stations ranging from 0.90 to 1.66 at stations 8 and 7, respectively. Low species diversity values indicated stress conditions in the study area according to Welch model. There was no correlation (p≤0.05) between total foraminifera assemblages and environmental parameters.

Caspian Sea is the largest land locked water body in the world and has been characterized by significant relative sea-level changes since the Pliocene. The sea-level oscillations have strongly impacted the coastal areas depending on geomorphological setting. This study aims to investigate the impacts of sea level oscillations on low-lying coasts of the southeastern flank of the Caspian Sea using sedimentological, paleontological and geophysical tools. The results show that barrier-lagoon development with overstepping migration of the complex is the response of low lying coasts to the rapid sea level changes. Moreover, development of saline environments is another response to sea level changes for more inland coastal areas. According to the radiocarbon dating results, the area was subjected to Amudarya flooding around 1800 BP and high sedimentation rate in the second half of the Little Ice Age, underpinned by higher precipitation rate and sea-level rise.

The present study aims to recognize dhow prawn trawl by-catch from Hormuzgan coastal waters (Northeast Persian Gulf). Sampling was carried out of 36 hauls by using traditionally wooden dhow among prawn fishing season in 2011. The catch composition consisted of 31.66% target species prawns, mainly banana prawn (Penaeus merguiensis) and 68.34% by-catch. The total by-catch was 4,622.67kg comprised of 56 species and 37 families. Species composition of by-catch was 81.08% Teleostei, 0.1% Elasmobranchs and 18.8% Invertebrates. Ulmaridae, leiognathidae and Mullidae were the most abundant families with mean CPUE of 10.06, 9.97 and 7.73 kg/hour, respectively. CPUE, Occurrence indices and catch percentage of species (based on Wt %) have been calculated. Prawn-toby- catch ratio was computed at 1:2.15. It was estimated that annual volumes of the entire fleet dhow prawn trawls in Hormuzgan coastal waters consisted of 5,728 tons of by-catch.. The investigation of the by-catch showed the large pressure on commercial and non-commercial fish stocks in the fishing grounds of northern Persian Gulf; Therefore, fishery managers need to consider other species when determining catch or effort limits, prawn fishing season and area restrictions.

Growth performance, food efficiency and body composition of pikeperch (Sander lucioperca) were investigated with 1 or 2 g/kg L-carnitine added to the diet. Control diet did not contain L-carnitine. Two hundred pikeperch fingerlings (1.63 g, mean weight) were stocked in each 1 m3 concrete tank and fed equally 6 meals per day for 6 weeks. Higher increment in body weight (5.92 ± 0.37 g), the highest specific growth rate (3.75 ± 0.17) and food efficiency (98.04 ± 4.56), the highest crude protein (64.53 ± 0.84), the lowest crude lipid (21.59 ± 0.23) and significant (P<0.05) lowering in food conversion ratio (1.02 ± 0.05) were obtained with 2 g/kg L-carnitine diet. The greatest survival rate (84.88 ± 0.92) occurred when fingerlings were fed with 1 g/kg L-carnitine. Both treatments with L-carnitine showed lesser rate of cannibalism than in control (1.25± 0.09). Use of dietary L-carnitine improved growth performance and body composition of pikeperch fingerlings.

Because of random nature of many dependent variables in coastal engineering, treatment of effective parameters is generally associated with uncertainty. Numerical models are often used for dynamic analysis of complex structures, including mechanical systems. Furthermore, deterministic models are not sufficient for exact anticipation of structure’s dynamic response, but probabilistic models are far more efficient in modelling uncertainties. To determine the uncertainty effect on dynamic characteristics, the laboratory samples of a pier structure were created. Stochastic finite element method was used for numerical study of pier’s dynamic behavior. For this purpose, the concept of variable distributions of Gaussian and Wishart random matrices for modeling dynamic characteristics of the system was used. At last, by comparing the output frequency response function obtained from empirical experiments and numerical simulation of stochastic finite element method, it is shown that probability density function of Wishart matrix evaluates and tracks uncertainty parameters in system’s dynamic response far better than Gaussian matrix.

The zooplankton biomass and distribution were studied during two oceanographic cruises in NE part of the Persian Gulf in autumn 2012 (November) and summer 2013 (August) with 300 μmmesh net. Zooplankton samples were analyzed for biomass content. Zooplankton biomass expressed as mg m-3 dry wt., was greatest during summer cruise (mean of 18.8 ± 4.6 mg m-3 dry wt.). The mean zooplankton biomass during summer cruise was slightly higher than autumn cruise (mean of 16.2 ± 1.7 mg m-3 dry wt.). Higher zooplankton biomass values (mean of 127.7 mg m-3 dry wt.) occurred in the central part of the Persian Gulf, between NW of Kish and Hendourabi Islands. Zooplankton biomass was not higher in near-coastal waters than in the offshore. Zooplankton biomass was not spatially and temporally significant (p>0.05).