International Journal of Marine Science 2014, Vol.4, No.6: 67-73 http://ijms.sophiapublisher.com
Research Report
Open Access
Impact of Sea Level Change of Caspian Sea on Gastropods Temporal and Spatial Variation Homayoun Khoshravan1 , Arya Khoshravan2 1. Coastal Management Group, Caspian Sea National Research & Study Center, Water Research Institute, Sari, Mazandaran, Iran 2. M.S.c student of Islamic Azad University of Tehran (north branch), Iran Corresponding author email:
[email protected] International Journal of Marine Science, 2014, Vol.4, No.6 doi: 10.5376/ijms.2014.04.0006 Received: 15 Oct., 2013 Accepted: 16 Dec., 2013 Published: 04 Jan., 2014 Copyright © 2014 Khoshravan and Khoshravan, This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Khoshravan and Khoshravan, 2014, Impact of Sea Level Change of Caspian Sea on Gastropods Temporal and Spatial Variation, International Journal of Marine Science, Vol.4, No.6: 67-73 (doi: 10.5376/ijms.2014.04.0006)
Abstract Determination, localized and frequency control and distribution condition of Gastropod species in several sedimentary environment in Miankaleh territory, and their temporal and spatial variation by Caspian rapid sea level change are the main targets in this research. By selecting 8 measuring transects along the study area, 24 sediment samples and 8 water samples have been taken for biofacies and chemical properties analysis. At parallel of above mentioned subject, deformation and displacement degree of shore line of the Caspian Sea during 38 years was evaluated by remote sensing and GIS modeling. The results show that the most important species of Gastropod totally include: 10 species associated to 3 genera of two family of Prosobranshia. Also some species of Gastropod was selected due to sedimentary environment bioindicators. Water chemical quality and quantity indicate that the salinity, EC, pH degree is different in several parts of study area. Sediments grain size gradually has decreased from the West to East region of Miankaleh territory. Instead of in the same direction near to Gorgan Golf shore line the sediment particles size have been increased. Gastropod species accumulation and concentration tendency convert to high population in saline low land and lagoon with shallow depth and gentle slope of bottom. The correlation of information layers of Gastropod species location map with shore line displacement in GIS modeling indicate vital variation more in the central and east part of Miankaleh. Keywords Caspian Sea; Sea level change; Fluctuation; Gastropod; Miankaleh
1 Introduction
spreading statement along the Miankaleh territory as real problem. And we examine the responsibility of Bio indicators to Rapid sea level changing of the Caspian Sea as main target. So the measuring of water quality of sub sedimentary environment and sedimentary composition of gastropod settlements are the most important approach for gaining the final conclusion. Previous studies results indicated that study area has very gentle slope and its flooding vulnerability to sea level changing is high degree (Khoshravan, 2011). Also different sedimentary basins and several ecosystems have been recognized around the Miankaleh spit (Amini, 2012; Khoshravan, 2011). From morphological point of view, the long period fluctuation of the Caspian Sea has great impact on Miankaleh sand spit evolution during the late Holocene epoch (Amini, 2012; Khoshravan, 2011). There are so many species of fauna and flora in Miankaleh lagoon (Khoshravan, 2011). They have concentrated much more in the central and eastern part of the lagoon (Khoshravan, 2011). Bivalves and
Generally, oceans and seas fluctuation have vital agent on deformation and displacement of shore line all over the world (Kakroudi, 2012). In due to climatologic, tectonic, geology and anthropogenic impact cause principal changing in the coastal area (Khoshravan, 2007; Barimani, 2011). The Caspian Sea as largest closed basin in the world had perfect sea level changing cycle between 1930 – 1996 with 3 meters elevation changing of water table (Ghanghermeh and Malek, 2005). During the above mentioned time, several sedimentary basin have been affected and mouth of rivers, lagoons, Golf, Islands, and channel inlet have been changed by Caspian rapid sea level changing. In this period water chemical properties and substrate sedimentation condition of sub sedimentary environment were deformed and it caused the temporal and spatial changing of fauna and flora distribution (Rychagov, 1994; Svitoch et al., 2006). So in this research, our attention has been concentrated to Gastropod species recognition and their frequency and 67
International Journal of Marine Science 2014, Vol.4, No.6: 67-73 http://ijms.sophiapublisher.com during the late Holocene (Amini, 2012; Khoshravan, 2011). The length of Miankaleh territory is about 70 Km and its width varied between 3 to 6 Km. The study area was surrounded by Gorgan Golf in the south and Caspian Sea in the other side. The eastern border of Miankaleh is close to Ashoradeh Island and the other side was limited by Amirabad port. There is the very great and precise lagoon in the central and eastern part of Miankaleh region. This lagoon was selected as protected area by international environment agency. Recent study indicated that the water of Miankaleh lagoon was polluted by heavy metal and other pollutants (Ebadati et al., 2005). Miankaleh has temperate weather and it contains several ecosystems such as: beach, sand dune with different shape (mobile, stable and semi stable), lagoon, wetland, channel inlet, paleobeach and golf.
gastropods are dominant genera in the lagoon (Khoshravan, 2000). Pulmonata and prosobranchia groups of gastropods live in the brackish to less saline water in the study area (Khoshravan, 1999; Umonth 1998). Their susceptibility to sea level changing is very high degree (Khoshravan, 1999; Umonth, 1998). During the transgression and regression phase of the Caspian Sea, sedimentary environment condition due to sediment composition and water quality have been changed and this event has direct effect on gastropod species accumulations and distribution. In this stage more aquatic ecosystem has been changed or destructed and some gastropod species as bio indicators can lead us to determine sub sedimentary environment indexes that in this research we are focusing on these objects.
2 Study Area
3 Methods
Miankaleh sand barrier was located in the end eastern part of southern coasts of the Caspian Sea (Figure 1). Hydrodynamic and climatologic impacts have caused to make the elongate sand spit along the west to east direction between Caspian Sea and Gorgan Golf. Waves, currents, winds and rapid sea level changing have deformed the Miankaleh sand spit morphology
Firstly, study area has been studied due to morphology and geology conditions. So by satellite and aerial images interpretation, 8 measuring transect were selected along the Miankaleh spit. Totally 24 sediment samples and 8 water samples have been taken from different parts of study area that they correspond with
Figure 1 Study area location map and measuring stations
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International Journal of Marine Science 2014, Vol.4, No.6: 67-73 http://ijms.sophiapublisher.com (72%), Caspiella sp (22%) and theodoxus sp (6%). The statistic study on gastropods species accumulation and distribution in different part of study area showed that there are many index bioindicators of gastropods in any sub sedimentary environments such as: Caspian beach zone, Miankaleh lagoon, Khozeini channel, saline wetland and Gorgan Golf (Table 2). For example: Pygohydrobia gemmata and Pygohydrobia eichwaldi as equal percent survive in saline wet land and no other species exist near them. Theodoxus pallasi is good indicator for Gorgan golf basin and khozeini channel (Table 2). Pygohydrobia gemmata with high population (>90 %) exist in lagoon and marginal basin (Table 2). Beach zone of Caspian Sea has been determined by Pygohydrobia oviformis (
