Temporal distribution and composition of phytoplankton in the Southern part of Caspian Sea in Iranian waters from 1994 to 2007
| dc.contributor.author | Khenari, Ali Ganjian | |
| dc.date.accessioned | 2015-07-30T00:51:56Z | |
| dc.date.available | 2015-07-30T00:51:56Z | |
| dc.date.issued | 2011 | |
| dc.description.abstract | Caspian Sea is the largest inner water body on the earth underwent sharp changes in its ecosystem during the recent decades of the twenty century. They were caused by natural eg. transgression of the sea level, climate change, increase of fresh water inflow and anthropogenic factors eg. pollution, invasion of ctenophore Mnemiopsis leidyi and illegal fishing for sturgeons at sea. All that led to significant change in hydrological regime; modify the food base, abundance and biomass of biological resources and bioproductivity of the sea. Long-term qualitative and quantitative characteristics of phytoplankton community structure and biomass were investigated in from 1994 to2007. During the study period, 4556 samples of phytoplankton were collected during 33 cruises in the southern part of the Caspian Sea (SCS). A total of 334 species (88 genera) of phytoplankton were jdentified in the SCS, which comprised of Bacillariophyta, Chlorophyta, Cyanophyta, Pyrrophyta, Euglenophyta, Chrysophyta, Xanthophyta and Cryptophyta. Bacillariophyta and Pyrrophyta were present in all ecological groups. The phytoplankton ecological groups were fresh water species (34%), fresh - brackish - water species (18%), brackish-water species (14%), brackish-marine-water species (4%), marine species (8%) and other species (22%). The dominant groups of phytoplankton from 1994 to 2007 were Bacillariophyta which constituted the major cell abundance and biomass (37 % and 52%, respectively). The highest annual mean phytoplankton cell abundance and biomass were 249.1x106 ± 22.4x106 cells/m3 and 1034.17±117.81 mg/m3 , respectively; and higher population was due to the presence of Pyrrophyta, Bacillariophyta and Cyanophyta between 2001-2002. The cell abundance and biomass of phytoplankton population showed significant difference in years 1994-2007 (p<0.001). The maximum cell abundance (9.7 x106 cells I m3 ) and biomass (83.8 mg/m3 ) were observed in brackish-water and marine water forms, respectively. Longterm changes of cell abundance and biomass in five ecological groups and dominant species were observed in different years. In 2001-2002, the dominant phytoplankton were Exuviella cordata and Rhizosolenia fragilissima; and high density was due to Bacillariophyta and Pyrrophyta in winter. In 1999-2007, after the invasion of ctenophore Mnemiopsis leidyi, higher cell abundance was no longer recorded in spring but in winter and autumn; while higher biomass shifted from summer to winter and spring. High diversity index of phytoplankton was associated with high level of transparency and salinity. Phytoplankton population aggregated at the depth of 0 - 20 m with more than 87% of total cell abundance due to some favorable conditions such as higher water temperature, light penetration, dissolved oxygen and nutrient concentrations. Vertical distribution of phytopl~nkton cell abundance and bio~ass decreased with increasing depth. Water quality in SCS was classified as moderately and highly organically polluted. In the present study, algal genus and species pollution indices (API) were due to the oscillation in the number of phytoplankton species composition. The eutrophication index (EI) showed an increasing trend from oligotrophic to eutrophic, with its lower value was observed for the typical oligotrophic (0.21) in 1994 and the highest in 2005-06 (1.22). Long term EI ranged from 0.26 to 1.22 in 1994/1996 and 1996/1997 were grouped in the typical oligotrophic (0) and 1999/2000 were grouped as the standard mesotrophic (M) and 2003/2004, 2004/2005, 2005/2006 and 2006/2007 were grouped with the typical eutrophic (E). Cyanophyta were represented mainly by Aphanothece elabens, Microcystis spp., Oscillatoria limosa, Spint!ina laxissma and Anabaena spp. throughout the years. The highest cell abundance and biomass were observed in summer and autumn. Long term biomonitoring in the SCS is required to manage its sustainable resources and to prevent environmental degradation. | en_US |
| dc.identifier.uri | http://hdl.handle.net/123456789/889 | |
| dc.language.iso | en | en_US |
| dc.subject | Phytoplankton | en_US |
| dc.subject | Caspian sea | en_US |
| dc.title | Temporal distribution and composition of phytoplankton in the Southern part of Caspian Sea in Iranian waters from 1994 to 2007 | en_US |
| dc.type | Thesis | en_US |
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