|dc.description.abstract||Assessing the ecological characteristics (water quality and the biological functions) of the Mesopotamian marshes is necessary to evaluate their recovery. Mesopotamian marshes have been affected by several anthropogenic impacts and providing a sufficient water supply is a challenge. Among the several anthropogenic activities that have caused damage to the Mesopotamian ecosystem, water shortage (mainly since 1974) and desiccation (from 1993 to 2003) have caused the most damage. In a case like Mesopotamia, it is important to quantify the damage in order to design a recovery plan and suitable recovery methods.
The main goal of my thesis is to define the current hydrological and ecological status of the Mesopotamian marshes after re-flooding, in order to understand and identify the factors that are limiting their recovery to historical conditions. The main objectives of my research are: 1) investigate the changes in discharge and salinity of the main water sources to the Mesopotamian marshes (the Tigris and Euphrates Rivers) over time and how any changes may be affecting water quality; 2) identify the main sources of increased salinity of the marshes after re-flooding; 3) identify the major parameters affecting the water quality Mesopotamia marshes after re-flooding; and 4) investigate whether there are differences in species composition and abundance in phytoplankton communities among the selected re-flooded marshes of Al-Hawizeh, a marsh located in the north-east of the Mesopotamian marsh system, and what environmental parameters relate to those differences.
My results indicate that ~ 45% of the annual water discharge of the Tigris and Euphrates Rivers was lost by 2002 and that there was a significant shift in the period of maximum water discharge from spring (March) during 1973 to summer (June and July) during 2002 – 2005 and to fall (November) during 2006 – 2007. They also indicate that the average water salinity of the two rivers in 2006 – 2007 was 0.73 practical salinity unit (psu) which is 1.9 times greater than their historical level (0.4psu).
The Mesopotamian marshes increased in salinity from their historical level, 0.4 psu, to 2.5 psu during 1980s and then declined to 1.1 psu after re-flooding. The high salinity values observed, especially early in the inundation, were from re-dissolution of salts that accumulated during the desiccation period, while the persistent increase relative to historical values is mainly due to increase the salinity of the inflowing rivers and longer water residence in the marshes. However, re-dissolution of salts can be added to the main reasons of increasing salinity of the Al-Hammar marsh. The results show that there was a net loss of salt from Al-Hawizeh marsh, and a net gain in salt for Hammar Marsh. In both cases, the change was in large part due to changes in water level. The salt budget for Central Marsh was problematical, probably because the water flows in and out of some distributaries were hard to quantify.
Based on water quality indices combining several parameters (dissolved oxygen, nitrate, and pH), changes in water quality from prior to the desiccation period (historical state) to after re-flooding were generally moderate. However, deterioration in water quality of the re-flooded marshes is evident when salinity related parameters, specifically total dissolved solids, chloride and sulphate, are included in the water quality index calculation. Marshes that were severely damaged by desiccation and construction of embankments during the war, Majnoon and Lissan Ijerda, show low potential of recovery compared to marshes that are close to the river inputs.
The Al-Hawizeh marsh complex was investigated as a case study for biological assessment. I identified significant spatial differences among individual marshes within Al-Hawizeh suggesting that their once homogenous nature has been altered since inundation in 2003. Silicate concentrations in Al-Hawizeh marsh were 10 times lower than before desiccation. Since silicate is an important nutrient for diatoms, this may be a driver of phytoplankton community structure in the marshes. A change from abundant Bacillariophyta during the pre-desiccation period to Chlorophyta after re-flooding could be due to reduction in SiO2 concentrations, especially in areas far from the major water inputs. The biological assessment of Al-Hawizeh marsh revealed three important issues: 1) invasion of euryhaline species of phytoplankton, which could reflect increasing salinity over time; 2) harmful species were recorded in small abundance (<1000 cell/ml), which could be a source of serious health issues; and 3) an increase of approximately 100 times in Cyanobacteria over the historical record, which can be attributed to high nutrient levels, especially in the southern marshes of Al-Hawizeh||en