Epiphytic algae adherent to aquatic plants are an essential link in the composition of the food chain of any ecosystem. Epiphytic algae act as primary producers of the food chain in the aquatic ecosystem and as natural food for herbivorous zooplankton and fish. This study aimed to detect the presence of algae colonies through remote sensing and to analyze factors that affect the growth of algae through field survey and visual interpretation of satellite images in Lake Um El-Naaj. Samples were collected from six locations on Lake Um El-Naaj from November 2018 to June 2019. The algae samples were collected from submerged parts of emerging aquatic plants (aquatic macrophytes Phragmites australis) and stored in plastic bags with little ambient water and solutions for preservation in the field and the laboratory. Water samples were collected to study the nutritional factors that influence the growth of algae, including the concentration of Phosphate, Nitrate, and Silica (silicon dioxide). The results showed that the values of total phosphorus increased by 1.0, 0.9, and 0.8 mg/L, in January, in places 2, 5, and 6, respectively. The highest nitrate value was 11.2 mg/L in December at site 5, while the lowest concentration values were in November (2.2 mg/L at site 6 and 3.7 mg/L at site 4). Besides, the lowest silicate concentration was 0.4 mg/L in November at site 2, while the highest was 2.4 mg/L in June 2019 at site 6. Based on the findings, it is possible to conclude that, during the winter, the water level increased due to the rain. For this reason, nutrient concentrations were low during the last period. Also, with the use of maps and remote sensing techniques, it is possible to determine the expected values around the station's location as future predictive readings that compensate for the difficulty of reaching these areas.

The present work included qualitative study of epiphytic algae on dead and living stems, leaves of the aquatic plant Phragmitesaustralis Trin ex Stand, in Tigris River in AL- Jadria Site in Baghdad during Autumn 2014, Winter 2015, Spring 2015, and Summer 2015. The physical and chemical parameters of River’s water were studied (water temperature, pH, electric conductivity, Salinity, TSS, TDS, turbidity, light intensity, dissolve oxygen, BOD5, alkalinity, total hardness, calcium, magnesium and plant nutrient). A total of 142 isolates of epiphytic algae were identified. Diatoms were dominant by 117 isolates followed by Cyanobacteria (13isolates), Chlorophyta (11 isolates) and Rhodophyta (1 isolate), Variations in the isolates number were recorded on different parts of macrophyte host as well as, indifferent seasons. Eight new algal isolates (Achnanthesexigue var. heterovalvata Krasske, Navicula exilissima Grunow, Navicula falaisiensis var lanceola Grunow, Navicula microcephalo Grunow, Pleurosigma obscurum W. Smith, Stauroneis amphioxys var. amphioxys Gregory, Stenopterobia intermedia Lewis and Audouinella hermannii Roth).were identified as new records.