Şükran Dere

Factors affecting the current status of a eutrophic shallow lake (Lake Uluabat, Turkey): Relationships between water physical and chemical variables

Lake Uluabat (Apolyont), a protected wetland area, the shorelines of which host urban and industrial sites, is influenced by a high human impact. The lake has eutrophic hardwater characteristics. Temperature, pH value, total dissolved substance, electrical conductivity, dissolved oxygen, biochemical oxygen demand, total hardness, carbonate and bicarbonate alkalinity, nitrate, soluble reactive phosphate, sulphate, soluble reactive silica, secchi disc depth, water depth, water volume, and chlorophyll a values were measured. Physical and chemical variables were determined from samples taken monthly at 10 stations from July 1998 to June 1999 to assess the present status of the lake. Significant correlations between physical and chemical variables were observed, and these relationships reflected the interactions among internal nutrient loadings. Two-way ANOVA test results also showed spatial and temporal variations. Internal nutrient loadings have been stimulated by a combination of different factors. Principal-component analyses showed that pH and alkalinity were the major factors that influenced the internal nutrient loadings in the lake. Results also indicated that nitrate, sulphate, and soluble reactive silica concentrations significantly induced the soluble reactive phosphorus loading. Direct or indirect interactions among primary nutrients were important in the nutrient loading in Lake Uluabat. Mustafakemalpaşa stream and its two branches Orhaneli and Emet, which drain into the lake, receive sewage water from households and industry. For this reason, soluble reactive phosphate, sulphate, nitrate, nitrite, ammonia, boron, and suspended solids were determined in samples collected bi-monthly from the Ayazköy station located on the Mustafakemalpaşa stream during the same study period to determine the effects of the main streams on the lake. Results indicated that the pollution load of Lake Uluabat is highly affected by Mustafakemalpaşa stream inflow. In addition, the present nutrient status, compared with previous years’ data (1986–1990), collected only during summer months, showed that the physical and chemical characteristics of the lake have changed according to former years. The former and recent years’ data also showed that the fluctuation of the water depth also influenced the chemical composition of the lake water. According to qualitative and quantitative observations, the effects of human impact and current status of the lake were determined. The physical and chemical characteristics of the lake water have changed according to human activities and nutrient loadings. Although external nutrient loadings are important because of the inflow of pollutants, internal nutrient loadings are the major factors that determined the trophic status of the lake. In the light of all findings, the lake balance is going to be disturbed, and some measures must be taken to prevent these circumstances.

Determination of the Phenolic Compounds and Antioxidative Capacity in Red Algae Gracilaria bursa-pastoris

There is an increasing demand for natural antioxidant molecules in order to replace the synthetic additives in the food industry. Gracilaria bursa-pastoris (Gmelin) Silva was analyzed to determine its bioactive components including; the total phenolic content, total antioxidant capacity (lipid and water-soluble), vitamins (A, E and C), total protein and total carbohydrate content. In addition, the bioactive components of Gracilaria bursa-pastoris were compared with some plants and seaweeds having antioxidant capacity. This study showed that Gracilaria bursa-pastoris contained a high total phenolic content, vitamin E, vitamin C and the antioxidant capacity. Gracilaria bursa-pastoris can be utilized as a source of natural antioxidant molecules and could be useful for food industry.

Ultraviolet radiation modulates the physiological responses of the calcified rhodophyte Corallina officinalis to elevated CO2

Abstract Ocean acidification reduces the concentration of carbonate ions and increases those of bicarbonate ions in seawater compared with the present oceanic conditions. This altered composition of inorganic carbon species may, by interacting with ultraviolet radiation (UVR), affect the physiology of macroalgal species. However, very little is known about how calcareous algae respond to UVR and ocean acidification. Therefore, we conducted an experiment to determine the effects of UVR and ocean acidification on the calcified rhodophyte Corallina officinalis using CO2-enriched cultures with and without UVR exposure. Low pH increased the relative electron transport rates (rETR) but decreased the CaCO3 content and had a miniscule effect on growth. However, UVA (4.25 W m-2) and a moderate level of UVB (0.5 W m-2) increased the rETR and growth rates in C. officinalis, and there was a significant interactive effect of pH and UVR on UVR-absorbing compound concentrations. Thus, at low irradiance, pH and UVR interact in a way that affects the multiple physiological responses of C. officinalis differently. In particular, changes in the skeletal content induced by low pH may affect how C. officinalis absorbs and uses light. Therefore, the light quality used in ocean acidification experiments will affect the predictions of how calcified macroalgae will respond to elevated CO2.

The effects of elevated-CO2 on physiological performance of Bryopsis plumosa

An increase in the level of atmospheric carbon dioxide (CO2) and the resultant rise in CO2 in seawater alter the inorganic carbon concentrations of seawater. This change, known as ocean acidification, causes lower pH in seawater and may affect the physiology of seaweed species. Accordingly, the main goal of the current study was to determine the physiological responses of Bryopsis plumosa to elevated-CO2. The results indicated that photosynthesis of B. plumosa was insignificantly affected to elevated-CO2, but photosynthetic pigment contents and phenolics were significantly decreased. The results obtained from the research reveal that B. plumosa may become physiologically advanced when exposed to CO2-induced ocean acidification. In particular, B. plumosa may be more able to compete with calcifying algae when it will become future predicted CO2 scenario.

Factors Affecting the Phytoplankton Diversity and Richness in a Shallow Eutrophic Lake in Turkey

ABSTRACT Three hundred and thirty-one phytoplankton taxa were identified from Lake Uluabat over a 12-month period in 1998–1999. Phytoplankton richness varied between 35 and 79 taxa, and the Shannon-Wiener diversity index range was 1.574–3.151. Lake Uluabat was characterized by a high variety of Bacillariophyta (152 taxa), Chlorophyta (89 taxa), and Cyanobacteria (42 taxa). Total diversity was strongly correlated with dissolved oxygen and pH, but total species richness and total density were mostly influenced by temperature and Secchi depth. The lake supported a dynamic phytoplankton community through most months of the year.

Relationships between Epipelic Diatom Taxa (Bacillariophyceae) and Nutrients in Two Karstic Lakes in Central Anatolia, Turkey

ABSTRACT The relationship between epipelic diatom communities and 16 environmental variables from two gypsum karstic lakes in central Anatolia was explored using canonical correspondence analysis. Temperature, ammonium (NH4 +), sulphate (SO4 2-) and calcium (Ca2+) concentrations were the most important variables related to species distribution. The genera Mastogloia, Gomphonema, Navicula, Cymbella, and Nitzschia were the richest in taxa. Diatom species associated with temperature, NH4 +, SO4 2-, and Ca2+ gradients were Mastogloia braunii, Mastogloia smithii var. lacustris, Campylodiscus clypeus, Navicula salinarum and Amphora coffeaeformis.