Nurhayat Dalkiran

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.

A new species of Prosopistoma Latreille, 1833 (Ephemeroptera: Prosopistomatidae) from northwestern Turkey

The new mayfly species Prosopistoma orhanelicum sp. n. (Ephemeroptera: Prosopistomatidae) was collected from Orhaneli stream, northwestern Anatolia, Turkey. The main diagnostic larval characters are described and compared with two species which are found in nearby geographic regions. The larvae of P. orhanelicum sp. n. are differentiated by the number of antennal segments, antennal segment 2/3-5 ratio, maxillary palp seg 1/seg 2 ratio, width/length ratio of the head and posterolateral projections on abdominal segments 7–9.

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.

Epilithic diatom assemblages and their relationships with environmental variables in the Nilüfer Stream Basin, Bursa, Turkey

Patterns of epilithic diatom species distribution in relation to environmental variables from 12 sampling sites on the main stream and some of its tributaries in the Nilüfer Stream Basin were determined using multivariate statistical techniques. The stream basin has been heavily influenced by anthropogenic effects. The upper part of the basin that is distant from pollution sources mostly has a spring water quality, while the lower part where the stream flows through the urban area and receives domestic and industrial wastewater has a quite low quality. Ordination techniques using both diatom taxa and 21 environmental variables revealed non- to slightly polluted upper basin sites and highly polluted lower basin sites along the stream. The results showed that the stream catchment is polluted gradually from upstream to downstream and that most of the downstream sites have very low water quality especially in summer months. A total of 134 epilithic diatom taxa belonging to 50 genera were recorded for 12 sample sites. Partial CCA results indicated that water temperature (T), discharge (Q), and total phosphorus (TP) were the most important variables affecting the distribution of diatom species. Unpolluted or slightly polluted upper basin sites were dominated by Achnanthidium minutissimum, Cocconeis placentula var. euglypta, Gomphonema olivaceum, and Navicula tripunctata. Highly polluted lower basin sites were characterized by high levels of organic and inorganic matters and low dissolved oxygen (DO) values. Species widespread in the highly polluted lower basin sites such as Nitzschia umbonata, Nitzschia amphibia, Nitzschia capitellata, Nitzschia palea, Nitzschia paleacea, Luticola mutica, and Stephanodiscus niagarae were mostly related to pollution indicator variables such as ammonium nitrogen (NH4+–N), sodium (Na+), total phosphorus (TP), and total organic matter (TOM).