İzmit Körfezi'ne dökülen akarsuların su kalitesinin değerlendirilmesinde diyatome indekslerinin kullanılması = The use of diatome indices in assessment of the water quality of streams falling into Izmit Bay

Abstract

In this study, the physical, chemical and biological water quality of 13 stations in 8 streams flowing into Izmit Bay were determined. Biologically, it was aimed to reveal the ecological quality of these streams by examining epilithic diatoms. The Bay of Izmit, where intensive industrialization and urbanization are seen, is located in the east of the Marmara Sea and is frequently associated with environmental problems. Recently, it has been faced with mucilage problems. This situation raises many questions about the pollution load of the streams flowing into Izmit Bay. There are very few studies on how these streams affect the existing mucilage problems. In our study, it is planned to determine the physical, chemical and biological pollution status of the selected streams and to determine what kind of pollution load both these streams and other streams around the gulf leave to Izmit Bay and Marmara Sea. In our study, a comprehensive study area was created by selecting streams from the east, west and south of the bay. Water and diatom samples were taken from a total of 13 stations located in Ballıkaya (1), Saz (2), Dil (3), Çınarlı (4 and 5), Yırım (6 and 7), Kiraz (8 and 9), Hisar (10 and 11) and Değirmen (12 and 13) streams flowing into Izmit Bay throughout the year of 2022-2023 in the fall, winter, spring and summer seasons. A total of 51 samples were studied since one stream could not be sampled due to the drying of one stream in summer. Temperature, dissolved oxygen, electrical conductivity and pH values of the streams were measured in situ. Water samples taken from these streams were subjected to a series of chemical analyses in the laboratory and then orthophosphate, total phosphorus, nitrite nitrogen, nitrate nitrogen, sulfate and silica values were measured in a spectrophotometer. The water quality of the stations was determined according to the physicochemicals measured, taking into account the Surface Water Quality Regulation of the Ministry of Agriculture and Forestry in 2015. In order to obtain epilithic diatom samples, stone samples were taken from the streams and these stones were brushed to release the diatoms living on the stones. The diatom samples were brought to the laboratory under appropriate conditions. The identification of epilithic diatoms was made with the help of species-specific patterns of siliceous cell walls (frustules). In order to obtain the siliceous frustules, the cell contents were burned with acid and the samples were made into permanent preparations. Diatom samples were identified and counted with OLYMPUS BX51 research microscope. Species were photographed and identification was done with spesific identification key books. The current names of diatom species were checked on the "Algabase" website. At least 400 diatoms (maximum 500) were counted in each preparation. Using these data, the Artois-Picardie Diatom Index, Eutrophication/Pollution Index, Biological Diatom Index, Steinberg and Schiefele's Index, Swiss Diatom Index, Watanabe Index, Specific Pollution Sensitivity Index, Sládeček's Index Descy's Index, Leclercq and Maquet Diatomic Index, Generic Diatom Index, Metric-European Index, Trophic Diatom Index, Trophic-Saprobic Index, Pampean Diatom Index, Rott's Saprobic Metric Index, and Rott's Trophic Metric Index indices were calculated using OMNIDIA program. Trophic Index Turkey was calculated with excel program. From the counts obtained, individuals with ten percent of the total number of individuals were considered dominant. Frequent (40-60%) and most frequent (60-80%) species were determined throughout the study. Pollution indicator values of dominant species were determined according to literature. Redundancy analysis was performed using CANOCO package program to see the relationship between sampling stations, dominant species, physical and chemical parameters. In order to determine the similarity of the stations in terms of diatom species composition, similarity analysis was performed using Bray-Curtis analysis and PAST 4.03 package program. Diversity (Shanon diversity index) and Evenness values of the stations were obtained from OMNIDIA program. The differences of all physicochemical and biological parameters between stations and seasons were statistically determined using non-parametric Kruskal-Wallis or parametric analysis of variance (one-way ANOVA) tests using SPSS 20.0 package program. Based on the regression of physicochemicals with diatom indices, the indices with strong regression with orthophosphate and total phosphorus were determined as the indices that gave the best results in this study. At the same time, the regression of physicochemicals with Species richness, Diversity, and Eveness was examined to see how environmental parameters affect Species richness, Diversity, and Eveness. As a result of all studies, 347 diatom taxa belonging to 32 families were identified from 51 samples. The highest number of species was observed at the 8th station with 161 species and the lowest number of species was observed at the 2nd station with 57 taxa. During the studied period 42 different dominant species were identified such as Amphora indistincta, Achnanthidium minutissimum, Achnanthidium minutissimum var. jackii, Amphora pediculus, Aulacoseira subarctica, Cocconeis lineata, Cocconeis pediculus, Hantzschia amphioxys, Luticola mutica, Navicula germainii, Nitzschia fonticola, Cocconeis sp., Placoneis anglophila, Cymbella lanceolata, Nitzschia amphibia, Sellaphora sp., Mayamaea permitis, Sellaphora saugerresii, Mayamaea atomus, Fistulifera saprophila, Surirella minuta, Navicula veneta, Nitzschia palea, Nitzschia palea var. debilis, Nitzschia capitellata, Gomphonema lagenula, Nitzschia umbonata, Halamphora montana, Nitzschia archibaldii, Diatoma moniliformis, Achnanthidium saprophilum, Amphora eximia, Planothidium frequentissimum, Gomphonella olivacea, Cocconeis placentula, Melosira varians, Ulnaria biceps, Navicula tripunctata, Achnanthidium affine, Reimeria uniseriata, Reimera sinuata. The most common species between 60-80% were Cocconeis lineata, Nitzschia amphibia, Amphora pedicuuls, Achnanthidium minitissimum var. jackii, Gomphonema pumilum, Amphora indistincta, Gomphonema parvulum, Craticula subminuscula, Cocconeis pediculus, Cocconeis euglypta, Planothidium frequentissimum, Sellaphora saugerressii and Navicula tripunctata. The most common species between 40-60% were Amphora inariensis, Cocconeis placentula, Mayamea permitis, Melosira varians, Nitzschia palea, Nitzschia dissipata, Nitzschia linearis, Nitzschia capitellata, Nitzschia palea var. debilis, Navicula antonii, Navicula veneta, Navicula antonii, Surirella angusta, Surirella minuta and Navicula gregaria. According to the index results that gave the strongest regression with orthophosphate and total phosphorus, Saz (2), Dil (3), Yırım (7), Kiraz (9), Hisar (11) and Değirmen (13) stations were found to be "very poor" eutrophic. Hisar (10) and Değirmen (12) stations were found to be meso-eutrophic of "poor" quality, Ballıkaya (1), Çınarlı (4 and 5) and Yırım (6) stations were found to be meso-eutrophic of "moderate" quality and Kiraz (8) station was found to be oligo-mesotrophic of moderate-good quality. In the Redundancy Analysis, Saz (2), Dil (3) and Hisar (11) stations, pollutant physicochemical parameters and dominant species such as Craticula subminuscula, Nitzschia palea, Nitzschia palea var. debilis, Nitzschia amphibia, Nitzschia capitellata, Navicula veneta, Mayamea permitis, Fistulifera saprophila, Sellaphora saugerressii, Achnanthidium minutissimum var. jackii are located close to each other. These species were found to be pollution tolerant and pollution indicator species. In these stations, the highest values of the pollutant parameters determined according to the Surface Water Quality regulation, and at the same time, the lowest values of Species richness, Diversity and Evenness were found in these stations. The regression of physicochemicals on species richness was examined. It was found that total phosphorus, orthophosphate and sulfate negatively affected species richness, while dissolved oxygen positively affected it. It was observed that pollution negatively affected dominant species, Species richness, Diversity and Evenness. At the stations where the number of species was higher, the amount of oxygen was measured higher than the other stations and it was thought that oxygen increased Species richness. In the stations with very poor ecological quality, Evenness values were found to be low and single species dominance was observed. At the 11th station with the lowest Evenness value, the eutrophic water indicator Craticula subminuscula constituted 337 of 518 individuals counted in the fall. Fistulifera saprophila accounted for 280 out of 406 individuals in summer. As a result, the stations that were found to be very polluted had low Evenness values, and the abundance and dominance of pollutant tolerant species were observed in these stations. The fact that the Evenness value approached the value of "1" in the stations that were relatively clean allowed for equal competition conditions in terms of parameters, a high number of species due to the ability of both sensitive and tolerant species to reproduce, and an equal distribution of species. The strikingly higher levels of pollutant parameters in the lower basins of the streams compared to the upper basins, high abundance of pollution tolerant species and low Diversity indicate that these stations are exposed to human impact. The fact that the water quality of the downstream basins of Saz and Dil streams, which were studied as a single station, and Yırım and Hisar streams, which were studied as two stations, is very poor and eutrophic suggests that the waste discharge is not cleaned properly, considering that there are dense industrial establishments and population in these areas. It can be said that both these streams and other streams flowing into the gulf leave a pollution load to Izmit Bay. When the increasing need for clean water and the sustainability of ecosystems are considered, it seems that healthy and controlled wastewater discharge is not only a need but also a necessity. It seems that many problems, especially the mucilage problem in the waters, are caused by the excessive increase in physicochemical parameters and the overgrowth of species tolerant to these chemicals, causing eutrophication and decreasing the quality of water. Eutrophication is inevitable as long as this situation continues. Therefore, efforts to improve water quality should be accelerated. Key words: Streams, Diatom Indices, Ecological Quality, Izmit Bay, Water quality