EPILITHIC DIATOM-BASED ECOLOGICAL ASSESSMENT IN TAŞMANLI POND ( SINOP , TURKEY )

The common goal of the Water Framework Directive (WFD) published by The European Parliament and European Council and the Regulation on the Management of Surface Water Quality Directive (RMSWQ) published by the Republic of Turkey, Ministry of Forestry and Water Affairs, is to provide all water bodies to achieve a fine ecological status. These directives require the use of relevant biological quality elements and diatoms constitute an important group within these elements. The use of diatom based indices for assessing ecological conditions in inland water systems is increasing day by day. The current study was performed with the aim of determination of the ecological status of the Taşmanlı Pond based on epilithic diatoms, physico-chemical parameters and to estimate pond water quality using diatom indices. For this purpose, epilithic diatom and water samples were collected from 3 stations in the pond in monthly intervals from March 2008 to March 2009. The identifications of the sampled revealed presence of a total of 46 taxa in the sampled stations. Achnanthidium minutissimum (Kützing) Czarnecki, Nitzschia acicularis (Kützing) W. Smith, Navicula cincta (Ehrenberg) Ralfs in Pritchard and Navicula cryptocephala Kützing were the dominant taxa in all stations. According to Regulation on the Management of Surface Water Quality directive, the pond water was classified as III-IV quality class and trophic status changed from mesotrophic to eutrophic. Significant correlation was determined between LTDI (Lake Trophic Diatom Index) and EQR (Ecological Quality Ratio). The values of LTDI and EQR indicate that, pond water has class III (poor, moderately polluted site) water quality.


Introduction
Water is vital for any type of life on earth. The world contains aquatic and terrestrial ecosystems that are in very close contact with each other resulting in a delicate balance. The continuity of life is directly related to the continuity of this dynamic ecosystem interaction. Moreover, the continuity of socioeconomic inputs for humans is realized by the continuity of this system. Algae are primary producers of aquatic ecosystems and ensure the continuity of the systems they are involved in. This essential component creates the natural energy inputs of aquatic ecosystems and forms the most fragile link.
Aquatic systems, freshwater ecosystems in particular, are under a constant and strong pressure of human related activities (Gümüş 2010). Therefore, protection of natural water resources and the dominance of aquatic systems is one of the most important elements to be used in determination of future standard of life quality. Small physico-chemical changes in water initiate a chain 72 F. Gümüş & A. Gönülol reaction that affects both algae and our life quality. Phytobenthos is one of the biological quality elements that must be contained in The Water Framework Directive (WFD, "Directive 2000/60/EC" The European Parliament and European Council 2000) assessments of ecological status of freshwaters and diatoms are good environmental indicators and are often the main component of phytobenthos (Della Bella et al. 2007). Although diatoms are one of the important components of phytobenthos in aquatic systems, only some countries have yielded WFDcompliant phytobenthos tools specifically for lakes (Bennion et al. 2014). Diatoms are also taken into account as key organisms used as biological indicators in ecological quality analysis. Diatom-based water quality evaluation is a new process for Turkey and the first studies have begun after 2000s. Some of these studies were performed in Antalya River basin (Kalyoncu 2002 The present study was performed in order to determine the ecological status of Taşmanlı Pond based on epilithic diatoms and to estimate pond water quality using diatom indices.

Materials and Methods
Study Area Taşmanlı Pond (41°54´N, 35°02´E) is located in the southern part of Sinop ( Fig. 1) and covers an area of 222.000 square meters. The maximum depth of the pond is 15m and the minimum is 3-4m. The pond was constructed in 1977 by the General Directorate of State Hydraulic Works (DSI) for irrigation and it does not freeze in winter. The pond is free of industrial waste water discharge and juvenile common carp (Cyprinus carpio Linnaeus) were released a few times to the pond with the aim of breeding. Forest and scrub vegetation is observed in the drainage basin of the pond.

Sampling and Chemical Analysis
The samples were collected monthly from March 2008 to March 2009. Epilithic samples were collected from the stones by brushing, brought to the laboratory in plastic cups then preserved in 4% formalin solution. Diatoms were cleaned using hydrogen peroxide (H2O2) and diluted hydrochloric acid (3%) was added to purify calcium carbonate (Renberg 1990). After cleaning, the diatom frustules were washed with distilled water and rinsed. Clean diatom frustules were mounted in a synthetic resin (Naphrax). Diatom species were identified according to Krammer & Lange-Bertalot (1991a, 1991b, 1999a, 1999b, Round et al. (1990) and Sims (1996). Relative abundances of diatom species were evaluated by counting 300 valves per sample (Round 1953). Identified species were checked in algae databases and necessary taxonomic corrections were made (Guiry & Guiry 2017, Gönülol 2017). The author names were abbreviated according to Brummit & Powell (1992).
The surface water samples for physico-chemical analysis in laboratory were taken from all stations using plastic bottles. Environmental parameters such as dissolved oxygen of the water, temperature were measured in field with portable instruments. Chemical analysis were carried out according to APHA protocols (APHA 1998) and contained nutrients and ions such as chloride, nitrates, alkalinity, silica and phosphates. The water conductivity and pH were measured using a portable digital pH meter (Hach®HQ40d). The temperature and the dissolved oxygen values -as environmental parameters-of the water samples were measured in the filed using a portable handheld dissolved oxygen and temperature system (YSI®55).

Data Analysis
The average values and standard errors of all physicochemical analysis were computed using "Microsoft® Office Excel 2003". Diatom diversity "H´" (Shannon & Weaver 1949) and evenness "J´" (Pielou 1975) indexes were computed with Primer5 software (Clarke 1993). Trophic diatom indices were computed by two different softwares; i) Trophic Diatom Index for Lakes (TDIL) was computed with the DILSTORE software (Hajnal et al. 2009) and ii) Lake Trophic Diatom indices (LTDI) developed based on modification of the trophic diatom index (TDI) (Kelly & Whitton 1995) and Ecological Quality Ratio (EQR) were computed with the DARLEQII Software (WFD-UKTAG 2014).

Results
The identifications of the collected material showed that a total 46 taxa were present in the sampled stations of the pond (Table 1). The numerical distributions of the taxa with respect to the sampling months were given in Figure    According to the Regulation on the Management of Surface Water Quality Directives "Republic of Turkey, Ministry of Forestry and Water Affairs, 2015", the water bodies of all stations in Spring/Winter and Summer/Fall seasons have been identified as Class III and Class IV, polluted areas respectively. According to Trophic Classification System Limit Values in the directive, the water body of Taşmanlı Pond is in the limit values from mesotrophic to eutrophic waters. Index values of measured based on the sampled epilithic diatoms were given Table 3.

Discussion
Achnanthidium minutissimum (Kütz.) Czarnecki, was described as the most common and abundant diatom in well-oxygenated, neutral or alkaline lakes and streams with low or moderate concentrations of nutrients and organic pollution. It can also be present in high numbers in streams exposed to heavy metal pollution and in eutrophic inland waters (Bennion et al. 2014, Stenger-Kovács et al. 2007, Kelly et al. 2005. Some former studies suggested that taxa in the A. minutissimum complex can be assigned to morphological groups, each with differing ecological preferences though these morphological groups are not discontinuous (Potapova and Hamilton 2007). However, palaeoecological works indicates that a slightly change in planktonic diatoms suggest the early stages of nutrient enrichment rather than changes in non-planktonic diatoms (Bennion et al. 2004). Indeed, as revealed in the present study, A. minutissimum became a dominant species in spring months when the pond water began to be enriched with nutrients (Fig. 3). The common goal of both WFD and RMSWQT is to obtain water bodies with better ecological status. According to RMSWQT directives, the pond water were classified as III-IV quality class and the trophic status change from mesotrophic to eutrophic. Significant correlation was determined between LTDI (Lake Trophic Diatom Index) and EQR (Ecological Quality Ratio). The values of TDIL, LTDI and EQR indicate that the pond water have class III (poor, moderately polluted site) water quality. Consequently, it can be said that The Taşmanlı Pond is under pollution effect and diatom community content is closely related with water quality. Therefore, the epilithic diatom metrics can be used in monitoring in Taşmanlı Pond.