Acoustical identification and calibration of Posidonia oceanica in Antalya Bay

This PhD thesis has been carried out in the Gulf of Antalya using a scientific ecosounder with a frequency of 206 kHz and acoustical data of the marine survey made in 7 different months between 2011-2012. The study area of Posidonia oceanica meadows in the western Mediterranean coast of Turkey, as intense in terms of determining the presence has a different significance. The aim of the thesis is; acoustical identification of the P. oceanica species using EcoSAV (Eco Submerged Aquatic Vegetation) and VBT (Visual Bottom Typer) commercial software. Based on the calibrating species-specific parameters in the software that will provide this definition; estimated biomass quantities and leaf height. End of this result draw of distribution maps based on seasonally. The same time the investigation of the bottom structural feature of the environment it is growing. For the first time with a method applied in the world, biomass quantities were estimated by performing energy detection from P. oceanica via VBT. During the calculations by taking seasonal differences into consideration, regression analyzes were performed from the length-weight data for use in the biomass calculations. The regression equation obtained by calibrating the biomass and the acoustic energy (sa) calculated from these data was used in the biomass cycle of the acoustic energy. Thus, it forms the basis for the determination and mapping of density variations and seasonal distributions. In addition, ANOVA and ANCOVA were used to test for differences for acoustically estimated biomass due to the depth and season. According to these results, there was a difference according to depth when seasonal difference was not observed, and it was determined that as the depth increased, the amount of biomass decreased. When the seasonally obtained biomass-related distribution maps of the study area were examined, it was determined that the study area formed 3 different beds. The highest estimated biomass is in two seasons; in July above 4000 (g/m–2) and in April / May above 2000 (g/m–2), the lowest biomass quantity was 800 (g/m–2) in January respectively. The vegetation height in the area determined by EcoSAV where it is distributed. The presence of 3 beds in the study area was determined by seasonal distribution of leaf length. The results of the spatial and temporal distribution have been found to be correlated with biomass-related outcomes. According to these results, the highest leaf size was determined at 80–90 cm in July and April/May, and the minimum was determined as 30–40 cm in January. The seawater temperature and salinity data from the hydrological properties of the study area were sampled and recorded monthly where the materials of this thesis were obtained. Evaluations were also made on the distribution of the specimen using these data. In line with these records, the highest temperature in the area where Posidonia oceanica meadows grew was determined to be 29–30 °C and salinity was maximum 39-40 ‰ in August. It has been understood that these temperature do not yet constitute a negative situation in order to maintain the survival of the species. In addition, the structural characteristics of bottom sediment were tried to be determined with VBT and it was determined that P. oceanica was distributed on hard rocky ground due to the determination of the bottom structure of the bottom sediment. Finally, within the results obtained from this study, it was found that the P. oceanica species living in the study area was a strong scatterer that can be acoustically identified and the acoustic characteristics affecting the acoustic scattering were determined. With this type of features identified in the workspace, it has revealed the species' availability in all seasons. It was concluded that in the research conducted with 3 different analysis and method applications in order to determine the distribution, dynamics and the living area of the acoustically, the results are compatible with each other in supporting the results. In the research carried out with 3 different analyzes and methods in order to determine the acoustical distribution, habitat and the dynamics, it is concluded that the results are compatible with each other. It is also worth noting that it may be advisable to identify the structural dynamics of the leaf structure (CO2, O2, photosynthesis rate, young-aged etc.) acoustically containing important information to aid in the understanding of vegetation and to use this data in similar investigations.