Acoustic estimates of leaf height and biomass of Posidonia oceanica meadow in Gulf of Antalya, the eastern Mediterranean

Abstract

Vegetation cover on the sea floor plays an important role in marine health, and sonar systems can provide detailed observation and evaluation of sea floor vegetation under rapidly changing environmental conditions. Various acoustic techniques are available for this purpose. In this study, a split beam echo sounder operating at a frequency of 206 kHz was employed. Simultaneous dive expeditions were performed for direct acoustic observations. The aim of this study was to use the BioSonics EcoSAV software program to generate acoustic estimates of leaf height and create seasonal distribution maps in Posidonia oceanica meadows distributed between Lara and Manavgat in the Gulf of Antalya (Turkey). Calculation of program parameters by species and acoustic identification of P. oceanica were carried out with the aid of the PAST 3.05 (PAleontological STatistics) statistics program, enabling isolation of P. oceanica and other non-target species from the sea floor. The results revealed three major meadow beds in the study area. The maximum leaf height was observed in July (80–90 cm), followed by April/May (70–80 cm), with the shortest leaf height in January (40–50 cm). The biomass of the leaves varied seasonally between 100 and 1000 g/m2 and decreased by the seafloor depth in a year. This method proved effective for mapping and monitoring important seasonal habitat parameters such as the distribution of aquatic vegetation.

Keywords

• acoustic identification
• meadow
• leaf height biomass
• temporal and spatial distribution