Depth-gradient biometrics of the invasive seaweed Caulerpa taxifolia spreading northward along the Turkish Aegean coast

OpenAlex İngilizce

The presence of the invasive green alga Caulerpa taxifolia has been documented in the Turkish Aegean Sea, prompting a comprehensive investigation into its depth biometry and ecological interactions. This study sought to assess the distribution, density, and morphological characteristics of C. taxifolia at four distinct depths (10, 15, 20, and 30 m) in Dikili Bay, İzmir, during the summer of 2024. A total of 321 sampling stations were surveyed, and C. taxifolia specimens were identified at four locations. Sampling was performed by SCUBA divers using a 0.4 x 0.4 m quadrat. Biometric measurements included shoot density, stolon length, frond length, and number of pinnae per frond. Environmental parameters such as temperature, salinity, pH, and light intensity were simultaneously recorded to evaluate their influence on algal growth. The internodal distance (frond) on stolon exhibited a range from 18.4 mm at the 15-m depth to 38.4 mm at the 30-m depth. The maximum shoot density (1397 shoots/m2) was recorded at the deepest sampling depth. The minimum density of 343 shoots/m2 was observed at 15 m. The number of fronds (shoots) per stolon showed a gradual decrease with depth up to 20 m. The length of the stolons ranged from 178 mm to 355 mm, with the shortest stolon occurring in the shallowest water, followed by a gradual increase with increasing bottom depth. Frond length exhibited a range from 49.9 mm at 10 m to 87 mm at 20 m, followed by 71 mm at 30 m. Frond width remained within a narrow range of 0.855 cm to 1.1139 cm across the bottom depth. The widest frond was observed at 30 m, while the narrowest frond was recorded at 10 m. A total of 35% of the specimens examined at 10 m were found to be budded, 12% at 15 m, and 7% at 20 m, and 20% at 30 m. The number of branchlets ranged from 6-18 to 156-210, with an average of 76 to 94 and 10-12 per 1 cm frond length.