Diversity and seasonal variability of Heterobranchs in Tulamben waters, Bali, Indonesia

Abstract

This study examines the ecological traits of heterobranchs, which are found in various habitats associated with reef regions. We use data on heterobranchs abundance, depth, substrates, and seasonal observations to analyze their ecological traits, as these factors are often under studied. The species diversity of heterobranch species found in Tulamben, Bali is exceptionally rich. From a total of 41 surveys carried out at depths between 0 and 25 m every week in a one-year period, more than 144 species of heterobranchs belonging to 63 genera were recorded. A total of 1001 individuals were recorded during our survey efforts with 645 individuals in the dry season and 356 during the wet season. Hypselodoris roo and Mexichromis trilineata are the most abundant species of heterobranch recorded in this study. Despite these numbers, no significant difference was found between the abundance of heterobranchs between the dry and wet seasons; however, depth was a significant factor in determining heterobranchs abundance and species richness. The highest abundance was recorded for zone C (between 15 and 20 m depth) where 437 individual heterobranchs were recorded. The lowest abundance of heterobranchs was recorded for zone A (5–9 m depth) where only 72 individuals were recorded. Substrate preference was also observed among the individuals in which the highest abundance of heterobranchs were found on sponges in both dry (47.9 %) and wet (41 %) seasons. The second most dominant substrate was recorded as sand, accounting for 25 % relative abundance in both dry and wet seasons. To learn more about the seasonality of heterobranchs, further research considering tides, temperature, and other environmental factors needs to be considered.