Population structure and secondary production of Hediste diadroma (Nereididae, Polychaeta) in the Bongam tidal flat, Masan Bay, Korea

This study aims to understand population dynamics and secondary production of a nereid polychaete Hediste diadroma in the Bongam tidal flat. Samples were collected on a monthly basis over two distinct periods: from May 2015 to April 2016 and from March 2018 to February 2019. The annual mean values for temperature, sand content, and total organic carbon in surface sediments were 18.1±9.6 ℃, 79.8±12.4% and 0.53±0.36%, respectively. Relationships between parameters such as body length (BL) versus the width of the third setiger (WS3), and dry weight (DW) versus WS3 were analyzed using a sample group of 56 intact individuals. The resulting equations were determined as BL=(28.575×WS3)-7.6462 with an R2 value of 0.93, and DW=1.3435×WS33.252 with an R2 value of 0.83. There was a notable decrease in annual mean density observed in 2018 (1,096±901 ind. m-2) compared to 2015 (1,938±1,724 ind. m-2), which could be attributed to higher temperatures and interspecies competition in 2018. Recruitment events were singular within each year, occurring in June 2015 and July 2018. The estimated secondary production (P) was 8.40g DW m-2 yr-1 with a mean biomass (B̅) of 5.18g DW m-2 (P/B̅= 1.6) from May 2015 to April 2016, and P= 3.38g DW m-2 yr-1 with B̅= 1.97g DW m-2 (P/B̅= 1.7) from March 2018 to February 2019. Based on these findings, it is suggested that the contribution of H. diadroma to energy flows in the benthic ecosystem of the study area accounts for approximately 3% (1.7gC m-2 yr-1) of the total energy flows (54.5gC m-2 yr-1).