The aquatic annelid community in Lake Al-Delmage (Iraq)

Lake Al-Delmage is part of the middle section of a main outfall drain located south of Baghdad (Iraq). This study focuses on the community structure of aquatic annelids and the physico-chemical variables in this lake. Six stations along the lake were chosen for sample collection in the period from January 2013 to January 2014. The results revealed that the lake water is oligohaline, with salinity levels ranging from 1.5 to 14.6 ‰ and temperatures ranging from 9°C to 33°C; hydrogen ion concentrations (as pH) ranging between 7 and 9. Water was well aerated with dissolved oxygen concentrations values ranging between 6 and 12 mg L−1, and BOD values ranging between 1.5 and 3 mg L−1. The lake water was considered as very hard, since the total hardness values ranging between 825 and 8466 mg L−1. From samples collected during the study period, 1,885 aquatic annelid specimens were identified. Of these, 58% belonged to the family Aeolosomatidae (Polychaeta); the remaining taxa belonged to subfamilies of the family Naididae (Oligochaeta - Clitellata): subfamily Naidinae (6%), subfamily Tubificinae (36%), and subfamily Rhyacodrilinae, Branchiura sowerbyi (3%). Two species of Aeolosomatidae were recognized, Aeolosoma hemprichi and Aeolosoma variegatum. Naidid worms of the subfamily Naidinae included three species, Paranais litoralis, Dero (Aulophorus) furcatus, and Stylaria lacustris. The highest frequency percentage of 23.6% was recorded for P. litoralis. The subfamily Tubificinae was represented by five species - Limnodrilus hoffmeisteri, L. profundicola, L. claparedeanus, L. udekemianus, and Tubifex tubifex. Limnodrilus claparedeanus was the most abundant species, comprising 53% of the total number of Tubificinae. Seasonal fluctuations showed spatial and temporal variations of species richness. The highest species richness was recorded in the stations near the feeder canal, and temporally during June and October 2013.