The aim of this paper is to present an analytical study of gonad index (GI) and repletion index (RI) of Holothuria (Holothuria) tubulosa Gmelin, 1791 (Echinodermata Holothuroidea Holothuriidae). The study is based on biomonitoring data collected from February 2014 to January 2015 in the Oran coast. The gonad index of Holothuria tubulosa is analyzed to show the reproductive cycle and its relationship to environmental parameter conditions. Samples of 15 to 20 individuals were collected monthly at three stations on the Oran coast (La Madrague, Cap Carbon, and Ain Franin). The sex ratio of all sampling was found as (female: male) 0.8:1.2 with no significant difference between sites (X 2 = 2.18 ; df=4 ; p>0.05) and is also not significant regarding the seasons (spring, summer, autumn, winter) (X2= 3.03 ; df=6 ; p>0.05). Sea cucumber reproduction occurred in September at Cap Carbon and Ain Franin with values of Gonad index (GI) that are 0.33± 0.52 % and 0.22± 0.52 % respectively. At the La Madrague site, the spawning occurred in October with a value of GI of 1.49±2.03 %. It was observed that seawater temperature has a positive correlation with Gonad index (GI) and no correlation with Repletion index (RI).

This study assesses the characteristics of the metallic trace elements (Fe, Cd, Cu, Pb and Zn) in the Paracentrotus lividus gonads. The physiological indices evolution (RIm and GIm) was adopted in order to determine the laying period of this echinoid; and to support the hypothesis that this species may be considered as an excellent bioindicator in the marine environment. For this purpose, two edible sea urchin populations with a diameter between 41 and 71 mm were sampled. This samples were taken from two different sites, Salamandre area (presence of rocky seabed rich of photophilic algae, with less biodiversity), and Sidi Lakhdarin area (presence photophilic algae and Posidonia oceanica, more biodiversity). Each sample was evaluated by the coupled plasma mass spectrometry (ICP-MS) method. The results obtained show that there is a significant variation (p<0.005) of physiological indices (RIm and GIm) over time. Besides, an important spawning increase is observed during spring and autumn. The results revealed that gonads metallic contaminations were present in all samples, with very heterogeneous concentrations. Also, it demonstrates that the metallic contamination existed in all seasons, with a clear demarcation of zinc and iron. The zinc quantity is 2.159 mg/l in Sidi Lakhdar and 1.413 mg/l in Salamandre; and the iron quantity is 2.088 mg/l in Sidi Lakhdar and 1.888 mg/l in Salamandre. Unlike zinc and iron, copper and cadmium have small amounts in the two sites. In the autumn, the cadmium quantity is 0.005 mg/l in the two sites; and the copper quantity is 0.068 mg/l in Sidi Lakhdar and 0.065 mg/l in Salamandre. Consequently, this marine species accumulates large quantities of these toxic metals according to the bioavailability of the pollutant in the surrounding environment.