The present study was conducted with the aim of identification of macrobenthos in the Yekshabe estuary in Persian Gulf. Sampling of macrobenthos was performed from spring 2015 for one year. It was carried out seasonally by the Van Veen Grab (0. 04 m ) at four stations, with three replications. The identified macrobenthos belonged to 51 families, 70 genera, 80 species, 4 classes (including Polychaeta, Malacostraca, Bivalvia, Gastropoda) and 5 Phyla. The average total density of macrobenthos was 760± 614 per square meter. The most frequently observed classes of macrobenthos belonged to Polychaeta (67. 8%), Malacostraca (18. 5%), Bivalvia (11. 6%) and Gastropoda (1. 2%), respectively. According to the results of the Kruskal– Wallis test, there was no significant difference between the macrobenthos classes among the different sampling stations. The highest values of the Shannon-Wiener index of diversity (3. 07) and the Margalef's richness index (4. 66) were observed in spring, whereas the highest value of the Pielou's evenness index (0. 95) was observed in autumn. The values of all indices at station 4 were the highest as compared to those of the others. The results of ANOVA test showed that the mean values of the indices were significantly different (p<0. 05) in different seasons, whereas the mean values were not significantly different at stations.

Artemia is one of the most important test organisms available for ecotoxicity tests. In this study the toxicity of five widely used herbicide formulations including: Paraquat, 2, 4-dichlorophenoxy acetic acid (2, 4-D), Trifluralin, Glyphosite and-Atrazine were compared using the ecotoxicity (Bioindicator), Artemia franciscana. Acute toxicity (48 h LC50) of five herbicides were determined via OECD standard methods. Artemia were hatched using standard methods and 12 h old nauplii were used for toxicity evaluation of herbicides. Nauplii were exposed to serial concentrations (more than 6 in triplicates) of each herbicid. Mortalities at 12, 24, 36 and 48 hours after exposure were recorded and the LC50 were calculated using the Probit software. The results showed that the mortality rate increased by increasing the exposure time in all herbicide toxicity assays. Besides 48 hours LC50 value of Paraquat, 2, 4-D, Trifluralin, Glyphosite and Atarzine were calculated at 15. 67, 12. 93, 11. 87, 164. 31 and 61. 34 mg L-1 in A. franciscana respectively. Glyphosate showed significantly less lethality and toxicity while Trifluralin and 2, 4-D showed the highest toxicity in A. franciscana among the examined herbicides. Then for sustainable agricultural activity, especially in areas that runoff water flows into aquatic ecosystems, it is highly recommended to use environmentally friendly herbicides like – Glyphosate as an alternative to the highly toxic herbicides like Trifluralin, Paraquat and 2, 4-D.