Family Spionidae is one of the largest families of the class Polychaeta (Williams, 2000). This is the first report of existence of this family in the southern reach of the Caspian Sea (Noor City). Sampling of bentic community in Noor coast during autumn 2004 revealed polychaetes that is differed from the ones reported earlier. The new samples were found to belong to spionidae family, not reported earlier from the Caspian Sea. This was approved by the concerned scientists at Zoological Museum Universitesparken of Denmark and South Australian Museum by observing the samples and pictures send to them.

This study was carried out in line with the Caspian Sea water transportation program to the central plateau on the Southeast shores of the Caspian Sea (Goharbaran region) since 2013-2014,Sampling was performed monthly and there were 8 stations at depths of 5,10 and 15 meters in 2 transects,The purpose of this study was to investigate the relationships between some physico-chemical parameters of water and total organic matter,distribution,abundance and biomass of Streblospio gynobranchiata (Spionoidae) in the different depths,The results showed that the highest abundance and biomass were in the Eastern transect with mean 1437,1±269,17 ind,m-2 and 0,711±0,131 g,m-2,respectively,A positive correlation was found between the abundance and biomass of S,gynobranchiata with TOM and at 0,01 level,salinity and water temperature at 0,05 level based on Pearson correlation test,The abundance and biomass of S,gynobranchiatain different seasons was fluctuating,with the highest abundance 1550,08±185,22 ind,m-2 and 0,775±0,09 g,m-2 recorded in winter and in January,respectively,So there was a significant difference between the abundance and biomass in different months (p<0,05),This could be due to the approach to the period of water disruption following the seasonal changes and the creation of a bioturbation in the seabed and a deposit feeder species,

In this study, polychaete worms in muddy-sandy coast of Gulshahr in Bandar abbas were investigated. Monthly sampling was conducted during one year from July 2005 until June using a hand corer.According to the results five families of polychaete worms, comprising 6 species, were recorded as macro fauna in the studied sites. The identified families were as following: nereididae, nephtyidae, spionidae, capitellidae, and glyceridae. The most species diversity belonged to family spionidae, while nephtyidae were the most abundant family. Results indicated that the polychaete worms were relatively sparse. This was more considerable in high intertidal areas.

This research was conducted with the aim of determining the biodiversity of Pertaran communities in three areas with mangrove cover and in 9 stations including one station in Gowatr Bay and 4 stations in each of Gowatr bay and Bahu Kalat on the eastern coast of Chabahar port. From each station, from the winter of 2019 to the fall of 2014, three sediment samples were collected seasonally for the separation and identification of sediments and one sample for the analysis of grain size and total organic matter of the sediments by Grab van Veen with a cross-sectional area of 0.028 square meters. In total, 12 genera belonging to 10 families were identified. Among the groups of the detected families of spionidae, the highest percentage of the average frequency with 13.70% was related to the Spionidae family. The survey of the density of the birds in total is 17800 ± 180 in the mentioned seasons, the average density of the birds in winter is 8720 ± 42 and the average density of the birds in the autumn is 9080 ± 181.63 in the mentioned seasons, the lowest average in winter is related to the Nereidae family: 0.5 600±67 and the most number was for Spionidae family: 1280±31.47 individuals in one square meter. The lowest average in autumn was related to the Nereidae family: 560 ± 32.65 and the highest to the Spionidae family: 1160 ± 62.94 individuals per square meter.

The present study has investigated polychaete worms in a muddy-sandy shore in Bandar Abbas in two sites. The first site which was receiving urban sewage of the city and was next to Terminal was named "Terminal". The second site was next to Goharshad Hotel and was named "Goharshad". Present research was conducted in a one year period starting from July 2005 until June 2006 on a monthly basis. Sampling was done using a hand corer. Results showed that five families of polychaete worms, comprising 6 species, were present as macrofauna in the sites. The identified families were: Nereididae, Nephtyidae, Spionidae, Capitellidae, and Glyceridae. The family Spionidae was most diverse while Nephtyidae were the most abundant family. Results indicated that the polychaete worms were relatively sparse. This was more considerable in high intertidal areas. Statistical analysis showed no significant difference between the two sites (p>0.05). Also it was clear that main habitat for the polychaete worms is low intertidal zone.

The aim of this study was to find the relations between macro-benthos dominant orders and environmental parameters using mono and multivariate analysis in the southern part of the Caspian Sea in 2009-2010. 160 samples were collected in four seasons and in eight transects perpendicular to the coast from depths of 5, 10, 20, 50 and 100 meters. Results of the current study showed that Polychaeta had the highest abundance compared to other main orders (Oligochaeta and Crustacea). Results also indicated that CCA test was more compatible with ecological evidences compared to mono and other multivarite anaylysis (PCA). The CCA results showed that Polychaeta was in inverse relationship with TOM and siltclay, while the Oligochaeta was directly related to sediments characteristics (TOM) and in inverse relationship with environmental parameter (DO%). The dominance of deposit feeder group of Polychaeta (Streblospio genus from Spionidae) indicates high level of organic matter in sediment and trophic status of ecosystem.

In aquaculture environments, organic enrichment significantly alters the chemical composition of pond sediments, leading to increased levels of organic matter, sulfur, and iron, alongside a reduction in pH. One promising approach to improve nutrient cycling and remediate contaminated sediments is the use of bioremediation through polychaetes. The selection of native species is crucial to mitigate the risks associated with introducing non-native, invasive species that may act as disease vectors or compete with native populations. This study, conducted from 2018 to 2020, aimed to identify and introduce polychaete species from the Persian Gulf with potential for bioremediation. A total of 41 sampling stations were selected across three provinces in the Iranian waters of the Persian Gulf—Hormozgan, Bushehr, and Khuzestan. Sediment samples were collected using a Van Veen grab sampler, washed with seawater, and analyzed for polychaete identification. The study identified 23 polychaete species from five families: Eunicidae (2 species), Capitellidae (3 species), Spionidae (5 species), Sabellidae (7 species), and Nereididae (6 species). The results highlight the potential of native polychaetes in bioremediation, enhancing the quality of aquatic substrates and contributing to the preservation of local ecosystems. These species play a vital role in the health and sustainability of ecosystems by degrading pollutants and improving environmental conditions. Thus, using native polychaetes for bioremediation can strengthen biodiversity and reduce the risks posed by non-native species in aquatic management and conservation.

Biodiversity and structure of the benthic macrofauna communities were studied in the southeast the Caspian Sea (Golestan Province – Iran) during one year from October 2014 to September 2015. Seasonal samplings were done at 6 stations in 3 transects. Depth, temperature, salinity, pH, E. C., total organic matter and grain size were measured. More than 4, 037 individuals belonging to five orders, Polychaeta, Oligochaeta, Bivalvia, Diptera and Amphipoda, and eight families including Nereididae, Spionidae, Amphartidae, Tubificidae, Smelidae, Cardiidae, Chironomidae and Gammaridae were identified. In terms of total individuals, Streblospio gynobranchiata, Hypania invalida and Cerastoderma lamarcki, were the most abundant species, and Polychaeta were dominant in the research region. The highest density of all species was observed in autumn (1515 ind m2) and the lowest was observed in summer (698 ind m2). The maximum diversity, richness, and evenness were 1. 36, 0. 6 and 0. 98, respectively. The results of distance-based redundancy analysis (db-RDA) showed that environmental factors such as salinity, depth and substrate type were all important in detecting the distribution pattern of macrobenthic species in the research region. The dominant species, S. gynobranchiata, was distributed in the areas with smaller grain size and higher TOM and muddy sediments and had the most correlation with salinity, temperature, pH and E. C. Species such as T. fraseri. H. invalida and P. robustoides showed more dependency on TOM and mud factors in the spring and summer, while their dependency became lower in autumn and winter. Abra ovate was less influenced by all factors except the substrate.

Polychaetes are important in determining the environmental status of seabed and their role in the food chain. Sampling of sediments in three areas of Beris, Ramin and Pasabandar was performed at 10 stations in the north of the Makoran Sea by Garb van-veen during three periods of pre-monsoon, monsoon, and post-monsoon winter with recordings of chemical physical parameters from November to March 2016. In the study identified 18 families of polychaetes communities it was found that the highest density in Monson period and in Post-Monsoon with 4364.67 ± 570 ind/m2 and the lowest density in Post-Manson period in Roman region with 225.33 ± 89 ind/m2.  In the pasaBandar area, the highest percentages belonged to the families Spionidae, Maldanidae and Cirratulidae, and to the families of Nephtydae, Phyllodocidae and Cirratulidae and to the Ramin family's Orbiniidae, Maldanidae and Cirratulidae. One-way ANOVA showed significant differences between stations and time periods (P <0.05). The highest densities of the polychaetes were estimated in terms of the period of Monsoon> Pre-Monsoon> Post-Monsoon period, respectively. Results of correlation between polychaete density and environmental factors of grain size sediment and TOM in pre-monsoon period showed a positive and significant correlation. There was no positive and significant correlation with environmental factors in monsoon period (P <0.05), but there was a significant positive correlation with grain size in post-monsoon period (p<0.05). The results showed that winter monsoon causes significant changes in the populations of the studied areas and the increase in density in monsoon can be due to the change of the currents direction and consequent increase of nutrient load in the area.

Desalination technology is growing due to population growth and water shortage. These kinds of activites can have environmental impacts where brine discharges into the sea. This study examined the effects of brine discharge from desalination plant Chabahar Konarak on the sea environment were used to study polychata assemblage. Sediment samples were sampled from 7 stations in pre monsoon and post monsoon in year 2011 using by van veen grab (0.025m2) samplers that 5 stations were around the discharge point and 2 station as controls. The results of the statistical analysis showed that the abundance and richness significances differences (P<0.05) between stations. The most abundance of polychaetes was occurred in station 6 with 3666.62 and 2079.92 individuals per m2 in pre and post monsoon respectively. While the lowest values observed in station1 in pre and post monsoon periods with 306.97 and 0 numbers in m2.The richness, diversity and evenness results indicated that the highest and the lowest values is observed in control stations 0.94, 1.07 and 0.67 in pre monsoon and station 1, zero in post monsoon. According to results, we observed different sensitivity of polychaete to brine discharges because abundance and ecological indices were decreased in stations near the discharges area comparing to control stations far from the brine discharges zone. Results of the CCA indicated that salinity and temperature effects on polychaete structure. The most frequancy family in this study was spionidae that it showed tolerance of this family to brine discharges. With monsoon occurrence of stress added to the study area where that the lowest abundance (0) in one station in post monsoon.