Marine Ecology. 2019;40:e12544. wileyonlinelibrary.com/journal/maec | 1 of 10 https://doi.org/10.1111/maec.12544 © 2019 Blackwell Verlag GmbH 1 | INTRODUCTION Mangroves are coastal ecosystems found in tropical and subtropical regions around the world. They are found in the transitional zones between land, sea, and rivers; regarding their geographical distribu‐ tion, these ecosystems are found in the Americas, Africa, Asia, and Oceania (Brito et al., 2006). Mangroves can tolerate a wide range of sediment types, temperature changes, nutrient, salinity, and ox‐ ygen levels. Mangrove plant species vary in their tolerance to these factors, forming characteristic templates or zones of vegetation (Lovelock, 1993). This ecosystem provides various natural func‐ tions of great ecological and economic importance. Some of these functions include being an important nursery for fish, crustaceans, mollusks, reptiles, mammals, bird nesting, a site of carbon and nutri‐ ent accumulation, a location of marine biomass reconstruction and offering protection against coastal erosion (Alongi, 2002). Mangrove forests were first recorded in the Persian Gulf and Oman Sea by Eratosthenes (194–276 BC), a geographer from Alexandria (Safiari, 2002). Nowadays, mangroves are found along the Iranian beaches of the Persian Gulf and Oman Sea, as well as around Bahrain, Qatar, Saudi Arabia, and the United Arab Emirates (Bayoumi & El‐Nagar, 2009). Mangrove forests on the southern coast of Iran are given the common title “The Hara forests,” and they cover several locations between the 25°11′ and 27°52′ parallels longitude Received: 9 March 2017 | Revised: 27 December 2018 | Accepted: 1 March 2019 DOI: 10.1111/maec.12544 REGULAR PAPER A study of crude oil‐degrading bacteria from mangrove forests in the Persian Gulf Iman Fakhrzadegan 1 | Mehdi Hassanshahian 1 | Majid Askari Hesni 1 | Amir Saadatfar 2 1 Department of Biology, Faculty of Science, Shahid Bahonar University of Kerman, Kerman, Iran 2 Research and Technology Institute of Plant Production (RTIPP), Shahid Bahonar University of Kerman, Kerman, Iran Correspondence Mehdi Hassanshahian, Department of Biology, Faculty of Science, Shahid Bahonar University of Kerman, Kerman, Iran. Email: mshahi@uk.ac.ir Funding information Shahid Bahonar University of Kerman Abstract Mangroves are coastal ecosystems, found in tropical and subtropical regions around the world. They are found in the transitional zones between land, sea, and rivers. Petroleum hydrocarbons are the most common environmental pollutants, and oil spills pose a great hazard to mangroves forests. This research was focused on the isolation and characterization of crude oil‐degrading bacteria from mangrove ecosys‐ tems at the Persian Gulf. Sixty‐one crude oil‐degrading bacteria were isolated from mangrove samples (plant, sediment, and seawater) that enriched in ONR7a medium with crude oil as only carbon source. Some screening tests such as growth at high concentration of crude oil, bioemulsifier production, and surface hydrophobicity were done to select the most efficient strains for crude oil degradation. Molecular identification of strains was carried out by amplification of the 16S rRNA gene by PCR. The results of this study were indicated that the quantity of crude oil‐degrading bacteria was higher in the root of mangrove plants compare to other mangrove sam‐ ples (sediment and seawater). Also, identification results confirmed that these iso‐ lated strains belong to Vibrio sp. strain NW4, Idiomarina sp. strain BW32, Kangiella sp. strain DP40, Marinobacter sp. strain DW44, Halomonas sp. strain BS53, and Vibrio sp. strain DS35. The application of bioremediation strategies with these bacteria can reduce crude oil pollution in this important marine environment. KEYWORDS bacteria, biodegradation, contamination, mangrove, Persian Gulf