Effect of harvesting season and location on the microbial quality and community composition of the edible sea urchin (Echinus esculentus) gonads

Despite the crucial role of microbial community composition in the quality and stability of seafood, little emphasis has been given to the microbiota profile of sea urchin gonads. This study investigates the microbial quality and community composition of sea urchin gonads (Echinus esculentus) as a function of harvesting season (autumn, winter, spring, and summer) and location (one site proximal to urban activity areas while the other is located in open water close to the coastline). Significant season-dependent variations were found in psychrotrophic and aerobic plate counts, with higher counts in summer, followed by autumn, spring, and winter. H₂S-producing bacteria and Pseudomonas spp. counts were unaffected by harvesting season or location. Sea urchin gonad microbial composition proved resilient and dynamic, primarily shaped by seasonal variations, and minimally influenced by location. Winter and spring samples exhibited higher diversity than autumn and summer. Key genera like Pseudomonas, Psychromonas, Vibrio, Chryseobacterium, Shewanella, and Photobacterium varied seasonally. Pseudomonas, Vibrio, and Photobacterium are crucial in assessing microbial quality and safety due to their roles as specific spoilage organisms (SSOs) and, in some cases, human pathogens. Though relative abundances differed slightly between locations, harvesting location did not notably impact microbial community shaping in gonads. However, the results suggest that harvesting locations near areas with urban activity may lead to contamination with specific bacterial species, possibly due to water quality variations. These findings emphasize the importance of considering seasonality when evaluating sea urchin gonad microbial quality. Identifying key genera enhances insights into potential SSOs and human pathogens, enhancing food safety considerations in the consumption of raw or lightly processed sea urchin gonads and guiding the development of preservation methods to extend shelf life.