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A temporal analysis of the benthic polychaete community and its relationship with environmental variables was conducted by comparing coastal sediment samples collected in three separate sampling events between 1998 and 2013 from the southern end of the Southern California Bight (SCB). Environmental variables indicated a spatio-temporal increase of the sand fraction in sediment composition. Station stratification by depth from shallow to deep, and a reduction of trace metal enrichment (Co, Cr, Cu, Mn, Ni, Pb and Zn) was also found. There was a notable change in polychaete family composition due to high abundances and frequency of Spionidae, Chaetopteridae and Phyllodocidae in 2013, especially close to the Binational wastewater treatment plant discharge. An increase in polychaete abundance, richness and diversity was indicative of a probable relationship with regional weather conditions (El Niño-Southern Oscillation and recent drought events during sampling) along with local anthropogenic discharges of wastewater treatment plants in the area.

Pyrethroids are insecticides widely used to control pests and disease vectors in residential areas and agricultural lands. Pyrethroids are emerging pollutants, and their use is a growing concern because of their toxicity potential to aquatic organisms. Todos Santos Bay and the Punta Banda estuary, 2 coastal bodies located to the south of the Southern California Bight, were studied to establish a baseline of the current conditions of pollution by pyrethroids and fipronil. Eight pyrethroids, along with fipronil and its 2 metabolites, were determined in effluents from wastewater-treatment plants (n = 3), surface sediments (n = 32), and 3 locations with mussels (Mytilus californianus, n = 9). Bifenthrin, permethrin, and cypermethrin were the most common pyrethroids found in the study areas and were widespread in sediments, mussels, and wastewater-treated effluents. Fipronil and its metabolites were detected in mussels and wastewater-treated effluents only. Total pyrethroid concentrations in sediments ranged from 0.04 to 1.95 ng/g dry weight in the Punta Banda estuary (n = 13) and from 0.07 to 6.62 ng/g dry weight in Todos Santos Bay (n = 19). Moreover, total pyrethroids in mussels ranged from 1.19 to 6.15 ng/g wet weight. Based on the toxic unit data calculated for pyrethroids and fipronil for Eohaustorius estuarius and Hyalella azteca, little to no impact is expected to the benthic population structure. Environ Toxicol Chem 2017;36:3057-3064. © 2017 SETAC.

This systematic review analysed scientific publications to identify relevant research about the impact of alien polychaete species around the world, using the PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analysis) guide. The criterion for inclusion was studies published in English, with the key terms (e.g. ‘impact’, ‘alien species’, ‘polychaetes’) in the title, abstract and keywords. The literature search was conducted in Scopus and Web of Science from April to December 2020. The search resulted in 150 papers that included information about impact of alien polychaete species. Of these studies, 98% were published in the last 25 years, reporting on the impact of 40 species in 18 regions of the world. Sixty-one per cent of the research was conducted in the Baltic Sea, South-west Atlantic and Mediterranean Sea. The most frequent type of study was field surveys (46%) and the most studied system was open coast areas (36%). The species with the highest number of publications about their impacts were Ficopomatus enigmaticus, Marenzelleria viridis, Sabella spallanzanii and Boccardia proboscidea. Based on evidence of their most severe documented impacts in their introduced ranges, the impact mechanisms (IMos) of the alien polychaete species were strongly related to their biology and lifestyles. We found that species that build conspicuous reefs and tube-dwellers mainly showed physical and structural impact on ecosystems; shell-borers, mainly parasitism and infauna species, showed mainly chemical, physical and structural impacts on ecosystems. Some recommendations for the study of alien polychaete species are discussed.