Effects of natural and anthropogenic stressors on fecundity, developmental abnormalities, and population recruitment in the intertidal gastropod Littorina saxatilis

Abstract

Coastal marine ecosystems in the Arctic are extremely vulnerable to human activities associated with oil and gas exploration, transportation and processing, and with industrial and urban development. The effects of complex pollutant mixtures interact with environmental factors. Here we assessed the effects of two anthropogenic and one natural factor on the reproduction, development and adult shell shape of the intertidal ovoviviparous gastropod Littorina saxatilis at 12 sites in the Barents and Norwegian Seas. The stressors studied were toxicity equivalency (TEQ) of the polycyclic aromatic hydrocarbons (PAH), the proximity of the site to urban/industrial locations as a proxy for urban pollution, and salinity. Total fecundity of the snails decreased at sites with low salinity but was not affected by PAH pollution. Allometric relationships of L. saxatilis shell shape varied between sites depending on the proximity of urban/industrial locations; the intrapopulation morphological disparity increased near urban sites. The frequency of abnormal embryos per brood and the incidence of females with abnormal embryos in the brood pouch increased at urban sites, especially under conditions of low salinity, but was unrelated to PAH pollution. Monte Carlo simulation showed that the registered embryotoxic effect of the proximity to urban/industrial locations was unlikely to result in a significant reduction of the population recruitment of L. saxatilis due to the high fecundity of these snails. Elucidation of the mechanisms of low sensitivity of L. saxatilis to PAHs in concentrations registered in our study and identification of the cause of embryotoxic effects associated with the proximity of urban/industrial locations are promising directions of further studies. Our results highlight the importance of considering multiple stressors when assessing anthropogenic impacts on coastal systems. We show that L. saxatilis can be an informative indicator of coastal urban pollution across its wide distribution range.