Environmental Influences onVibrioPopulations in Northern Temperate and Boreal Coastal Waters (Baltic and Skagerrak Seas)

Abstract

Even if manyVibriospp. are endemic to coastal waters, their distribution in northern temperate and boreal waters is poorly studied. To identify environmental factors regulatingVibriopopulations in a salinity gradient along the Swedish coastline, we combinedVibrio-specific quantitative competitive PCR with denaturant gradient gel electrophoresis-based genotyping. The totalVibrioabundance ranged from 4 × 10³to 9.6 × 10⁴cells liter⁻¹, with the highest abundances in the more saline waters of the Skagerrak Sea. SeveralVibriopopulations were present throughout the salinity gradient, with abundances of single populations ranging from 5 × 10²to 7 × 10⁴cells liter⁻¹. Clear differences were observed along the salinity gradient, where three populations dominated the more saline waters of the Skagerrak Sea and two populations containing mainly representatives ofV. anguillarumandV. aestuarianusgenotypes were abundant in the brackish waters of the Baltic Sea. Our results suggest that this apparent niche separation within the genusVibriomay also be influenced by alternate factors such as nutrient levels and high abundances of dinoflagellates. AV. cholerae/V. mimicuspopulation was detected in more than 50% of the samples, with abundances exceeding 10³cells liter⁻¹, even in the cold (annual average water temperature of around 5°C) and low-salinity (2 to 4‰) samples from the Bothnian Bay (latitude, 65°N). The unsuspected and widespread occurrence of this population in temperate and boreal coastal waters suggests that potentialVibriopathogens may also be endemic to cold and brackish waters and hence may represent a previously overlooked health hazard.