The main aim of the BaltVib sampling campaign was to analyse the microbial community composition in pelagic and benthic habitats with special focus on Vibrio spp. bacteria inside and outside of eelgrass meadows (Zostera marina), and selected macroalgae populations (Fucus spp.) in the salinity gradient of shallow coastal waters of the Baltic Sea.
The temporal extent of the dataset is 25.07.2021 to 02.09.2021. The geographic extent of the dataset is spanning from 9°52,655 E to 25°00,698 W and 60°06,547 N to 54°00,8666 S. The measurement depth ranges from 0.2 meters to 7 meters. Salinity ranges from 4 to 14. Environmental parameters measured are: conductivity, temperature, pH, Secchi depth, chlorophyll a, dissolved oxygen, ammonium, nitrate, nitrite, phosphate, silicate, grain size, dissolved organic carbon, dissolved nitrogen, particulate organic nitrogen, particulate organic carbon. Vibrio spp. colony forming units were counted using TCBS agar plates. Abundance of Vibrio vulnificus was determined by ddPCR in water and sediment samples as well as in Zostera marina surface biofilm. Cell counts by flow cytometry contain: Synechococcus, Picoeukaryota, Nanoeukaryota, high-nucleic acid bacteria, low-nucleic acid bacteria. Macrophyte abundance was measured for Zostera marina and Fucus spp..
Reference measurements of surface waters were collected during two RV Otzum cruises along the river Elbe in 2012 and 2013 (Ot2012_05: 21.-24.05.; Ot2013_05: 27.-30.05.2013). Temperature [°C], salinity, turbidity [NTU], and chlorophyll from fluorescence [µg/L] were measured by a PocketFerrybox System (values given to the time of sampling). Water samples were taken from the outlet of the system. Suspended particular matter (SPM) and chlorophyll a (Chl a) were filtered onboard on glas fibre filters (GFF, 47mm, 0,7 µm) and frozen at -25°C and -80°C immediately after sampling. Values were determined in the lab after the cruise within 2 months, for SPM via gravimetric analysis (IOCC recommendations) and for Chl a according to EPA Method 445. Water clarity and color were observed using a white Secchi disc with a diameter of 30 cm and a Forel-Ule color scale. The Secchi depth (SD) was recorded as a relative measure of water clarity at each in situ station during day time. At half SD the apparent color of the water above the submerged Secchi disc was determined using the Forel-Ule color scale. A Forel-Ule color scale is a classic tool used to differentiate the percieved color of water based on a scale from 1 (indigo blue) to 21 (cola brown). The measurements were conducted as recommended in literature (Garaba and Zielinski, 2015; Wernand, 2011; Wernand and van der Woerd, 2010). Measurements were part of the project DOMsense (01.11.2011 - 31.05.2014, KF2866501DF1)
Vibrio – microbes that are part of the natural bacterioplankton in temperate marine waters – have in recent years flourished in the Baltic Sea, probably stimulated by elevated surface water temperatures. Several Vibrio species are human pathogens. It is hence of great concern that Vibrio-related wound infections and fatalities have increased dramatically along the Baltic coasts. Future climate change is predicted to escalate this problem, posing a significant threat to human health and the Baltic tourism industry. However, the projections do not yet take into account the influence of ‘ecosystem engineers’ such as mussels and macrophytes on Vibrio diversity and abundance. Recent data indicate that in some of the ‘ecosystem engineers’ habitats the abundance of pathogenic Vibrio spp. is reduced. This opens up the option for nature-based solution (NbS) strategies to control pathogenic vibrios in the nearshore habitat where humans interact with the sea. However, climate change will also affect the structure and functioning of the ecosystem engineers, with as yet unknown consequences for the Vibrio populations in the Baltic Sea. BaltVib aims to delineate the current and future Vibrio status, determine biotic and abiotic key factors regulating Vibrio prevalence, and identify NbSs to mitigate the problem. This will be accomplished through interdisciplinary integration of marine, microbiological, molecular and socio-ecological expertise carried by partners from seven Baltic nations.