Benthic ecology of Vibrio spp. and pathogenic Vibrio species in a coastal Mediterranean environment (La Spezia Gulf, Italy)

Abstract

We carried out a 16-month in situ study to investigate the ecology of Vibrio spp. and pathogenic Vibrio species in coastal sediments of the Mediterranean Sea, employing multiple-regression analysis to reveal the major environmental factors controlling their occurrence in the benthic environment. In addition, association between vibrios and sediment-inhabiting meiofauna, which is a major component of benthic ecosystems, was investigated. Culturable and total Vibrio spp. estimates by most-probable-number technique coupled with standard polymerase chain reaction (PCR) and real-time PCR methods, respectively, were at least one order of magnitude higher in sediment than in seawater. In addition, potential human pathogenic species Vibrio cholerae, Vibrio vulnificus and Vibrio parahaemolyticus occurred in the sediment with V. parahaemolyticus being the most frequently found. In the pelagic environment, 60% of total variance in culturable Vibrio data was explained by sea surface temperature (40%), salinity (13%) and organic matter concentration (7%). In the benthic environment, sea surface temperature was the only factor that significantly affected culturable Vibrio occurrence although it explained only 25% of total variance, suggesting that additional unexplored factors may play a role as well. No correlation was found between culturable Vibrio spp. concentrations and the abundance of harpacticoid copepods in the sediment whilst a negative correlation was found between Vibrio spp. and nematode abundance which accounted for almost 90% of the total meiofaunal density. Taxonomic analysis revealed that selective bacterial feeders accounted for nearly 50% of the total nematode community and included genera such as Terschellingia, Molgolaimus and Halalaimus, suggesting that top-down control by nematode grazing may be an important factor affecting Vibrio occurrence in these sediments. It is concluded that the benthic marine environment may function as a reservoir of Vibrio spp. and potential pathogenic vibrios whose ecological features appeared substantially different from the ones recognised in the pelagic environment.

Temporal and Spatial Distribution Patterns of Potentially Pathogenic Vibrio spp. at Recreational Beaches of the German North Sea

“…Although previous studies in different regions showed that sediments can harbour high amounts of Vibrio spp. [12,40,63,64], such a high difference in the number of viable cells between sediment and water seems to be extraordinary. The possibility of an active benthic lifestyle of Vibrio spp.…”

“…[15]), few environmental studies have considered the sedimentary matrix (e.g. [39,40]), thus neglecting an important component with regard to the assessment of possible health risks.…”

Influence of Environmental Factors onVibriospp. in Coastal Ecosystems

“…Interestingly, negative correlations have also been described between temperature and total vibrios in the waters of India (46,67) and Louisiana (68). Temperature has also been positively correlated to total vibrios in mussels (59) and sediment (47,64,69). A 2003 study identified a distinct temperature effect when Vibrio coralliilyticus infected the coral Pocillopora damicornis; V. coralliilyticus pathology was higher at 27°C and 29°C than at 25°C (70).…”

“…Although these studies have not focused on the top three human pathogens, they are important because they shed light on the ecology of naturally occurring vibrios and because of the relationships with pathogens with which they may exchange genetic material. Positive relationships have been described between temperature and total vibrios in the waters of Germany (58,59), North Carolina (31,55,60,61), the country of Georgia (62), the state of Georgia (63), Italy (64,65), South Africa (66), and Germany (47). Interestingly, negative correlations have also been described between temperature and total vibrios in the waters of India (46,67) and Louisiana (68).…”

Dangerous hitchhikers? Evidence for potentially pathogenic Vibrio spp. on microplastic particles

“…Environmental parameters, such as temperature, salinity or plankton abundance have an effect on Vibrio spp. communities and abundances (Blackwell and Oliver, 2008;Caburlotto et al, 2010;Drake et al, 2007;Martinez-Urtaza et al, 2008;Thompson et al, 2004b;Turner et al, 2009;Vezzulli et al, 2009). Vezzulli et al (2010) and Schets et al (2010) identified seawater temperature as a key factor influencing the presence of Vibrio spp., for instance it is well documented that V. parahaemolyticus favours warmer water temperatures (Sobrinho et al, 2010).…”