Evidence that viral abundance across oceans and lakes is driven by different biological factors

Abstract

1. Samples from 16 lakes in central (n = 145) and western (n = 12) North America, the coastal northeast Pacific (n = 302) and the western Canadian Arctic Oceans (n = 142) were collected and analysed for viral, bacterial and cyanobacterial abundances and chlorophyll-a concentration.2. Viral abundance was significantly different among the environments. It was highest in the coastal Pacific Ocean and lowest in the coastal Arctic Ocean. The abundances of bacteria and cyanobacteria as well as chlorophyll-a concentrations also differed significantly among the environments, with both bacterial abundance and chlorophyll-a concentration highest in lakes. As a consequence, the association of these variables with viral abundance varied among the environments. 3. Discriminant analyses with the abundance data indicated that the marine and freshwater environments were predictably different from each other. Multiple-regression analysis included bacterial and cyanobacterial abundances, and chlorophyll-a concentration as significant variables in explaining viral abundance in lakes. In regression models for the coastal Pacific Ocean, bacterial and cyanobacterial abundances were significant variables, and for the coastal Arctic Ocean viral abundance was predicted by bacterial abundance and chlorophyll-a concentration. 4. The relationship of viral and bacterial abundance differed between the investigated freshwater and marine environments, probably because of differences in viral production and loss rates. However, freshwaters had fewer viruses compared to bacteria, despite previously documented higher burst sizes and frequencies of infected cells, suggesting that loss rates may be more important in lakes. 5. Together, these findings suggest that there are different drivers of viral abundance in different aquatic environments, including lakes and oceans.

Warming shifts top-down and bottom-up control of pond food web structure and function

“…One of the most surprising results of our study was that viruses responded negatively to the presence of fish. Viral abundance is positively correlated with trophic status across freshwater and marine ecosystems [65], a result that may indicate that virus abundance tracks that of bacteria or phytoplankton [66]. However, the response of viral biomass to our treatments closely reflected that of the zooplankton (figure 1).…”

Seasonal variation in viral-induced mortality of bacterioplankton in the water column of a large mesotrophic lake (Lake Biwa, Japan)

“…However, temporal resolutions of our data (sampling with a monthly interval) were probably too low to capture temporal dynamics of cyanophages and their hosts (picoplanktonic cyanobacteria display seasonal peaks during warm seasons in Lake Biwa; Nagata 1986, Maeda et al 1992. Thus, we do not exclude the possibility that cyanophages are important components of viral communities in Lake Biwa, as suggested in other lakes (Maranger & Bird 1995, Clasen et al 2008. The difference in results of correlation analyses between Honjo et al (2007) and the present study might be explained by a large variation, over seasons and years, in the mode of virus-host couplings in Lake Biwa.…”

“…Maranger & Bird (1995) found that viral abundance in Canadian lakes was positively correlated with chl a, but not with bacterial abundance; the authors interpreted these results as indicating that cyanophages largely contribute to total viral abundance, although other possibilities were not excluded. More recently, Clasen et al (2008) have reported cyanobacteria and chl a to be significant predictor variables of viral abundances in 16 lakes in central and western North America. In contrast, the present study data suggest a tight coupling between bacteria and viruses: a large fraction (76%) of the variation in viral abundance was explained by bacterial abundance alone.…”

Seasonal patterns of viral, microbial and planktonic communities in Sidi Salem: a freshwater reservoir (North of Tunisia)

“…Viruses play an important role in regulating carbon and nutrient fluxes, food-web dynamics and microbial diversity in aquatic systems (Suttle, 2005;Jacquet et al, 2010;Breitbart, 2012). The factors that influence viral abundance and dynamics in aquatic environments are complex and are found to vary with aquatic ecosystems (Clasen et al, 2008). Studies have shown that the viral abundance is influenced more by the bacterial abundance in marine environments and by chlorophyll a concentration in nutrient-rich lakes (Pradeep Ram et al, 2010).…”