Links between viruses and prokaryotes throughout the water column along a North Atlantic latitudinal transect

Viruses are an abundant, diverse and dynamic component of marine ecosystems and have a key role in the biogeochemical processes of the ocean by controlling prokaryotic and phytoplankton abundance and diversity. However, most of the studies on virus–prokaryote interactions in marine environments have been performed in nearshore waters. To assess potential variations in the relation between viruses and prokaryotes in different oceanographic provinces, we determined viral and prokaryotic abundance and production throughout the water column along a latitudinal transect in the North Atlantic. Depth-related trends in prokaryotic and viral abundance (both decreasing by one order of magnitude from epi- to abyssopelagic waters), and prokaryotic production (decreasing by three orders of magnitude) were observed along the latitudinal transect. The virus-to-prokaryote ratio (VPR) increased from ~19 in epipelagic to ~53 in the bathy- and abyssopelagic waters. Although the lytic viral production decreased significantly with depth, the lysogenic viral production did not vary with depth. In bathypelagic waters, pronounced differences in prokaryotic and viral abundance were found among different oceanic provinces with lower leucine incorporation rates and higher VPRs in the North Atlantic Gyre province than in the provinces further north and south. The percentage of lysogeny increased from subpolar regions toward the more oligotrophic lower latitudes. Based on the observed trends over this latitudinal transect, we conclude that the viral–host interactions significantly change among different oceanic provinces in response to changes in the biotic and abiotic variables

A new view on karst genesis

Karst terrains and their specific landforms, such as sinkholes and caves, have been thoroughly studied from the second half of the nineteenth century. However, karst genesis remains a puzzling issue to this day. The results of the recent studies of ocean floor and the results obtained by drilling deep oil boreholes have raised doubts about the existing explanations of the karst landforms development and encouraged the emergence of new views on this subject matter. According to the new hypothesis, the majority of karst landforms were formed at great depths beneath sea level where dissolution of carbonates increases dramatically. Underwater dissolution first caused the formation of karst depressions and the primary network of karst conduits elongated along the existing fractures. This process was followed by further expansion of the conduits and the formation of spacious caves due to the water regression and the action of turbulent flows. It is considered that the introduction of the new concept would accelerate the development of karstology and improve the principles and methods for solving numerous practical problems such as the abstraction of quality drinking water and the research of oil, gas and bauxite deposits