Viral ecology of organic and inorganic particles in aquatic systems: avenues for further research

Abstract

Viral abundance and processes in the water column and sediments are well studied for some systems; however, we know relatively little about virus-host interactions on particles and how particles influence these interactions. Here we review virus-prokaryote interactions on inorganic and organic particles in the water column. Profiting from recent methodological progress, we show that confocal laser scanning microscopy in combination with lectin and nucleic acid staining is one of the most powerful methods to visualize the distribution of viruses and their hosts on particles such as organic aggregates. Viral abundance on suspended matter ranges from 10 5 to 10 11 ml -1. The main factors controlling viral abundance are the quality, size and age of aggregates and the exposure time of viruses to aggregates. Other factors such as water residence time likely act indirectly. Overall, aggregates appear to play a role of viral scavengers or reservoirs rather than viral factories. Adsorption of viruses to organic aggregates or inorganic particles can stimulate growth of the free-living prokaryotic community, e.g. by reducing viral lysis. Such mechanisms can affect microbial diversity, food web structure and biogeochemical cycles. Viral lysis of bacterio-and phytoplankton influences the formation and fate of aggregates and can, for example, result in a higher stability of algal flocs. Thus, viruses also influence carbon export; however, it is still not clear whether they short-circuit or prime the biological pump. Throughout this review, emphasis has been placed on defining general problems and knowledge gaps in virus-particle interactions and on providing avenues for further research, particularly those linked to global change.

A multitrophic model to quantify the effects of marine viruses on microbial food webs and ecosystem processes

“…On the other hand, it is unlikely that purely exponential decay of viruses and type-I interactions with host populations (as we proposed) is to be expected. For example, marine viruses can be the target of grazing (Gonzalez and Suttle, 1993), adsorb to and aggregate on larger particles, such as marine snow (Weinbauer et al, 2009), and their life history traits, for example, replication rates (Lindell et al, 2007), burst sizes (Wilson et al, 1996) and latent periods (Baudoux et al, 2012), also depend on the physiological status of hosts. All of these factors would potentially give rise to higher-order loss terms or deviations from models with strict type-I functional responses (for example, see Weitz and Dushoff, 2008).…”

Potential impacts of black carbon on the marine microbial community

“…Viral abundance was enumerated by flow cytometry (FC), which currently cannot be combined with virus-aggregate disruption agents such as methanol, since it interferes with the staining dye (Weinbauer et al 2009). Thus, bulk measurements represent likely free viral abundance (FVA).…”

Biophysical characteristics of a morphologically-complex macrotidal tropical coastal system during a dry season

“…Sediment particles in King Sound, in the southern part of the Kimberley but with similar water depths to our study area, were indeed shown to be bound together by organic matter, with these 'flocs' embedded with larger sized phytoplankton (e.g., diatoms, dinoflagellates and ciliates) and faecal pellets (Wolanski and Spagnol, 2003). Indirect scavenging and/or aggregation of planktonic organisms (including picoplankton, bacteria and viruses) onto a range of particle types is well documented in systems with high particle loads (e.g., lakes, estuaries) but also across a range of systems from coastal to oceanic (Simon et al, 2002;Turner, 2002;Weinbauer et al, 2009). The in situ particle structure is known to have a strong impact on nutrient adsorption and bacterial processing of suspended materials (e.g., Chang et al, 2003), though again, nothing is known of the rates and/ or importance of such processes in the Kimberley.…”