Unraveling novel microbial community interactions involved in the decline and fate of an under-ice diatom bloom

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Ice cover presents a logistical obstacle to our understanding of north temperate ecosystems. Reflecting this, ecosystem models frequently neglect or underestimate biological parameters associated with ice cover including potentially high rates of primary productivity. Yet current warming trends in global climate are reinforcing the need to focus attention on ice covered environments. We are growing more confident in our predictions of factors contributing to bloom development in these environments in the face of climate warming. However, identifying factors that lead to bloom decline and determining the fate of this biomass is more difficult owing to logistical considerations that challenge our abilities to study these blooms from 'rise to fall'. Existing collaborative relationships with binational agencies including Coast Guards and their ice-breaking assets combined with my close proximity to this study site offer a feasible approach to study the rise and decline of an expansive under-ice diatom bloom in Lake Erie. Central to this hypothesis-driven proposal are questions addressing the development, fate and foodweb interactions of Lake Erie's winter diatom bloom. Broadly, the proposal highlights the emerging role of parasitism beyond conventional controls such as nutrient supply and grazing, in regulating plankton dynamics during a poorly studied season. Amongst potential parasites identified by microscopy and transcriptomic analysis were chytrid fungi and oomycetes, fungal-like protists that are well-known pathogens causing disease in agriculture and aquaculture. Additional insights into novel host-parasite interactions came from the observation that the most abundant viral sequences mined from a bloom metatranscriptome aligned with the dsRNA Partitiviridae family whose natural hosts are fungi and plants. Given that chytrids are known parasites of diatoms, it is tempting to speculate that these viruses may help control chytrids which in turn are parasitic on the under-ice Lake Erie diatom community. The implications of these preliminary findings are manifold and provide the framework to hypothesize roles for diverse microbial interactions in regulating bloom fate whereby parasites effectuate a shunt reducing the amount of carbon that is directly exported to the benthos. In doing so, parasites transform bloom biomass into pools more readily consumed by diverse members of the pelagic food web.