Final Report Summary - MINOS (Microbial Network Organisation) The biology of the ocean's pelagic food web covers a size range of about 8 orders of magnitude (viruses to whales). Half of this range goes from the smallest organisms visible to the naked eye (copepods ~ 1 mm) down to viruses (~0.1 um), forming what is known as the marine microbial food web (MMFW). This "invisible" part totally dominates the biodiversity. Since virtually all pelagic primary production is by microbes, the MMFW also dominates the fluxes of energy and matter in the ocean. MINOS was a project trying to understand the mechanisms linking biodiversity and ecosystem functioning in this central part of the marine ecosystem. Constructing models that build on the organisms' strategic dilemma of dividing available resources between competition and defense, we have been able to produce unifying explanations for experimental results that otherwise seemed contradictory. Reapplying the same principles at successive levels of resolution, these models get a hierarchical "Russian doll" structure: at a food web level with trophic interactions between communities, at an intermediate level of species forming the communities, and at an inner level representing the strains of each species. The resolution to strain level is novel to such models and may seem overly detailed, but was found to increase the explanatory power of these models considerably. It allows an analysis of the balance between competitive and defensive properties needed for a species to become numerically dominant, an aspect highly relevant to the ongoing debate of why SAR 11 (a marine bacterium) has become the world's probably most abundant organism. It also resolves previously suggested paradoxes in the behavior of host-virus systems in the laboratory and in nature, and it suggests that the dominance of dormant bacteria in the ocean may be a result of their need for expensive defensive mechanisms, rather than a lack of competitive ability for scarce resources as previously assumed. It also allows one to ask questions such as how the cost of resistance associated with a molecular defense mechanism will affect the shunting of material out of the particulate food chain and back towards dissolved material via viral lysis. With these models, the potential for linking molecular data to ecosystem function seems much better than was the case with the previous versions of conceptual models of the MMFW. MINOS has thus made a significant contribution to a modernized and unifying conceptual understanding of the MMFW.
