1 - 5,000 individuals/m^3
||Tréguer PJ, De La Rocha CL. The world ocean silica cycle. Ann Rev Mar Sci. 2013 5 :477-501. doi: 10.1146/annurev-marine-121211-172346 p.483 3rd paragraphPubMed ID22809182
||Boltovskoy D, Kling SA, Takahashi K, Bjorklund K. 2010. World atlas of distribution of recent polycystina (Radiolaria). Palaeontolog. Electron. 13: 13.3.18A
||P.483 3rd paragraph: "Radiolarians inhabit all major oceans, and in the upper 1,000m of the ocean are typically found at densities between 1 and 5,000 individuals/m^3 (primary source). Not all radiolarians produce a silica skeleton, and the lack of information about silica per radiolarian and rates of DSi [dissolved silicon] uptake make it currently impossible to estimate the contribution of radiolarians to silica production. However, if 0.6 μg is a representative weight for a radiolarian skeleton (Takahashi 1981), anywhere from 1 μmol to 6 mmol of the 2–26 mmol/m^2 of biogenic silica standing stocks in the upper 120 m of the ocean (Adjou et al. 2011) could be associated with radiolarians."