DeLong, J. M., Hodges, D. M., Prange, R. K., Forney, C. F., Fan, L., Bishop, M. C., Elliot, M. L., Jordan, M. A. and Doucette, C. 2013. The influence of cold water storage on fatty acids, antioxidant content and activity, and microbial load in ostrich fern (Matteuccia struthiopteris) fiddleheads. Can. J. Plant Sci. 93: 683-697. The influence of upwards to 42 d of cold water storage (CWS) on selected bioactive compounds and microbial populations in ostrich fern (Matteuccia struthiopteris) fiddlehead tissue was investigated. Following harvest, the fiddleheads were stored in cold deionized water (1°C) with removals occurring at 1, 8, 18, 28 and 42 d. Post-removal analysis showed fiddlehead tissue had a unique fatty acid composition including γ-linolenic, dihomo-γ-linolenic, arachidonic and eicosapentaenoic acids. Post-storage tissue concentrations of ascorbic acid, a- and γ-tocopherol, a- and ß-carotene, the xanthophyll pigments (violaxanthin, zeaxanthin and lutein) and phenolic compounds ranged from high to very high for green plant tissue. High antioxidant activity values were also recorded and were likely due to the elevated phenolic compound content. Site differences were also apparent for several of these measurements. The microbial data showed that the fiddleheads had relatively high populations of bacteria as well as yeast and fungi resident on the tissue and in the surrounding storage water. Significant linear and quadratic CWS effects (both positive and negative) occurred for many of the bioactive compound and microbial measurements. A CWS period of a month or perhaps longer at 1°C appears possible for ostrich fern fiddleheads before the nutritional content markedly declines.