A semi‐automated digital microphotographic approach to measure meiofaunal biomass

Meiofauna studies often investigate community structure and function where biomass estimates and taxonomic analysis are required. Nondestructive methods of biomass estimation are necessary to preserve specimens for subsequent taxonomic analysis. A semi‐automated protocol to estimate meiofaunal biomass was developed to meet this need. The method improves upon previous indirect biomass techniques by using digital microphotography and analytical graphics software to obtain better estimates of biovolume. The technique is not fully automated because the digital images require some manipulation. Dry mass and carbon mass were estimated for two dominant components of marine benthic meiofauna (Nematoda and Harpacticoida) as the product of conversion factors and body volumes. The technique was validated by comparing indirect dry and carbon mass estimates to direct measurements using an analytical balance and carbon‐hydrogen‐nitrogen (CHN) elemental analyzer. No significant difference was found between the semi‐automated method and direct measurements for harpacticoid dry or carbon mass (P = 0.68 and P = 0.74, respectively), or nematode dry mass (P = 0.28) or carbon content (P = 0.17). The semi‐automated indirect method was used to estimate the biomass of meiofauna (13,279 harpacticoids and 12,288 nematodes) collected from the deep‐sea Gulf of Mexico. Estimated average wet mass was compared to direct analytical balance measurements from an earlier, independent study in the same area. Wet mass estimates generated by the indirect method (2.67 ± 0.86 µg/harpacticoid and 0.85 ± 4.78 µg/nematode) were similar to direct measurements in the earlier study (2.80 µg/harpacticoid and 0.85 µg/nematode). The semi‐automated indirect method is about three times faster than traditional microscope methods to measure body volume, estimates biomass comparably to direct methods, and conserves samples and images of samples for other analyses.