Estimating biomass from images for marine macrofauna

Biomass data are essential information for quantitatively describing ecosystems. Current methods of determining biomass by measuring dry mass are time-consuming and destructive. To overcome these drawbacks, a database of area-mass data pairs was established, allowing dry mass to be estimated from recorded surface areas, initially starting with six species. Surface areas were derived from photographs using ImageJ software, and ash-free dry mass (AFDM) was subsequently determined using a Precisa Prepash oven. The imaging setup and analysis using ImageJ have been further developed. The correlation between surface area and mass is formulated as M = α*Aβ, where mass M is calculated from surface area A, parameterized by the normalization constant α and the scaling constant β. For Mytilus edulis and Monocorophium acharusicum, β is around 1.5, consistent with an isometric growth pattern. Jassa herdmani, Sabellaria spinulosa, Phtisica marina and Metridium senile have a β value around 1.3, indicating some shape change during growth (allometry). Based on the collected area-mass data pairs, species-specific models could be constructed that predict AFDM with good reliability (R2 values of 0.77–0.96). Additional filters on the month of collection, depth below sea level, preservation method, preservation period, location, and substrate are collected to refine the model for specific circumstances. For Mytilus edulis, the season (month of collection) appears to be an important factor in calculating AFDM. On the other hand, data for Mytilus edulis at different salinities are important for calculating DM, but not for AFDM.