Global estimate of mesopelagic mesozooplankton biomass.

The global standing stock of mesozooplankton in the mesopelagic zone was assessed using estimates of particulate organic carbon (POC) and net primary productivity (NPP). These estimates were compared to published data to establish a relationship between epipelagic and mesopelagic zooplankton biomasses. The relationship between species diversity and biomass in the mesopelagic zone was examined using scatterplots and maps with 2-dimenssional scales. The results showed that NPP and POC were important predictors of mesopelagic mesozooplankton biomass (MMB). Linear models incorporating these factors were statistically significant, explaining a moderate to high proportion of variance in the predicted MMB. The spatial patterns of MMB showed higher values in some regions of the northern hemisphere, along the west coasts of continents, and in the equatorial and 50°S bands. This study provides the first estimates of MMB using two definitions of the mesopelagic zone: standard (200-1000 m depths) and variable depth. Global MMB was estimated between 0.20 and 0.91 PgC, depending on the method. High biomass values were common in regions with intermediate rarity values and high species richness coupled with high POC stocks. Surface and mesopelagic biomass spatial patterns were consistent, and the epipelagic/mesopelagic biomass ratio depended on mesopelagic zone depth, suggesting a higher MMB than previously observed.