Global patterns and drivers of seagrass biomass, net primary production and meadow structure

We decipher global patterns in seagrass growth and structure to advance
seagrass science, facilitate multidisciplinary research, and promote
effective management strategies and policy development for seagrass
habitats. A global data set on seagrass total biomass, total NPP, shoot
density, and percent cover was compiled for 11 genera. Here, we tested how
these variables change across seagrass genera, life-history strategy, and
geographic location, and then sought to decipher the environmental drivers
of the patterns observed. The mean (±SE) total biomass of seagrasses
globally was estimated at 340 ± 10 g DW m
-2, and total NPP was estimated at 5.4 ± 0.4 g DW m -2
d-1. Mean shoot density across all genera was 1,780 ± 67 shoots m-2, and
percent cover was 42 ± 1%. Persistent genera showed the highest total
biomass, followed by opportunistic and then colonising genera, whereas
shoot density was higher for colonising than for persistent, which had the
highest percent cover. Latitudinal and bioregional patterns were
identified for some genera, and were mostly driven by genus-specific
traits, followed by localised environmental factors. Trends in seagrass
meadow ecology were largely influenced by seagrass genera and their
life-history strategy, with localised environmental factors, such as
temperature and nutrients, also playing a role. Global estimates of
seagrass biomass and NPP were 2 times higher than previously reported.
Seagrass life-history strategies modulate the trade-offs between NPP and
biomass to thrive in specific habitats. This study provides the most
updated global synthesis of patterns in seagrass growth and structure.