Metatranscriptomics reveals higher species compositional homogeneity in
smaller size coral reef zooplankton
Marine drifting animals — zooplankton — play essential ecological
roles in the pelagic ecosystem, transferring energy and elements to
higher trophic levels, such as fishes, cetaceans, and others.
Zooplankton are generally considered passive drifting organisms
homogeneously distributed throughout waters, where high dispersal is
expected. Although empirical observations have demonstrated that many
species possess active swimming mechanisms that generate metacommunities
with high beta diversity, the role of animal sizes in the process of
marine zooplankton community dynamics remains unexplored. Here, we
collected a total of 48 size-fractionated zooplankton samples in the
vicinity of a coral reef island with environmental gradients and
performed metatranscriptome analyses. The samples were collected in two
transects (from nearshore to offshore) twice a day (morning and night).
Sample size fraction was the only variable that rendered apparent
differences in species composition between the samples. Our results
demonstrate differential dispersal through the size fractions —
smaller size fraction communities had higher compositional homogeneity
than larger ones. Contrary to expectation, distance to shore had no
significant influence on the composition or diversity of zooplankton
communities. This study offers novel insights on the use of
metatranscriptomics for analyzing community structures and the role size
plays for the marine zooplankton community assembly processes.