Abstract
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
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.