Data from: Studying biodiversity-ecosystem function relationships in experimental microcosms among islands

Ecological studies on islands have provided fundamental insights into the
mechanisms underlying biodiversity of larger organisms, but we know little
about the factors affecting island microbial biodiversity and ecosystem
function. We conducted a field experiment on five Baltic Sea islands where
we placed aquatic microcosms with different levels of salinity mimicking
environmental stress and allowed diatoms to colonize the microcosms via
air. Using structural equation models (SEM), we investigated the
interconnections among environmental and dispersal-related factors, diatom
biodiversity, and ecosystem productivity (represented by chlorophyll a
concentration). We also tested whether the body size structure of the
community influences productivity together with biodiversity. In SEMs, we
found no relationship between species richness or evenness and
productivity. Rather, productivity increased with increasing mean body
size of species in the communities. The effects of environmental stress on
both biodiversity and ecosystem productivity were highlighted as species
richness and evenness declined, whereas productivity increased at the
highest salinity levels. In addition to salinity, wind exposure affected
both biodiversity metrics and productivity. This study provides new
insights into microbial community assembly in a field experimental setting
and the relationship between biodiversity and ecosystem function. Our
results indicate that salinity presents a strong abiotic filter, leading
to communities that may be species-poor, yet comprise salinity-tolerant
and relatively productive species at high salinity. Our findings also
emphasize the importance of mean community body size in mediating the
effects of environmental conditions on productivity and suggest that this
trait should be considered more broadly in biodiversity-ecosystem function
studies.