Data from: Invertebrate community composition in a New England fouling community

Fouling communities are tractable ecological systems that form on manmade
structures added to the marine environment. Their proximity to the water’s
surface allows hypotheses about community assembly, disturbance, and
invasion biology to be tested and these communities have become model
systems in the marine realm. Much of this work has focused on sessile
invertebrates but, on hard substrates in the marine environment,
invertebrates and macroalgae, organisms from two different kingdoms, can
compete for the same limiting resource, space. On rocky reefs, macroalgae
and invertebrates are partitioned between horizontal and vertical walls
respectively, but invertebrates are able to persist on horizontal surfaces
if algae are excluded by shading, suggesting that algae presence may
exclude invertebrates or impact invertebrate post-settlement mortality. I
conducted four manipulative experiments on floating docks to test if algae
also excluded invertebrates in fouling communities, including potential
mechanisms for this by using mimicked (putative plastic) and modified
(distal thalli removed) algae. In three out for four experiments,
macroalgae did not exclude invertebrates but did alter invertebrate
community composition, communities with algae tending to have more native
species whereas communities without algae were dominated by invasive ones.
In one experiment, macroalgae also appeared to facilitate invertebrate
settlement in the early stages of community assembly, mediated by both
algae structure and natural chemical cues. If macroalgae can confer
invasion resistance i.e., its presence in a community can shift
assemblages towards those composed of more native versus invasive species,
then managing floating docks to enhance algae persistence can help prevent
species invasions. Recommendations include constructing docks out of
materials that allow sufficient light for photosynthesis, orienting docks
towards the sun, and adding surfaces and structures that can enhance algae
growth and persistence. Marinas should also be managed to reduce sediment
and pollutants, factors that negatively impact algae survival.
Furthermore, to advance the field of invasion biology, more studies should
investigate facilitation, indirect effects, and interactions between
organisms from different taxonomic groups.