Age and life style affect macroalgae colonization by amphipods in shallow marine environments

Dispersal and colonization processes are complex and affected by several factors in the marine realm. Understanding how and where individuals go can be challenging, particularly for marine invertebrates that do not have a sessile phase. We selected the amphipod-macroalga system to investigate if life stage and life style can influence colonization patterns from algal patches placed at different distances and having variable amounts of available substrate for colonization. Amphipods are key organisms connecting the benthonic and pelagic environments through food chains and our results bring important contributions for conservation and management of these systems in shallow marine areas. We ran field and laboratory experiments to compare the colonization of Sargassum fronds between adult and juvenile amphipods, as well as tube-dwelling and free-living species. We found three times more juveniles than adults colonizing the experimental patches, and both tube-dwelling and free-living juveniles occupied experimental patches across all distances in the field. In the laboratory, we observed the tube-dwelling Cymadusa filosa remaining in more proximal patches than the free-living Hyale niger. Juveniles occupied similarly small and large algal surface area patches both in the field and in the laboratory, while adults occupied primarily large algal surface area patches in the field. We did not observe differences regarding life style in the colonization of small or large algal surface area patches by juveniles in the field or in the laboratory. Our findings support the idea that juvenile amphipods may have higher dispersal potential by colonizing more distant areas and/or patches with variable amounts of available substrate when compared to adults. Amphipods life style may influence colonization distance during initial dispersal movements of juveniles due to the fact that tube-dweller juveniles stay closer to the site where they were released.