Biological correlates of sea urchin recruitment in kelp forest and urchin barren habitats

Shifts between the alternate stable states of sea urchin barren grounds and kelp forests correspond to density. In Aleutian Archipelago, green urchins Strongylocentrotus polyacanthus are dominant herbivores that graze forests. Sea recruitment is an important driver influences density, particularly in absence top-down control from a keystone predator such as otter Enhydra lutris . To understand how biological community may influence patterns recruitment, we compared recruit (size ≤20 mm) densities with biomass other benthic organisms both ground forest habitats at 9 islands across Archipelago. Patterns structure 2 did not explain recruits; however, same 10 specific taxa were found correlate recruits each habitat. Taxa showed strong positive correlations included Codium, Constantinea, Schizymenia, hydrozoans, while negative observed Pachyarthron Pugettia Weak Alcyonidium ascidiaceans habitats, weak variable relationships detected Polysiphonia Corallina habitats. The species-specific be due small displacement by larger conspecifics, larval responses settlement cues, post-settlement survival via biogenic refugia, or potentially predation. These potential interactions apparent, regardless habitat, it can inferred they would preserved presence