Hymeniacidon perlevis detections from settlement plates at several sites within Elkhorn Slough over time. The shaded area represents the mean cover of sponges on annual recruitment plates at each site. Blue indicates that no plates deployed at a site were colonized that year, and green represents colonization occurred that year. White represents a period of no sampling at a site, open green boxes indicate H. perlevis presence, but no cover data were recorded. Sites are ordered from upper to lower estuary, with lower slough sites beginning at VM (Vierra Mouth).