We present results from ongoing research that is investigating diversity-stability relationships and evaluating the responsible mechanisms in the benthic organisms of temperate kelp forests in the Santa Barbara Channel. The benthic component of the kelp forest is a mosaic of macroalgal and sessile invertebrate species that compete for space and are basal species in the food web. We utilized fourteen years of field survey data on the diversity and abundance of algae and sessile invertebrates across twenty-six locations monitored by the Santa Barbara Coastal Long Term Ecology Research site (SBC LTER) to test if understory algae or sessile invertebrates exhibited a diversity-stability relationship, and if the portfolio effect and/or negative covariation were contributing factors. We found that stability of the macroalgal understory community was positively correlated with species richness while that of the sessile invertebrate community was not. Stability among sessile invertebrates was significantly correlated with negative covariation among sessile invertebrate species but this did not scale with species richness. Our results point to a stark contrast between understory macroalgae and sessile invertebrates. We are continuing to evaluate other theorized mechanisms of stability that could explain why we observe a diversity-stability relationship in understory algae but not in sessile invertebrates.