Interest in oceanography and marine biology and its relevance to global environmental issues continues to increase, creating a demand for authoritative reviews that summarize recent research. Oceanography and Marine Biology: An Annual Review has catered to this demand since its foundation, by the late Harold Barnes, more than 40 years ago. It is an

Red abalone and sea urchins are both important herbivores that potentially compete with each other for resources like food and space along the California coast. Red abalone supported a socioeconomically important recreational fishery during this study (which was closed in 2018) and red sea urchins support an important commercial fishery. Both red sea urchins and red abalone feed on the same macroalgae (including Pterygophora californica, Laminaria setchellii, Stephanocystis osmundacea, Costaria costata, Alaria marginata, Nereocystis leutkeana), and a low abundance of this food source during the period of this project may have created a highly competitive environment for urchins and abalone. Evidence that suggests competition between red abalone and red sea urchins can be seen within data collected during the years of this study (2014-2016): a significantly higher red sea urchin density, concomitant with a significantly lower red abalone density, was observed within areas closed to commercial sea urchin harvest (in MPAs) compared to nearby reference areas open to sea urchin harvest. In addition, a significant negative relationship was found between red abalone and red sea urchin abundances when examined at the 60 m2 transect level: transects with higher abundances of red sea urchins contained fewer red abalone. Designating MPAs that are closed to sea urchin harvest, in the absence of sea urchin predators such as sunflower stars (Pycnopodia helianthoides), sea otters (Enhydra lutris), spiny lobster (Panulirus interruptus), and predatory fish species, (such as the sheephead (Semicossyphus pulcher) found in Southern California), may all have contributed to an increase in red sea urchin abundances and a concomitant decrease in red abalone within the Cabrillo MPA studied in this project.