A mass mortality of sea urchins in 1983, which had drastic consequences for the reef ecosystem in part because of the prior reduction in fish stocks. In the absence of both fish and sea urchins, there were few herbivores left in the system to keep algal densities low. It is possible that stresses caused by human activity currently exceed the rates of global reef growth. The good news is that with increased attention, Jamaican reefs are improving and coral cover is again increasing. Another area of vulnerability is the exposed temperate rocky shores, which are unique and diverse ecosystems covered in mussels, barnacles, starfish, plants, and a host of creatures that live in the harsh intertidal realm.
Disturbances are regular and seasonal.
Storms remove mussels and create small patches of bare space that are quickly colonized by barnacles, seaweeds, and other creatures which have evolved to take advantage of this regular disturbance. The result is a spatial mosaic of diverse species on the shoreline. Eventually the competitively dominant mussels reoccupy that space and the cycle begins again. However, human recreational use has begun to interfere with the natural disturbance and diversity patterns of shore life. The study was initiated in response to staff at an Oregon marine park who were concerned about the impacts of high visitor use on marine diversity.