For a number of reasons mostly having to do with dive reports mentioning urchin barrens, I have not been an enthusiastic diver of my perceived local underwater paradises, Monterey and Carmel Bays, over the last year or so.
And that’s made me feel bad.
Then this arrived yesterday. With Dan’s permission, here is unexpurgated report by Dan Abbot, regional director of Reef Check, California, about changes seen at Point Lobos State Underwater Reserve (Carmel Bay) over the past few years of surveying there. Contact Dan for more details.
We have completed all of our monitoring surveys in Point Lobos for 2016. We completed 2 surveys at Middle Reef, one in the spring and one in the fall, and one fall survey at Weston. This is our 11th year of surveying these sites. This year we observed some big changes at these sites (especially Weston) including a dramatic decrease in the density of giant kelp. The data we collected has been uploaded to our online Global Reef Tracker and is available to be viewed and downloaded (note: 2014 Invert and Algae data does not currently appear on the Global Reef Tracker. We are working on fixing that now).
In recent years there has been a trend in some Northern California kelp forests of a dramatic increase in sea urchins followed by a dramatic decrease in kelp. Urchins are voracious grazers of kelp forests and have the ability of completely taking over lush kelp forests and turning them into “urchin barrens,” which are areas devoid of kelp, resembling a clear-cut, where primarily rocks and urchins remain.
The trend has been most pronounced outside of MPAs, evidence that these underwater parks are successfully protecting biodiversity. We witnessed a small barren develop in Monterey Bay in 2014. Last year huge swaths of the North Coast, particularly in Sonoma Country became barrens. This year we saw some barrens develop in Carmel Bay, including at Pescadero, just outside of the Carmel Bay State Marine Conservation Area.
In Point Lobos we not yet observing barrens but we did observe a dramatic increase in purple urchins at both our sites. From 2006 to 2013 we recorded densities of purple urchins at both sites to be less than two per 60 m2. In 2015 and 2016 densities of purple urchins we around 250 per 60 m2 at Middle Reef and above 450 per 60 m2 at Weston. From 2006 to 2013 densities of giant kelp averaged about 135 and 121 stipes per 60 m2 at Middle Reef and Weston respectively. In 2016 densities dropped to 44.3 stipes per 60 m2 at Middle Reef and 9.5 stipes per 60 m2 at Weston.
We recorded significant changes in the densities of other species as well. Sea stars, including bat stars, giant-spined sea stars, and sunflower stars, are all at low densities due to Sea Star Wasting Disease which broke out prior to, and maybe at least partially responsible for, the dramatic increase in urchins. In addition to purple urchins, red urchins are also present in higher than normal numbers. Other species of kelp, including Pterygophora appear to be decreasing, though not as dramatically as the very abundant giant kelp and are currently within the range of what we have observed in the past. Fish, which are very abundant in Point Lobos, do not appear to be affected so far. All of this data is available at data.reefcheck.org.
Personally, I was surprised by the condition of Weston in particular. It is a place I have dived for many years and it has always been one of the most pristine sites in the Monterey area. I was a little surprised to see it in such a state and thus wanted to inform you directly of what we saw. I’m not sure how much the park staff and volunteers are aware of what is occurring in the ocean portion of the State Park. Though I am concerned about the state of these two sites, I should also note, that unlike forests on land, kelp forests are highly dynamic ecosystems, and can quickly bounce back from a big change. As they do every spring after the winter storms tear the kelp free wash it up on the beach. On the other hand, places that become urchin barrens seem to reach another stable state and stay that way for a long time with many implications up the food chain.