Mearns Rock 2008

What You See

In 2008, there is very little popweed (Fucus) on the rock. Almost all of the large reproductive plants seen in 2007 are now gone, except for a few stragglers on the lower left corner of the boulder. The absence of the popweed now allows us to see that the rock surface has about a 50% cover of white barnacles and some black areas. In a close-up view, we see that there are two size classes of barnacles: older, large ones and many tiny new ones. In addition, the black spots and regions are juvenile mussels. Last year, we saw baby mussels under the Fucus. This year, they are exposed and appear to be growing.

It is interesting that, despite the loss of popweed on the rock, there is still a heavy cover of it and other seaweeds on the beach face. We also see the continued presence of eelgrass in the water behind the rock.

What’s Happening?

The thick cover of reproducing Fucus seen in 2007 has either died out or possibly has been removed by grazing animals or even ice scouring in the winter of 2007/2008. Since we don't visit the site in the winter, we don't know if ice was present. However, the changes are reminiscent of what happened between 1991 and 1992 or between 2000 and 2001.  The presence of very tiny white barnacles suggests that they recruited onto the rock very recently and perhaps after the Fucus disappeared.  Likewise, it appears that the baby mussels that settled under the Fucus in 2007 are now growing.  Will their future be like what happened between 1992 and  1993, when Fucus disappeared and there were a lot of mussels that continued to grow into 1994 and then disappeared? Maybe predators, such as seastars and predatory snails, will come onto the rock and eat the new mussels before they have a chance to grow! It's tough to predict what's going to happen next. We will have to go out again in 2009 and find out!

Stay tuned!

(07.01.08, Snug Harbor, Knight Island, Alaska)