Oceanography | Vol.29, No.2
helianthoides, sea star wasting disease is altering rocky seashore
communities on an unprecedented scale.
In many subtidal habitats in Northern California, pur-
ple urchin populations have increased in abundance by nearly
an order of magnitude. Combined with warmer ocean tem-
peratures unfavorable to kelp growth, sea urchin grazing has
reduced many of the West Coast’s lush and diverse kelp forests
to barren grounds of grazer-resistant coralline algae. Devoid of
the kelp providing protection and nutrition, these urchin bar-
ren grounds can no longer sustain the high diversity and pro-
ductivity of invertebrate and fish species characteristic of kelp
forest communities.
Was the disappearance of Pycnopodia responsible for the
coincident population explosion of purple urchins? The contri-
butions of Bob and his students and colleagues have provided
us with the theoretical framework and experimental methods
required to tease out the ecological basis for the observed eco-
system regime shift. If the release of urchins from sea star preda-
tion has played a significant role in triggering this regime shift,
then it is unlikely the kelp forests will recover to their former
state, even with the return of cooler La Niña conditions, with-
out some sort of natural perturbation or human intervention to
reduce urchin abundance. I can picture the smile on Bob’s face
as his academic offspring contemplate how to make the world of
kelp forests green again.
Charles H. Greene, Associate Editor, Oceanography
REFERENCES
Cavole, L.M., A.M. Demko, R.E. Diner, A. Giddings, I. Koester, C.M.L.S. Pagniello,
M.-L. Paulsen, A. Ramirez-Valdez, S.M. Schwenck, N.K. Yen, and others. 2016.
Biological impacts of the 2013–2015 warm-water anomaly in the Northeast
Pacific: Winners, losers, and the future. Oceanography 29(2):273–285,
http://dx.doi.org/10.5670/oceanog.2016.32.
Hairston, N.G., F.E. Smith, and L.B. Slobodkin. 1960. Community structure, popula-
tion control, and competition. The American Naturalist 94(879):421–425.
Paine, R.T. 1966. Food web complexity and species diversity. The American
Naturalist 100(910):65–75.
Pfister, C.A., R.T. Paine, and J.T. Wooten. 2016. The iconic keystone predator
has a pathogen. Frontiers in Ecology and the Environment 14(5):285–286,
http://dx.doi.org/10.1002/fee.1292.
FIGURE 1. The Robert T. Paine
academic family tree at the
time of his retirement, drawn by
Marian Kohn in 1999.