The Biggest Little Frond in the Sea

Talking protists in class these days, so here's the only one I have photos of:

Giant Kelp (Macrocystis pyrifera), Seward, AK  8/3/2012

For the most part, protists are small critters, typically microscopic. This, on the other hand, is Pacific Giant Kelp (Macrocystis pyrifera), washed up on the beach at Seward, Alaska. It can reach 45 meters long (that's ~150 ft!), not bad for something we call a protist. Since it grows in dense stands (often called forests), it actually affects light conditions, (1) water flow, and nutrient levels in the surrounding water, (2) making it a crucial part of an ecosystem that supports many other species, from young fish to Leopard Sharks (Triakis semifasciata) and Sea Otters (Enhydra lutra). When Kelp is removed, communities of smaller algae change, often dramatically, (3) although the extent of the changes does appear to vary with the specific composition of those communities. (4) Even after it washes up on shore, kelp supports an interesting fauna of little critters. (5) Losing this species means major changes in coastal Pacific waters, including the loss of important game and food fishes. And a study from 1998 of Orca (Orcinus orca) predation on Sea Otters suggests that overfishing of salmon, by a very interesting chain of events, has produced that very result in the Pacific Northwest. (6) Orcas that once relied on salmon have been forced to prey on sea otters, resulting in a decline in otter populations. Otters like to eat sea urchins, so we see more of them. And sea urchins (some of them, at least) feed on kelp holdfasts (the bottom part, where a bottom-dwelling sea urchin could reach). So an increase in urchins produces a decrease in kelp, all because of overfishing of salmon.

Orca (Orcinus orca), Resurrection Bay, AK, 8/4/2012

Sea Otter (Enhydra lutris), Resurrection Bay, AK 8/4/2012

Protists are sometimes called a "wastebasket" group. As I tell my students, they're all the eukaryotes that didn't get big or interesting enough to call their own kingdom. But Giant Kelp is clearly both big and interesting -- guess I'll have to amend that.

(1) Gerard, V. A. (1984). The light environment in a giant kelp forest: influence of Macrocystis pyrifera on spatial and temporal variability. Marine Biology, 84(2), 189-195.

(2) Gerard, V. A. (1982). In situ water motion and nutrient uptake by the giant kelp Macrocystis pyrifera. Marine biology, 69(1), 51-54.

(3) Foster, M. S. (1975). Regulation of algal community development in a Macrocystis pyrifera forest. Marine biology, 32(4), 331-342.

(4) Santelices, B., & Ojeda, F. P. (1984). Effects of canopy removal on the understory algal community structure of coastal forests of Macrocystis pyrifera from southern South America. Marine ecology progress series. Oldendorf, 14(2), 165-173.

(5) Inglis, G. (1989). The colonisation and degradation of stranded< i> Macrocystis pyrifera</i>(L.) C. Ag. by the macrofauna of a New Zealand sandy beach.Journal of Experimental Marine Biology and Ecology, 125(3), 203-217. 

(6) Estes, J. A., Tinker, M. T., Williams, T. M., & Doak, D. F. (1998). Killer whale predation on sea otters linking oceanic and nearshore ecosystems. Science,282(5388), 473-476.