3rin's View…

Walking on a different beach recently, just a few miles south of where I live, I became mesmerized by the Bullwhip Kelp (Nereocystis luetkeana) that had washed ashore. The smoothness and the golden-brown coloration of the floats (pneumatocysts) made them quite photogenic. I am clearly not the first person to be fascinated by the floats of this kelp since the name Nereocytstis is Greek for Mermaid’s Bladder.

As you know by now, once something catches my eye I am driven to dive into the subject and this was no exception. The rapid growth rate of Bullwhip Kelp is astounding enough: morphing from a single spore to 120′ long in one growing season (that’s over 5” a day). But the real story is the interconnection between this kelp, sea urchins, sea stars, and Sea Otters.

Back in March I shared information about the Sea Star Wasting Syndrome (SSWS) that caused a massive die-off of sea stars along our Pacific coast. First noted the summer of 2013, the disease has affected over 19 species of sea stars, severely depleting the population. Turns out we have more to mourn than the loss of sea stars, as entire ecosystems have been negatively impacted.

Ochre Sea Stars (Pisaster ochraceus), control California Mussel (Mytilus californianus) abundance on intertidal rocks which allows for a greater diversity of species on those valuable territories. A bit further offshore in the subtidal zone, Sunflower Sea Stars (Pycnopodia helianthoides) prey predominately on sea urchins. Since 2015 the sea urchin population has exploded, according to one researcher, “…densities have increased from less than one urchin per square meter to anywhere from a dozen to three dozen…”

Sea urchins voraciously devour algae, which includes kelp. Even Bullwhip Kelp (the fastest growing kelp in the world) can not withstand the onslaught of unrestrained masses of sea urchins. Urchin barrens now cover vast sections off the west coast where great kelp forests once thrived.

This is devastating since kelp forests not only minimize wave action but they provide sheltering habitat for a number of species, including Sea Otters. Sea Otters are inextricably linked to these kelp forests as they hunt and sleep amongst the stems and ribbons. The decline of Sea Otter populations is at least partially linked to SSWS.

There is a bright spot in this sad tale, sea star surveys conducted in the past few months have noted a huge increase in juveniles. There is even a high likelihood that these youngest sea stars are immune to SSWS. Hopefully, these nearshore ecosystems are on the road to recovery.

Float with Visible Gas Bubble

Matte Finish Float

Shiny Float

Semi-transparent Float

Polished Bronze Float

Pale Float

Burnished Float

Remember the brightly-colored bubble photo I shared back in January? It was right after I moved to the Oregon Coast and though I was smitten with the various hues I didn’t pause to consider their source. The iridescence reminded me of similar ones I noted a dozen years ago on the beach in Carpinteria, California. Those bubbles were the result of natural seepage of petroleum from an offshore oilfield (historically, the Chumash people gathered the oil and used it to seal their boats).

Well, fast forward six months to a talk I recently attended by Stewart T. Schultz. This guy wrote the book on the Oregon Coast, I mean that literally. In 1998 he wrote The Northwest Coast: A Natural History. An Oregon native, Stewart couldn’t find a comprehensive book that described the coastal region he loved, so he wrote one (as a grad student no less).

While explaining nutrient cycling in the near shore zone Stewart described the importance of diatoms. Diatoms may be small (considered microalgae) but they are mighty; producing roughly 20% of the world’s oxygen. Plus, they are a key nutrient source for all manner of sea life. Or as Stewart put it, “A clam is basically reconstituted diatoms.”

But what do diatoms have to do with my bubbles? Everything! The daily cycle of diatoms in the ocean is a delicate dance between buoyancy and gravity. Diatoms photosynthesize which means they need to be within range of sunlight. But diatoms are unicellular and the majority of them cannot move. Diatoms have a unique solution to this problem – mucus!

Diatoms secrete mucilage which helps them float up through the water column toward the surface. During the day, the power of crashing waves can whip up a froth of mucusy diatoms which comes ashore as a foam. Hence my bubbles.

But wait, there’s more. What is mucus known for (besides being kinda gross)? It’s sticky! And diatom mucilage is no different. Throughout the day grains of sand, stirred up by wave action, adhere to the mucilage. As sand accretes throughout the day, it weighs the diatom down and causes it to slowly sink to the bottom. Overnight, the diatom creates more mucilage so that by dawn it is ascending back up to the light for another productive burst of photosynthesis.

Amazing to think about the complex dynamics involved in the creation of those beautiful bubbles!

Bubbles of Diatoms, Lincoln City, Oregon 2018