Beaten to the punch, part 2: Tsunami Debris

Back in early 2012 Jim Brennan and I published a short technical report through Washington Sea Grant focused on assessing likely debris accumulation scenarios for Washington State associated with "tsunami debris" from the March 2011 Tohoku tsunami.  The report was a response to some dire messages that were promulgated at the time through the media, and even by some ocean circulation experts.  There was some very real anxiety about the impacts to Washington's coast from this load of debris.

Anyway, we used some analysis of previous research and observations, coupled with some liberal hand-waving, to estimate what we considered a likely range of debris loading to Washington's beaches in the first four years after the tsunami, and we came up with an estimate of 1-14 times the background debris loading level.

So that was great, and we got some limited but very nice feedback on the report from some coastal managers on the west coast, and found that it was making its way into management decisions as far afield as B.C.  As the years passed, though, I found myself with a desire to revisit our suggested likely scenario, and compare it to what really happened.  I was involved in a few tiny efforts in the subsequent years, but largely I could never pull it off.  Thankfully, someone else did.  

Earlier this year Cathryn Murray published a paper with Nikolai Maximenko and Sherry Lippiatt examining whether there was a detectable tsunami signal in temporal patterns of marine debris on the west coast, based on monitoring data.  The short answer...there was!  And they used data collect in the Olympic Coast National Marine Sanctuary to estimate that the tsunami debris contributed to a roughly 10-fold increase in debris load to beaches in Washington State...which sits squarely within our 2012 likely estimate.  Very cool!

Fig. 1. Mean yearly debris influx of indicator items from 2003 to 2015 at sites in northern Washington State, USA. Letters denote significantly different groups using Tukeys HSD posthoc comparisons).  From Murray et al., 2018.  

The figure above shows the estimated average rates of loading of a subset of indicator debris items tracked in monitoring efforts over 10+ years at sites in the Olympic Coast National Marine Sanctuary.  This is the source of the estimate that the Tohoku tsunami led to a ~10x increase in debris load.

There is quite a bit more ground covered in this paper, some of it interesting relative to what we assessed back in 2012, and some of it just cool new territory (i.e. the documentation of seasonal spikes in debris loading, which I blogged about back in 2014 in the thick of the tsunami debris period).  Really cool to see this work, and really useful for assessing when and where debris is likely to come ashore in the future associated with any input of debris in the Pacific Ocean.
 

Beaten to the punch, again...

A clump of Eudistylia vancouveri, photographed at a location just to the west of the Elwha River delta

Every once in a while over the ten years that I've been diving at Elwha I would see something that struck me as special; an example of an interspecific relationship that I hadn't really anticipated.  

Let me start with a bit of background.  First, let me introduce you to one of my favorite invertebrates, the beautiful Eudistylia vancouveri, or Northern Feather Duster worm.  I'm into these inverts for a few reasons. First, they look like truffula trees, which is just cool.  Next, and perhaps most importantly, they are big, obvious and easy to identify underwater.  When we first started diving the Elwha I always felt a sense of relief counting Eudistylia, since I knew I was going to get it right.  More than anything, perhaps, that explains my appreciation for these worms.  

A complete E. vancouveri individual that we happened to dredge up with a sediment grab.  The scissors are full size.  The tube of this individual measured roughly 1 meter, and the worm almost 0.5 m. 

E. vancouveri is a special tubeworm, notable for how large and stout its tube is.  Diving near Elwha we would commonly observe individual tubes in excess of probably 20 cm...and that was just the bit sticking out of the substrate.  We couldn't really figure out how much additional tube there was below the substrate.  On a few occasions over the years we made futile efforts to dig an individual out of the substrate, hoping to actually measure one.  I dug some big holes underwater, and never was able to get to the end of one of these tubeworms. 

It wasn't until early this year that we collected a complete individual in a sediment grab...purely by accident.  The tube was over 1 meter in length, and the worm itself around 50 cm.  These are impressive worms.  

Looking up at the fronds of bull kelp.  Oh, and there are some fish too.

The other player in this story is bull kelp (Nereocystis leutkeana).  These are a bit better known - they are the fast-growing kelp that, under some circumstances, are able to grow all the way to the surface, where you can easily observe their buoyant bulb and fronds from a boat or kayak.  These bull kelp require (or so we told ourselves) hard substrate to attach to - ideally bedrock.  They can grow on smaller boulders and gravels, but as they grow and the cross-sectional area of their stipe and fronds increases, it becomes more and more likely that they will mobilize these coarse grains  After that, these kelps are on the move...and frequently won't survive the ordeal.

A common site near Elwha - Nereocystis attached to coarse clasts.  As the kelp grows it mobilizes the clasts and the algae no longer can stay in one spot.  This typically ends poorly.

So around Elwha it always struck me that one of the challenges for Nereocystis, and maybe even a limiting factor for its distribution, was finding available stable substrate. Every now and again, though, we would see enterprising Nereocystis taking advantage of the stability of E. vancouveri to find a place to hold in relatively fine substrates.

Nereocystis attached to and growing on Eudistylia.  This photo was shot near here.  This is a pretty energetic area - high currents and decent surge - and no bedrock.  Its likely very hard for Nereocystis to find stable substrate to hold on to in this area.  

This all came up for me after reading this article in the Hakai Institute's excellent magazine.  There is a lot to like about this - I love the story here about the serendipity of this discovery, and the convergence of an observation with a "prepared mind".  In this case Matthew Bracken was prepared enough to know how special the relationship that he was seeing really was, and to document it.   I wasn't - I thought it was cool, but wasn't prepared enough to know just how cool it was.  So, again; beaten to the punch.  Maybe there still is a chance though...is this the first documentation of this relationship with Nereocystis?  

Great fields of sand

Looking south towards the Olympics from the San Juan Channel

Man, its been too long....almost three months since my last blog post.  Too much going on.  I still have a fourth edition of the sea level rise posts I started back in August in mind, but I'm going to back-burner that in favor of a shorter and easier post.  I'm back at Friday Harbor Labs, once more teaching the Marine Sedimentary Processes research apprenticeship.

Last week our class had one day of time on the R/V Centennial that we have traditionally used to make a long one-day cruise to Elwha.  But we decided instead to stay local, partner up with other classes at Friday Harbor, and make a trip out to the sand field in the San Juan channel.  We had two over-all goals.  First, many of the students had projects focused on investigating the use of this sand field by Pacific Sand Lance...and much of our time was spent pulling sand samples from the field, and sorting the PSL out of those sand grabs.  Next, we wanted to sample around the sand field to get a sense for the grain sizes immediately adjacent to it.  How distinct was the boundary of the field?

The name of the game is plucking as much sand as possible off the bottom using the biggest grab available

Sorting through a sample of sand

Pacific Sand Lance, and coarse sand

So first off, the PSL utilization of this sand field is unbelievable.  We took a total of 10 grabs of sand from the field, with the grab bringing maybe 5 gallons of sand to the surface at a go.  The average number of fish in each of those grabs was probably about 15...and the max?  An incredible 50 fish in one grab.

Pacific San Lance emerging out of a sample of sand

Interestingly enough, while the abundance of PSL in the sand field is pretty high, the sand field has pretty low diversity of invertebrates.  Just a few were pulled up.

2 of these shellfish came up, from 10 grabs.  Juvenile Clinocardium?

One sample included this beautiful worm.  Flatworm I think?

And out of 10 grabs, one amphipod.  

Our samples away from the sand field were, perhaps unsurprisingly, pretty coarse.  The currents in the channel are intense, which presumably makes this area unsuitable for the deposition of most fine sediment.  But it begs the question...how is the sand field itself maintained?  How does it persist?  These samples outside of the sand field were also notable for their relatively high invertebrate diversity.

A characteristically coarse grab sample from the San Juan Channel, outside of the sand field

We pulled up a good number of these beautiful brachiopods...its been a good long while since I've seen one of these.  I think maybe Hemithiris?  There is a lot of interest in these, not least because they are so prevalent in the fossil record.  

High chiton abundance, but we dredged up only tiny specimens like this one

A couple of these came up...juvenile Cancer oregonensis I think?

A great wealth of Podedesmus at these sites...shown here with a nice encrusting bryozoan

The only scallop we pulled up, and I'm not totally sure, but maybe a rock scallop (Hinnites) just prior to cementing itself in place (?), with maybe a boring sponge (Cliona??)