Zonation: the obvious and not so obvious

Heading out at O-dark hundred, the Marine Bio 250 class made it all the way past the dreaded  ‘McCatchins’ without losing anybody arriving at  Cattle Pass ready to learn about zonation in the San Juans.  Turns out Cattle Pass is an ideal place to study this.  The south ends of San Juan and Lopez islands are ecotones, areas of sharp environmental boundaries that occur naturally.  Our destination is an area where the effects of the open ocean move east up the Strait of Juan de Fuca and meet the more protected waters of the San Juan Islands.

We dropped down to the rocky beach passing through a couple zones on the protected side of the ecotone.  The highest intertidal, the spray zone is dominated by lichens.  Caloplaca forms the orangish-yellow layer which is just above the dark layer of Verrucaria, a lichen that forms a black band.  Unfortunately it was too dark to see this band but if you look when you travel the San Juans at a more reasonable hour, it’s obvious.  Although we may have not seen it, we did get to experience Cyanobacteria, the blue-green algae that reminded us of the saying “the nearer your destination, the more you keep slip-sliding away.”

Below this zone we got into the barnacles (Balanus nebulis) and rockweed (Fucus gardneri and Fucus spiralis).   And after rolling over a few rocks we found Balanus’s nemisis, Nucella lamelosa.  nucella lamelosa on balanus

While I have done the slip and slide on rockweed for years, I had never taken the time to see the various life stages as we did in class.    fucusThis was also where the not so obvious zonation was apparent.  One rock would be covered in Fucus, the next in Balanus, and another might be completely devoid of life.  Our author states that “Explaining such departures from zonation is a major issue.  Indeed, one can question whether a predictable zonation is the typical situation on many rocky shore localities.”

As we moved south around the end of the island, species began to change.  Perhaps the most obvious change was the appearance of huge mussels, Mytilus californianus, in large patches.  Mussels do not form a continuous band here so again the question is why here and not there.Mytilis Plus these were huge mussels that we estimated to be 25 -30 years old for the largest.  In this same area, actually on this same rock, were snails that appeared to be of the third species which is not so common near FHL, Nucella carniculatus.nucella carniculatus

The other species appearing on this exposed shore was Phyllospadix, sea grass.  phylospadixAlso a patchy species it liked the tide pools as well as some areas where the waves sloshed up rock channels (the bath tub effect.)   This is a flowering plant and some were lucky enough to see its flowering parts.  Sharing the bath tub was the feather boa kelp, Egregria menziesii,  which was as long as Emily is tall.

Finally, returning to the upper intertidal was another patchy species that appeals to me both as an avid bird watcher and also as someone who has been know to consume a beer or two,  Prasiola meridionalis.  prasiolaWe saw this on the exposed side, although it also occurs on the protected side. What makes this an interesting alga is that it occurs in areas of high nitrogen concentration that are consistently damp.  This means it will occur higher on the exposed side due to wave action and a higher splash zone.  But what does this have to do with birds and brews?  NITROGEN.  This genus loves bird guano to grow in.  But not just our native northwest species, but also other members of the genus.  A paper out of Ireland by Rindi et.al.  mapped both terrestrial and marine species in the genus Prasiola.  Apparently all love nitrogen and the mapping of locations in Galway is rumored to include several pubs as Prasiola hot spots.  The GPS coordinates were given for all the study sites so I suppose with Google Earth one could verify this.

Ode to Prasiola

Prasiola is the name of this algae genus
It grows on rocks and brew pubs among us
Nitrogen is the key,
Be it guano or be it pee,
Birds and drunks make this algae famous.

Birds, brews and algae, who could ask for anything more.

And one final question: whose fingers are those holding Deadman’s fingers?  Could it be the McCatchins!
deadmans fingers

Phil Green



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