Little boxes all the same

In the lower intertidal zone, there's a new treasure to be found under every rock. This one holds a community of bryozoans, sponges, and pink spiral tubeworms.

Orange encrusting bryozoan, Schizoporella unicornis

These bryozoan colonies grow outward from the center. The inner ones die off, leaving the calcified framework behind, hexagonal boxes towards the center, switching to rectangles farther out. Along the edges, live zooids are orange; the boxy structure is less obvious, but looking closely, tiny dots show where the feeding lophophores emerge.

The orange encrusting bryozoan is an invader from Japan, and has found our waters much to its liking. My encyclopedia says it is,

"now the dominant encrusting bryozoan in much of the Pacific Northwest. ... Long term effects? An unfolding mystery."

An example of bryozoan "boxes". This one was from a bryozoan I found on kelp, examined under a microscope I had in 2012.

View of S. unicornis remains, showing the openings for the lophophores. Photo: Yale Peabody Museum. YPM IZ 049667 

Zooming in on the rock face, I found what looks like a new colony, circular and dotted with feeding zooids.

The blobs on the lower centre left show the same basic structure, but they're piled on top of each other. The little grey doughnut is the egg ring of an unknown snail.

And on to the next rock ...

(Title taken from a line of the song, "Little Boxes". The photo on Wikipedia is reminiscent of bryozoan crusts.)