Lowest Tide and the Diffusion of Life

Went to the waterfront in downtown Seattle in late spring for the lowest tide of the year,

-3 feet. Took my lunch break from my job at Cisco in Belltown and walked through the sculpture park and down to the water front. There were some volunteers with pamphlets with several interesting species already scoped out, but the beach was actually pretty dead until the last couple of feet.

According to the volunteer, the shoreline in that area of Myrtle Edwards park had been torn out when they repaired the sea-wall and replaced less than a year previously. From perhaps 0' up to 2' the rocks were slimy with simpler sea weeds. Below 0' a few interesting things were visible - barnacles, snails, limpets, several kinds of sea weed. It was slippery and rough, scrambling over the last 6 or 8 feet of sea weed coated rocks to get down where the water was splashing. Fingerlings swam by, a few gulls were visible. The shore is an isolated pocket, to the south the piers cover the shore, and to the north bulkheads drop steeply into the water up towards the grain elevator in West Seattle. There isn't an adjacent inter-tidal zone, so it's been slow to re-populate. I’m glad they took the time to rebuild a little inter-tidal zone back up, even if it may take a decade or more to really regenerate.

Rapidly changing conditions – reminds me of the recent story about the fish in Lake Washington. As the human population grew and the waters of the lake got more cloudy, this one species of little fish dropped most of their armoring of scales over a couple of decades. Apparently since the predator fish couldn’t hunt them visually they were less likely to be bitten, so the armor provided less benefit and the balanced tipped to favor fish that mature more quickly and avoid the extra metabolic cost of the extra scales. Then in the 70s Seattle and King County put in sewers and storm water retention ponds and the water cleared back up. Within a couple of decades the armor was back, and the fish now look about like they did before: moderately armored. With our rivers and lakes, swamps and marshes, erosion and flooding, we get large swings in visibility all the time. I speculate that there is a sort of meta-evolution occurring – these fish have evolved an ability to evolve additional or fewer scales quickly in response to competitive pressure. Their ability to evolve is evolving – meta-evolution.