gribble-grousing

Seattle’s Proposition 1, issuing a thirty-year, $290 million bond to repair the city’s crumbling seawall, appears likely to pass. The proposition will require a property tax increase of about sixty dollars per year from land owners in the area, and the project’s first phase—injecting a special grout behind the seawall from S. Washington Street to Virginia Street, as bulwark—is slated to begin next summer. Phase two continues the grouting from Virginia to Broad Street and will reportedly cost another $300 million. It promises to be a costly, drawn-out affair, with street closures and traffic snarls galore. Opponents of the proposition don’t disagree that the seawall needs work—a truth self-evident—but quibble mostly over the source of its funding. Regardless of who pays, it’s clear that drastic measures are far past due. All of this, however, is my roundabout way of saying that the state-sanctioned war on gribbles has begun.

What is a gribble, you say? Gribbles are fourteen-legged wood-boring crustaceans of the Limnoriidae family, and they are the culprit behind our seawall’s decline. Exceedingly small creatures—more than twenty could cram onto a penny—gribbles are abundant in all oceans and provide a scant-recognized service to the housekeeping of the sea: breaking down wood. Like blanched underwater termites, gribbles have been gnawing wood since time immemorial, munching on the rafts of arboreal flotsam because little else salubriously can. They have plagued seafarers for centuries: Columbus once delayed a return trip to Europe because his ships were too gribbled to sail. When the Titanic wreckage was first discovered in 1985, explorers noticed that all the exposed wood on deck had been gobbled by gribbles.

Though it’s difficult to descry nowadays, a large portion of the steel-and-concrete Seattle waterfront is supported by a sixty-foot wooden platform, erected in 1934. Piled above the platform is thirteen feet of dirt, and above this dirt lie shops, warehouses, museums, train tracks, streets, and the upraised interstate. On February 28, 2001, the 6.8-magnitude Nisqually earthquake shook Seattle for almost a minute, causing the Alaskan Way Viaduct to mysteriously sink several inches. A subsequent investigation beneath the seawall revealed a vastly deteriorated platform, which in some sections was completely devoid of wood. Engineers in 1934 thought the steel, concrete and dirt matrix would keep the timbers safe from seawater and gribble-nibbling, but this, alas, was not the case. Salt corroded through the steel, allowing seawater to wash away much of the soil and giving the gribbles unfettered access to the planks.

What is it about wood that grabs the gribble? After all, it’s really quite tough to see the gustatory appeal of soggy sawdust, however salted it may be. Trees are made mostly of cellulose and lignin, chemical compounds that constitute the bulk of a plant’s, well, bulk. These compounds are incredibly durable in living plants, and it takes a lot of work to break them down. (Try chewing through a tree.) Harder still is the process of extracting nutrients from wood, a digestive feat few animals can manage without help from gut-dwelling bacteria. It is a niche lifestyle, this xylophagy, and those who can hack it find themselves almost without competition. Gribbles too have their microscopic compatriots to aid with digestion, but their relationship is a bit more nuanced.

On land, under the right conditions, fungi and other minute organisms use enzymes to slowly digest wood, breaking down lignin and cellulose and degrading its physical structure in the process. The wood splits apart, exposing more surface area, permitting more microorganisms to join the smorgas-board. Without their metabolic magic, forests everywhere would be stacked high with dead trees and leaves decomposing at a literally glacial rate. Those trees washed out to sea by rivers, though, are no longer subject to this fungal decay, and they become the domain of the gribble. Using its specialized front legs, the gribble burrows just beneath the wood’s surface, boring ventilation holes to the water every couple millimeters. It plods along, chewing thoughtlessly. Despite all outward appearances, the crustacean doesn’t ingest the wood for food; rather, it eats the microbes attracted to the masticated pulp, they being quite happy having an excavator to forge the way. Thus the gribble grinds through wood, striating its surface with crisscrossing burrows, revisiting old tunnels to chow on the new microbial growth. As the gribbles graze, widening channels with each pass, the wood weakens and eventually gives way, utterly fenestrated by hordes of pale, flea-sized sawyers.

The war on gribbles is upon us. Understand thy enemy, and know this: gribbles are implacable creatures, deaf to sense and reason (and probably everything else). They don’t care that their depredations may end up costing us $600 million in seawall renovations, or that we’d gladly give them other bits of wood to chew on, somewhere else, or that they’ve undermined the waterfront to the point of it almost falling into the sound. They just…don’t…care.

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