Introduction

The thin region where the sea meets the land is unlike either land or sea. It is betwixt and between, a threshold from one state to another. It is a linear point or a coastal ribbon, a place of dramatic change and remarkable abundance—abundance of life and also of possibility. The regions where continents meet the great oceans of our planet are long stretches of liminal space.

From the continent’s point of view the approach to an ocean is usually through dunes or over a cliff to a sandy beach, a rocky coast, or a cobbled shore. The littoral region extends from the terrestrial land to the edge of the water at the lowest tides, where it gets swallowed by the marine world. From the ocean’s perspective, the approach to the world’s great landmasses is from the deep and dark pelagic up over a continental shelf into a dim region where light barely penetrates the waters and on up into a brighter photic zone, what might be called the subtidal, and continues into the low intertidal where the extreme full-moon tides pull away the water once or twice a month, up towards the beach or rocky reef where the ocean swells in and out in six-hour cycles, up finally to the highest tide mark, the wrack line, where the ocean leaves its debris to mark a final encroachment towards dry land.

This sliver of ocean, where sunlight penetrates enough to allow photosynthesis to work its magic and where the benthos, or ocean bottom, provides something to hold onto, is the home of the seaweeds, or marine algae. Seaweeds have three requirements for survival: a substrate to hold onto to keep them in one place, sunlight to provide the energy for primary production of biomass, and nutrients to fuel growth. The thin section of ocean from the intertidal zone to about three hundred feet (91 metres) deep is where the ocean flora find these three elements for success and where they reside. This is a miniscule sliver of ocean area, less than two percent of the entire sea floor, and yet it is a zone of incomparable richness, where marine algae are the supreme eco-engineers. They oxygenate the waters, create three-dimensional habitat for countless other organisms, and form the base of a food chain that keeps our planet—unique in the universe as we know it—opulently rich in life.

The Pacific Ocean’s edge where it encounters the North American continent is considered one of the richest of these rich zones. The continental shelf is abrupt and close to the coastline, often less than a mile from shore. The steep transition from deep to shallow and prevailing winds that push surface waters away, letting the cold deeper waters well up with their vast nutrient stores, allow for exuberant algal growth. This slice of ocean from Alaska to Baja California in Mexico has some of the most diverse and abundant seaweeds and kelps on Earth. The rocky, fog-shrouded coast sports a spectacular number of seaweed species, from enormous kelps to tiny corallines.