Chapter 1: About Seaweeds


“We live on a planet dominated by oceans. As we develop our limited land masses, often converting arable lands into commercial and residential areas and otherwise reducing our ability to support an increasing human population, we will grow more dependent upon ocean resources.”


This opening from the original Pacific Seaweeds is as true now as the day it was written. So too is the statement that we must understand the ocean and its inhabitants in order to wisely develop and sustain our ocean resources. This includes seaweeds: major players in coastal ecosystems, a continental fringe swaying gently in near-shore waters around the world. Seaweeds constitute the nutritional base for many shallow-water food webs and, as the architects of coastal marine meadows and underwater forests, provide homes and shelter for entire communities of associated fishes and invertebrates.

In addition to playing important ecological roles, seaweeds benefit humankind in numerous ways—with great potential for more. They are used for food, industrial and scientific chemicals, plant fertilizers and pesticides, and livestock feed supplements; are a renewable energy source; and can provide services in nature that would be impossibly expensive to reproduce. The potential pharmaceutical uses of seaweeds is still an exciting horizon, as it was in the original Pacific Seaweeds, with exploratory tests indicating seaweed constituents may combat hypertension (high blood pressure), some cancers and stroke. Perhaps the newest frontier is the potential for seaweeds to extract carbon dioxide from seawater, thereby reducing the effects of ocean acidification on shellfish. Because seaweeds are so diverse, and so distinct from flowering plants and fungi, we can expect to continue discovering new, exotic compounds and new uses beneficial to humankind.

The seaweeds dealt with in this guide are major elements of the temperate marine flora extending from southeast Alaska (60°N, just north of Homer) to central California (34°N, just south of Santa Barbara at Point Conception; Figure 1). Biogeographers refer to this stretch of coast as the Cold Temperate Region—this region is the focus of this book. The coastline west of southeast Alaska is the Arctic Region, and south of Point Conception is the Warm Temperate Region. General seawater temperatures define each region; for the Cold Temperate Region these are 5–14°C (41–57°F) in winter and 10–18°C (50–64°F) in summer. Along the approximately 55,000 km (34,000 mi) of foreshore in the Cold Temperate Region live more than 640 species of seaweeds. We have not attempted to describe all species on our shores; instead, you will find here a curated selection of 240 species representing common seaweeds spanning the full range of lifestyles and forms in this part of the Pacific Ocean.



Figure 1. This guide covers the Cold Temperate biogeographic region of the Pacific coast from Homer, AK, to Point Conception, CA.

Related objects



What Are Seaweeds?

Seaweed Morphology and Growth

Seaweeds and the Tree of Life

Seaweed Life Histories

Seaweed Names

Biodiversity, the DNA Barcode and the Future of Taxonomy

Beach Etiquette, Collections, Safety


Next: Chapter 2: Identifying Pacific Seaweeds

Back to Acknowledgements