Algae and Seagrass in the Sanctuary

Marine algae (aka seaweed), while often referred to as “marine plants”, are not true plants and instead belong to the Kingdom Protista. Like true plants, they photosynthesize using chlorophyll, the pigment that appears green; but they also contain other pigments that appear in shades of red and brown, which is why alga species are categorized into green, brown, and red algae. Unlike true plants, algae does not have stems, leaves, or flowers. The only true marine plants are species of seagrass, which belong to the Plant Kingdom.

There are over 200 species of algae and two species of seagrass that can be found in Greater Farallones National Marine Sanctuary. Below are some of the most common or noteworthy species . Learn how our LiMPETS Program monitors many of these species in the Sanctuary.

Learn more about Sanctuary wildlife.

Brown Algae (Kelp)

Bull Kelp Nereocystis luetkeana

Bull kelp forest in California has been drastically declining in recent years. Greater Farallones Association and Greater Farallones National Marine Sanctuary are working to recover this important species. Learn more.

Habitat: Intertidal, subtidal

Range: Central California to Alaska

Avg. Size: Can grow up to 118 ft in length

Fun Fact: Bull kelp pneumatocysts (the gas-filled bulbs that keep the kelp raised toward the sunlight) have up to 10 percent carbon monoxide in them as a byproduct of photosynthesis.

Photo: Keith Johnson

Giant Kelp (Macrocystis pyrifera)

Giant kelps makes up impressive, underwater forests that can be found in the Sanctuary. Kelp forests provide food and shelter for thousands of marine species, and are important not only to the regional ecology, but to recreational and commercial interests as well. While giant kelp growth can fluctuate naturally with seasonal changes to ocean conditions, the species has been in steady decline in California in recent years.

Habitat: Kelp forest, rocky seafloor

Range: Temperate water along the North American coast from central California to Baja California, Mexico; along the temperate coasts of South America, New Zealand, Australia

Avg. Size: ~10-100 ft

Fun Fact: Giant kelp can release over 50 trillion spores every year and can grow at a rate of 2 ft per day!

Photo: Chad King, NOAA

Feather Boa Kelp (Egregia menziesii)

Habitat: Subtidal, mid intertidal, rocky shore, kelp forest

Range: Mexico to Alaska

Avg. Size: Can grow to over 30 ft in length

Fun Fact: This kelp resembles a feathery scarf, hence the common name: feather boa kelp.

Photo: James St. John, Flickr Creative Commons

Winged Kelp (Pterygophora californica)

Habitat: Rocky intertidal, kelp forest

Range: British Columbia, Canada to Baja California, Mexico

Avg. Size: up to ~9 ft in length

Fun Fact: Winged kelp is a long-lived perennial marine plant that can survive for up to 25 years!

Photo: Steve Lonhart, NOAA MBNMS

Green Algae

Sea Lettuces Ulva spp.

Sea lettuces are green, thin species of algae that often appear crumpled and translucent. It can commonly be found throughout the intertidal of Greater Farallones National Marine Sanctuary and along the California coast.

Habitat: Intertidal, shallow subtidal

Range: Global, along the West Coast of North America from Alaska to Mexico

Avg. Size: grows up to 16 inches

Fun Fact: Sea lettuces are only two cells thick so they often appear transparent.

Photo: Myfanwy Rowlands

Dead Man’s Fingers (Codium fragile)

Habitat: Mid to low intertidal

Range: Alaska to Baja, California, Mexico

Avg. Size: up to ~1 ft in length

Photo: Steve Lonhart, NOAA MBNMS

Red Algae

Nori (Porphyra perforata)

Habitat: Intertidal

Range: Aleutian Islands to Baja California, Bering Sea, Sea of Okhotsk, and Russia

Avg. Size: up tp ~1 ft

Photo: Flickr Creative Commons

Iridescent Algae (Mazzaella flaccida)

Habitat: Mid to low intertidal, upper subtidal

Range: Alaska to Baja California, Mexico

Avg. Size: up to ~3 ft length, ~10 in width

Photo: Chad King, NOAA MBNMS

Crustose Coralline Algae (Odonthalia floccosa)

Habitat: Rocky intertidal, shallow subtidal

Range: Alaska to Chile

Avg. Size: ~1/4 inch thick encrusted on rocks

Fun Fact: It used to be thought that encrusting coralline algaes were animals related to coral.

Photo: Wikipedia Commons


Eelgrass (Zostera marina)

Eelgrass (Zostera marina) is the primary type of seagrass found along the Sanctuary coast, including in Tomales Bay. Eelgrass beds provide an important habitat for numerous fish (including commercially-important Pacific herring, rockfish, and salmon) invertebrates, and seabirds as food, shelter, and important spawning and nursing grounds; as well as other ecosystem services including increasing water quality by trapping sediments and reducing excess nutrients and pollutants in the water column, preventing coastal erosion by buffering the impacts of wave energy and storms, and sequestering carbon. Learn how the Sanctuary works to protect this important seagrass habitat, and how you can help.

Habitat: Low intertidal, bay (sandy shore), estuary, protected sandy beaches

Range: Alaska to Baja California

Avg. Size: Blades are up to 1 cm wide and up to 3 m long

Fun Fact: Eelgrass improves water quality by filtering pollution that has runoff into the water. It also absorbs excess nutrients, stores greenhouse gases like carbon dioxide, and protects the shoreline from erosion.

Photo: Wikipedia Commons