Seaweeds of the Pacific Northwest

(Unedited version)
Originally appeared in the October 2008 issue of
Tropical Fish Hobbyist Magazine

This spring I was fortunate enough to take a three week vacation in my home state of Washington. I spent most of my time exploring various natural habitats and taking photos. The western side of Washington borders the Pacific ocean giving me lots of opportunities to explore the coast and it's many diverse areas.

Though we usually look at different aspects of the freshwater environment, I thought it might be fun to look at the photosynthetic plant like organisms that live on the Washington coast, and what better issue to publish it in than the annual MACNA edition?

Gearing Up

In between my trip adventures I purchased several field guides, two that covered local seashore life. Field guides and books about nature often offer useful information that can be used or adapted for your aquarium. They can also offer a greater understanding of the plant and animal life we keep, and natural habitats in general. Different areas have a their own unique populations of wildlife and plants, and local shops will often have area specific field guides that make at least somewhat closely identifying what you see much easier.

Weather and Wind:
An Essential Pair

The Pacific northwest experiences seasonal weather changes and part of those changes include the direction that the winds blow. In the spring and summer the winds blow south, this moves the surface water away from the shore which in turn pulls cold, nutrient rich water from the depths to replace it. This is called upwelling. The infusion of nutrient rich waters in the spring and summer coupled with the increased sunlight supplies the plants and algae with the tools they need to thrive. This allowed the diverse number of macroalgaes that developed there. These in turn supplied the food base that the rest of the system could survive on.


Most seaweeds are various types of macroalgae. Though they can look like plants, macroalgae are less complex than plants. Macroalgae don't have roots, but have simple anchoring structures called holdfasts. Macroalgae also don't have the complex vascular systems that true plants do, as there is no need for them to store and transport water, since they live in it. Like other algae, macroalgae don't produce seeds but reproduce with spores.

Photosynthetic organisms use pigments to trap the energy of the sun and store it. Chlorophyll are the most well known pigments that plants and algae use and what gives them their green color. Plants and algae also use other pigments and some seaweeds have predominant colors other than green.

Phylum Chlorophyta green algae

The green algae are what we most commonly see in freshwater planted aquariums, and the least represented in the marine environment. Some green algae are terrestrial, and some form symbiotic relationships with fungus to create lichen. Green algae can also be unicellular or colonial. The green algae, like the plants we're more familiar with, get their color from chlorophyll pigments. They use chlorophyll a and b and are similar to land plants, and are considered by most scientist to be the group that terrestrial plants evolved from. Green algae are most often found in shallow waters because chlorophyll functions more poorly as the light changes in deeper water.

On my visit to the Washington coast the green algae I remember seeing the most were sea lettuce, a species of Ulva, which not surprisingly looks similar to lettuce. Perhaps I remember this one the most because it was on a lot of the rocks I was walking over and was very slippery. It looked very wilted when the tide was down but seemed to perk right back up when it was under the water again.

Another interesting green macroalgae common to the area is Codium fragile, it's also called, among other names; dead man's fingers, sea staghorn or sponge weed. This is an attractive multi-branching algae that looks similar to some sponges. This macroalgae can have a small red algae that grows on it called staghorn fringe.

Phylum Phaeophyta brown algae

Brown algae are multicellular and mostly marine and they include the very impressive kelp. Kelp form dense underwater forests to a depth of about 200 feet. These forests support large communities of aquatic life. Kelp are the largest algae and they only ones to have internal conducting tissue, though it's not as advanced as that found in true plants. Like green algae, brown algae have chlorophyll pigments, using chlorophyll a and c, but their color is covered by the pigment fucoxanthin, giving them a brown color.

Kelp were very plentiful along the beaches and rocky tidal pool areas in the far northern part of Washington. As well as species that grew closer to shore there were many that had been torn up from the deeper kelp forests. The feather boa kelp were particularly interesting with their irregular branching and oblong floats. These kelp grow to the length of about 33 feet, others are much longer.

Smaller brown macroalgae that were abundant included 2 types called rockweed. Both had flat branching blades, but one also had bladders and is sometimes called bladder wrack or popping wrack.

Phylum Rhodophyta - red algae

The largest group of the marine algae the red algae has more species than the green and brown combined. Most of the red algae are multicellular. They include some of the most strikingly colored of the macroalgae in red, pink, violet and purple. Like other algae and plants these seaweeds have chlorophyll but also have red and blue pigments giving them their unusual colors. These pigments also allow the macroalgae to use the lower light levels available in deeper water.

Some of the most interesting colored seaweeds I saw are the iridescent. This macroalgae is a dark red to purple color with iridescent blue and violet highlights in the sun. It looks very similar to oil or gas on water.

There are other beautiful red algae with branching shapes that look like red ferns. There are several genus and species that have a similar appearance. There were several piles of these laying on the beaches and they were very attractive.

Some red algae fix calcium carbonate to form hard exterior that can branched or encrusting. These are the include the sought after coralline algae that many reef keepers strive to encourage in their aquariums. These also grew on the rocks along the coast. Usually many types of macroalgae would be close together.

True plants

There are also a few true plants, not macroalgae, that live in the ocean. On my visit I also saw quite a few patches of seagrasses or Surf Grass. These plants resemble the Vallisneria and some Sagittaria we grow in our fresh water planted aquariums.

Bringing it Home

Most macroalgae live in cold water, and certainly those in Northern Washington. There's a good chance they wouldn't be suitable for the home aquarium, though some of the pools they live in can get rather warm. It may also be illegal to collect some species or any species in some places. I didn't intend to attempt to bring any seaweed home from my trip. So I didn't look in to the possibility of collecting any. As far as I've seen it looks like it's always illegal to collect in national parks. While researching this column I noticed that since many seaweeds are eaten and used commercially that, in Washington at least, some seaweeds are legal to collect with a fishing license. I'm not sure if you're allowed to keep them in an aquarium though so I would recommend you fully check local laws before attempting to bring anything you find on the beach home.

Weather Factor

Most of the seaweeds I saw were along the coast outside the Olympic National Park in May of this year. There are many different areas of beach along the Washington coast, and I visited areas from the north of Oregon to the tip northern tip of Washington covering at least sections of most of the area.

There had been some severe storms and damage the previous winter. In many areas the forest comes down to the ocean and many huge trees were pulled up during the storms, making for very interesting landscapes. Some areas had long areas of relatively clean clear sand with a back drop of driftwood along the edge. Many areas were marshy with some brackish water.

There were also a surprising number of shore plants that were along the edge or in and out of the water, growing in the sand. I can't image sand and salt water would be the preferred environment of most plants but there were a surprisingly large and diverse number that made this landscape their home.

Exploring and tides

Though you may not have access to the Washington coast there are many coastal areas and each one is unique in its own way. Exploring natural areas close to you can bring you further insight and ideas for your home aquariums.

If you decide to explore a beach are be sure to check on local laws and conditions. There is a surprisingly large difference in depth between high and low tides and time can slip by easily while your out exploring the sea shore or tide pools. Sometimes what seems like a safe path can become an island with no dry way back to shore.


After looking at some of the macroalgae and other plants and animals that live in the marine environments you may decide to attempt a planted marine aquarium of your own. You wouldn't be alone. Many people are exploring the possibilities of creating marine planted gardens, and different macroalgaes suitable to the home aquarium are becoming more widely available in pet stores and through mail order resources. For an interesting twist on the hobby it might be something you'd be interested in exploring.

Welcome to the Jungle | Into The Forest | The Creepy Crawlies | A Clearing in the Thicket | Algae Eaters for the Planted Aquarium
North American Natives | Why things go wrong Pt 1 | Why things go wrong Pt 2 (Algae) | Algae Eating Shrimp | Lo-Tech Tanks
Welcome to the Fish Room | The Stemmed Plants | Mosses | A Livebearer Biotope | Planted Tank Social | The Genus Hygrophila | Cyanobacteria
Easy Plants | What I Did Last Summer | Decorations in the Planted Tank | Botany-An Introduction to Plant Biology | Botany-Anatomy of a plant
Botany-How Plants Work | Easy Rosettes | Going High-Tech | Floating Plants | Dealing with Success | Bringing the Outside In | Vallisneria
Hair Algae | Flowering Aquarium Plants Part 1 | Flowering Aquarium Plants Part 2 | Liverworts in the Aquarium | Elements of Design
Planted Aquarium Maintenance | More Mosses | Invaders | Ferns in the Aquarium | Setting up a Planted Aquarium
Seaweeds of the Pacific Northwest | Proserpinaca | Hardware for the Planted Aquarium | Rotala | Neocaridina Shrimp | Lo-tech Tank Tips

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