Andrea Schwenke Wyile
Seaweed
Hungry for some tasty algae? You might be surprised to know that marine algae is another name for seaweed. Seaweeds are vital resources in the ocean, providing shelter, nutrients and breeding grounds to a wealth of ocean plants and animals. These plants* are also found in everyday products from toothpaste to soap to fertilizer to…you guessed it, snack food!
Spend time at the seashore in Nova Scotia and you will soon see bands of dried seaweed washed up and dozens or more species of living seaweed in the tide pools and shallow water just offshore. In fact, Nova Scotia has over 350 species of seaweed! Seaweeds range in size from microscopic algae, barely visible to the naked eye, to bull kelp that grow up to 100 metres long! The most common species here in Nova Scotia are Irish moss (Chondrus crispus), rockweed (Ascophyllum nodosum), and bladderwrack (Fucus vesiculosus). Another common Nova Scotian seaweed, dulse (Pulmaria palmata), can be found in most grocery stores, and is harvested right here in the province. Take a look the next time you walk along a beach in Nova Scotia, and you will likely see each of these species, and more.
Seaweeds provide some widely used ingredients in commercial products, such as carrageenan, agar, and alginate. They provide nutrition in our diets as a food additive and thickening agent. Seaweeds are rich in minerals and used in many supplements, as well as in traditional medicine. They were one of the first sources of added iodine to the human diet and were used as a nutritional supplement for over two centuries. They are still used in natural health supplements today, though their effectiveness needs further study. As some have anticoagulant properties and cause allergic reactions in some people, among other contraindications, they should not be consumed without consulting a medical professional. Seaweeds are also used in many beauty and skincare products. Seaweeds provide a powerful additive to fertilizers and are used in livestock feed.
Seaweed can store up to 35 times more carbon than rainforests, making it an important area of research for climate and environmental scientists. They are also major area of current study for biofuels.
* Algae are plant-like organisms, the ancestors of plants.We refer here to algae as plants for simplicity.
Harvesting Seaweeds
Walking on seaweed on the beach will not hurt it or damage the local population, but commercial seaweed harvesters must follow strict guidelines to avoid overharvesting and to preserve this special local resource. Some Nova Scotian companies harvest seaweed only by hand using specially designed rakes that prevent harvesters from damaging the holdfast. This ensures that plants can be harvested year after year.
Let’s take a closer look at two species of seaweed, bladderwrack and rockweed.
BLADDERWRACK (Fucus vesiculosus), black tang, rock wrack, red fucus, rockweed
Appearance
The scientific name for this brown alga is Fucus vesiculosus, from the Greek word for seaweed, phykos, and vesiculosus, meaning vesicle. Each frond of this seaweed typically has two air bladders, or vesicles, which give it buoyancy in the water. This helps the algae float on the water surface, giving it more sunlight and therefore more access to the energy it needs to photosynthesize. This easy-to-spot characteristic explains its common name, bladderwrack, though it has many other nicknames, including black tang, rock wrack, red focus, and others. Bladderwrack does not develop air bladders until maturity, so young specimens may not have their paired bladders yet, and even at maturity some branches may only exhibit single bladders. Bladderwrack fronds typically grow up to a metre long, splitting off into multiple branches, and are attached to rocks or other non-mobile objects, such as wharfs or sunken debris. Bladderwrack attaches itself to these objects using a “holdfast,” a root-like structure used by many aquatic plants to anchor themselves underwater.
Ecology
Bladderwrack grows predominantly in cold, shallow water, in the mid-tidal zone. It is not usually found at high tide lines, where it would not readily receive the nutrients it needs to thrive. Unlike some thicker growing seaweeds, bladderwrack does not usually grow densely enough to provide shelter over large areas, but does provide protection for a number of common, but very small, ocean critters, such as isopods, some snail species, and other small marine invertebrates. It is common throughout Nova Scotia and is often the dominant species in areas affected by ice scour during the winter months, as it is robust and can survive harsher conditions than some other native seaweed species.
Bladderwrack has a lifespan of about five years, and, similar to grass, the top of each blade can be cut and it will still continue to grow, so long as the lower part of the plant is not damaged.
Range
Bladderwrack grows naturally in the North Atlantic Ocean, from Atlantic Canada to Northern European shores and as far south as Morocco.
ROCKWEED (Ascophyllum nodosum), knotted wrack
Appearance
The scientific name for this brown alga is Ascophyllum nodosum, but you are likely to hear it called by its common name, rockweed, or knotted wrack. It earns its nickname from its propensity for growing on underwater rocks, where it may become exposed during low tides, as the air bubbles on each frond, or bladders, give it buoyancy. Similar to bladderwrack, the air bladders help the fronds float on the water surface, giving it more sunlight and therefore energy for photosynthesis. Rockweed fronds can be up to two metres long, branching out into multiple strands. Similar to bladderwrack, it affixes itself to rocks or other non-mobile objects using a holdfast.
Ecology
Rockweed’s long length and densely branching fronds enable it to cover large swathes of intertidal areas and provide food, shelter, and breeding grounds for many other shallow ocean organisms. This vital role in the ecological community shows the importance of protecting rockweed populations in Nova Scotia.
With a lifespan of ten to fifteen years, rockweed brings much-needed stability to marine areas, and threats to the population need to be carefully monitored. The introduction of non-native green crabs (Carcinus maenas) into Nova Scotia and surrounding coastal areas in recent years has significantly affected rockweed communities, as the crabs voraciously consume the seaweed until entire areas are left barren and unsheltered. Without the seaweed to provide safe areas for other organisms to mate and reproduce, fish and invertebrate diversity has declined sharply. This is an ongoing area of study and ocean experts are working hard to reduce green crab populations and prevent future invasive species in Nova Scotia, as well as other affected coastal waters.
Range
Rockweed grows naturally in the North Atlantic Ocean, from Atlantic Canada to the Arctic Circle to Northern Europe.
Rockweed or Bladderwrack?
Think you’ve found some good rockweed or bladderwrack at the beach? Not too fast! They look very similar. Adding to the confusion, both are casually referred to as rockweed, both are used in supplements and cosmetics, and both are common in Nova Scotia! Rockweed (Ascophyllum nodosum) is usually dominant however, in areas not covered in winter ice.
The easiest way to distinguish these two seaweeds (as long as the specimen is at least one year old) is by checking for a midrib that runs vertically along each frond. If there is a midrib, it is bladderwrack. If not, you are likely looking at rockweed. Also, bladderwrack’s bladders are mostly paired whereas rockweed’s bladders are usually not paired.
Seaweed Biomimicry
Biofouling is a problem in aquatic environments as organisms grow on wharfs, ship hulls, and on other organisms, deteriorating structural integrity, decreasing efficiency of ships, and creating challenges to the fishing industry. It also plays a significant role in introducing invasive species to new areas, as organisms can be transported on ships and in ballast water across long distances and are left to reproduce wherever the ships travel. This can create ecological problems as the newly introduced species outcompetes native species, decreasing or even eliminating local populations.
Many researchers are trying to combat this concern with studies on a variety of antifouling techniques. As many seaweeds and other marine organisms engage in “shedding”, where the outer layer of cells gets sloughed off, researchers are trying to discover ways to mimic this shedding ability on the hulls of ships. This would be a significant step, not only for researchers and engineers, but also for the shipping industry and the environment.
Jokes
What did the ocean say to the seaweed?
Nothing. It just waved!
Where does seaweed look for a new job?
In the kelp wanted ads!
Sarah Silver Slayter
