Growing in our oceans and lining our beaches, seaweed is familiar to us all. But what many of us don’t realise is the nutritional benefit that seaweed offers.
The edible seaweed industry in Australia is in its infancy. It’s only recently that scientific research is being conducted into the nutritional benefits of seaweed and how we can start incorporating it into our diets.
Southern Australia has more species of seaweed than any other region, with 62% of species not growing anywhere else in the world. This means that we’re starting from scratch when it comes to understanding the health benefits and nutritional values that it holds.
It also means that we have a huge potential for discovering more species of commercial value. On a global scale, Australia is perceived as having clean and pure waters, making Australian seaweed products highly desirable to the rest of the world.
Seaweed accumulates nutrients, trace elements and minerals from the water in which it lives. Some of these, such as zinc and iodine, are important additions to our diet and are often lacking in terrestrial grown food. By eating seaweed, we are increasing our vitamin and mineral consumption (see the Seaweed Solution article on Page 23). The more diverse types of seaweed we eat, the wider the range of nutritional benefits we experience.
Unlike mushrooms, seaweeds have few if any naturally occurring toxins. Any seaweed is potentially edible; it’s just a matter of how they taste as to whether you want to eat them.
The problem is that the same processes that enable seaweed to concentrate beneficial dietary nutrients also enable them to accumulate metals, pesticides, herbicides and other contaminants of emerging concern (CECs) from the water they grow in, making the consumption of seaweed potentially toxic.
Dr Alecia Bellgrove and her team at Deakin University are currently testing Australian seaweeds grown in clean and unpolluted waters, along with those grown in highly urbanised (and potentially polluted) waters to see what levels of different pollutants, beneficial fatty acids and minerals occur. They are yet to finalise the results, so when harvesting seaweed, it’s important to think very carefully about where you’re getting it from.
Your safest bet is to buy dried seaweed from reputable companies that harvest it sustainably and test it for toxins. However, if you’re mindful, collecting your own can be a rewarding experience that allows you to become more in touch with the ocean and where your food comes from.
Where To Collect
Before going out foraging for seaweed, you need to be aware of the laws that surround its collection in your area. Go to your local Department of Fisheries website to find out your state’s regulations. Some states allow only beach cast seaweed to be collected, whereas others allow a small amount above the low tide mark — but never in marine parks.
Also until we have data to suggest otherwise, it’s best to avoid collecting seaweed from highly urbanised areas or close to river mouths, sewage outlet drains and other wastewater outlets.
Environmental Impacts Of Harvesting
It’s not just danger to our own health we need to think about when foraging seaweed, but also the effect it can have on aquatic life. Seaweeds are often foundation species in many coastal marine ecosystems; the engineers that the rest of the ecosystem rely on. They provide food and habitat for many other species living within it, and often alter the physical environment, such as by reducing light, wave action and desiccation at low tide. The canopy of some varieties provides protection for a whole range of species of animals. With Neptune’s necklace (Hormosira banksii), if canopy is reduced by just 25% it can dramatically impact the animals that reside within.
If just one branch (frond) is taken from each plant and that is spread across the shoreline, that’s a more sustainable way to forage. It is important to know and understand the varieties that you are harvesting, as some types of seaweed will happily grow back if cut whereas others will not, killing off the plant and harming the ecosystem.
The following is a guide to a few of the more commonly available seaweeds and how to harvest them with minimal impact:
Where is it found: In the rocky intertidal zone from Albany in Western Australia through to northern NSW, and around Tasmania and New Zealand. Can also be found in estuaries throughout the range, often free-floating amongst mangroves.
Ecology: Important habitat for lots of species, providing shade and moisture at low tide. Reducing canopy by as little as 25% can impact the associated biodiversity.
When is it best to harvest: Can be found all year round but is more prolific in the colder months. Best/safest places to harvest: Rock pools away from river mouths, urban areas and wastewater outlets. Avoid collection from estuaries or mangroves.
How to harvest: Remove only one or two fronds from each plant from the base, but ensure the holdfast disc is left behind to regenerate. It is sensitive to trampling so try and not burst the bubbles while walking over the reef.
How to prepare: Pickle with salt, vinegar, seawater, a bit of pepper, ginger and any other pickling herbs and spices of your choice. Can also be used as a base for steamed fish.
Where is it found: Broadly distributed subtidally throughout southern and eastern temperate Australia, as well as in the Canary Islands, the Cape Verde Islands, Madagascar, Mauritania, Senegal, South Africa, Oman, Lord Howe Island and New Zealand.
Ecology: Important habitat provider. When is it best to harvest: This species is a perennial, so it can be harvested all year round. Best/safest places to harvest: Avoid obvious pollution discharge points and highly urbanised shores. This kelp is more resistant than many others and can be found in close proximity to pollution sources.
How to harvest: The meristem is at the base of the central lamina so harvesting should occur above that point to allow regeneration. Best to trim only a few blades from each plant to minimise impact and canopy reduction.
How to prepare: Pickle as you would for any vegetable or blanch and dehydrate for later use. You could also try making oven-baked chips from this species and crayweed (see below); baste first in soy and other seasonings and spices. Can be used to wrap around fish for steaming or baking to enhance flavour.
Where is it found: Subtidally on open coasts from Robe in South Australia, throughout Victoria and Tasmania, to Port Macquarie.
Ecology: Important habitat provider for crayfish and many other plants and animals. Vulnerable to wastewater discharge. Populations were decimated from the Central NSW coast through historical sewage discharge. Current efforts are underway to restore populations (Operation Crayweed).
When is it best to harvest: This species is a perennial but often lacks condition during summer months when waters are warmer. If plants look healthy they should be fine to harvest. Best/safest places to harvest: This species is generally absent on highly polluted shores, but avoid obvious signs of urbanisation and/or effluent discharge. Collections should be avoided on the Central NSW coast due to current restoration efforts.
How to harvest: Apical meristems means regeneration happens from the tips to extend and basal meristems create new fronds. Could harvest an individual frond or more ideally blades from various fronds on a plant. Blades are more likely to be the best bits to eat. If a whole frond is harvested, then the midrib could be used for soup stock, dried, ground and added to feeds, but it might be a bit tough to eat straight up.
How to prepare: Blanch to remove surface bacteria then boil to soften, oven bake, pickle or dehydrate for later use. Can be rehydrated as a soup stock and flavour enhancer. Can be used to wrap around fish for steaming or baking to enhance flavour as well.
Where is it found: Between the low and high tide line, growing on rock shelves and in rock pools.
Ecology: Grows rapidly in response to nutrients and disturbance. Rapid regeneration from propagules (like seaweed seeds). Important food species for animals.
When is it best to harvest: Generally abundant and nutrient-rich over late winter through to spring. Under normal nutrient conditions it dies off over summer.
Best/safest places to harvest: Avoid collecting from areas near river mouths, wastewater discharge and drain outlets to avoid potential contamination. Also avoid highly urbanised shores.
How to harvest: Plants can be trimmed anywhere and should regrow. Make sure to leave the holdfast (the bit attaching it to the rock) and some of the tissue, as removal of the whole plant will rely on a new individual to take the place. When harvesting, try to spread the collections across the shore.
How to prepare: This is one of the few types of seaweed that can be eaten fresh. Wash and add it to a salad, crush and blend with salt, or dry and add as a garnish over your favourite dish. For lovers of Japanese okonomiyaki pancakes, this is the dried seaweed sprinkled on top.
Realistically for many of us, harvesting in clear and unpolluted waters where regulations allow it may make harvesting a bit difficult. However, there are a growing number of businesses selling dehydrated seaweed and edible seaweed products which you can order online and add to your diet.
Dr Alecia Bellgrove is a marine biologist at Deakin University. She is currently driving a research program exploring the potential for a creating a sustainable seaweed industry in southeastern Australia.