Sunday, December 22, 2013

Ask an Expert: Seaweed Harvesting in BC


I've heard that wrack seaweed is being harvested in BC. Is this something we should be worried about?  Submitted by Elizabeth K.

Answer (by Tom Carefoot)

Yes, most definitely we should be worried. But, first, let's define what 'wrack' is. You may have heard the expression 'going to wrack and ruin', where 'wrack' in old times referred to the wreck of a ship on the shore, then later referred to cast up seaweed (see photo 1).  Nowadays, of course, the expression refers to falling into a state of destruction and decay.  When the word is applied to seaweed it is sometimes just a quaint way to refer to all stranded seaweeds, but may also be used to refer to certain species of brown kelps such as the Atlantic coast brown alga Ascophyllum nodosum.

Photo by Ian Birtwell.

So why do the harvesters want to harvest wrack seaweed? The harvested seaweeds can be processed for their content of commercially useful substances, including alginates, agar, and carrageenans, depending upon the type of seaweed.  In a seaweed, the carbohydrates mentioned are involved in structural support, while in commerce they are used as various thickening or gelling agents in face creams and other cosmetics, toothpaste, ice cream, and pharmaceuticals. For many biologists, including me, the term 'wrack' assumes a certain amount of drying, up to and including even the most crinkly sun-dried seaweed that one finds higher up on the shore. Less water, of course, means less expense for the harvesters to gather, load and transport the wrack for processing. One important wrack harvesting species in BC, Mazaella japonica, is a red algae with a particularly high content of carrageenan.   It is also a non-native species with an aggressive, over-growing presence.

Photo by Ian Birtwell.

The most recent harvesting of wrack in British Columbia that I know of, and that has created a fair bit of controversy, occurred in 2012/2013 in the Deep Bay/Browser area around Parksville, and is ongoing.  The BC Ministry of Agriculture granted 5 licenses, each for 1000 tonnes of Mazaella japonica wrack to be removed from 21km of shoreline in 2012, and two more licenses in 2013 each for 300 tonnes.  It seems that only 300 tonnes in total were harvested in 2012, with the data not yet in for 2013.  The harvesters are allowed to use vehicles on the beach to cart and load the seaweed (see photo 3), but there appears to be little or no on-site monitoring of number and size of these vehicles.  In face of growing opposition from local citizens, environmental groups, First Nations peoples, and scientists (ref. cited below), the granting of smaller-scale licenses suggests that the Ministry of Agriculture may be tentatively applying the brakes, at least for now. 

Photo by Pamela Smythe & The Comox Valley Echo.

 Photo by Ian Birtwell.

So, what’s the issue?  Does harvesting of wrack have important ecological consequences?  The answer is “yes”, for several reasons. The main concern relates to possible negative effects on inshore fisheries. There are several species of fishes, such as Pacific sand-lance, herring, and surf smelt, that use these same beaches on which to spawn.  Of serious concern in this regard is the physical damage done to the shore by harvesting machinery and raking. 

Sandy beaches are not desolate wastelands that can tolerate being disrupted in this way.  Sand lances, for example, preferentially spawn in intertidal sand/gravel areas, sometimes quite high on the shore.  In the absence of physical protection and shading provided by wrack, the eggs are more vulnerable to drying and being eaten by bird and fish predators.  Additionally, in the above-tide or strand area itself (where wrack eventually ends up), there exist many species of worms, amphipods, isopods, beetles, and so on.  These live in and among the seaweeds, and in burrows in the sand beneath them, and many of them, but most notably the amphipods (beach-hoppers), feed directly on the seaweeds (see photos 4 and 5).  These crustaceans feed and breed, and often become so numerous that that the sand and seaweeds can hardly be seen for their bodies. Whole kelp plants can be consumed in just a few days.  As the seaweeds diminish in volume and/or move about in high wave-swash these arthropods are found and eaten by fishes and birds.  Fine particles and pieces of seaweed find their way back into the intertidal and subtidal regions where they are consumed by a host of suspension- and deposit-feeding crustaceans, worms, and sea urchins, and by numerous omnivorous and herbivorous invertebrates.  Wrack, therefore, is a living entity on the beach, and plays a vital role as a steady, predictable, and necessary conduit of energy and nutrients from the ocean to the land and back again.

Photo by Maryjo Adams.

Photo by Ingrid Taylar.

For several species of semiterrestrial arthropods, wrack in its dried form is actually preferred as food over fresh seaweeds.  In the summer of 1998 at the Bamfield Marine Science Centre, a group of 6 international scientists, including myself, hosted by NSERC Canada and the participating scientists’ home countries of England and Germany, investigated the biology of the sea-slater isopod Ligia pallasii (see photo 6) and two amphipod species Megalorchestia californiana and Orchestia traskiana.  Among other things, we discovered that these consumers actually prefer the wrack form of stranded seaweeds, probably owing to the fact that, in their dried state, wrack provides about 50% more energy and nutrients “per mouthful” than would be available from a diet of fresh seaweeds.

  Photo by Tom Carefoot.

To some, wrack is just old rotting seaweed from which to derive profit.  In reality, wrack is a valuable component of the sea/land interface, essential for the livelihoods of many invertebrates that require it as food, and of many species of fishes and birds that eat these invertebrates and/or use the wrack to help them survive and lay their eggs.  Best to leave it be. 

Learn more about amphipod use of wrack seaweeds as food. Visit a Snail's Odyssey.  


Birtwell, I. K., R. C. de Graaf, D. E. Hay, and G. R. Peterson. 2013.  Seaweed harvesting on the east coast of Vancouver Island, BC:  a biological review. Unpublished report. 28 pp.   

Thanks to Mike Hawkes, Department of Botany, University of British Columbia for seaweed identifications.

Tom Carefoot, Marine Biologist

Department of Zoology

University of British Columbia

Tom Carefoot is Professor Emeritus with the University of British Columbia Department of Zoology and a marine ecology expert. He is a frequent contributor to E-Fauna BC and provides introductory notes for marine invertebrates. E-Fauna BC is cross-linked to his marine invertebrates web site, A Snails Odyssey.

Tuesday, December 17, 2013

Featured Plant Species: English Holly


In the southwestern corner of BC, English holly (Ilex aquifolium)--a common Christmas decoration--has moved into the woods and is now present in most of our urban or near-urban 'woods' as a result of dispersal by birds.  A walk through local parks can often turn up seedlings, saplings and trees.  It is a hardy species that is tolerant of moist conditions and, where it invades, becomes part of the site ecology. 

English holly is a broad-leaf evergreen species that is native to western and southern Europe, northwest Africa, and southwest Asia, including the UK (exclusive of northern Scotland) (Wikipedia 2013, Kew 2013).  Kew reports it as one of the 'few native evergreen trees in Britain'.  In BC, English holly is grown on holly farms on Vancouver Island and is commonly found in gardens.

Visit our atlas page on English Holly.
Read more about English holly here (Kew Royal Botanical Gardens).

Monday, December 2, 2013

Guest Contributors: Observations on European Mistletoe (Gui): by Jim Dickson and Genevieve (Jenny) Lecrivain

A little bit of European seasonal flavour by two E-Flora contributors...

The French name for Mistletoe is Gui; the g is hard, the pronunciation being like the Scots gie, meaning give. One of the first things to strike a Scottish botanist in Franche-Comté [the former 'free county' of Burgundy, France] is the abundance of Gui (Viscum album), a plant rarely noticed in Scotland where it is not native. There is a plant low down on the trunk of a Common Lime in Glasgow University campus. There is a bigger population in the middle of Edinburgh where some spread has taken place. Sparse other records have been made in Scotland. So that does not amount to much but here in Haute-Saône this parasite simply cannot be missed. All I have to do is walk down past the fruit trees to the end of Jenny’s back garden and there it is on an old Plum tree. However, it is particularly noticeable on the many plantations of Poplars (Peupliers, the often planted Populus x euamericana, a hybrid of Populus nigra). These trees can be infested, as can Willows and Apple trees. The crown of an old Apple can appear more Mistletoe than Apple.

The hosts as seen by us so far in Haute-Saône are:

Apple (Malus domestica), Birch (Betula pendula), Black Loqust  (Robinia pseudacacia), Hawthorn (Crataegus monogyna), Hazel (Corylus avellana), Plum (Prunus domestica), Blackthorn (Prunus spinosa), Poplar (Populus spp), Small-leaved Lime (Tilia cordata), Willows (Salix spp).

Though short, this list makes the point that Gui grows on many different trees, as on Scots Pines in Tyrol but not in Scotland. In recent scientific papers no less than 27 different host trees have been found in central Warsaw and 59 species, cultivars and hybrids of trees are claimed as hosts in Croatia and Slovenia.

Though here in Haute-Saône Poplars in general are very susceptible, it seems the commonly planted Lombardy Poplar (Populus nigra cv. italica) is resistant.. In Warsaw the Polish botanists noted 612 trees of Populus x euamericana but only one Lombardy Poplar with Gui.

It is easy to find Lombardy Poplar totally lacking Gui very close to other Poplars which in winter can look partly green because of the abundant growth of the parasite.

There is no Oak on our list (Quercus robur) though we have been told of one place where Gui grows on Oak in Haute-Saône. It seems rarely on Oak anywhere. So how come the druids with golden sickles could gather Mistletoe from Oak, as perhaps on Angelsey, an island where Gui does not grow now (if it ever did)? That story comes from Pliny the Elder. Is it fully trustworthy? We hae oor doobts, as they say.  However, our scepticism may be misplaced regarding a special interest in Gui by the British (and/or other Celts) because of a very remarkable, intriguing, recent archaeological discovery from Germany. At Glauberg in Hesse the excavators dug up a life-size stone statue of a “Celtic Prince” from about 500 BC. He sports a headdress shaped convincingly like an opposite pair of Gui leaves. The shape is right even to the two not being a symmetrically matching pair. 

 At Poncey, France, six infested Poplars with Gui and, to the right, two Lombardy Poplars (with the upright branches) free of Gui, December 2012. Photo by Jim Dickson

Poplars along the Saône canal near Chemilly, France, everyone with Gui, November 2012. Photo by Jim Dickson.


Jim Dickson is a Scottish archeobotanist and photo contributor to E-Flora BC. He is well known for his work on Otzi, the Iceman. Jim, with his wife Genevieve Lecrivain, resides in both Scotland and France, but has visited BC to work on the BC iceman--Kwäday Dän Ts'ìnchí--studying the mosses that gave clues to his origin.  Some of Jim's publications include:  The Changing Flora of Glasgow: Urban and Rural Plants Through the Centuries, Bryophytes of the Pleistocene: The British Record and Its Chorological and Ecological Implications, Ancient Ice Mummies, and The Life and Death of Kwäday Dän Ts'ìnchí, an Ancient Frozen Body from British Columbia: Clues from Remains of Plants and Animals. 

View Jim's photos on E-Flora BC here. View Jenny's photos here.

Viscum album is not found in BC. It is native to Europe and western and southern Asia. Read more about this species here.

In British Columbia, we have four species of mistletoe reported, in the genus Arceuthobium: A. americanum, A. douglasii, A. laricis, and A. tsugense. A. tsugense has 3 subspecies.  Click on the links to view the atlas pages.