The wrack wall and how storms can tear seaweed from their rocks.

In the last posts, Lena has been reporting on all the interesting finds you can make on the beach after a storm. However, these haven’t been all that much about the different species of seaweed that gets washed ashore during strong winds. So, here is a small exposé of what she found after the storm Sven (Bodil in Denmark, Xaver in Germany).

In some bays on the west coast at Tjärnö, seaweed forms large beach walls whereas in other bays you will only find a few specimens of what is growing just a couple of meters off shore. Seaweed can also come entangled in ropes and lines from far away.
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A photo from a bay filled with seaweed forming thick carpets. Later in the year, in the summertime, they will have been decomposed and form a beach wall covered in lush green plants. Seaweed and algae make excellent compost due and was formerly gathered to fertilize the potato patches. If you find a bay full of seaweed you can collect some and put in your garden.
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On other shores, like in this photo, there is only some seaweed and the red alga Furcellaria lumbricalis in a band just by the water. This is the popular sandy beach at Saltö.
Higher up on the shore some distance away, i found a pile of rope and entangled algae. On closer examination, it turned out to be seaweed from quite some distance, maybe as far away as England.

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How can you tell that the seaweed is from far away and not just from next bay or further down the coast? If you look closely at the photo underneath, you’ll see some long, brown slightly knobbly bands, which are the reproductive organs (receptacles) of Himentalia elongata, which has never been found attached in Swedish waters. The nearest site is in Norway. In the pile there is also very large bladders of Ascophyllum nodosum and a form of bladderwrack (Fucus vesiculosus)with several bladders that is much more common in areas of higher salinity that at the Swedish coast.
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Those of you who look closely on the photograph will notice a red algae on the bottom right, like small, finely branched bushes attached to the Ascophyllum nodosum. This is one of many Polysiphonia species, and this particular species is commonly found growing on Ascophyllum nodosum and it is called Polysiphonia lanosa.
The wrack wall consists, as one might guess, mostly of wracks that have been washed ashore, both bladderwrack and serrated wrack (Fucus serratus). The smaller specimens were still attached to blue mussels (Mytilus edulis)and others had not attached hard enough to rock or boulder and had come loose.

Different sizes of wrack washed ashore, with accessories.

Different sizes of wrack washed ashore, with accessories.

Slightly larger specimens were washed ashore still attached to pebbles. A larger plant of seaweed is very firmly attached to the rock surface and you can lift the rock by holding the seaweed sometimes. It’s not until the wracks get really big that the pull of the wave manages to tear them loose from the rock or boulder to which they are attached. But, if you look closely on the bottom of the holdfast, there is a white calcareous layer. The wrack that has come loose with holdfast has once settled as a small germling on a crustose calcareous algae or a barnacle. So what has actually come loose by the wave force is not the seaweed holdfast, but the barnacle or calcareous alga that can no longer hold on to the rock surface.

sågtångsfäste

The photo shows a holdfast from a Fucus serratus with clearly visible white parts of a calcareous crustose alga.
nyårsskål för alger
And finally – a somewhat late toast for the new year and wishing you all a happy 2014 from the BalticSeaWeed blog.

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“Cinema Seaweed”

Here in Sweden, the frost is making everything sparkling white, and our noses and cheeks red. So what could make us warmer than some Cinema Seaweed? During summer and autumn, several seaweed movies have appeared on YouTube. This is a trend that we hope will last.

Here are links to nice seaweed movies that we have come across.

Nyköpings municipality, just south of Stockholm, has really got the hang of how to show itself from its best side!
Here you can see the two localities Långskär and West Kovik. The gurgling sound you hear is when the snorkel is filled with water.

From Skälderviken down south in Skåne county we can see that both bladderwrack and serrated wrack have recovered. It is also shown that 2013 was an incredibly successful year for the brown algae Dead Man’s Rope (Chorda filum) along most of the Swedish coast.
The movie is by Virtuerack. Virtue is a resource for schools, created by the Faculty of Science at Gothenburg University and The Maritime Museum & Aquarium in Gothenburg. They also have more movies where they show how cd-discs are being placed under a jetty in the sea and become habitat for several algae and animals.

Do you have any nice seaweed movies? Please let us know.

Seaweed course in Denmark

The week has been spent in Denmark, on a full Sunday to Sunday course to learn more about macroalgae.
With a schedule so full you can hardly fit it to a paper, the hopes and expectations to become a real seaweed guru are high.
There are 11 PhD students partaking, all from different countries!
The course is arranged by Aarhus University, as you can see in their newsletter (sorry, only in Danish).

Our first day of the course, we went out to collect macroalgae in the field. We started at the pier next to Ebeltoft harbour, where the sun shone and it was lee on the inside where we were working. I took this years “first swim without a drysuit in Nordic waters”. It was a refreshing 16 degrees Celsius and I was in the water for about 10 minutes, collecting material. Here there were four Fucus species growing: Fucus spiralis, Fucus vesiculosus, Fucus evanescens and Fucus serratus. Jackpot!

Lots of seaweed!

Lots of seaweed!

After a field lunch of sandwiches, we headed north, to Grenaa. Here, the Marine Home Guard and their boat took us out on Kattegat! What a luxury! This is a new collaboration between the Home Guard and Aarhus University, so the Danish TV was out and filmed us. Click here and fast forward to 1:19 into the clip and there we are.

Monday evening and Tuesday was spent going through the collected material to determine the different species and look at their different physiological structures.
On Wednesday, we tried to reproduce sugar kelp ( Saccharina latissima ) by getting them to release spores. It didn’t quite go as planned, so we took some good old bladderwrack and got it to release eggs and sperm instead.

On Thursday, we went to Algcenter Grenaa and had a look around. Pictures from our visit you can see the Algcenter website

Anette Bruhn show us how they cultivate sugarkelp at the Algcenter

Anette Bruhn show us how they cultivate sugarkelp at the Algcenter

We also got to visit the Kattegat Center, located just across the parking lot. This is one of Denmark’s many fine aquariums that have long been on my wish-to-see list. It was just as good, if not better, as I had expected. There was even an exhibition of algae and their importance. It is totally worth a visit!

Friday and Saturday were devoted to compiling and analyzing all of our data, and then present it in four groups according to various themes (Taxonomy, Monitoring, Light and Cultivation).

Danish seaweed; red, brown and grøn

Danish seaweed; red, brown and grøn

Fucus serratus – Serrated wrack

Serrated wrack, Fucus serratus, is easily recognized by its serrated edges. In the Baltic Sea we can find serrated wrack along the Swedish coast up to the Gryt archipelago in Östergötland, where the salinity is approximately 7 psu. We have not found any observations of its distribution along any other Baltic countries coastlines. If you know of any such, please let us know.

Serrated wrack (Fucus serratus) on the Swedish coast

Serrated wrack (Fucus serratus) on the Swedish coast

Serrated wrack is sensitive to dehydration and is not as tolerant as i.e. bladderwrack to air exposure. Where we find baldderwrack and serrated wrack living together, the serrated wrack is often found slightly deeper thatn the bladderwrack. Outside the east coasts of Öland and Gotland, for example, there are wonderful forrests of serrated wrack at about 8 m depth.

Serrated wrack thrown ashore by waves often gets a more brown-orange colour before it dries and turns almost black.
In the winter, you can find frost covered seaweed when you walk along the shore.

Frozen Fucus serratus

Frozen Fucus serratus

More information will follow.

The Baltic Sea

The Baltic Sea is unique because of its low salinity. In the northernmost parts, the water is almost considered freshwater, whilst the salinity at the entrance/exit in Öresund lies around 15 psu (practical salinity unit, roughly equal to ‰ and denotes salinity). The low salinity of the Baltic Sea makes it a stressful environment for both freshwater and marine species, both groups lives on the very edge of their tolerance of either too high or too low salinity.

Salinity and Fucus distribution in the Baltic Sea

Salinity and Fucus distribution in the Baltic Sea

The map show surface water salinity and the distribution of the three species from the genus Fucus that can be found in the baltic Sea.
Green denotes bladderwrack (Fucus vesiculosus)
Orange denotes narrow wrack (Fucus radicans)
Yellow denotes serrated wrack (Fucus serratus) Note that for this species only the distribution along the Swedish coasline is shown, since we have not found any data on its distribution in any other countries along the Baltic Sea.

More information will follow.