Too hot to handle?

The ice is disappearing… Over this winter there was no walking on the sea around Helsinki, or in much of Finland for that matter.

In January the ice cover was dramatically lower than normal for the Baltic Sea. Normally the ice should extend from the northern parts of the Baltic down to the Gulf of Finland and the Gulf of Riga, however this year the ice was limited to just a small section of the Bothnian Bay.

Indeed this lack of ice is a tell-tale sign of a milder winter, both on land and in the sea.

Extent of ice coverage (jäätä) in the northern Baltic Sea under normal condition and those observed in January 2020. Number on ice indicate thickness. Source: Finnish Meteorological Institute

But was last winter an odd exception?

It appears not. The earth is experiencing a warming of the marine environment in general, but the Baltic Sea is warming far more severely than the average global ocean. The Baltic Sea temperature is now higher than that average temperature recorded between 1981-2010 (European Environmental Agency, 2019)

Decadal global and Baltic Sea averaged sea-surface temperature anomalies relative to a 1981-2010 baseline. Source: European environmental agency

However it is not solely the increase in temperature that is concerning for the marine environment. Shorter spells of prolonged warmer temperatures, called marine heatwaves, are also troubling.

Due to climate change the IPCC (2013) expects marine heatwaves to become more frequent, and those that we do experience to be far more intense. Already the marine environment has experienced a 54% increase in annual marine heatwave days (Oliver et al., 2018).

And Finland is no exception. Monitoring at the University of Helsinki’s Tvärminne Zoological Station points that last winter was just one long marine heatwave. Exceptionally warm conditions lasted an outstanding  142 days, and even included record breaking temperatures in February 2020 (@Tvärminne, 2020).

Water temperature over the winter of 2019/2020 recorded by temperature loggers in shallow areas near Tvärminne. Source: Tvärminne Zoological Station .

Are marine heatwaves really all that bad?

Prolonged high temperatures can induce heat stress in marine plants and seaweeds with disruptive consequences to the survival of these organisms.

This stress can reduce a marine plant or algae’s ability to persist within previously inhabited areas. Consequently heatwaves have the potential to cause local extinctions.

By 2200 three currently common seaweeds; bladder, serrated and knotted wrack; will have disappeared from any North-Atlantic shore south of 45 ° latitude due to marine heatwaves and the other effects of climate change (Jueterbock et al., 2013).

4 © OCEANA Juan Cuetos 70537

Serrated wrack, Urter island, Karmøy, Norway (Image source ©OCEANA)

How will marine heatwaves affect Baltic Sea ecosystems?

Recent research at GEOMAR Helmholtz Centre for Ocean Research sheds some light on this.

By using large, outdoor tanks called ‘mesocosms’, researchers tested how eelgrass and bladderwrack respond to heatwaves (Saha et al., 2019). Within these 1,500l tanks the eelgrass and bladderwrack were subjected to 9 day heatwaves.

EUO © OCEANA Carlos Minguell 20130706_Puck Bay_157

Eelgrass meadow, Puck Bay, Poland (Image source ©OCEANA)

So how did the plant and seaweed cope?

Well is seems that both eelgrass and bladderwrack are fairly resilient to heatwaves. The eelgrass did experience impaired growth, but also showed good signs for potential recovery. Bladderwrack, on the other hand, showed no impaired growth with the only significant effect being seen on the bacterial community living on the algae.

Therefore it seems that both eelgrass and bladderwrack will likely be able to endure short heatwaves similar to those of this experiment when experienced within the natural environment.

EUO © OCEANA Carlos Suárez 45888_2

Wrack, Västra Banken, Bothnian Sea, Sweden (Image source ©OCEANA)

However it is not all good news. The effects of long heatwaves will probably be fairly different. In a previous study subjecting eelgrass to a continuous 3 week heatwave far greater detrimental effects where observed (Winters et al., 2011).  

So a tolerance to short heatwaves does not necessarily equate to a tolerance to longer ones. Consequently the length of each heatwave will be critical to determining the effects on eelgrass and bladderwrack.

We will have to endure more and hotter marine heatwaves, as will the resident plants and animals of the Baltic Sea, yet at least eelgrass and bladderwrack seem somewhat prepared for the future.


Sources:

@Tvärminne, 2020. Tvärminne Zoological Station. Date accessed: 28/5/20. https://www.facebook.com/Tvarminne/posts/2426296717472671

European Environmental Agency, 2019. Decadal average sea surface temperature anomaly in different European seas. Date accessed: 29/5/20. https://www.eea.europa.eu/legal/copyright

IPCC, 2013: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 1535 pp, doi:10.1017/CBO9781107415324.

Jueterbock, A., Tyberghein, L., Verbruggen, H., Coyer, J.A., Olsen, J.L. and Hoarau, G., 2013. Climate change impact on seaweed meadow distribution in the North Atlantic rocky intertidal. Ecology and evolution3(5), pp.1356-1373.

Saha, M., Barboza, F.R., Somerfield, P.J., Al‐Janabi, B., Beck, M., Brakel, J., Ito, M., Pansch, C., Nascimento‐Schulze, J.C., Jakobsson Thor, S. and Weinberger, F., 2020. Response of foundation macrophytes to near‐natural simulated marine heatwaves. Global Change Biology26(2), pp.417-430.

Winters, G., Nelle, P., Fricke, B., Rauch, G. and Reusch, T.B., 2011. Effects of a simulated heat wave on photophysiology and gene expression of high-and low-latitude populations of Zostera marina. Marine Ecology Progress Series435, pp.83-95.

Does diversity matter?

We are currently in a biodiversity crisis. The rate of extinction is 100 to 1000 times faster than the natural rate (Singh, 2012) and by the end of the 21st century we will have lost at least 50% of all species (Myers, 1993).

Earth render 5

A view from space

Undoubtedly, this species loss will have overwhelming effects on how we live. Biodiversity loss is not only an environmental issue, it also directly effects us as a society, as well as our development, economy and security. In fact the UN (2019) declared that biodiversity loss undermines progress towards 80% of the assessed targets of their Sustainable Development Goals.  

Much attention has been focused on the loss of species, such as the charismatic black rhino or the snow leopard. With more than 31,000 species threatened with extinction (IUCN, 2020) this is understandable. Species are undeniably important and we should aim to conserve them, but we should not ignore the fact that we are losing so much more than just species in this biodiversity decline.

Marwell Zoo - Snow Leopard

Snow leopard, Marwell Zoo, UK

Biodiversity manifests throughout scales, from ecosystems, communities, species, and even genes. Genetic diversity, or the variety of genes, is a vital part of biodiversity. Yet genetic diversity is frequently overlooked in international conservation policies.  

Genetic diversity can be represented between species: you are genetically different from your pet cat; or within species: both you and I share different genes. If genetic diversity declines within a species there can be devastating consequences to the stability and functioning of that species.

In the case of the Florida panther low genetic diversity led to a range of severe problems. In fact the species was slated for extinction, with only ~30 individuals remaining (Ohio State University, 2019). Luckily for the Florida panther this downward spiral was rescued by the addition of new genes into the genepool from eight Texas puma females. This increased genetic diversity has saved the Florida panther and now at least 230 roam the wilds of Florida.  

But what about species that have natural populations with sustained low genetic diversity?

Seagrasses have notoriously low genetic diversity, often forming vast meadows of a few clones. The genetic diversity within these meadows, though conventionally low, is also important. Seagrass meadows with greater numbers of genetically different individuals have far better growth after disturbance compared to meadows of a single clone (Reusch et al., 2005; Hughes & Stachowicz, 2011). So even in species with typically low genetic diversity, higher diversity can be beneficial.

This highlights that policy makers are making a big mistake overlooking genetic diversity. By taking genetic diversity into account we could vastly improve the effectiveness of our conservation measures. Hence, if we want to successfully conserve a species, especially a threatened species, the conservation of the genetic variation within the species is of the utmost importance.


Sources:

Hughes AR, Stachowicz JJ. 2011. Seagrass genotypic diversity increases disturbance response via complementarity and dominance. Journal of Ecology 99:445-453

IUCN 2020. The IUCN Red List of Threatened Species. Version 2020-1. https://www.iucnredlist.org. Downloaded 30 April 2020

Myers, N. (1993). Biodiversity and the precautionary principle. Ambio, 22, 2/3:74-79

Ohio State University. (2019, October 3). How the Texas puma saved the Florida panther: Uncovering the genetic details of a conservation success story. ScienceDaily. www.sciencedaily.com/releases/2019/10/191003111755.htm. Downloaded 29 April 2020

Reusch TBH, Ehlers A, Hämmerli A, Worm B. 2005. Ecosystem recovery after climatic extremes enhanced by genotypic diversity. Proceedings of the National Academy of Sciences of the United States of America 102:2826_2831 DOI 10.1073/pnas.0500008102

Singh, J. S. (2002). The biodiversity crisis: a multifaceted review. Current Science82(6), 638-647

United nations [UN] (2019) www.un.org/sustainabledevelopment/blog/2019/05/nature-decline-unprecedented-report/. Downloaded 30 April 2020

What happens in the deep?

Beyond the range of conventional diving and above where submersibles normally roam lies a unique habit rarely studied. Exploration of this new world leads to the discovery of a new wealth of biodiversity; upon each exhibition to the deep scientists come back with brand new species never known to science before.

But does seaweed really live 100m below the surface where light barely touches?

Divers Descending to Deep Ledge

NOAA scientific divers descending to 150ft, Pearl and Hermes Atoll, Hawaii

Well yes they do, in fact they can be even more abundant than the neighbouring corals. Carpets of reds and greens, with shoots up to 1m long, bloom throughout this range. Not only that but walls of mushroom-like brown algae and beds of fine green seaweed are amongst the other seaweeds that can be found.

So even in deep waters seaweeds are important players in the marine ecosystem.

And if you ever wondered what it entails to be a seaweed researcher then this is a great example. Here at FunkVeg we use many of the same techniques and can vouch for the completely new level of awkwardness these pesky critters create.

Any seaweed lover should check this out!

Learn more about deep sea algae here

Or watch the whole video here

What’s all the fuss about foundations?

What do kelp forests, mussel beds, seagrass meadows and coral reefs have in common? They are all given their name by the foundation species that creates them.

But what does being a foundation species entail?

Great Barrier Reef, Australia

Just as the foundations of your house provide structural stability keeping you house strong and stable, so too does a foundation species within an ecosystem. Because of this they are vitally important in structuring the community and maintaining a healthy ecosystem.

With the growing influence and uncertainty of human activity and environmental change the stability of the world’s ecosystems is questionable. It is therefore imperative that we understand what keeps ecosystems stable.

We know that foundation species are pivotal in ensuring ecosystem stability; but few have quantified it. Fortuitously nearly two decades worth of data and observations exists courtesy of the Santa Barbara Coastal Long-Term Ecological Research Project. Using this data researchers at the UC Santa Barbara’s Marine Science Institute posed the question:

‘Does a stable giant kelp forest result in a more stable understory community?´

MBNMS - Anemone in Kelp

Anemone in Kelp, Monterey Bay National Marine Sanctuary, USA

Well it turns out it does. Just as stable foundations ensure your house stays up, so too does a stable forest of kelp help in maintaining the stability of the under-story community of plants and animal.

Unfortunately in the face of climate change the stability of kelp is likely to change in the future. This could have devastating effects of all the plants and animals that rely on the kelp forest. Not only this, but this new research suggests that all habitats reliant on foundations species may also face such similar problems. Without the important species providing a foundation for all the other plants and animals, we could see devastating changes to these iconic habitats.

So the take home note:

Just as you have to take care of the foundations of your house to prevent it collapsing, so too do we have to take care of the foundations of our ecosystems or face calamitous consequences.

Scorpionfish In Seagrass

Scorpionfish in Seagrass, NOAA Florida Keys National Marine Sanctuary, USA

If you want to read more about this research check out this link or article below:

https://www.news.ucsb.edu/2020/019772/strong-foundation

Lamy, T., Koenigs, C., Holbrook, S.J., Miller, R.J., Stier, A.C. and Reed, D.C., 2020. Foundation species promote community stability by increasing diversity in a giant kelp forest. Ecology, p.e02987.

The demise of Baltic Sea wrack?

Another post about climate change, but this time closer to home. Climate change has been identified as one of the largest contributors to environmental change within the Baltic Sea. It is predicted that Baltic waters will heat by some 2–4°C and become up to 50% fresher by the end of the twenty-first century (Meier 2015).

Coastlines of the Southern Baltic Sea

Coastline of the Southern Baltic Sea

But how will Baltic wracks fair under these new conditions?

Unfortunately the future doesn’t look good for bladderwrack. Research by Antti Takolander and colleges at the University of Helsinki indicated that warming waters and increased freshness pose real threats to bladderwrack. The once abundant brown seaweed may struggle to cope with these new environmental conditions and consequently be lost from much of the Baltic Sea.

Bladder wrack peeking up above the water 4

Bladderwrack – Brofjorden, Sweden

Climate change looks bad for bladderwrack, but is that the case for all wracks of the Baltic Sea?

It seems that the future may not be as bleak for all the Baltic Sea wracks after all. Narrow wrack, having evolved within the Baltic Sea from bladderwrack, can be found nowhere else in the world. As a unique seaweed to the Baltic you might expect that the dramatically changing conditions predicted pose an even greater threat to this sister of bladderwrack. Yet a study by Luca Rugiu and colleges at the University of Turku indicates that this is in fact not the case. By subjecting narrow wrack to higher temperatures and fresher conditions replicating predicted future conditions they assumed that narrow wrack would fair as poorly as bladderwrack; however their results were surprising. Though the predicted future conditions did lead to higher mortality, those individuals that did survive were larger and grew faster.

Bladderwrack (Fucus vesiculosus) and Narrow wrack (Fucus radicans) living side by side – SW Gulf of Bothnia (northern Baltic Sea) [From Pereyra et al., 2009; CC BY 2.0]

Does this mean that narrow wrack may benefit from climate change?

In short: Yes. Those narrow wrack individuals that can withstand the predicted future conditions will benefit from the increased growth and gain a competitive advantage over those that cannot. Since where each wrack can be found is largely affected by competition between the species the future looks even worse for bladderwrack. Both wracks frequently grow side by side and if narrow wrack profit and bladderwrack lose out from future climate conditions bladderwrack may be lost from these areas and instead replaced with narrow wrack.

The future looks bleak for bladderwrack; we may end up losing vast swathes of bladderwrack forest in the Baltic. Though there is the small silver-lining that narrow wrack appears somewhat tolerant to climate change. So the future may not be all bad. We won’t see the disappearance of all the wracks from the Baltic Sea; though we will see a very different Baltic then we see today.


Sources:

Meier HEM (2015) The BACC II Author Team, Second Assessment of Climate Change for the Baltic Sea Basin, Regional Climate Studies, DOI 10.1007/978-3-319-16006-1_13

Takolander, A., Leskinen, E. and Cabeza, M., 2017. Synergistic effects of extreme temperature and low salinity on foundational macroalga Fucus vesiculosus in the northern Baltic Sea. Journal of Experimental Marine Biology and Ecology495, pp.110-118.

Rugiu, L., Manninen, I., Rothäusler, E. and Jormalainen, V., 2018. Tolerance to climate change of the clonally reproducing endemic Baltic seaweed, Fucus radicans: is phenotypic plasticity enough?. Journal of phycology54(6), pp.888-898.

The unsung hero in the fight against climate change

Buzzword of the day: Climate Change

You will have needed to be living under a rock to have not heard all about the controversial topic of climate change.

Human-induced climate change is having a dramatic effect around the world. In 2017 human-induced warming reached approximately 1°C above pre-industrial levels, with 20–40% of the global human population living in regions that have already experienced warming of more than 1.5°C above pre-industrial in at least one season (IPCC, 2018).

But why should we worry that the world is warming?

Human-induced global warming has already caused multiple observed changes in the climate including more frequent land and marine heatwaves, increases in the frequency, intensity and/or amount of heavy precipitation events, and an increased risk of droughts (IPCC 2018).

So what is causing this problem?

The answer: Greenhouse gases.

The most infamous culprit being carbon dioxide (CO2). At Mauna Loa observatory, a remote research facility located on the slope of Mauna Loa volcano [Hawaii], scientists have been recording atmospheric CO2 levels for the past 60 years and the trends are quite disturbing. Atmospheric CO2 has increased dramatically since recording first began, from 317ppm in 1960 to a high of 415 ppm in May 2019 (NOAA, 2019).

Monthly mean atmospheric carbon dioxide measured at Mauna Loa Observatory, Hawaii

Well maybe seaweed can help..

It is well publicised that trees can remove CO2 from the atmosphere by incorporating the carbon into plant material. But did you know that marine plants can help with storing CO2 from the atmosphere too? Just as with land plants, carbon can be incorporated into marine plants directly or stored in the surrounding sediment. Surprisingly marine plants can even contribute to the long-term storage of carbon in the deep ocean.

Yet it had been assumed that seaweed had little influence in storing CO2 from the atmosphere. In fact seaweed isn’t even included within the Blue Carbon initiative; a global program aiming to lessen climate change through coastal ecosystem management; whereas seagrasses, saltmarshes, and mangroves are. However a recent study published in Nature geoscience challenges this perception. Marine scientists from KAUST have confirmed the importance of seaweed in contributing to deep ocean carbon storage.

Seaweed community at Penguin Island [AU]

Unlike rooted seagrasses and mangroves, the majority of seaweed are rootless and do not remain fixed indefinitely but instead can drift on the currents and tides. This has made estimating their contribution to locking carbon away challenging. However using some cool molecular techniques this study shows that seaweed can be found regularly at depths greater than 1000m. We know that below this depth the carbon is unlikely to return to the atmosphere, and therefore can no longer contribute to the atmospheric CO2.

So it turns out seaweed could have a very important role in helping us fight climate change.

Want to know more? Check out the link below:

or find the published article:

Ortega, A., Geraldi, N.R., Alam, I. et al. Important contribution of macroalgae to oceanic carbon sequestration. Nat. Geosci. 12, 748–754 (2019) doi:10.1038/s41561-019-0421-8

https://rdcu.be/bZzWS


Sources:

IPCC, 2018: Global Warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty [Masson-Delmotte, V., P. Zhai, H.-O. Pörtner, D. Roberts, J. Skea, P.R. Shukla, A. Pirani, W. Moufouma-Okia, C. Péan, R. Pidcock, S. Connors, J.B.R. Matthews, Y. Chen, X. Zhou, M.I. Gomis, E. Lonnoy, T. Maycock, M. Tignor, and T. Waterfield (eds.)]. In Press. https://www.ipcc.ch/sr15/

NOAA (National Oceanic and Atmospheric Administration), Earth System Research Laboratory Global Monitoring Division [online], 5/12/19, Date Accessed: 23/12/19. https://www.esrl.noaa.gov/gmd/ccgg/trends/mlo.html

Sea Urchin Ranching – the new restorative fishing practice?

Vast plains of barren emptiness, devoid of life, bar one animal: the purple sea urchin. These barrens used to be some of the most productive habitats on the planet, now they are empty wastelands. 

Urchin Valley

Purple sea urchin barren – San Miguel Island, California, United States

So what happened? 

Like a story from the bible, plagues rained down on this once pleasant land. First came pestilence. The sea stars started wasting away. Next came years of extreme heat, with coastal Californian waters reaching record breaking temperatures. And finally an explosion. An explosion of purple sea urchins. Everywhere you look would be purple sea urchins. These ravenous monsters devoured the plentiful forests, one unfortunate kelp individual at a time, until nothing was left but the barren wasteland we see today. 

Sea Star Wasting Syndrome

Ochre sea star suffering sea star wasting disease – North Beach, Washington, United States

Soon there were terrible consequences for the locals as well. With the loss of kelp forests, commercial shellfisheries collapsed. Red abalones declined by 80% and many livelihoods were shattered.

All is not well on these urchin barrens either, for too much competition leads to empty stomachs. Each urchin, competing against its brothers and sisters, now finds food scarcity a real pressing problem. So many mouths to feed, nowhere near enough kelp to eat.

Purple Sea Urchin - Strongylocentrotus purpuratus

Purple sea urchins – Santa Cruz Island, California, United States

So it seems that no individual is particularly happy after this catastrophic chain of events, not the starving sea urchins, the decimated kelp, or the troubled fishermen. 

But there may be a solution, and one in which may please all involved parties, at least in part. 

The urchins are hungry, so firstly why do we not just feed them? This sounds like such an obvious idea. So let’s take the urchins from their barrens and rehome them in special ranches, where they are provided with plentiful food and allowed to grow plump. This is where the urchin’s story gets a little less happy for them. Unfortunately for them, they are considered quite the delicacy, which conversely is quite pleasing for the fishermen, who can make a good living from fattening up urchins for slaughter. Though the urchin’s eventual fate is not necessarily such a pleasant one, they have at least had a good life eating as much as they please up until the end. And the fishermen make a tasty profit. 

But best of all, the biggest beneficiary from all of this is the kelp itself. Once the ravenous urchins are removed the kelp can grow at an enormous rate, one of the fastest on the planet, and restore the wasteland to its former glory. 

So by choosing Californian sea urchins, you as a consumer can help support perhaps the only restorative fishing practice known today, one bite at a time. 

Ollie, the residential sea otter

Sea otter taking a nap in bull kelp – Race Rocks, British Columbia, Canada

Interested in finding out more? Check out the link below where you can find more info from the authors and the freely available article:

https://www.ucdavis.edu/news/california%E2%80%99s-crashing-kelp-forest/

Free-living Bladderwrack – Why should we care?

To answer this question it helps to look at the bigger picture: Why should we care about the natural environment at all? Though the reasons are many, one of the most obvious is that their functioning directly affects our society. This idea is the basis for the ecosystem services concept.

Ecosystems Services – What are they and why do we need them?

Ecosystem services are the benefits provided by the natural environment to society. They are the foundation of human well-being. These services are numerous and highly varied depending on the ecosystem. In forests and woodlands the production of wood as a raw material for the use in manufacturing is one such service. On a smaller scale, individual species can also provide important services, such as bees acting as pollinators for agricultural plants. These services are invaluable to human existence, and often come with no accompanying monetary cost. Being freely available, many are undervalued and consequently protection for the environments that provide them is frequently limited.

Though ecosystem services are often taken for granted, they are hugely important. Imagine if the continued use of pesticides, most famously neonicatoids, led to the extinction of numerous bee species. Many fruit and seed producing crops would be left unpollinated, leading to crop failure and the consequential food shortages within shops and supermarkets. Hence the ecosystem services we take for granted can have monumental effects on society and our quality of life. It therefore seems necessary to provide protections for these environments so that they can continue to provide the services we rely on.

So now we know what Ecosystem Services are – How does this relate to bladderwrack?

As an underwater environment that many people rarely, if ever, see bladderwrack forests are a hugely underrated environment in terms of their value and the ecosystem services they provide. However bladderwrack forests can be considered similar to giant kelp forests, which are some of the most productive habitats on earth.

Bladderwrack forests are highly productive environments storing large quantities of carbon. Because some of this carbon is sequestered bladderwrack can be considered to provide a service in reducing CO2 within the atmosphere and thus help our society with mitigating climate change.

This is not the only services these underwater forests provide. As an ecosystem engineer; a creature that modifies its environment; bladderwrack also provides the additional benefits of food and shelter for a myriad of different plants and animals, all of which themselves contribute to the ecosystem services provided by this habitat. Notably bladderwrack plays an important part in food production by providing nursery and feeding habitat for juvenile fish of commercial importance including cod, pike and perch. By supporting populations of these important fish species they also provide valuable recreational services including recreational fishing, boating and SCUBA diving.

Plaice resting next to an attached bladderwrack stand

An entirely different service that bladderwrack provides influences people’s health by reducing their contact with harmful environments. Within the Baltic Sea, the enrichment of water bodies with excessive nutrients has led to widespread eutrophication and resulting nuisance blooms of cyanobacteria. These blooms can be detrimental for human health and are monitored by the Finnish Environmental Institute SYKE. Importantly though, bladderwrack forests can act as filters against high nutrient inputs from terrestrial sources, providing a service in reducing excessive load of nutrients and consequently benefiting human health and well-being.

These are just a few of the ecosystem services this fascinating habitat provides, though there are numerous others that have not been listed here. We can therefore conclude that both bladderwrack and the associated community of plants and animals are important for the Baltic Sea ecosystem and many of the services we require.

What about free-living bladderwrack and the associated animal community?

Since free-living bladderwrack fulfils a similar ecological niche to the attached form, albeit generally on soft bottoms rather than rocky substrates, we surmise that it provides similar ecosystem services as well. Both forms support a similar animal community living around and on the seaweed, but the free-living form also supports an additional community living within the sediment below the algal mats. It is likely that this community will provide additional services that benefit us, however what these services are is difficult to tell unless we have a greater understanding of the associated animal communities of the free-living form. Hence this is where our study comes in. In one of our projects we are interested in identifying the animals on and below the surface of the sediment, and how these communities vary from those of bare, soft bottoms. To find out how important these creatures are to our society we will delve below the surface of this barely studied habitat.

Free-living bladderwrack forest

The curious case of free-living Fucus: what is it and where does it come from?

Bladderwrack (Fucus vesiculosus) is a brown algae commonly found within many parts of the Baltic Sea. It forms structurally complex habitats at depths of 0.5-7m, providing shelter and food for many marine invertebrates and fish. It is one of the major foundation species in the Baltic Sea coastal zone. Generally, bladderwrack is considered a rocky shore organism, being most notability found growing attached to rocks, boulders and pebbles. However, interestingly an unattached form can also be found.

A meadow of free-living bladderwrack, resulting in 100% coverage. Image taken in the Askö area (Sweden)

These unattached individuals form free-living populations, that can be quite extensive (10-100m2) occurring year after year at the same sites. They have been observed since the late 19th century (Kjellman, 1890) and are generally described as pieces torn from attached populations and deposited in sheltered locations, with no ecological significance. However with modern molecular techniques; including microsatellites and DNA barcoding; we aim to test this theory.

 

The origins of life?

Firstly we aim to test this long held idea that the free-living populations are solely supplied by the surrounding attached populations. To put it simply, do they rely on supplies of torn off pieces to start and replenish a population or are they fully or partially self-sustaining through their own means? This really is a question of ‘can they reproduce?’, and if so ‘how do they do it?’.

The processes involved in forming and maintaining free-living bladderwrack populations

We surmise that the founding members of any free-living population are supplied by pieces from attached populations, as has been suggested since their first documentation. However this is where the ideas diverge, rather than assuming any replenishment to the population are from supplies of material from the nearby attached population, we view that these free-living populations have some level of self-sustainability.

How do they do this? The current idea is through fragmentation, a method of asexual reproduction where new, smaller, genetically identical individuals are formed through breakage from the main individual. If you ever get your hands on a free-living bladderwrack individual, you will see how easily one individual becomes many with just the simplest of handling. Through splitting into many individuals that continue to grow and eventually break apart once more, soft bottoms can quickly become dominated by many genetically identical plants.

Two distinct morph types from different free-living populations around the Askö area (Sweden)

The level at which this asexual reproduction occurs will be defined by the amount of genetic variation within the population. If populations contain only a few genetically different individuals then we can assume that fragmentation plays a large role in maintaining these free-living populations. If we observe the reverse; many genetically different individuals; then it is likely that either attached populations are largely responsible for supplying these populations, or that the free-living plants can themselves reproduce sexually. The latter seems improbable, in part because few free-living individuals have been observed to form sexual structures known as receptacles.

 

Population connectivity?

Now that we have established the possible mechanisms for forming, maintaining and regenerating free-living populations, we can consider the dispersal of a normally immobile seaweed. It is frequently observed that broken off pieces from attached individuals can be transported by currents over great distances; and since reattachment is incredibly rare; either these free-floating pieces eventually sink becoming loose-lying pieces which eventually decay or they contribute material to free-living populations.

However the question is, are free-living individuals equally as mobile? Can free-living individuals migrate between patches, and do distances and other abiotic factors affect their dispersal?

We currently have little idea as to answering this question, but it seems likely that distance and geological features will be the major influences on the dispersal potential. By identifying the genetic variation; or the level of relatedness; between and among populations we will hope to answer this intriguing question.

 

Ecologically important?

Thirdly, we have little idea of the importance of free-living populations. What function and ecosystem services do they provide in the coastal zone? Through inhabiting soft bottoms, that are normally uninhabitable by the attached form of bladderwrack, they can provide a complex habitat that would normally not be found on this substrate type. Consequently this habitat can support a vast variety of plants and animals that would otherwise not be found in that location. Through environmental surveys and the monitoring of biological measurements we aim to identify the important functions and services that are provided by the free-living populations.

 

The importance of this study

Now comes the most important question: Why do we need to study these questions in the first place? As an integral part of the Baltic Sea ecosystem, free-living bladderwrack is considered an important biotope at risk of damage. As such they are listed on HELCOM Red List of biotopes and habitats as endangered (HELCOM, 2013). This means that policy makers and conservationists need to implement methods to best protect these populations. Without adequate knowledge, including the genetic diversity, of these populations successful management is doubtful. As such, if we wish to maintain the health of these populations and consequently that of the Baltic Sea, we need all the research we can collect.

 

References

HELCOM (2013) Red List of Baltic Sea underwater biotopes, habitats and biotope complexes. Baltic Sea Environmental Proceedings No. 138.

Kjellman FR (1890) Handbok i Skandinaviens hafsalgflora. I. Fucoidae., Stockholm