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Help our Kelp!!!

Image by Kyle McBurnie

Kelp Forests Provide a refuge from Ocean Acidification:-

But Could They Be at Risk from Climate Change?

Within a hidden underwater forest of

dense kelp that extends to 30m deep, the

limit of most scuba divers, there is an

abundance of activity. Juvenile fish and

marine mammals, swim amongst kelp

fronds, underwater forms of exaggerated

leaves, sheltered from predators. The

vigorous frond blades are adorned with

epiphytes of flat and feather-like

calcareous algae of pink and red hues to Image by Ian Skipworth

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green and brown turfing, bushy and foliose algae, providing a gastronomic delight for hundreds of

grazing gastropod snails, limpets and sea-urchins. These become a menu of prey for predatory whelks,

crustaceans, sea otters and fish. At the seabed holdfasts of kelp, mistakenly confused as roots, attach

to the bedrock, creating a cavern of niches. Within these niches a myriad of animals hide from

predators, whilst mobile animals crawl around the bedrock scavenging for detritus.

What are Kelp Forests?

These magnificent kelps are key habitat forming species, dominating temperate rocky reefs says

Professor Robert Steneck. They provide energy and food by photosynthesising. Supplying a safe haven

for over 1800 species, from predators and

wave exposure, they are a vital coastal and

marine landscape. Astonishingly, a single kelp

frond alone supplies a home for over 8000

individual organisms, from not only 40 species

of macroinvertebrates, such as crabs,

molluscs, sea urchins, as well as sponges and

hilarious sea-squirts, which, as their name

suggests, squirt seawater. As well as micro-

invertebrates, so small they can only be identified by high-powered microscopes, such as amphipods

and isopods that hop, skip and jump between the fronds. In addition, epiphytes, organisms that attach

themselves to kelp, such as membrane-like bryozoans and, turfing, feathery and encrusting algae that

offer a secondary home to those that choose. Kelp with coarse stipes supply additional homes for

animals and epiphytes to attach to, whilst holdfasts of various shapes, ranging from root-like to ruffled

fans, can support between 30-70 different types of species.

Just How Important Are They?

Dr. Juliet Brodie believes they are amongst the most productive ecosystems in the world, providing

over a kg of carbon per meter square per year by way of primary production. To put this into context,

this is between 3 to 10 times more than coastal phytoplankton adds Dr. Dan Smale. Although some

20% of kelp is consumed directly by grazing invertebrates, such as Sea Urchins and snails (that leave

tell-tale signs of holes where they’ve fed), 80% of its carbon is consumed as dissolved organic matter

or detritus, where older fragments of fronds have withered away with age.

Image by Brian Skerry

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Newly hatched fish make the most

of the tangled kelp, sneakily hiding

away from predatory terminators.

Whilst on the surface sea-otters

make use of the dense canopy as a

make-shift raft as they lie back,

enjoy the sunshine and break sea-

urchins with rocks for their supper,

safe from killer whale predation.

Deep-down below sessile invertebrates, such as sponges and tunicates hide away amongst the

holdfasts from predatory fish, sea stars and sea-urchins.

The magnitude in number of most individual kelps entwined together absorbs and weakens the power

of the strongest of currents and waves, protecting adjoining coastlines. Providing such a contrasting

environment frees the forest occupiers to go about their daily business, entertaining guests in the

holdfasts and flirting with each other amongst the fronds. To put this into context, imagine how it

feels walking home from the pub on a really windy night compared to a calm, moonlight sky.

Now for the Chemistry Part!!!

Atmospheric CO2 is absorbed by seawater, across a thin boundary layer on the surface and, dissolves

into an aqueous form. Almost 99% of this reacts with seawater, creating destructive carbonic acid

which, luckily, rapidly splits apart into 2 types of dissolved inorganic carbon, that are freely available

as the building blocks of sea life and, free Hydrogen ions. Hydrogen bicarbonate, as in bicarbonate of

soda, accounts for 90% of this dissolved inorganic carbon and,

carbonate the remainder.

For life to survive in the ocean, the chemical make-up of seawater

has to be at an optimum acid-alkaline balance. This is controlled by

seawater’s innate buffering capacity, known as alkalinity, which

resists changes in balance. This is measured by pH, which is the

negative logarithmic value of unattached, free Hydrogen ion

concentration. Optimum pH is around 8.2, so to maintain this level,

the addition of CO2 as Hydrogen Bicarbonate and Carbonate, is

balanced by equivalent amounts of free Hydrogen ions. As the

Image by Vancouver Aquarium

Image by Author

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amount of free Hydrogen ions increases pH levels drop, seawater becomes more acidic/less alkaline,

like bleach and this is where kelps help.

Different species of kelp take up Hydrogen Bicarbonate by a variety of different methods, known as

carbon concentrating mechanisms, and, inside their cells, convert this to Carbon Dioxide using an

enzyme known as Carbon Anhydrase says Pamela Fernandez. In the presence of sunlight, the Carbon

Dioxide is converted into Lucozade-like energy, glucose, releasing Oxygen into the seawater for fish

and animals to breath, just as we do. Whilst calcareous animals, such as crabs, snails and sea urchins,

and microscopic plankton that float around at the surface, make use of the available carbonate to

form their protective shells and plates.

Ocean Acidification – Climate Change’s Evil Twin

When the amount of CO2, dissolved into the water, exceeds the rate at which oceanic chemical

reactions can occur, it becomes so saturated, that excess free hydrogen ions form increasing amounts

of destructive carbonic acid, the equivalent of battery acid on our skin. As the protective shell coats

of animals are dissolved by this battery acid, the weaker they become to the environment and, more

easily consumed by predators, similar to how Coca-Cola dissolves aged dirt on coins.

Over the past 200 years to 2000 atmospheric CO2 increased, by a very high 33% to 360 ppm (parts per

million), amounting to 0.17% per year. Since

2000, monitoring records at the Scripts

Institute of Oceanography, Mauna Loa on the

idyllic islands of Hawaii, show current

atmospheric CO2 has increased, by a further

15%, to over 400 ppm or 0.94% per year. This

equates to an anxiously astonishing rate of

increase, between pre-2000 and 2016 of 73%.

At the same time, free Hydrogen ion

concentrations have increased, by 32%

between the 1800s and 2000, a rate of 0.16%

per year. This is predicted to increase by a total

of 70% in 2050 and a total of 130% by 2100, i.e.

at a rate of 1.4% per year says Dr. Ken Caldeira. This amounts to an increase, in the rate of Hydrogen

Ion concentration released into the ocean, of 8.75% between pre-2000 and 2050. “By 2050 we will be

Image by Katharina Fabricus

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in unknown territory, as pH levels are predicted to be lower, than at any point in the past 25 million

years” says Prof. Jason Hall-Spencer, a pioneer of research into the effects of ocean acidification at

natural CO2 seeps.

However, it is not necessarily as bad a situation as it could be, since there are winners and losers in all

walks of life. Excess CO2 is a great treat for photosynthetic algae and kelps, that take it up like it’s gold

dust, increasing their growth and primary production, as well as seawater alkalinity. On the other side

of the coin though, this lowers the availability of carbonate for animals using calcium carbonate, to

form their protective coatings and shells. But, due to the enormous density of kelp in these forests,

the amount of Hydrogen Bicarbonate they are able to absorb, can keep pH at normal levels during

daytime. Thus allowing animals to form their shells, as shown by Dr. Bruno Delille, who observed in

the sub-Antarctic, a 1.6% increase in seawater pH inside the forest, compared to outside.

Too hot to handle

Add to this seawater boiling away in a saucepan and, a

recipe for disaster begins to emerge, as our insatiable

desire for fossil fuels continues. The unstoppable rise of

greenhouse gases projected into the atmosphere creates

“radiative forcing”. Solar energy that is not absorbed by the

planet, is rebounded back into the stratosphere, becoming

trapped, known as “the greenhouse effect”. Like a mirror,

the stratosphere reflects back this extra solar energy,

accumulating heat and rising the planet’s temperature.

Just like ourselves being stuck in a sunlit office devoid of

open windows all day, kelp become stressed and over-

heated, by temperatures higher than their normal range of

5-20oC, depending on the particular species. This causes a

loss of their defence chemicals and pigments, similar to

melatonin which we rely upon to defend our skin against sunburn, frizzling their fronds, that inhibits

their photosynthetic working capacity.

Extreme elevated temperature events, also known as “El Nino” and “El Nana” years, are increasing in

number. As Dr. Dan Smale says temperature increases of 2-4oC, a 7.8-16% increase above the ~20oC

norm in Australia, 5 years ago, are increasing. Curtailing regions in which Kelp Forests can occupy,

Image by Sandy Didine

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both now and in the future. Dr. Juliet Brodie has pointed out that the warming of the NE Atlantic alone,

is already causing a poleward shift, of species adapted to cooler waters of below 13oC, such as

Laminaria hyperborea and L. digitata. Along the eastern coast of the Pacific Ocean, in the sunshine

state of California, only a 3oC rise in temperature is enough to reduce growth in the giant kelp,

Macrocystis pyrifera, says Matthew Brown. However, ironically, he goes on to say that, when coupled

with increased CO2, the opposite occurs.

Wild as the Wind

Increasing storms, such as

Hurricane Katrina, add to the

vulnerability of Kelp Forests. On

the one hand, kelp forests require

a certain degree of wave and

current flow, to remove sediment

from blocking the sunlight they

need to photosynthesise. Dr. Dan

Smale has shown that, in the “wild

west” of the Northern Scottish

Isles, an increase in wave speed of

an astonishing 538%, from 0.16 to

1.02 meters per second, has a profound effect. The number of individual L. hyperborea per square

meter rose dramatically, by 66% from six to ten and, like a runaway train, frond length increased by

41% from 1.7 to 2.4 meters.

Along the western and southern coasts of the UK L. digitata and L. hyperborea entwine together, but

epiphytic animals and algae are discerning in their choice of stipe. They choose the sandpaper surface

of that of L. hyperborea, to which they can form an attachment, as oppose to the smooth, glossy

surface of L. digitata. But with this comes at a price. L. hyperborea snaps as waves crash down, unable

to cope with the pressure, whereas the flexibility of L. digitata can absorb this. The result: an epiphytic

habitat lost, forever, as it is washed upon the shoreline, leaving broken L. hyperborea fronds floating

amongst the surface.

Image by www.boatus.com

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The UK is not unique for this. All over the world increasing hurricanes are decimating and, destroying

our underwater magical forests. Only to be replaced by rocks and boulders, smothered with slimy,

gruesome, turfing green algae, that provides no protection for animals, fish and our coastlines.

The Future?

The pernicious cocktail of ocean

acidification, increased warming

and strengthening storms is

placing one of the few jewels

left of our oceanic world in

jeopardy. Now is the time to act.

To protect these forests that

provide a healthy ecosystem, a

storage for excess CO2 and a

habitat abounding with an array

of exquisite micro and macro-

animals, fish and algae.

Deforestation has already wiped

out kelp in Canada, California,

Central and South America, not

to mention Europe, Japan and

Australasia. If we do not act

now, to reduce our unnecessary,

excessive use of fossil fuels, we

risk losing even more

environments which they

occupy, to invasive, non-native, competitive species, as suitably climatic areas become more and more

constricted. We have a choice now, we have a chance to turn things round, a challenge to act against

the greatest threat mankind has ever known. Let’s take that chance to better the future for our

children and their children and the planet they inherit from us.

Matthew Brown is a researcher at the Department of Biology, San Diego State University, San Diego, California, USA. Dr. Ken Caldeira is a senior scientist at Carnegie Institution for Science (Global Ecology), Stanford, California, USA researching issues related to climate, carbon, and energy. Dr. Bruno Delille is a Research Associate at FRS-FNRS Chemical Oceanography Unit, University of Liège, Liège, Belgium. Pamela Fernandez is a PhD student in the Department of Botany, University of Otago, New Zealand.

Image by Lynn Lee

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Prof. Jason Hall-Spencer is a Professor of Marine Biology at the University of Plymouth, UK, Editor-in-Chief of Regional Studies in Marine Science, a UK Government Scientific Advisor on Marine Conservation Zones and serves on the Ocean Acidification International Reference User Group. Dr. Juliet Brodie is a Research Phycologist at the Department of Life Sciences, Natural History Museum, London Dr. Dan Smale is a benthic marine ecologist and Research Fellow at the Marine Biological Association of the UK. Prof. Robert S. Steneck is a Professor in the structure and function of coastal marin2e ecosystems at the University of Maine, USA.