Can sea creatures adapt to climate change? | The Economist

published on July 2, 2020

Over the past century the ocean has been rapidly changing

Global water temperatures have increased

sea levels have risen

and the fundamental chemistry of the ocean has been altered

The biodiversity that appeared on this Earth

three and a half billion years ago

now are facing threat because of we the humans

A marine biologist in the Bay of Bengal

is investigating the resilience of marine life

by researching one of the planet’s greatest survivors

the horseshoe crab

They’ve outlived the dinosaurs and survived mass extinctions

Can their ability to adapt provide clues for how other ocean creatures

might evolve and survive in the face of modern-day climate change

We believe that because the horseshoe crabs have survived

they hold the information for survival

In the north-eastern part of the Indian Ocean is the Bay of Bengal

Dr Punyasloke Bhadury and his team of marine biologists

are searching for horseshoe crabs

But finding these creatures is harder than it once was

Seems to be an interesting place

where we should be able to see some horseshoe crabs

Horseshoe crabs are an example of living fossils

They’ve existed, nearly unchanged, since at least 445m years ago

long before dinosaurs

They are a keystone species

which means they play a crucial role in maintaining the health

of this coastal area

Horseshoe crabs, in sizeable numbers

can help accelerate many of the ecosystem-level processes

transfer of energy, maintaining the food web

ensuring the carbon cycling

So, therefore, they are very, very critical

But they are now on the threatened species list

Ten years ago when I started my work

looking at the horseshoe-crab population at this place

I would find a lot of horseshoe crabs

Today, I see hardly any horseshoe crabs

The team is researching what is causing the decline in population

to help build a case to make part of this coastline a marine-protected area

We are liaising with fisherfolk communities

They get hold of the horseshoe crabs, which are caught in nets or in trawlers

They pass those horseshoe crabs to us so that they can recover

They can help towards the conservation by keeping an eye

how the habitat is changing or how they are being threatened

But the team is facing many challenges

Horseshoe crabs are sought after

because of their ability to improve human health

They have a unique substance in their blood

which is used to make a chemical called limulus amoebocyte lysate

This chemical can detect trace amounts of bacterial contamination

It is used in many vaccines and to test equipment before surgical operations

As a result, the blood of horseshoe crabs

is one of the most valuable liquids on Earth

and can be worth as much as $16,000 per litre

Although they are returned to the ocean after being bled

an estimated 50,000 horseshoe crabs die in the process per year

But this isn’t the only threat they are facing

Like so many other ocean creatures

the horseshoe crabs are also being affected by overfishing

coastal pollution and habitat loss

Perhaps the greatest threat, however, comes from climate change

Over the past few hundred years

human activity has increased the concentration

of carbon dioxide in the atmosphere

This traps heat, most of which is absorbed by the ocean causing it to warm

in 2019 its mean surface temperatures were 077 degrees Celsius warmer

than during the 20th century

And in turn the sea levels have risen

The ocean also absorbs carbon dioxide from the atmosphere

changing its chemistry

These factors are affecting ocean species

Many will need to adapt or face the threat of extinction

Today, the researchers are taking water samples and sediment

from the bay to analyse back in the lab

What they find on expeditions like this

can shape their understanding of the effects of climate change

on marine life, like the horseshoe crab

We analyse different environmental parameters

to understand the health of this ecosystem

for example, charismatic species such as the horseshoe crabs

We can then start to link and understand

what kind of changes might be happening to them

The samples are analysed for acidity, temperature and microscopic algae

food for many sea creatures, including the horseshoe crab

Using this information the researchers are able to build

a more accurate picture of the biodiversity in the area

and ultimately which creatures are likely to survive

This isn’t the first time that the horseshoe crab

has had to face major climatic changes

It has survived five catastrophic mass-extinction events

But current changes to the ocean are happening much faster than ever before

Human pressure is affecting the health of the modern ocean

on a much shorter scale

Therefore, the horseshoe crabs are not finding enough time

to adapt to these changes and thus, they are becoming more vulnerable

Along the coast, the team has unearthed something unexpected

The horseshoe crabs are moving into different areas

in search of new food sources and new habitats

We are quite happy, we found two horseshoe crabs

out here in this mangrove patch

They’re looking very healthy

This is a new habitat out there within the mangroves of the Sunderbans

where they have colonised

And we’ll continue to monitor these sites very well

and get an understanding why they’re colonising these new sites

The horseshoe crabs are survival specialists

But it’s too early to tell whether this recent migration and adaptation

is a masterstroke

This is a fight-back mechanism or I would say an adaptive mechanism

I believe this is a very, very bold step the horseshoe crabs are taking

They’re going into areas where food resources are a very different nature

We have to keep studying them to understand

whether it is a wise step for them or not

I’m sure it knows what it is doing

Question is: are we allowing that animal to let that change happen

so that it survives and prospers?

The horseshoe crabs aren’t the only marine species

which are trying to adjust to climate change

For the past two decades lobsters along the coast of North America

have been slowly moving north to colder, more favourable temperatures

And researchers have discovered

that some Arctic seabirds have moved their mating season

to earlier in the year when food is more available

The hope is, that if given enough time

many marine species will be able to adapt

to the growing changes in the ocean

If we can understand what kind of adaptive strategies they have undertaken

we can then see for many of the other endangered species

how would they cope with these changes

that is happening in the global ocean

Horseshoe crabs are showing signs

that they may adapt in the face of climate change

But to give them a fighting chance

Dr Bhadury is lobbying local government

to implement more marine-protected areas along this fragile coastline

to protect and conserve these animals and the ecosystem

from overfishing, pollution and construction

Eventually in the coast of India we will declare ecologically sensitive areas

where human-induced activity will completely stop

So, that horseshoe crabs will survive, thrive

and in the process many other marine organisms will survive and thrive

So, that is the approach that we are aiming to achieve in the long run

As the ocean changes, it is unclear which species will be able to cope

But by conserving and studying one of nature’s greatest survivors

scientists like Dr Bhadury, can gain a better sense

of how other marine species might migrate, adapt and evolve in the future

Hi I’m Claire and I directed this film

If you want to learn more about some of the innovative ways

people are trying to tackle the challenges facing the ocean

then click on the link opposite

If you want to watch more of The Protectors series, then click on the other link

Please remember to subscribe, and thank you for watching

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