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The gigantic forests you won’t find on land - Luka Seamus Wright and Salomé Buglass
The gigantic forests you won’t find on land - Luka Seamus Wright and Salomé Buglass
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Subtitles (141)
0:00
[music]
0:07
>> In [music] the mid-20th century, the
0:10
first scuba technology allowed deep-sea
0:13
divers in the Mediterranean to reach
0:15
previously impossible [music]
0:17
depths.
0:18
And after descending into the mesophotic
0:20
zone, an ocean region spanning 30 to 150
0:25
m, these aquanauts [music] made a
0:27
remarkable discovery.
0:30
Up to 90 m below the surface, where
0:33
sometimes only 0.1%
0:35
of surface sunlight can reach, they
0:38
found a forest of huge kelps, over twice
0:42
the size of a giraffe.
0:46
Today, kelps are known to be the largest
0:48
marine plants, and there had already
0:51
been talk of such giants being pulled up
0:53
from enormous depths in the late 19th
0:56
century.
0:58
But following the Mediterranean
0:59
discovery,
1:01
fishermen, naval officers, and
1:03
scientists began dredging up more
1:06
massive [music] mesophotic kelps in the
1:08
Philippine Sea and off the coasts of
1:11
Brazil, Australia, and North America.
1:15
There were even claims of plants this
1:17
large being brought up from as deep as
1:19
150 m. That's deeper than the Great
1:23
Pyramid [music] of Giza is tall.
1:27
These forests should be impossible. Like
1:30
any other plant, kelps require light to
1:32
grow.
1:34
Yet these [music] specimens grow as
1:35
large as and often even larger than
1:39
their shallow counterparts. [music]
1:41
All with less light than they should
1:43
require just to stay alive.
1:46
Then again, the mesophotic is the border
1:49
between two worlds. One where life
1:52
depends on the energy provided by
1:53
sunlight, and another where life has
1:57
learned to live in darkness.
2:00
So, how have these large,
2:02
light-dependent organisms
2:04
>> [music]
2:04
>> adapted to thrive at such depths?
2:08
Researchers are still investigating the
2:10
answer to this question, but they do
2:12
have theories. Mesophotic kelps [music]
2:15
photosynthesize more efficiently than
2:17
their shallow counterparts,
2:19
and some have suggested this might be
2:21
due to having very large surface area
2:24
relative to biomass, [music]
2:26
which allows deep kelps to maximize
2:28
light harvesting and minimize
2:31
respiration.
2:32
By taking these adaptations into
2:34
account, existing research still
2:36
suggests that deep kelp forests don't
2:39
photosynthesize enough to sustain
2:41
[music] their growth and respiration,
2:44
even at peak sunlight.
2:46
So, the real key to their success might
2:49
be thriftiness.
2:51
Photosynthesis is dependent on four main
2:54
ingredients: sunlight, water, nutrients,
2:57
[music]
2:58
and CO2.
3:00
And while sunlight is severely limited,
3:02
the deep ocean is full of water and
3:04
nutrients. It's also full [music] of
3:07
CO2. However, most marine CO2 is in a
3:11
bicarbonate form that requires lots of
3:14
energy to convert.
3:16
>> [music]
3:16
>> Most aquatic plants have evolved
3:18
mechanisms to handle this
3:20
energy-intensive process, but deep kelps
3:23
take the easy way out. Since their
3:26
deeper waters have more CO2, which
3:28
doesn't need to be converted, they get
3:30
their fill through low-energy passive
3:33
diffusion.
3:35
Mesophotic kelps also save energy by not
3:37
having to produce molecular sunscreen,
3:40
which plants typically need to avoid
3:42
damage from excess sunlight.
3:45
These aren't the only tricks deep kelps
3:47
use to conserve energy. In the darker
3:50
winter months, these plants suppress
3:53
their respiration and subsist on the
3:55
carbon reserves they stocked up over the
3:58
summer.
3:59
This adaptation is similar to how
4:01
shallow polar kelp forests survive
4:03
months of darkness.
4:06
But while mesophotic kelp's access to
4:08
sunlight also changes with the seasons,
4:10
temperature is fairly consistent in the
4:13
deep ocean. So, they don't have to
4:15
contend with extreme temperature swings.
4:18
This lets these forests act as a climate
4:20
[music] refuge, providing a stable home
4:23
for species in shallower zones fleeing
4:26
marine heat waves.
4:28
Kelps also draw down some of the
4:30
atmospheric CO2 that causes climate
4:32
change. In [music] fact, kelp detritus
4:35
will keep photosynthesizing and drawing
4:37
down CO2 as it drifts to the ocean
4:40
floor. The researchers are still
4:42
investigating its exact [music] impact
4:45
on the carbon cycle.
4:47
There's still lots to be learned about
4:49
the ocean's hidden forests. In fact, we
4:52
still don't even know how much of the
4:54
seafloor they cover. Since most kelp
4:56
forests are invisible to satellites,
4:59
researchers need to use [music]
5:00
cutting-edge underwater robots to find
5:03
the answer.
5:05
These remotely operated vehicles, ROVs,
5:09
can explore and film depths far beyond
5:12
the reach of humans.
5:13
And with their help, marine biologists
5:16
have already found new kelp forests,
5:19
such as those off the tropical coast of
5:21
the Galapagos Islands.
5:23
But given how many surprises these
5:25
impossible forests have already
5:27
revealed, who knows what other mysteries
5:30
they're hiding.
5:32
Ready to keep learning? Watch these
5:34
videos to either challenge what you
5:35
think you know or learn more about what
5:38
you don't. Subscribe and stay curious.
5:47
>> [music]
5:50
>> Mhm.
