To ask which animal in nature is big, I believe that everyone will nominate elephants, blue whales and other creatures, but in fact, the world's largest organism looks "inconspicuous" on the surface, it is the "seagrass" that flutters with the wind.
A magical aquatic plant that can bloom in the sea
So, how did a small "grass" become the world's largest organism? What's so special about it? Why is this biggest creature also threatened? Let's take a look at which "grass" swaying with the wind is so powerful.
Vast and beautiful underwater meadows
Magical "grass"
The previously magical "seagrass song" and "seaweed dance" brought a wave of imitation, and this plant, which is very common in the ocean, suddenly became the object of everyone's attention. Of course, there are also many people who believe that the presence of seagrass actually pollutes the sea, making the clear water somewhat "ugly", so they are very disgusted with them.
However, the "seagrass army" will grow freely in the sea regardless of whether humans have opinions or not, covering a large area of the sea. The "seagrass" we are going to introduce today is located in the westernmost shark bay in Australia, where different species of seagrass grow, and as can be seen from the map, these seagrasses constitute a huge "seagrass plain".
The "Seagrass Plains" of Shark Bay
Many biologists are very interested in the seagrass here, and have traveled to various areas here to sample and try to sort out the "family tree" of the seagrass family. So they took samples at a location in 2020 and genetically tested the samples.
It was thought that these distant seagrasses were at most distant relatives, but the test results showed that the samples from 9 locations all belonged to the same seagrass, which is the "Australian neptune grass".
Specimen of Aussie neptune
Immediately after making such a special discovery, evolutionary biologist Elizabeth Sinclair began a larger study, and finally found that the vast majority of seagrass in Shark Bay behaved genetically identically, which proved that they all had the same "ancestor".
To this end, they believe that the vast neptune grass in Shark Bay should start with only one, and this small "grass" replicates itself day after day, eventually allowing the clone to occupy a large area of the seabed.
Underwater photo of The Australian Neptune grass in Shark Bay
The seagrass bed spans 180 km and covers an area of about 200 square kilometres. Presumably, it would take at least 4500 years for the first grass to spread to this extent. As a result, it is not only the largest organism in the world, but also the degree of longevity.
In this regard, researcher Elizabeth Sinclair said: "This is the largest known clone on Earth, and arguably the largest organism in the world. ”
The expanding Australian neptune grass
It is worth mentioning that in fact, all the seagrass in the world relies on cloning to reproduce, and there are such huge seagrass beds in the Mediterranean and Baltic Seas. However, there is no "polyploid seaweed" in these areas, and the Australian neptune grass in Shark Bay has long been out of the limit and has become a tetraploid organism.
This characteristic makes it possible to withstand the upheaval of the environment, and has been cloned and copied for thousands of years, making its family even larger. Therefore, for the seagrass in Shark Bay, this is essentially an evolution, not only making individuals more adaptable, but also allowing the population to reproduce.
Seagrass produces clones by extending the rhizome
However, it is the seagrass that has found the "diffusion code" in its long evolution, after becoming the world's largest organism, also faces a threat, and may even become smaller and smaller under this threat until it eventually disappears.
What kind of threat is "seagrass"
In fact, from the above discussion, it can be seen that when humans study seaweed, they will rarely target a certain tree, and even if they are sampled, they will be "blindly selected" in a wide range. And these seemingly growing, growing beds of seagrass are actually in the process of fading.
Schematic diagram of the distribution and variation of european seagrasses
From the current situation, there are 12 genera and 50 kinds of seagrass in the world, with a total area of about 0.6 × 10^6 square kilometers, equivalent to about 10% of the offshore area. Because it grows in offshore areas, it is relatively easy for humans to "census" seagrasses.
This creature itself relies on its strong cloning ability to mix in offshore waters, but since the 1980s, it has begun to fade at a rapid rate. And according to the current statistical comparison, nearly 30% of the world's seagrass beds have disappeared, and the remaining seagrass days are not good, basically facing certain threats.
Seagrass is an indispensable creature in the ocean
Humans undoubtedly play an important role in the degradation of seagrass beds. Because with the development of science and technology, human operations in the offshore are becoming more and more frequent, and many construction activities will cause damage to the seagrass bed offshore. But at that time, the human beings who only pursued profit did not care, after all, it was just a seaweed, and it was harmless to disappear.
Later, changes in the global climate made the situation of seagrass more difficult, such as the El Niño event between 1995 and 1998 that brought a lot of rain to a bay in the United States, which eventually led to excessive nitrogen input and a significant slowdown in seagrass growth in the region.
El Niño events observed in 1997
In addition, there is eutrophication of water bodies, etc., which will have a potential impact on the growth and survival of seagrass. Because many people do not care about the "small creatures" in these seas, it is difficult to detect the reaction of the seagrass bed to environmental upheavals.
However, according to the scientists' current research, seagrass has successfully proved the fact that although a small tree can be clustered together, it can have a huge impact.
Eutrophication affects the photosynthesis of plants in water
So, what is the significance of the existence of seagrass beds? Do they sway in the sea do anything to contribute to the earth?
Carbon sequestration capacity of "seagrass ecosystems"
In recent years, human beings around the world have been very troubled by the problem of global warming, because the negative effects of global warming have been highlighted and are in the process of expanding.
If in the past we could "cover our ears" when nothing happened, then now reality does not allow people to pretend to be stupid.
Schematic diagram of changes in global ground temperature
Therefore, in recent years, in addition to thinking about how to reduce carbon emissions, human beings are also looking for things in nature that have the ability to sequester carbon. For example, in order to achieve "carbon neutrality" as soon as possible, the mainland has been working hard to plant trees in these years.
According to the "Blue Carbon - The Securing Effect of Healthy Oceans on Carbon" jointly released by the United Nations Environment Programme and the World Conservation Union in 2009, the carbon sequestration function of the ocean may actually be more powerful than the solid-state ability of terrestrial organisms.
Schematic diagram of the process of marine carbon sequestration and storage
The report points out that although the biomass of marine plants is only 0.05% of that of land plants, the productivity is very high, the carbon cycle is about the same size as that of land plants, and it is one of the densest carbon sinks in the entire Earth's biosphere.
Among the marine carbon sequestration army, the most prominent performance is the seagrass we introduced today. Don't look at this guy looks very small, the daily life will only "drift with the wind", its area is nothing compared to the total area of the ocean, but the carbon sequestration ability is extremely strong.
Schematic diagram of the carbon cycle of seagrass
Studies have shown that its average carbon sequestration rate is about 21 times that of tropical rainforests, making it a veritable "small expert in carbon sequestration".
Studies by Fourqurean et al. show that the global storage of organic carbon in seagrass bed sediments is 9.8 to 19.8 Pg C (Pg = 10^15 g), which is equivalent to the sum of global mangrove and intertidal saline marsh plant sediment carbon stocks.
Comparative map of carbon sequestration capacity of coastal zone ecosystems
As can be seen from the data, the carbon sequestration capacity of seagrass beds is indeed extremely strong. And as research continues, many experts point out that seagrass plays a far more important role in carbon sinks than humans think.
In the case of Spain's Balearic Islands, seagrasses here create about 35 times the value of carbon sinks than the same area of tropical rainforest.
Therefore, many scientists have called on everyone to reduce their activities in shallow seas and avoid affecting the survival and growth of seagrasses. On the other hand, we are also stepping up research on how to artificially restore degraded seagrass beds to bring them back to life.
Transplanting eelgrass helps to restore seagrass ecosystems
However, sometimes it is difficult for humans to solve all the problems, so it is still necessary to focus on "protection". At least a seagrass bed of this magnitude like the one in Shark Bay, we can't let it fade or even disappear. It's hard to imagine how carbon dioxide levels would skyrocket if humans lost all of their seagrass.