Have you ever thought of the important role sea sponges play in the world’s oceans? They are in fact important members of coral reefs all over the planet.
They keep a healthy nitrogen level; this makes it available for other creatures in the reef, such as fish. Sponges are responsible for recycling the coral into sand – this ensures that the delicate balance between the growth and erosion of the reef is maintained.
Yet, the effects of global warming are threatening to disrupt this critical equilibrium. The threat is due specifically to what is known as ocean acidification and ocean surface temperature. These two factors are a result of the rise of carbon dioxide in the atmosphere and the resulting rise in the earth’s temperature.
From Coral to Sand
If you have ever seen a coral reef, its majestic beauty has very likely been captivating. Their importance to the oceans and the world can’t be overstated.
Coral reefs contain an astounding diversity of life; its surface is made of polyps (also known as stony coral), which form a living layer covering the coral.
These polyps (which are distant relatives of anemone and jellyfish) extract calcium from the water; converting it to Calcium Carbonate, which is then deposited onto the coral contributing to its growth. These limestone deposits form the supporting structure of the coral (NOAA).
Sea sponges are one of a number of creatures in the reef responsible for a process known as bioerosion. Essentially, the sponge excavates the coral through crevices which have already been formed by other bioeroding organisms. The ingested limestone will be transformed into fine sand, which becomes an important part of the coral landscape. This sand eventually becomes part of tropical beaches.
This process helps to maintain the proper calcium carbonate levels – along with erosion it keep a proper balance between the building and destruction of the coral (The Journal of Experimental Biology 210, 91-96). Sea sponges are instrumental in maintaining the physical structure of coral reefs
Naturally, carbon dioxide is crucial for life on earth. All animals and plants have a symbiotic relationship – plants need to inhale the carbon dioxide we exhale while we need to breathe in the oxygen they let out.
This gas is also important to life on earth in another way. It is the planet’s natural blanket; in the atmosphere, it prevents much of the sun’s heat from escaping back into space – which would otherwise leave the earth too cold for life as we know it.
Carbon dioxide happens to be a bi-product of much of the fossil fuels we currently burn for our every day energy needs – 30 – 40% of it is absorbed by the oceans (Earth Eclipse). This causes one of the effects of global warming – our oceans become more acidic. As a result, sea sponges, such as the Zooxanthelate Sponge in the Great Barturier Reef, increase their rate of bioerosion.
The unfortunate outcome is a coral that’s being eroded too quickly. By the year 2,100 it is predicted that coral reef erosion can increase by 2 to 4 times (Aquatic Biology). This will disrupt the balance between coral growth and bioerosion, causing havoc to the calcium carbonate budget of the coral reef.
This means the coral’s growth will be more restricted. This could be a significant disruption to the accretion-erosion balance of the reef. With the potential to have unseen consequences for the biodiversity of the reef. Because the coral’s influence reaches the entire marine ecosystem, there will be a natural ripple effect throughout the oceans and the world as a whole.
Rise in Ocean Surface Temperature
The scientific community has been warning the public for years about the threat of rising sea levels. This ascent is made possible by the melting of polar ice and the warming of the oceans – as heat causes the water itself to expand. Ocean expansion can sink islands and speed up the erosion of shorelines – potentially displacing millions of people. The warming of the waters also lead to significant impacts below the surface.
The sea sponge depends on a symbiotic relationship between itself and the microbes that inhabit it. This relationship fails when the water temperature reaches 91.4 degrees Fahrenheit or 33 degrees Celsius (Science Alert).
By the year 2100, the oceans surface temperatures will cross this critical point on a regular basis (Science Alert). The host sponge is dependent on its relationship with the microbes for its own chemical defenses, nutrients and waste removal.
The result of this can be disastrous for the sea sponge, as it relies on the health of this relationship for its survival. The coral reef itself depends on the sponge for maintaining the proper amount of limestone, and distribution of nutrients. A disruption of this type can cause the coral to grow too slowly – if at all – causing a loss of equilibrium.
Where Are We Going
It is clear that the sea sponge is an important part of the coral reef. What affects this member of the coral community will have consequences for other creatures as well. Bioerosion keeps the coral in a healthy balance. Like all natural processes in nature, there’s a balance that has been in place for millions of years. Human activity has essentially sped up this natural process, rendering our future uncertain at best.
The experts warn us that the outcome is something we must try to avoid. Since all systems are interconnected, and we are inseparable from nature, what affects the sea sponge will have significant consequences on us all.
What We Can Do
According to climate scientists, there are steps we can take to curb the likely consequences of global warming. Sea sponges need to be protected, as their health is intricately linked to the fitness of the entire coral reef. One of the important roles they provide is called bioerosion; which regulates the growth of the coral by converting the calcium carbonate limestone to fine sand.
This process is being accelerated by the acidification of the oceans, which are absorbing the excess carbon dioxide from the atmosphere. This surplus is the result of burning of fossil fuels; which is also warming up our planet – including our oceans.
This ascent in water temperature is hindering the sea sponge’s symbiotic relationship with the microorganisms that inhabit it.
If we can transform how we meet our energy needs, then our sea sponges, and thus our coral reefs, will have a better chance – which also means our outlook will fare much better as well.
What do you think about our impact on the world’s Sea Sponges? How important do you think they are? What do you think we can do to protect them? Please leave a comment!
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