#1504 What is a kelp forest?

What is a kelp forest? A kelp forest is a dense area of kelp in the sea. Kelp is a type of algae. They form incredibly diverse ecosystems, and they can help to clean up the sea.

Kelp are giant strands of brown algae, probably more commonly known as seaweed. They look like plants, but they are actually stramenopiles. A stramenopile is often a single-celled organism, such as slime mold. Kelp is not a single-celled organism, it is very complex, but the cells share properties with other stramenopiles, and kelp doesn’t have the vascular system that plants have. The main thing they share is that they both photosynthesize. Kelp have a strong stalk and large flat leaves that branch out from it. These leaves are how it photosynthesizes and makes its energy. Most plants are green because it is easier for them to absorb enough energy and photosynthesize, but algae are generally brown, not green. Their color comes from pigments called carotenoids. They are brown because they grow in the sea and brown is a much more effective color to absorb energy in low light conditions.

Kelp only grow in certain areas, and they grow very close together, which is why they are called kelp forests. The water temperature has to be between 6 and 14 degrees Celsius, and if they have access to a lot of sunlight and nutrients, they can grow at up to 50 cm a day. Some of the biggest varieties can reach 80 meters in length. They are so long that they become fairly heavy, and they can only stay upright because of gas-filled bladders called pneumatocysts. They do this because there is more sunlight closer to the surface. To stop the floating away, they anchor themselves to the seabed using a structure called a holdfast, which looks like a root, but isn’t a root. The holdfast cannot absorb any nutrients, it only holds the kelp down. Unless you go underwater, you have probably only ever seen the parts of the kelp that reach the surface.

Kelp forests are very special ecosystems because of the things the kelp can do and because of the habitat they provide for other animals. It is said that there is a greater variety of plants and animals in a kelp forest than anywhere else in the ocean. Kelp are so big and they grow so closely together that they create lots of hiding places and shelters for different sea life. A lot of small animals live amongst the holdfasts as well. And where a lot of animals gather, more animals gather because life begets life. There are animals that feed on the animals that live there, and animals that feed on the remains and the waste of the animals that live there. Larger animals like sea lions and whales even hide and feed in kelp forests. There are even bacteria that specialize in decomposing the kelp when it dies. Sea cucumbers, crabs, and starfish live at the bottom of kelp forests and feed on everything that falls down to them.

More than providing a wonderful home, kelp forests also clean the water around them. Kelp do two things. Firstly, they absorb carbon dioxide out of the water when they photosynthesize. Secondly, they absorb excess nitrogen out of the water. Nitrogen can get into water from many places, but a lot of it comes from fertilizer that farmers use on fields. Nitrogen is vital for plants to grow. They use it when their cells divide, and generally, extra nitrogen helps them grow more. It also extends the length of time they can grow for. Nitrogen helps plants photosynthesize more as well. Nitrogen fertilizer is common, but the rains washes it out of fields and it ends up in rivers and then the sea. Nitrogen can be toxic to fish in high quantities, but the problem is that it makes algae grow much faster than usual. If there is a lot of nitrogen, algae can go out of control and completely cover the surface of the water. When this happens, they cut out light, and they can sometimes get caught in the gills of fish. More problematic, though, is when they die. The bacteria that decompose them use enormous quantities of oxygen, and they can use all of the oxygen in an area of water, leading to dead zones that fish can’t live in. Kelp forests can help here because they absorb a lot of the nitrogen, so that they can grow. They also live longer and don’t all die at the same time, so there is not a huge removal of oxygen in the area. Kelp area a positive part of any undersea ecosystem. And this is what I learned today.

Sources

https://www.nps.gov/articles/giant-kelp.htm

https://en.wikipedia.org/wiki/Kelp_forest

https://en.wikipedia.org/wiki/Kelp

https://en.wikipedia.org/wiki/Stramenopile

https://www.montereybayaquarium.org/animals/habitats/kelp-forest

https://oceanservice.noaa.gov/facts/kelp.html

https://press.uni-mainz.de/shedding-light-on-the-brown-color-of-algae

https://southernscientificireland.com/2023/11/22/nitrogen-in-water