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Do fish sleep? And other ocean questions answered.

This series will answer some of the most common questions about animals and habitats. Today, it is all about oceans and those that call it home.

How many oceans are there?

5 - Arctic, Atlantic, Indian, Pacific and Southern.

Why are oceans important?

Oceans are a significant ecosystem, accounting for 2/3 of the Earth's surface. Oceans help to regulate the climate by producing 70% of our oxygen, absorbing CO2 and regulating temperature. It provides food, resources and jobs, contributing to the global economy.

How many animals are in the ocean?

In the 2021 census, The World Register of Marine Species reported 240,000 known species in the ocean. However, with 80% of our oceans yet to be explored, it is estimated that 91% of ocean species are yet to be classified.

Which ocean animals are endangered?

The U.S. Endangered Species Act reports that the global count is approx. 2270 marine species classed as threatened or endangered. This includes the vaquita, blue whale, Hawaiian monk seal, hawksbill turtle and white shark.

How does climate change affect the ocean animals?

We've spoken about how the ocean helps to regulate our temperature on land, but what happens when climate change makes the temperature too high? Coral reefs are susceptible to the effects of global warming - a 1.5°C increase could destroy up to 90% of coral reefs, and 2% could lead to complete loss. Higher temperatures make oceans more acidic, and these factors encourage coral to grow algae (see coral bleaching), which puts pressure on the ecosystem. Acidity also damages the shells of sea molluscs and crustaceans and disrupts the food chain.

Climate change reduces the oxygen supply in the water. As the ocean's temperature increases, the amount of available oxygen decreases (hot water holds less oxygen), causing an increased demand for oxygen for sea creatures. Deoxygenation leads to habitat compression and an increase in disease.

Temperature and current changes affect migration patterns, breeding and the health of sea creatures. For example, the rising sea levels are estimated to flood 2,835 sea turtle nest locations across seven breeding grounds from 2010 to 2100 under moderate and high greenhouse gas emission scenarios.

Can sea animals drown?

Marine mammals can drown. The International Marine Mammal Project reports that the leading cause of drowning in marine mammals is caused by entanglement from plastic fishing gear, lines and nets.

On the other hand, fish technically cannot drown as they breathe through their gills rather than inhale. However, they can suffocate if oxygen levels aren't sufficient or their gills are damaged (see Discover Wildlife for more information).

What is the biggest animal in the ocean?

The blue whale is the largest animal in existence.

Can fish that live in oceans see in the dark?

Deep sea fish have adapted to life with little light. While some have evolved to have large eyes with more rods, detecting more light, others produce light (bioluminescence). Those with little or no sight ‘see’ with their other adaptations, such as light-sensitive cells on their heads or mechanoreceptors that detect pressure change and vibrations in the water.

What are ocean animal adaptations?

There are so many! We've chosen 5 animals with pretty cool adaptations below:

Peacock mantis shrimp: They are not only extremely clever with incomparable eyesight but also have the most powerful punch in the animal kingdom.

Clownfish: Clownfish can change gender. When clownfish are born, they are gender-neutral - they are hermaphrodites and will become male in the juvenile stage. The clownfish school is run by a dominant female, the largest of the group. The second-largest is the dominant male. If something happened to the dominant female, the dominant male would switch genders. These fish are monogamous - if two males become partners, the more dominant will become female to mate.

Blue dragon: This gorgeous sea slug feeds on the deadly Portuguese man-o’-war (and other venomous creatures), stores the toxins and releases them when threatened.

Notothenioidei: Notothenioidei is a suborder found around the Antarctic. To survive the extreme cold, they produce antifreeze proteins.

Mimic octopus: The mimic octopus is the master shapeshifter; it can impersonate a plethora of different sea animals by changing colour, shape and behaviour.

And lastly, do fish sleep?

Yes! Some fish slow their breathing and lie motionless. Others have to keep moving to breathe; it is thought that these creatures sleep with half their brain at a time - just like dolphins.

COMING SOON: ZooLab's Ocean's workshop will be available for booking in September 2023. Keep an eye out for more details.

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