By Laurel Dykun
Today is Fibonacci Day! The day we celebrate the Fibonacci Sequence, a pattern of numbers in which each number is the sum of the two before it - 1, 1, 2, 3, 5, 8, 13 - and so on. It’s named after the Italian mathematician, Leonardo of Pisa, later known as Fibonacci. The sequence can be found in mathematics, architecture, stock-trading, and even in nature! One of the most interesting animals that has the Fibonacci Sequence in its biological design is the nautilus.
The Fibonacci spiral drawn in a rectangle (right) and Leonardo of Pisa (left)
Image credit: Stefano Bianchetti via Getty Images
Meet the Nautilus
Nautiluses are marine molluscs of the cephalopod family, think squid with its ‘shell’ on the outside! They are a link to the past and have been around for over 480 million years, swimming the ocean depths before even dinosaurs were around. Today, nautiluses are native to tropical Pacific waters. Unlike other cephalopods like squid or octopus, nautiluses have very poor eyesight, only able to sense how light or dark their surroundings are. Instead, they rely on their strong sense of smell to find food and potential mates.
A chambered nautilus (Nautilus pompilius) Image credit: Monterey Bay Aquarium
To protect itself from predators, the nautilus can close itself completely inside its shell by shimmying inside and shutting an exterior ‘door’ called an operculum. In turn, they are able to hunt small fish and crustaceans by using jet propulsion to move around the water column, and by using their sticky tentacles (they can have over 90!) to grab onto their meal. Once caught, the nautilus uses their beak-like mouth to chow down.
A crusty/fuzzy nautilus (Allonautilus scrobiculatus) Image credit: Peter Ward
Cool! But, Where is the Fibonacci Sequence?
Were you able to spot it? It’s actually seen in the nautilus’ shell! The spiral curve of the shell follows the pattern of a spiral drawn in the Fibonacci rectangle. This type of spiral is known as a logarithmic spiral and the nautilus is a prime example of its use in nature.
Image credit: Math Images
Nautilus shells are coveted for their beautiful appearance as well as the mother-of-pearl substance that lines the inside of it. Since these animals mature late and don’t produce many offspring at a time, shell collecting can mean a significant decline in nautilus populations. Because of this, many organizations stopped selling nautilus shells. And in 2017, the chambered nautilus, which is particularly collected for its shell pattern, was listed as threatened under the Endangered Species Act.
By Sarah Holleran
This past season at the Touch Tank Hut, we welcomed a new animal we haven't had before; a maned nudibranch (Aeolidia papillosa)! Let's take some time to learn about this fin-tastic animal and why we at Back to the Sea think it is so claw-some.
Touch Tank Hut's maned nudibranch out for a stroll
Nudibranchs (pronounced NEW-dee-bronk)
Many visitors at the Touch Tank Hut, including myself, are intrigued by the nudibranch, commonly known as the sea slug. These animals are soft-bodied, shell-less marine molluscs. You will often see our nudibranch at the bottom of our tanks, cruising over sand and rocks.
Nudibranchs can be found at the bottom of shallow waters in all of the world's oceans, feeding on other invertebrates, particularly sea anemones. They feed using their radula, which is comparable to a spike-y tongue. While eating sea anemones, nudibranchs also soak up their prey's pigment into their tissue, which allows them to camouflage from predators. Nematocysts, or 'stinging cells' are a common feature on sea anemones and they are ingested by nudibranchs and used for defence purposes. They can be found on the outgrowths on nudibranchs called "cerata".
Up close and personal with our maned nudibranch
Nudibranchs, just like snails, are hermaphrodites, which means they have both male and female reproductive organs. For nudibranchs to reproduce, they can mate with any other mature nudibranch that is the same species as them. While doing a dance-like courtship, sperm is exchanged from both partners where it is stored until the eggs are ready for fertilization,. The eggs are then laid by both nudibranchs in a unique spiral formation.
Shortly after we obtained our lovely nudibranch, it laid eggs in our tank. At first, they were a big surprise to staff members as we had never seen anything like this in our tanks before. After doing some research, we found out that our nudibranch had laid eggs around our tank. It was exciting to show visitors and volunteers, since many people have never seen a nudibranch in real life before, let alone nudibranch eggs (me including)!
Nudibranch eggs next to a periwinkle at the Touch Tank Hut
Nudibranchs have another extremely fascinating thing about them - they are strong communicators! Just like snails, nudibranchs leave a trail behind them as they crawl along the ocean floor (or our touch tank). The trail they leave behind is filled with chemicals and nudibranchs use this to communicate with others. The trail can tell other nudibranchs about a potential danger, or help to attract a potential partner.
When it comes time to finding their food or a mate, nudibranchs use their rhinophores which are sensory organs or tentacles found on the back of the head or neck. These are also found in animals such as sea hares.
Nudibranch sliding down the tank glass
Sea it Yourself!
As you can see, nudibranchs are amazing marine animals and we were so happy to have one living at the Touch Tank Hut for the 2022 season. You might even be able to see one for yourself in shallow area between kelp fronds! Keep your eyes on the water!
by Kaitlin Burek
“I spy, with my little eye, something that is green” is a difficult prompt at the best of times but is especially difficult on St. Patrick’s Day. If asked, my guesses would be:
1.The dog bed in my living room
2.The apples in my fruit bowl
3.The green algae in my vase of tulips
In fact, green algae (Chlorophyta) would almost always be one of my guesses as you can “spy it” everywhere: lakes, rivers, ponds, oceans, soils, snow, lichens. The diversity in habitats lends itself to a wide diversity of green algae species. Estimates suggest there are between than 7,000-10,000 species worldwide making green algae the most diverse of the algal groups (catch up on Rhodophyta/red algae and Phaeophyta/brown algae)!
Check out some examples of green algae species below.
Oyster Thief (Codium fragile)
Sea Lettuce (Ulva lactuca)
Mermaid’s Tresses (Spirogyra)
All photo credits: Kaitlin Burek
Although green algae can be a nuisance to some – coating docks, clogging filters, stinking-up shorelines, creating blooms – it should be celebrated by all. Green algae serves as a vital food source for many aquatic organisms (e.g., snails, turtles) and creates a lot of the oxygen we breathe.
Not only that, it also serves as a great St. Patrick’s Day challenge:
“I spy, with my little eye, green algae”
by Xinya Calhoun
This past September marked my first time volunteering for the Back to the Sea Society. It also marked the first ever public Animal Release Party - and what a turnout! So many families and friends came out to the beach at Point Pleasant Park to give our sea creatures some love and say goodbye to them one last time. It was an amazing experience that I’m sure will live on in everyone’s memories for years to come!
Tons of families and friends came to Point Pleasant Park for the first Animal Release Party!
All Photo Credits: Julie Balasalle
As the Touch Tank Hut season ends each year, the animals have to say farewell to their summer home and return to the ocean. In 2021, we decided to give them an event that everyone could celebrate! Magali (Back to the Sea's Executive Director) and I spent almost an hour carefully packing up all the animals from the 4 tanks - crabs, sea stars, snails, anemones, you name it! We moved them from the tanks into bags of water and then into coolers so they stayed cool and comfy during the trip from the Touch Tank Hut to Point Pleasant Park.
Our awesome staff and volunteers getting ready for the party!
At the beach, we met with other Back to the Sea staff and volunteers. We had lots to do to set up, so it was great to have so many helping hands. Everyone pitched in to unpack, prepare the shell painting station, and get the animals ready to be handed out. Once people began to arrive, the party officially started!
Each participant filled their reusable container with some water from the beach, and then lined up to get some animals! When an animal was chosen to be released, we made a note of it - it was important to keep track of each animal to make sure they all safely got to the ocean. Participants got to touch and hold the animals, and often got to learn some fun facts about them! Then the animals were put in their container and carried to the ocean for the participant to say a final goodbye and release them into the water. Though most of our species were intertidal and were content to be set free in the shallows directly by our participants, there were some animals (our moon snail Otis, for example) who needed to go a bit deeper to be happy. We had two brave snorkelers and an amazing diver swimming in the chilly waters to help make sure those species got far enough away from shore.
A family getting their first animal - a sea star!
We had so many animals to go around that many participants came back after letting their first one go so they could help release even more! Many kids also enjoyed the oyster shell painting station.
Releasing animals back into the water!
This animal release party is unlike anything I’d ever done before. It was hours of learning, sharing, and experiencing new things about marine animals while having lots of fun at the beach. I loved every second of it, and I hope that every visitor had as much fun as I did!
As we settle into winter here in Nova Scotia, I often find it hard to believe that our grey, frozen province can be the same place it was during the sunny summer months. It’s on these chilly November days that I like to look back to the time of sunshine – so what better time than now to reminisce about the Back to the Sea Society’s Touch Tank Hut season!
This summer was a big one for the Touch Tank Hut building. After being closed for the entirety of the previous season due to COVID-19 and being moved across the parking lot of Alderney Landing, the Back to the Sea staff had a whale of a time giving the building some much needed TLC. Watching the Touch Tank Hut come together was truly an incredible sight! Once the building was in back in order and our animals collected, we knew we were officially ready to welcome our visitors.
We had to make sure that the outside was looking as good as the inside!
It’s amazing how much stuff can fit into a one-room building! Thankfully we were able to sort it all.
Just your average day at the Touch Tank Hut!
Speaking of visitors, we were so happy to welcome every single one of the 1,681 people who came through our doors this summer! People young and old were able to experience not only the Touch Tank Hut’s animals, but also the outdoor programming we developed this summer season. We loved being able to take visitors outside to paint shells, learn about coastal geology, make mini scuba divers, and clean up oil spills! Outdoor programming was a new adventure for us, and one we’re very happy to have done.
The Touch Tank Hut is for everybody, no matter how small!
Shell we Paint?! was definitely our most popular program! We loved seeing everybody’s creative sides as they painted their oyster shells.
Our work didn’t just stay at the Touch Tank Hut, however. Our interpreters not only visited summer camps throughout the season, but we also ran Tidal Trekkers, the intertidal exploration program that we started as a COVID-19 pivot but proved so popular we had to bring it back! I had some of the best moments of my summer splashing through the shallow waters of the North West Arm and McCormacks Beach alongside curious visitors, finding the intertidal species I cared for every day at the Touch Tank Hut in the wild.
It was awesome to be able to take our critters to summer camps!
We’re so happy that you all enjoyed Tidal Trekkers enough to have us bring it back!
Another reason the Touch Tank Hut had such a great season is due to our amazing staff! Back to the Sea was able to hire 5 staff this summer, including our Executive Director Magali Grégoire, Animal Care Lead Sarah Holleran, Volunteer Coordinator Maka Ngulube, Interpreter Lindsay Wamboldt, and myself, the Communications Coordinator. This amazing group of staff truly made the summer, and I’m so happy I got to work with all of them. Ladies, if you’re reading this: cheers to an awesome season!
The dream team! From left to right: Lindsey, Maka, Magali, Sarah, and Sarah.
Even though it’s cold and grey outside right now, the memories of this summer at the Touch Tank Hut serve to remind me that someday, in however many months, the sun will be shining and the Touch Tank Hut will be open once more. Until then, however, memories will have to do!
With an estimated one million species of animal living in the ocean, the diversity of ocean life is truly amazing! While most of us might think about sea turtles, dolphins or the biggest sea creature of all, the blue whale, as our favourite underwater wonder, not every species in the ocean is quite so… photogenic. Most of the spookiest sea creatures live deep beneath the ocean surface, where the sunlight barely reaches. This environment houses some of the most interesting and ugliest(!) animals that have only recently been discovered by scientists due to the remarkable conditions where they exist and thrive.
This spooky season, we want to share with you some of the spookiest sea creatures! Be brave and dive into our top ten list!
Coffinfish, colloquially known around Australia (where they are most commonly found) as Sea Toads, are benthic (bottom-dwelling) fish with the ability to use their fins to walk along the seafloor! They are ambush predators, whose facial expressions typically look really sad, because of the shape of their mouths. However, they are able to inflate their body with water which allows them to hold their breath for up to four minutes!! This is supposedly so that they can conserve energy when food on the ocean floor is scarce. And when they do… they look kind of like a cute balloon?!
(Photo credit: National Geographic)
9. Sarcastic Fringehead
Although completely harmless to humans unless provoked (they have been known to threaten scuba divers who get too close…), the Sarcastic Fringehead is well known for opening its huge mouth to fend off other ocean-dwelling critters when provoked or agitated. They live in burrows or tube-like structures created by other animals, such as burrowing clams or snail shells. Their specifically-designed jaws fan out to the side when they open their mouths, which makes them appear much larger and more intimidating. If one Sarcastic Fringehead challenges another, the two will “kiss” by aggressively pressing their open mouths against each other until one finally gives up and swims away!
This deep sea fish is transparent and has the ability to move its eyes 360 degrees so they can see what’s going on (and what’s for dinner) even when it’s behind them! Scientists only fully discovered this species in 2009, when they identified that their eyes can fully rotate inside of their head. Another quirky trait of the Barreleye is that it engulfs its prey fully! The Barreleye, like many species on this spooky list, lives deep in the ocean where there is hardly any light, so their specially designed eyes allow them to see even in almost complete darkness.
7. Vampire Squid
Unlike other squid (which can be surprisingly aggressive as tiny sea critters go!), Vampire Squid are surprisingly docile (no, they don’t suck the blood of their prey!). Vampire Squid actually feast mainly on “marine snow”, decaying organic material that falls down to the ocean floor. The spookiest feature of the Vampire Squid is its strange appearance, notably it’s umbrella-like tentacles!
6. Goblin Shark
You guessed it, these guys are ugly. Nonetheless, they use their impressive ugliness to their advantage; they use their elongated, flattened snout to seek out their prey with specialized sensing organs to sense electric fields in the darkness of the deep ocean, and they can extend their jaw the entire length of their snout to catch their prey (mainly squid, fish and crustaceans) with their 50 thin, sharp teeth! Thankfully they only grow to be 8-11 inches long!
(Photo credit: Diane Bray, Museum Victoria)
5. Northern Stargazer
Only found in the eastern United States, this frightening fish burrows itself in the sand to camouflage and can use its side fins as shovels to quickly burrow and hide beneath the sand. When unsuspecting prey comes near, the stargazer has a special organ on its head that can deliver an electric shock that stuns and confuses the prey and electrically shocks it into submission. Seems like not only is this guy pretty painful to look at, but might be pretty painful to encounter on the bottom of the ocean...
(Photo: Huffington Post)
4. Deep Sea Anglerfish
Yet another deep-sea carnivore, this anglerfish, also known as the humpback anglerfish, has to be one of the ugliest and spookiest creatures on the planet! Most famous for the bioluminescent growth on their heads, which lures their prey towards them, and to their death, deep in the darkness of the ocean. This lure is filled with bacteria, which the fish use to make their own light. They use a muscular flap of skin to either expose or hide the glowing lure. Pulsing the light and slowly moving it back and forth attracts all kinds of prey. Creepy, right? Not to mention their razor sharp, translucent teeth and their dead-looking eyes...
3. “Flying Spaghetti Monster” Bathyphysa conifer
Belonging to the Siphonophores, a group of animals including corals and jellyfish, is probably one of the weirdest creatures floating around in the ocean; first captured on video by oil and gas workers in 2015, at around 1220m depth. It has been nicknamed the “flying spaghetti monster” for its white, noodle-like appearance. Perhaps the quirkiest fact about these guys is that Siphonophores actually clone themselves in order to grow! Instead of a single body, one siphonophore is a whole tightly knit colony of many organisms, sometimes several thousands!
(Photo: National Oceanography Centre)
2. Skeletal Jellyfish
Also known as the crystal jellyfish, this ghostly, translucent critter can give off a green-blue glow when provoked or disturbed, due to the 100 or more tiny, light-producing organs that surround its outer bell. Glow in the dark and a skeleton costume? This guy is permanently embracing spooky season down there on the ocean floor!
(Photo: Hiroya Minakuchi)
1. Ghost Fish
Perhaps not as terrifying as some of the others, but by far my favourite spooky sea creature is this little guy; the ghost fish! Spotted alive and swimming for the very first time by a team of NOAA research scientists in 2016, we are still learning all about the ghost fish, which was seen swimming in the Mariana Trench at around 2500 m depth!! With translucent, scale-less skin and small colourless eyes, the ghost fish is undeniably bizarre and gives me perfect spooky season vibes!
(Photo: Weather Channel)
When most individuals “see red”, they are getting angry. When I “see red”, I am getting excited because I probably just spotted red algae (Rhodophyta)!
Unlike the brown algal species described here, red algae contains a pigment called phycoerythin which absorbs blue light and reflects – you guessed it – red light. The more phycoerythin a species has, the redder it appears. What local, Nova Scotian red algae species below do you think has the most phycoerythin?
Not only does the colour differ, but there are other morphological (or the way something looks) differences between these four red algae species. You may have noticed, for example, that Corallina looks hard and articulated whereas Porphya looks soft and sheet-like. Perhaps it was the ooey-gooey, worm-like Nemalion that first caught your eye or the branching Chondrus. Whatever it was, I am sure you’d agree that there is a lot of morphological (there’s that word again) variation between these four species. Now, what would you say if I told you there are more than 6,000 species of red algae?
Although there are morphological differences galore amongst red algae, there are also differences in how species are used by us! Would you believe me if I told you certain Corallina species are dried and used as a bone-forming material? It’s true! Chondrus crispus’s use is equally mind-blowing: did you know that it is harvested and used in Jell-O, ice cream, and vegan gelatin? It’s true! What about Porphya? It’s true that Porhyra is used in sushi! What about Nemalion, did you know it is harvested by aliens to make spaghetti? Okay, maybe that last one isn’t true.
Regardless of what it looks like or what we use it for, I hope that you get excited the next time you “see red”.
Tune in next time for when we explore green algae!
Imagine a motorcycle revving through your house while you get ready for school, make a meal, or talk to your family. That motorcycle would be loud, kick up dirt everywhere, and make it difficult to do the things you normally do. No one signs up for that!
That is a taste of what marine creatures in the Halifax Harbour have been experiencing for decades. Big container ships, recreational boats, and ferries drive through their living rooms, making lots of noise and polluting their space.
Fortunately, the Halifax Harbour will be changing soon! However, before we talk about the good things coming our way, we need to talk about why things need to change – we need to talk about how animals in the Halifax Harbour are affected by noise pollution.
Halifax Harbour on a still morning (image credit: Charlotte Craig)
Whales are heavily impacted by boat noise, because they use echolocation to find their food and move around the ocean. Echolocation is when animals like whales and dolphins send out sounds in the water, and listen for those sounds to echo back to them, helping them figure out what is around them. While whales are rare visitors to the Harbour, some more common creatures are affected by noise, too.
Animals that you see in the Touch Tank Hut like crabs and urchins can also be affected by noise. Noise pollution can reduce all marine creature’s ability to communicate, navigate, locate prey, avoid predators, and find mates. Ecological acts that are key to ocean health that are performed by invertebrates, such as water filtration and mixing sediment layers, are also negatively affected by noise. Overall, noise stresses animals out and it stops them from doing all the things that they normally would.
Boats can also cause silt (ocean floor dirt) to be turned up which can make moving around very tricky. Boats can also leave behind unwanted fuel and other pollutants while they move through the water.
Thankfully, our sea friends will soon be catching a small break. Electric ferries are coming to the Halifax Harbour starting in 2022. Electric ferries are quieter and don’t use gas.
A Halifax Harbour ferry (image credit: Discover Halifax)
The new ferries will run on a new route from the Halifax terminal to a new terminal in Mill Cove. While it is only a small step in the right direction, hopefully it will lead to the province adopting more electric ferries and other transportation. Maybe one day, the Halifax-Alderney route will be electric, and the Touch Tank Hut residents will be spared the noise.
Just as we must wash our hands and keep our voice down in the Touch Tank Hut, it’s about time we start keeping the water clean and quiet for out ocean buddies in the Harbour!
June 16th is World Sea Turtle Day! To celebrate, let's talk about a sea turtle that’s a bit closer to home than you may have realized.
Leatherback swimmin’ in the sea!
Photo credit: Jason Isley - Scubazoo/Science Faction/Corbis
Canadian Sea Turtles
When you picture a sea turtle habitat, I bet you’re picturing a lush tropical beach with crystal clear turquoise water. That’s not incorrect! We can find many different sea turtle species in the tropics. However, there is one special species that likes to visit Nova Scotia’s waters on an annual basis. Welcome to the wonderful world of the leatherback sea turtle!
The presence of leatherback sea turtles in Nova Scotia is a relatively new finding in the scientific world, although fishermen all across Atlantic Canada reported sightings of these turtles long before the first scientific article was published.
Named after the thick skin that covers their shells, leatherback sea turtles visit Atlantic Canada and the North Atlantic ocean as part of their migration route. They can be spotted in Atlantic Canadian waters during the summer months, and then during the fall they begin their journey back down to the tropics to mate and nest.
Leatherbacks are Super Cool
Not only is it awesome that Canada has its own sea turtle species, but we actually have (in my opinion) the most fin-tastic sea turtle! Although there are many reasons as to why the leatherback is so incredible, I’m going to highlight three of my favourite reasons below.
Size comparison of all seven currently living species of sea turtle, and one extinct species.
Photo credit: Smithsonian
Not many people realize just how big sea turtles are. Green sea turtles, which are a popular tropical sea turtle species and sometimes found in Atlantic Canada, are typically 3 to 4 feet long and weigh over 300 pounds. This is similar to the size of a baby elephant!
However, Green sea turtles have nothing on leatherback turtles. Leatherback sea turtles are actually one of the largest reptiles on earth! They can reach over 2 meters (6 feet) in length and weigh over 2000 pounds. The only reptile to come close to the size of a leatherback sea turtles is the salt water crocodile!
What They Eat
Leatherback eating jellyfish in Atlantic Canada
Photo credit: Lorne Bonnell from CBC news
Leatherback turtles do not have a very diverse diet. In fact, they mainly only eat one thing. Based on how big they are, be you may think they eat huge fish or full lobsters – but the reality is a bit more strange!
Leatherback sea turtles follow currents from the tropics all the way to Nova Scotia to find one thing: Jellyfish!
You read that right, these massive turtles only eat jellyfish and other jellyfish-like animals like tunicates and ctenophores. A single jellyfish doesn’t provide very much nutritional value, so leatherback sea turtles will eat up to their body weight in jellyfish every day! Think about how many more jellyfish would fill our ocean if we didn’t have turtles eating 2000 pounds of jellyfish daily. Thank you leatherbacks!
The Pink Spot
Leatherback sea turtle with visible pink spot on the top of its head!
Photo credit: S. Bonizzoni
The last cool leatherback fact I’m going to highlight is their pink spots. Leatherbacks have a very special characteristic that helps us identify them from afar (it comes in handy when trying to spot a leatherback from a boat to tag!). On the back of every leatherbacks head is a pink dot. This is actually an exposed part of their brain!
Although science is still debating what the actual function of this pink spot is it is theorized it helps identify light and may play a role in leatherback migration! Perhaps a built in GPS?
Turtles in Danger
Leatherback in Nova Scotia
Photo credit: Canadian Sea Turtle Network
Unfortunately, similar to other sea turtles species, leatherback sea turtles population numbers have declined, and the species is currently listed as vulnerable on the IUCN Red List. These turtles face many threats including fisheries bycatch, habitat loss, and plastic pollution.
On the plus side, if you’re looking to help leatherbacks you have already have helped just by reading this far into my blog post! Not many people realize how cool leatherback sea turtles are and that they are part of our maritime family. The more people that realize these turtles share our waters and how amazing they are, the better chance the turtles will have for future protection measures.
If you are interested in doing more for leatherback sea turtles check out the Canadian Sea Turtle Network who are doing great work for sea turtles in Canada. If you’re looking for even more leatherback content checkout this fact page by NOAA Fisheries.
Feel free to ask questions about leatherbacks in the comments!
Lauren is a part of the Communications Committee for Back to the Sea and just recently finished her undergraduate degree in marine biology and sustainability at Dalhousie. Lauren is extremely passionate about ocean conservation and loves to share this passion by educating everyone around her on the wacky and amazing species that call the ocean home!
June 8th is World Oceans Day—or, depending on who you ask, World Ocean Day. Why is there a debate? Surely, in an age where thousands of satellites orbit the Earth, we know how many oceans there are? But it turns out, it’s a little more complicated.
The ocean as seen from a beach
Let’s start close to home. If you’ve visited Back to the Sea’s Touch Tank Hut at the Dartmouth Waterfront, then you’ve probably seen the ocean while you’re there—it’s the big blue thing right in front of you! You can’t miss it. Here in Nova Scotia, we live next to the Atlantic Ocean. Canada borders three different oceans: to the west is the Pacific, and up north is the Arctic. But how many oceans are there in the world?
Halifax harbour at sunset, showing the Macdonald bridge
If you listen to Eurythmics or are a pirate from the olden-times, you might have heard that there are “seven seas”. What exactly are they? That rather depends on who you ask, and when.
First of all, even though “seas” and “oceans” are often used interchangeably, geographers make a distinction: seas are smaller and are often partially enclosed by land. Secondly, many different cultures and eras used “seven seas” as a catch-all term for the waters that extended towards the limits of their known world. For the ancient Persians, the “seven seas” were actually rivers and in Central Asia. It wasn’t until Europeans began exploring the world that the seven seas came to include the oceans as we know them today.
Map showing all of the world's oceans
So, let’s count the oceans and see if they add up to seven. We already know three of them: the Arctic, the Pacific, and the Atlantic. The fourth ocean is the Indian Ocean, located between Africa, Asia, and Australia. And that’s where the list ends—for some people. Others recognize a fifth ocean surrounding Antarctica called the Southern Ocean. In 2000, the International Hydrological Society—the global authority on nautical charts—proposed a new boundary for the Southern Ocean. But it was never ratified by all the member states, so its “official” existence remains up in the air, and some maps don’t include it.
As the previous example makes clear, the reasons why we create boundaries between oceans can sometimes be a bit arbitrary. It’s hard to say exactly where one ocean ends and another one begins. Even though we talk about different oceans and seas, all the water in the ocean is connected, although it can take a very long time--up to 1,000 years—for a parcel of water to make its way from end of the ocean to another. That’s why some people think we should call it World Ocean Day: to remind ourselves that there’s only one big, interconnected ocean that we’re a part of, too.
The ocean is complicated—and people make it even more complicated. No matter which way you to choose to celebrate, Ocean Day or Oceans Day, I hope you take some time today to think about the incredible waters that make up 71 percent of our planet and how we can protect them.