As we move into April, I’m sure many people are gearing up for warmer weather and all of the fun activities associated with spring. Many concerned with marine life might associate spring with whale migration or the mating season for some animals, but those with their mind on Easter egg hunting might have the right idea too! Today these two spring-related topics can cohabitate, just like eggs and marine life, because we are going to highlight some of the marine animals that lay eggs!

When you think of animals that lay eggs, you might most commonly think of birds. Birds, and the marine animals we’ll be learning about today are called oviparous. Oviparous animals are ones whose babies hatch from eggs that those animals have laid previously. Some animals, including humans, are viviparous, which means that the offspring must receive nutrients from their mother until they are ready to be born. 

Some of the most common oviparous marine animals are penguins, turtles, crocodiles, alligators, squid, and fish! While they all have this trait in common, it's important to distinguish in which ways these animals differ. While you might’ve thought that sharks and rays are oviparous, some species are actually considered to use ovoviviparity, which is when the eggs develop inside of the mother but don’t need to gather any nutrients from her. A shyshark however is oviparous, as well as some skates and chimaera. 

Fish can lay hundreds, up to millions of eggs, and most are left to float freely in bodies of water, are attached to different underwater plants, or left on the seafloor. Salmon will travel hundreds of miles to spawn, often from where they themselves were born! A female cod can produce between 4-6 million eggs, while in contrast, penguins typically lay only one or two eggs at a time. The emperor penguin only lays one, and the male penguin keeps the egg warm with a pouch by its feet. The adelie and gentoo penguins only lay two eggs at a time and both build nests for their eggs. Similarly alligators also build nests for their eggs, often built out of mud and other vegetation in their habitat. Once their eggs are laid, around 20-30 per season, the female alligator will cover her eggs with leaves and dirt. Turtles also build nests for their eggs on sandbanks, and like salmon, some will travel a long distance before laying their eggs. The number of eggs a turtle will lay in one season, and how often turtles lay eggs, vary depending on the species of turtle. 

Unlike most eggs appearing this season, marine life that lay eggs don’t produce with the same frequency, uniformity, or amount that most eggs that appear this season— not to mention what comes out of those eggs!

So when you’re hunting for eggs this season, or not as the case may be, think about all of the species migrating or nesting this season in order to bring more wonderful animals into the world!

Narwhals are commonly referred to as the “unicorn of the sea,” primarily because of the iconic spiral horn on the front of their heads, but also because not too much is known about these seemingly mythical creatures! A narwhals’ most famous appearance is as an animated character in the movie Elf, and the most common Google search about narwhals is “are narwhals real.” The fantastical nature of these creatures makes todays’ spotlight science article that much more exciting, because in April we are going to be talking about groundbreaking narwhal observations that have never been recorded before!

A study was recently published outlining new narwhal behavioral patterns, all of which were carried out through the use of their long tusks. Scientists from Canada, with the help of Inuit communities, observed a surprising total of 17 behaviors utilizing the tusk, proving that horn isn’t just there for show. The narwhals displayed foraging behaviors, precisely using their tusks to track and manipulate fish movement. They also displayed social behaviors akin to resource guarding, using their tusks to protect their target fish from other narwhals. Their findings lead to a number of questions. Does echolocation with the tusk play a role in tracking? How intricate is the social order between narwhal individuals? Of course these questions require further research. But how are scientists making these observations to begin with?

For this project, and presumably others, the researchers were able to record their observations, not from the water, but the sky! Drones, called UAVs (unmanned aerial vehicles) were the star cameramen, recording the footage which was then slowed, zoomed, refined, and finally analyzed. The research team plans to continue with this methodology to establish baseline behaviors and observe behavioral changes as climate change continues its’ ecological upset.

One buzzword relating to global warming and climate change is the phenomenon of coral bleaching. Coral reefs are made up of millions of individual animals called polyps. These polyps use a compound called calcium carbonate (CaCO₃) to build a hard skeleton, creating coral reef structures that house many different fish, invertebrate, and algal species. Coral reefs are considered one of the most diverse, beautiful ecosystems! How do these tiny, immobile coral polyps live, feed, and grow? 

Coral polyps work closely together with algae called zooxanthellae to survive. In fact, the zooxanthellae actually live inside coral tissues! The coral and zooxanthellae provide each other helpful resources in a beneficial relationship called mutualism. The coral host protects the zooxanthellae and also provides nitrogen and carbon which the zooxanthellae use for photosynthesis. In turn, the zooxanthellae produce sugars during photosynthesis, which the coral host uses for growth and reproduction. 

Due to global warming and climate change, the sea surface temperatures have been rapidly rising, which threatens coral health. As ocean temperature rise, coral and zooxanthellae metabolism increases (metabolism refers to the chemical reactions that are necessary for life). As a result, there is more nitrogen and carbon available to the zooxanthellae, making it less dependent on the coral host. The coral host then receives less sugar from the zooxanthellae, and in its stress, expels the zooxanthellae from its tissues. This expulsion causes the coral to turn stark white, known as bleaching, and often leads to coral starvation and death. As coral reefs provide homes for almost 25% of all ocean species, coral bleaching and death is extremely harmful! 

How will corals survive if ocean temperatures continue to rise? In recent research, scientists have observed a sliver of hope for corals to adapt and avoid bleaching. One study deliberately exposed young coral polyps, or larvae, to hotter temperatures to study how they responded. Surprisingly, they found that the coral larvae did not show signs of bleaching. Instead, the larvae adapted in two ways. First, the larvae reduced their metabolism— going into energy-saver mode to save their sugar resources. Second, the coral larvae held onto more nitrogen, limiting the amount of nitrogen available to the zooxanthellae. By doing this, the zooxanthellae continued to rely on the coral host for nitrogen and provided the coral hosts sugar.

Although there are still many unanswered questions regarding the mutualistic relationship between coral and zooxanthellae, this discovery is super exciting. This research hints at the fact that coral may be able to adapt to hotter water temperatures, allowing them to avoid bleaching and to continue to support many of the oceans’ creatures!