Selbert

This creates the conditions for sea grass beds and shellfish to thrive.Sea cucumber excretions can also aid in coral formation and may play a role in buffering marine environments from ocean acidification.As the ocean vacuum cleaners, they are very good at their job:about half of the sandy seafloor is thought to have passed through the digestive tract of a sea cucumber.So next time you're rejoicing in the feeling of sand crunching between your toes, consider this:those very grains of sand might have, at one point or another,been excreted by a pickle that breathes through its butt.

Sea cucumbers are found everywhere from shallow shores to abyssal trenches 6,000 meters below sea level.On the deep sea floor, they comprise the majority of animal biomass,reaching up to 95% in some areas.As these sausage-shaped wonders trudge along, they vacuum up sand,digest the organic matter it contains, and excrete the byproduct.In this process, sea cucumbers clean and oxygenate the seafloor by breaking down detritus and recycling nutrients.

This act is called visceration and it's a surprisingly effective defense mechanism.In addition to startling and distracting predators,the innards of some sea cucumber species are sticky and toxic.Evisceration may seem drastic,but sea cucumbers are able to regenerate what they're lost to their gut reaction in just a few weeks time.Aside from the few species that have evolved to swim and those that feed without moving,many of these cumbersome creatures pass their time grazing the seabed.

This versatile tissue has many advantages:it aids in efficient locomotion,enables sea cucumbers to fit into small spaces,and allows them to reproduce asexually by splitting apart.But MCT most explosive application is employed when a predator attacks.By loosening the attachments of internal tissues then quickly softening and contracting their muscles,many species are capable of shooting a wide range of organs out of their anuses.

But even sea cucumbers that lack anal teeth are outfitted with tools to defend themselves.They evade threats and launch counter-attacks using their mutable collagenous tissue, or MCT.This gel-like tissue contains bundles of collagen, called ibrils.Proteins can interact with these fibrils to slide them together,stiffening the tissue, or apart, softening it.

Certain species of crabs and pearlfish take advantage of this rhythmic action and,once the sea cucumber anus is dilated,they shimmy in and take shelter.The rear end of a single sea cucumber can harbor up to fifteen pearlfish at a time.However, it seems that not all sea cucumbers put up with this intrusive behavior.Some species are equipped with five teeth around their anus,suggesting that they may have taken an evolutionary stand against unwanted guests.

Adhesive tube feet run the length of their bodies and allow them to scoot along the seafloor.Specialized tube feet can be used for feeding and respiration,though many sea cucumbers actually breathe through their anuses.Rhythmically contracting and relaxing their muscles,they draw water in and out over an internal lung-like structure called a respiratory tree that extracts oxygen from seawater.

Some sea cucumbers have feathery tentacles flowing from their mouths,some are puffed like bloated balloons,and others simply look like Headless Chicken Monsters the actual name given to a rare deep-sea species.But they are generally characterized by their long, cylindrical shape.A sea cucumber is essentially a brainless,fleshy form surrounding a digestive tract,bookended by a mouth and an anus.

Can you guess what you're looking at?Is it a fuzzy sock? An overripe banana? A moldy tube of toothpaste?In fact, this is the humble sea cucumber, and while it might look odd,its daily toil paves the way for entire ecosystems to thrive.Sea cucumbers are members of the phylum Echinodermata,along with sea urchins, starfish and other radially symmetrical,piny-skinned marine invertebrates.

If a four-degree Celsius warming persisted for several millennia,the sea level could rise by as much as 10 meters.By studying past climates,scientists learn more about what drives the shifts in ice that have shaped our planet for millions of years.Research suggests that by taking action now to reduce carbon dioxide emissions quickly,we still have the opportunity to curb ice loss and save our coastal communities.

Computer models forecast another one to four degrees Celsius of warming by 2100,depending on how much additional fossil fuel we burn.What does that mean for the ice currently on Greenland and Antarctica?Past climate changes suggest that even a small warming shift can begin a process of ice melt that continues for thousands of years.By the end of this century,ice melt is expected to raise the sea level by 30 to 100 centimeters,enough to impact many coastal cities and island nations.

Why?Carbon dioxide levels in the atmosphere have been rising since the 19th century,when fossil fuel use increased.We know that from studying air bubbles trapped in Antarctic ice.This surge in carbon dioxide also coincides with a global temperature increase of nearly one degree Celsius.Ice cores and atmospheric monitoring stations show us that carbon dioxide levels are rising faster,and to higher levels,than at any point in the last 800,000 years.

By analyzing pollen and marine fossils,geologists can tell that temperatures peaked about 6,000 years ago,before another shift in Earth orbit caused renewed cooling.So what's coming next?Based on the repeated natural cycle seen in the climate record,we're normally expect the Earth to continue a trend of gradual cooling for the next few thousand years.However, this cooling abruptly reversed about 150 years ago.

Simultaneously, cooler conditions transfer carbon dioxide from the atmosphere into the ocean,causing even more cooling and glacier expansion.About 20,000 years ago,these trends reversed when changes in Earth orbit increased summer sunshine over the giant ice sheets, and they began to melt.The sea level rose 130 meters and carbon dioxide was released from the ocean back into the atmosphere.

These wobbles, combined with the planet elliptical orbit,cause summer temperatures to vary depending on whether the summer solstice happens when Earth is closer or farther from the sun.Approximately every 100,000 years,these factors align to create dramatically colder conditions that last for millennia.Cool summers that aren't warm enough to melt the preceding winter snow allow ice to accumulate year after year.These ice sheets produce additional cooling by reflecting more solar energy back into space.

Natural processes, such as volcanism,chemical weathering of rocks,and the burial of organic matter,can cause huge changes in carbon dioxide when they continue for millions of years.Over the past million years, carbon dioxide has been relatively low,and repeated glacial maxima have been caused by cycles in Earth movement around the sun.As Earth rotates,it wobbles on its axis and its tilt changes,altering the amount of sunlight that strikes different parts of its surface.

Throughout Earth history, climate has varied greatly.For hundreds of millions of years,the planet had no polar ice caps.Without this ice, the sea level was 70 meters higher.At the other extreme, about 700 million years ago,Earth became almost entirely covered in ice during an event known as nowball Earth.So what causes these massive swings in the planet climate?One of the main drivers is atmospheric carbon dioxide,a greenhouse gas that traps heat.

Twenty thousand years ago,the Earth was a frigid landscape where woolly mammoths roamed.Huge ice sheets, several thousand meters thick,encased parts of North America, Asia, and Europe.We commonly know it as the Ice Age.But geologists call it the Last Glacial Maximum.That because it's the most recent time that ice reached such a huge extent,and ice age is an informal term without a single agreed-upon definition.Over the last million years,there have actually been about 10 different glacial maxima.