Aquatic Ecosystems


when you start to develop your powers for empathy and imagination the whole world opens up to you so let’s exercise those powers imagine you are suddenly transformed into a fish it doesn’t take a lot of imagination to realize the first thing you need to do is find water lucky for you you live on a water planet most of the living space on your planet is water you just need to decide what kind of water you want to live in salt water fresh water or a mix of the two since marine ecosystems cover 71% of the planet’s surface if you decide to be a saltwater fish you have lots and lots of choices of places to live you could live out in the open ocean in surface waters where it’s bright and sunny and there’s food to eat but no place to hide from predators or down deep where it’s cold and dark and there’s not much food except what rains down from above but it is a whole lot easier to hide from predators if you stay down here you’ll probably want to be the kind of fish that makes light called bioluminescence light you can use to help find food or attract a mate or you could head for Shore where there are plenty of hiding places and plenty of food and a kelp forest maybe or how about a coral reef or a seagrass meadow if you decide instead to be a freshwater fish your choices are much more limited since freshwater ecosystems cover less than 1% of Earth’s surface there just isn’t a lot of fresh water on your planet and a lot of what there is is tied up in polar ice caps glaciers and underground aquifers what little is left in lakes ponds rivers and streams makes for slim pickings in the fish real-estate market slim in terms of available space but not in terms of variety freshwater habitats are like islands of water in a sea of land so each island can be very different from the next requiring fish to adapt accordingly which helps explain why 40% of all the fish species on earth live in freshwater ecosystems different fish adapted to live in different ecosystems all of them fresh or how about a mix of fresh water and salt where rivers meet the sea in what are called estuaries here there is phenomenal diversity and abundance of species rivers and rain carry nutrients off the land and into the estuary where they stimulate plant growth providing abundance of food and hiding places compared to the open ocean where nutrients are often in short supply this is prime real estate which is why many open ocean fish come here to spawn this is where life begins for many ocean fish thus earning estuaries the reputation of nurseries of the sea these extraordinary ecosystems cover less than 1 mm of a percent of the Earth’s surface area but they are some of the most productive ecosystems on the planet if you decide to live here you’re going to have a rich bounty of food and shelter but because it is a mixing zone you will have to be pretty tolerant of widely fluctuating environmental variables like salinity and temperature any one of these ecosystems could be perfect for you if you imagine yourself as the right kind of fish because wherever you live you need to be adapted to tolerate the range of environmental variables that you will encounter while living there if you stay within your zone of tolerance you will thrive just outside that zone you may survive but not thrive and let’s not even talk about what happens if you get too far outside the zone it’s all about being in the zone you

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