How Aquatic Plants & Animals Adapt to Their Environment

From submarine canyons in deep-ocean darkness to an ephemeral meltwater pond on a high plateau, aquatic environments encompass an enormous breadth of ecologies. Many plants and animals have adapted well to take advantage of these productive frontiers of water, air and land. Even when the players are radically different, the patterns of lifestyles and behaviors much resemble those of terrestrial organisms.

Aquatic animals and plants both partition themselves into different ecological niches (or roles) to reduce resource competition and maximize utility of their environment. Plants in a freshwater marsh pursue a range of lifestyles. Some, such as water lilies, float their leaves and flowers at the surface, while others, such as cattails, are rooted in sediment and extend their stalks above the water’s surface. In the oceans, some species, such as oceanic whitetip sharks and leatherback turtles, forage in pelagic environments far out to sea, while others, such as sea otters, favor coastal environments. Still more manage to survive in the benthic zones of the seafloor.

As on land, the world’s aquatic systems play host to ceaseless dramas of life and death in the form of predatory struggles. In the oceans, many fish are schooling, traveling in massive aggregations that reduces any one individual’s chances of sticking out to a passing predator. In the muck of a marsh rim, a northern leopard frog camouflages itself with stillness and intricate markings. White sharks cruise the mid-depths, their eyes trained to the surface to pick out telltale silhouettes of elephant seals and other favored prey. Along sloughs and wetland margins, kingfishers and night herons pursue the same fish, but the former do it by ambushing from tree perches, while the latter stalk the shallows and dart their prey with lightning-fast lunges.

Many aquatic ecosystems, particularly in semi-arid climates and those experiencing distinct dry seasons, are ephemeral or temporary in nature. A playa pond on Texas’ high plains or a creek in East African woodland may dry up in extended drought. Less mobile species such as fish, crayfish or aquatic snails may be doomed if their wetland vaporizes, while others, such as crocodilians, mink, waterfowl or hippos, can often migrate to a new home. Many migratory birds, from geese and swans to sandpipers, use aquatic environments only during certain times of year: for breeding, for wintering or simply as a convenient stopover on a long journey in between.

The streamlined shapes of so many kinds of fish and aquatic mammals are honed for efficient travel through their watery universes. Dolphins and sharks famously resemble one another, with sharp dorsal fins and lean forms: This is a case of convergent evolution, when two unrelated species come to adopt similar morphologies because of the common pressures of their environment. Aquatic or semi-aquatic plants do this too: Giant cane and bulrushes are not closely related (one’s a grass and one’s a sedge), but they look similar with their stout, tall stalks and constitute similar landscape features (canebrakes and tule beds).