A wall of granite looms above the sea on the western coast of Unciolis. Cliffs like these were Apterra's most common shoreline formation prior to terraforming, surrounding most major landmasses. A combination of millions of years of biological weathering, sea levels rising and falling, and the once-unstoppable movement of ice sheets has turned most of these areas into more gently-sloping beaches. In a few corners of the world, though, the old cliffs still stand tall. At low tide, one can stand on the exposed seabed, looking up at the line of encrusted salt 15 meters overhead that marks where the water will reach in just a few short hours. Dotting the stony surface are organisms of all kinds, forming an ecosystem unlike any other.
The foundation of the cliffside food web is rockslime algae. These hardy dinoflagellates can survive a variety of conditions, resisting desiccation better than most other aquatic photosynthesizers. Up to a dozen species can be found on a typical cliff face, stratifying based on the particular conditions of each region. For example, the Unciolan Red Rockslime (Petrolubricus rupensis), a fast-growing but thirsty species, may straddle the low-tide line, while Windy Rockslime (P. altocrescus), which can handle drier conditions, may occupy a higher zone. Outcrops with horizontal surfaces may be populated by Violet Rockslime (P. purpureus), whose dark pigments keep it safe from ultraviolet radiation in the direct sunlight.
A few species of highly mobile algivores can freely feed on all these varieties. When the tide rises, the Grazing Seastout (Bicolorichthys algivora), a member of the stoutling family that has switched to a vegan diet, swims up and down, taking bites at every level. This helps the fish get a wide range of nutrients, as each species of rockslime has a slightly different nutritional profile. At low tide, terrestrial woodlice from the squashroach family, such as the four-centimeter-long Washroach (Scopularthrus), descend from the vegetation above to feed on the exposed dinoflagellate biofilm. Like all species that feed on rockslime, washroaches have evolved to resist the algae's potent neurotoxicity. In this genus's case, the poisonous substances are deposited in the chitinous matrix of its exoskeleton, granting the isopod a defense mechanism against its own predators.
Many other animals are restricted to specific zones of the cliff. The small Caenarthrid Saxarthrus can only climb about a meter out of the water before it dries out and is forced to return below the waves. Airgill mosquitoes like Rupivermes, which live in small crevices in the rock above the high-water mark, never venture far below their burrows.
Predators from both land and sea make a meal of these small creatures. The Scratchray (Actinodactylus), a small grumbletoad with forward-pointing fin spines, creeps up the vertical surface. It uses its the flexible rays to pry its prey from their hiding places, sometimes even impaling them in the process. Nomadic seacocks such as the Surferbird (Undulapteryx unciolensis) ride the waves as the water gradually climbs, then retreat further offshore after eating their fill. When the waters are particularly calm, meat-hungry scuttleworms may appear, creeping up the submerged stone and squeezing their flat bodies into the tiniest cracks, leaving nothing safe from their needle-like claws.