The Wine-Dark Sea

While Gambusia slowly evolve their way further and further from shore, the open ocean remains for now devoid of complex life. A variety of tiny crustaceans, dinoflagellate algae, and a diverse suite of bacteria rule the waves. Algal blooms occur regularly across the surface, staining the water red. As they grow unchecked, the cells form opaque mats across the water, entirely blocking light and oxygen from reaching lower layers. These masses of algae may stretch dozens of kilometers in semi-enclosed bays and basins where waves and tides are limited. The open ocean tends to break up any large solid structures; thus, the phytoplankton there live suspended in the water column. In either case, they completely dominate the seas, outcompeting other photosynthesizers.

Some hardy zooplankton try to feed on it, but the toxins produced by the red tide keep their numbers low. A few species of small copepod persist despite this, serving as the sole organisms keeping the Gonyaulax, Karenia, and other related genera in check. Occasionally, they may consume enough to form a hole in the dense mat, leaving an opening through which oxygen can reach the waters below. As they are specialized to eat just a few species of algae, they often ignore the small colonies of unicellular chlorophytes that grow in these windows. 

The winner of this fight depends heavily on location. In the estuaries, extreme red tides are rare, as non-toxic algae are more efficient at living on the masses of dead grass that wash up there. On the other hand, the enclosed sea separating Loxodia from Abeli is almost entirely covered in dinoflagellates. Being protected on all sides by land, the surface is calmer here than in other bodies of water. This leads to a continuous mat of reddish-colored algae (though true members of the red algae clade are not present on Apterra) stretching over 50 kilometers off the coast, growing too fast for the grazing copepods to keep it at bay. Other regions fall somewhere between these extremes, often fluctuating from an empty, clear color to poisonous red and back again in a matter of weeks.

This cycle won’t last forever. Already, several forces are emerging that will help develop the oceans of Apterra into a productive ecosystem. For another couple hundred millennia, though, the seas will continue to run red.