With ocean levels reaching new lows with every passing year, large expanses of seabed once too deep to support photosynthetic life now find themselves basking in the life-giving sunlight for the first time. Single-celled green algae were the first to take advantage of this new supply of energy, coating the carbon-rich mud with a thin biofilm. Next came the cyanobacteria; despite their lower degree of complexity, they gained an edge over their eukaryotic competitors due to their ability to form tall stromatolites that towered over the seafloor, overshadowing other photosynthesizers as they reached higher and higher toward the waves. In turn, starting around 1.4 million PA, they too found themselves choked out by a newcomer.
Descended from the semi-aquatic water-lily-like baskets, Apterra's first true seagrasses evolved from a widespread pond-growing ancestor that adapted to germinate in fully-inundated soil, granting it the capacity to grow in far deeper water than any other plant. After evolving salt-tolerance and spreading into the sea about a million years ago, they rapidly spread across the newly-formed shallows. As long as light reached the seabed, they could sprout, growing rapidly to the surface. Like other grasses, their blades had the ability to regrow after being cut, a feature that only became more useful with the diversification of seagoing herbivores. Expanding further on this ability, the Seabaskets (Thalassocanistrum) now possess leaves that grow indeterminately, extending all the way to the surface if not cut or consumed. Indeed, if allowed to grow freely, these wavy, kelp-like blades will continue growing into a thick tangle of foliage floating atop the surf, smothering all photosynthetic life, including young seabaskets. In a sense, then, the plants actually rely on aquatic grazers to promote recruitment.
More than a thousand millennia since the seabasket forests first sprouted, animals of many different lineages have evolved to take advantage of the new biome. Fish of all kinds find refuge here, feeding on the abundant isopods that chew away at the fast-growing plants. Thalassaurs arrived soon after; some, like the Gheckial (Thalassaurus gracilidens), prefer piscine prey, and others like the Siren Gecko (T. fluctuopascor) prefers to graze on the soft vegetation that would otherwise clog the water. Especially dense seabasket groves are a feeding ground for seawis, who weave through the rippling blades in pursuit of fish and large invertebrates. Even the neotenic mosquitoes have a presence here, chasing after plankton and fish fry with powerful strokes of their tails.
This habitat won't make it out the other side of the approaching ice age unscathed; the shallow continental shelf around the Gecko Isles that supports over 80% of all seabasket forests will be above the low-tide line in another 75,000 years or so. Species that are too specialized for life in this environment are already doomed to die with it.