Flies of the genus Coelopa lay their eggs onto these organisms found decomposing at wrack zones. It’s not diatoms, but non-photochemical quenching in one clade of these organisms is facilitated by allenic pigments called fucoxanthins. The thallus of these organisms comprises the stipe and lamina, which are connected to gas-filled (*) pneumatocysts [new-MAT-uh-sists]. Carrageenans synthesized by these organisms are harvested for use as food thickeners. Eel migration is speculated to be propagated by free-floating kinds of these (-5[1])organisms named after the Sargasso (10[1])Sea. Sea otters are a keystone (10[1])species of these organisms’ namesake ecosystems. For 10 points, name these plant-like algal organisms that form namesake underwater “forests.” (10[1])■END■