down sulfated heteropolysaccharides, which are produced by many groups of macroalgae. The breakdown of these sulfated heteropolysaccharides by Planctomycetota are then used as an energy source. Some Planctomycetota are suggested to be capable of breaking down carrageenan. Association with other organisms Planctomycetota have often been observed in association with many organisms, including, macroalgae, microalgae, marine sponges, and plants such as lichens and bryophytes. They have also been observed inhabiting deep-sea cold seeps, where they are dominant organisms living on tube worms. Macroalgae Planctomycetota are often associated with marine surfaces high in nutrients. They occur as biofilms on algal surfaces in relatively high abundance. Macroalgae such as the kelps Laminaria hyperborea and Ecklonia radiata are suggested to be an important habitat for Planctomycetota. Roughly 70% of the bacterial community on Ecklonia radiata were Planctomycetota. Almost 150 Planctomycetota species have been isolated from the biofilms of macroalgae, and these communities associated with macroalgae are mainly independent of changes in geographical distribution. This would suggest a symbiotic relationship. Kelp forests dominate the rocky coastlines of temperature regions, and provide habitat, shelter, and food for many organisms, including the Planctomycetota. Given the considerable role of kelp forests in coastal primary productivity, the association of the Planctomycetota with kelp could indicate their significant role in coastal habitats. Planctomycetota also play an important role as components of detritus in the water column, also known as marine snow, given their ability to attach to surfaces. As the climate continues to warm, the abundance of Planctomycetota associated with macroalgae might increase. The seaweed Caulerpa taxifolia was incubated under higher CO2 conditions, and the abundance of Planctomycetota increased substantially, as much as 10 times in some species. Microalgae and diatom blooms While macroalgae are well known substrates for Planctomycetota communities, their abundance has also been known to correlate with blooms of microalgae such as diatoms. Blooms of cyanobacteria, diatoms, and dinoflagellates provide nutrients for Planctomycetota, which could explain the association. Marine sponges Planctomycetota species are often associated with the surfaces of marine sponges. They interact with sponges either by attachment with a holdfast, or through a symbiotic relationship. A high diversity of Planctomycetota is present as biofilms on sponges. The symbiotic relationship among sponges and Planctomycetota contributes to the health of the sponge, and the sponge often provides suitable habitat and nutrients to the Planctomycetota. Lichen communities and sphagnum bogs Planctomycetota were found to be highly abundant in lichen