<P> Chloroplasts evolved following an endosymbiotic event between an ancestral, photosynthetic cyanobacterium and an early eukarytoic Phagotroph . This event (termed Primary endosymbiosis) resulted in the origin of the red and Green algae, and the Glaucophyte s, which make up the oldest evolutionary lineages of photosynthetic eukaryotes . A secondary endosymbiosis event involving an ancestral red alga and a heterotrophic eukaryote resulted in the evolution and diversification of several other photosynthetic lineages . </P> <P> The coralline algae, which secrete calcium carbonate and play a major role in building coral reefs, belong here . Red algae such as dulse (Palmaria palmata) and laver (nori / gim) are a traditional part of European and Asian cuisines and are used to make other products such as agar, carrageenans and other food additives . </P> <P> Unicellular members of the Cyanidiophyceae are thermoacidophiles and are found in sulphuric hot springs and other acidic environments . The remaining taxa are found in marine and freshwater environments . Most rhodophytes are marine with a worldwide distribution, and are often found at greater depths compared to other seaweeds because of dominance in certain pigments (i.e., Phycoerythrin) within their chloroplasts . Some marine species are found on sandy shores, while most others can be found attached to rocky substrata . Freshwater species account for 5% of red algal diversity, but they also have a worldwide distribution in various habitats; they generally prefer clean, high - flow streams with clear waters and rocky bottoms, but with some exceptions . A few freshwater species are found in black waters with sandy bottoms and even fewer are found in more lentic waters . Both marine and freshwater taxa are represented by free - living macroalgal forms and smaller endo / epiphytic / zoic forms, meaning they live in or on other algae, plants, and animals In addition, some marine species have adopted a parasitic lifestyle and may be found on closely or more distantly related red algal hosts </P> <P> In the system of Adl et al. 2005, the red algae are classified in the Archaeplastida, along with the glaucophytes and green algae plus land plants (Viridiplantae or Chloroplastida). The authors use a hierarchical arrangement where the clade names do not signify rank; the class name Rhodophyceae is used for the red algae . No subdivisions are given; the authors say, "Traditional subgroups are artificial constructs, and no longer valid ." </P>

Where is red algae found in the ocean
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