Short answers, pulled from the story.
The oldest undisputed fossil evidence of cyanobacteria dates back 2100 million years. Stromatolites associated with cyanobacterial biofilms appear as early as 3500 million years ago, marking the beginning of oxygenic photosynthesis on Earth.
The oldest undisputed fossil evidence of eukaryotic algae is Bangiomorpha pubescens, a red alga found in rocks around 1047 million years old. This fossil provides a glimpse into the early history of diverse organisms and challenges the notion of a single origin for algae.
Kelp can grow up to 50 meters in length. This macroalgae represents one end of the spectrum of algae diversity, ranging from unicellular microalgae to large multicellular forms.
Samuel Gottlieb Gmelin published Historia Fucorum in 1768, which was the first work dedicated to marine algae and the first book on marine biology to use the then new binomial nomenclature of Linnaeus. This publication marked a significant step in the history of algae classification.
Algal turf scrubbers have been found to capture 60 to 90% of nitrogen runoff from manure effluents. These horizontal algae scrubbers increase the quality of water flowing into rivers, streams, and oceans by reducing toxic chemicals.