Biofilm
This descendent of L. cytosol has evolved within zone 4 to become colonial. The reason for this is that it eliminates all of the shortcomings of solitary life. The L. cytosol would reproduce quickly, and such areas were they had minimal predators were full of L. cytosol. However, despite the abundance of these cells, they could not cooperate in any way, and thus many individuals were left behind, whether they drifted into the shade or otherwise. Thus, with biofilm, the cells are conjoined, forming a living film across the surface of the water, hence the common name. This originally happened when mitosis in an individual failed, and the daughter cells did not fully split apart. This actually turned out to be good, and as the two daughter cells kept splitting, the film grew larger, as all of the new cells were still conjoined. This has only happened in zone 4 due to the calm waters allowing for the biofilm to stay in-tact, however they will likely spread out further. The biofilm survives just like the ancestor, however on a much larger scale. The individual cells only function in the sun, however if a section drifts into the shade, energy from the section still in the light will be transferred equally across the sheet, so that all cells will get energy equally. This means that even cells in the dark can reproduce, and thus the entire film grows consistently, besides at night. Each cell is separated by a thin membrane, with the conjoined areas lacking a cell wall. This allows nutrients to be transferred easily. The nutrients are specifically transferred inside vacuoles that are covered in proteins, so that they can travel freely between cells. There is technically no limit to how large one film can grow, however they are frequently broken up by ripples and waves in the water.