abstract algae background blue brown floats green haptera holdfast kelp lamina littoral marine nature ocean planktonic pools rock saavem sea sorus spore stipe texture thallus tidal water weed backdrop black close close-up closeup definition detail detailed details dynamic flora free greenery HDR high image organic pattern photo photograph picture plancton plankton plant plants range resource seabed shade shades shadow shadows somadjinn stock strand strands textured UP urchin urchins vegetation white