Create a square, realistic image of a trophic pyramid designed to resemble an oc

Create a square, realistic image of a trophic pyramid designed to resemble an ocean for a scientific poster. The pyramid should be divided into four levels by lines, each representing different ocean depths. Use a gradient of ocean blue colors, with the darkest blue at the top to represent the deep sea and gradually becoming lighter towards the base, which represents the shallower, sunlit waters. The base should feature realistic images of algae and plankton. Ensure that the interior of the pyramid looks like the ocean at various depths, with no animals except for those at the base. The exterior of the image should be a clean, transparent PNG format.