Mitochondria transfer energy from to atp; chloroplasts transform energy into the chemical energy of atp. food . . light . . nuclear chemical . . food . . light light . . food . . kinetic food . . light . . chemical

Mitochondria transfer chemical energy from food to ATP; chloroplasts transform light energy into the chemical energy of ATP.
Mitochondria and chloroplasts are capable for converting chemical energy from food (or light) in the cell to energy in a form usable to that cell (ATP).
High-energy electrons which are produced during the oxidation of food molecules (or from the action of sunlight in case of chloroplast) are transferred through the electron transport chain located in the inner membrane of mitochondria. These electron transfers release energy that is used to pump H+ and thus generate an electrochemical proton gradient. H+ moves down its electrochemical gradient through a protein called ATP synthase permitting the proton gradient to drive the production of ATP.

Although i don't know what is the simulated system, starfish are predators that eat mostly  microalgae,  snails, sponges, bivalves, mussels and other small marine animals. removing starfish from any system would definitely increase this animals that they prey.