Jellyfish the size of a dining room table have been washed up on Great Barrier Island New Zealand, leading a scientist to blame pollution for the over-grown monsters. The biggest of purple lion mane jellyfish measured 1.5m across. The species was not only rare in New Zealand but these specimens were abnormally large. While jellyfish normally feed on zooplankton, tiny animals near the bottom of the ocean food chain, they can feed on an unusually large, jelly-like form of phytoplankton (the oceanâs plant âsoupâ) called dinoflagellate. Unseasonable amounts of dinoflagellate were around at the moment, noticeable through the effect of âphosphorescenceâ, or âsea sparkâ which doesnât usually arrive until late summer. Scientists believe phosphorescence could be caused by high concentrations of nutrients in the sea from run-off from sewage or other pollutants.