Phytoplankton productivity as a function of N and p concentrations and sunlight In winter low temperature and Phosphates and Phytoplankton sunlight are the nitrates at surface productivity limiting factors to talal phytoplankton productivity. In summer, nutriel become the limiting factor Decay of dead plant matter replenish nutrients leading to a secondary peak of phytoplankton winter Spring Summer Autumn winter productivityPhytoplankton productivity as a function of N and P concentrations and sunlight In winter, low temperature and sunlight are the limiting factors to phytoplankton productivity. In summer, nutrients become the limiting factor. Decay of dead plant matter replenish nutrients, leading to a secondary peak of phytoplankton productivity