In many freshwater ecosystems, the availability of inorganic nitrogen compounds is a limiting factor for growth. This means that producers cannot grow as quickly as they could even though no other factor is limiting. Which statements about these ecosystems are correct? 1 Transfer of energy to higher trophic levels is also limited by availability of these nitrogen compounds. 2 Addition of excess nitrate compounds will benefit all organisms in the ecosystem. 3 The percentage of energy lost between trophic levels will be the same whether nitrogen compounds are limiting or not. 4 Addition of ammonium compounds will cause an increase in the numbers of nitrifying bacteria.