Eutrophication phosphate into water is slow, hence the difficulty of reversing the effects of eutrophication. However, numerous literature report that nitrogen is the primary limiting nutrient for the accumulation of algal biomass. The sources of these excess phosphates are phosphates in detergent, industrial/domestic run-offs, and fertilizers. With the phasing out of phosphate-containing detergents in the 1970s, industrial/domestic run-off and agriculture have emerged as the dominant contributors to eutrophication. Cultural eutrophication is the process that speeds up natural eutrophication because of human activity. Due to clearing of land and building of towns and cities, land runoff is accelerated and more nutrients such
Carnivorous plant more or less than this optimum will take up less carbon dioxide than an optimal plant, and hence growing less well. These plants will be at a selective disadvantage. At zero investment the growth is zero, because a non-carnivorous plant cannot survive in a habitat with absolutely no soil-borne nutrients. Such habitats do not exist, so for example, "Sphagnum" absorbs the tiny amounts of nitrates and phosphates in rain very efficiently and also forms symbioses with diazotrophic cyanobacteria. In a habitat with abundant soil nutrients but little light (as shown above), the gross photosynthesis curve will be lower and flatter,