Now, after a half-century of accelerated nitrogen input (much of it from direct atmospheric deposition), the lake is phosphorus-limited. Theodore Swift et al.,[82] concluded that "suspended inorganic sediments and phytoplanktonic algae both contribute significantly to the reduction in clarity, and that suspended particulate matter, rather than dissolved organic matter, are the dominant causes of clarity loss." The largest source of fine sediment particles to Lake Tahoe is urban stormwater runoff, constituting 72 percent of the total fine sediment particle load.[83] Recent research has shown that the urban uplands also provide the largest opportunity to reduce fine sediment particle and phosphorus contributions to the lake.