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The dynamics of the lower-level components of the coastal food web of Qatar are presented as an 'organic carbon' budget that summarizes comprehensive sampling of the phytoplankton, zooplankton and benthos at standard, repeated locations seasonally over a two year period. Moderate levels of phytoplankton biomass and primary production support diverse, healthy assemblages of zooplankton and benthos that are typical of sub-tropical ecosystems. The primary production however must be supported by sources of new or regenerated inorganic nutrients, such as rate-limiting nitrate, but no clear sources (such as freshwater runoff or upwelling) can be identified in this ecosystem, surrounded as it is by desert. A coupled carbon/nitrogen numerical simulation of the phytoplankton, zooplankton and benthos is used to test the hypotheses that 'new' or regenerated nutrients are supplied by i. export from coastal mangroves forests, ii. nitrogen fixation in the plankton, iii. benthic-pelagic coupling, or iv. the annual (summer) low-salinity, nutrient-rich current from the Sea of Oman. While the potential that high temperatures, high salinities and low oxygen affect metabolic rates, a general limitation of available inorganic nutrients at the bottom of the food web appears to limit sustainable recruitment and biomass.