primary productivity | Definition, Measurement, & Facts

Primary productivity, the rate at which energy is converted to organic substances by photosynthetic producers, which obtain energy and nutrients by using ... primaryproductivity Sections&Media Article IntroductionCalculatingprimaryproductivityTypesofprimaryproducers FastFacts Facts&RelatedContent Media Images AdditionalInfo MoreArticlesOnThisTopic Contributors ArticleHistory primaryproductivity biology Alternatetitles:primaryproduction Print print Print Pleaseselectwhichsectionsyouwouldliketoprint: TableOfContents Cite verifiedCite Whileeveryefforthasbeenmadetofollowcitationstylerules,theremaybesomediscrepancies. Pleaserefertotheappropriatestylemanualorothersourcesifyouhaveanyquestions. SelectCitationStyle MLA APA ChicagoManualofStyle CopyCitation Share Share Sharetosocialmedia Facebook Twitter URL https://www.britannica.com/science/primary-productivity More GiveFeedback Feedback Corrections?Updates?Omissions?Letusknowifyouhavesuggestionstoimprovethisarticle(requireslogin). FeedbackType Selectatype(Required) FactualCorrection Spelling/GrammarCorrection LinkCorrection AdditionalInformation Other YourFeedback SubmitFeedback Thankyouforyourfeedback Oureditorswillreviewwhatyou’vesubmittedanddeterminewhethertorevisethearticle. JoinBritannica'sPublishingPartnerProgramandourcommunityofexpertstogainaglobalaudienceforyourwork! ExternalWebsites By TheEditorsofEncyclopaediaBritannica | ViewEditHistory phytoplanktonbloom Seeallmedia RelatedTopics: grossprimaryproductivity netprimaryproductivity biologicalproductivity ...(Showmore) Seeallrelatedcontent→ primaryproductivity,inecology,therateatwhichenergyisconvertedtoorganicsubstancesbyphotosyntheticproducers(photoautotrophs),whichobtainenergyandnutrientsbyharnessingsunlight,andchemosyntheticproducers(chemoautotrophs),whichobtainchemicalenergythroughoxidation.NearlyallofEarth’sprimaryproductivityisgeneratedbyphotoautotrophs.CalculatingprimaryproductivityThetotalamountofbiologicalproductivityinaregionorecosystemiscalledthegrossprimaryproductivity.Acertainamountoforganicmaterialisusedtosustainthelifeofproducers(orautotrophs)inafoodchain,andwhatremainsisthenetprimaryproductivity,whichcanbeusedbyconsumers(orheterotrophs,whicharemadeupofherbivoresandcarnivoresineachenvironment).Primaryproductivityisusuallydeterminedbymeasuringtheuptakeofcarbondioxideortheoutputofoxygen.Productionratesareusuallyexpressedasgramsoforganiccarbonperunitareaperunittime.TypesofprimaryproducersInmarineenvironments,thetwoprincipalcategoriesofproducersarepelagicphytoplankton,whichfloatfreelyintheocean,andbenthicalgae,whichliveatorneartheocean’sfloor.Interrestrialenvironments,primaryproductivityisgeneratedbytreesandotherlandplants(includingplantedcrops).Mostprimaryproducersrequirenitrogenandphosphorus—whichareavailableasdissolvednutrientsinthesoil,lakes,andriversandintheoceansasnitrate,nitrite,ammonia,andphosphorus.Theabundancesofthesemoleculesandtheintensityandqualityoflightexertamajorinfluenceonratesofproduction.Theannualproductivityoftheentireoceanisestimatedtobeapproximately50×1015grams(50×109metrictons)ofcarbonperyear,whichisabouthalfoftheglobaltotal.Mostprimaryproductivityintheoceansiscarriedoutbyfree-floatingphytoplanktonintheopenoceanratherthanbybottom-dwelling(benthic)plants,withchemoautotrophscontributingsmalleramountsasproducersindeep-sea-venthabitats.Benthicplantsgrowonlyonthefringeoftheworld’soceansandareestimatedtoproduceonly5to10percentofthetotalmarineplantmaterialinayear.TheEditorsofEncyclopaediaBritannica ThisarticlewasmostrecentlyrevisedandupdatedbyJohnP.Rafferty.