Actual and potential heterotrophicneutrogen fixation and detrification rates of oryza glumaepatula Steud in an amazonian lake

Abstract

Estimates of the rates of heterotrophic nitrogen fixation (HNF) and denitrification by acetylene reduction and acetylene inhibition, respectively, were determined for the roots and culms of wild rice, Oryza glumaepatula, in Lake Batata, a lake severely impacted by the dumping of bauxite tailings into the lake basin. Two stations were established in different parts of the lake: one in a natural area and other in an impacted area of the lake. Plant assays were performed during the principle hydroperiods of dry (December) and flood (July) to determine both: a) Actual rates of HNF and denitrification, and b) potential rates of HNF after amending with glucose potential rates of denitrification after amending with glucose, glucose + nitrate, or nitrate alone. HNF was found to naturally exceed denitrification in this system. HNF and denitrification were consistently found to be greater for roots than culms but no correlation was found between rates of HNF or denitrification and water depth. It was determined that for HNF and denitrification that glucose and nitrate were the limiting factors in controlling those processes in roots and culms of O. glumaepatula. HNF and denitrification of O. glumaepatula does not appear to show differences between impacted and non-impacted areas.Key words: biological nitrogen fixation, Amazonian lake, aquatic macrophyte. RESUMOTaxas reais e potenciais de fixação heterotrófica de nitrogênio e de desnitrificação em Oryza glumaepatula Steud em um lago amazônico Foram estimadas taxas reais e potenciais de fixação heterotrófica de nitrogênio (FHN) e de desnitrificação pela metodologia da redução de acetileno e inibição por acetileno, respectivamente. Estas taxas foram determinadas para raízes e colmos de uma espécie selvagem de arroz, Oryza glumaepatula, presente no lago Batata, um ecossistema impactado pelo lançamento de rejeito de bauxita. Foram escolhidas duas estações de coleta no lago Batata: uma localizada na área natural e outra localizada na área impactada por rejeito de bauxita. Os experimentos foram realizados nos dois períodos mais representativos do pulso hidrológico: seca (dezembro) e cheia (julho). Foram determinadas: a) taxas reais de FHN e desnitrificação e b) taxas potenciais de FHN após a adição de glicose de taxas potenciais de desnitrificação após a adição de glicose, nitrato e nitrato + glicose. O processo de FHN excede o processo de desnitrificação nesse sistema. Os processos de FHN e de desnitrificação foram maiores em raízes do que em colmos de O. glumaepatula, porém nenhuma correlação foi encontrada entre estas taxas e a profundidade da água. Verificou-se que a glicose e o nitrato foram os fatores Rev. Brasil. Biol., 59(3) Palavras-chave: fixação biológica de nitrogênio, lago Amazônico, macrófita aquática.

From virus to igapó forest: a systematic review of 35 years monitoring of an Amazonian Lake impacted by bauxite tailings (Batata Lake)

“…Further, other discoveries from the long-term research of Batata Lake have revealed the recovery capacity of the igapó forest after revegetation interventions (Barbieri et al, 2000b;Esteves, 2000;Scarano et al, 2018) and the role of the wild rice Oryza glumaepatula in reestablishing local communities due to increasing organic matter and nutrient concentrations in the impacted sediments (Enrich-Prast, 1998;Enrich-Prast et al, 1999), and the accumulation of detritus over the sediment avoiding the resuspension of the bauxite tailings . Studies on the omnivorous catfish Auchenipterichthys longimanus indicated a potential disperser of forest seeds with distinct germination and dormancy patterns in the lake (Mannheimer et al, 2003).…”

“…Nitrogen and carbon cycling also received substantial attention during the monitoring project of Batata Lake. The former was mainly explored regarding nitrogen fixation (Enrich-Prast et al, 1999, 2002Enrich-Prast & Esteves, 1996, 1998, Esteves et al, 2001Nielsen et al, 2004), and the latter considering particulate organic carbon incorporation by organisms (Bozelli, 1998a, b), dissolved organic carbon (DOC) quality, origin, and photo-oxidation (Amado et al, 2003(Amado et al, , 2006Farjalla et al, 2006), and recently CH 4 production (Conrad et al, 2010;Vavilin et al, 2017).…”