haracterizing Trophic State in Tropical/Subtropical Reservoirs: Deviations among Indexes in the Lower Latitude

Autor(es)

Fernandes Cunha, Davi Gasparini ^[1] ; Finkler, Nicolas Reinaldo ^[1] ; Lamparelli, Marta Conde ^[2] ; Calijuri, Maria do Carmo ^[1] ; Dodds, Walter K. ^[3] ; Carlson, Robert E. ^[4]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Dept Hidraul & Saneamento, Escola Engn Sao Carlos, Sao Carlos, SP - Brazil

^[2] Co Ambiental Estado Sao Paulo, Sao Paulo, SP - Brazil

^[3] Kansas State Univ, Div Biol, Ackert Hall, Manhattan, KS 66506 - USA

^[4] Kent State Univ, Kent, OH 44242 - USA

• Tipo de documento: Artigo Científico
• Fonte: Environmental Management; v. 68, n. 4 AUG 2021.
• Citações Web of Science: 2

Resumo

Trophic state indexes (TSI) guide management strategies regarding eutrophication control worldwide. Such indexes usually consider chlorophyll-a (Chl-a), total phosphorus (TP), and Secchi disk depth (SDD) as independent variables for estimating aquatic productivity and the degree of impairment. TSIs for each of these components are frequently averaged to produce a single TSI value associated with a trophic state classification (e.g., oligotrophic, mesotrophic, or eutrophic). The potential divergence among equations and classification systems originally developed for temperate lakes or tropical/subtropical reservoirs might be particularly relevant in the tropics, where there is a lack of data and the use of equations originally developed for temperate systems may be inappropriate. We calculated two widely used TSIs for temperate lakes (TSItemp) or tropical reservoirs (TSItrop) and explored the deviations among TSI components in Brazilian reservoirs. When applied to our tropical/subtropical reservoirs, the TSItemp provided a conservative approach, with lower limits anticipating increasing trophic state classification. TSI components for Chl-a and SDD significantly deviated for both sets of equations, and these discrepancies were related to turbidity, water temperature, and cyanobacterial biomass. For TSItemp, but not for TSItrop, TSI values in relation to Chl-a and TP were also significantly different. All such deviations have important management implications especially when Chl-a, TP, and SDD are averaged in a single TSI, representing loss of information and less useful trophic state classifications. Our results demonstrate that tropical water bodies may respond to drivers of eutrophication differently than temperate systems, highlighting the need for more data to better inform management of these understudied ecosystems. As managers collect data from more tropical water bodies, regional models may offer even better understanding of factors influencing trophic state. (AU)

• Processo FAPESP: 18/21412-9 - Efeitos do lançamento de esgoto sanitário tratado por diferentes tecnologias sobre o funcionamento dos cursos de água receptores: retenção de nutrientes, metabolismo aquático e emissão de gases
• Beneficiário: Davi Gasparini Fernandes Cunha
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 18/13171-1 - Efeitos de fontes pontuais de poluição sobre a retenção de nutrientes em riachos tropicais: manipulação experimental da razão estequiométrica de nitrogênio e fósforo
• Beneficiário: Nícolas Reinaldo Finkler
• Modalidade de apoio: Bolsas no Brasil - Doutorado