Effect of leaf decomposition stage and water temperature on fragmentation activity of a shredder invertebrate species in lotic ecosystems

Abstract

ABSTRACT. The attractiveness of a given leaf detritus to invertebrates depends on the chemical composition, physical structure, stage of microbial colonization and decomposition level. In addition to the leaf detritus quality, water temperature also aff ects organic matter cycling in aquatic environments. In this context, the objectives of this study were: i) to increase knowledge about the role of invertebrate shredders on fragmenting senescent, conditioned senescent and green leaves of Richeria grandis Vahl. (Phyllanthaceae) under gradual temperature rise and check leaf mass loss; ii) to verify the preference of Phylloicus sp. (Trichoptera) for leaves for larval case production. The experiment I consisted of three treatments with diff erent water temperatures: 20°C, 24°C and 28°C. In the experiment II, we added 10 discs of green leaves of R. grandis and two shredder invertebrates (Phylloicus sp.) to each aquarium. Leaf mass loss in the presence or absence of fragmentation was not signifi cantly infl uenced by diff erences in the intraspecifi c quality of the detritus or temperature. Intraspecifi c quality of resources mixed with green leaves can lead to increased contact of phenolic content on senescent leaves, leading to a similarity in food exploitation by invertebrates. However, the production of larval cases by Phylloicus sp. seems to be dependent on the resistance presented by the resource rather than the phenolic content, thus leading the shredders to use signifi cantly more senescent detritus, regardless temperature.KEYWORDS. Microcosms, chemical composition, Phylloicus sp., warming of water.RESUMO. Efeito do estágio de decomposição foliar e temperatura da água sobre a atividade de fragmentação de uma espécie de invertebrado fragmentador em ecossistemas lóticos. A atratividade de um determinado detrito foliar pelos invertebrados depende da composição química, estrutura física, estágio de colonização microbiana e nível de degradação do detrito. Além da qualidade do detrito foliar, a temperatura da água tem sido outro fator que pode levar a variações na velocidade da ciclagem de matéria orgânica em ambientes aquáticos. Os objetivos deste estudo foram: i) ampliar os conhecimentos acerca do papel dos invertebrados fragmentadores sobre a atividade de fragmentação de folhas senescentes, senescentes condicionadas e verdes de Richeria grandis Vahl. (Phyllanthaceae) sob elevações graduais de temperatura e verifi car as possíveis consequências sobre a perda de massa foliar; ii) verifi car a preferência de recurso foliar para a construção de casulo pelo invertebrado fragmentador Phylloicus sp. (Trichoptera). O experimento I foi constituído de três tratamentos que se diferiram apenas na temperatura da água: Tratamento 1: 20°C, Tratamento 2: 24°C, Tratamento 3: 28°C. O experimento II se diferiu do I pelo acréscimo de dez discos de folhas verdes de R. grandis e dois invertebrados (Phylloicus sp.) em cada aquário. A perda de massa foliar na presença ou ausência de atividade de fragmentação não foi infl uenciada signif...

Effects of litter size and quality on processing by decomposers in a tropical savannah stream

“…, Martins et al . , Navarro & Gonçalves‐Jr ), supporting our hypothesis that invertebrates prefer larger fragments for case building. Our hypothesis that Phylloicus prefer higher quality litter was also supported, but we did not observe a preference for lower quality litter for case construction.…”

“…Smaller leaf litter sizes (fragmented or not) increase some nutrients (e.g., nitrogen) by microbial bioaccumulation and/ or invertebrate bioturbation due to a higher surface-area-tovolume ratio (Cornejo et al 1994, Rinkes et al 2014, Alvim et al 2015. Understanding the influence of litter size may contribute to our general understanding of processes that have previously been observed in savannahs, including: i) a decrease in leaf size resulting from global warming (see also Silverio et al 2013) and ii) the increase in biological leaf fragmentation due to higher activity of shredder invertebrates also in response to global warming (see also Navarro et al 2013, Navarro & Gonc ßalves-Jr 2017.…”

“…Shredder invertebrates are specialized to process allochthonous detritus in tropical streams, and several experimental studies have investigated the influence of shredders on litter breakdown (Nolen & Pearson 1993, Cheshire et al 2005, Boyero & Pearson 2006, Casotti et al 2014, Kiffer et al 2016, particularly in caddisflies of the genus Phylloicus (Muller, 1880; Rinc on & Mart ınez 2006, Moretti et al 2009, Navarro et al 2013, Vidovix et al 2013, Casotti et al 2014, Leite et al 2016, Navarro & Gonc ßalves-Jr 2017. Phylloicus (Calamoceratidae: Trichoptera) is a caddisfly genus with daytime and crepuscular activity of which there are 17 known species in Brazil (Paprocki & Franc ßa 2014).…”

“…) and ii) the increase in biological leaf fragmentation due to higher activity of shredder invertebrates also in response to global warming (see also Navarro et al . , Navarro & Gonçalves‐Jr ).…”

“…, Martins et al . , Navarro & Gonçalves‐Jr ). Phylloicus (Calamoceratidae: Trichoptera) is a caddisfly genus with daytime and crepuscular activity of which there are 17 known species in Brazil (Paprocki & França ).…”