Experimental manipulation of leaf litter colonization by aquatic invertebrates in a third order tropical stream

Abstract

Through a manipulative experiment, the colonization of leaf litter by invertebrates was investigated in two sections of a tropical stream (spatial scale) that differed in function of the canopy cover, one with the presence (closed area) and another without riparian vegetation (open area), during one month of the dry and one of the wet season (temporal scale). The work aimed to verify differences related to four variables: season, canopy cover, leaf type and leaf condition. Litter bags containing arboreal and herbaceous leaves (leaf type variable), non-conditioned and preconditioned (leaf condition variable) were placed at the bottom of the stream in each area (canopy cover variable) and season (dry and wet), and removed after 13-day colonization. The analysis of the remaining litter dry mass per leaf bag emphasizes differences related mainly to seasonality, canopy cover and leaf type, although leaf condition was also important when combined with those three factors. Comparing the abundance of invertebrates per treatment, there was a tendency of high predominance of Chironomidae during the dry season and greater taxa diversity and evenness during the wet season, when the water flow increase could alter the availability of microhabitats for local fauna. Even though canopy cover alone was not a significant source of variation in the abundance of invertebrates, the results showed a tendency of a combined effect of canopy cover with seasonality and leaf condition.Keywords: aquatic insects, leaf breakdown, headwater streams, seasonal variation, spatial variation. Manipulação experimental da colonização de detritos foliares por invertebrados aquáticos em um riacho tropical de 3ª ordem ResumoAtravés de um experimento de manipulação, a colonização de detritos foliares por invertebrados foi analisada em duas seções de um riacho tropical (escala espacial), que diferem em função da cobertura do dossel , um com a presença (área fechada) e outro sem vegetação ciliar (área aberta), durante um mês da estação seca e um da chuvosa (escala temporal). O trabalho teve como objetivo verificar as diferenças relacionadas a quatro variáveis: estação, cobertura vegetal, tipo e condição da folha. Sacos de náilon contendo folhas de uma planta arbórea e uma herbácea (tipo folha), não-condicionadas e pré-condicionadas (condição da folha) foram colocadas em cada área e estação do ano e removidos após 13 dias de colonização. A análise da massa seca remanescente dos detritos enfatizou diferenças relacionadas principalmente à sazonalidade, cobertura do dossel e tipo folha, embora a condição da folha também tenha sido importante quando combinado com esses três fatores. Comparando a abundância de invertebrados por tratamento, houve uma tendência de predominância de Chironomidae durante a estação seca e maior diversidade e equidade durante a estação chuvosa, quando o aumento do fluxo de água pode alterar a disponibilidade de micro-habitats para a fauna local. Apesar de cobertura do dossel sozinha não ter sido uma importante fonte de variaçã...

Organic matter dynamics in a savanna transition riparian zone: input of plant reproductive parts increases leaf breakdown process

“…The most abundant taxa were Tanypodinae, Chironominae, and Orthocladiinae, belonging to the family Chironomidae (Diptera). The dominance of Chironomidae is typical in tropical and temperate streams (Milošević et al, 2012;Biasi et al, 2013;Uieda and Carvalho, 2015) due to their high adaptive capacity for various environmental conditions (Anderson and Ferrington, 2012;Milošević et al, 2012). The low abundance of shredders (higher in August and November) and scrapers is also typical of tropical streams (Boyero et al, 2011(Boyero et al, , 2012.…”

Post-fire consequences for leaf breakdown in a tropical stream

“…This may also explain the importance of variation in autochthonous-allochthonous production to Cerrado stream metabolism (Lau et al, 2008;Rezende et al, 2017;Wagner et al, 2017). On the other hand, the decomposer community recovered quickly after fire (Rodríguez-Lozano et al, 2015), using the leaf litter mainly as a substrate (Rezende et al, 2016;Uieda & Carvalho, 2015). However, since long-term effects, were not investigated, they remain obscure for Cerrado (tropical) stream systems and thus warrant further investigation.…”

Efectos de las características de la hojarasca sobre la diversidad alfa y beta de ensambles de invertebrados en una cuenca hidrográfica tropical

“…However, our results should be interpreted with caution, since our findings are limited to invertebrate community associated with leaf breakdown. Canopy cover will also increase the exposed surface of the streams, increasing the water temperature and likely leading to a decrease in dissolved oxygen concentrations (Md Rawi et al 2013;Uieda and Carvalho 2015). Changes in the dissolved oxygen concentrations of streams may increase the levels of suspended sediments and soil erosion (Negishi et al 2006), deteriorating the physico-chemical parameters of the water and decreasing the overall invertebrate diversity (Dominguez-Granda et al 2011;Luiza-Andrade et al 2017).…”