Flavia Tromboni - Academia.edu (original) (raw)

Papers by Flavia Tromboni

Communications Earth & Environment

River metabolism and, thus, carbon cycling are governed by gross primary production and ecosystem... more River metabolism and, thus, carbon cycling are governed by gross primary production and ecosystem respiration. Traditionally river metabolism is derived from diel dissolved oxygen concentrations, which cannot resolve diel changes in ecosystem respiration. Here, we compare river metabolism derived from oxygen concentrations with estimates from stable oxygen isotope signatures (δ18O2) from 14 sites in rivers across three biomes using Bayesian inverse modeling. We find isotopically derived ecosystem respiration was greater in the day than night for all rivers (maximum change of 113 g O2 m−2 d−1, minimum of 1 g O2 m−2 d−1). Temperature (20 °C) normalized rates of ecosystem respiration and gross primary production were 1.1 to 87 and 1.5 to 22-fold higher when derived from oxygen isotope data compared to concentration data. Through accounting for diel variation in ecosystem respiration, our isotopically-derived rates suggest that ecosystem respiration and microbial carbon cycling in river...

Ecology and Evolution, 2021

This is an open access article under the terms of the Creative Commons Attribution License, which... more This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Water, 2021

Tonle Sap lake-river floodplain ecosystem (TSE) is one of the world’s most productive freshwater ... more Tonle Sap lake-river floodplain ecosystem (TSE) is one of the world’s most productive freshwater systems. Changes in hydrology, climate, population density, and land use influence water quality in this system. We investigated long term water quality dynamics (22 years) in space and time and identified potential changes in nutrient limitation based on nutrient ratios of inorganic nitrogen and phosphorus. Water quality was assessed at five sites highlighting the dynamics in wet and dry seasons. Predictors of water quality included watershed land use, climate, population, and water level. Most water quality parameters varied across TSE, except pH and nitrate that remained constant at all sites. In the last decade, there is a change in the chemical nutrient ratio suggesting that nitrogen may be the primary limiting nutrient across the system. Water quality was strongly affected by development in the watershed i.e., flooded forest loss, climatic variation, population growth, and change i...

Scientific Reports, 2021

Wildfire smoke often covers areas larger than the burned area, yet the impacts of smoke on nearby... more Wildfire smoke often covers areas larger than the burned area, yet the impacts of smoke on nearby aquatic ecosystems are understudied. In the summer of 2018, wildfire smoke covered Castle Lake (California, USA) for 55 days. We quantified the influence of smoke on the lake by comparing the physics, chemistry, productivity, and animal ecology in the prior four years (2014–2017) to the smoke year (2018). Smoke reduced incident ultraviolet-B (UV-B) radiation by 31% and photosynthetically active radiation (PAR) by 11%. Similarly, underwater UV-B and PAR decreased by 65 and 44%, respectively, and lake heat content decreased by 7%. While the nutrient limitation of primary production did not change, shallow production in the offshore habitat increased by 109%, likely due to a release from photoinhibition. In contrast, deep-water, primary production decreased and the deep-water peak in chlorophyll a did not develop, likely due to reduced PAR. Despite the structural changes in primary product...

Freshwater Science, 2019

Studies of the effects of landscape configuration on nutrient concentrations in aquatic systems, ... more Studies of the effects of landscape configuration on nutrient concentrations in aquatic systems, apart from land cover percentages, remain limited. Understanding these influences is important to guide land use planning and avoid the undesirable consequences of artificial eutrophication. We investigated how land use and natural landscape attributes such as edge density, mean shape index, cohesion, and contagion were related to nitrate (N-NO 3) and phosphate (P-PO 4) concentrations in Brazilian streams and Mexican lakes. Data on nutrient concentrations were collected by citizen science volunteers from 2013 to 2016, and we calculated land use classes and landscape metrics for each watershed. We developed models to predict nutrient concentrations based on landscape metrics, watershed slope, and season after excluding autocorrelated predictors. We used the Generalized Additive Model for Location, Shape and Scale framework and found the distribution (gamma or lognormal) that provided the best fit to the data based on the Akaike Information Criterion. The best predictors were selected following a stepwise strategy. We found relatively high N-NO 3 (5-10 mg/L) and P-PO 4 (0.5-1.0 mg/L) concentrations in the watersheds in both countries. Landscape composition (percentages of urban and agricultural areas) and configuration (mean shape indexes for urban and agricultural land use) metrics were the key predictors in the model for P-PO 4 in Brazilian streams. In Mexican lakes, the predictors of nutrient concentrations were configuration metrics such as contagion and edge density of natural areas for P-PO 4 , and cohesion of urban areas for N-NO 3. Our findings can be used as a starting point for land use planning, as well as for helping managers predict nutrient enrichment in watersheds within existing urban and agricultural areas. Our study highlights the importance of community-based monitoring that supplements regular monitoring initiatives because we were able to use data collected by citizen scientists to assess potential drivers of nutrient pollution and differences between countries.

Limnology and Oceanography Letters, 2017

Abundant living roots can be found in some streams and other shallow marine and freshwater habita... more Abundant living roots can be found in some streams and other shallow marine and freshwater habitats. A reach of a small Brazilian forested stream had 28% cover by live roots and exhibited diurnal trends in dissolved oxygen that could be attributed to gross primary production, but we hypothesized that activity of riparian tree roots in the channel caused this pattern. During sunny periods, trees transpire deoxygenated water from roots to the canopy but not in the dark, resulting in diurnal cycles of dissolved oxygen. Wholestream shading experiments showed that photosynthesis in the stream is not responsible for the pattern. Sealed chamber measurements showed living roots of riparian vegetation had substantial respiratory activity and ammonium and nitrate uptake, and rates per unit area were greater than sand and less than silt (the other two dominant substrata), indicating roots can substantially alter in-stream biogeochemistry. Whole-system metabolism (ecosystem respiration, ER, and gross primary production, GPP) is a central aquatic ecosystem function and is often used as an index of stream ecosystem health (Fellows et al. 2006; Correa-Gonz alez et al. 2014) and the trophic state (Dodds 2006, 2007). Metabolism is affected by natural features of the aquatic and terrestrial ecosystems (e.g., biofilms, light availability, canopy cover and rainfall) as well as by the impacts from anthropogenic activities (Wang et al. 2003; Frankforter et al. 2010). However, we know of little work on an additional biological component in some streams, living tree roots in the open channel. Streams and other aquatic habitats (e.g., lake shores, estuarine environments) can have exposed living roots associated with nearby vegetation. These roots and their associated biofilms might be an important component of benthic metabolism but their importance to whole systems is not well

BioScience, 2021

Nearshore (littoral) habitats of clear lakes with high water quality are increasingly experiencin... more Nearshore (littoral) habitats of clear lakes with high water quality are increasingly experiencing unexplained proliferations of filamentous algae that grow on submerged surfaces. These filamentous algal blooms (FABs) are sometimes associated with nutrient pollution in groundwater, but complex changes in climate, nutrient transport, lake hydrodynamics, and food web structure may also facilitate this emerging threat to clear lakes. A coordinated effort among members of the public, managers, and scientists is needed to document the occurrence of FABs, to standardize methods for measuring their severity, to adapt existing data collection networks to include nearshore habitats, and to mitigate and reverse this profound structural change in lake ecosystems. Current models of lake eutrophication do not explain this littoral greening. However, a cohesive response to it is essential for protecting some of the world's most valued lakes and the flora, fauna, and ecosystem services they su...

Water

Establishing reference conditions in rivers is important to understand environmental change and p... more Establishing reference conditions in rivers is important to understand environmental change and protect ecosystem integrity. Ranked third globally for fish biodiversity, the Mekong River has the world’s largest inland fishery providing livelihoods, food security, and protein to the local population. It is therefore of paramount importance to maintain the water quality and biotic integrity of this ecosystem. We analyzed land use impacts on water quality constituents (TSS, TN, TP, DO, NO3−, NH4+, PO43−) in the Lower Mekong Basin. We then used a best-model regression approach with anthropogenic land-use as independent variables and water quality parameters as the dependent variables, to define reference conditions in the absence of human activities (corresponding to the intercept value). From 2000–2017, the population and the percentage of crop, rice, and plantation land cover increased, while there was a decrease in upland forest and flooded forest. Agriculture, urbanization, and popu...

Journal of Limnology, May 22, 2018

Stream metabolism is affected by both natural and human-induced processes. While metabolism has m... more Stream metabolism is affected by both natural and human-induced processes. While metabolism has multiple implications for ecological processes, relatively little is known about how metabolic rates are influenced by land use in tropical streams. In this study, we assessed the metabolic characteristics and related environmental factors of six streams located in a transition area from Cerrado to Atlantic Forest (São Carlos/Brazil). Three streams were relatively preserved, while three were flowing through more agriculturally and/or urban impacted watersheds. Surface water samples were analyzed for biological and physico-chemical parameters as well as discharge and percentage of canopy cover. Metabolism was determined through the single-station method to estimate gross primary production (GPP), ecosystem respiration (ER) and net ecosystem production (NEP) with BAyesian Single-station Estimation (BASE). Nutrient concentrations tended to be higher in impacted versus preserved streams (e.g., average total phosphorus between 0.028-0.042 mg L-1 and 0.009-0.038 mg L-1 , respectively). Average canopy cover varied between 58 and 77%, with no significant spatial or seasonal variation. All streams were net heterotrophic (ER exceeded GPP) in all sampling periods. GPP rates were always lower than 0.7 gO 2 m-2 d-1 in all streams and ER varied from 0.6 to 42.1 gO 2 m-2 d-1. Linear Mixed-Effect models showed that depth, discharge, velocity and total phosphorus are the most important predictors for GPP. For ER, depth, velocity and canopy cover are significant potential predictors. Canopy cover was the main light limiting factor and influenced stream metabolism. Our findings reinforced the concepts that shifts in the shading effect provided by vegetation (e.g., through deforestation) or changes in discharge (e.g., through land use conversion or water abstractions) can impact freshwater metabolism. Our study suggests that human activities in low latitude areas can alter tropical streams' water quality, ecosystem function, and the degree of riparian influence. Our data showed that tropical streams can be especially responsive to increases of organic matter inputs leading to high respiration rates and net heterotrophy, and this should be considered to support management and restoration efforts.

Limnology and Oceanography: Methods

Frontiers in Ecology and the Environment

Fundamental and Applied Limnology

Ecosphere

Leaves, epilithon, macrophytes, and fine benthic organic material are central ecosystem compartme... more Leaves, epilithon, macrophytes, and fine benthic organic material are central ecosystem compartments to food webs and mediate nutrient fluxes in streams. Most estimates of gross primary production (GPP) and ecosystem respiration (ER) are made at a reach scale, averaging across compartments. Thus, there is little information on how individual compartments contribute to and scale up to wholestream estimates across watersheds. We compared estimates of GPP, ER, and nitrogen (N) uptake of individual ecosystem compartments (dm) and stream reaches (~100 m) in three sizes of streams in a preserved Atlantic Rainforest watershed. The smallest stream had dense forest canopy cover, whereas the largest was more open. We measured substratum-specific rates of GPP and ER, as well as ammonium and nitrate 15 N uptake in recirculating chambers. We compared these decimeter-scale measurements to whole-stream estimates, using single-station dissolved oxygen (GPP and ER) and pulsed N uptake methods. Epilithon and macrophytes (when present) were the dominant GPP and N uptake compartments in open-canopy sites, and leaves contributed strongly to ER at all sites, even though they covered <3 percent of the stream bottom. Ammonium and nitrate uptake per unit N content varied significantly among substrata and streams. Upscaled inorganic N uptake per unit area was greater when macrophytes were present. Chamber measurements overestimated metabolic rates in the larger streams, but not in the smallest one. The smallest transient storage zone streams were more active than the biggest one, and this influenced the mismatch between whole-stream and chamber nutrient uptake estimates. We conclude that scaling to the whole watershed requires information on location in the watershed (e.g., where canopy cover is dense), rates of individual compartments, and reach-specific hydrodynamic information as influenced by large-scale geomorphic details (i.e., the size and activity of the transient storage zones).