Mariana Meerhoff

Universidad de la República de Uruguay | UdelaR · Centro Universitario de la Región Este - CURE

Climate and hydrology are relevant control factors determining the timing and amount of nutrient losses from land to downstream aquatic systems, in particular of phosphorus (P) from agricultural lands. The main objective of the study was to evaluate the differences in P export patterns and the performance of alternative monitoring strategies in str...

Lakes can be sources or sinks of carbon, depending on local conditions. Recent studies have shown that the CO 2 efflux increases when lakes recover from eutrophication, mainly as a result of a reduction in phytoplankton biomass, leading to less uptake of CO 2 by producers. We hypothesised that lake restoration by removal of coarse fish (biomanipula...

Despite its well-established negative impacts on society and biodiversity, eutrophication continues to be one of the most pervasive anthropogenic influence along the freshwater to marine continuum. The interaction between eutrophication and climate change, particularly climate warming, was explicitly focused upon a decade ago in the paper by Moss e...

In this review we describe patterns and mechanisms by which habitat complexity is crucial for the functioning of shallow lakes and ponds, and for the abundance and diversity of biological communities in these ecosystems. Habitat complexity is affected by processes acting at different spatial scales, from the landscape to the ecosystem level (i.e.,...

Fluxes of carbon dioxide (CO2) and methane (CH4) in shallow lakes are strongly affected by dominant primary producers which mostly has been studied in temperate and boreal regions. We compared summer CO2 and CH4 fluxes (diffusion and ebullition) in littoral and pelagic zones of three subtropical shallow lakes with contrasting regimes: clear-vegetat...

The wicked nature of sustainability challenges facing food systems demands intentional and synergistic actions at multiple scales and sectors. The Southern Cone of Latin America, with its historical legacy of “feeding the world,” presents interesting opportunities for generating insights into potential trajectories and processes for food system tra...

Body size plays a key role in the functioning of communities and ecosystems. However, this ecological trait is commonly under strong selection pressure by environmental drivers, such as temperature, nutrients, predation, and food quality. Understanding how environmental factors interact to shape the body size structure of communities is, therefore,...

With 6 main basins, and being the second smallest country in South America, Uruguay has a high freshwater ecosystem diversity. The study of zooplankton communities dates back to 1949, but remained marginal until the end of the 20th century when the number of publications increased notably. Here, we revise the history and accumulated knowledge on th...

NON FORMATED PUBLISHED VERSION Feedbacks between climate change and eutrophication: revisiting the allied attack concept and how to strike back Despite its well-established negative impacts on society and biodiversity, eutrophication continues to be one of the most pervasive anthropogenic influence along the freshwater to marine continuum. The i...

Streams generally are affected by multiple stressors acting at different timescales. Periphyton, often the most important primary producer in these ecosystems , may respond to short-term impacts as well as to different long-term environmental conditions with potentially various changes in community structure. Here, we experimentally investigated th...

Anthropogenic stressors on aquatic environments change the relative importance of environmental conditions on spatial species distributions in a regional pool. One way to assess the spatial species distribution is measure the beta diversity. This study analyzed the difference in zooplankton beta diversity between natural lakes and artificial reserv...

In this review we describe patterns and mechanisms by which habitat complexity is crucial for the functioning of shallow lakes and ponds, and for the abundance and diversity of biological communities in these ecosystems. Habitat complexity is affected by processes acting at different spatial scales, from the landscape to the ecosystem level (i.e.,...

To investigate the potential long-term consequences of environmental warming in subtropical systems, we compare the trophic structure of shallow lakes in tropical and subtropical regions. In total, 25 meso-eutrophic lakes with piscivorous fish were sampled during summer along a latitudinal gradient in South America. The fish catch per unit of effor...

A recent paper by Beretta-Blanco and Carrasco-Letelier (2021) claims that agricultural eutrophication is not one of the main causes for cyanobacterial blooms in rivers and artificial reservoirs. By combining rivers of markedly different hydrological characteristics e.g., presence/absence and number of dams, river discharge and geological setting, t...

Newspaper interview.

Stream macroinvertebrate communities are modulated by different ecological processes that occur from the watershed to reaches and local sites, which can be directly or indirectly affected by human activities and changes in land use. This study evaluated the effects of water quality on macroinvertebrate structure in a low-impacted highland watershed...

The invasive freshwater dinoflagellate Ceratium furcoides is extending its distribution in South America with increasing environmental impacts associated with its bloom. We here report two events related to C. furcoides distribution expansion in Uruguay: (1) the main environmental drivers (physical and chemical factors, extreme wind events and zoop...

Climate-induced changes in precipitation and land-use intensification affect the discharge of streams worldwide, which, together with eutrophication and loss of riparian canopy, can affect periphyton biomass and composition, and therefore, ultimately the stream functioning. We investigated the responses of periphyton biomass and life-forms (i.e., h...

Warming, eutrophication, and increased omnivory by small-sized fish are global change processes that induce major effects on the food web structure and primary producers of shallow lakes. Despite the key relevance of phytoplankton and periphyton in freshwaters, the combined and potential synergistic effects of fish omnivory, warming and eutrophicat...

• Shallow aquatic systems exchange large amounts of carbon dioxide (CO2) and methane (CH4) with the atmosphere. The production and consumption of both gases is determined by the interplay between abiotic (such as oxygen availability) and biotic (such as community structure and trophic interactions) factors. • Fish communities play a key role in dri...

Global change drivers including eutrophication, hydrological disturbance, climate change, chemical pollution, overexploitation, invasive species, and land-use change are affecting the function and structure of freshwater ecosystems. South American freshwater ecosystems are especially threatened by the combination of rising human pressures on natura...

Despite there are multiple causes and consequences of eutrophication, this article analyses key aspects in the current context of Uruguay, emphasizing on cyanobacterial blooms as one of the most frequent and noticeable consequences. The worsening of eutrophication and its symptoms predicted with climate change, the keys for the reduction of diffuse...

Disentangling the effects of climate change on nature is one of the main challenges facing ecologists nowadays. Warmer climates forces strong effects on lake biota for fish, leading to a reduction in size, changes in diet, more frequent reproduction, and stronger cascading effects. Space-for-time substitution studies (SFTS) are often used to unrave...

Glyphosate herbicide is ubiquitously used in agriculture and weed control. It has now been identified in aquatic ecosystems worldwide, where numerous studies have suggested that it may have both suppressive and stimulatory effects on diverse non-target organisms. We cultured natural biofilms in a hypereutrophic environment to test the effects on pe...

In arid and semiarid regions, extreme temperature events and the frequency and duration of drought will increase toward 2050, leading to increased salinisation of inland waters, aggravated by catchment erosion and human activities (e.g., crop irrigation). With salinisation, a decline in biodiversity is expected, with potential negative effects on f...

Warming, eutrophication, and increased omnivory by fish are global change processes that induce major effects in the food web structure and primary producers of shallow lakes. Despite the key role of phytoplankton and periphyton in freshwaters, the combined and potential synergistic effects of fish omnivory, warming and eutrophication on these comm...

The invasive freshwater dinoflagellate Ceratium furcoides is extending its distribution in South America with increasing environmental impacts associated with its blooms. We here report two events related to C. furcoides distribution expansion in Uruguay: 1) the first appearance and main environmental drivers (physico-chemical variables, extreme wi...

In this study, we focused on the seasonal variation of the determinants of territory size in the weakly electric fish Gymnotus omarorum. This species is a seasonal breeder that displays year-round territorial aggression. Female and male dyads exhibit indistinguishable non-breeding territorial agonistic behavior and body size is the only significant...

This Special Issue of Inland Waters (featuring 2 Special Sections spread across 2 issues) celebrates the contribution of Brian Moss to the science and management of freshwater ecosystems. Brian passed away in 2016, and since then much has been written about his life and achievements (Carvalho and Johnes 2016, Irvine and Barker 2016, Jeppesen and Jo...

Interaction between non-native predatory fishes and native galaxiids (Pisces: Galaxiidae) shapes food web structure in Tasmanian lakes, Inland Waters, ABSTRACT Non-native fish invasions threaten native fauna and ecosystem functioning, not least in isolated island lakes. In Tasmania, where the native fish are mostly galaxiids, 9 non-native freshwate...

Nitrogen lost from agriculture has altered the geochemistry of the biosphere, with pronounced impacts on aquatic ecosystems. We aim to elucidate the patterns and driving factors behind the N fluxes in lowland stream ecosystems differing about land-use and climatic-hydrological conditions. The climate-hydrology areas represented humid cold temperate...

The expression of territorial behavior in wild species is especially suited to explore how animals integrate individual traits with dynamic environmental and social contexts. In this study, we focused on the seasonal variation of the determinants of territory size in the weakly electric fish Gymnotus omarorum . This species is a seasonal breeder th...

Sudden increases in temperature and turbidity in aquatic ecosystems are expected for different regions in the future, as a result of the predicted more frequent extreme climatic events. The consequences of these abrupt changes in the outcomes of predator-prey interactions are unknown. Here, we tested the effects of a heat wave and a turbidity pulse...

The Neotropics represent a hotspot for freshwater biodiversity with vast number of fish species of scarce ecological knowledge. This hold true for the Uruguay River, where fish assemblages and their diets remain unexplored. Fish assemblages were surveyed in 14 sites along its main course, from headwaters to mouth (approximately 1800 km), with the a...

Role of plant architecture on littoral macroinvertebrates in temperate and subtropical shallow lakes: a comparative manipulative field experiment We dedicate this paper to the late Maria Rosa Miracle, who was a key researcher in the shallow lakes community, always enthusiastically dedicated to science, and always ready to discuss and guide younger...

Hydrilla verticillata is a submerged, rooted macrophyte native to Asia and Australia, but currently attains broad distribution across all continents. Its success as an invasive species depends on the simultaneous influence of abiotic and biotic factors on different components of its performance. We conducted a factorial experiment to test the short...

Dormant stages (“resting eggs”) produced by cladocerans can persist for long periods of time in sediments and restore populations once the environmental conditions become favorable again. Lake Blanca, a subtropical shallow eutrophic lake, hosts a cladoceran community dominated by small-sized species. Previous studies on zooplankton resting eggs sug...

Predators play a key role in the functioning of shallow lakes. Differences between the response of temperate and subtropical systems to fish predation have been proposed, but experimental evidence is scarce. To elucidate cascading effects produced by predators in contrasting climatic zones, we conducted a mesocosm experiment in three pairs of lakes...

Differences in trophic web structure in otherwise similar ecosystems as a consequence of direct or indirect effects of ambient temperature differences can lead to changes in ecosystem functioning. Based on nitrogen and carbon stable isotope analysis, we compared the food-web structure in a series of subtropical (Uruguay, 30–35°S) and temperate (Den...

The maintenance of biodiversity in dynamic landscapes can be explained through the unifying concept of the metacommunity, an ecological system with a changing structure that arises from both the biotic features of its component species and from changing temporal processes. We evaluated the relative importance of environmental factors and spatial fa...

One of the most prominent manifestations of the ongoing climate warming is the retreat of glaciers and ice sheets around the world. Retreating glaciers result in the formation of new ponds and lakes, which are available for colonization. The gradual appearance of these new habitat patches allows us to determine to what extent the composition of ase...

The relationships between fish composition, connectivity and morphometry of 103 lagoons in nine freshwater ecoregions (FEOW) between 2·83∘ S and 37·64∘ S were evaluated in order to detect possible congruence between the gradient of species richness and similarities of assemblage composition. Most lagoons included in the study were <2 km2, with a ma...

Stable-isotope analysis is widely used in aquatic ecosystem studies to evaluate trophic structure and resource dynamics. Because δ 15 N values vary in freshwater systems, e.g., reflecting variations in land use, suitable baseline indicators must be specified. Few investigators have identified specific baseline organisms based on thorough and method...

The maintenance of biodiversity in dynamic landscapes can be explained through the unifying concept of the metacommunity, an ecological system with a changing structure that arises from both the biotic features of its component species and from changing temporal processes. We evaluated the relative importance of environmental factors and spatial fa...

Transformation of the natural land cover is one of the most important global changes. Changes in land use may strongly affect ecosystem functions and biodiversity by directly or indirectly modifying key structural properties. Here, we examined the effects of land use on the size structure of fish communities in subtropical Uruguayan streams. We ana...

The trophic structure of fish assemblages often varies seasonally, following the changes in food availability and supposedly water temperature. To unveil potential drivers of trophic shifts, we studied changes in fish trophic structure at both whole-assemblage and species levels at contrasting food availability and water temperatures in a subtropic...

The characteristics of riparian vegetation along streams vary with natural and anthropogenic factors. Deforestation for agricultural purposes has consequences for the physical in-stream structure and function, such as the predominance of autotrophic or heterotrophic stream metabolism. Open canopy lowland streams are often dominated by macrophytes,...

Agricultural land covers approximately 40% of Earth’s land surface and affects hydromorphological, biogeochemical and ecological characteristics of fluvial networks. In the northern temperate region, agriculture also strongly affects the amount and molecular composition of dissolved organic matter (DOM), which constitutes the main vector of carbon...

Recent studies provide compelling evidence for the idea that creative thinking draws upon two kinds of processes linked to distinct physiological features, and stimulated under different conditions. In short, the fast system-I produces intuition whereas the slow and deliberate system-II produces reasoning. System-I can help see novel solutions and...

Dissolved organic matter (DOM) is an important factor in aquatic ecosystems, which is involved in a large variety of biogeochemical and ecological processes, and recent literature suggests that it could be strongly affected by agriculture in different climates. Based on novel monitoring techniques, we investigated the interaction of climate and agr...

1. Stable isotope analyses of carbon and nitrogen are widely used to study food web structure in ecosystems. However, isotopic signatures are affected by the often-needed chemical preservation of tissues in the field, which impedes or weakens the interpretation of results. The scarcely available correction factors for preserved fish samples are spe...

Climate and hydrology are relevant control factors for determining the timing and amount of nutrient losses from agricultural fields to freshwaters. In this study, we evaluated the effect of agricultural intensification on the concentrations, dynamics 5 and export of phosphorus (P) in streams in two contrasting climate and hydrological regimes (tem...