Dean Jacobsen

Dean Jacobsen
University of Copenhagen · Freshwater Biological Laboratory, Department of Biology

PhD

About

124
Publications
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5,184
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Publications

Publications (124)
Article
Full-text available
The biodiversity of glacier-fed streams is particularly threatened by climate change, emphasising the need of monitoring these sentinel systems. The glacier-fed Saldur stream is an International Long Term Ecological Research (ILTER) site in the Italian Central Eastern Alps. Here, we sampled benthic macroinvertebrates and measured environmental vari...
Article
High altitude waters in the Ecuadorian Andes are devoid of native fish, but rainbow trout (Oncorhyn-chus mykiss) have been introduced widely. We surveyed 14 small and shallow, high altitude (3800 – 4300 m a.s.l.) lakes in Ecuador; seven lakes without fish, and seven with introduced rainbow trout. The main purpose of this study was to explore the ef...
Article
Global warming is expected to drive species toward higher altitudes. Indeed, most documented range shifts are upward, but observed shifts are often far from model predictions, and even downward shifts are common. Can such counterintuitive observations be explained? Metabolic oxygen demand rises with temperature in ectothermic animals, but levels of...
Article
In many mountainous areas, glaciers feed streams characterised by harsh environmental conditions, such as low water temperature, high turbidity, low channel stability, and high temporal variability in flow. Additionally, in many glacierised catchments, the mixture of streams arising from different water sources (glacier melt, groundwater, rainfall)...
Article
Full-text available
The effects of climate change in the tropical Andes are predicted to be devastating. While changes altering hydrology are already occurring, our knowledge of high-altitude lentic ecosystems is limited. Therefore, we carried out a survey of 16 small (0.06–7.1 ha) and shallow (≤ 6.5 m) fishless lakes, above the treeline in the Ecuadorian Andes (≤ 386...
Article
Full-text available
Currently, across the entire European river network, there are an estimated 0.74 barriers per kilometer of river length, with hydropower production being the main cause of riverine habitat fragmentation. On the one hand, policy actions have been proposed by different institutions to limit this impact. On the other hand, the compelling need to produ...
Article
Full-text available
The increasing incentives stemming from many international initiatives that target sustainable energy production have led to the global success of small hydropower plants. However, there is a growing debate about the actual environmental impact these structures have on riverine ecosystems, to the extent that some researchers argue that they could h...
Article
Full-text available
Microplastics have been detected in lake environments globally, including in remote regions. Agricultural and populated areas are known to congregate several inputs and release pathways for microplastic. This study investigated microplastic (50–5000 µm) contamination in five Danish freshwater lakes with catchments dominated by arable land use. The...
Article
The cover image is based on the Original Article Temperature and spatial connectivity drive patterns in freshwater macroinvertebrate diversity across the Arctic, by Jennifer Lento et al. https://doi.org/10.1111/fwb.13805.
Article
Full-text available
While river macroinvertebrates are the most widely used form of bioindicators, their baseline information, although crucial, is scarce in Nepal. The main objective of this study was to assess the macroinvertebrate assemblages in mountain tributaries of the glacial-fed Tamor and rain-fed Kamala rivers. A total of eight sites were sampled during Marc...
Article
Full-text available
Tropical Andean glaciers are retreating rapidly, with possible consequences for trophic structure and ecosystem processes in high Andean meltwater streams. Here, we measured the environmental characteristics, quantified pools of particulate organic matter (POM) and periphyton (Chl. a), sampled benthic macroinvertebrates, determined functional feedi...
Article
Anthropogenic inputs of nutrients and organic matter are common in tropical lowland rivers while little is known about the pollution-induced changes in oxygen availability and respiratory performance of ectotherms in these high temperature systems. We investigated the effects of agriculture and urban land-use on river water oxygen levels (diel meas...
Article
Full-text available
The cover image is based on the Original Article Aquatic biota responses to temperature in a high Andean geothermal stream, Estefania Quenta‐Herrera et al. https://doi.org/10.1111/fwb.13798.
Article
Freshwater consumers play a role in ecosystem nutrient cycling and dynamics by excreting metabolic waste products containing ammonium (NH4) and phosphate (PO4). In this study we quantified excretion of a selection of macroinvertebrate taxa and measured nutrient uptake metrics in a small Danish forest stream. Macroinvertebrate excretion was measured...
Article
Full-text available
• Warming in the Arctic is predicted to change freshwater biodiversity through loss of unique taxa and northward range expansion of lower latitude taxa. Detecting such changes requires establishing circumpolar baselines for diversity, and understanding the primary drivers of diversity. • We examined benthic macroinvertebrate diversity using a circu...
Article
Full-text available
The aim of this study is to generate a first global overview of pressures and methods used to assess the environmental quality of rivers and streams using macroinvertebrates. In total, 314 peer-review studies were reviewed, published in the period 1997 – 2018, from developing economies in Africa, South-Central America, Mexico and Southern Asia. To...
Article
Full-text available
1) The impact of global warming on mountain ecosystems is predicted to be high, and particularly in the tropical region. Geothermal streams have provided comprehensive evidence about how aquatic biodiversity changes across natural thermal gradients, but current knowledge is restricted to arctic and temperate zones. Thermal tolerances are different...
Article
Full-text available
Retreating glaciers, icons of climate change, release new potential habitats for both aquatic and terrestrial organisms. High-elevation species are threatened by temperature increases and the upward migration of lowlands species. Improving our understanding of successional processes after glacier retreat becomes urgent, especially in the tropics, w...
Article
Full-text available
Paul Colinvaux and his Ecuadorian student Miriam Steinitz-Kannan were the first modern scientists to study limnology in Ecuador in the 1960s and 1970s. Fifty years later, Steinitz-Kannan continues this research along with many collaborators, focusing on Andean, Amazonian, and Galapagos lakes, particularly their paleolimnology, physical/chemical par...
Article
Full-text available
Introduction: Glacierised catchments are remote and hostile environments, in which streams from different water sources (e.g., glacier melt, rain/snowmelt, groundwater) converge, creating a complex mosaic of stream sites with varying levels of glacial influence and environmental conditions. This environmental heterogeneity, in turn, influences the...
Article
Full-text available
Introduction: Glacierised catchments are remote and hostile environments, in which streams from different water sources (e.g., glacier melt, rain/snowmelt, groundwater) converge, creating a complex mosaic of stream sites with varying levels of glacial influence and environmental conditions. This environmental heterogeneity, in turn, influences the...
Article
Full-text available
Climate change is altering conditions in high-elevation streams worldwide, with largely unknown effects on resident communities of aquatic insects. Here, we review the challenges of climate change for high-elevation aquatic insects and how they may respond, focusing on current gaps in knowledge. Understanding current effects and predicting future i...
Article
We collected quantitative macroinvertebrate samples and measured environmental and geographical parameters at 13 sites: six along the main stem and seven in tributaries close to the main channel over a 700 m gradient in altitude and 22 km longitudinal distance along the River Kokra in the Slovenian Alps. Our objectives were 1) to compare longitudin...
Article
Full-text available
Glaciers are important drivers of environmental heterogeneity and biological diversity across mountain landscapes. Worldwide, glaciers are receding rapidly due to climate change, with important consequences for biodiversity in mountain ecosystems. However, the effects of glacier loss on biodiversity have never been quantified across a mountainous r...
Poster
Full-text available
The rapid melting of glacier cover is one of the most obvious impacts of climate change on alpine ecosystems and biodiversity. Our understanding of the impact of a decrease in glacier runoff on aquatic biodiversity is currently based on the “glacier-heterogeneity-diversity” paradigm, according to which there is high α-diversity at intermediate leve...
Article
Full-text available
Chironomidae (Diptera) are among the most diverse and widespread aquatic insects, with roughly 5,500 described species inhabiting an enormous variety of aquatic ecosystems, ranging from moist soils to lakes and rivers, and even marine ecosystems. Despite its ubiquity, the group remains underrepresented in studies addressing aquatic insect assemblag...
Article
• Land use changes can strongly influence stream ecosystems, yet these effects remain poorly documented in many hotspots of deforestation such as tropical Africa. The few studies conducted in this region have mostly focused on structural aspects of stream integrity; sparse data are available for key ecosystem processes such as ecosystem metabolism...
Article
Full-text available
Understanding metacommunity organisation in freshwater ecosystems is particularly important at high elevation in the tropical Andes, as this region is considered an important biodiversity hotspot with many endemic species threatened by climate change. High levels of dispersal at the regional scale and strong environmental filters at the local scale...
Article
Full-text available
Glaciers in the tropical Andes have been retreating for the past several decades, leading to a temporary increase in dry season water supply downstream. Projected future glacier shrinkage, however, will lead to a long-term reduction in dry season river discharge from glacierized catchments. This glacier retreat is closely related to the observed in...
Conference Paper
Full-text available
Mountain glaciers throughout the world are retreating; a trend that is expected to accelerate over the next several decades due to anthropogenic climate change. In some places glaciers are projected to completely disappear, while the area of frozen ground will diminish and the ratio of snow to rainfall will decrease. These changes will also affect...
Article
Danish streams have for some decades shown a significant improvement in ecological quality. This is based on a time-series of a subset of 247 sites from the nationwide monitoring program with reoccurring annual sampling. The ecological quality is determined using the benthic macroinvertebrate fauna as bio-indicators via the Danish Stream Fauna Inde...
Article
Glaciers in the tropical Andes have been retreating for the past several decades, leading to a temporary increase in dry season water supply downstream. Projected future glacier shrinkage, however, will lead to a long-term reduction in dry season river discharge from glacierized catchments. This glacier retreat is closely related to the observed in...
Article
Full-text available
Glaciers cover ∼10% of the Earth's land surface, but they are shrinking rapidly across most parts of the world, leading to cascading impacts on downstream systems. Glaciers impart unique footprints on river flow at times when other water sources are low. Changes in river hydrology and morphology caused by climate-induced glacier loss are projected...
Article
Full-text available
While the impacts of climate change on individual species and communities have been well documented there is little evidence on climate-mediated changes for entire ecosystems. Pristine alpine environments can provide unique insights into natural, physical and ecological response to climate change yet broad scale and long-term studies on these poten...
Data
Data spreadsheet of wetland cover and main predictors presented in Fig 7. (XLSX)
Data
List of LANDSAT images used in this study. The 738 PLEIADES images were 739 recorded the 2013-05-26 and 2013-06-03. (DOCX)
Data
Calibration between Pléiades and Landsat images. Regression coefficients (red line), slope values (labels on red dots), and root mean-square deviation (RMSE, blue curve) of the linear regressions between wetland areas calculated from Pléiades image and those calculated from Landsat images (N = 33 wetlands at different NDVI threshold values. (DOCX)
Data
Calculation of wetland fragmentation. Illustration of the different steps of the procedure used to calculate 747 individual wetland fragmentation over the period 1984–2011. (DOCX)
Article
Full-text available
The cryosphere in mountain regions is rapidly declining, a trend that is expected to accelerate over the next several decades due to anthropogenic climate change. A cascade of effects will result, extending from mountains to lowlands with associated impacts on human livelihood, economy, and ecosystems. With rising air temperatures and increased rad...
Article
Full-text available
The cryosphere in mountain regions is rapidly declining, a trend that is expected to accelerate over the next several decades due to anthropogenic climate change. A cascade of effects will result, extending from mountains to lowlands with associated impacts on human livelihood, economy, and ecosystems. With rising air temperatures and increased rad...
Article
In alpine regions worldwide, climate change is dramatically altering ecosystems and affecting biodiversity in many ways. For streams, receding alpine glaciers and snowfields, paired with altered precipitation regimes, are driving shifts in hydrology, species distributions, basal resources, and threatening the very existence of some habitats and bio...
Article
Full-text available
Glacier retreat is a worldwide phenomenon with important consequences for the hydrological cycle and downstream ecosystem structure and functioning. To determine the effects of glacier retreat on aquatic communities, we conducted a 4-year flow manipulation in a tropical glacier-fed stream. Compared with an adjacent reference stream, meltwater flow...
Data
Supplementary Figures 1-2, Supplementary Tables 1-2, Supplementary Notes 1-2 and Supplementary References
Article
Full-text available
The rapid melting of glacier cover is one of the most obvious impacts of climate change on alpine ecosystems and biodiversity. Our understanding of the impact of a decrease in glacier runoff on aquatic biodiversity is currently based on the glacier-heterogeneity-diversity' paradigm, according to which there is high -diversity at intermediate levels...
Article
Full-text available
We explored mechanisms determining the upper altitudinal limit of ephemeropterans from two different genera: Leptohyphes Eaton, 188215. Eaton, A.E. (1882), ʻAn Announcement of New Genera of the Ephemeridaeʼ, The Entomologist's Monthly Magazine, 18, 207–208.View all references (Leptohyphidae) and Lachlania Hagen, 186823. Hagen, H.A. (1868), ʻOn Lach...
Article
Full-text available
The latitudinal gradient in species richness of the European freshwater fauna is usually depicted as a contrasting pattern between lentic (standing waters) and lotic (running waters) habitats. Species richness decreases from South to North in lotic habitats, while lentic habitats show an intermediate richness peak in central Europe (Hof et al. 2008...
Article
The fast increase in temperature on the Tibetan Plateau, with anticipated future changes in aquatic ecosystems and biodiversity, highlights the urgent need for ecological data on the sparsely studied Tibetan running waters. In the present study we surveyed eight Tibetan streams to obtain data on densities, feeding selectivity and trophic position o...
Article
Full-text available
Under the ongoing climate change, understanding the mechanisms structuring the spatial distribution of aquatic species in glacial stream networks is of critical importance to predict the response of aquatic biodiversity in the face of glacier melting. In this study, we propose to use metacommunity theory as a conceptual framework to better understa...
Article
We revealed a history of legacy pesticides in water and sediment samples from 19 small streams across an agricultural landscape. Dominant legacy compounds included organochlorine pesticides, such as DDT and lindane, the organophosphate chlorpyrifos and triazine herbicides such as terbutylazine and simazine which have long been banned in the EU. The...
Article
Full-text available
1. Temperature and oxygen are recognised as the main drivers of altitudinal limits of species distributions. However, the two factors are linked, and both decrease with altitude, why their effects are difficult to disentangle. 2. This was experimentally addressed using aquatic macroinvertebrates; larvae of Andesiops (Ephemeroptera), Claudioperla, (...
Article
Full-text available
Knowledge on the ecology of streams at extreme altitudes is relatively sparse. We conducted a preliminary survey of the macroinvertebrate fauna of Tibetan streams in June 2009 and August 2011 and compared streams with different water sources. We collected quantitative samples of macroinvertebrates and measured physicochemical variables at 16 sites...
Article
We used equatorial glacier-fed streams as a model system to investigate the relationships between flow fluc- tuation and benthic fauna at different temporal scales. Water level was measured at 30 min intervals over 29 months (942 d) and benthic macroinvertebrates were sampled 14 times over the study period. We performed wavelet analyses on water-le...
Article
Full-text available
The hypotheses that beta diversity should increase with decreasing latitude and increase with spatial extent of a region have rarely been tested based on a comparative analysis of multiple datasets, and no such study has focused on stream insects. We first assessed how well variability in beta diversity of stream insect metacommunities is predicted...
Data
The hypotheses that beta diversity should increase with decreasing latitude and increase with spatial extent of a region have rarely been tested based on a comparative analysis of multiple datasets, and no such study has focused on stream insects. We first assessed how well variability in beta diversity of stream insect metacommunities is predicted...
Article
Full-text available
The hypotheses that beta diversity should increase with decreasing latitude and increase with spatial extent of a region have rarely been tested based on a comparative analysis of multiple datasets, and no such study has focused on stream insects. We first assessed how well variability in beta diversity of stream insect metacommunities is predicted...
Article
Full-text available
The hypotheses that beta diversity should increase with decreasing latitude and increase with spatial extent of a region have rarely been tested based on a comparative analysis of multiple datasets, and no such study has focused on stream insects. We first assessed how well variability in beta diversity of stream insect metacommunities is predicted...
Article
Full-text available
The hypotheses that beta diversity should increase with decreasing latitude and increase with spatial extent of a region have rarely been tested based on a comparative analysis of multiple datasets, and no such study has focused on stream insects. We first assessed how well variability in beta diversity of stream insect metacommunities is predicted...
Article
Full-text available
Among the objectives of the BIOTHAW project, the aquatic ecology part aims at characterizing the organization of aquatic communities living in high Andean bofedales with regards to several environmental and social factors that are rapidly changing under climate change. In this paper we propose a methodological framework for the analysis of aquatic...
Article
Full-text available
Alpine areas of the tropical Andes constitute the largest of all tropical alpine regions worldwide. They experience a particularly harsh climate, and they are fragmented into tropical alpine islands at various spatial scales. These factors generate unique patterns of continental insularity, whose impacts on biodiversity remain to be examined precis...