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Voysey MD, de Bruyn PJN, Davies AB. Are hippos Africa's most influential megaherbivore? A review of ecosystem engineering by the semi-aquatic common hippopotamus. Biol Rev Camb Philos Soc 2023; 98:1509-1529. [PMID: 37095627 DOI: 10.1111/brv.12960] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Revised: 03/30/2023] [Accepted: 04/03/2023] [Indexed: 04/26/2023]
Abstract
Megaherbivores perform vital ecosystem engineering roles, and have their last remaining stronghold in Africa. Of Africa's remaining megaherbivores, the common hippopotamus (Hippopotamus amphibius) has received the least scientific and conservation attention, despite how influential their ecosystem engineering activities appear to be. Given the potentially crucial ecosystem engineering influence of hippos, as well as mounting conservation concerns threatening their long-term persistence, a review of the evidence for hippos being ecosystem engineers, and the effects of their engineering, is both timely and necessary. In this review, we assess, (i) aspects of hippo biology that underlie their unique ecosystem engineering potential; (ii) evaluate hippo ecological impacts in terrestrial and aquatic environments; (iii) compare the ecosystem engineering influence of hippos to other extant African megaherbivores; (iv) evaluate factors most critical to hippo conservation and ecosystem engineering; and (v) highlight future research directions and challenges that may yield new insights into the ecological role of hippos, and of megaherbivores more broadly. We find that a variety of key life-history traits determine the hippo's unique influence, including their semi-aquatic lifestyle, large body size, specialised gut anatomy, muzzle structure, small and partially webbed feet, and highly gregarious nature. On land, hippos create grazing lawns that contain distinct plant communities and alter fire spatial extent, which shapes woody plant demographics and might assist in maintaining fire-sensitive riverine vegetation. In water, hippos deposit nutrient-rich dung, stimulating aquatic food chains and altering water chemistry and quality, impacting a host of different organisms. Hippo trampling and wallowing alters geomorphological processes, widening riverbanks, creating new river channels, and forming gullies along well-utilised hippo paths. Taken together, we propose that these myriad impacts combine to make hippos Africa's most influential megaherbivore, specifically because of the high diversity and intensity of their ecological impacts compared with other megaherbivores, and because of their unique capacity to transfer nutrients across ecosystem boundaries, enriching both terrestrial and aquatic ecosystems. Nonetheless, water pollution and extraction for agriculture and industry, erratic rainfall patterns and human-hippo conflict, threaten hippo ecosystem engineering and persistence. Therefore, we encourage greater consideration of the unique role of hippos as ecosystem engineers when considering the functional importance of megafauna in African ecosystems, and increased attention to declining hippo habitat and populations, which if unchecked could change the way in which many African ecosystems function.
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Affiliation(s)
- Michael D Voysey
- Department of Organismic and Evolutionary Biology, Harvard University, 22 Divinity Avenue, Cambridge, MA, 02138, USA
| | - P J Nico de Bruyn
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Private Bag X20, Hatfield, 0028, South Africa
| | - Andrew B Davies
- Department of Organismic and Evolutionary Biology, Harvard University, 22 Divinity Avenue, Cambridge, MA, 02138, USA
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Naz S, Mansouri B, Chatha AMM, Ullah Q, Abadeen ZU, Khan MZ, Khan A, Saeed S, Bhat RA. Water quality and health risk assessment of trace elements in surface water at Punjnad Headworks, Punjab, Pakistan. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2022; 29:61457-61469. [PMID: 35442001 DOI: 10.1007/s11356-022-20210-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Accepted: 04/08/2022] [Indexed: 06/14/2023]
Abstract
Pollution of the aquatic ecosystem due to different trace elements has become a global concern which has raised health-related issues for both aquatic and human life. Industrial and agricultural water run-off drained into the rivers and deposit trace elements in water, sediments and planktons. This study was designed to calculate the burden of trace elements such as aluminium (Al), arsenic (As), barium (Ba), and lead (Pb) in the river water of Punjnad Headworks, Bahawalpur, Punjab, Pakistan. Samples were collected from surface water, bed sediments and planktons during autumn, winter and spring seasons (September 2018 to May 2019). The results showed that the concentration of Pb was highest in surface water (453.87 mg L-1), while that of Al was highest in sediments (370.24 µg g-1) and plankton (315.05 µg g-1). A significant difference was found in metal concentrations among surface water, bed sediments and plankton at different sampling stations during various seasons. Importantly, the Exping (0.71, 1.23-3, 0.34, 0.02 for Pb, As, Al, and Ba, respectively) and Expderm (7.09-8, 1.2310, 3.42-8, and 2.48-9 for Pb, As, Al, and Ba, respectively) for trace elements were below 1.0 suggesting non-significant adverse effects of trace elements on human health. This study provided better understanding of various pollutants and their concentrations in water sources at the studied location.
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Affiliation(s)
- Saima Naz
- Department of Zoology, The Government Sadiq College Women University, Bahawalpur, Pakistan
| | - Borhan Mansouri
- Substance Abuse Prevention Research Center, Health Institute, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Ahmad Manan Mustafa Chatha
- Department of Entomology, Faculty of Agriculture and Environment, The Islamia University of Bahawalpur, Bahawalpur, Pakistan
| | - Qudrat Ullah
- Faculty of Veterinary and Animal Sciences, The University of Agriculture, Dera Ismail Khan, Pakistan
| | - Zain Ul Abadeen
- Department of Pathology, Faculty of Veterinary Science, University of Agriculture, 38040, Faisalabad, Pakistan.
| | - Muhammad Zahoor Khan
- Faculty of Veterinary and Animal Sciences, The University of Agriculture, Dera Ismail Khan, Pakistan
| | - Adnan Khan
- Shenzhen Branch, Guangdong Laboratory for Lingnan Modern Agriculture, Agriculture Genomics Institute at Shenzhen, Genome Analysis Laboratory of the Ministry of Agriculture, Chinese Academy of Agricultural Sciences, Shenzhen, 518000, China
| | - Saba Saeed
- Department of Zoology, The Government Sadiq College Women University, Bahawalpur, Pakistan
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Vegetation Greenness Trend in Dry Seasons and Its Responses to Temperature and Precipitation in Mara River Basin, Africa. ISPRS INTERNATIONAL JOURNAL OF GEO-INFORMATION 2022. [DOI: 10.3390/ijgi11080426] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The Mara River Basin of Africa has a world-famous ecosystem with vast vegetation, which is home to many wild animals. However, the basin is experiencing vegetation degradation and bad climate change, which has caused conflicts between people and wild animals, especially in dry seasons. This paper studied the vegetation greenness (VG), vegetation greenness trends (VGT), and their responses to climate change in dry seasons in the Mara River Basin, Africa. Firstly, based on Google Earth Engine (GEE) platform and Sentinel-2 images, the vegetation distribution map of the Mara River Basin was drawn. Then dry seasons MODIS NDVI data (January to February and June to September) were used to analyze the VGT. Finally, a random forest regression algorithm was used to evaluate the response of VG and VGT to temperature and precipitation derived from ERA5 from 2000 to 2019 at a resolution of 250 m. The results showed that the VGT was fluctuating in dry seasons, and the spatial differentiation was obvious. The greenness increasing trends both upstream and downstream were significantly larger than that of in the midstream. The responses of VG to precipitation were almost twice larger than temperature, and the responses of VGT to temperature were about 1.5 times larger than precipitation. The climate change trend of rising temperature and falling precipitation will lead to the degradation of vegetation and the reduction of crop production. There will be a vegetation degradation crisis in dry seasons in the Mara River Basin in the future. Identifying the spatiotemporal changes of VGT in dry seasons will be helpful to understand the response of VG and VGT to climate change and could also provide technical support to cope with climate-change-related issues for the basin.
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Masese FO, Fuss T, Bistarelli LT, Buchen-Tschiskale C, Singer G. Large herbivorous wildlife and livestock differentially influence the relative importance of different sources of energy for riverine food webs. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 828:154452. [PMID: 35278569 DOI: 10.1016/j.scitotenv.2022.154452] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Revised: 03/05/2022] [Accepted: 03/06/2022] [Indexed: 06/14/2023]
Abstract
In many regions of the world, large populations of native wildlife have declined or been replaced by livestock grazing areas and farmlands, with consequences for terrestrial-aquatic ecosystem connectivity and trophic resources supporting food webs in aquatic ecosystems. The river continuum concept (RCC) and the riverine productivity model (RPM) predict a shift of energy supplying aquatic food webs along rivers: from terrestrial inputs in low-order streams to autochthonous production in mid-sized rivers. In Afromontane-savanna landscapes, the shifting numbers of large mammalian wildlife present a physical continuum whose ecological implications for rivers is not clearly understood. Here, we studied the influence of replacing large wildlife (mainly hippos) with livestock on the fractional contribution of C3 vegetation, C4 grasses and periphyton on macroinvertebrates in the Mara River, which is an African montane-savanna river known to receive large subsidy fluxes of terrestrial organic matter and nutrients mediated by large mammalian herbivores (LMH), both wildlife and livestock, in its middle and lower reaches. Using stable carbon (δ13C) and nitrogen (δ15N) isotopes, we identified spatial patterns in the fractional contribution of allochthonous organic matter from C3 and C4 plants (woody vegetation and grasses, respectively) and autochthonous energy from periphyton for macroinvertebrates at various sites of the Mara River and its tributaries. Potential energy sources and invertebrates were sampled at 80 sites spanning stream orders 1 to 7, various catchment land uses (forest, agriculture and grasslands) and different loading rates of organic matter and nutrients by LMH (livestock and wildlife, i.e., hippopotamus). The fractional contribution of different sources of energy for macroinvertebrates along the river did not follow predictions of the RCC and RPM. First, the fractional contribution of C3 and C4 carbon was not related to river order or location along the fluvial continuum but to the loading of organic matter (dung) by both wildlife and livestock. Notably, C4 carbon was important for macroinvertebrates even in large river sections inhabited by hippos. Second, even in small 1st -3rd order forested streams, periphyton was a major source of energy for macroinvertebrates, and this was fostered by livestock inputs fuelling aquatic primary production throughout the river network. Importantly, our results show that replacing wildlife (hippos) with livestock shifts river systems towards greater reliance on autochthonous sources of energy through an algae-grazer pathway as opposed to reliance on allochthonous inputs of C4 carbon through a detrital pathway.
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Affiliation(s)
- Frank O Masese
- University of Eldoret, Department of Fisheries and Aquatic Science, P.O. Box 1125-30100, Eldoret, Kenya; Department of Ecohydrology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany.
| | - Thomas Fuss
- Department of Ecohydrology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany; Department of Ecology, University of Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
| | - Lukas Thuile Bistarelli
- Department of Ecohydrology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany; Department of Ecology, University of Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
| | - Caroline Buchen-Tschiskale
- Thünen Institute of Climate-Smart Agriculture, Bundesallee 65, 38116 Braunschweig, Germany; Leibniz Centre for Agricultural Landscape Research (ZALF), Eberswalder Straβe 84, 15374 Müncheberg, Germany
| | - Gabriel Singer
- Department of Ecohydrology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany; Department of Ecology, University of Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
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Misonou T, Nakanishi T, Tsuruta T, Shiribiki T, Sanada Y. Migration processes of radioactive cesium in the Fukushima nearshore area: Impacts of riverine input and resuspension. MARINE POLLUTION BULLETIN 2022; 178:113597. [PMID: 35366555 DOI: 10.1016/j.marpolbul.2022.113597] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Revised: 03/16/2022] [Accepted: 03/20/2022] [Indexed: 06/14/2023]
Abstract
It is essential to evaluate secondary migration caused by riverine input and resuspension from seabed sediments to estimate the future distribution of radioactive cesium (137Cs) in the coastal area off Fukushima Prefecture. In particular, the inflow from rivers cannot be ignored because most of the 137Cs inflow from rivers is deposited on the coast without elute into seawater. Two mooring systems were installed near the Ukedo River's mouth (Fukushima Prefecture) from February 2017 to February 2018. The first contained a sediment trap system, collecting sinking particles during the period. The second comprised a turbidity sensor and a current sensor. The contribution of resuspension and inflow from the river to the mass flux was quantitatively evaluated using multiple regression equations. The results showed that resuspension caused 79%-83% of secondary 137Cs migration in nearshore areas, whereas the influence of riverine 137Cs input on the sediment was only 7% per year.
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Affiliation(s)
- Toshiharu Misonou
- Sector of Fukushima Research and Development, Japan Atomic Energy Agency, 45-169, Kaihama-sukakeba, Minamisoma, Fukushima 975-0036, Japan.
| | - Takahiro Nakanishi
- Sector of Fukushima Research and Development, Japan Atomic Energy Agency, 45-169, Kaihama-sukakeba, Minamisoma, Fukushima 975-0036, Japan
| | - Tadahiko Tsuruta
- Sector of Fukushima Research and Development, Japan Atomic Energy Agency, 45-169, Kaihama-sukakeba, Minamisoma, Fukushima 975-0036, Japan
| | - Takehiko Shiribiki
- Sanyo Techno Marine, 1-3-17, Horidomecho, Nihonbashi, Chuouku, Tokyo 103-0012, Japan
| | - Yukihisa Sanada
- Sector of Fukushima Research and Development, Japan Atomic Energy Agency, 45-169, Kaihama-sukakeba, Minamisoma, Fukushima 975-0036, Japan
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Nakangu NF, Masese FO, Barasa JE, Matolla GK, Riziki JW, Mbalassa M. Influence of the changing environment on food composition and condition factor in Labeo victorianus (Boulenger, 1901) in rivers of Lake Victoria Basin, Kenya. AQUACULTURE AND FISHERIES 2021. [DOI: 10.1016/j.aaf.2021.09.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Iteba JO, Hein T, Singer GA, Masese FO. Livestock as vectors of organic matter and nutrient loading in aquatic ecosystems in African savannas. PLoS One 2021; 16:e0257076. [PMID: 34495982 PMCID: PMC8425544 DOI: 10.1371/journal.pone.0257076] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Accepted: 08/23/2021] [Indexed: 11/19/2022] Open
Abstract
Populations of large wildlife have declined in many landscapes around the world, and have been replaced or displaced by livestock. The consequences of these changes on the transfer of organic matter (OM) and nutrients from terrestrial to aquatic ecosystems are not well understood. We used behavioural data, excretion and egestion rates and C: N: P stoichiometry of dung and urine of zebu cattle, to develop a metabolism-based estimate of loading rates of OM (dung), C, N and P into the Mara River, Kenya. We also directly measured the deposition of OM and urine by cattle into the river during watering. Per head, zebu cattle excrete and/or egest 25.6 g dry matter (DM, 99.6 g wet mass; metabolism) - 27.7 g DM (direct input) of OM, 16.0-21.8 g C, 5.9-9.6 g N, and 0.3-0.5 g P per day into the river. To replace loading rates OM of an individual hippopotamus by cattle, around 100 individuals will be needed, but much less for different elements. In parts of the investigated sub-catchments loading rates by cattle were equivalent to or higher than that of the hippopotamus. The patterns of increased suspended materials and nutrients as a result of livestock activity fit into historical findings on nutrients concentrations, dissolved organic carbon and other variables in agricultural and livestock areas in the Mara River basin. Changing these patterns of carbon and nutrient transport and cycling are having significant effects on the structure and functioning of both terrestrial and aquatic ecosystems.
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Affiliation(s)
- Jacob O. Iteba
- Department of Hydrobiology and Aquatic Ecosystem Management, University of Natural Resources and Life Sciences, Vienna, Austria
- Department of Fisheries and Aquatic Sciences, University of Eldoret, Eldoret, Kenya
| | - Thomas Hein
- Department of Hydrobiology and Aquatic Ecosystem Management, University of Natural Resources and Life Sciences, Vienna, Austria
- WasserCluster Lunz, Lunz am See, Austria
| | - Gabriel A. Singer
- Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany
- Department of Ecology, University of Innsbruck, Innsbruck, Austria
| | - Frank O. Masese
- Department of Fisheries and Aquatic Sciences, University of Eldoret, Eldoret, Kenya
- Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany
- Aquatic Science and Ecosystems Group, University of KwaZulu-Natal, Scottsville, Pietermaritzburg, South Africa
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Regier PJ, González-Pinzón R, Van Horn DJ, Reale JK, Nichols J, Khandewal A. Water quality impacts of urban and non-urban arid-land runoff on the Rio Grande. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 729:138443. [PMID: 32498151 DOI: 10.1016/j.scitotenv.2020.138443] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 03/30/2020] [Accepted: 04/02/2020] [Indexed: 06/11/2023]
Abstract
Urban surface runoff from storms impacts the water quality dynamics of downstream ecosystems. While these effects are well-documented in mesic regions, they are not well constrained for arid watersheds, which sustain longer dry periods, receive intense but short-lived storms, and where stormwater drainage networks are generally isolated from sewage systems. We used a network of high-frequency in situ water quality sensors located along the Middle Rio Grande to determine surface runoff origins during storms and track rapid changes in physical, chemical, and biological components of water quality. Specific conductivity (SpCond) patterns were a reliable indicator of source, distinguishing between runoff events originating primarily in urban (SpCond sags) or non-urban (SpCond spikes) catchments. Urban events were characterized by high fluorescent dissolved organic matter (fDOM), low dissolved oxygen (including short-lived hypoxia <2 mg/L), smaller increases in turbidity and varied pH response. In contrast, non-urban events showed large turbidity spikes, smaller dissolved oxygen sags, and consistent pH sags. Principal component analysis distinguished urban and non-urban events by dividing physical and biogeochemical water quality parameters, and modeling of DO along the same reach demonstrated consistently higher oxygen demand for an urban event compared to a non-urban event. Based on our analysis, urban runoff poses more potential ecological harm, while non-urban runoff poses a larger problem for drinking water treatment. The comparison of our results to other reports of urban stormwater quality suggest that water quality responses to storm events in urban landscapes are consistent across a range of regional climates.
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Affiliation(s)
- Peter J Regier
- Department of Civil, Construction & Environmental Engineering, University of New Mexico, Albuquerque, NM 87131, USA.
| | - Ricardo González-Pinzón
- Department of Civil, Construction & Environmental Engineering, University of New Mexico, Albuquerque, NM 87131, USA
| | - David J Van Horn
- Department of Biology, University of New Mexico, Albuquerque 87131, USA
| | - Justin K Reale
- U.S. Army Corps of Engineers, Albuquerque District, Albuquerque 87109, USA
| | - Justin Nichols
- Department of Civil, Construction & Environmental Engineering, University of New Mexico, Albuquerque, NM 87131, USA
| | - Aashish Khandewal
- Department of Civil, Construction & Environmental Engineering, University of New Mexico, Albuquerque, NM 87131, USA
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Masese FO, Kiplagat MJ, González-Quijano CR, Subalusky AL, Dutton CL, Post DM, Singer GA. Hippopotamus are distinct from domestic livestock in their resource subsidies to and effects on aquatic ecosystems. Proc Biol Sci 2020; 287:20193000. [PMID: 32345142 PMCID: PMC7282896 DOI: 10.1098/rspb.2019.3000] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Accepted: 03/31/2020] [Indexed: 12/31/2022] Open
Abstract
In many regions of the world, populations of large wildlife have been displaced by livestock, and this may change the functioning of aquatic ecosystems owing to significant differences in the quantity and quality of their dung. We developed a model for estimating loading rates of organic matter (dung) by cattle for comparison with estimated rates for hippopotamus in the Mara River, Kenya. We then conducted a replicated mesocosm experiment to measure ecosystem effects of nutrient and carbon inputs associated with dung from livestock (cattle) versus large wildlife (hippopotamus). Our loading model shows that per capita dung input by cattle is lower than for hippos, but total dung inputs by cattle constitute a significant portion of loading from large herbivores owing to the large numbers of cattle on the landscape. Cattle dung transfers higher amounts of limiting nutrients, major ions and dissolved organic carbon to aquatic ecosystems relative to hippo dung, and gross primary production and microbial biomass were higher in cattle dung treatments than in hippo dung treatments. Our results demonstrate that different forms of animal dung may influence aquatic ecosystems in fundamentally different ways when introduced into aquatic ecosystems as a terrestrially derived resource subsidy.
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Affiliation(s)
- Frank O. Masese
- Department of Fisheries and Aquatic Sciences, University of Eldoret, P.O. Box 1125-30100, Eldoret, Kenya
- Department of Ecohydrology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany
| | - Mary J. Kiplagat
- Department of Fisheries and Aquatic Sciences, University of Eldoret, P.O. Box 1125-30100, Eldoret, Kenya
| | | | - Amanda L. Subalusky
- Department of Biology, University of Florida, Gainesville, FL 32611, USA
- Department of Ecology and Evolutionary Biology, Yale University, 165 Prospect Street, New Haven, CT 06511, USA
| | - Christopher L. Dutton
- Department of Ecology and Evolutionary Biology, Yale University, 165 Prospect Street, New Haven, CT 06511, USA
| | - David M. Post
- Department of Ecology and Evolutionary Biology, Yale University, 165 Prospect Street, New Haven, CT 06511, USA
| | - Gabriel A. Singer
- Department of Ecohydrology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany
- Department of Ecology, University of Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
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A Regression-Based Prediction Model of Suspended Sediment Yield in the Cuyahoga River in Ohio Using Historical Satellite Images and Precipitation Data. WATER 2020. [DOI: 10.3390/w12030881] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Urbanization typically results in increased imperviousness which alters suspended sediment yield and impacts geomorphic and ecological processes within urban streams. Therefore, there is an increasing interest in the ability to predict suspended sediment yield. This study assesses the combined impact of urban development and increased precipitation on suspended sediment yield in the Cuyahoga River using statistical modeling. Historical satellite-based land-cover data was combined with precipitation and suspended sediment yield data to create a Multiple Linear Regression (MLR) model for the Cuyahoga watershed. An R2 value of 0.71 was obtained for the comparison between the observed and predicted results based on limited land-use and land-cover data. The model also shows that every 1 mm increase in the mean annual precipitation has the potential to increase the mean annual suspended sediment yield by 860 tons/day. Further, a 1 km2 increase in developed land area has the potential to increase mean annual suspended sediment yield by 0.9 tons/day. The framework proposed in this study provides decision makers with a measure for assessing the potential impacts of future development and climate alteration on water quality in the watershed and implications for stream stability, dam and flood management, and in-stream and near-stream infrastructure life.
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Bregoli F, Crosato A, Paron P, McClain ME. Humans reshape wetlands: Unveiling the last 100 years of morphological changes of the Mara Wetland, Tanzania. THE SCIENCE OF THE TOTAL ENVIRONMENT 2019; 691:896-907. [PMID: 31326813 DOI: 10.1016/j.scitotenv.2019.07.189] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Revised: 07/10/2019] [Accepted: 07/12/2019] [Indexed: 06/10/2023]
Abstract
The Lower Mara River and Wetland, Tanzania, is an important ecosystem and unique water resource for a vast semi-arid area. The river, an affluent of Lake Victoria, and the wetland are experiencing morphological and vegetation changes resulting in channel avulsions and wetland expansion. This study analyses the changes over the last 100 years and investigates natural and anthropogenic behaviors to explain the increase of the Mara Wetland area. We collated historical topographic maps and satellite images. We conducted two field surveys in low and high flow condition with an unmanned aerial vehicle, a sonar and an ADCP. We mapped selected areas as well as the bed topography in some stretches of the river, measured discharges, and collected river bed and suspended sediment samples. The analysis of the sediments shows that the wetland system, dominated by papyrus sp., is very efficient in trapping sediment, releasing clear water to the Lake Victoria. The historical reconstruction using topographic maps, satellite images and a multivariable analysis including hydrology and land cover, shows that 4 major avulsions occurred in the last 70 years due to a combination of natural behaviors, hydrological fluctuations and anthropogenic factors such as basin deforestation, farming and grazing along the river banks and in the wetland. Each avulsion led to substantial expansion of the wetland. Combined, they increased the wetland area by a factor of 3.6. Describing the Lower Mara River dynamic behavior, this work provides relevant information for sustainable future water and sediment management in order to preserve wetland habitats and natural resources.
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Affiliation(s)
- F Bregoli
- Department of Water Science and Engineering, IHE Delft Institute for Water Education, Westvest 7, 2611 AX, Delft, the Netherlands.
| | - A Crosato
- Department of Water Science and Engineering, IHE Delft Institute for Water Education, Westvest 7, 2611 AX, Delft, the Netherlands; Faculty of Civil Engineering and Geosciences, Delft University of Technology, Building 23, Stevinweg 1, 2628 CN, Delft, the Netherlands
| | - P Paron
- Department of Water Science and Engineering, IHE Delft Institute for Water Education, Westvest 7, 2611 AX, Delft, the Netherlands
| | - M E McClain
- Department of Water Science and Engineering, IHE Delft Institute for Water Education, Westvest 7, 2611 AX, Delft, the Netherlands; Faculty of Civil Engineering and Geosciences, Delft University of Technology, Building 23, Stevinweg 1, 2628 CN, Delft, the Netherlands
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Dutton CL, Subalusky AL, Hill TD, Aleman JC, Rosi EJ, Onyango KB, Kanuni K, Cousins JA, Staver AC, Post DM. A 2000-year sediment record reveals rapidly changing sedimentation and land use since the 1960s in the Upper Mara-Serengeti Ecosystem. THE SCIENCE OF THE TOTAL ENVIRONMENT 2019; 664:148-160. [PMID: 30739850 DOI: 10.1016/j.scitotenv.2019.01.421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Revised: 01/29/2019] [Accepted: 01/31/2019] [Indexed: 06/09/2023]
Abstract
The Mara River basin is a trans-boundary basin of international importance. It forms the headwaters of the Nile River and serves as the primary dry season water source for an estimated 1.1 million rural people and the largest remaining overland migration of 1.4 million wildebeest in the Serengeti-Mara Ecosystem. Changes throughout the basin are impacting the quantity and quality of the Mara River, yet the historical context of environmental conditions in the basin is not well known. We collected sediment cores throughout the wetland at the mouth of the Mara River, and we used isotopic dating methods and a suite of analyses to examine historical patterns of sediment quantity and source, mercury contamination, and carbon and nutrient loading. Our results show that ecological conditions in the Mara River basin were fairly stable over paleoecological time scales (2000-1000 years before present), but there has been a period of rapid change in the basin over the last 250 years, particularly since the 1960s. A shift in the source and quantity of sediments in the river began in the late 1700s and became much more pronounced in the 1950s and 1960s, coincident with increasing mercury concentrations. The quantity of sediment from the Upper Mara increased, particularly since 1960, but the proportion of total sediment from this region decreased as the Talek and Middle Mara portions of the basin began producing more sediment. The decadal oscillation in sediment accumulation was congruent with known periods of extreme precipitation events. Carbon and nitrogen loading also increased since the 1960s, and the shift in the isotopic ratio of nitrogen provides evidence for increased anthropogenic loading. Altogether, these data likely reflect patterns of change also experienced in other basins throughout East Africa.
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Affiliation(s)
- Christopher L Dutton
- Yale University, Department of Ecology and Evolutionary Biology, 165 Prospect St, New Haven, CT 06511, USA.
| | - Amanda L Subalusky
- Cary Institute of Ecosystem Studies, 2801 Sharon Turnpike, Millbrook, NY 12545, USA
| | - Troy D Hill
- South Florida Natural Resources Center, National Park Service, 950 N. Krome Avenue, Homestead, FL 33030, USA
| | - Julie C Aleman
- Yale University, Department of Ecology and Evolutionary Biology, 165 Prospect St, New Haven, CT 06511, USA
| | - Emma J Rosi
- Cary Institute of Ecosystem Studies, 2801 Sharon Turnpike, Millbrook, NY 12545, USA
| | | | - Kanuni Kanuni
- WWF-Tanzania, Plot No. 350, Regent Estate Mikocheni, Dar es Salaam, Tanzania
| | - Jenny A Cousins
- WWF-UK, The Living Planet Centre, Rufford House, Brewery Rd, Woking GU21 4LL, UK
| | - A Carla Staver
- Yale University, Department of Ecology and Evolutionary Biology, 165 Prospect St, New Haven, CT 06511, USA
| | - David M Post
- Yale University, Department of Ecology and Evolutionary Biology, 165 Prospect St, New Haven, CT 06511, USA
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Schoelynck J, Subalusky AL, Struyf E, Dutton CL, Unzué-Belmonte D, Van de Vijver B, Post DM, Rosi EJ, Meire P, Frings P. Hippos ( Hippopotamus amphibius): The animal silicon pump. SCIENCE ADVANCES 2019; 5:eaav0395. [PMID: 31049394 PMCID: PMC6494503 DOI: 10.1126/sciadv.aav0395] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 03/21/2019] [Indexed: 05/10/2023]
Abstract
While the importance of grasslands in terrestrial silicon (Si) cycling and fluxes to rivers is established, the influence of large grazers has not been considered. Here, we show that hippopotamuses are key actors in the savannah biogeochemical Si cycle. Through a detailed analysis of Si concentrations and stable isotope compositions in multiple ecosystem compartments of a savannah-river continuum, we constrain the processes influencing the Si flux. Hippos transport 0.4 metric tons of Si day-1 by foraging grass on land and directly egesting in the water. As such, they bypass complex retention processes in secondary soil Si pools. By balancing internal processes of dissolution and precipitation in the river sediment, we calculate that hippos affect up to 76% of the total Si flux. This can have a large impact on downstream lake ecosystems, where Si availability directly affects primary production in the diatom-dominated phytoplankton communities.
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Affiliation(s)
- Jonas Schoelynck
- University of Antwerp, Department of Biology, Ecosystem Management Research Group, Universiteitsplein 1C, B-2610 Wilrijk, Belgium
| | - Amanda L Subalusky
- Cary Institute of Ecosystem Studies, Millbrook, NY, USA
- Yale University, Department of Ecology and Evolutionary Biology, New Haven, CT, USA
| | - Eric Struyf
- University of Antwerp, Department of Biology, Ecosystem Management Research Group, Universiteitsplein 1C, B-2610 Wilrijk, Belgium
| | - Christopher L Dutton
- Yale University, Department of Ecology and Evolutionary Biology, New Haven, CT, USA
| | - Dácil Unzué-Belmonte
- University of Antwerp, Department of Biology, Ecosystem Management Research Group, Universiteitsplein 1C, B-2610 Wilrijk, Belgium
| | - Bart Van de Vijver
- University of Antwerp, Department of Biology, Ecosystem Management Research Group, Universiteitsplein 1C, B-2610 Wilrijk, Belgium
- Botanic Garden Meise, Nieuwelaan 38, 1860 Meise, Belgium
| | - David M Post
- Yale University, Department of Ecology and Evolutionary Biology, New Haven, CT, USA
| | - Emma J Rosi
- Cary Institute of Ecosystem Studies, Millbrook, NY, USA
| | - Patrick Meire
- University of Antwerp, Department of Biology, Ecosystem Management Research Group, Universiteitsplein 1C, B-2610 Wilrijk, Belgium
| | - Patrick Frings
- Department of Geosciences, Swedish Museum of Natural History, Box 50007, Stockholm, Sweden
- Section 3.3 Earth Surface Geochemistry, GFZ German Research Centre for Geosciences, Telegrafenberg, Potsdam, Germany
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Subalusky AL, Dutton CL, Njoroge L, Rosi EJ, Post DM. Organic matter and nutrient inputs from large wildlife influence ecosystem function in the Mara River, Africa. Ecology 2018; 99:2558-2574. [PMID: 30179253 DOI: 10.1002/ecy.2509] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Revised: 07/19/2018] [Accepted: 07/27/2018] [Indexed: 11/11/2022]
Abstract
Animals can be important vectors for the movement of resources across ecosystem boundaries. Animals add resources to ecosystems primarily through egestion, excretion, and carcasses, and the stoichiometry and bioavailability of these inputs likely interact with characteristics of the recipient ecosystem to determine their effects on ecosystem function. We studied the influence of hippopotamus excretion/egestion and wildebeest carcasses, and their interactions with discharge, in the Mara River, Kenya. We measured nutrient dissolution and decomposition rates of wildlife inputs, the influence of inputs on nutrient concentrations and nutrient limitation in the river and the influence of inputs on biofilm growth and function in both experimental streams and along a gradient of inputs in the river. We found that hippopotamus excretion/egestion increases ammonium and coarse particulate organic matter in the river, and wildebeest carcasses increase ammonium, soluble reactive phosphorus, and total phosphorus. Concentrations of dissolved carbon and nutrients in the water column increased along a gradient of wildlife inputs and during low discharge, although concentrations of particulate carbon decreased during low discharge due to deposition on the river bottom. Autotrophs were nitrogen limited and heterotrophs were carbon limited and nitrogen and phosphorus colimited upstream of animal inputs but there was no nutrient limitation downstream of inputs. In experimental streams, hippo and wildebeest inputs together increased biofilm gross primary production (GPP) and respiration (R). These results differed in the river, where low concentrations of hippo inputs increased gross primary production (GPP) and respiration (R) of biofilms, but high concentrations of hippo inputs in conjunction with wildebeest inputs decreased GPP. Our research shows that inputs from large wildlife alleviate nutrient limitation and stimulate ecosystem metabolism in the Mara River and that the extent to which these inputs subsidize the ecosystem is mediated by the quantity and quality of inputs and discharge of the river ecosystem. Thus, animal inputs provide an important ecological subsidy to this river, and animal inputs were likely important in many other rivers prior to the widespread extirpation of large wildlife.
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Affiliation(s)
- Amanda L Subalusky
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, 06511, USA.,Cary Institute of Ecosystem Studies, Millbrook, New York, 12545, USA
| | - Christopher L Dutton
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, 06511, USA
| | - Laban Njoroge
- Invertebrate Zoology Section, National Museums of Kenya, Nairobi, Kenya
| | - Emma J Rosi
- Cary Institute of Ecosystem Studies, Millbrook, New York, 12545, USA
| | - David M Post
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, 06511, USA
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Subalusky AL, Post DM. Context dependency of animal resource subsidies. Biol Rev Camb Philos Soc 2018; 94:517-538. [DOI: 10.1111/brv.12465] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Revised: 08/24/2018] [Accepted: 08/30/2018] [Indexed: 12/01/2022]
Affiliation(s)
- Amanda L. Subalusky
- Department of Ecology and Evolutionary Biology Yale University New Haven CT 06511 U.S.A
- Cary Institute of Ecosystem Studies Millbrook NY 12545 U.S.A
| | - David M. Post
- Department of Ecology and Evolutionary Biology Yale University New Haven CT 06511 U.S.A
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Dutton CL, Subalusky AL, Hamilton SK, Rosi EJ, Post DM. Organic matter loading by hippopotami causes subsidy overload resulting in downstream hypoxia and fish kills. Nat Commun 2018; 9:1951. [PMID: 29769538 PMCID: PMC5956076 DOI: 10.1038/s41467-018-04391-6] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Accepted: 04/20/2018] [Indexed: 11/18/2022] Open
Abstract
Organic matter and nutrient loading into aquatic ecosystems affects ecosystem structure and function and can result in eutrophication and hypoxia. Hypoxia is often attributed to anthropogenic pollution and is not common in unpolluted rivers. Here we show that organic matter loading from hippopotami causes the repeated occurrence of hypoxia in the Mara River, East Africa. We documented 49 high flow events over 3 years that caused dissolved oxygen decreases, including 13 events resulting in hypoxia, and 9 fish kills over 5 years. Evidence from experiments and modeling demonstrates a strong mechanistic link between the flushing of hippo pools and decreased dissolved oxygen in the river. This phenomenon may have been more widespread throughout Africa before hippopotamus populations were severely reduced. Frequent hypoxia may be a natural part of tropical river ecosystem function, particularly in rivers impacted by large wildlife. Hypoxic (low oxygen) water conditions are generally thought to be uncommon in rivers and result from human impacts. However, Dutton and colleagues show here that waste from hippos in the Mara River contributes to frequent hypoxic events, suggesting hypoxia is a natural aspect of this system.
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Affiliation(s)
- Christopher L Dutton
- Department of Ecology and Evolutionary Biology, Yale University, 165 Prospect Street, New Haven, CT, 06511, USA.
| | | | - Stephen K Hamilton
- W.K. Kellogg Biological Station, Michigan State University, 3700 E. Gull Lake Drive, Hickory Corners, MI, 49060, USA.,Department of Integrative Biology, Michigan State University, 288 Farm Lane, East Lansing, MI, 48824, USA
| | - Emma J Rosi
- Cary Institute of Ecosystem Studies, Box AB, Millbrook, NY, 12545, USA
| | - David M Post
- Department of Ecology and Evolutionary Biology, Yale University, 165 Prospect Street, New Haven, CT, 06511, USA
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