Pierre Denis Plisnier - Academia.edu (original) (raw)

Papers by Pierre Denis Plisnier

Research paper thumbnail of Etude de la biologie des espèces de poissons exploités dans le lac Ihema (Bassin de l'Akagera) au Rwanda

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Research paper thumbnail of Global data set of long-term summertime vertical temperature profiles in 153 lakes

Scientific Data

Climate change and other anthropogenic stressors have led to long-term changes in the thermal str... more Climate change and other anthropogenic stressors have led to long-term changes in the thermal structure, including surface temperatures, deepwater temperatures, and vertical thermal gradients, in many lakes around the world. Though many studies highlight warming of surface water temperatures in lakes worldwide, less is known about long-term trends in full vertical thermal structure and deepwater temperatures, which have been changing less consistently in both direction and magnitude. Here, we present a globally-expansive data set of summertime in-situ vertical temperature profiles from 153 lakes, with one time series beginning as early as 1894. We also compiled lake geographic, morphometric, and water quality variables that can influence vertical thermal structure through a variety of potential mechanisms in these lakes. These long-term time series of vertical temperature profiles and corresponding lake characteristics serve as valuable data to help understand changes and drivers of...

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Research paper thumbnail of Food Web Dynamics in Stable Isotope Ecology

Measurement, Analysis, Simulation, 2003

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Research paper thumbnail of Analysis of trophic relationships in two shallow equatorial lakes Lake Naivasha (Kenya) and Lake Ihema (Rwanda) using a multispecifies trophic model

Hydrobiologia, 1996

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Research paper thumbnail of Deeper waters are changing less consistently than surface waters in a global analysis of 102 lakes

Scientific Reports

Globally, lake surface water temperatures have warmed rapidly relative to air temperatures, but c... more Globally, lake surface water temperatures have warmed rapidly relative to air temperatures, but changes in deepwater temperatures and vertical thermal structure are still largely unknown. We have compiled the most comprehensive data set to date of long-term (1970–2009) summertime vertical temperature profiles in lakes across the world to examine trends and drivers of whole-lake vertical thermal structure. We found significant increases in surface water temperatures across lakes at an average rate of + 0.37 °C decade−1, comparable to changes reported previously for other lakes, and similarly consistent trends of increasing water column stability (+ 0.08 kg m−3 decade−1). In contrast, however, deepwater temperature trends showed little change on average (+ 0.06 °C decade−1), but had high variability across lakes, with trends in individual lakes ranging from − 0.68 °C decade−1 to + 0.65 °C decade−1. The variability in deepwater temperature trends was not explained by trends in either s...

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Research paper thumbnail of Composition and seasonal variations in abundance of Copepod (Crustacea) populations from the northern part of Lake Tanganyika

Aquatic Ecosystem Health & Management

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Research paper thumbnail of Phytoplankton communities in the crater lakes of western Uganda, and their indicator species in relation to lake trophic status

Ecological Indicators

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Research paper thumbnail of Evaluating TMPA Rainfall over the Sparsely Gauged East African Rift

Journal of Hydrometeorology

Accurate precipitation data are fundamental for understanding and mitigating the disastrous effec... more Accurate precipitation data are fundamental for understanding and mitigating the disastrous effects of many natural hazards in mountainous areas. Floods and landslides, in particular, are potentially deadly events that can be mitigated with advanced warning, but accurate forecasts require timely estimation of precipitation, which is problematic in regions such as tropical Africa with limited gauge measurements. Satellite rainfall estimates (SREs) are of great value in such areas, but rigorous validation is required to identify the uncertainties linked to SREs for hazard applications. This paper presents results of an unprecedented record of gauge data in the western branch of the East African Rift, with temporal resolutions ranging from 30 min to 24 h and records from 1998 to 2018. These data were used to validate the Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis (TMPA) research version and near-real-time products for 3-hourly, daily, and monthly r...

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Research paper thumbnail of Monitoring climate change and anthropogenic pressure at Lake Tanganyika

Journal of Great Lakes Research

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Research paper thumbnail of Climate Change Affects the East African Rift Valley Lakes

ABSTRACT

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Research paper thumbnail of Vertical distribution and light effect on zooplankton density in relationship to fish catch

In this study, I've looked at the zooplankton variability and distribution at night near the ... more In this study, I've looked at the zooplankton variability and distribution at night near the fishing canoes, and tried to correlate these findings to the total fish catch and catch composition. Zooplankton was collected at the surface and from 100 to 0m at two locations: right from the fishermen's boat and about 100m from it. The samples were compared to

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Research paper thumbnail of A preliminary investigation of vertical migration and temporal changes in abundance of pelagic zooplankton during the day and night off Kigoma bay

Lake Tanganyika harbors a simple pelagic zooplankton community in terms of species abundance. The... more Lake Tanganyika harbors a simple pelagic zooplankton community in terms of species abundance. The micro and meso zooplankton communities consist primarily of one calanoid species, three cyclopoid species, while the macrozooplankton community consist of 15 species of shrimp, one species of medusa and two primary species of fish larvae (Coulter, 1991). The zooplankton community is an important indicator of primary

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Research paper thumbnail of Etude de la biologie des espèces de poissons exploités dans le lac Ihema (Bassin de l'Akagera) au Rwanda

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Research paper thumbnail of Pêche et biologie des principales espèces de poissons du lac Ihema (Rwanda)

ABSTRACT

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Research paper thumbnail of Tanganyika Lake: Strong in Hydrodynamics, Diverse in Ecology

Encyclopedia of Earth Sciences Series, 2012

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Research paper thumbnail of Tanganyika Lake, Modeling the Eco-hydrodynamics

Encyclopedia of Earth Sciences Series, 2012

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Research paper thumbnail of Manganese content records seasonal upwelling in Lake Tanganyika mussels

Biogeosciences, 2007

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Research paper thumbnail of Mn seasonal upwellings recorded in Lake Tanganyika mussels

Biogeosciences Discussions, 2006

Biogenic productivity of Lake Tanganyika is highly dependent on seasonal upwellings of anoxic dee... more Biogenic productivity of Lake Tanganyika is highly dependent on seasonal upwellings of anoxic deep waters. We investigated the shell of freshwater bivalve Pleiodon spekii as a geochemical archive of these periodic hydrological changes tuned by the monsoon regime. The results of a 2-years-long geochemical survey of the coastal waters performed on the dissolved and particulate fractions were put in perspective against laser ablation ICP-MS profiles of Mn in five aragonitic shells from the same lake location. Skeletal Mn profiles in 3 shells are very similar and dominated by episodic peaks that matched the Mn increase recorded in surface waters during the 2002 upwelling, while a shell collected during 2003 dry season detect both 2002 and 2003 upwelling events. Larger shells showing an extremely reduced growth display more than 8Mn peaks suggesting at least an 8 years record of seasonal changes in water composition.

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Research paper thumbnail of Silicon Isotopic Fractionation in Lake Tanganyika and Its Main Tributaries

Journal of Great Lakes Research, 2005

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Research paper thumbnail of Drivers of phytoplankton diversity in Lake Tanganyika

Hydrobiologia, 2010

In keeping with the theme of this volume, the present article commemorates the 50 years of Hutchi... more In keeping with the theme of this volume, the present article commemorates the 50 years of Hutchinson’s (Am Nat 93:145–159, 1959) famous publication on the ‘very general question of animal diversity’, which obviously leads to the more important question regarding the driving forces of biodiversity and their limitation in various habitats. The study of phytoplankton in large lakes is a challenging task which requires the use of a wide variety of techniques to capture the range of spatial and temporal variations. The analysis of marker pigments may provide an adequate tool for phytoplankton surveys in large water bodies, thanks to automated analysis for processing numerous individual samples, and by achieving sufficient taxonomic resolution for ecological studies. Chlorophylls and carotenoids were analysed by HPLC in water column samples of Lake Tanganyika from 2002 through 2006, at two study sites, off Kigoma (north basin) and off Mpulungu (south basin). Using the CHEMTAX software for calculating contributions of the main algal groups to chlorophyll a, variations of phytoplankton composition and biomass were determined. We also investigated selected samples according to standard taxonomic techniques for elucidating the dominant species composition. Most of the phytoplankton biomass was located in the 0–40 m layer, with maxima at 0 or 20 m, and more rarely at 40 m. Deep chlorophyll maxima (DCM) and surface ‘blooms’ were occasionally observed. The phytoplankton assemblage was essentially dominated by chlorophytes and cyanobacteria, with diatoms developing mainly in the dry season. The dominant cyanobacteria were very small unicells (mostly Synechococcus), which were much more abundant in the southern basin, whereas green algae dominated on average at the northern site. A canonical correspondence analysis (CCA) including the main limnological variables, dissolved nutrients and zooplankton abundance was run to explore environment–phytoplankton relations. The CCA points to physical factors, site and season as key determinants of the phytoplankton assemblage, but also indicates a significant role, depending on the studied site, of calanoid copepods and of nauplii stages. Our data suggest that the factors allowing coexistence of several phytoplankton taxa in the pelagic zone of Lake Tanganyika are likely differential vertical distribution in the water column, which allows spatial partitioning of light and nutrients, and temporal variability (occurring at time scales preventing long-term dominance by a single taxon), along with effects of predation by grazers.

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Research paper thumbnail of Etude de la biologie des espèces de poissons exploités dans le lac Ihema (Bassin de l'Akagera) au Rwanda

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Global data set of long-term summertime vertical temperature profiles in 153 lakes

Scientific Data

Climate change and other anthropogenic stressors have led to long-term changes in the thermal str... more Climate change and other anthropogenic stressors have led to long-term changes in the thermal structure, including surface temperatures, deepwater temperatures, and vertical thermal gradients, in many lakes around the world. Though many studies highlight warming of surface water temperatures in lakes worldwide, less is known about long-term trends in full vertical thermal structure and deepwater temperatures, which have been changing less consistently in both direction and magnitude. Here, we present a globally-expansive data set of summertime in-situ vertical temperature profiles from 153 lakes, with one time series beginning as early as 1894. We also compiled lake geographic, morphometric, and water quality variables that can influence vertical thermal structure through a variety of potential mechanisms in these lakes. These long-term time series of vertical temperature profiles and corresponding lake characteristics serve as valuable data to help understand changes and drivers of...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Food Web Dynamics in Stable Isotope Ecology

Measurement, Analysis, Simulation, 2003

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Analysis of trophic relationships in two shallow equatorial lakes Lake Naivasha (Kenya) and Lake Ihema (Rwanda) using a multispecifies trophic model

Hydrobiologia, 1996

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Deeper waters are changing less consistently than surface waters in a global analysis of 102 lakes

Scientific Reports

Globally, lake surface water temperatures have warmed rapidly relative to air temperatures, but c... more Globally, lake surface water temperatures have warmed rapidly relative to air temperatures, but changes in deepwater temperatures and vertical thermal structure are still largely unknown. We have compiled the most comprehensive data set to date of long-term (1970–2009) summertime vertical temperature profiles in lakes across the world to examine trends and drivers of whole-lake vertical thermal structure. We found significant increases in surface water temperatures across lakes at an average rate of + 0.37 °C decade−1, comparable to changes reported previously for other lakes, and similarly consistent trends of increasing water column stability (+ 0.08 kg m−3 decade−1). In contrast, however, deepwater temperature trends showed little change on average (+ 0.06 °C decade−1), but had high variability across lakes, with trends in individual lakes ranging from − 0.68 °C decade−1 to + 0.65 °C decade−1. The variability in deepwater temperature trends was not explained by trends in either s...

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Research paper thumbnail of Composition and seasonal variations in abundance of Copepod (Crustacea) populations from the northern part of Lake Tanganyika

Aquatic Ecosystem Health & Management

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Phytoplankton communities in the crater lakes of western Uganda, and their indicator species in relation to lake trophic status

Ecological Indicators

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Evaluating TMPA Rainfall over the Sparsely Gauged East African Rift

Journal of Hydrometeorology

Accurate precipitation data are fundamental for understanding and mitigating the disastrous effec... more Accurate precipitation data are fundamental for understanding and mitigating the disastrous effects of many natural hazards in mountainous areas. Floods and landslides, in particular, are potentially deadly events that can be mitigated with advanced warning, but accurate forecasts require timely estimation of precipitation, which is problematic in regions such as tropical Africa with limited gauge measurements. Satellite rainfall estimates (SREs) are of great value in such areas, but rigorous validation is required to identify the uncertainties linked to SREs for hazard applications. This paper presents results of an unprecedented record of gauge data in the western branch of the East African Rift, with temporal resolutions ranging from 30 min to 24 h and records from 1998 to 2018. These data were used to validate the Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis (TMPA) research version and near-real-time products for 3-hourly, daily, and monthly r...

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Research paper thumbnail of Monitoring climate change and anthropogenic pressure at Lake Tanganyika

Journal of Great Lakes Research

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Research paper thumbnail of Climate Change Affects the East African Rift Valley Lakes

ABSTRACT

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Research paper thumbnail of Vertical distribution and light effect on zooplankton density in relationship to fish catch

In this study, I've looked at the zooplankton variability and distribution at night near the ... more In this study, I've looked at the zooplankton variability and distribution at night near the fishing canoes, and tried to correlate these findings to the total fish catch and catch composition. Zooplankton was collected at the surface and from 100 to 0m at two locations: right from the fishermen's boat and about 100m from it. The samples were compared to

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Research paper thumbnail of A preliminary investigation of vertical migration and temporal changes in abundance of pelagic zooplankton during the day and night off Kigoma bay

Lake Tanganyika harbors a simple pelagic zooplankton community in terms of species abundance. The... more Lake Tanganyika harbors a simple pelagic zooplankton community in terms of species abundance. The micro and meso zooplankton communities consist primarily of one calanoid species, three cyclopoid species, while the macrozooplankton community consist of 15 species of shrimp, one species of medusa and two primary species of fish larvae (Coulter, 1991). The zooplankton community is an important indicator of primary

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Etude de la biologie des espèces de poissons exploités dans le lac Ihema (Bassin de l'Akagera) au Rwanda

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Pêche et biologie des principales espèces de poissons du lac Ihema (Rwanda)

ABSTRACT

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Tanganyika Lake: Strong in Hydrodynamics, Diverse in Ecology

Encyclopedia of Earth Sciences Series, 2012

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Tanganyika Lake, Modeling the Eco-hydrodynamics

Encyclopedia of Earth Sciences Series, 2012

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Manganese content records seasonal upwelling in Lake Tanganyika mussels

Biogeosciences, 2007

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Mn seasonal upwellings recorded in Lake Tanganyika mussels

Biogeosciences Discussions, 2006

Biogenic productivity of Lake Tanganyika is highly dependent on seasonal upwellings of anoxic dee... more Biogenic productivity of Lake Tanganyika is highly dependent on seasonal upwellings of anoxic deep waters. We investigated the shell of freshwater bivalve Pleiodon spekii as a geochemical archive of these periodic hydrological changes tuned by the monsoon regime. The results of a 2-years-long geochemical survey of the coastal waters performed on the dissolved and particulate fractions were put in perspective against laser ablation ICP-MS profiles of Mn in five aragonitic shells from the same lake location. Skeletal Mn profiles in 3 shells are very similar and dominated by episodic peaks that matched the Mn increase recorded in surface waters during the 2002 upwelling, while a shell collected during 2003 dry season detect both 2002 and 2003 upwelling events. Larger shells showing an extremely reduced growth display more than 8Mn peaks suggesting at least an 8 years record of seasonal changes in water composition.

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Research paper thumbnail of Silicon Isotopic Fractionation in Lake Tanganyika and Its Main Tributaries

Journal of Great Lakes Research, 2005

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Research paper thumbnail of Drivers of phytoplankton diversity in Lake Tanganyika

Hydrobiologia, 2010

In keeping with the theme of this volume, the present article commemorates the 50 years of Hutchi... more In keeping with the theme of this volume, the present article commemorates the 50 years of Hutchinson’s (Am Nat 93:145–159, 1959) famous publication on the ‘very general question of animal diversity’, which obviously leads to the more important question regarding the driving forces of biodiversity and their limitation in various habitats. The study of phytoplankton in large lakes is a challenging task which requires the use of a wide variety of techniques to capture the range of spatial and temporal variations. The analysis of marker pigments may provide an adequate tool for phytoplankton surveys in large water bodies, thanks to automated analysis for processing numerous individual samples, and by achieving sufficient taxonomic resolution for ecological studies. Chlorophylls and carotenoids were analysed by HPLC in water column samples of Lake Tanganyika from 2002 through 2006, at two study sites, off Kigoma (north basin) and off Mpulungu (south basin). Using the CHEMTAX software for calculating contributions of the main algal groups to chlorophyll a, variations of phytoplankton composition and biomass were determined. We also investigated selected samples according to standard taxonomic techniques for elucidating the dominant species composition. Most of the phytoplankton biomass was located in the 0–40 m layer, with maxima at 0 or 20 m, and more rarely at 40 m. Deep chlorophyll maxima (DCM) and surface ‘blooms’ were occasionally observed. The phytoplankton assemblage was essentially dominated by chlorophytes and cyanobacteria, with diatoms developing mainly in the dry season. The dominant cyanobacteria were very small unicells (mostly Synechococcus), which were much more abundant in the southern basin, whereas green algae dominated on average at the northern site. A canonical correspondence analysis (CCA) including the main limnological variables, dissolved nutrients and zooplankton abundance was run to explore environment–phytoplankton relations. The CCA points to physical factors, site and season as key determinants of the phytoplankton assemblage, but also indicates a significant role, depending on the studied site, of calanoid copepods and of nauplii stages. Our data suggest that the factors allowing coexistence of several phytoplankton taxa in the pelagic zone of Lake Tanganyika are likely differential vertical distribution in the water column, which allows spatial partitioning of light and nutrients, and temporal variability (occurring at time scales preventing long-term dominance by a single taxon), along with effects of predation by grazers.

Bookmarks Related papers MentionsView impact