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49 results for “oligotrophication”
Hubbard Brook Nitrogen Oligotrophication (HBNO): Foliar resorption, leaf mass per area, and leaf chemistry of sugar maple and American beech, 2020-2022
We quantified nitrogen (N) resorption of the two dominant tree species of northern hardwood forests along an elevation gradient using 14 sites at Hubbard Brook Experimental Forest, NH. For these calculations, we also quantified the leaf mass per area for both species, sugar maple and American beech. The original data before averaging for combining with chemistry data is available in an earlier revision of this dataset. Foliar N of sugar maple increased, and N resorption proficiency (NRP) decreased with increasing elevation. In contrast, foliar N and NRP of American beech did not vary significantly with elevation, suggesting that the mechanisms driving patterns of N resorption were distinct between these co-occurring species. While both species exhibited strong correlations between resorption efficiency of C and N, resorption of both elements was much greater for beech than maple. These data were gathered as part of the Hubbard Brook Ecosystem Study (HBES). The HBES is a collaborative effort at the Hubbard Brook Experimental Forest, which is operated and maintained by the USDA Forest Service, Northern Research Station.
Ecosystem metabolism and associated modeling parameters for 6 oligotrophic lakes and ponds in a single watershed
This dataset was collected as part of a watershed-scale study to assess impacts of smoke cover on water temperature and rates of ecosystem metabolism in small lakes and ponds. We measured thermal and metabolic responses to smoke in six waterbodies within a high-elevation watershed (watershed area 1908 ha; elevation range 2800-3229 m.a.s.l) located in Sequoia-Kings Canyon National Park in the Sierra Nevada Mountains of California. All lakes and ponds are oligotrophic, and range in maximum depth from 1.5m to 10m. The dataset includes: time series data of dissolved oxygen, water temperature, and environmental parameters relevant to modeling ecosystem metabolism; estimated rates of ecosystem metabolism using the Kalman filter method; descriptive site information including location, size, and depth.
Chemical characteristics of dissolved organic matter in an oligotrophic subtropical wetland/estuary ecosystem, Everglades National Park (FCE), South Florida from December 2001 to January 2002
The objective of this study was to investigate in detail the molecular characteristics of DOM in a sub-tropical, oligotrophic aquatic environment, namely the Florida coastal Everglades, along a freshwater wetland, mangrove fringe to estuarine transect. For this purpose, surface waters from five sites along Taylor Slough ranging from freshwater marsh to mangrove ecotone environments, as well as three sites within the Florida Bay estuary were collected for analyses. Fluorescence properties of DOM were measured for a quick assessment of DOM quality. Ultrafiltered DOM samples (UDOM; less than 0.7 um, greater than 1000 Da) were concentrated and freeze dried for the determination of bulk C composition, lignin-phenol concentration, and neutral sugar composition. These molecular characteristics were investigated by 13C-NMR spectroscopy, TMAH thermochemolysis, and hydrolysis with trifluoroacetic acid (TFA), respectively. Furthermore, UDOM samples were classified by cluster analysis based on their pyrolysis products obtained via flash pyrolysis-GC/MS.
Physical and microbial processing of dissolved organic nitrogen (DON) (Salinity Experiment) along an oligotrophic marsh/mangrove/estuary ecotone (Taylor Slough and Florida Bay) for August 2003 in Everglades National Park (FCE), South Florida, USA
A better understanding of the biogeochemical cycling of nutrients entering Florida Bay is a key issue regarding the restoration of the Everglades. In addition to precipitation, the other major source of freshwater to Florida Bay is from Taylor Slough and the C-111 Basin in the northeast section of the Bay. While it is known that these areas deliver significant amounts of N to the Bay, a significant portion of this is in the form of dissolved organic N (DON). The sources, environmental fate and bioavailability to microorganisms of this DON are however, not known. Should this DON be readily available, any increased load as a function of restoration changes might have an impact on internal phytoplankton bloom dynamics. No significant flocculation or precipitation of DOM occurred with increase in salinity, meaning that terrestrial DOM does not get trapped in the sediments but stays in the water column where it subjected to photolysis and advective transport. Sunlight has a significant effect on the chemical characteristics of DOM. While the DOC levels did not change significantly during photo-exposure, the optical characteristics of the DOM were modified. The environmental implications of this are conflicting: photo-induced polymerization may stabilize the DOM by reducing its bioavailability while photolysis may make the DOM more labile. Overall, DON bioavailability was relatively low in this region. Even though the amount of DON loaded to the bay may be significant, the fraction of DON available for microbial cycling is much smaller. The amount of N supplied by recycling may be a significant portion of the total DIN pool. All this must be considered in context with the proposed CERP modifications to flows. As of the latest initial Comprehensive Everglades Restoration Project (CERP) update, the flows to Taylor Slough and C-111/Panhandle Basis are not predicted to change very much from base conditions. Therefore we do not expect any great increases in TN loading in this
Physical and microbial processing of dissolved organic nitrogen (DON) (Photodegradation Experiment) along an oligotrophic marsh/mangrove/estuary ecotone (Taylor Slough and Florida Bay) for August 2003 in Everglades National Park (FCE), South Florida, USA
A better understanding of the biogeochemical cycling of nutrients entering Florida Bay is a key issue regarding the restoration of the Everglades. In addition to precipitation, the other major source of freshwater to Florida Bay is from Taylor Slough and the C-111 Basin in the northeast section of the Bay. While it is known that these areas deliver significant amounts of N to the Bay, a significant portion of this is in the form of dissolved organic N (DON). The sources, environmental fate and bioavailability to microorganisms of this DON are however, not known. Should this DON be readily available, any increased load as a function of restoration changes might have an impact on internal phytoplankton bloom dynamics. No significant flocculation or precipitation of DOM occurred with increase in salinity, meaning that terrestrial DOM does not get trapped in the sediments but stays in the water column where it subjected to photolysis and advective transport. Sunlight has a significant effect on the chemical characteristics of DOM. While the DOC levels did not change significantly during photo-exposure, the optical characteristics of the DOM were modified. The environmental implications of this are conflicting: photo-induced polymerization may stabilize the DOM by reducing its bioavailability while photolysis may make the DOM more labile. Overall, DON bioavailability was relatively low in this region. Even though the amount of DON loaded to the bay may be significant, the fraction of DON available for microbial cycling is much smaller. The amount of N supplied by recycling may be a significant portion of the total DIN pool. All this must be considered in context with the proposed CERP modifications to flows. As of the latest initial Comprehensive Everglades Restoration Project (CERP) update, the flows to Taylor Slough and C-111/Panhandle Basis are not predicted to change very much from base conditions. Therefore we do not expect any great increases in TN loading in this
Characterization of dissloved organic nitrogen in an oligotrophic subtropical coastal ecosystem (Taylor Slough and Shark River Slough) for December 2001 in Everglades National Park (FCE), South Florida, USA
A better understanding of the biogeochemical cycling of nutrients entering Florida Bay is a key issue regarding the restoration of the Everglades. In addition to precipitation, the other major source of freshwater to Florida Bay is from Taylor Slough and the C-111 Basin in the northeast section of the Bay. While it is known that these areas deliver significant amounts of N to the Bay, a significant portion of this is in the form of dissolved organic N (DON). The sources, environmental fate and bioavailability to microorganisms of this DON are however, not known. Should this DON be readily available, any increased load as a function of restoration changes might have an impact on internal phytoplankton bloom dynamics. No significant flocculation or precipitation of DOM occurred with increase in salinity, meaning that terrestrial DOM does not get trapped in the sediments but stays in the water column where it subjected to photolysis and advective transport. Sunlight has a significant effect on the chemical characteristics of DOM. While the DOC levels did not change significantly during photo-exposure, the optical characteristics of the DOM were modified. The environmental implications of this are conflicting: photo-induced polymerization may stabilize the DOM by reducing its bioavailability while photolysis may make the DOM more labile. Overall, DON bioavailability was relatively low in this region. Even though the amount of DON loaded to the bay may be significant, the fraction of DON available for microbial cycling is much smaller. The amount of N supplied by recycling may be a significant portion of the total DIN pool. All this must be considered in context with the proposed CERP modifications to flows. As of the latest initial Comprehensive Everglades Restoration Project (CERP) update, the flows to Taylor Slough and C-111/Panhandle Basis are not predicted to change very much from base conditions. Therefore we do not expect any great increases in TN loading in this
Hubbard Brook Nitrogen Oligotrophication (HBNO): Microbial Biomass and Activity, 2021-2023
The goal of this project is to test the overarching hypothesis that positive feedback mechanisms involving changes in seasonal cycles that diminish N availability to plants such that plant N demand is not met by soil N availability in northern forests. Specifically, we hypothesize that increasing N demand by plants (induced by increasing temperatures, longer growing seasons, and other environmental changes) leads to greater N resorption by trees in autumn, increased C:N in litter, and greater net immobilization of N by soil microbes in the following spring. However, the timing of snowmelt and soil freezing in spring may further affect net mineralization and N availability for plants. These hypotheses are being tested with a combination of observational, experimental, and modeling approaches at Hubbard Brook Experimental Forest in New Hampshire: 1) measurements at 14 previously established sites along an elevation/aspect climate gradient; 2) litter and snow manipulation experiments at six sites along the climate gradient to create variation in soil climate conditions and microbial N immobilization during spring. We leveraged 14 sites previously established along an elevation and aspect-driven climate gradient at Hubbard Brook as a “natural climate experiment" to test our hypothesis that a positive feedback between N cycling during fall senescence and spring contributes to declining N availability in northern forests. This elevation gradient encompasses variation in mean annual air temperature of ~2.5 °C that is similar to the change projected to occur with climate change over the next 50–100 years in the northeastern U.S. There is relatively little variation in soils along the gradient. We are utilizing three sites at higher elevation (~550-660 m, north facing) and three sites at lower elevation (~375-500 m, south facing) for the litter and snow manipulation experiments to maximize the differences in temperature among the 14 sites. Litterbox manipulation: The objecti
Hubbard Brook Nitrogen Oligotrophication (HBNO): In-situ Nitrogen Mineralization and Nitrification, 2021-2023
The goal of this project is to test the overarching hypothesis that positive feedback mechanisms involving changes in seasonal cycles that diminish N availability to plants such that plant N demand is not met by soil N availability in northern forests. Specifically, we hypothesize that increasing N demand by plants (induced by increasing temperatures, longer growing seasons, and other environmental changes) leads to greater N resorption by trees in autumn, increased C:N in litter, and greater net immobilization of N by soil microbes in the following spring. However, the timing of snowmelt and soil freezing in spring may further affect net mineralization and N availability for plants. These hypotheses are being tested with a combination of observational, experimental, and modeling approaches at Hubbard Brook Experimental Forest in New Hampshire: 1) measurements at 14 previously established sites along an elevation/aspect climate gradient; 2) litter and snow manipulation experiments at six sites along the climate gradient to create variation in soil climate conditions and microbial N immobilization during spring. We leveraged 14 sites previously established along an elevation and aspect-driven climate gradient at Hubbard Brook as a “natural climate experiment" to test our hypothesis that a positive feedback between N cycling during fall senescence and spring contributes to declining N availability in northern forests. This elevation gradient encompasses variation in mean annual air temperature of ~2.5 °C that is similar to the change projected to occur with climate change over the next 50–100 years in the northeastern U.S. There is relatively little variation in soils along the gradient. We are utilizing three sites at higher elevation (~550-660 m, north facing) and three sites at lower elevation (~375-500 m, south facing) for the litter and snow manipulation experiments to maximize the differences in temperature among the 14 sites. Litterbox manipulation: The objecti
Nutrient Inputs in Mesocosms of an Oligotrophic Lake Fail to Sustain an Algal Bloom, Lake George, NY, 2019
Harmful algal blooms (HABs) pose a significant threat to aquatic ecosystems, and their frequency in oligotrophic lakes—previously thought resistant to such blooms due to their low nutrient levels—has been increasing. This challenges the traditional view that nutrient loading, a major driver of HABs, is less relevant in low-nutrient systems. To investigate whether nutrient enrichment plays a role in HAB development in oligotrophic lakes, we used in-lake mesocosms to assess the effects of varying nitrogen and phosphorus levels on pelagic communities over a 4-week period. The experiment utilized 20 mesocosms (~2,000 L each), with varying phosphorus (P) and nitrogen (N) concentrations, all maintaining a 30:1 N:P ratio, representing ten distinct nutrient levels (235:8 µg/L [control], 600:20 µg/L, 1200:40 µg/L, 1800:60 µg/L, 2400:80 µg/L, 3000:100 µg/L, 3600:120 µg/L, 4200:140 µg/L, 4800:160 µg/L, and 5400:180 µg/L). Nutrients were added twice a week (Tuesdays and Fridays) to sustain the concentrations, with two replicates for each of the ten treatments, totaling 20 experimental units. Water samples were collected to assess water chemistry at two points during the experiment (days 12 and 26). The water chemistry variables measured included total phosphorus (TP), total dissolved phosphorus (TDP), dissolved reactive phosphorus (DRP), total nitrogen (TN), nitrate, nitrite, ammonium, and chlorophyll a. Phytoplankton abundance and abiotic conditions (dissolved oxygen, temperature, pH, and turbidity) were monitored on days 5, 7, 10, 13, 17, 19, 21. Grab samples were also collected on day 12 and 26 to identify phytoplankton species/abundance and zooplankton abundance. In this experiment, nutrient additions enhanced the fluorescence of chlorophyll a (indicative of total phytoplankton) and phycocyanin (a proxy for cyanobacteria), these increases plateaued at low nutrient levels and were transient. Phytoplankton species identification and enumeration revealed no significant changes
Data accompanying the manuscript "Biogeochemical cycling of trace elements and nutrients in ferruginous waters – constraints from a deep oligotrophic ancient lake", published in Limnology and Oceanography (doi: 10.1002/lno.12687)
<p>CTD and geochemical data accompanying the publication: Biogeochemical cycling of trace elements and nutrients in ferruginous waters – constraints from a deep oligotrophic ancient lake in Limnology & Oceanography (doi: 10.1002/lno.12687).</p>
Hubbard Brook Nitrogen Oligotrophication (HBNO): Snowmelt Manipulation study, 2021-2023
In seasonally snow-covered ecosystems such as northern hardwood forests of the northeastern U.S., spring snowmelt is a critical transition period for plant and microbial communities, as well as for the biogeochemical cycling of nitrogen (N). However, it remains unknown how shifting snowmelt dynamics influence soil and plant processing and uptake of N in these forests, which are experiencing reductions in N availability relative to demand, a process known as oligotrophication. We determined the role of changing spring snowmelt timing on root production and N pools and fluxes by manipulating snowmelt timing along a climate elevation gradient at the Hubbard Brook Experimental Forest in New Hampshire. We manually halved or doubled snow water equivalent (SWE) in experimental plots in March of 2022 and 2023 to accelerate or delay by an average of one week, respectively, the onset of spring snowmelt. Earlier snowmelt led to reduced snowpack depth and duration, as well as deeper, more sustained soil frost during the snowmelt period in 2022, but soil freezing did not occur in 2023. Soil nitrate and net nitrification rates were significantly lower with shallower snowpack and earlier snowmelt compared to plots with deeper snow and later snowmelt. Shallower snowpack and early snowmelt were also associated with decreased foliar N concentrations and 15N values, indications that earlier snowmelt contributes to lower N availability relative to plant N uptake and demand. Our study provides evidence that early snowmelt resulting from shallower snowpack contributes to N oligotrophication, primarily through impacts on soil nitrate supply and uptake of N by trees. These data were gathered as part of the Hubbard Brook Ecosystem Study (HBES). The HBES is a collaborative effort at the Hubbard Brook Experimental Forest, which is operated and maintained by the USDA Forest Service, Northern Research Station.
Hubbard Brook Nitrogen Oligotrophication (HBNO): Litter Manipulation study, 2021-2023
Declining nitrogen (N) availability relative to plant demand, known as N oligotrophication, is a widespread phenomenon that has been particularly well documented in northern hardwood forests of the northeast U.S. It is hypothesized that later fall senescence contributes to this trend by increasing tree resorption of N, resulting in higher carbon:nitrogen ratios (C:N) in litterfall and reduced N availability in soil. To examine the effects of litterfall C:N on soil N cycling, we conducted a litter quality manipulation experiment comparing low C:N and high C:N litter with native litter along an elevation and aspect gradient at Hubbard Brook Experimental Forest, NH, USA. We found that potential net ammonification and mineralization rates were positively correlated with litter N and negatively correlated with litter C:N under high C:N litter, but these relationships were not present under native or low C:N litter. Differences in nitrate pools and net mineralization rates between high- and low-quality litter treatments were greater at colder sites where native litterfall tends to have lower C:N than at low elevation sites. Together, these results demonstrate that higher C:N litter and a warming climate likely contribute to N oligotrophication through effects on microbially driven N cycling rates in organic soils. These data were gathered as part of the Hubbard Brook Ecosystem Study (HBES). The HBES is a collaborative effort at the Hubbard Brook Experimental Forest, which is operated and maintained by the USDA Forest Service, Northern Research Station.
Fig. 3 in Water level influences on body condition of Geophagus brasiliensis (Perciformes: Cichlidae) in a Brazilian oligotrophic reservoir
Fig. 3. Means and standard error (vertical lines) for gonadosomatic index (GSI) by sex and size classes for Geophagus brasiliensis in the Lajes Reservoir. Between-sex significant differences: * p <0.05; ** p <0.01.
Fig. 2 in Water level influences on body condition of Geophagus brasiliensis (Perciformes: Cichlidae) in a Brazilian oligotrophic reservoir
Fig. 2. Means and standard errors (vertical lines) for body condition (K) by sex and water level periods for Geophagus brasiliensis in the Lajes Reservoir. Distinct letters (a, b, c) indicate significant differences at 95% level of confidence.
Evolution of the oligotrophic West Pacific Warm Pool during the Pliocene–Pleistocene boundary
<p>We present a new data set from the western Pacific and eastern Indian Ocean exploring the timing of the closing of the Indonesian seaway and its consequent effect on sea surface circulation, productivity and Walker Circulation.</p>
CDOM spectral slope (S275-295) as tracers of water masses, CDOM heterogeneity, and 14C-DOC in an oligotrophic marginal sea
<p>The present study is focused on the CDOM vertical profiles in the northern South China Sea. The results suggest humic-like FDOM is controlling the variation of the spectral slope of CDOM (<em>S</em><sub>275-295</sub>). In addition, our results suggest <em>S</em><sub>275-295</sub> could be used as tracers of water mass, CDOM diversity and radiocarbon age of dissolved organic carbon in oligotrophic ocean.</p>
Stronger thermal response of viral life strategy and lytic activity in a fringing coral reef than in oligotrophic oceans
<p>data_Stronger thermal response of viral life strategy and lytic activity in a fringing coral reef than in oligotrophic oceans</p>
Dataset_urea oxidaiton in the oligotrophic ocean
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Data from: Rediscovery of a presumed extinct species, Salvelinus profundus, after re-oligotrophication
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Data from: Isotopic evidence for oligotrophication of terrestrial ecosystems
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