scholarly journals Diazotrophic Cyanobacteria are Associated With a Low Nitrate Resupply to Surface Waters in Lake Tanganyika

2021 ◽  
Vol 9 ◽  
Author(s):  
Benedikt Ehrenfels ◽  
Maciej Bartosiewicz ◽  
Athanasio Stephano Mbonde ◽  
Kathrin B.L. Baumann ◽  
Christian Dinkel ◽  
...  
Keyword(s):  
Surface Waters ◽  
Phytoplankton Community ◽  
Lake Tanganyika ◽  
Euphotic Zone ◽  
Convective Mixing ◽  
Nitrate Supply ◽  
Upward Transport ◽  
Diazotrophic Cyanobacteria ◽  
Nitrate Depletion ◽  
Productive Surface

In Lake Tanganyika, blooms of nitrogen-fixing (diazotrophic) cyanobacteria emerge, when the upper water column re-stratifies after a period of upwelling and convective mixing. During this seasonal transition, diazotrophic cyanobacteria exploit the abundant phosphate and fix nitrogen after other phytoplankton taxa have consumed the available nitrate. However, it remains less clear, which mechanisms favour diazotrophic cyanobacteria under more heavily stratified conditions with lower levels of excess phosphate and persistent nitrate-depletion. Here, we collected profiles of physicochemical parameters, nutrients and photo-pigments, as well as the medium- to large-sized phytoplankton community during two lake-wide cruises to elucidate to what extent the abundance of diazotrophic cyanobacteria in Lake Tanganyika may be controlled by the nitrate resupply through the thermocline into the euphotic zone. At stations where nitrate was depleted, but phosphate remained available near the surface, high densities of diazotrophic cyanobacteria were associated with a low nitrate supply to surface waters. Our data provide first support for two conceptual scenarios, where the relative position of the thermocline and the euphotic depth may create a functional niche for diazotrophic cyanobacteria: when the upward transport of nitrate into the euphotic zone is reduced by a subjacent thermocline, diazotrophic cyanobacteria, comprising Dolichospermum and Anabaenopsis, are key players in the medium-to large-sized phytoplankton community. By contrast, a thermocline located within the euphotic zone allows for a rapid vertical transport of nitrate for a thriving nitrate-assimilating phytoplankton community that evidently outcompetes diazotrophic cyanobacteria. This study highlights that, under nitrogen-depleted conditions, diazotrophic cyanobacteria can also grow in response to a reduced nutrient resupply to the productive surface waters.

scholarly journals Thermocline depth and euphotic zone thickness regulate the abundance of diazotrophic cyanobacteria in Lake Tanganyika

2020 ◽  
Author(s):  
Benedikt Ehrenfels ◽  
Maciej Bartosiewicz ◽  
Athanasio S. Mbonde ◽  
Kathrin B. L. Baumann ◽  
Christian Dinkel ◽  
...  
Keyword(s):  
Phytoplankton Community ◽  
Lake Tanganyika ◽  
Ecological Factors ◽  
Euphotic Zone ◽  
Cyanobacterial Blooms ◽  
Thermocline Depth ◽  
Nitrogen Fixing ◽  
Multiple Observations ◽  
High Nutrient ◽  
Diazotrophic Cyanobacteria

Abstract. In spite of the fact that cyanobacterial blooms are classically associated with high nutrient loadings, there is also abundant evidence revealing that nitrogen fixing cyanobacteria (diazotrophs) can prevail under oligotrophic conditions. The mechanisms favouring diazotrophs in oligotrophic water bodies remain, however, poorly resolved. Here we analyse biogeochemical and ecological factors regulating the distribution of nitrogen fixing cyanobacteria in the oligotrophic Lake Tanganyika using sensor profiles of hydrodynamic conditions, nutrient and pigment analyses, as well as phytoplankton community assessment. During periods of stable or re-establishing water column stratification, we find evidence that the location of the thermocline and the euphotic depth can create a functional niche for diazotrophic cyanobacteria: Nitrogen limitation provides an ecological advantage for an apparent mutualistic interaction between diazotrophs and diatoms when the upward transport of nitrate into the euphotic zone is reduced by a subjacent thermocline. Diazotrophs, comprising the filamentous genera Dolichospermum and Anabaenopsis, are key players under these conditions (up to 41.7 % of phytoplankton community), while they are rare otherwise. By contrast, a thermocline located within the euphotic zone allows rapid vertical transport of nitrate for a thriving nitrate assimilating phytoplankton community that evidently outcompetes diazotrophs. Finally, multiple observations of relatively high diazotroph densities in the upwelling region in the South of Lake Tanganyika imply that they may additionally thrive under high nutrient conditions, when nitrogen is heavily deficient with respect to phosphorous. This study highlights that, under nitrogen deficient conditions, cyanobacterial blooms may form in response to reduced nutrient fluxes to the productive surface waters.

scholarly journals Supplementary material to "Thermocline depth and euphotic zone thickness regulate the abundance of diazotrophic cyanobacteria in Lake Tanganyika"

2020 ◽  
Author(s):  
Benedikt Ehrenfels ◽  
Maciej Bartosiewicz ◽  
Athanasio S. Mbonde ◽  
Kathrin B. L. Baumann ◽  
Christian Dinkel ◽  
...  
Keyword(s):  
Lake Tanganyika ◽  
Euphotic Zone ◽  
Thermocline Depth ◽  
Diazotrophic Cyanobacteria ◽  
Supplementary Material

scholarly journals Dissolved iron (II) in the Baltic Sea surface water and implications for cyanobacterial bloom development

2009 ◽  
Vol 6 (2) ◽  
pp. 3803-3850 ◽  
Author(s):  
E. Breitbarth ◽  
J. Gelting ◽  
J. Walve ◽  
L. J. Hoffmann ◽  
D. R. Turner ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Surface Waters ◽  
Cyanobacterial Bloom ◽  
Euphotic Zone ◽  
Strong Wind ◽  
Ferrous Ions ◽  
The Baltic Sea ◽  
High Concentrations ◽  
Wind Events ◽  
The Baltic

Abstract. Iron chemistry measurements were conducted during summer 2007 at two distinct locations in the Baltic Sea (Gotland Deep and Landsort Deep) to evaluate the role of iron for cyanobacterial bloom development in these estuarine waters. Depth profiles of Fe(II) were measured by chemiluminescent flow injection analysis (CL-FIA) and reveal several origins of Fe(II) to the water column. Photoreduction of Fe(III)-complexes and deposition by rain are main sources of Fe(II) (up to 0.9 nmol L−1) in light penetrated surface waters. Indication for organic Fe(II) complexation resulting in prolonged residence times in oxygenated water was observed. Surface dwelling heterocystous cyanobacteria where mainly responsible for Fe(II) consumption in comparison to other phytoplankton. The significant Fe(II) concentrations in surface waters apparently play a major role in cyanobacterial bloom development in the Baltic Sea and are a major contributor to the Fe requirements of diazotrophs. Second, Fe(II) concentrations up to 1.44 nmol L−1 were observed at water depths below the euphotic zone, but above the oxic anoxic interface. Finally, all Fe(III) is reduced to Fe(II) in anoxic deep water. However, only a fraction thereof is present as ferrous ions (up to 28 nmol L−1) and was detected by the CL-FIA method applied. Despite their high concentrations, it is unlikely that ferrous ions originating from sub-oxic waters could be a temporary source of bioavailable iron to the euphotic zone since mixed layer depths after strong wind events are not deep enough in summer time.

Iron plays a role in nitrate drawdown by phytoplankton in Lake Erie surface waters as observed in lake-wide assessments

2012 ◽  
Vol 69 (2) ◽  
pp. 369-381 ◽  
Author(s):  
Sonya M. Havens ◽  
Christel S. Hassler ◽  
Rebecca L. North ◽  
Stephanie J. Guildford ◽  
Greg Silsbe ◽  
...  
Keyword(s):  
Surface Waters ◽  
Thermal Stratification ◽  
Lake Erie ◽  
Phytoplankton Community ◽  
Sampling Depth ◽  
Phytoplankton Pigment ◽  
Chl A ◽  
Dissolved Iron ◽  
Continuous Surface

Phytoplankton interactions with iron (Fe) were examined in surface waters of Lake Erie during summer thermal stratification. Lake-wide sampling in June and September 2005 was conducted using a continuous surface water sampler (1 m sampling depth) and in July at 18 hydrographic stations (5 m sampling depth). In situ measurements of photosynthetic efficiency (maximum quantum yield of photosystem II) and phytoplankton community composition were measured using fast repetition rate fluorometry and a phytoplankton pigment-specific fluorometer, respectively, during June and September. High ratios (73%–85%) of intracellular Fe to particulate Fe coincident with increases in chlorophyll a (Chl a) concentrations in the western and central basins in June and July imply that the majority of Fe in these regions was associated with intracellular pools. Correlations between intracellular Fe and Chl a were frequently observed when Heterokontophyta and Pyrrophyta dominated the phytoplankton community. Assimilation of Fe by the phytoplankton strongly influenced its partitioning between the dissolved and particulate phase. Dissolved iron (<0.45 µm) concentrations were proportional to Chl a concentrations and both dissolved iron and Chl a were inversely proportional to nitrate concentrations in July and September, suggesting that dissolved iron influenced both nitrate drawdown and Chl a concentrations in Lake Erie surface waters in summer.

scholarly journals Structure of the phytoplankton community in the Cachoeira Dourada reservoir (GO/MG), Brazil

2011 ◽  
Vol 71 (3) ◽  
pp. 587-600 ◽  
Author(s):  
M. Teixeira de Oliveira ◽  
O. Rocha ◽  
AC. Peret
Keyword(s):  
Phytoplankton Community ◽  
Driving Forces ◽  
Climatic Factors ◽  
Euphotic Zone ◽  
Taxonomic Composition ◽  
Nitrogen And Phosphorus ◽  
Physical And Chemical Variables ◽  
Algal Assemblages ◽  
Physical And Chemical

The limnological features and the phytoplankton community of the Cachoeira Dourada reservoir were analyzed in December 2006, May 2007 and November 2007. Temporal changes in the taxonomic composition, density, diversity and dominance of species were analyzed in relation to climatic factors and the physical and chemical characteristics of the water. A positive correlation was found between some of the physical and chemical variables and the phytoplankton community. According to the CCA, variables such as the extent of the euphotic zone, temperature, pH, nitrogen and phosphorus concentrations directly affected the phytoplankton dynamics. Organisms belonging to the class Cyanophyceae were the most representative in all the sampling periods, comprising the functional groups K, S1, M and H. Hydrodynamics and seasonal fluctuations of environmental factors were the driving forces determining the composition and abundance of the algal assemblages. Despite the prevalence of Cyanobacteria, the reservoir is still oligotrophic. The absence of blooms and the relatively low population abundances indicated that the quality of the reservoir's water still lies within the limits required for its multiples uses.

scholarly journals What limits photosynthetic energy conversion efficiency in nature? Lessons from the oceans

2017 ◽  
Vol 372 (1730) ◽  
pp. 20160376 ◽  
Author(s):  
Paul G. Falkowski ◽  
Hanzhi Lin ◽  
Maxim Y. Gorbunov
Keyword(s):  
Quantum Yield ◽  
Energy Conversion ◽  
Conversion Efficiency ◽  
Surface Waters ◽  
Phytoplankton Community ◽  
Inorganic Nitrogen ◽  
Photosynthetic Apparatus ◽  
Energy Conversion Efficiency ◽  
Thermal Dissipation ◽  
Essential Components

Constraining photosynthetic energy conversion efficiency in nature is challenging. In principle, two yield measurements must be made simultaneously: photochemistry, fluorescence and/or thermal dissipation. We constructed two different, extremely sensitive and precise active fluorometers: one measures the quantum yield of photochemistry from changes in variable fluorescence, the other measures fluorescence lifetimes in the picosecond time domain. By deploying the pair of instruments on eight transoceanic cruises over six years, we obtained over 200 000 measurements of fluorescence yields and lifetimes from surface waters in five ocean basins. Our results revealed that the average quantum yield of photochemistry was approximately 0.35 while the average quantum yield of fluorescence was approximately 0.07. Thus, closure on the energy budget suggests that, on average, approximately 58% of the photons absorbed by phytoplankton in the world oceans are dissipated as heat. This extraordinary inefficiency is associated with the paucity of nutrients in the upper ocean, especially dissolved inorganic nitrogen and iron. Our results strongly suggest that, in nature, most of the time, most of the phytoplankton community operates at approximately half of its maximal photosynthetic energy conversion efficiency because nutrients limit the synthesis or function of essential components in the photosynthetic apparatus. This article is part of the themed issue ‘Enhancing photosynthesis in crop plants: targets for improvement’.

Some Aspects of the Ecology of Lake Macquarie, N.S.W., with Regard to an Alleged Depletion of Fish. V. Chlorophyll Distribution

1959 ◽  
Vol 10 (3) ◽  
pp. 316
Author(s):  
PS Davis
Keyword(s):  
Surface Waters ◽  
Vertical Profile ◽  
Chlorophyll Concentration ◽  
Euphotic Zone ◽  
Early Summer ◽  
Late Winter ◽  
Light Penetration ◽  
Chlorophyll Distribution ◽  
The Mean ◽  
Made In

The chlorophyll a in samples from five stations in Lake Macquarie was determined over the period July 1955 to November 1956. The mean surface value for the four stations within the lake proper was 1.26 mg/m³. The vertical profile at one station was studied and the mean of these profile values was 1.23 mg/m³. Throughout the period of the survey chlorophyll concentrations in the lake varied from 0.1 to 4.0 mg/m³. The lowest values were found in the late winter and early summer (November) and the peaks during spring and autumn. The chlorophyll concentration in the surface waters of Lake Macquarie was shown to be significantly higher than that of the marine water entering the lake, but lower than that of a comparison station in the Hawkesbury River. One series of light penetration measurements made in December 1956 showed that all the water in the lake, and all but one section of Dora Creek, lay within the euphotic zone.

scholarly journals Manganese content records seasonal upwelling in Lake Tanganyika mussels

2007 ◽  
Vol 4 (2) ◽  
pp. 195-203 ◽  
Author(s):  
D. Langlet ◽  
L. Y. Alleman ◽  
P.-D. Plisnier ◽  
H. Hughes ◽  
L. André
Keyword(s):  
Surface Waters ◽  
Coastal Waters ◽  
Lake Tanganyika ◽  
Manganese Content ◽  
Monsoon Climate ◽  
Freshwater Bivalve ◽  
Water Composition ◽  
Deep Waters ◽  
Crater Size ◽  
Icp Ms

Abstract. Biogenic productivity of Lake Tanganyika is highly dependent on seasonal upwellings of cold, oxygen-depleted, nutrient-rich 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 three-year-long limnological and geochemical survey of the coastal waters performed on the dissolved and particulate fractions were compared to LA-ICP-MS profiles of Mn in five aragonitic shells from the same lake location. Three shells present very similar Mn/Ca profiles dominated by a peak that matched the concomitant increase of Mn and chlorophyll a 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 8 Mn/Ca peaks suggesting at least an 8-year-record of seasonal changes in water composition. We postulate that Mn/Ca in shells record the conjunction of an increase of biological activity with supplied of dissolved Mn and nutriments in coastal waters, resulting in an enhanced assimilation of biogenic Mn-rich particles. By combining the most recent generation of laser ablation system and the powerful High Resolution ICP-MS, the spatial resolution could be improved down to 5 to 10 µm crater size and end up in a better constrain of the relative variations of the annual Mn peaks. Such an approach on P. spekii from Lake Tanganyika has definitively a great potential to provide recent and past records on primary productivity associated with the monsoon climate system.

Stimulation of Nitrate Uptake and Photosynthesis by Molybdenum in Castle Lake, California

1980 ◽  
Vol 37 (4) ◽  
pp. 707-712 ◽  
Author(s):  
R. P. Axler ◽  
R. M. Gersberg ◽  
C. R. Goldman
Keyword(s):  
Nitrate Uptake ◽  
Phytoplankton Community ◽  
Euphotic Zone ◽  
Growing Season ◽  
Uptake Rates ◽  
Early Portion ◽  
Rate Of Photosynthesis ◽  
Castle Lake ◽  
Stimulation Of

The uptake rates of 15NO3 and 14CO2 by the natural phytoplankton community at Castle Lake, California, were measured in situ as responses to 5 μg∙L−1 additions of molybdenum. Stimulation of both nitrate uptake and photosynthesis occurred in water samples containing only relatively high amounts of nitrate. This response to added molybdenum disappeared as the growing season progressed and nitrate was depleted in the euphotic zone. Although molybdenum stimulated nitrate uptake by 55% in water collected from the lower euphotic zone, it did not increase the rate of CO2 uptake because at that depth the rate of photosynthesis was most limited by light intensity and not by nitrogen. An analysis of molybdenum bioassays from 1959 to 1963 is integrated with these findings and points to the importance of molybdenum for phytoplankton growth during the early portion of the growing season when nitrate concentrations in the euphotic zone are maximal.Key words: molybdenum, nitrate, nitrate uptake, micronutrient bioassays

Influence of extended water column mixing during the first 2 years of hypolimnetic oxygenation on the phytoplankton community of Amisk Lake, Alberta

1997 ◽  
Vol 54 (9) ◽  
pp. 2133-2145 ◽  
Author(s):  
D J Webb ◽  
R D Robarts ◽  
E E Prepas
Keyword(s):  
Water Column ◽  
Trophic Status ◽  
Phytoplankton Community ◽  
Euphotic Zone ◽  
Open Water ◽  
Eutrophic Lake ◽  
Cyanobacterial Blooms ◽  
Chl A ◽  
Hypolimnetic Oxygenation ◽  
Physical Variables

The phytoplankton community, physical variables, and nutrient and chlorophyll a (Chl a) concentrations were monitored during the first two of six open-water seasons of hypolimnetic oxygenation in double-basined Amisk Lake, Alberta. Deep mixing of the water column in the treated basin (Zmax = 34 m) in spring was enhanced by hypolimnetic oxygenation. Oxygenation began in June 1988, when stratification was likely already established, but subsequent year-round treatment favoured an extended spring diatom bloom (Asterionella formosa and Cyclotella spp.), followed by a delay in the development of, and reduction in the severity of, cyanobacterial blooms (Aphanizomenon flos-aquae and Anabaena flos-aquae) in 1989. Historically, mean summer Chl a and total phosphorus (TP) concentrations in the euphotic zone (0-6 m) of the treated basin were 15.9 ± 1.6 and 33.5 ± 1.5 µg ·L-1, respectively, indicating a eutrophic lake. In 1988 and 1989, mean summer Chl a (10.0 ± 0.6 and 8.1 ± 0.7 µg ·L-1, respectively) and TP concentrations (29.0 ± 0.5 and 22.5 ± 0.9 µg ·L-1, respectively) in this stratum were lower than historic values (P < 0.05), indicating that the trophic status of Amisk Lake had shifted towards mesotrophy.

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