Assessing the Composition of Particulate Organic Matter and Zooplankton Food Sources in Lake Superior and Across a Size-Gradient of Aquatic Systems | Chapter 1 | Contemporary Research and Perspectives in Biological Science Vol. 5

Food webs in aquatic systems can be supported both by carbon from recent local primary productivity and by carbon subsidies, such as material from terrestrial ecosystems or past in situ primary productivity. The importance of these subsidies to respiration and biomass production remains a topic of debate.  While some studies have reported that terrigenous organic carbon supports disproportionately high zooplankton production, others have suggested that phytoplankton preferentially supports zooplankton production in aquatic ecosystems. Quantification of zooplankton food sources using ambient stable carbon isotopic signatures is difficult because of the inherent difficulty in directly measuring the δ¹³C of phytoplankton, and the narrow and overlapping range of phytoplankton and terrigenous organic matter δ¹³C signatures, especially in freshwater systems. The objectives of this study were (1) to use isotopic composition to assess the food sources of mesozooplankton in Lake Superior, and (2) to investigate food sources of zooplankton in a suite of other aquatic systems.  Natural abundance radiocarbon (∆¹⁴C) and stable isotope (δ¹³C, δ¹⁵N) analyses were applied to show that zooplankton in Lake Superior selectively incorporate recently-fixed, locally-produced (autochthonous) organic carbon even though other carbon sources are readily available.  Estimates from Bayesian isotopic modeling based on ∆¹⁴C and δ¹³C values show that the average lakewide median contributions of recent in-lake primary production and terrestrial, sedimentary, and bacterial organic carbon to the bulk POM in Lake Superior were 58%, 5%, 33%, and 3%, respectively. However, isotopic modeling estimates also show that recent in situ production contributed a disproportionately large amount (median, 91%) of the carbon in mesozooplankton biomass in Lake Superior. Although terrigenous organic carbon and old organic carbon from resuspended sediments were significant portions (median, 38%) of the available basal food resources, these contributed only a small amount to mesozooplankton biomass (median, 3% from sedimentary organic carbon and 3% from terrigenous organic carbon). The isotopic investigation shows that intermediate trophic-level mesozooplankton in Lake Superior prefer to incorporate fresh autochthonous food, despite the availability of other organic carbon sources, and that upper trophic levels are likely not supported by terrestrial and/or resuspended-sediment OC subsidies to the carbon cycle.    Comparison of zooplankton food sources based on their radiocarbon composition showed that terrigenous organic carbon was relatively more important in rivers and small lakes, and the proportion of terrestrially-derived material used by zooplankton correlated with the hydrologic residence time and the ratio of basin area to water surface area.  Further research should focus on the catabolic metabolism of mesozooplankton and both anabolic and catabolic metabolism in the microbial loop to further our understanding of such subsidies in the carbon cycle and energy transfer.

 

Author (s) Details

Prosper K. Zigah
Large Lakes Observatory and Water Resources Science Program, University of Minnesota, Minnesota, USA and Department of Surface Waters, Swiss Federal Institute of Aquatic Science and Technology (Eawag), Kastanienbaum, Switzerland and Department of Chemistry, Biochemistry and Physics, Georgia Southern University, Statesboro, Georgia, USA.

 

Elizabeth C. Minor
Large Lakes Observatory and Department of Chemistry and Biochemistry, University of Minnesota-Duluth, Minnesota, USA.

 

Josef P. WerneA
Department of Geology and Environmental Sciences, University of Pittsburgh, Pennsylvania, USA.

 

S. Leigh McCallister
Department of Biology, Virginia Commonwealth University, Richmond, Virginia, USA.

 

Please see the book here:- https://doi.org/10.9734/bpi/crpbs/v5/2314

Studies on Global Redox Carbon Cycle and Periodicity of Some Phenomena in Biosphere (6381)| Chapter 4 | Challenging Issues on Environment and Earth Science Vol. 6

 A global redox carbon cycle model is used to investigate the irregular periodicity of some biosphere events such as climatic cycles, mass extinctions, sudden changes in biodiversity rate, and others over geological time. It is demonstrated that the periodicity of these various natural events is caused by a single cause. Moving lithospheric plates have a periodic impact on photosynthesis via CO2 injections, which is the cause. The oxidation of sedimentary organic matter via thermochemical sulphate reduction from the subduction zone, where plates clash, is the source of CO2. Orogenic cycles are generated by the periodicity and irregularity of lithospheric plate movement, which occur against a backdrop of orogenic cycles. Identify the geological events that occurred in the past. Orogenic cycles occurred until the carbon cycle reached the ecological compensation point, which occurs when the amount of photosynthetically produced carbon equals the amount of reduced carbon oxidised in the Earth's crust's various oxidation processes. Long-term orogenic cycles were replaced by short-term climatic oscillations after this time. The orogenic cycles and climatic oscillations share the same set of characteristics, indicating that they are of the same nature. The only things that have changed are the length of the event and the magnitude of its impact.

Author(s) Details

Dr. Alexander A. Ivlev
Russian State Agrarian University - Moscow Agricultural Academy of Timiryazev, Timiryazevskaya str. 49 Moscow 127550, Russia.

View Book :- https://stm.bookpi.org/CIEES-V6/article/view/2830

1 Carbon Isotopic Data Validate the New Model of Carbon Turnover | Chapter 7 | Challenging Issues on Environment and Earth Science Vol. 2

 It is proposed that a new global redox carbon cycle model be created. It claims that the movement of the lithosphere plates has an effect on photosynthesis growth. Periodic injections of CO2 from plate collision zones are used to create the effect. In subduction zones, carbon dioxide is produced by the oxidation of sedimentary organic carbon during thermochemical sulphate reduction. Carbon turnover is characterised as the transformation of an element from its oxidised state (CO2 + HCO3- + CO32-) to its reduced state (CO2 + HCO3- + CO32-) as a result of photosynthesis and subsequent transformations. The isotopic data back up the model's validity. They clarify why the carbon isotope composition of sedimentary organic matter corresponds with geologic age. The discrepancy between the carbon isotope composition of organic matter and that of coeval carbonates was discovered to be an analogue of the carbon 13C isotope discrimination used by modern plants in photosynthesis. Isotopic periodicity coincides with the periodicity of climatic shifts, mass extinctions, the irregularity of stratigraphic distribution of organic-rich rocks, and other periodic occurrences in the biosphere. The model describes how the evolution of photosynthesis contributed to the accumulation of oxygen in the atmosphere and sedimentary organic matter in the Earth's crust, and how these developments gradually led to an ecological compensation point in the global carbon cycle system. At this point, all of the system's parameters stabilised and started to oscillate around a fixed point.

Author (s) Details

A. A. Ivlev
Russian State Agrarian University of K. A. Timiryazev, Moscow.

View Book :- https://stm.bookpi.org/CIEES-V2/issue/view/60