Characterisation of Congolese Aquatic Biomass and Their Potential as a Source of Bioenergy

This study assesses the bioenergy potential of two types of aquatic biomass found in the Republic of Congo: the green macroalgae Ulva lactuca (UL) and Ledermanniella schlechteri (LS). Their combustion behaviour was assessed using elemental and biochemical analysis, TGA, bomb calorimetry and metal analysis. Their anaerobic digestion behaviour was determined using biochemical methane potential (BMP) tests. The average HHV for LS is 14.1 MJ kg−1, whereas UL is lower (10.5 MJ kg−1). Both biomasses have high ash contents and would be problematic during thermal conversion due to unfavourable ash behaviour. Biochemical analysis indicated high levels of carbohydrate and protein and low levels of lipids and lignin. Although the lipid profile is desirable for biodiesel production, the levels are too low for feasible extraction. High levels of carbohydrates and protein make both biomasses suitable for anaerobic digestion. BMP tests showed that LS and UL have an average of 262 and 161 mL CH4 gVS−1, respectively. The biodegradability (BI) of LS and UL had an average value of 76.5% and 43.5%, respectively. The analysis indicated that these aquatic biomasses are unsuitable for thermal conversion and lipid extraction; however, conversion through anaerobic digestion is promising.

Geoenvironmental Implications and Biocenosis of Freshwater Lakes in the Arid Zone of East Kazakhstan

Steppe and semi-desert lakes of Central Asia represent unique and still poorly known aquatic ecosystems. The paper provides summaries of multi-proxy environmental and biological investigations of the previously unexplored ground of Sibe lakes in the naturally pristine zone of East Kazakhstan, and of their contributions to people. Data on the taxonomic composition of zooplankton and zoobenthos of these freshwater lacustrine basins are presented in terms of the species’ frequency of occurrence; the abundance of the aquatic biomass and the analyzed water geochemical variables insofar as they are dependent and correlative. The qualitative and quantitative records display variability in the biocenosis diversity due to the lakes’ geochemistry and hydrology differences—some lakes being oligotrophic and others being moderately trophic. In the latter case, the lakes characterized by an increased macrozoobenthos biomass are favourable for local ichthyofauna. Sapro-biological analysis reveals the predominance of β-saprobic species in the zooplankton composition pointing to slight or moderate pollution of surface waters due to natural biotic substances. This observation is in agreement with differences in the water quality of solitary lakes. The uneven distributions of benthic invertebrates (in terms of taxonomy and species populations) in the water bodies suggest specific hydro-ecological conditions that predetermine the structure of the lakes’ biocenosis. The littoral part of the lakes is characterized by the highest abundance of zooplankton and benthic fauna. The Sibe lakes are an example of an autonomous functioning of the lacustrine basins in the upland arid steppe zone, which is characterized by pronounced climate “continentality” and a high level of the sub-aquatic flora and fauna endemism. The present results are relevant to the understanding of the ecosystems’ dynamics and the modern anthropogenic impacts upon the pristine parkland-steppe landscapes of Central Asia, with implications for regional nature protection and sustainable eco-recreation.

The global ocean size-spectrum from bacteria to whales

It has long been hypothesized that aquatic biomass is evenly distributed among logarithmic body mass size-classes. Although this community structure has been observed locally among plankton groups, its generality has never been formally tested across all marine life, nor have its impacts by humans been broadly assessed. Here, we bring together data at the global scale to test the hypothesis from bacteria to whales. We find that biomass within most order of magnitude size-classes is indeed remarkably constant, near 1 Gt wet weight (10^15 grams), but that bacteria and whales are markedly above and below this value, respectively. Furthermore, human impacts have significantly truncated the upper one-third of the spectrum. Size-spectrum theory has yet to provide an explanation for what is possibly life's largest scale regularity.