Assessment of the quality and quantity of organic matter in the Rufiji mangrove surface sediments using biochemical composition

This study was carried out to investigate spatial changes in the quality and quantity of sedimentary organic matter in the Rufiji mangrove system, Tanzania. Sediment samples were collected from three sampling sites. Total organic matter in mangrove sediments ranged from 7.28 ± 2.02% to 10.58 ± 1.34%. Protein concentrations varied from 1,145.33 ± 20.33 μg/g to 2,747.50 ± 25.14 μg/g in the mangrove sediments. Total carbohydrates, lipids and biopolymeric carbon in mangrove sediments ranged between 1,110.50 ± 16.31 μg/g and 1,914.17 ± 27.79 μg/g, 1,436.50 ± 24.13 μg/g and 6,373.50 ± 25.79 μg/g, and 4,496 μg C/g and 10,231.50 μg C/g, respectively. Tannins and lignins in mangrove sediments varied from 817.67 ± 12.97 μg/g to 1786.50 ± 30.74 μg/g, while stable carbon isotope (δ13C) in Rufiji mangrove sediments ranged between –26.64 ± 0.10 ‰ and –25.48 ± 0.13 ‰. Higher protein:carbohydrate (PRT:CHO) at station 3 indicated the presence of freshly deposited organic matter. The high lipid:carbohydrate (LPD:CHO) ratios observed in the Rufiji mangrove systems pointed towards the high quality of labile organic matter which supports benthic fauna. PCA revealed the association of variables and their distribution on trends across sites of the Rufiji mangrove system. Keywords: Organic matter, biochemical composition, Rufiji, mangroves, sediments

Biochemical and microbiological tools for the evaluation of environmental quality of a coastal lagoon system in Southern Brazil

This study aimed to evaluate the environmental quality of surface water of the Maricá Lagoon System through physicochemical, biochemical and microbiological parameters, in order to assess its environmental quality. Marine influence over the system was evidenced by the salinity and temperature gradients, where the most distant point, in Maricá Lagoon, presented the largest protein, lipid and biopolymeric carbon concentrations. Biopolymers, with predominance of lipids, presented a pattern that differs from the literature for coastal sediments. The concentration of thermotolerant coliforms characterised Maricá Lagoon and Boqueirão Channel as unfit for bathing (60.0 and 66.3 cells.mL-1, respectively). The bacterioplankton in the system proved to be predominantly heterotrophic, a consumer of organic matter, with fermentative, denitrifying and sulfate-reducing metabolism. No esterase enzyme activity was detected, despite the presence of active metabolism, measured by the electron transport system (average of 0.025 µgO2.h-1.mL-1). The bacterial biomass (autotrophic, heterotrophic and coliforms), bacterial respiratory activity and biopolymer parameters evinced a spatial degradation pattern in the Maricá Lagoon System, where the points with less water renewal are the most impacted.

Biodisponibilidade da Matéria Orgânica dos Sedimentos Superficiais da Baía de Guanabara, Rio de Janeiro, Brasil

Thirty superficial sediment samples were collected in Guanabara Bay in order to identify new trophic state and environmental quality descriptors for coastal systems. A biochemical approach was used for analyzing the quality and quantity of sedimentary organic matter and metabolic bacterial activity. The samples were analyzed for particle size; organic matter, protein, carbohydrate, lipid, biopolymeric carbon, and bioavailable carbon levels; and bacterial metabolic activity. The results show a homogeneous spatial distribution for the anaerobic bacteria web and for biopolymers (carbohydrates>;lipids>;protein). The NE area of the bay displayed sediment lipid levels above 1 mg/g, indicative of organic sewage input. Spatial distribution of the superficial sediments in relation to other variables was not significant (p>;0.05). Biopolymers and labile organic matter showed a significant correlation with the average particle size of 80% of the fine particles. Despite the availability of labile organic matter, under the form of biopolymeric carbon, only 50% of the carbon was available to the trophic web. The bacterial consortia formed by sulfate reducing and denitrifying bacteria sustain the benthic trophic food web in Guanabara Bay.

Sediment biochemical and microbial variables for the evaluation of trophic status along the Italian and Albanian continental shelves

Phytopigment concentrations (chlorophyll-a and phaeopigments), labile organic matter (proteins, carbohydrates and lipids), bacterial density and frequency of dividing cells were analysed in the sediments of a large coastal area covering the southern Adriatic continental shelf between Italy and Albania in order to describe the trophic status of coastal marine sediments. On average, sediments of the Italian coast displayed the highest phytopigment and biopolymeric carbon concentrations compared to sediments of the Albanian coast and indicated an increased nutritional status of this coastal ecosystem. Different trophic conditions were evidenced in terms of biopolymeric composition of sedimentary organic matter as an increase in protein and a decrease in the carbohydrate contributions to total biopolymeric carbon was observed moving from the Albanian to the Italian coast. Using a benthic approach for the evaluation of trophic status shallow Italian sediments (0–50 m) were mainly classified as eutrophic and were subjected to stronger anthropogenic disturbance. This was particularly evident in areas in front of city harbours (Brindisi and Barletta) that were classified as hypertrophic and displayed the highest biopolymeric carbon (BPC) concentrations and protein to carbohydrate ratio (PRT:CHO on average >1). In contrast Albanian sediments as well as deeper Italian stations (>50 m), resulted mainly in meso-oligotrophic and displayed lower BPC and PRT:CHO ratio (on average <1). The study of bacterial variables provided an improved approach for the conceptual definition of trophic state using benthic biochemical measures. An inverse relationship occurred between the nutritional contents and the bacterial density within meso-oligotrophic sediments. This may reflect an increase in ecosystem organization and complexity (i.e. increased abundance of the higher trophic levels) which may determine a reduction of the bacterial density at increasing trophic conditions. In contrast a positive correlation was found within eutrophic and hypertrophic sediments suggesting that at high organic matter concentrations the ecosystem is no longer capable of further organization.

Viral Density and Virus-to-Bacterium Ratio in Deep-Sea Sediments of the Eastern Mediterranean

ABSTRACT Viruses are now recognized as a key component in pelagic systems, but their role in marine sediment has yet to be assessed. In this study bacterial and viral densities were determined at nine deep-sea stations selected from three main sites (i.e., the Sporades Basin, the Cretan Sea, and the Ierapetra Trench at depths of 1,232, 1,840, and 4,235 m, respectively) of the Eastern Mediterranean. The three areas were characterized by different phytopigment and biopolymeric carbon concentrations and by changes in the protein and carbohydrate pools. A gradient of increasing trophic conditions was observed from the Sporades Basin (North Aegean) to the Ierapetra Trench (South Aegean). Viral densities (ranging from 1 × 109 to 2 × 109 viruses ml of sediment−1) were significantly correlated to bacterial densities (n = 9, r 2 = 0.647) and reached values up to 3 orders of magnitude higher than those generally reported for the water column. However, the virus-to-bacterium density ratio in deep-sea sediments was about 1 order of magnitude lower (range of 2 to 5, with a modal value of 2.6) than in pelagic environments. Virus density decreased vertically with depth in sediment cores at all stations and was below detection limits at the 10-cm depth of the abyssal sediments of the Ierapetra Trench. Virus density in the sediment apparently reflected a gradient of particle fluxes and trophic conditions, displaying the highest values in the Sporades Basin. The low virus-to-bacterium ratios and their inverse relationship with station depth suggest that the role played by viruses in controlling deep-sea benthic bacterial assemblages and biogeochemical cycles is less relevant than in pelagic systems.