Role of eddies and N2 fixation in shaping C:N:P proportions in the Bay of Bengal during spring

<p>Bioavailable nitrogen (N) and phosphorus (P) determine the strength of the ocean’s carbon (C) uptake and variation in their ratio (N:P) is key to phytoplankton growth. A similarity between C:N:P ratio (106:16:1) in plankton and deep-water inorganic nutrients was observed by Alfred C. Redfield, who suggested that biological processes in the surface ocean controlled deep ocean chemistry. Recent studies suggest that the ratio varies geographically. The veracity in C:N:P ratio could be attributed to the characteristic physical and biogeochemical processes, which play an important role in regulating the elemental dynamics in ocean. Basins like the northern Indian Ocean due to its geographic setting and monsoonal wind forcing provide a natural laboratory to explore the role of environmental factors, physical and biogeochemical processes on C:N:P stoichiometry.</p><p>We sampled the Bay of Bengal for its C, N, and P contents in the organic and inorganic pool from surface to 2000 m at 8 stations (5 coastal, 3 open ocean) during spring 2019. Mesoscale anticyclonic eddies were identified in our sampling area, which were associated with low nutrient concentrations in the photic depth. Mean (NO<sub>3</sub><sup>- </sup>+ NO<sub>2</sub><sup>-</sup>):PO<sub>4</sub><sup>3-</sup> ratio was 0.6 at eddy and 4.7 at non eddy stations. On the other hand, C:N:P in the organic matter was same at eddy and non-eddy locations. Mean C:N:P ratio in particulate organic matter was 254:39:1 and 244:37:1 in the photic depth of the coastal and open ocean stations, respectively. Biological N<sub>2</sub> fixation contributed ~0.1-0.4% to the N:P ratio of export flux, which ultimately contributes to the (NO<sub>3</sub><sup>- </sup>+ NO<sub>2</sub><sup>-</sup>):PO<sub>4</sub><sup>3-</sup> ratio in subsurface waters. Our results highlight the importance of physical and biological processes in changing elemental stoichiometry.</p>

Non-Redfieldian C:N:P ratio in the inorganic and organic pools of the Bay of Bengal during the summer monsoon

Nitrogen (N) and phosphorus (P) determine the strength of the ocean’s biological carbon (C) pump, and variation in the N:P ratio is key to phytoplankton growth. A fixed C:N:P ratio (106:16:1) in organic matter and deep-water nutrients was observed by Alfred C. Redfield. However, recent studies have challenged the concept of the Redfield Ratio, and its veracity remains to be examined in oceanic basins like the Bay of Bengal. For this purpose, we sampled the water in the Bay of Bengal for C, N, and P content in the organic and inorganic pools from the surface to 2000 m. Overall, the C:N:P ratio deviated greatly from the Redfield Ratio. The C:N:P ratio in particulate organic matter varied from 232:25:1 in the top layer (surface to the depth of the chlorophyll maximum) to 966:72:1 in the deep water (300-2000 m). In dissolved organic matter, the ratio varied from 357:30:1 in the top layer to 245:66:1 in the deep water. The N:P ratio in nutrients varied from 3 in the top layer to 12 in the deep water. The nutrient-depleted top layer (average NO3- + NO2- ~ 0.7 µmol l-1) with a low N:P ratio coupled with reported low primary production rates in the Bay suggested that the production was N limited. Concurrent N2 fixation rates were not sufficient to alter the observed C:N:P ratio. Eddies showed a mixed effect on the C:N:P ratio. Our C:N:P ratios in particulate organic matter are comparable to other tropical basins and supports the nutrient supply hypothesis for low latitude ecosystems.

Characteristics and Environmental Factors of Stoichiometric Homeostasis of Soil Microbial Biomass Carbon, Nitrogen and Phosphorus in China

Marine studies have shown that the carbon:nitrogen:phosphorus (C:N:P) atomic ratio in planktonic organisms is generally 106:16:1, which is known as the “Redfield ratio”. This raises the question of whether there are similar patterns in terrestrial organisms, particularly in soil. In this study, we extracted 404 datasets from the literature to analyze the ecological stoichiometry of C, N and P, both in the soil and in the soil microbial biomass in China; additionally, we assessed their relationships with environmental factors, and calculated the homeostasis coefficient (H) of soil microbial biomass. First, although the concentrations of C, N and P in soil and soil microbial biomass showed high spatial heterogeneity, the atomic C:N:P ratios in the soil and soil microbial biomass were relatively consistent at the national scale. Second, the influences of temperature and precipitation on stoichiometric relationships among C, N and P in the soil and soil microbial biomass were limited in China; however, they decreased with the increase in soil pH. Third, the degree of stoichiometric homeostasis for soil microbes spanned a wide range, from non-homeostasis to strict homeostasis. For single elements, most of the soil microbes’ H ranged from 1.01 to 5.00; for elemental ratios, most of the soil microbes’ H displayed strict homeostasis. This study indicates that the “Redfield-like” ratio exists in the soil microbial biomass in the 0–20 cm soil layer in China, with an atomic C:N:P ratio of 66:8:1 and it is close to the atomic C:N:P ratio in the soil (66:5:1) of terrestrial ecosystems. In addition to the N:P ratio in plants, the soil microbial biomass N:P ratio may also be used to judge the nutrient limitations because of its high stability.

Partially aerated submerged fixed-film bioreactor for simultaneous removal of carbon and nutrients from high-strength nitrogen wastewaters: effect of aeration rate and C:N:P ratio

Influence of aeration rate and COD:N:P (C:N:P) ratio on the performance of an upflow partially aerated submerged fixed film (UP/ASFF) bioreactor for simultaneous carbon and nutrient removal from high-strength nitrogen wastewater was investigated during 6 months. Airflow rates at three levels of 1.5, 3, and 4.5 L/min and C:N:P ratios at four levels of 450:300:10, 450:150:10, 450:100:10, and 450:75:10 were selected as the two main input factors. All experiments were performed at constant chemical oxygen demand (COD), phosphorus (P) and hydraulic residence time of 450 mg COD/L, 10 mg PO43− -P/L and 7.3 h, respectively. The results showed when the airflow rate increased from 1.5 to 4.5 L/min, complete COD removal was achieved. At an airflow rate of 4.5 L/min, total nitrogen removal reached a maximum value of 75% for the C:N:P ratio of 450:75:10. A maximum value of 54% for total phosphorus removal, however, was obtained at an airflow rate of 3 L/min for the C:N:P ratio of 450:75:10. Analysis of variance for the obtained data revealed that aeration rate and nitrogen concentration had more impact on phosphorus removal than COD and nitrogen removal. The study demonstrated that the UP/ASFF system has considerable potential for use in simultaneous removal of carbon and nutrients for high-strength nitrogen wastewater.

KULTIVASI SPIRULINA PLATENSIS PADA MEDIA BERNUTRISI LIMBAH CAIR TAHU DAN SINTETIK

This research was conducted to study the effect of various additions of synthetic nutrient into Spirulina platensis growth medium containing tofu wastewater 8%v/v. Synthetic nutrient was varied at 50, 75, 100%. Based on abservation, the OD680 (Optical Density at 680 nm) increased until in the end of cultivation time with final OD680 of 0.381, 0.392, 0.189 for variable of 50, 75, 100% respectively. Meanwhile, the growth rate value was 0.0743, 0.0759, 0.0354/day. The best protein content was obtained at nutrient synthetic of 75%, which was 91,27%. The good growth and protein content of S. platensis obtained at nutrient synthetic of 75%, which had C:N:P ratio of 128:12:1.