PON Ratio Research Articles

Molar ratios of C, N, P of particulate matter and their vertical fluxes in the Yellow Sea

The vertical fluxes and molar ratios of carbon, nitrogen and phosphorus of suspended particulate matter in the Yellow Sea were studied based on the analysis of suspended particulate matter, sediments and sinking particles obtained by use of moored sediment traps. The POC: PON ratios indicate that most of the particulate organic matter in the Yellow Sea water column comes from marine life rather than the continent. The vertical fluxes of SPM, POC, PON and POP in the Yellow Sea are much higher than those in other seas over the world, and present a typical pattern in shallow epicontinental seas. The estimated residence time of the bioactive elements showed that the speed of the biogeochemical process of materials in the Yellow Sea is much shorter than that in the open ocean as there was high primary productivity in this region.

Particulate Organic Matter Composition in A Semi-Enclosed Marine System

Spatial and temporal changes in the biochemical composition of particulate organic matter in a semi-enclosed marine system (Stagnone di Marsala, Mediterranean Sea) were studied, on a monthly basis, from January to December 1994, in order to assess nutritional value of suspended particles for benthic suspension feeders. According to previous findings, the study site displayed a strong oligotrophy. Chlorophyll-a accounted for a very low fraction of the total suspended matter pool (0.1%), whereas at least 75% of POC was of detrital/heterotrophic origin. POC: PON ratio values indicate that bacterioplankton biomass accounted for a significant fraction of the total POC pool, displaying values comparable to those of the phytoplankton biomass (phytoplankton to bacterial biomass ratio was about (1). Temporal and spatial changes in the biochemical composition of particulate organic matter were rather limited and related to its sources, the main of which is represented by detrital particles released by the Posidonia oceanica (L.) beds. the comparison between our results and those encountered in other coastal lagoons indicates that the low abundance of suspension-feeding organisms observed in the study area is related to the “quality depression” of particles due to the dilution of high quality compounds (i.e., biopolymeric carbon) in a largely inorganic matrix. This result leads us to conclude that, to reach the same amount of high quality particulate food, a suspension feeder mollusc in the Marsala lagoon would need to filter a sea water volume around 3 times higher than in other Mediterranean coastal lagoons.

Biomass and productivity in Monterey Bay, California: contribution of the large phytoplankton

The contribution of large phytoplankton to the standing stock and productivity of the eastern-boundary ecosystem of Monterey Bay, California, was evaluated during 1992 and 1993, using size fractionation. Eight cruises sampled the variability of the bay both spatially (within the upwelling plume and offshore) and temporally (during upwelling and non-upwelling seasons, El Niño and non-El Niño years). The larger cell sized (>5 μm) autotrophs contributed significantly to chlorophyll, particulate nitrogen, and new and primary productivity in most cruises. This was especially noticeable above a threshold nutrient concentration of 10–12 μM nitrate. Pooling the entire dataset, there were good linear relationships between biomass and productivity parameters measured using GF/F and 5 μm filters. The contribution of the >5 μm size fraction was greatest at higher biomass concentrations and productivity rates, supporting the idea that to reach maximal values, large cells are required. There were linear trends with Chl : PON ratio of close to 1, and 14 C : 15 NO 3 uptake ratio of about 10 in both total and >5 μm size fractions. These large cells are major contributors to carbon and nitrogen productivity in Monterey Bay.

Effects of ultraviolet-B radiation on simultaneous carbon and nitrogen transport rates by estuarine phytoplankton during a week-long mesocosm study

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 199:69-81 (2000) - doi:10.3354/meps199069 Effects of ultraviolet B radiation on simultaneous carbon and nitrogen transport rates by estuarine phytoplankton during a week-long mesocosm study Laure Mousseau1,*, Michel Gosselin1, Maurice Levasseur2, Serge Demers1, Juliette Fauchot1, Suzanne Roy1, Piedad Zulema Villegas1, Behzad Mostajir1 1Institut des sciences de la mer de Rimouski (ISMER), Université du Québec à Rimouski, 310 allée des Ursulines, Rimouski, Québec G5L 3A1, Canada 2Institut Maurice-Lamontagne, Ministère des Pêches et des Océans, CP 1000, Mont-Joli, Québec G5L 3Z4, Canada *Present address: Observatoire Océanologique, BP 28, 06230 Villefranche-sur-Mer, France. E-mail: mousseau@obs-vlfr.fr ABSTRACT: The effect of UV B radiation on photosynthesis and nitrogen uptake by an estuarine phytoplankton community was investigated during a week long experiment, conducted in 8 mesocosms under varying conditions of UV-B radiation: reduced UV-B, natural radiation, and 2 levels of enhanced UV-B. Twice a day, dissolved inorganic carbon (13C) and total dissolved nitrogen (15N) transport rates were estimated simultaneously from in situ incubations. Irrespective of the treatment, phytoplankton biomass (chlorophyll a) and primary production increased over the first 3 d. Subsequently, nitrate and silicate depletion resulted in a decrease in algal biomass and productivity. Enhanced UV-B radiation was deleterious to chlorophyll a specific transport rates of C and N when compared to reduced and natural UV B. The C:N transport ratios, as well as the POC:PON ratios, were generally not affected by enhanced or reduced UV-B. In the enhanced UV-B treatments, carbon transport rates were often significantly higher in the afternoon than in the morning, suggesting that phytoplankton exposed to UV B developed photoprotective mechanisms against UV radiation on a daily basis. A shift in the algal community assemblage from diatoms (>10 µm) to small flagellates (5-10 µm) was observed during the study. Small flagellates were less sensitive to the UV B treatments than diatoms, whose abundance decreased under reduced and enhanced UV B. Results from this study suggest that UV B exposure on a daily basis could change the chlorophyll a specific transport rates of C and N and alter the structure of the phytoplankton community. KEY WORDS: Mesocosms · Nitrogen transport · Photoinhibition · Photosynthesis · Phytoplankton · St. Lawrence Estuary · UV B radiation Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 199. Publication date: June 26, 2000 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 2000 Inter-Research.

Kinetics of phytoplankton decay during simulated sedimentation: Changes in biochemical composition and microbial activity under oxic and anoxic conditions

A series of oxic and anoxic incubations examined the decay of two marine phytoplankton, the diatom Thalassiosira weissffogii and the coccoid cyanobacterium Synechococcus sp, in flow-through systems without macrozooplankton grazers. The major biochemical fractions of algal carbon (protein, carbohydrates, and lipid) were quantified over time together with bacterial abundance and activity. Oxic decay constants of bulk and individual biochemical fractions showed good agreement between both phytoplankters, suggesting that composition at the molecular level within a particular biochemical class does not influence decay rate as much as differences among the major biochemical fractions. Large differences in decay rates did exist among biochemical classes, with carbohydrates utilized most rapidly under oxic conditions, followed by protein and then lipid. Turnover times among the particulate pools ranged from 10.7 days for diatom and cyanobacterial carbohydrates under oxic conditions to over 160 days for cyanobacterial lipids under anoxia, with oxygen having a substantial effect on overall rates of algal carbon decomposition. PON values tracked POC with an average POC:PON ratio of 4.99 ± 0.52 for diatoms and 4.48 ± 0.66 for cyanobacteria throughout the experiments. Bacterial abundances and activity varied substantially over the course of the incubations with greatest activity during periods of greatest particulate loss. Bacterial abundances and metabolism were comparable under oxic and anoxic conditions even though the amount of material degraded under anoxic conditions was significantly less than when oxygen was present, suggesting that oxygen increased rates of particulate material degradation.

Sedimentary organic matter preservation: an assessment and speculative synthesis

The pool of particulate organic matter driven by primary production in western boundary continental margins is known to be smaller than the highly eutrophic upwelling systems of eastern margins. Its production and export, however, can be high compared to productive ocean environments due to inherent specific physical dynamics such as mesoscale instabilities driven by the boundary current. To investigate how such physical process influence nutrients, chlorophyll-a and particulate matter on the outer shelf of the South Brazil Bight, two oceanographic cruises were conducted three months apart (November 2012 and January 2013), both under wind conditions that favor intrusions of South Atlantic Central Water (SACW). Our results showed two distinct hydrographic scenarios derived by the relative positions of oceanographic fronts in the outer shelf and shelf break region, associated with the Brazil Current (BC). In November 2012, the oligotrophic Tropical Water occupied a larger area of the continental shelf. Low nutrients and chlorophyll-a concentrations were found, typical of a regenerated production system. In contrast, maximum concentration of particulate matter and particulate inorganic carbon occurred at deeper layers in this period, together with low POC:PON ratio — probably from sediment resuspension. In January 2013, a strong shelf break upwelling was detected that enhanced SACW intrusion, notably increasing nutrient availability in the euphotic zone and the chlorophyll-a concentration at deeper layers. These deep chlorophyll maximum layers contribute to the production and accumulation of particulate organic carbon and nitrogen under these conditions. BC mesoscale instabilities appear to act as a particulate matter transport and export agent to the deep waters throughout the South Brazil Bight outer shelf.

Developmental changes in rat brain monoamine metabolism and β-adrenoceptor subtypes after chronic prenatal exposure to propranolol

The aim of this study was to investigate whether a chronic prenatal β-blockade can alter the maturation of the noradrenergic system in the rat brain. Pregnant female and adult male rats were treated for 10 days with the β-antagonist propranolol dissolved in the drinking water (40–50 mg/kg/day). Direct and long-term effects on β-adrenoceptors and monoamine metabolism in various rat brain regions were determined. After the prenatal treatment the propranolol level in the foetal brain was 0.9 μg/g, while in the adult brain 2.0 μg/g was present. The foetal β1-receptors were significantly up-regulated by propranolol (200%), whereas the β2-receptor number remained unaltered. On postnatal days 4 and 21 the number of both β-subtypes was the same as that of controls. Noradrenaline, its metabolite 3-methoxy-4-hydroxyphenylglycol and their ratio were unaltered directly after the prenatal treatment. In the PN 21 offspring, however, the metabolite level had increased in the frontal cortex (+17%) and hippocampus (+32%), and the ratio in the hippocampus (37%) and medulla pons (+34%). Prenatal treatment also induced a significant increase of the 5-hydroxyindolacetic acid·5-hydroxytryptamine ratio (+15%) in the medulla pons at GD 21. No direct or lasting effects were found on dopamine metabolism. Propranolol treatment of adult rats gave no direct changes in monoamine metabolism. We concluded that chronic prenatal propranolol exposure (a) reversibly up-regulates foetal β1-adrenoceptors, and (b) increases the NA activity in the brain in later life.

Nitrate and phytoplankton production in southern California coastal waters1

The transport of nitrate into the euphotic zone appears to be a major factor regulating the standing stock and production of phytoplankton in southern California coastal waters. The evidence is as follows. 1) The rate of photosynthetic carbon assimilation is proportional to the rate of nitrate assimilation and to the ratio of nitrate:total N assimilated. 2) The phytoplankton standing stock (g C·m−3) and its production rate are related to the depth of the vertical nitrate concentration gradient. 3) The chemical composition of the particulate organic matter, as the POC:PON ratio, is related to the carbon:nitrogen assimilation ratio of the phytoplankton. 4) Regenerated production, measured as ammonium assimilation, is proportional to the nitrate assimilation rate, implying parallel and concurrent increases in the production of heterotrophic microplankton and phytoplankton attending new inputs of nitrate into the euphotic zone. 5) The vertical diffusion of nitrate, when calculated from the vertical nitrate concentration gradients and nitrate assimilation rates, appears to give reasonable estimates of the vertical eddy diffusivity coefficient for nitrate.