Phytoplankton Debris Research Articles

Heterogeneous coupling of δ13Corg and δ13Ccarb during the Shuram Excursion: Implications for a large dissolved organic carbon reservoir in the Ediacaran ocean

The Ediacaran ocean recorded the largest negative carbonate carbon isotope (δ13Ccarb) excursion in Earth's history, the Shuram Excursion (SE). The relatively invariant character of organic carbon isotope (δ13Corg) profiles during the SE has been attributed to buffering by a large dissolved organic carbon (DOC) reservoir in the ocean. However, recent studies suggest that the DOC buffering may have been highly heterogeneous, a hypothesis that can be tested by assessing variability in the spatial and temporal ranges of δ13Corg buffering during the SE. In this study, we evaluated δ13Corg and δ13Ccarb records from multiple regions globally to test the heterogeneous buffering hypothesis. Making use of a high-precision astrochronological framework, we found that the buffering effect of DOC persisted for ∼2.7 Myr in Oman, ∼4.9 Myr in South China, and ∼5.9 Myr in Australia, demonstrating its temporal heterogeneity. Heterogeneous buffering is also demonstrated at a small spatial scale for South China sections based on a correlation framework subdividing the SE into three intervals: EN3a (δ13Ccarb decline from baseline to nadir), EN3b (δ13Ccarb stabilized at nadir), and EN3c (δ13Ccarb recovery from nadir value). The duration of δ13Corg buffering increased with water depth from shallow neritic to deep pelagic areas. The buffering effect terminated within EN3a in inner-shelf areas, within EN3b in an intra-shelf basin, and within EN3c in slope areas. Spatial variation in the offset between δ13Ccarb and δ13Corg values (Δ13C(carb-org)) is consistent with multiple sources of sedimentary organic matter. An average of ∼26 ‰ in inner-shelf areas implies mainly fresh phytoplankton debris, whereas an average of ∼18 ‰ in slope areas is consistent with dominance of DOC, which is thought to have been present in abundance in deeper anoxic watermasses. Thus, our study supports a large DOC reservoir in the late Ediacaran ocean that led to heterogeneous buffering during the SE at both basinal and global scales. Large shallow-to-deep oceanic δ13Ccarb and δ13Corg gradients of similar magnitude existed both before and during the SE, indicating that the circulation and productivity dynamics of the Ediacaran ocean were not significantly changed by the SE. The downward expansion of oxidant-rich surface watermasses during the SE improved the ventilation of shelf oceans while leaving the deep ocean anoxic, setting the stage for rapid biological evolution on continental shelves during the Cambrian Explosion.

Subducted organic matter buffered by marine carbonate rules the carbon isotopic signature of arc emissions

Ocean sediments consist mainly of calcium carbonate and organic matter (phytoplankton debris). Once subducted, some carbon is removed from the slab and returns to the atmosphere as CO2 in arc magmas. Its isotopic signature is thought to reflect the bulk fraction of inorganic (carbonate) and organic (graphitic) carbon in the sedimentary source. Here we challenge this assumption by experimentally investigating model sediments composed of 13C-CaCO3 + 12C-graphite interacting with water at pressure, temperature and redox conditions of an average slab–mantle interface beneath arcs. We show that oxidative dissolution of graphite is the main process controlling the production of CO2, and its isotopic composition reflects the CO2/CaCO3 rather than the bulk graphite/CaCO3 (i.e., organic/inorganic carbon) fraction. We provide a mathematical model to relate the arc CO2 isotopic signature with the fluid–rock ratios and the redox state in force in its subarc source.

Metagenomic evidence for the microbial transformation of carboxyl-rich alicyclic molecules: A long-term macrocosm experiment

Carboxyl-rich alicyclic molecules (CRAMs) widely exist in the ocean and constitute the central part of the refractory dissolved organic matter (RDOM) pool. Although a consensus has been reached that microbial activity forms CRAMs, the detailed molecular mechanisms remain largely unexplored. To better understand the underlying genetic mechanisms driving the microbial transformation of CRAM, a long-term macrocosm experiment spanning 220 days was conducted in the Aquatron Tower Tank at Dalhousie University, Halifax, Canada, with the supply of diatom-derived DOM as a carbon source. The DOM composition, community structure, and metabolic pathways were characterised using multi-omics approaches. The addition of diatom lysate introduced a mass of labile DOM into the incubation seawater, which led to a low degradation index (IDEG) and refractory molecular lability boundary (RMLB) on days 1 and 18. The molecular compositions of the DOM molecules in the later incubation period (from day 120 to day 220) were more similar in composition to those on day 0, suggesting a rapid turnover of phytoplankton debris by microbial communities. Taxonomically, while Alpha proteobacteria dominated during the entire incubation period, Gamma proteobacteria became more sensitive and abundant than the other bacterial groups on days 1 and 18. Recalcitrant measurements such as IDEG and RMLB were closely related to the DOM molecules, bacterial community, and Kyoto encyclopaedia of Genes and Genomes (KEGG) modules, suggesting close associations between RDOM accumulation and microbial metabolism. KEGG modules that showed strong positive correlation with CRAMs were identified using a microbial ecological network approach. The identified KEGG modules produced the substrates, such as the acetyl-CoA or 3‑hydroxy-3-methylglutaryl-CoA, which could participate in the mevalonate pathway to generate the precursor of CRAM analogues, isopentenyl-PP, suggesting a potential generation pathway of CRAM analogues in bacteria and archaea. This study revealed the potential genetic and molecular processes involved in the microbial origin of CRAM analogues, and thus indicated a vital ecological role of bacteria and archaea in RDOM production. This study also offered new perspectives on the carbon sequestration in the ocean.

Microbial communities in the nepheloid layers and hypoxic zones of the Canary Current upwelling system.

Eastern boundary upwelling systems (EBUSs) are among the most productive marine environments in the world. The Canary Current upwelling system off the coast of Mauritania and Morocco is the second most productive of the four EBUS, where nutrient‐rich waters fuel perennial phytoplankton blooms, evident by high chlorophyll a concentrations off Cape Blanc, Mauritania. High primary production leads to eutrophic waters in the surface layers, whereas sinking phytoplankton debris and horizontally dispersed particles form nepheloid layers (NLs) and hypoxic waters at depth. We used Catalyzed Reporter Deposition Fluorescence In Situ Hybridization (CARD‐FISH) in combination with fatty acid (measured as methyl ester; FAME) profiles to investigate the bacterial and archaeal community composition along transects from neritic to pelagic waters within the “giant Cape Blanc filament” in two consecutive years (2010 and 2011), and to evaluate the usage of FAME data for microbial community studies. We also report the first fatty acid profile of Pelagibacterales strain HTCC7211 which was used as a reference profile for the SAR11 clade. Unexpectedly, the reference profile contained low concentrations of long chain fatty acids 18:1 cis11, 18:1 cis11 11methyl, and 19:0 cyclo11–12 fatty acids, the main compounds in other Alphaproteobacteria. Members of the free‐living SAR11 clade were found at increased relative abundance in the hypoxic waters in both years. In contrast, the depth profiles of Gammaproteobacteria (including Alteromonas and Pseudoalteromonas), Bacteroidetes, Roseobacter, and Synechococcus showed high abundances of these groups in layers where particle abundance was high, suggesting that particle attachment or association is an important mechanisms of dispersal for these groups. Collectively, our results highlight the influence of NLs, horizontal particle transport, and low oxygen on the structure and dispersal of microbial communities in upwelling systems.

Simulated bioavailability of phosphorus from aquatic macrophytes and phytoplankton by aqueous suspension and incubation with alkaline phosphatase

Bioavailability of phosphorus (P) in biomass of aquatic macrophytes and phytoplankton and its possible relationship with eutrophication were explored by evaluation of forms and quantities of P in aqueous extracts of dried macrophytes. Specifically, effects of hydrolysis of organically-bound P by the enzyme alkaline phosphatase were studied by use of solution 31P-nuclear magnetic resonance (NMR) spectroscopy. Laboratory suspensions and incubations with enzymes were used to simulate natural releases of P from plant debris. Three aquatic macrophytes and three phytoplankters were collected from Tai Lake, China, for use in this simulation study. The trend of hydrolysis of organic P (Po) by alkaline phosphatase was similar for aquatic macrophytes and phytoplankton. Most monoester P (15.3% of total dissolved P) and pyrophosphate (1.8%) and polyphosphate (0.4%) and DNA (3.2%) were transformed into orthophosphate (14.3%). The major forms of monoester P were glycerophosphate (8.8%), nucleotide (2.5%), phytate (0.4%) and other monoesters P (3.6%). Proportions of Po including condensed P hydrolyzed in phytoplankton and aquatic macrophytes were different, with the percentage of 22.6% and 6.0%, respectively. Proportion of Po hydrolyzed in debris from phytoplankton was approximately four times greater than that of Po from aquatic macrophytes, and could be approximately twenty-five times greater than that of Po in sediments. Thus, release and hydrolysis of Po, derived from phytoplankton debris would be an important and fast way to provide bioavailable P to support cyanobacterial blooming in eutrophic lakes.

Calcium, magnesium and strontium cycling in stratified, hardwater lakes: Lake Kinneret (Sea of Galilee), Israel

In stratified hardwater lakes, calcite crystallization in the epilimnion and partial dissolution in the hypolimnion play important roles in the cycling of Ca2+ in the water column. Mg2+ and Sr2+ coprecipitate with this mineral, to be released together with Ca2+ upon its dissolution. Here, we focus on Lake Kinneret (Sea of Galilee, Israel), a stratified, warm, hardwater lake, searching for an interpretable, high resolution picture of the processes that drive Ca2+, Mg2+ and Sr2+cycling in this and similar lakes elsewhere.In total, 1428 water samples were collected from the lake, and another 81 samples were collected from the Jordan River and two small streams discharging into it, covering a full monomictic cycle from December 2001 through March 2003. Particulate material was retrieved from sediment traps in the hypolimnion. The water samples were analyzed for Na+, K+, Mg2+, Ca2+, Sr2+, Cl−, SO42−, HCO3− and Br−, and the trapped particulates were examined under SEM and analyzed for their Ca, Mg, and Sr content. Individual calcite crystals within the particulate material underwent LA-ICP-MS analysis for Ca, Mg, and Sr.Downward transport of Ca2+ involves crystallization of calcite in the epilimnion, followed by its settling through the water column, followed by its partial dissolution in the hypolimnion. Magnesium and Sr2+ follow Ca2+ by coprecipitation in calcite and are released upon its dissolution in the hypolimnion. Upward cycling of the three solutes occurs through an admixture of the hypolimnetic water into the epilimnion during thermocline deepening, terminated by overturn of the lake.Removal rates of Mg2+ and Sr2+ from the lake, relative to that of Ca2+, and the water–calcite distribution coefficients, DMg and DSr, were calculated from the analyses using: (1) epilimnion water and ‘bulk’ particulates; (2) epilimnion water only; and (3) epilimnion water and calcite crystals in the particulates. The DSr values obtained were internally consistent (0.194±5.9%, 0.22–0.28, and 0.204–0.232, respectively); however, the DMg value for the ‘bulk’ particulates (0.0477) was ∼6 times higher than that corresponding to calcite crystals included therein (0.00841). This difference is attributed to phytoplankton debris in the ‘bulk’ particulates and should be of concern to geochemists using Mg/Ca ratios in limestone to reconstruct ancient aquatic environments.The cycling of Ca2+, Mg2+ and Sr2+ in the stratified lake is monitored by Mg/Ca vs. Sr/Ca regression diagrams, where each line represents the water column composition on a specific date. The distance of the data points from the initial (mixed lake) coordinates reflects the fractionation of Ca2+, Mg2+ and Sr2+ after the onset of stratification. The regression lines rotate in an orderly anticlockwise direction in response to the high calcite flux from the epilimnion in spring and the higher rate of Mg2+ replenishment than that of Sr2+, compensating for their loss in calcite. The release of Mg2+ and Sr2+ from dissolving calcite in the hypolimnion, at an Mg/Sr ratio (7.5eq/eq) much lower than that in the surrounding water (∼160eq/eq), lends additional support to the anticlockwise rotation. Reversal of rotation occurs in summer, when calcite crystallization and the freshwater supply slow down, and brackish and saline water sources take control over the Mg/Sr ratio in the lake. Subsequent turnover and mixing of the lake in winter reset the Mg/Ca and Sr/Ca ratios to their original values before the next stratification.

Diatom valve distribution and sedimentary fatty acid composition in Larsen Bay, Eastern Antarctica Peninsula

During austral summer 2006–2007, five sediment cores were recovered from the Eastern Antarctic Peninsula (EAP) continental shelf. Microscopic observations and sediment fatty acid (FA) composition analyses were carried out to investigate whether the drastic changes at the sea surface in EAP may be reflected in the sedimentary record. A sharp decrease in the number of diatom valves was observed below 2 cm depth. This difference between the upper 2 cm of sediment and the deeper part of the sediment column was attributed to the drastic change in the upper water column conditions after the collapse of the ice shelves, which allowed the arrival of phytoplankton debris and fresh organic matter to the sea floor in EAP. The presence of bacterial-, zooplankton- and detrital-related FA throughout EAP cores suggests that there has been an input of older and more refractory organic matter into the region, presumably by lateral transport before the Larsen ice shelves disintegration.

Production of colloidal organic carbon and trace metals by phytoplankton decomposition

Colloids are important intermediates and can considerably influence the biogeochemical cycling of organic carbon and trace metals in aquatic systems. Previous studies have determined the release of carbon and trace elements from decomposing phytoplankton debris, but the degradation of biogenic particles to colloids and their significance in metal and carbon cycling remain unknown. In this study, we measured the release of carbon and trace elements (Cd, Cr, Se, and Zn) from the debris of two phytoplankton (diatom Thalassiosira pseudonana, and dinoflagellate Prorocentrum minimum) into a colloidal phase (operationally defined as 5 kDa–0.2 mm). In general, Cd, Se, and Zn were released at a faster rate and Cr was released at a slower rate than the release of C from the decomposing debris into the dissolved phase (<0.2 mm). Release of trace metals appeared to closely follow C release. The release rate coefficients of Cd, Cr, Se, Zn, and C in the two phytoplankton debris with microbial addition were 1.67–1.68 d−1 for Cd, 0.147–0.239 d−1 for Cr, 0.712–0.845 d−1 for Se, 0.765–1.14 d−1 for Zn, and 0.443–0.512 d−1 for C. The percentages of trace elements (Cr, Se, Zn) and C associated with the colloidal phase were relatively high within the first 5 d ofdecomposition. After 5 d, the fraction of colloidal trace elements in the <0.2–µm dissolved phase was 5–10% for Cd, 13–52% for Cr, 13–28% for Se, 14–30% for Zn, and 16–41% for C in the diatom decomposing experiment; and 4–9% for Cd, 15–62% for Cr, 15–31% for Se, 3–27% for Zn, and 22–38% for C in the dinoflagellate decomposing experiment, respectively. The partitioning of metals in the colloidal phase was not greatly affected by the microbial activity. Although the overall percentage of organic carbon release was related to that of metals from decomposing debris, no significant correlation between the percentages of colloidal metals and colloidal organic carbon was observed, implying that organic C and metals have different partitioning behavior during their release from decomposing phytoplankton debris. Our study demonstrated that the decomposition of biogenic particles may contribute considerably to the production of colloids in marine environments.

The surface ocean productivity response of deeper water benthic foraminifera in the Atlantic Ocean

We test the relationship of deep sea benthic foraminiferal assemblage composition to the surface ocean productivity gradient in the low latitude Atlantic Ocean using 81 surface sediment samples from a water depth range between 2800 and 3500 m. The samples are selected so that the surface ocean productivity gradient, controlling the flux of organic carbon to the seabed, will be the most important environmental variable. The first two principal components of the assemblage data account for 73% of data variance and are clearly linked to the productivity gradient across the Atlantic. These components show that under higher productivity the assemblages contain a higher abundance of Uvigerina peregrina, Melonis barleeanum, Globobulimina spp. and other taxa with probable infaunal microhabitats. Alabaminella weddellensis, a species linked to episodic phytoplankton debris falls, is also important in these assemblages. As productivity decreases there is a regular shift in assemblage composition so that low productivity assemblages are dominated by Globocassidulina subglobosa and several Cassidulina species along with Epistominella exigua. We hypothesize that these taxa are epifaunal to very shallow infaunal since nearly all organic carbon oxidation occurs near the sediment-water interface in low productivity settings. Discriminant function analysis of the foraminiferal assemblages, with groups selected on the basis of surface ocean productivity, shows clear separation among five productivity levels we used. This analysis demonstrates that productivity variations have a strong influence on assemblage composition. Finally, we used two groups of samples from the Rio-Grande Rise representing water depths from 2007 to 2340 m and 2739 to 3454 m to test for effects produced by changing water depth. All these samples are from a low productivity region and represent nearly identical environmental conditions. Although the low productivity nature of all the Rio-Grande Rise samples is obvious, there are assemblage differences between our depth groups. We cannot account for the assemblage differences with changes in organic carbon flux, dissolution effects or other physical/chemical properties of the ocean. Thus there are as yet unidentified factors related to water depth which cause some assemblage variation in the low productivity setting we investigated.

Utilization of phytoplankton in seston aggregates from the Elbe estuary, Germany, during early degradation processes

A laboratory device was used to simulate the environmental conditions in a seston layer of about 1 mm thickness, similar to those in aggregates of the open water of the Elbe estuary, Germany. During 98 h of oxic, suboxic and anoxic incubation, microbial degradation was investigated by measuring both changes in the chemlcal compos~tlon of the particulate organic carbon (POC) and heterotrophic microbial activities. Mineralization of the POC at 15°C occurred at mean rates of 16 under oxic, 26 under suboxic, and 0.24 pm01 cm-3 d-' under anoxic conditions. Different respiration processes accounted for ratios of carbon degradation equal to 1 7 for oxygen:nitrate, 430 for nitrate:manganese, and 3.5 for Mn(IV):Fe(lII) Dunng o x ~ c and suboxic incubation, particulate combined amino acids (PCAA) were preferred as an organic substrate, and PCAA:C ratios decreased from about 0.12 to 0.02. A total of 85% of the PCAA wds degraded within 56 h including PCAA and dissolution of silica from the cell wall material of diatoms; the remaining amlno acids were assumed to be those from active bacteria. Chlorophyll a (chl a ) was more resistant to degradation than total POC below a threshold value of 60 p M 02, which resulted in an increase of chl a.C ratlos up to 37. A decrease in the availability of particulate substrates for heterotrophic decomposition was expressed as an accumulation of glycine and serine and a depletion in aspartic and glutamatic a c ~ d in the PCAA. During anoxic incubation PCAA decreased by only 18% and remained unchanged in composition. Along the longitudinal profile of the freshwater section of the Elbe estuary, gradual decomposition of the seston material during summer downstream transport was followed by changes in composition similar to those observed in the oxic laboratory experiments. The results indicate that phytoplankton debris that is not available as a substrate for microorganisms in sediments and small suspended particles is rapidly degraded within seston aggregates.

Aerobic degradation of phytoplankton debris dominated by Phaeocystis sp. in different physiological stages of growth

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 12:11-19 (1997) - doi:10.3354/ame012011 Aerobic degradation of phytoplankton debris dominated by Phaeocystis sp. in different physiological stages of growth Osinga R, de Vries KA, Lewis WE, van Raaphorst W, Dijkhuizen L, van Duyl FC The aerobic degradation of phytoplankton debris collected in Dutch coastal waters on 2 days in 1991 (15 April and 8 May), representing 2 physiological stages of a phytoplankton spring bloom dominated by Phaeocystis sp., was studied in batch culture experiments. The bacterial production and the concentrations of particulate organic carbon (POC) and dissolved organic carbon (DOC) were monitored over a period of 102 d. Bacterial numbers and biomass were followed for 35 d. All experiments showed a rapid metabolic response of bacteria and a sharp decrease in the concentration of POC and DOC during the first days of the experiments. Thereafter, bacterial production rates remained constant, and POC and DOC decreased slowly. Apparently, the phytoplankton debris consisted of a labile, rapidly degradable fraction and a refractory, slowly degradable fraction. The labile fraction comprised approximately 50% of the debris, and was degraded with a bacterial carbon conversion efficiency of between 10 and 20%. There were no indications that antibiotic compounds present in the algal debris inhibited the degradation. Acrylate, a proposed antibiotic compound which was present in the algal debris, was rapidly degraded in a control experiment. The percentage of the material that had been degraded after 102 d was highest in the experiment with material collected in May. It was concluded that during the early phase of the bloom, more refractory compounds are produced. Phaeocystis sp. · Bacterial degradation · Organic carbon Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 12, No. 1. Publication date: January 30, 1997 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 1997 Inter-Research.

Release rates of trace elements and protein from decomposing planktonic debris. 1. Phytoplankton debris

Release rates of trace elements and protein from decomposing planktonic debris. 1. Phytoplankton debris

The role of Nuta (large amorphous particles) as a nutrient regenerator in Osaka Bay

Large amorphous particles (Nuta) observed in coastal areas after phytoplankton blooms and red tide outbreaks were collected by Nuta traps. These particles are always thickly attached to mooring ropes and/or fishing nets. From the decomposition experiments of Nuta and the sinking particles, dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) regenerations were active in Nuta, but were not active in sinking particles. In Nuta, regeneration abundances during 10 days were 567 µg-N/mg of initial particulate organic nitrogen (PON), and 583 µg-P/mg of initial particulate phosphorus (PP), respectively. Thus DIP was more regenerated from Nuta than DIN. Ten days integral regeneration abundances of DIN and DIP from Nuta were estimated to be 36% and 79% of in situ DIN and DIP standing stocks, respectively. Nuta contributes an important role of nutrient regeneration particularly DIN, in coastal water. Carbon and nitrogen stable isotope ratios of suspended particles, sinking particles and Nuta indicated that these three different type of particles were almost the same origin, and thus Nuta in the coastal water should be made from phytoplankton debris.

Degradation and elemental release rates from phytoplankton debris and their geochemical implications

The diatom Thalassiosira pseudonana was held without nutrients in the dark for 22 d; release rates of carbon and seven metals from the cells were determined with radiotracers. Cellular C was lost faster at 18°C (3.6% d−1) than at 4°C (1.0% d−1) due to higher microbial activity at 18°C. C loss rates decreased (from 9.7% d−1 at 18°C and 2.1% d−1 at 4°C) after 7 d. Formalin (24 mM) and HgCl2 (0.9 mM) inhibited microbial activity as indicated by 14CO2 evolution; NaN3 (154 mM) was less effective. Poison‐treated cells leached 33–39% of their C (as DOC) and large quantities of Cd, Se, Zn, and Ag.Cd, Se, and Zn, primarily in a soluble fraction in the cells, were released at about the same rate as C and were affected by microbial activity and temperature. In contrast, Ag, Am, Ce, and Co were retained to a much greater extent by the decomposing cells, their release was slower than that of C, and temperature and microbial activity had negligible effects on their retention. The results suggest that Cd, Se, and Zn will be rapidly recycled from planktonic debris in surface waters, while Ce, Am, Ag, and Co will be transported by phytoplankton aggregates sinking from surface waters.

Organic matter in Cretaceous chalks from eastern England

Upper Cretaceous chalks from eastern England and northern France and two representative chalks of post-Cretaceous age contain organic matter in the form of humic and fulvic acids, humin and bitumen. Levels of total humic matter range from ∼ 0.01% in the white chalks (> 95% CaCO 3) to 0.1% in the clayey and phosphatic chalk facies; they reach 1% in a sample of the Black Band (marking the Cenomanian-Turonian boundary) and in one of the post-Cretaceous samples (Eocene chalk from Israel). Less than 30% of the total humic matter in the samples was amenable to direct extraction, the bulk (and all the bitumen) being obtainable only after dissolution of carbonates or of all mineral phases (as humin). This points to a diffuse distribution of organic matter in the chalks, some being intracrystalline in the calcite, some being associated with clays. H/C atomic ratios of the humic materials range from 0.6 to 1.6 and are positively correlated with N/C (range 0.02–0.09). Humic acids most susceptible to direct extraction, especially those from the phosphatic chalks, exhibit the highest H/C and N/C ratios. This trend correlates with structural information obtained using Fourier-transform infra-red and pyrolysis-mass spectrometry (PY-MS). Both show that the humic acids are predominantly aromatic structures but those with the higher H/C and N/C ratios contain an abundance of aliphatic and peptide-type moieties. Other structural elements identified by PY-MS included methoxyphenols (derived from lignins) and acetamide (derived from n-acetylaminosugars, e.g. chitin). Humic acids with the highest N/C ratios contain up to 20 wt.% of hydrolysable amino acids, although the relative abundances of different amino acids in all the samples was the same and congruent to that of humic acids and phytoplankton debris from Recent sediments. Bitumens from the chalks consisted mostly (>80%) of high-molecular-weight compounds that were not subject to further analysis. Chromatography and gas chromatography-mass spectrometry showed that the residual low-molecular-weight fractions were dominated by the presence of normal and branched alkanes ( n-isomers in the range C 12–C 23) and by n-fatty acids (especially C 14, C 16 and C 18 types). The release of methoxyphenols during pyrolysis shows that all the humic acids (particularly those with low H/C ratios) contain some terrestrially derived organic matter. This probably forms the aromatic skeleton of the humic acids. Aliphatic and peptide-type moieties, mainly in the samples with higher H/C and N/C ratios, together with the amino acid patterns, provide evidence that this skeleton is augmented by marine-derived structural units. The presence of marine, and more particularly of plankton-derived organic matter in the humic acids, is substantiated by the n-alkane and n-fatty acid data. Humic acids from the chalks exhibit a negative relation between their H/C and O/C ratios, in part a reflection of the presence of terrestrial components. However, this trend also suggests microbial oxidation of lipid and peptide material in the humic acids in the original chalk sediments. Low levels of sulphur indicate that the most extensively altered humic materials (mainly from the white chalks) were subject to oxidation in an aerobic microbial regime. High levels of sulphur in lipid/peptide-rich humic acids from the phosphatic and Israeli chalks reflect preferential preservation due to less active anaerobic microbial conditions. The presence of humic acids (rather than kerogen) and the predominance of polymeric material in the bitumens shows that all of the chalks examined are catagenically immature. This is not unexpected in view of their burial history.

Correlation of the Canol Formation source rock with oil from Norman Wells

The source of the oil at Norman Wells has long been assumed to have been the Canol Formation and/or the Bluefish Member of the Hare Indian Formation. These two units are stratigraphically above and below the Kee Scarp Formation reservoir unit respectively, and are both bituminous shales. A wide range of analytical techniques including Rock-Eval pyrolysis, solvent extraction and fractionation, capillary gas chromatography, gas chromatography-mass spectrometry, and white light and fluorescence microscopy has been used to characterize core samples of these two units and two samples of crude oil from the Norman Wells field. Most of the analytical techniques were insufficiently refined to either differentiate the extracts from each other or to make a definitive oil/source rock correlation. Collision activated decomposition coupled with multiple ion detection mass spectrometry (GC-MS-MS) did provide sufficient chemical compositional detail of the oils and the two potential sources to demonstrate that the Canol Formation has been the effective source of the Norman Wells oil whereas the Bluefish Member has not. Petrological analysis of the organic fractions also indicates that although the bulk organic composition of both units may be classified as Type II organic matter, significant differences exist between them. The Bluefish Member contains substantial amounts of megaspores, whereas the organic matter in the Canol Formation is largely phytoplankton debris. The level of thermal maturity of the core samples ranges from immature to moderately mature in the vicinity of the Norman Wells field to overmature for the samples obtained to the west and north of the field. The level of thermal maturity of the oil was observed to be somewhat higher than that of the samples of the source formation directly above the field. It was thus inferred that some lateral migration from more mature areas has occurred but the extent of this migration was not necessarily more than a few to tens of kilometers.

Phytoplankton crops, bacterial metabolism and oxygen in saanich inlet, a fjord in Vancouver Island, British Columbia

Phytoplankton crops in Saanich Inlet were characterized by their content of photosynthetic pigments and by their taxonomic compositions, from early April to mid-December, 1981. Crop sizes were correlated to particle volumes, bacterial activities, and oxygen concentrations at all depths to test the hypothesis that the degradation of sinking phytoplankton debris by bacterial production results in anoxia. Particles produced during the spring bloom were rich in chlorophyll a and pheopigments, which disappeared as particles sank deeper in the water column. The volume of particles, with sizes ranging from 2.0 to 40 μm, was dominated by those with a mean size of about 32 μm. Qualitatively, many of the particles were frustules of the two diatom genera, Thalassiosira and Chaetoceros, which dominated crops in the euphotic zone. No temporal changes in either qualities or quantities of photosynthetic pigments were observed in anoxic sediments. A positive correlation between particle volume and bacterial production was observed. However, no correlation between production and changes in dissolved O 2 was seen in the deep water prior to mid-June. Further observations were masked by flushing that occurred in August and may have begun as early as mid-June.

Rate of Degradation and Efficiency of Conversion of Phytoplankton Debris by Marine Micro-Organisms

Rate of Degradation and Efficiency of Conversion of Phytoplankton Debris by Marine Micro-Organisms