Particulate Organic Matter In Seawater Research Articles

18S rRNA gene sequences of leptocephalus gut contents, particulate organic matter, and biological oceanographic conditions in the western North Pacific

Eel larvae apparently feed on marine snow, but many aspects of their feeding ecology remain unknown. The eukaryotic 18S rRNA gene sequence compositions in the gut contents of four taxa of anguilliform eel larvae were compared with the sequence compositions of vertically sampled seawater particulate organic matter (POM) in the oligotrophic western North Pacific Ocean. Both gut contents and POM were mainly composed of dinoflagellates as well as other phytoplankton (cryptophytes and diatoms) and zooplankton (ciliophoran and copepod) sequences. Gut contents also contained cryptophyte and ciliophoran genera and a few other taxa. Dinoflagellates (family Gymnodiniaceae) may be an important food source and these phytoplankton were predominant in gut contents and POM as evidenced by DNA analysis and phytoplankton cell counting. The compositions of the gut contents were not specific to the species of eel larvae or the different sampling areas, and they were most similar to POM at the chlorophyll maximum in the upper part of the thermocline (mean depth: 112 m). Our results are consistent with eel larvae feeding on marine snow at a low trophic level, and feeding may frequently occur in the chlorophyll maximum in the western North Pacific.

Seasonal changes in particulate organic matter (POM) concentrations and properties measured from deep areas of the Baltic Sea

Summary In seawater particulate organic matter (POM) serves as a food source for heterotrophic bacteria and zooplankton and is a source of dissolved organic compounds and nutrients. POM plays a critical role in transporting carbon to marine sediments where a fraction of it is buried in subsurface sediments and thus avoids conversion to carbon dioxide on shorter time scales. Distribution and properties of POM were investigated in the Baltic Proper from 2013 to 2015. Particulate organic carbon (POC) was used to investigate POM sources and dynamics. Stable carbon isotopes (δ13C), elemental composition (C, N), chlorophyll a and POM contribution to suspended particulate matter (SPM) were also measured and interpreted. The water column exhibited concentrations ranging from 0.2 mg POC/l (deep water layer – DWL, cold season – CS) to 1.7 mg POC/l (surface water layer – SWL, warm season – WS). POM represented 0.15 to 0.45 of SPM during respective cold and warm seasons. Stable carbon isotopes (δ13CPOC) ranged from −22.5‰ (WS) to −28.0‰ (CS), while the POC/Chl a ratio ranged from 180 g/g (SWL-WS) to 300 g/g (DWL-CS). Seasonal changes were attributed to high primary production in the SWL during the WS, which represented a major POM source. Continuous mineralization/sedimentation throughout the water column constituted a major POM sink.

Autoxidation as a major player in the fate of terrestrial particulate organic matter in seawater

AbstractThe Rhône River plays a major role in the Mediterranean Sea, being both its main freshwater source and its major particulate matter provider. This survey of the fate of terrestrial particulate organic matter (POM) was conducted along the salinity gradient of the Rhône River plume, between 2012 and 2014. It revealed that autoxidation acts rapidly and intensely upon the POM's arrival at sea, with α‐amyrin and β‐amyrin autoxidation rates going from 12.9 ± 2.9% to 45.0 ± 6.4% and 10.7 ± 4.0% to 50.3 ± 4.4%, respectively, between fresh water (salinity 0) and seawater (salinity 38). These compounds, being unambiguous markers of the terrestrial origin of POM, allow us to unequivocally characterize the POM as terrestrial. While it was originally believed that a desorption of redox‐active trace metal ions was the favoring factor that kick‐started this intense autoxidation, this study evidences no trace metal desorption in the Rhône River mixing zone and hence no correlation between high autoxidation rates and the presence of trace metal ions. Autoxidation rates however were very well correlated with salinity levels within the river plume, with r2 reaching 0.801, 0.962, and 0.943 for sitosterol, α‐amyrin, and β‐amyrin, respectively, in November 2014.

Practical wet oxidation experiment to determine concentrations of particulate organic matter in seawater

The report presents results of experiments testifying to the possibility of using wet oxidation to determine the concentrations of organic carbon in marine particulate matter. We describe a method for eliminating the measurement error caused by the influence of chlorides on the processes of dichromate oxidation of organic matter. We present an equation to calculate the concentration of organic carbon depending on that of sodium chloride.

Seasonal variation of stable isotope ratios of size-fractionated zooplankton in the Bay of Marseille (NW Mediterranean Sea)

Stable isotope ratios of six size fractions of zooplankton (80 to >2000 µm) were analyzed seasonally in 2009-2010 at the SOMLIT site in the Bay of Marseille. Isotopic ratios generally increased with zooplankton size. The highest δ15N values were observed in the 1000-2000 µm fraction. The largest size class (>2000 µm), dominated by gelatinous plankton, had lower δ15N values due to the low isotopic signatures of most of these organisms. In the larger size fractions (>1000 µm), isotopic ratios were measured at the taxon level. Brachyuran, stomatopod, teleost and cephalopod larvae showed the highest δ15N values, and salps and pteropods the lowest ones. Lower values of both δ13C and δ15N were recorded in winter and spring than in summer and autumn for all fractions. Seasonal variations were consistent with the fluctuations of environmental parameters (temperature, nutrients, Chl a concentration) and were related to phytoplankton and seawater particulate organic matter (POM) composition. Stable isotope and flow cytometry analysis of water POM indicated that sewage wastewater particles were mixed with marine phytoplankton at the SOMLIT site and transferred up into the zooplanktonic food web.

Terrestrial trophic subsidy in sandy beaches: evidence from stable isotope analysis in organic matter sources and isopod Excirolana armata

AB Aquatic Biology Contact the journal Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AB 14:129-134 (2012) - DOI: https://doi.org/10.3354/ab00392 NOTE Terrestrial trophic subsidy in sandy beaches: evidence from stable isotope analysis in organic matter sources and isopod Excirolana armata Leandro Bergamino*, Diego Lercari, Omar Defeo Unidad de Ciencias del Mar, Facultad de Ciencias, Iguá 4225, Montevideo 11400, Uruguay *Email: lbergamino@fcien.edu.uy ABSTRACT: We examined the assimilation of terrestrial organic matter (TOM) by the ovoviviparous isopod Excirolana armata inhabiting an exposed sandy beach of Uruguay. The source of this terrestrial input was an artificial freshwater discharge (the Andreoni Canal). We analyzed carbon (δ13C) and nitrogen (δ15N) isotope ratios in the TOM, in seawater particulate organic matter (POM) and in E. armata at 3 beach sites: Andreoni, at the canal mouth, Coronilla, at 1 km from the mouth and Barra, at 13 km from the mouth. Our analysis revealed clear effects of the canal discharge on the beach ecosystem. TOM was observed in the beach-face detrital mixture only at Andreoni; it also showed the lowest isotopic values there. POM δ13C values were also lowest near the canal mouth (increasing with distance from the mouth), indicating the dominance of terrestrial material in the carbon pools of sites closest to the freshwater discharge (viz. Andreoni and Coronilla). The same trend was seen in E. armata. Mixing-model (IsoSource) results for E. armata at Andreoni and Coronilla suggested that TOM was the main contributor to diet at these sites, while POM was the main contributor at Barra. We concluded that E. armata is a useful indicator of TOM assimilation in sandy-beach ecosystems. Our results point up the need, when studying sandy beach food webs, to consider potential modifications by terrestrial allochthonous inputs. KEY WORDS: Trophic subsidy · Excirolana armata · Freshwater discharge · Sandy beaches · Stable isotopes · Uruguay Full text in pdf format PreviousNextCite this article as: Bergamino L, Lercari D, Defeo O (2012) Terrestrial trophic subsidy in sandy beaches: evidence from stable isotope analysis in organic matter sources and isopod Excirolana armata. Aquat Biol 14:129-134. https://doi.org/10.3354/ab00392 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AB Vol. 14, No. 2. Online publication date: January 04, 2012 Print ISSN: 1864-7782; Online ISSN: 1864-7790 Copyright © 2012 Inter-Research.

Summer autotrophy and winter heterotrophy in the temperate symbiotic coral Cladocora caespitosa

Carbon and nitrogen isotope ratios (δ13C and δ15N) were determined in the zooxanthellae, host tissue, and whole symbiotic association of the symbiotic temperate coral Cladocora caespitosa, as well as in the different components of the coral's potential food sources (plankton, particulate organic matter in seawater and in the sediment). Data were collected both in winter and summer at three different locations, to assess the extent of auto‐ and heterotrophy in this species and get a better understanding of the functioning of temperate symbioses. There was a marked seasonal difference in the signature of the zooxanthellae and host tissue, highlighting two clear feeding patterns. In summer, δ13C signatures of the coral host and the zooxanthellae were similar (‐17‰) and very different from the signature of the food sources (from ‐21‰ to ‐25‰), suggesting that corals were relying on autotrophy for the acquisition of carbon. δ15N values also suggested that nitrogen was not acquired through feeding. Conversely, in winter, the δ13C signature of the host decreased by ca. ‐23‰ to ‐28‰, and was more comparable to the signature of the external food sources (between ‐24‰ and ‐25‰), suggesting a substantial reliance of C. caespitosa on external food sources during this season. There was also a 3‰ enrichment between the δ15N signatures of the food (4‐5‰) and the signature of the symbiotic association (7‐8‰), suggesting that nitrogen was also acquired through feeding. Overall, these results give evidence that C. caespitosa and temperate corals in general derive a large fraction of their energy from heterotrophic feeding in winter.

Coral mucus stable isotope composition and labeling: experimental evidence for mucus uptake by epizoic acoelomorph worms

Mucus released by scleractinian corals can act as an important energy and nutrient carrier in coral reef ecosystems, and a distinct isotopic signature would allow following the fate of this material. This study investigates the natural C and N stable isotopic signatures of mucus released by four scleractinian coral genera (Acropora, Fungia, Pocillopora and Stylophora) in comparison with those of suspended particulate organic matter (POM) in seawater of a Northern Red Sea fringing coral reef near Aqaba, Jordan. The natural δ13C and δ15N signatures of coral mucus differed significantly from seawater POM for the majority of seasonal comparisons, but were inappropriate for explicit tracing of mucus in the coral reef food web. Thus, a labeling technique using stable isotope tracers (13C and 15N) was developed that produced δ13C values of up to 122 ± 5‰ (mean ± SE) and δ15N of up to 2,100 ± 151‰ in mucus exuded by Fungia corals. 13C and 15N-enriched compounds were rapidly (within 3 h) and light-dependently transferred from the endosymbiotic zooxanthellae to the mucus-producing coral host. The traceability of 15N-labeled mucus was examined by evaluating its uptake and potential utilization by epizoic acoelomorph Waminoa worms naturally occurring on a range of scleractinian coral taxa. This tracer experiment resulted in uptake of coral mucus by the coral-associated acoelomorphs and further demonstrated the possibility to trace stable isotope-labeled coral mucus by revealing a new trophic pathway in coral reef ecosystems.

Inferring Black Carbon Concentrations in Particulate Organic Matter by Observing Pyrene Fluorescence Losses

Black carbon (BC), the soot and char formed during incomplete combustion of fossil and biomass fuels, is ubiquitous, participates in diverse environmental processes, and has adverse effects on human health. However, uncertainty persists regarding how accurately the present measurement methods quantify total BC or even defined subportions of the BC continuum. Hence, we sought to improve this situation by developing a new, low-sample manipulation methodology that does not require any oxidative or pyrolytic treatments but rather differentiates BC from other non-BC organic carbon (OC) using its sorbent properties. The procedure, referred to as the pyrene fluorescence loss (PFL) method, infers BC concentrations in particulate organic matter (POM) by observing the decrease in fluorescence from pyrene spiked into aqueous POM suspensions. The method was first tested using diverse materials previously utilized in an international BC method intercomparison study, and then its effectiveness (e.g., sensitivity and geochemical reasonableness) was tested by applying itto sediment and seawater POM samples collected from a coastal area downwind of important BC sources. Parallel evaluation of BC, using the PFL method and CTO-375 procedure, suggested we can characterize the predominant BC in a given sample as (i) thermally recalcitrant and highly sorptive per mass (e.g., soot), (ii) thermally labile and highly sorptive per mass (e.g., char), or (iii) thermally recalcitrant but not highly sorptive (e.g., lignite coal).

Influence of the Danube River inputs on C and N stable isotope ratios of the Romanian coastal waters and sediment (Black Sea)

The main aim of this study was to estimate the influence of the seasonal variations of the Danube River particulate organic matter (POM) inputs on the Black Sea surface seawater POM and upper layer of sediments along the Romanian coast. Ratios of carbon ( 13C/ 12C) and nitrogen ( 15N/ 14N) stable isotopes allowed differentiating river and marine organic matter sources. Danube River POM presented significantly lower average values of δ 13C (−27.52 ± 0.88‰) and δ 15N (4.88 ± 1.45‰) than seawater POM ( δ 13C = −24.70 ± 2.37‰ and δ 15N = 6.75 ± 1.96‰), whereas surface sediment presented average values similar to seawater POM ( δ 13C = −24.02 ± 2.39‰ and δ 15N = 7.29 ± 2.16‰). Stable isotope values showed that the Danube River influence on marine ecosystems decreased from the North to the South of the Romanian coast. Strong seasonal variations of C and N isotopic signatures were observed in all compartments studied with generally higher values in spring when the river was flooding.

Steroid alcohols and ketones in coastal waters of the western Mediterranean: Sources and seasonal variability

A total of 36 sterols (stenols and stanols) and 17 sterones (stenones and stanones) were identified in the particulate organic matter (POM) of surface seawater from the western Mediterranean in the vicinity of the Ebro river mouth. Concentrations of particulate sterols ranged from 0.6 to 4.8 μg l −1 in the delta bays and from 0.07 to 1.1 μg l −1 in the open sea transects. Sterones were present at one order of magnitude lower. Both the concentrations and the compositions of steroidal components were seasonally dependent, reflecting changes in the phytoplanktonic population, in the sense that diatom biomarkers ( Δ 5, Δ 5,22 and Δ 5,24(28)-stenols, and Δ 4-stenones) were the major components during marine fertile periods (spring and fall), whereas dinoflagellate markers (4 α-methylstanols and 4 α-methylstanones) predominated during the lowest productivity periods (summer and winter). Based on spectral data 4 α-methylcholest-7-en-3 β-ol, 4 α,23,24-trimethylcholest-7-en-3 β-ol, 4 α-methyl-5 β(H)-cholestan-3 β-ol and 24-methylcholesta-4,24 (28)-dien-3-one were identified for the first time in seawater particles. Some of these are proposed as biomarkers of the dinoflagellate contribution to POM in seawater. In addition, the occurrence of red algae in the river bays in spring is suggested by steroidal biomarkers (i.e. cholesta-5,24(25)-dien-3β-ol). Fecal pollution was detected, according to the 5 β-steroids distribution, near the Ebro river mouth and Tarragona.

Sterenes in suspended particulate matter in the eastern tropical North Pacific

Particulate matter in the oceans is operationally partitioned into two pools. Large (≳ 32 µm) particles, such as zooplankton faecal pellets and marine snow, sink rapidly and dominate the vertical flux of organic matter in the oceans1–4. These relatively rare particles, usually collected in sediment traps, sink at rates of tens to hundreds of metres per day5–8 leading to a significant flux of labile particulate organic matter from sites of production in the euphotic and mesopelagic zones to the deep ocean9–14. Finer (≲ 2 µm) suspended material, on the other hand, dominates the standing stock of particulate matter1. Sinking rates of only a few metres per day for small particles result in long residence times in the water column during which major transformations of the suspended organic matter may occur. Source and transformation processes involving particulate organic matter in seawater and Recent sediments may be traced by studying various classes of specific organic marker compounds, including the steroids9,11,15–18. We report here the apparent production of sterenes (steroidal alkenes) on suspended particulate matter within the oxygen minimum zone in the equatorial Pacific Ocean off central Mexico; this provides further evidence of the importance of water column processes on early stages of the transformation of biogenic sterols to the steranes present in mature sediments.

Distribution of heterotrophic bacteria in relation to the concentration of particulate organic matter in seawater

The relationship between the number of bacteria and the concentration of particulate organic carbon (POC) in seawater was investigated. In coastal seawater in summer, the POC concentration showed better correlation to the density of bacteria obtained by the viable plate count method (viable count, V.C.) than by the total direct count method (total count, T.C.). The number of attached bacteria (A) showed significant fluctuation, both laterally on a geographical scale and vertically in the water column; on the other hand, the number of free-living bacteria (F) was relatively constant. The POC concentration had a much higher correlation with A (r = 0.8795) than with T.C. (r = 0.7339), and had a low correlation with F (r = 0.6935). Moreover, a very good correlation was observed between the density of bacteria obtained by V.C. and A (r = 0.9153). These results indicate that when the concentration of particulate organic matter (POM) increases, some free-living bacteria become attached to POM, and grow on the surface of POM. These communities of attached bacteria have the ability to make colonies on plate media and can be counted as the "viable plate count."

Chemical and GC-MS characterization of marine particulate lipids

The lipid fraction of particulate organic matter in seawater was analyzed by gravimetry, liquid chromatography, gas chromatography (GS), and gas chromatography—mass spectrometry (GS—MS). Gravimetric concentrations in the Gulf of Mexico were in the range of 12–70 μg 1 −1 for near-surface samples and 9–52 μg 1 −1 for near-bottom samples. The lipids accounted for ∼20% of the particulate organic carbon. Particulate lipids were found to be a much more complex mixture of organic compounds than the dissolved lipids and their composition was much more variable. The majority of the extracted weight was recovered in the polar liquid chromatography fraction (49–85%). The major components of the analyzable particulate lipids were similar to those of the dissolved lipids, namely, n-alkanes, pristane, phytane, and methyl, ethyl and propyl fatty acid esters. Often olefins, alkylated benzenes, quinones, and the unresolved GC area contribute a substantial part to the total particulate lipids. Minor components included ketones, phenols, indanes, acids, benzoates, aromatics and possibly derivatives of inositol, dioxane, and pyran. The low concentrations observed confirm that the area is relatively pristine though some evidence for chronic low-level oil pollution was present. Seasonal, diurnal, vertical and areal variations were observed in the particulate lipids. Lipid concentrations not only decreased with depth but they were also a decreased percentage of the organic carbon present. This may indicate the loss of labile carbon with depth due to reworking in the euphotic zone. Anoxic conditions appeared to promote the preservation of lipid materials in the particulate phase, n-Alkanes and fatty acid esters were common to both the particulate and dissolved phases and had similar distributions.

Land sources of marine organic matter

Organic matter in seawater is ultimately derived from various species of marine plants and river run-off and airborne materials of terrestrial origin. Direct addition of organic matter, especially due to oil spills, is also an important source for organic matter in seawater. Recent advances in the studies of the chemistry and biochemistry of particulate organic matter in seawater clearly indicate that most of the organic materials produced by the photosynthetic reaction of phytoplankton is decayed before the particulate matter has reached the ocean floor. This fact suggests that the processes of primary production may not contribute much to the input of organic matter to the deep ocean. The average concentration of organic carbon in river water is estimated to be 10 mg C/l. Thus, annual input of organic matter to the ocean can be calculated as 3.0 · 10 14g C. However, two opposite arguments on this point have been reported. Several workers have stated that the contribution of river-dissolved organic matter (i.e., humic substances) to the ocean must be ignored because of rapid precipitation of the organic matter during the mixing processes of river water with seawater, while Sholkovitz (1976) stated that only 3–10% of organic matter from river water is precipitated in contact with seawater. Thus, more studies on the mechanism of the flocculation in estuaries are needed. The organic matter carried by winds may be somewhat more important to the organic matter in the ocean than is that of the rivers. The isolation, identification and elucidation of the organic compounds from airborne particles of urban areas and from exhaust gases derived from internal combustion engines have been developed extensively during the last decade. Very limited information as to the contribution of these organic compounds to the ocean is available at the present time. Organic materials from land sources must be transported to the ocean mainly by trade winds, since pesticides and PCBs have been determined in marine aerosols collected at Barbados. Quantitative estimation of the contribution of airborne particles to the ocean is an important problem to solve in the future in view of the mass-balance of the organic matter in the ocean.

Composition of the inorganic fraction of the particulate organic matter in seawater

Na, K, Mg, Ca, Fe, and Mn have been measured in both naturally occurring particulate matter and artificially created aggregates taken from water from the Nova Scotian coastal region and from the North Atlantic Ocean. The order of concentration of these elements is the same in both the aggregates and the natural particulate matter as it is in seawater. There is an inverse relationship between depth of the water and the amount of inorganic matter in artificially created aggregates, while a direct relationship is found with the naturally occurring particles. This direct relationship may reflect the utilization of organic material in the surface waters. Iron and manganese are enriched in both kinds of particles.

Microbial Biomass on Particulate Organic Matter in Seawater of the Euphotic Zone

Microbial biomass on suspended organic matter in seawater of the euphotic zone of Saanich Inlet was investigated. The viable microorganisms were measured by the glucose-uptake method. Microbial carbon on particulate organic matter in seawater was determined to be, on the average, 9.9 μg of C/liter, and there was a regression relationship as y = 0.0062 x − 1.79 with an unbiased variance V yx 1/2 = 0.38, where x = particulate organic carbon in seawater (micrograms of C/liter) and y = logarithm of microbial carbon (micrograms of C/liter).

Microbial Biomass on Particulate Organic Matter in Seawater of the Euphotic Zone

Microbial biomass on suspended organic matter in seawater of the euphotic zone of Saanich Inlet was investigated. The viable microorganisms were measured by the glucose-uptake method. Microbial carbon on particulate organic matter in seawater was determined to be, on the average, 9.9 mug of C/liter, and there was a regression relationship as y = 0.0062 x - 1.79 with an unbiased variance V(yx) = 0.38, where x = particulate organic carbon in seawater (micrograms of C/liter) and y = logarithm of microbial carbon (micrograms of C/liter).

ORGANIC AGGREGATES IN SEAWATER AND THE DYNAMICS OF THEIR FORMATION AND UTILIZATION

Much of the nonliving particulate organic matter in seawater consists of delicate, plate‐like aggregates ranging in size from about 5 µ to several mm in diameter. The aggregates are amorphous matrices containing both organic and inorganic materials, with inclusions of bacteria and phytoplankton. Descriptive information herein deals primarily with a two‐year series of observations in Long Island Sound. A consistent bimodal seasonal cycle has been found, with peaks in winter and early summer. These aggregates appear to be formed mainly by adsorption of dissolved organic matter on bubbles and other naturally occurring surfaces in the sea, a process readily duplicated under experimental conditions. Naturally occurring aggregates provide a substrate for bacterial growth and probably food for animals. They are present during certain seasons when phytoplankton is scarce and probably serve an important function as supplementary food for zooplankton under such circumstances. The presence of aggregates is an oceanic as well as a coastal phenomenon and is believed to have general ecological significance. A concept is developed that the reversible reaction between dissolved and particulate matter tends to stabilize the marine association, and there are suggestions of community adaptation in the development of this system.