Total Particulate Organic Matter Research Articles

The roles of grass leaf litter in streams draining tussock grassland in New Zealand: retention, food supply and substrate stabilization

SUMMARY1. We investigated the roles of grass litter in streams that drain upland New Zealand tussock grassland, paying particular attention to the ways in which grass leaves differed in their characteristics from much more intensively studied tree leaves.2. The instantaneous retention rates of tussock grass leaves (Chionochloa rigida) on the bed of a second‐order stream (0.157–0.515 m−1) were significantly higher than those of the elliptical leaves of lemonwood trees (Pittosporum eugenioides; 0.068–0.180 m−1).3. Instantaneous retention rates of grass leaves in two third‐order streams were very low. At high discharge, leaf retention rate was greater in Timber Creek (0.0040 m−1), a braided, gravel bed stream, than in the adjacent Kye Burn (0.0010m−1), with its well‐defined channel and large, stable substrate particles. At baseflow, retention rates were similar in the two streams (0.0053–0.0064 m−1 for Timber Creek; 0.0047–0.0058m−1 for Kye Burn). Nevertheless, total coarse particulate organic matter (mainly derived from tussock litter) was present at lower densities in Timber Creek than Kye Bum, reflecting the instability of the bed of the former and its tendency to spread over a wide area at high discharge.4. The results of a colonization tray experiment, in which substrate was mixed with tussock leaves, nylon ribbon or nothing, indicate that tussock leaves do not play an important role as microhabitat or food in the two third‐order streams. This may reflect the poor food quality of grass litter, and/or the relatively low availability and predictability of its supply.5. An in situ experiment revealed that tussock leaves play a role, analogous to that reported for certain seagrasses, in stabilizing substrate and reducing sediment transport, apparently by reducing bed roughness and therefore the force of friction on the bed.

Seasonal Variation of the Stable Isotopic Compositions of Coastal Marine Plankton from Woods Hole, Massachusetts and Georges Bank

A study of the isotopic composition of plankton from Woods Hole Harbor was conducted to investigate seasonal variation in carbon and nitrogen stable isotopes in a shallow coastal environment. Stable isotopic ratios of carbon and nitrogen both showed temporal variation on the scale of weeks to months, with heaviest (most positive) values in summer to fall for both isotopes. Particulate organic matter (POM) δ13C values were highest (−19‰ to −21‰) in August to November and lower (−21‰ to −25‰) at other times of the year, while δ13N-POM values were highest (9.5‰ to 12‰) in March to September and lower (7.5‰ to 9.5‰) at other times of the year. Stable isotopic values were significantly correlated with temperature, DI13C, and C∶N ratios, but not with [DIC], [POC], [PN], [chlorophyll], or the taxonomic composition of the phytoplankton. There was no direct evidence of allochthonous inputs of carbon and nitrogen to the system. Woods Hole δ13C values were virtually identical to Georges Bank plankton values; similar POC: Chlorophyll and C∶N ratios in the two systems further suggest that Woods Hole Harbor is principally a marine system. The high δ13C values of net plankton (>20 μm) during summer and early fall are consistent with a smaller degree of photosynthetic isotopic fractionation at that time, related to temperature and/or [CO2(aq)]. This pattern was not seen, however, in total POM. Plankton δ13N values were higher in Woods Hole Harbor than on Georges Bank, especially during warmer periods, possibly due to high rates of nitrification and organic matter recycling in Woods Hole waters. Relatively wide ranges of stable isotopic values from both Woods Hole Harbor and Georges Bank suggest that seasonality should be considered when attempting to establish endmember C and N isotopic values for temperate marine plankton. Preliminary results from size-fractionated samples suggest that cyanobacteria may fractionate carbon isotopes to a greater degree than net phytoplankton.

Storage and decomposition of particulate organic matter along the longitudinal gradient of an agriculturally-impacted stream

An agriculturally-impacted stream in northern Idaho was examined over a two-year period to determine seasonal and longitudinal patterns of the storage and decomposition of particulate organic matter. Biomass of benthic organic matter (BOM) was considerably less than values reported in the literature for comparable, undisturbed streams. Coarse, fine, and total benthic particulate organic matter were not correlated with parameters pertaining to stream size (e.g., stream order), but were correlated with sample site and amount of litterfall. The association of BOM with site and litterfall suggests that storage of particulate organic matter is a function of local characteristics rather than stream size. Low biomass of stored organic matter is a response to the low input of terrestrially-derived organic matter resulting from removal of climax vegetation.

Variability of biochemical composition and size distributions of seston in the euphotic zone of the Bay of Biscay: implications for microplankton trophic structure

Particle-size distributions and several biochemical components of seston were studied from October 1986 to December 1987 in surface waters of the Bay of Biscay. Variance partitioning of hydrographic and seston parameters indicates that, although seasonal variability related to the thermal cycle was important, most of the differences in seston concentration were caused by spatial components of variance. Changes in the vertical structure of the water column appeared to be the principal source of variability. Phytoplankton blooms in spring and fall and the effects of the coastal upwelling and the thermocline during summer were traced using seston concentration and biochemical composition. The different seston measurements were scaled according to their correlations with total concentration and particle size. Photosynthetic pigment biomass was related to both large and small partieles. However, concentrations of particulate proteins, lipids and carbohydrates were more related to small particles. Although not specifically analysed, low concentrations of inorganic particles and detritus can be expected in the study area, thus most of the particulate organic matter was associated with small, non-pigmented organisms, particularly in surface waters during the period of thermal stratification. The variability in concentrations of total seston and particulate organic matter was mainly due to variations in particulate proteins, lipids and carbohydrates; pigment concentrations were of secondary importance. Expressed as the ratio chlorophyll a: particulate protein-nitrogen, phytoplankton constituted an important fraction of the microplankton biomass only during spring blooms, when it averaged 75% of the particulate protein-nitrogen. In constrast, <30% of protein-nitrogen was related to chlorophyll a during the summer. These results suggest that an oligotrophic structure based on the “microbial-loop” prevails in microplankton assemblages of surface waters for most of the year.

Effects of Disturbance on Benthic Functional Structure and Production in Mountain Streams

To assess the role of macrofauna consumers in organic matter dynamics of headwater streams, we applied seasonal insecticide treatments to a southern Appalachian Mountain stream and compared benthic community structure between this and two other streams. Production was estimated in the two major habitats: mixed cobble-gravel-sand substrate and bedrock outcrop. Using the proportional availability of the habitats in each stream, production over the entire stream was measured. Annual habitat-weighted production in the untreated streams during the two study years ranged from 8.9 to 14.0 g AFDM m^-2 yr^-1, 81 to 86% of which was attributed to insects. Habitat-weighted production was distributed rather evenly among the collector-gatherer (32-41%), shredder (23-31%), and predator (28-33%) functional groups. Collector-filterer and scraper groups accounted for less than 9% of total habitat-weighted production in all three streams. Insecticide applications resulted in dramatic changes in the macrofaunal community. Annual habitat-weighted production (4.4 g m^-2 yr^-1) in the treated stream decreased by 62% from Yr 1 to Yr 2, with insects contributing only 45% to total production. Oligochaetes, several Diptera, dragonflies, and copepods composed most of the production during treatment. Although habitat-weighted production of all functional groups was lower in the treatment year than in the pre-treatment year, collector-gatherer production decreased the least (21% reduction) and dominated overall production during treatment. Production of the other functional groups decreased by 71-94% between the two years. The changes in macrofaunal community structure and production observed in the insecticide treated stream were much greater than between-year changes in the reference stream, despite the occurrence of a record drought in Yr 2. The effect of the two different disturbances on overall production differed not only in magnitude but also in direction, with production in the reference stream increasing (12% over Yr 1) during the drought year. Resource ingestion was estimated using values of functional group production. Estimates of ingestion suggested that the major functional groups were ingesting a fairly large portion of available resources in the untreated streams. Collector-gatherers consumed 34-64% of total annual habitat-weighted fine particulate organic matter. Shredders consumed an estimated 28-47% of average annual standing crop of leaves, and predators ingested 67-79% of total macrofaunal production. Insecticide treatments resulted in much lower levels of resource ingestion: 26%, 4%, and 50% for collector-gatherers, shredders, and predators, respectively. Our results show the importance of using estimates of production when assessing disturbance effects on macrofaunal communities, since abundances greatly underestimated the impact of insecticide treatments. Biomass estimates, though providing better measures of disturbance than abundances, tended to overestimate overall macrofaunal losses because of the disproportionate influence of large, slow growing taxa such as crayfish.

Chlorophyll concentrations and suspended particulate loads in St Lucia, a turbid estuary on the east coast of South Africa

Concentrations of chlorophyll a and suspended particulate concentrations were measured during three lake-wide surveys of St Lucia, a shallow, turbid estuary on the east coast of South Africa. There was no salinity gradient in the system during any of the surveys, but between the surveys there were considerable salinity differences. Summer turbidities were higher than those of winter and spring, and turbidity along the eastern edge of the system was lower than elsewhere. Chlorophyll a was present over a wide range of salinities and turbidities and was generally highest in summer. However, there was no relationship between salinity and concentrations of chlorophyll a, and the concentrations were not significantly higher along the less turbid eastern shore. Concentrations of total paniculate matter (TPM) and particulate organic matter (POM) in the < 100 μm fraction were significantly correlated with turbidity throughout the year, but chlorophyll a and POM (< 100 μm) were significantly correlated only in summer. Concentrations of TPM in the > 100 μm fraction were two orders of magnitude lower than those in the < 100 μm fraction, but the organic content of the former fraction was very much higher. There was no relationship between turbidity and TPM (> 100 μm), nor between chlorophyll a and POM (> 100 μm) concentrations. Under conditions of high TPM load and in the salinity range 2–25 × 10−3, phytoplankton would probably still occur in St Lucia. Estimates of phytoplankton production ranged between 218 and 252 mg C·m−2·day−1. A comparison of estimates of the standing stocks of carbon from phytoplankton and suspended POM < 100 μm indicated that carbon input from sources other than phytoplankton may be important.

Estimating Intermittent Runoff Concentrations of Organic Matter and the Allochthonous Organic Loading of New Mexico Reservoirs

ABSTRACT Variations in the concentrations of total and particulate organic matter were estimated from 1979 through 1988 in natural and simulated runoff events to improve estimates of reservoir gross organic loading from intermittent flows. Total organic matter concentrations in natural runoff from pinyon-juniper watersheds and particulate organic matter concentrations in runoff from creosote bush watersheds increased as a natural logarithmic function of discharge. Total organic matter and particulate organic matter discharge-weighted concentrations in natural runoff events were related to measurements of instantaneous discharge and total organic matter and particulate organic matter concentrations, and to estimates of the maximum discharge of total organic matter and particulate organic matter concentrations that occurred in the event. In rainfall simulations conducted in watersheds of creosote bush, desert grass, pinyon-juniper, ponderosa pine, and spruce meadow, only particulate organic matter concentra...

Particulate Organic Matter Export from Three Headwater Streams: Discrete versus Continuous Measurements

Particulate organic matter (POM) export from three small headwater streams of the southern Appalachian Mountains was estimated using continuous and discrete (grab) measurement methods for 2 yr. Total annual POM export estimated from continuous measurements was always greater (28–68 kg ash-free dry mass (AFDM)) than estimates (8–44 kg AFDM) made from discrete measurements (i.e. POM concentration × total discharge). Continuous export samples were collected using a weir and gaging flume connected to a Coshocton proportional sampler designed to deliver 0.6% of discharge into a series of three settling barrels. The settling barrels removed a consistent proportion of POM (85–87%). The proportion of stream flow sampled by the Coshocton samplers was constant for each of the samplers (range 0.53–0.6%). The constant extraction efficiencies and proportional sampling of discharge allowed for the calculation of total export independent of discharge measurements (i.e. total export = amount in barrels ÷ extraction efficiency ÷ Coshocton percentage). The inability of the discrete method to adequately sample storm and bedload transport accounts for the underestimates of total annual export. This underestimation has important implications for studies which use discrete measurements to estimate POM export.

Dynamique du phytoplancton et matière organique particulaire dans la zone euphotique de l'Atlantique Equatorial

At two fixed stations in the Equatorial Atlantic Ocean (0°–4° W), the physical, chemical and biological properties of the euphotic layer were determined for 14 d (Station A: 5–18 February, 1979) and 13 d (Station B: 20 October–7 November, 1979), respectively. The stability of the water column allowed comparison of 3 different “systems”: (i) a well-illuminated and nitrate-depleted mixed layer; (ii) a chlorophyll maximum layer (chl amax) in the thermocline which is poorly illuminated (6.3% of surface irradiance); (iii) a well-illuminated but nitrate-rich (>0.9 μg-at l-1) mixed layer. In each layer the particulate organic carbon (COP), nitrogen (NOP) and phosphorus (POP) contents were measured and compared with the phytoplankton biomass. In the chlorophyll maximum layer, the phytoplankton biomass contributed significantly to the total particulate organic matter (between 55 and 75%). In the nitrate-depleted mixed layer, the results varied according to whether the regression technique [COP=f(chl a)] was used, or the chl a synthesis during the incubation of the samples. With the former technique, the phytoplankton carbon (Cp) content appeared minimal, because the y intercept, computed using all the data of the water column, was probably overestimated for this layer. POP would be more associated with living protoplasm than with carbon and nitrogen in the three layers. In the chlorophyll a maximum layer it constitutes a valuable detritus-free biomass measurement, since 80% of the POP consist of phytoplankton phosphorus. The assimilation numbers (NA=μg C μg chl a-1 h-1) were high in all three layers, but the highest values were recorded in the nitrate-depleted mixed layer (NA=15 μg C μg chl a-1 h-1). In the chlorophyll maximum layer, light would be a limiting factor during incubation: between 1025 and 8.1024 quanta m-2 d-1 NA and light are positively correlated independant of nitrate concentration. The growth rates of phytoplankton (μ) were estimated and compared to the maximum expected growth rate. Our main conclusion was that despite very low biomass and nutrient content, the mixed layer was in a highly dynamic state, as evidenced by high rates of phytoplankton growth and short nutrient turnover times (1 d or less for PO-P4 in the mixed layer versus 3 d in the thermocline). The presence of nitrate in the water column allows the development of a higher phytoplankton biomass but does not increase growth rate.

Ambient levels of particulate organic matter in New York City in winter and summer

Samples of suspended particulate matter were collected during two summer and two winter sampling campaigns. Non-polar, moderately polar and polar fractions of particulate organic matter (POM) were separated by 8h sequential Soxhlet extractions with cyclobexane, dichloromethane and acetone, respectively. Atmospheric concentrations of total POM averaged 13.0 μgm −3 for the two summer periods and 16.0 μgm −3 for the two winter periods. Extractable organic matter in respirable (D 50≤3.5 μm aerodynamic diameter) suspended particulate matter was 81% of the TSP organics during January–February 1978, but only 54% of TSP organics in August 1978. Evaluation of dispersion normalized aerosol concentrations of POM indicated that space heating contributed approximately 75% of the total POM in New York City in February 1977 and 51% in January–February 1978. The strong association of POM with the “oil-burning” factor obtained by factor analysis performed on the data was also indicative of a substantial contribution from this source. Use of high-sulfur (1.5–15 %) fuel oil in New York City during the 1976–1977 fuel crisis appears to have had a striking and significant impact on both total emissions and ambient concentrations of POM during February 1977. The cumulative evidence indicates oil-burning for space heating is currently the most significant source of POM although it contributes only 10–20% of the TSP. The atmospheric concentrations of POM and TSP determined in this study were compared to those measured at the same site in 1968 and 1969. Although wintertime TSP levels have declined to almost one-half of the levels of 1968 and 1969, wintertime concentrations of airborne POM do not appear to have declined. The summertime concentrations of POM in 1977 and 1978 were about 40% higher than those determined for similar periods in 1968 and 1969.

Vertical transport of particulate organic matter in the deep Bering Sea and gulf of Alaska

Sediment trap arrays were deployed at two deep ocean stations, one in the Bering Sea and the other in the Gulf of Alaska, in the summer of 1975. The sediment trap was constructed of a pair of polyethylene cylinders (0.185 m2 opening) with funnel-shaped bases. The trap is equipped with a lid which is closed before recovery by a tripping messenger system triggered by an electric time release. 37–68% of the total organic carbon fluxes (37–38% in the Bering Sea; 48–68% in the Gulf of Alaska) were represented by large particles (67µm<) such as fecal matter and fecal pellets which contributed minor fractions to the total particulate organic matter concentration in sea water. The total fluxes were 11.1 and 14.2 mg C m−2d−1 at 1,510 and 2,610 m respectively at the station (3,800 m) in the Bering Sea, and were 7.60, 4.66 and 3.27 mg C m−2d−1 at 900, 1,500 and 1,875 m respectively at the station (4,150 m) in the Gulf of Alaska. The former values are several times greater than the latter, suggesting that there is a regional variation in the vertical carbon flux in deep layers. The fluxes were approximately equivalent to 1 to 3% of primary productivity in the overlying surface layers. These observations suggest that deep-water ecosystems may be influenced by relatively rapid sinking of large particles such as fecal matter and fecal pellets from near surface production.

A statistical method to estimate the biochemical composition of phytoplankton in the Southern Bight of the North Sea

The knowledge of changes in the biochemical composition of phytoplankton and its degraded products is regarded as important for the understanding of an eco-system because it influences the heterotrophic activities of the seawater column and/or sediments. The linear regressions method of some specific metabolite (protein, carbohydrate, lipid) on chlorophyll a is considered as the better method to estimate the biochemical composition of natural phytoplankton in the coastal area of the Southern Bight of the North Sea. The validity of this statistical method depends on a correct assemblage of the results in time and space, and requires a good knowledge of the growth conditions of the phytoplankton cells. This essential condition is however difficult to realize for post-bloom periods where the growth conditions are more heterogeneous. The linear regressions lead on the one hand to the quantification of two components of the total particulate organic matter (phytoplankton and bacteria/detritus) and on the other hand to their biochemical characterization. The comparison of the biochemical composition of the two components shows that bacteria/detritus component has an effective nutritive value when phytoplankton is less abundant. The study of the influence of changes in the environmental conditions (light intensity and nitrogen availability), on the biochemical composition of the phytoplankton shows a similar protein content of about 50% when nitrogen is not limiting. On the other hand, a change in the light intensity does not change the biochemical composition of natural phytoplankton but increases the cellular chlorophyll content when nitrogen is sufficient to ensure a good phytoplanktonic growth.

The chemical composition of macroscopic aggregates in two neretic seas1

Chemical analysis of macroscopic aggregates and whole water samples show that 26–34% of total particulate organic carbon, nitrogen, protein, carbohydrate, lipid, and particulate dry weight in surface waters of the Santa Barbara Channel and 4–8% in the Gulf of California exist as particles of marine snow 3 mm or longer in longest dimension. Twenty percent of these aggregates in the Gulf of California and 5% in the Santa Barbara Channel were of recognizable zooplankton origin. Macroscopic aggregates from the Gulf of California had significantly lower carbon, nitrogen, and protein content and significantly higher ash content than the total particulate matter. Aggregates in both locations had significantly higher carbon:nitrogen ratios than the total particulate organic matter. Calculated sinking rates of macroscopic aggregates indicate that marine snow serves as a major source of vertical flux to the benthos. As enrichment sites for nutritionally valuable substances, macroscopic aggregates are rich food sources and significantly alter the microscale distribution and composition of particulate organic matter in neritic waters of the pelagic zone.

The distribution of dissolved organic carbon in the Western Indian Ocean

The concentration of dissolved organic carbon between 0 and 2000 m depth was measured along a section from 20°S to 20°N in the Western Indian Ocean. No apparent correlation existed between primary production and the level of dissolved carbon in the euphotic zone. Deep water masses were characterized by temperature-salinity relationships and by the concentration of carbon. Calculations for the mixing of these water masses of differing origin on the basis of salinity, corresponded with similar calculations based on carbon. Assuming 90% conversion of total particulate organic matter to carbon dioxide by grazing organisms a minimum of 260 years is required to produce the amount of organic carbon present in the Arabian Sea. The conclusion is reached that carbon in solution and in particulate form in the ocean is extremely stable and subject to limited change by biological action.