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1.
Cultures of six marine phytoplankton were grown at ammonium concentrations ranging up to 200 μg-atom NH4---N litre−1. Only the growth of dinoflagellates, Gymnodinium splendens and Gonyaulax polyedra was inhibited at the two highest concentrations used. In 3-h photosynthetic 14CO2 uptake experiments, only Gymnodinium was inhibited at concentrations of NH4---N greater than 100 μg-atom litre−1. We conclude that the increased ammonium concentrations found near Southern California sewage outfalls would not be inhibiting to phytoplankton in the vicinity of such outfalls.  相似文献   

2.
Neanthes arenaceodentata were exposed to 292, 146, 92 and 56 μg litre−1 Cu (measured) and control seawater after a 27-day pre-exposure to a sublethal concentration of Cu (10, 16 and 28 μg litre−1 and control) to determine if the worms increased their tolerance to Cu after the pre-treatment. The worms pre-exposed to 28 μg litre−1 Cu were significantly more resistant to Cu toxicity than control and 10 and 16 μg litre−1 Cu pre-exposed worms. For example, the time to 50 % mortality at 92 μg litre−1 Cu was 18 and 11 days for worms pre-exposed to 28 μg litre−1 Cu and control conditions, respectively. The net rate of Cu uptake during the toxicity test was lower for worms pre-exposed to 28 μg litre−1 Cu than for the control and 10 and 16 μg litre−1 Cu pre-exposed worms. For example, the net rate of Cu uptake at 292 μg litre−1 Cu by worms pre-exposed to 28 μg litre−1 Cu and control conditions was 42 and 102 μg g−1 day −1, respectively.  相似文献   

3.
The effect of dissolved petroleum hydrocarbons in the environment on phytoplankton biomass measured as chlorophyll a was studied near the oil tanker route in the southern Bay of Bengal. In the transect from 5° N, 77° E to 5° N, 87° E the concentrations of dissolved petroleum hydrocarbons were negatively correlated with phytoplankton biomass, whereas in the 0° N, 87° E to 1° N, 79° E transect they were positively correlated with phytoplankton biomass. The mean petroleum hydrocarbon concentrations in the two transects were 12·12 ± 4·67 μg litre−1 and 11·23 ± 4·5 μg litre−1, respectively.It is surmised that the effect of dissolved petroleum hydrocarbons on phytoplankton biomass varies depending on the nature rather than the quantity of petroleum hydrocarbons present. Culture studies with unialgal Nitzschia sp. in seawater collected from selected stations in the study area as well as in artificial seawater spiked with the water-soluble petroleum hydrocarbon fraction of light Arabian Crude support this.  相似文献   

4.
A worldwide literature survey of data on cadmium concentration in the soft tissue of the mussel, Mytilus spp., from 591 stations is presented. These stations are from 13 regions. Geometric means for the regions vary from 0·6 to 3·3 μg g−1 (dry weight) for the Barents Sea and the Northeastern Pacific coast, respectively.The averages of seven of these regions, for which reliable cadmium concentrations in seawater were available, were used to calculate a relationship between cadmium concentrations in seawater and mussel soft tissue. The relationship was highly significant: (Cd) mussel (μg g−1, dry weight) = 0·074 (Cd) water (ng litre−1) + 0·39 (P ≤ 0·0005).This model has been successfully applied in the context of the contamination of the Gironde estuary (France). It can also be used to define a water quality criterion for mussel maturing parks consistent with the quality criterion defined for shellfish for human consumption.  相似文献   

5.
Specific effects of tributyltin (TBT) on Crassostrea gigas—valve thickening, and Nucella lapillus—imposex, were measured on local populations, relatively clean unaffected species from England were transferred to the Netherlands and exposed during six weeks to ambient TBT concentrations. Near marinas 50% of the exposed species were sterile after six weeks. In general, no dissolved butyltins were detected in the Rhine and Scheldt estuaries. In 1988 TBT concentrations in marinas ranged from 120 to 4000 ng litre−1. In sediments (fraction <60 μm) and suspended particulate matter TBT concentrations reached up to 1200 ng g−1. TBT concentrations in mussel tissue ranged from <1 to 2300 ng g−1 based on a dry weight. In 1989 concentrations of dissolved TBT ranged from <0·1 to 7200 ng litre−1. In 1989 a seasonal study in the marina of Colijnsplaat showed that dissolved butyltins increased from April to the end of May due to the launching of freshly painted boats, and decreased afterwards.  相似文献   

6.
Primary production was measured during two Lagrangian experiments in the Iberian upwelling. The first experiment, in a body of upwelled water, measured day-to-day changes in phytoplankton activity as the water mass moved south along the shelf break. Nutrient concentrations decreased over a five day period, with concomitant increases in phytoplankton biomass. Initially the maximum phytoplankton biomass was in the upper 10m but after four days, a sub-surface chlorophyll maximum was present at 30m. Depth-integrated primary production at the beginning of the experiment was 70mmolC.m−2.d−1 (838mgC.m−2.d−1) and reached a maximum of 88mmolC.m−2.d−1 (1053mgC.m−2.d−1) on day 3. On day 1, the picoplankton fraction (<2μm) was slightly more productive than larger (>5μm) phytoplankton, but the increase in overall production during the drift experiment was by these larger cells. Nitrate was the dominant nitrogen source. As nutrient concentrations declined, ammonium became increasingly more important as a nitrogen source and the f-ratio decreased from 0.7 to 0.5. Picoplankton cells (<2μm) were responsible for most (65–80%) of the ammonium uptake. The C:N:P uptake ratios were very close to the Redfield ratio for the first four days but as nutrients became depleted high C:N uptake ratios (11 to 43) were measured. Over the period of the experiment, nitrate concentration within the upper 40m decreased by 47.91mmolN.m−2. In vitro estimates, based on 15N nitrate uptake, accounted for 56% of the decrease in nitrate concentration observed in the drifting water mass. Ammonium uptake over the same four day period was 16.28mmolN.m−2, giving a total nitrogen uptake of 43.18mmolN.m−2.In the second experiment, an offshore filament was the focus and a water mass was sampled as it moved offshore. Nutrient concentrations were very low (nitrate was <10nmol l−1 and ammonium was 20–40nmol l−1). Primary production rate varied between 36mmolC.m−2.d−1 (436mgC.m−2.d−1) and 21mmolC.m−2.d−1 (249mgC.m−2.d−1). Picophytoplankton was the most productive fraction and was responsible for a constant proportion (ca 0.65) of the total carbon fixation. Uptake rates of both nitrate and ammonium were between 10 and 20% of those measured in the upwelling region. Urea could be a very significant nitrogen source in these waters with much higher uptake rates than nitrate or ammonium; urea turnover times were ca. one day but the source of the urea remains unknown. Urea uptake had a profound effect on calculated f ratios. If only nitrate and ammonium uptake was considered, f ratios were calculated to be 0.42–0.46 but inclusion of urea uptake reduced the f ratio to <0.1. The primary production of this oligotrophic off-shore filament was driven by regenerated nitrogen.  相似文献   

7.
In September 1994 and 1995, scientists from the Australian Institute of Marine Science (AIMS) and the Australian Geological Survey Organization (AGSO) conducted surveys aboard the RV Lady Basten to determine the dispersion, fates and effects of produced formation water (PFW) discharged from the ‘ Harriet A ’ oil production platform near the Montebello Islands. This report is one of four related papers and describes the non-volatile hydrocarbon chemistry studies. The dispersion of the PFW into dissolved and particulate fractions of seawater were measured using moored high volume water samplers, surface screen samplers and moored and drifting sediment traps. Bio-accumulation was studied using transplanted oysters, and dispersion measured into sediment with benthic grabs.Results showed enrichment in non-volatile hydrocarbons in surface microlayer samples to a distance of 1·8 km in the direction of tidal flow. Concentrations in surface microlayers near the platform varied by an order of magnitude and corresponded to when a surface slick was visible or not visible. Concentrations of oil in seawater ranged from 2·0 to 8·5 μg l−1at near stations to 1·3 μg l−1at 1·8 km. Water column samples showed the processes of desorption from particles for soluble components occur within the range of 1·8 km. Most particulate hydrocarbons drop out of suspension within c. 1 to 2 km from the platform. Fluxes of particulate hydrocarbons through the water column at c. 1 km, as estimated by moored sediment traps in 1995, were 138 to 148 ng cm−2day−1. A decrease in sediment concentrations within c. 1 km of the platform was measured as 2·45±1·29 μg g−1dry wt (n=15) in 1994 to 0·86±0·54 μg g−1dry wt (n=21) in 1995, after the platform installed a centrifugal separator in the discharge treatment process. Thus the residence time of this relatively low molecular weight oil was estimated in the coarse aerobic sands surrounding the platform to be less than one year. Oysters suspended near the platform bio-accumulated hydrocarbons and other lipophilic organics in their tissues. Uptake rates and bio-concentration factors of hydrocarbons indicated potential toxicity at the near-field stations within c. 1 km radius.A mass balance was constructed to show the partitioning of the input of hydrocarbons from the PFW into the surrounding marine ecosystem. The rates of dissipation processes were estimated as follows: dilution from tidal currents>degradation in the water column>sedimentation>evaporation. The calculations based on maximum concentrations measured in the environmental samples accounted for 85% of the daily input suspended within a 1 km radius.It is estimated that the potential zone of toxic influence in the water column extends to a distance of approximately 1 km. Concentrations of oil in sediments were too low to indicate potential toxicity. By the collaborative application of oceanographic and geochemical techniques to marine environmental problems, we endeavour to provide effective feedback to the oil industry to gauge the effectiveness of their operational strategies in minimizing impact in these pristine regions.  相似文献   

8.
Representative profiles of inorganic nitrogenous species dissolved in interstitial waters of coral reef sands are presented. Ammonium is the dominant nitrogenous species in these pore waters with concentrations of up to 40 μm. Nitrate is present but in lower concentrations. Nitrite is found only occasionally in trace amounts. Computations of diffusive fluxes and inferences concerning microbial activity are derived from the profile structures. Computed flux rates of nitrogenous species from the sediment to the water column range between 0.75 and 1.37 μM m−1 h−1. These inputs may represent a significant source of recycled nitrogen to the primary producers of the coral reef ecosystem.  相似文献   

9.
Heterotrophic mineralization of dissolved organic nitrogen (DON) can be a major source of N for primary producers. During the summer growing season in mesooligotrophic Castle Lake, dissolved inorganic nitrogen (DIN) is often below detection (<0.1 μg-atom N l−1) whereas DON can vary between 7 and 17 μg-atom N. The heterotrophic metabolism of glutamate resulted in the recycling of both carbon and nitrogen, but not at the same rate. The uptake of 15N- and 14C-labeled glutamate showed that C was preferentially assimilated relative to N resulting in an N-mineralization rate of 2.5–3.0 ng-atom N l−1 h−1. This suggests that heterotrophs in Castle Lake are not N-deficient, and metabolism of organic compounds results in the release of DIN which is available for primary production.  相似文献   

10.
The concentrations of total lead were determined in both ordinary coastal seawater and in coastal waters highly polluted with sewage. The average concentration of total lead ranged from about 25 ng/kg in surface samples of the former type to an average of 150 ng/kg in the latter type. 0.4−μm filtrate lead was found to be equivalent to lead extracted from untreated seawater by dithizone in chloroform. In highly polluted waters, particle lead ranged from 56 to 39% of the total lead, with the proportion increasing as the amount of sewage in the seawater increased. Virtually all of the lead in sewage is contained in the particle phase before it enters the ocean but about 11% is made freely available by cation exchange when the sewage is mixed with seawater. In ordinary coastal waters that are not highly polluted with sewage lead, particle lead ranged from 90 to > 20%, and most of this lead was associated with plankton. About one-third of total lead, or one-half of particle lead, in untreated seawater adheres to the walls of the water container within the first day. Upon prolonged standing (> 3 months) most of the remaining particle lead can be collected on the surface of algal colonies growing on the walls of the water container. The concentrations of freely available lead in seawater do not seem to be significantly affected by wall adsorption. The 206Pb/207Pb ratio of total lead in coastal surface seawater collected near Los Angeles was 1.194, and a day earlier was 1.188 near La Jolla. It is believed that this shows lack of mixing of contributions from two different sources of lead pollution: a pulse of rain-storm runoff of gasoline lead(206Pb/207Pb 1.197) from paved surfaces added to Los Angeles waters; and sewage lead (206Pb/207Pb 1.188) from San Diego added to La Jolla waters.  相似文献   

11.
Mussels (Mytilus edulis L.) were exposed to North Sea crude oil, microencapsulated oil and dispersants, singly and in combination, and growth rates measured at 24–48 h intervals.Exposure to microencapsulated pure oil (2·0–2·1 mg litre−1) and to microencapsulated mixtures of oil (2·2−2·5 mg litre-1+5 % of the different dispersants (FINASOL OSR 5, COREXIT 9527, DISPOLENE 36 S) gave approximately the same reduction in growth rate (80–90%) within 170h.Oil chemically dispersed with DISPOLENE 36 S and a pure oil mechanically dispersed in water were significantly less toxic. In high concentrations (2 mg litre−1) all disperants are toxic, DISPOLENE 36 S ssignificantly more than the others.Mussels exposed for 170 h to microencapsulated oil and to microencapsulated oil dispersant mixtures recovered to control growth within 300 h in clean seawater, while in those given pure oil-in-water suspension, the recovery was slower.It is concluded that the toxicity of oil is mainly related to size and concentration of oil particles, while the effect of 5% dispersants added is negligible.  相似文献   

12.
The concentration and distribution of dissolved nitrogenous compounds was studied in the Greenland Sea in June 1991. Dissolved organic (DON) and inorganic nitrogen (DIN) were determined in seawater of different origin and depth. Dissolved organic matter was isolated on XAD-2 resin and fractionated into its non-humic hydrophilic (H1), and so-called humic components (hydrophobic acid, HbA, and hydrophobic neutral, HbN). From all fractions the DON content was subsequently determined. Total DON concentrations were about 5 μmol Ni−1 in the surface and 3 μmol NI−1 below depths of 150–200 m. DIN varied between 1.5 and 1.6 μmol NI−1. There was a highly significant inverse correlation (r = −0.75) between DON and DIN suggesting a close coupling in the uptake and release of the different forms of nitrogen. The mean DON concentrations of the XAD-fractions were for HI = 2.3 μmol Ni−1, for HbA = 0.8 μmol NI− and for HbN = 1.0 μmol NI−1. The average percentage contributions were, respectively, 56%, 19% and 25%. This means that about 56% of the total DON does not belong to the ‘humic fraction’. The HbN fraction was evenly distributed in the water column, without any obvious relationship with water masses, depth, or nutrient status. In contrast, the HbA fraction showed a significant correlation with total DON.  相似文献   

13.
The spatial and temporal distribution of cadmium (Cd) and phosphate in the Southern Ocean are related to biology and hydrography. During a period of 18 days between transects 5/6 and 11, a phytoplankton spring bloom developed in the Polar Frontal region. Upper water Cd concentrations were not depleted and ranged from 0.2 to 0.8 nM at about 10 m depth. These relatively high Cd concentrations are attributed to upwelling of Upper Circumpolar Deep Water (0.5–1.2 nM in the core) in combination with low biological productivity (0.2 to 0.3 mg m−3 chlorophyll-a, 0.3 g C m−2 d−1). Total particulate Cd concentrations at 40 m depth were between 0.02 and 0.14 nM with the maximum in concentration in the Polar Frontal region. Most of the particulate Cd at this depth (85–94%) was detected in the first phase of a sequential chemical leaching treatment which includes adsorbed Cd as well as Cd incorporated in algae. The Polar Frontal region was characterized by minima in Cd concentration and Cd/phosphate ratio of seawater at both transects; values were the lowest at transect 11 after development of the spring bloom which was dominated by diatoms. This decreasing Cd/phosphate ratio in seawater during spring bloom development was attributed to preferential Cd gross uptake which more than compensated the process of preferential Cd recycling. Within the Upper Circumpolar Deep Water, Cd showed a maximum in concentration similar to that of the major nutrients. Both the Cd concentration and the Cd/phosphate ratio of the deeper water increased in southern direction, from 0.4 to 0.7 nM and from 0.2 to 0.3 nM/μM, respectively. Antarctic Intermediate Water has a Cd concentration of 0.21 nM with a Cd/phosphate ratio of 0.10 nM/μM. In Antarctic Bottom Water, Cd concentrations ranged from 0.60 to 0.82 nM.  相似文献   

14.
Many aquatic contaminants, because of low water solubility (hydrophobicity) or association with floatable particles, concentrate at the sea surface. Thirty-six samples of the sea-surface microlayer (SMIC), the upper 50 μm, were collected from sites in Puget Sound, Washington State. Sites included three urban bays, central Puget Sound, and a rural reference site. Exposure of floating fish eggs to approximately half of these samples resulted in sublethal and lethal toxic effects (Hardy et al., 1987c).Chemical analyses revealed high concentrations of contaminants in many of the samples. Major temporal and spatial differences in sea-surface chemistry occurred, but maximum (for all) and mean (for 1985) concentrations were aromatic hydrocarbons, 8030 (mean 132) μg liter−1: saturate hydrocarbons, 2060 μg liter−1: pesticides, 43·8 (mean 0·46) ng liter−1; PCBs, 3890 (mean 631) ng liter−1; and total metals, 4750 (mean 626) μg liter−1. Stepwise multivariate regression indicated that the percentage of fish eggs developing to normal live larvae decreased with increasing concentrations of a complex mixture of contaminants. Principal component analysis demonstrated that the major types of contaminants did not differ greatly in their statistical contribution to the toxicity, i.e. no single chemical was responsible for the observed toxicity.The chemical composition of the SMIC samples suggested that contamination originated from a variety of sources including atmospheric deposition, terrestrial runoff of fossil fuel combustion products, and sewage disposal.  相似文献   

15.
Using the seawater dilution technique, we measured phytoplankton growth and microzooplankton grazing rates within and outside of the 1999 Bering Sea coccolithophorid bloom. We found that reduced microzooplankton grazing mortality is a key component in the formation and temporal persistence of the Emiliania huxleyi bloom that continues to proliferate in the southeast Bering Sea. Total chlorophyll a (Chl a) at the study sites ranged from 0.40 to 4.45 μg C l−1. Highest phytoplankton biomass was found within the bloom, which was a mixed assemblage of diatoms and E. huxleyi. Here, 75% of the Chl a came from cells >10 μm and was attributed primarily to the high abundance of the diatom Nitzschia spp. Nutrient-enhanced total phytoplankton growth rates averaged 0.53 d−1 across all experimental stations. Average growth rates for >10 μm and <10 μm cells were nearly equal, while microzooplankton grazing varied among stations and size fractions. Grazing on phytoplankton cells >10 μm ranged from 0.19 to 1.14 d−1. Grazing on cells <10 μm ranged from 0.02 to 1.07 d−1, and was significantly higher at non-bloom (avg. 0.71 d−1) than at bloom (avg. 0.14 d−1) stations. Averaged across all stations, grazing by microzooplankton accounted for 110% and 81% of phytoplankton growth for >10 and <10 μm cells, respectively. These findings contradict the paradigm that microzooplankton are constrained to diets of nanophytoplankton and strongly suggests that their grazing capability extends beyond boundaries assumed by size-based models. Dinoflagellates and oligotrich ciliates dominated the microzooplankton community. Estimates of abundance and biomass for microzooplankton >10 μm were higher than previously reported for the region, ranging from 22,000 to 227,430 cells l−1 and 18 to 164 μg C l−1. Highest abundance and biomass occurred in the bloom and corresponded with increased abundance of the large ciliate Laboea, and the heterotrophic dinoflagellates Protoperidinium and Gyrodinium spp. Despite low grazing rates on phytoplankton <10 μm within the bloom, the abundance and biomass of small microzooplankton (<20 μm) capable of grazing E. huxleyi was relatively high at bloom stations. This body of evidence, coupled with observed high grazing rates on large phytoplankton cells, suggests the phytoplankton community composition was strongly regulated by herbivorous activity of microzooplankton. Because grazing behavior deviated from size-based model predictions and was not proportional to microzooplankton biomass, alternate mechanisms that dictate levels of grazing activity were in effect in the southeastern Bering Sea. We hypothesize that these mechanisms included morphological or chemical signaling between phytoplankton and micrograzers, which led to selective grazing pressure.  相似文献   

16.
Laboratory exposures of the urchin Lytechinus pictus to sediment dosed with varying concentrations of hydrogen sulfide (H2S), but without elevated organic material, were conducted. Changes in mortality, behavior, growth and gonad production were measured during 49 days' flow through exposures. Hydrogen sulfide concentrations of 165·8 μ liter−1 in pore water caused significant changes in all parameters measured. Concentrations as low as 32·9 μ liter−1 caused significant decreases in wet weight and male gonad production. A concentration of 91·8 μ liter−1 caused the mortality rate to increase 100-fold over control exposures (0·63 μ liter−1). Sublethal effects on growth and gonad production could have been caused by either direct biochemical inhibition by H2S or secondarily through behavioral modifications. Hydrogen sulfide concentrations above 165·8 μ liter−1 are common near sewage outfalls and could contribute to changes in species composition and sediment toxicity that occur there.  相似文献   

17.
Macroalgae biomass and concentrations of nitrogen, phosphorus and chlorophyll a were determined weekly or biweekly in water and sediments, during the spring-summer of 1985 in a hypertrophic area of the lagoon of Venice. Remarkable biomass production (up to 286 g m−2 day−1, wet weight), was interrupted during three periods of anoxia, when macroalgal decomposition (rate: up to 1000 g m−2 day−1) released extraordinary amounts of nutrients. Depending on the macroalgae distribution in the water column, the nutrients released in water varied from 3·3 to 19·1 μg-at litre−1 for total inorganic nitrogen and from 1·8 to 2·7 μg-at litre−1 for reactive phosphorus. Most nutrients, however, accumulated in the surficial sediment (up to 0·640 and to 3·06 mg g−1 for P and N respectively) redoubling the amounts already stored under aerobic conditions, Phytoplankton, systematically below 5 mg m−3 as Chl. a, sharply increased up to 100 mg m−3 only after the release of nutrients in water by anaerobic macroalgal decomposition. During the algal growth periods, the N:P atomic ratio in water decreased to 0·7, suggesting that nitrogen is a growth-limiting factor. This ratio for surficial sediment was between 6·6 and 13·1, similar to that of macroalgae (8·6–12·0).  相似文献   

18.
Following the observation of high concentrations of cadmium in Gironde estuarine waters, the response of embryos and larvae of the Japanese oyster, Crassostrea gigas to this heavy metal at various salinity regimes was studied for 10 days in the laboratory. The experimental design was a 4 x 4 factorial experiment using concentrations of cadmium of 0, 10, 20 and 50 μg litre−1 and salinities of 20, 25, 30 and 35‰. Statistical analysis indicated that the salinity changes have important effects on the embryonic development, survival and growth of C. gigas larvae. No deleterious effect of the toxin at all cadmium concentrations and no interaction between cadmium and salinity were found.  相似文献   

19.
Fatty acids and hydrocarbons of sedimenting particles were investigated in the northeastern Adriatic Sea from November 1988 to December 1989. Particles were collected at approximately monthly intervals, using sediment traps deployed at 30 m depth (2 m above bottom). Seasonal changes in sedimentation of particulate matter were very pronounced. Hydrocarbon fluxes and concentrations were found to vary significantly depending on the season. They averaged 2.69 ± 1.44 mg m−2 day−1 and 232.4 ± 90.93 μg g−1 in winter, respectively. In late spring-early summer the corresponding values amounted to 0.045 ± 0.015 mg m−2 day−1 and 13.72 ± 5.56 μg g−1, and they increased towards autumn, when mean values of 0.517 ± 0.228 mg m−2 day−1 and 98.86 ± 48.72 μg g−1 were obtained. In contrast, fatty acid fluxes and concentrations were low during winter (0.26 ± 0.08 mg m−2 day−1 and 21.95 ± 3.35 μg g−1), increased slightly towards the summer (0.48 ± 0.12 mg m−2 day−1 and 139.9 ± 44.6 μ g−1) and reached maximum rate and concentration in autumn, when average values were 1.98 ± 1.30 mg m2 day−1 and 489.1 ± 186.7 μg g−1, respectively. The differences in composition, concentrations and fluxes of the fatty acids and hydrocarbons were related to the sources of sedimenting material, reflecting the influence of resuspension of bottom sediments during winter and the appearance of mucus aggregates during summer and their subsequent deposition in autumn.  相似文献   

20.
To estimate the source and diagenetic state of organic matter reaching bottom sediments, fatty acids and sterols were measured in unconsolidated surface material (flocs) at 12 sites ranging from 600 to 2000 m across the mid-Atlantic continental slope off Cape Hatteras, North Carolina. Total free and esterefied fatty acids were similar in distribution and concentration to other coastal systems, with values ranging from 0.64 to 46.52 μg mg−1 organic carbon (1.10–68.85 μg g−1 dry sediment). Although shallow (600 m) stations contained significantly greater fatty acid concentrations than deep (> 1400m) stations, high variability observed at mid-depth (800 m) collections precluded a consistent relationship between total fatty acid concentration and station depth. At three sites where underlying sediments were also collected, decreases in total fatty acids, reduced amounts of polyenoic acids and significant presence of bacterial fatty acid suggest rapid reworking of labile organic material that reaches the sediment surface. The distribution of sterols was remarkably consistent among all sites even though there were large variations in concentrations (1.8–20.7 μg mg−1 organic carbon). Sterol composition indicated phytoplankton, principally diatoms and dinoflagellates, as the principal source of labile organic matter to sediments, together with a significant input of cholest-5-en-3β-ol typical of zooplankton and their feeding activity. A minor but widespread terrigenous input was also evident based upon significant concentrations of sterols dominant in vascular plants.  相似文献   

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