Acoustic backscatter contrast in depositional sediments under salmon farm cages in the Bay of Fun... more Acoustic backscatter contrast in depositional sediments under salmon farm cages in the Bay of Fundy, Canada, was correlated with localized changes in (unknown) sediment geotechnical properties, as indicated by 4 independent measures of organic enrichment. Sediment total sulfides and redox potentials, enzyme hydrolyzable amino acids, sediment profile imaging and macrofaunal samples, taken at mid-cage positions, each rejected the null hypothesis that salmon cage footprints, defined acoustically as high backscatter areas, were indistinguishable from nearby reference areas. Acoustic backscatter imaging appears capable of mapping organic enrichment in depositional sediments caused by excessive inputs of salmon farm wastes associated with intensive aquaculture.
Marine invertebrate deposit feeders secrete surfactants into their gut fluid in concentrations su... more Marine invertebrate deposit feeders secrete surfactants into their gut fluid in concentrations sufficient to induce micelle formation, enhancing solubilization of sedimentary lipids. We isolated and identified 3 related surfactant molecules from the deposit-feeding polychaete lugworm Arenicola marina. Surfactants were isolated and separated by a combination of solvent extraction and thin-layer and gas chromatography. Identification was performed using mass and infrared spectrometry, coupled to various derivatization and hydrolysis reactions. A. marina produces a mixture of related yet distinct anionic surfactants composed of branched, C9, saturated and unsaturated fatty acids that are amide linked to leucine or glycine residues, showing some similarity to crustacean surfactants. The critical micelle concentration of the mixture of these surfactants in gut fluid was about 2 mM, and total concentrations ranged from 5.5 to 19.5 mM. The hydrophilic amide linkage helps to explain previous observations that gut surfactants do not adsorb onto sediment transiting the gut.
The relationship between total and chemically labile Fe has been studied in estuarine, coastal an... more The relationship between total and chemically labile Fe has been studied in estuarine, coastal and shelf waters of the Gulf of Maine, U.S.A. Measurements of the labile fraction of total Fe, defined by complexation with 8-hydroxyquinoline in 1 h, correlate with the availability of Fe to marine phytoplankton and therefore can be used to estimate Fe availability in seawater. The results show that the relative lability (= labile/total) of Fe in seawater varied both spatially and temporally from near-zero to 100%. Although particulate Fe (>0.45 #m) was generally less labile than dissolved Fe (<0.45 /zm), the particulate fraction often contributed substantially to labile Fe concentrations overall. Conversely, as much as 75% of'dissolved' Fe was non-labile, and therefore was probably not available to phytoplankton. In seawater/river-water mixing experiments, aggregation diminished the relative lability of Fe by ~ 30%, even though much of it remained in the 'dissolved' fraction. Considering phytoplankton nutrition, these results demonstrate that equating dissolved Fe concentrations with 'available' metal can be misleading. Furthermore, the large variability observed in the labile proportion of total Fe in seawater indicates that Fe availability to phytoplankton cannot be estimated by applying fixed lability-ratios to total Fe concentrations.
We quantified rates of photochemical dissolution (photodissolution) of organic carbon in coastal ... more We quantified rates of photochemical dissolution (photodissolution) of organic carbon in coastal Louisiana suspended sediments, conducting experiments under well-defined conditions of irradiance and temperature. Optical properties of the suspended sediments were characterized and used in a radiative transfer model to compute irradiances within turbid suspensions. Photodissolution rate increased with temperature (T), with activation energy of 32 6 7 kJ mol 21 , which implicates indirect (non-photochemical) steps in the net reaction. In most samples, dissolved organic carbon (DOC) concentration increased approximately linearly with time over the first 4 h of irradiation under broadband simulated sunlight, after higher rates in the initial hour of irradiation. Four-hour rates ranged from 2.3 mmol DOC m 23 s 21 to 3.2 mmol DOC m 23 s 21 , but showed no relation to sample origin within the study area, organic carbon or reducible iron content, or mass-specific absorption coefficient. First-hour rates were higher-from 3.5 mmol DOC m 23 s 21 to 7.8 mmol DOC m 23 s 21-and correlated well with sediment reducible iron (itself often associated with organic matter). The spectral apparent quantum yield (AQY) for photodissolution was computed by fitting DOC photoproduction rates under different spectral irradiance distributions to corresponding rates of light absorption by particles. The photodissolution AQY magnitude is similar to most published dissolved-phase AQY spectra for dissolved inorganic carbon photoproduction, which suggests that in turbid coastal waters where particles dominate light absorption, DOC photoproduction from particles exceeds photooxidation of DOC.
Polycyclic aromatic hydrocarbons (PAHs) contamination of topsoil in Benxi City, Northeast China w... more Polycyclic aromatic hydrocarbons (PAHs) contamination of topsoil in Benxi City, Northeast China was investigated in this study, and sampling sites were located in industrial area and residential area. Results demonstrate that there is high variability in the total PAHs concentrations, ranging from 783.00 ng/g to 729 076.29 ng/g dry weight in the topsoil of Benxi City and the pollution in industrial area is the most serious. The results also present that higher molecular weight PAHs (4–6 rings) contribute substantially (79.03%) to the overall content of PAHs. The PAHs sources were determined with factor analysis by nonnegative constraints, and the results show that PAHs originating from traffic tunnel, power plant, coke oven and residential emission sources, account for 27.10%, 40.81%, 20.11% and 11.98%, respectively, of the total. The PAHs pollution is the most serious around Benxi Iron and Steel Group Corporation, and the PAHs mainly originate from coke oven and traffic tunnel, with the average contribution rate of 57.40% and 42.60%, respectively. The source apportionment results are basically consistent with the industry distribution, and the geographical and climatic characteristics of the study area.
The sediment-water interface in the coastal ocean is a highly dynamic zone controlling biogeochem... more The sediment-water interface in the coastal ocean is a highly dynamic zone controlling biogeochemical fluxes of greenhouse gases, nutrients, and metals. Processes in the sediment mixed layer (SML) control the transfer and reactivity of both particulate and dissolved matter in coastal interfaces. Here we map the global distribution of the coastal SML based on excess 210Pb (210Pbex) profiles and then use a neural network model to upscale these observations. We show that highly dynamic regions such as large estuaries have thicker SMLs than most oceanic sediments. Organic carbon preservation and SMLs are inversely related as mixing stimulates oxidation in sediments which enhances organic matter decomposition. Sites with SML thickness >60 cm usually have lower organic carbon accumulation rates (<50 g C m−2 yr−1) and total organic carbon/specific surface area ratios (<0.4 mg m−2). Our global scale observations reveal that reworking can accelerate organic matter degradation and re...
We focus on the role played by food quality in controlling sediment mixing by benthic animals in ... more We focus on the role played by food quality in controlling sediment mixing by benthic animals in coastal sediments. We hypothesize that a threshold level of food abundance controls whether or not significant mixing can occur, that this threshold is driven by protein concentrations, and regional differences in mixing among coastal regions may therefore be explained by differences in protein contents.
Wetland sediments undergo dry-wet cycles that may change their structural properties and affect g... more Wetland sediments undergo dry-wet cycles that may change their structural properties and affect geochemical behavior of associated organic compounds. In this study, we examined the effect of drying on particle size distributions and the rapid (24h) sorption reactions of polycyclic aromatic hydrocarbons (PAHs) with salt marsh sediments in Nueces Delta, South Texas. Drying reduced the fraction of fine particles in organically richer sediments, indicating structural rearrangement of organic matter and mineral aggregates. Among the 16 EPA priority PAHs examined, dried sediment preferentially released 1.0-7.5% of phenanthrene, fluoranthene and pyrene to added seawater (solid: water mass ratio of 1/100) - significantly greater than release from sediments maintained in the wet state. On the other hand, drying also increased the affinity of sedimentary organic matter (SOM) for experimentally amended (deuterated) phenanthrene relative to continually wet sediments. Further, deuterated phenant...
Lecture Notes on Coastal and Estuarine Studies, 1989
Several lines of evidence imply that deposit feeders can and do use non-living food resources in ... more Several lines of evidence imply that deposit feeders can and do use non-living food resources in marine sediments. Indeed, non-living food may comprise the bulk of the food for many species. The ability to use such food is indicated by feeding experiments which have shown ingestion selectivity by deposit feeders for protein-coated beads (Taghon 1982; Taghon and Jumars 1984) and demonstrated an ability to absorb non-living organic matter (Lopez et al., this volume). Tenore and coworkers (e.g. Tenore 1983) have also demonstrated the ability of polychaetes to utilize non-living detrital material. The actual use of non-living material in situ has been implied primarily via budgetary calculations (e.g. Canunen 1980; Rice et al. 1986), which show that the required assimilation efficiency of sedimentary organic matter indicates a bioavailable organic pool larger than can be provided by the living component.
Reference Module in Earth Systems and Environmental Sciences#R##N#Treatise on Estuarine and Coastal Science, 2011
Colloids are 1 nm to 1 µm particles that usually become destabilized in estuaries due to rapid ch... more Colloids are 1 nm to 1 µm particles that usually become destabilized in estuaries due to rapid changes in salinity, resulting in aggregation that brings them into the traditional particle size range. Best studied are the heterogeneous colloids originating on land. Colloids deriving from the ocean and within estuaries are less well studied. Organic- and iron-rich colloids dominate this aggregation reaction, also entraining many other elements. Aggregation requires an increase in the stickiness of these colloids, followed by colloid collision driven largely by Brownian motion. Resultant aggregates may not settle from the water column during estuarine residence times unless other settling particles are present. Colloid aggregation thus affects chemical reactivity, ecosystems, and the budgets of many biogeochemically important materials in estuaries.
This chapter will consider the term “sediment-water interface” as a double entendre and discuss t... more This chapter will consider the term “sediment-water interface” as a double entendre and discuss the interface both as the horizontal zone where the water column meets the sediment column and as the wetted surface of mineral grains which occur in this horizontal zone. Hereafter, the first definition will be termed the “sediment-water interface,” and the second the “mineral-water interface.” The interface in both of these senses is a zone of concentration of organic matter, albeit for quite different reasons.
Deep Sea Research Part A. Oceanographic Research Papers, 1991
... (B) Decrease in the ambient oxinc-Fe concentrations m Damariscotta surface water with aging i... more ... (B) Decrease in the ambient oxinc-Fe concentrations m Damariscotta surface water with aging in the dark. The water was collected at noontime under a clear, sunny sky. Oxine-Fc determinations were done within duplicate bottles removed during the time course. ...
Abstract The vertical distribution of reduced species and phosphate was monitored throughout a su... more Abstract The vertical distribution of reduced species and phosphate was monitored throughout a summer stagnation period in hypereutrophic Lake Sebasticook, Maine. The oxygen demand of reduced species released from hypolimnetic sediments was dominated by methane, followed by ammonium, and included minor contributions from Fe 2+ , Mn 2+ and sulfide. Release of iron and manganese from the sediments was apparently controlled by dissolution of siderite and rhodochrosite, with the requisite acidity for the dissolution provided by methanogenesis. Redox recycling of these two metals occurs in two vertically displaced “wheels”, which enhance oxidant delivery to the hypolimnion beyond that provided by oxygen diffusion alone. Phosphorus is tightly coupled to the “ferrous wheel”, in the absence of wind events, and is scavenged with a stoichiometry consistent with Tessenow's (Tessenow U., Arch. Hydrobiol. Suppl. 47 , 1–79, 1974) laboratory studies.
The concentration and composition of suspended particulate matter (SPM) were measured weekly for ... more The concentration and composition of suspended particulate matter (SPM) were measured weekly for a period of one year in the flood front waters traversing a muddy tidal flat. SPM concentrations were lowest in the winter when portions of the tidal flat were covered with ice, and biological activity was minimal. In contrast, the summer months had the highest SPM concentrations which reflected increased bottom resuspension. The two main sources of SPM were suspended matter carried in from offshore on the flooding tide and resuspended in situ bottom sediments. The offshore source was characterized by low SPM concentrations, coarse textures, and a high content of protein and chlorophyll 'a'. Samples taken during resuspension events (storms/showers) had high SPM concentrations, finer textures, and were enriched in dead detrital organic material (phaeophytin). At any one time the SPM was primarily an admixture of these two sources. The highest SPM measurements were taken during storm events, with rainfall seeming to play a dominant physical role in aiding resuspension. SPM concentrations, textures, and compositions collected during the storms closely approximated SPM measurements made over newly dug 'clam flats'.
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 1990
The principle of lost opportunity from optimal foraging theory, coupled with recent information a... more The principle of lost opportunity from optimal foraging theory, coupled with recent information about fluxes in the deep sea, allows prediction of feeding behaviours potentially specific to deep-sea deposit feeders. One possible strategy, thus far documented only indirectly, is to ‘ squirrel ’ away rich food from the seasonal or episodic pulses that recently have been shown to fuel meiofaunal growth. Echiurans and sipunculids show morphological and faecal handling patterns consonant with this suggestion. Where it is prevalent, this foraging strategy can have profound effects on stratigraphy. Autocoprophagy is another expected behaviour across a wider taxonomic spectrum, but one that is especially difficult to document. The principle of lost opportunity also predicts highly selective ingestion, not necessarily accomplished by the assessment of individual particles but possibly through pit building in areas where fluids move near-bed material. Under many depositions regimes, small but...
Acoustic backscatter contrast in depositional sediments under salmon farm cages in the Bay of Fun... more Acoustic backscatter contrast in depositional sediments under salmon farm cages in the Bay of Fundy, Canada, was correlated with localized changes in (unknown) sediment geotechnical properties, as indicated by 4 independent measures of organic enrichment. Sediment total sulfides and redox potentials, enzyme hydrolyzable amino acids, sediment profile imaging and macrofaunal samples, taken at mid-cage positions, each rejected the null hypothesis that salmon cage footprints, defined acoustically as high backscatter areas, were indistinguishable from nearby reference areas. Acoustic backscatter imaging appears capable of mapping organic enrichment in depositional sediments caused by excessive inputs of salmon farm wastes associated with intensive aquaculture.
Marine invertebrate deposit feeders secrete surfactants into their gut fluid in concentrations su... more Marine invertebrate deposit feeders secrete surfactants into their gut fluid in concentrations sufficient to induce micelle formation, enhancing solubilization of sedimentary lipids. We isolated and identified 3 related surfactant molecules from the deposit-feeding polychaete lugworm Arenicola marina. Surfactants were isolated and separated by a combination of solvent extraction and thin-layer and gas chromatography. Identification was performed using mass and infrared spectrometry, coupled to various derivatization and hydrolysis reactions. A. marina produces a mixture of related yet distinct anionic surfactants composed of branched, C9, saturated and unsaturated fatty acids that are amide linked to leucine or glycine residues, showing some similarity to crustacean surfactants. The critical micelle concentration of the mixture of these surfactants in gut fluid was about 2 mM, and total concentrations ranged from 5.5 to 19.5 mM. The hydrophilic amide linkage helps to explain previous observations that gut surfactants do not adsorb onto sediment transiting the gut.
The relationship between total and chemically labile Fe has been studied in estuarine, coastal an... more The relationship between total and chemically labile Fe has been studied in estuarine, coastal and shelf waters of the Gulf of Maine, U.S.A. Measurements of the labile fraction of total Fe, defined by complexation with 8-hydroxyquinoline in 1 h, correlate with the availability of Fe to marine phytoplankton and therefore can be used to estimate Fe availability in seawater. The results show that the relative lability (= labile/total) of Fe in seawater varied both spatially and temporally from near-zero to 100%. Although particulate Fe (>0.45 #m) was generally less labile than dissolved Fe (<0.45 /zm), the particulate fraction often contributed substantially to labile Fe concentrations overall. Conversely, as much as 75% of'dissolved' Fe was non-labile, and therefore was probably not available to phytoplankton. In seawater/river-water mixing experiments, aggregation diminished the relative lability of Fe by ~ 30%, even though much of it remained in the 'dissolved' fraction. Considering phytoplankton nutrition, these results demonstrate that equating dissolved Fe concentrations with 'available' metal can be misleading. Furthermore, the large variability observed in the labile proportion of total Fe in seawater indicates that Fe availability to phytoplankton cannot be estimated by applying fixed lability-ratios to total Fe concentrations.
We quantified rates of photochemical dissolution (photodissolution) of organic carbon in coastal ... more We quantified rates of photochemical dissolution (photodissolution) of organic carbon in coastal Louisiana suspended sediments, conducting experiments under well-defined conditions of irradiance and temperature. Optical properties of the suspended sediments were characterized and used in a radiative transfer model to compute irradiances within turbid suspensions. Photodissolution rate increased with temperature (T), with activation energy of 32 6 7 kJ mol 21 , which implicates indirect (non-photochemical) steps in the net reaction. In most samples, dissolved organic carbon (DOC) concentration increased approximately linearly with time over the first 4 h of irradiation under broadband simulated sunlight, after higher rates in the initial hour of irradiation. Four-hour rates ranged from 2.3 mmol DOC m 23 s 21 to 3.2 mmol DOC m 23 s 21 , but showed no relation to sample origin within the study area, organic carbon or reducible iron content, or mass-specific absorption coefficient. First-hour rates were higher-from 3.5 mmol DOC m 23 s 21 to 7.8 mmol DOC m 23 s 21-and correlated well with sediment reducible iron (itself often associated with organic matter). The spectral apparent quantum yield (AQY) for photodissolution was computed by fitting DOC photoproduction rates under different spectral irradiance distributions to corresponding rates of light absorption by particles. The photodissolution AQY magnitude is similar to most published dissolved-phase AQY spectra for dissolved inorganic carbon photoproduction, which suggests that in turbid coastal waters where particles dominate light absorption, DOC photoproduction from particles exceeds photooxidation of DOC.
Polycyclic aromatic hydrocarbons (PAHs) contamination of topsoil in Benxi City, Northeast China w... more Polycyclic aromatic hydrocarbons (PAHs) contamination of topsoil in Benxi City, Northeast China was investigated in this study, and sampling sites were located in industrial area and residential area. Results demonstrate that there is high variability in the total PAHs concentrations, ranging from 783.00 ng/g to 729 076.29 ng/g dry weight in the topsoil of Benxi City and the pollution in industrial area is the most serious. The results also present that higher molecular weight PAHs (4–6 rings) contribute substantially (79.03%) to the overall content of PAHs. The PAHs sources were determined with factor analysis by nonnegative constraints, and the results show that PAHs originating from traffic tunnel, power plant, coke oven and residential emission sources, account for 27.10%, 40.81%, 20.11% and 11.98%, respectively, of the total. The PAHs pollution is the most serious around Benxi Iron and Steel Group Corporation, and the PAHs mainly originate from coke oven and traffic tunnel, with the average contribution rate of 57.40% and 42.60%, respectively. The source apportionment results are basically consistent with the industry distribution, and the geographical and climatic characteristics of the study area.
The sediment-water interface in the coastal ocean is a highly dynamic zone controlling biogeochem... more The sediment-water interface in the coastal ocean is a highly dynamic zone controlling biogeochemical fluxes of greenhouse gases, nutrients, and metals. Processes in the sediment mixed layer (SML) control the transfer and reactivity of both particulate and dissolved matter in coastal interfaces. Here we map the global distribution of the coastal SML based on excess 210Pb (210Pbex) profiles and then use a neural network model to upscale these observations. We show that highly dynamic regions such as large estuaries have thicker SMLs than most oceanic sediments. Organic carbon preservation and SMLs are inversely related as mixing stimulates oxidation in sediments which enhances organic matter decomposition. Sites with SML thickness >60 cm usually have lower organic carbon accumulation rates (<50 g C m−2 yr−1) and total organic carbon/specific surface area ratios (<0.4 mg m−2). Our global scale observations reveal that reworking can accelerate organic matter degradation and re...
We focus on the role played by food quality in controlling sediment mixing by benthic animals in ... more We focus on the role played by food quality in controlling sediment mixing by benthic animals in coastal sediments. We hypothesize that a threshold level of food abundance controls whether or not significant mixing can occur, that this threshold is driven by protein concentrations, and regional differences in mixing among coastal regions may therefore be explained by differences in protein contents.
Wetland sediments undergo dry-wet cycles that may change their structural properties and affect g... more Wetland sediments undergo dry-wet cycles that may change their structural properties and affect geochemical behavior of associated organic compounds. In this study, we examined the effect of drying on particle size distributions and the rapid (24h) sorption reactions of polycyclic aromatic hydrocarbons (PAHs) with salt marsh sediments in Nueces Delta, South Texas. Drying reduced the fraction of fine particles in organically richer sediments, indicating structural rearrangement of organic matter and mineral aggregates. Among the 16 EPA priority PAHs examined, dried sediment preferentially released 1.0-7.5% of phenanthrene, fluoranthene and pyrene to added seawater (solid: water mass ratio of 1/100) - significantly greater than release from sediments maintained in the wet state. On the other hand, drying also increased the affinity of sedimentary organic matter (SOM) for experimentally amended (deuterated) phenanthrene relative to continually wet sediments. Further, deuterated phenant...
Lecture Notes on Coastal and Estuarine Studies, 1989
Several lines of evidence imply that deposit feeders can and do use non-living food resources in ... more Several lines of evidence imply that deposit feeders can and do use non-living food resources in marine sediments. Indeed, non-living food may comprise the bulk of the food for many species. The ability to use such food is indicated by feeding experiments which have shown ingestion selectivity by deposit feeders for protein-coated beads (Taghon 1982; Taghon and Jumars 1984) and demonstrated an ability to absorb non-living organic matter (Lopez et al., this volume). Tenore and coworkers (e.g. Tenore 1983) have also demonstrated the ability of polychaetes to utilize non-living detrital material. The actual use of non-living material in situ has been implied primarily via budgetary calculations (e.g. Canunen 1980; Rice et al. 1986), which show that the required assimilation efficiency of sedimentary organic matter indicates a bioavailable organic pool larger than can be provided by the living component.
Reference Module in Earth Systems and Environmental Sciences#R##N#Treatise on Estuarine and Coastal Science, 2011
Colloids are 1 nm to 1 µm particles that usually become destabilized in estuaries due to rapid ch... more Colloids are 1 nm to 1 µm particles that usually become destabilized in estuaries due to rapid changes in salinity, resulting in aggregation that brings them into the traditional particle size range. Best studied are the heterogeneous colloids originating on land. Colloids deriving from the ocean and within estuaries are less well studied. Organic- and iron-rich colloids dominate this aggregation reaction, also entraining many other elements. Aggregation requires an increase in the stickiness of these colloids, followed by colloid collision driven largely by Brownian motion. Resultant aggregates may not settle from the water column during estuarine residence times unless other settling particles are present. Colloid aggregation thus affects chemical reactivity, ecosystems, and the budgets of many biogeochemically important materials in estuaries.
This chapter will consider the term “sediment-water interface” as a double entendre and discuss t... more This chapter will consider the term “sediment-water interface” as a double entendre and discuss the interface both as the horizontal zone where the water column meets the sediment column and as the wetted surface of mineral grains which occur in this horizontal zone. Hereafter, the first definition will be termed the “sediment-water interface,” and the second the “mineral-water interface.” The interface in both of these senses is a zone of concentration of organic matter, albeit for quite different reasons.
Deep Sea Research Part A. Oceanographic Research Papers, 1991
... (B) Decrease in the ambient oxinc-Fe concentrations m Damariscotta surface water with aging i... more ... (B) Decrease in the ambient oxinc-Fe concentrations m Damariscotta surface water with aging in the dark. The water was collected at noontime under a clear, sunny sky. Oxine-Fc determinations were done within duplicate bottles removed during the time course. ...
Abstract The vertical distribution of reduced species and phosphate was monitored throughout a su... more Abstract The vertical distribution of reduced species and phosphate was monitored throughout a summer stagnation period in hypereutrophic Lake Sebasticook, Maine. The oxygen demand of reduced species released from hypolimnetic sediments was dominated by methane, followed by ammonium, and included minor contributions from Fe 2+ , Mn 2+ and sulfide. Release of iron and manganese from the sediments was apparently controlled by dissolution of siderite and rhodochrosite, with the requisite acidity for the dissolution provided by methanogenesis. Redox recycling of these two metals occurs in two vertically displaced “wheels”, which enhance oxidant delivery to the hypolimnion beyond that provided by oxygen diffusion alone. Phosphorus is tightly coupled to the “ferrous wheel”, in the absence of wind events, and is scavenged with a stoichiometry consistent with Tessenow's (Tessenow U., Arch. Hydrobiol. Suppl. 47 , 1–79, 1974) laboratory studies.
The concentration and composition of suspended particulate matter (SPM) were measured weekly for ... more The concentration and composition of suspended particulate matter (SPM) were measured weekly for a period of one year in the flood front waters traversing a muddy tidal flat. SPM concentrations were lowest in the winter when portions of the tidal flat were covered with ice, and biological activity was minimal. In contrast, the summer months had the highest SPM concentrations which reflected increased bottom resuspension. The two main sources of SPM were suspended matter carried in from offshore on the flooding tide and resuspended in situ bottom sediments. The offshore source was characterized by low SPM concentrations, coarse textures, and a high content of protein and chlorophyll 'a'. Samples taken during resuspension events (storms/showers) had high SPM concentrations, finer textures, and were enriched in dead detrital organic material (phaeophytin). At any one time the SPM was primarily an admixture of these two sources. The highest SPM measurements were taken during storm events, with rainfall seeming to play a dominant physical role in aiding resuspension. SPM concentrations, textures, and compositions collected during the storms closely approximated SPM measurements made over newly dug 'clam flats'.
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 1990
The principle of lost opportunity from optimal foraging theory, coupled with recent information a... more The principle of lost opportunity from optimal foraging theory, coupled with recent information about fluxes in the deep sea, allows prediction of feeding behaviours potentially specific to deep-sea deposit feeders. One possible strategy, thus far documented only indirectly, is to ‘ squirrel ’ away rich food from the seasonal or episodic pulses that recently have been shown to fuel meiofaunal growth. Echiurans and sipunculids show morphological and faecal handling patterns consonant with this suggestion. Where it is prevalent, this foraging strategy can have profound effects on stratigraphy. Autocoprophagy is another expected behaviour across a wider taxonomic spectrum, but one that is especially difficult to document. The principle of lost opportunity also predicts highly selective ingestion, not necessarily accomplished by the assessment of individual particles but possibly through pit building in areas where fluids move near-bed material. Under many depositions regimes, small but...
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