bluuebunny/crossref_metadata_2025 huggingface dataset:
Bio‐optical modeling of photosynthetic production in coastal waters
Authors: Smith R. C. , Prezelin B. B. , Bidigare R. R. , K. S. Baker
Published: April 2010

A physiological‐based bio‐optical model is used to estimate vertical profiles of instantaneous, diurnal, and integrated daily rates of in situ primary production throughout the water column at three stations across a coastal front. The model makes use of an empirical relationship between photosynthesis, quantum yield, and photosynthetically absorbed radiation and is a full spectral model with all relevant parameters determined as a function of wavelength. In the prior application of this bio‐optical model, parameters used to estimate quantum yield as a function of irradiance were wavelength‐independent and held constant. Here, the model is recast so that quantum yield is estimated with wavelength‐dependent photosynthesis‐irradiance parameters, Pmax the maximum rate of phytoplankton photosynthesis, and Ik the P‐I saturation parameter, which are allowed to vary with depth and time of day. Both Pmax‐dependent (assumed to be λ‐independent) and Ik‐dependent (known to be λ‐dependent) estimates of temporal/spatial changes in quantum yield were assessed. The model was tested in water masses where a net‐to‐nanoplankton transition was occurring in phytoplankton communities dominated by diatoms and prymnesiophytes. At each station there is close agreement between 14C productivity estimates derived from knowledge of diurnal patterns in P‐I parameters and productivity estimates derived from two variants of the bio‐optical model based on knowledge of spectral irradiance and phytoplankton pigmentation. The 14C and bio‐optical estimates of primary production also show similar vertical patterns for either instantaneous or daily integrated values. When compared with 14C estimates, Ik‐dependent bio‐optical estimates of photosynthetic rates give a closer match than bio‐optical estimates that are Pmax‐dependent. The model permits calculation of primary production from shipboard observations and may be useful for predicting production rates from bio‐optical data provided by untended buoys.
Surface pigments, algal biomass profiles, and potential production of the euphotic layer: Relationships reinvestigated in view of remote‐sensing applications
Authors: Morel André , Berthon Jean‐François
Published: April 2010

Maps of surface chlorophyllous pigment (Chl a + Pheo a) are currently produced from ocean color sensors. Transforming such maps into maps of primary production can be reliably done only by using light‐production models in conjunction with additional information about the column‐integrated pigment content and its vertical distribution.

As a preliminary effort in this direction, ∼4,000 vertical profiles of pigment (Chl a + Pheo a) determined only in oceanic Case 1 waters have been statistically analyzed. They were scaled according to dimensionless depths (actual depth divided by the depth of the euphotic layer, Ze) and expressed as dimensionless concentrations (actual concentration divided by the mean concentration within the euphotic layer). The depth Ze, generally unknown, was computed with a previously developed bio‐optical model. Highly significant relationships were found allowing 〈C〉tot the pigment content of the euphotic layer, to be inferred from the surface concentration, C̄pd, observed within the layer of one penetration depth. According to their C̄d values (ranging from 0.01 to >10 mg m−3), we categorized the profiles into seven trophic situations and computed a mean vertical profile for each. Between a quasi‐uniform profile in eutrophic waters and a profile with a strong deep maximum in oligotrophic waters, the shape evolves rather regularly. The well‐mixed cold waters, essentially in the Antarctic zone, have been separately examined. On average, their profiles are featureless, without deep maxima, whatever their trophic state. Averaged values of ρ, the ratio of Chl a to (Chl a + Pheo a), have also been obtained for each trophic category.

The energy stored by photosynthesizing algae, once normalized with respect to the integrated chlorophyll biomass 〈C〉tot is proportional to the available photosynthetic energy at the surface via a parameter ψ*, which is the cross‐section for photosynthesis per unit of areal chlorophyll. By taking advantage of the relative stability of ψ*, we can compute primary production from ocean color data acquired from space. For such a computation, inputs are the irradiance field at the ocean surface, the “surface” pigment from which 〈C〉tot can be derived, the mean ρ value pertinent to the trophic situation as depicted by the C̄pd or 〈C〉tot values, and the cross‐section ψ*. Instead of a constant ψ* value, the mean profiles can be used; they allow the climatological field of the ψ* parameter to be adjusted through the parallel use of a spectral light‐production model.
Bio‐optical provinces of the Northeast Pacific Ocean: A provisional analysis.
Authors: Mueller James L. , Lange R. Edward
Published: April 2010

A provisional analysis of satellite ocean color imagery and in situ profiles of spectral irradiance and Chl a fluorescence partitions the Northeast Pacific Ocean into four geographically and bio‐optically distinct provinces: the California Current system, the Alaskan gyre, the east central North Pacific central gyre, and the subarctic front. Within each province in a given 2‐month period (June– July 1985 and October–November 1982), a family of regression equations was found to accurately predict the vertical profiles of irradiance attenuation and normalized Chl a fluorescence from K490—the surface diffuse attenuation coefficient which can be estimated from remotely sensed ocean color. The irradiance attenuation profile (to the depth where irradiance is 0.1% of the surface value) is predicted directly from the reciprocal of K490. Prediction of the Chl a fluorescence profile is based on a log‐linear photoadaptive profile of fluorescence over diffuse optical depth—a conceptual model which robustly fit the entire sample analyzed. Given K490, the profile is determined from four regression models predicting the depth in meters of the fluorescence maximum, the optical depth of the deep background fluorescence minimum, the surface intercept of the profile, and the slope of the profile between the surface and maximum.
The measurement and penetration of ultraviolet radiation into tropical marine water
Authors: Fleischmann Esther M.
Published: April 2010

An inexpensive, easily deployed polymer film was used to measure the penetration of ultraviolet (UV) radiation in nearshore tropical water. Measurements were made to a depth of 25 m in Discovery Bay, Jamaica, with a UV‐sensitive polymer film in which o‐nitrobenzaldehyde is converted to o‐nitrosobenzoic acid. The film is sensitive in the range of 400–300 nm. UV radiation ranged from 5 µmol quanta s−1 m−2 at the surface to 0.05 at 25 m. The diffuse attenuation coefficient (k) varied between 2.6 and 0.09 m−1 with an average of 0.33 m−1. Diurnal measurements of UV at 1 m showed the shape of the curve to be similar to that of surface photosynthetically active radiation, with a maximum at 1200 hours. Integrated measurements of UV are useful in conjunction with the response of aquatic organisms to changes in this radiation.
Surface water‐quality studies in the interior marine environment of Denmark
Authors: Højerslev Niels K.
Published: April 2010

Suspended matter in terms of light scattering and gelbstoff in terms of fluorescence, temperature, and salinity have been measured on surface samples taken from the Øre Sund, the Kattegat, the Store Bælt, and the Baltic in January and August 1975 during the Danish Belt Project.

For the area investigated, the average surface concentration of suspended matter about doubled between January and August 1975, whereas the average surface gelbstoff concentration remained approximately unchanged.

The overall horizontal variation of the surface concentration of suspended matter attained its maximum in January 1975, being of the order of 10 times. For August 1975, this variation dropped appreciably, to the order of two times.

The overall horizontal variation of the surface gelbstoff concentration was about the same for January and August 1975, being of the order of two times. This suggests that biological activities such as primary production and organic decay are unrelated to the formation of gelbstoff in the sea.

Two older surface maps based on light scattering measurements similar to those above from the Øre Sund in April 1957 and November 1953 suggest that the surface concentration of suspended matter has more than tripled during the period 1953–1975.
Estimation of a photon budget for the upper ocean in the Sargasso Sea
Authors: Smith R. C. , Marra J. , Perry M. J. , Baker K. S. , Swift E. , Buskey E. , Kiefer D.A.
Published: April 2010

A photon budget based on the quanta absorbed and subsequent biological utilization is computed for a site in the northwestern Sargasso Sea in spring. The budget includes sources, transitions, and sinks for photosynthetically available radiation (PAR). The attentuation of PAR is partitioned into separate components and the loss caused by each component is estimated as a function of depth in the upper 100 m. The major sources of attenuation to PAR include seawater (35–76%), total particulate material (20–65%), and dissolved organic material (0–13%). The total particulate material attentuation could be partitioned into attenuation of phytoplankton (12–39%) and of detrital material (8–27%). Although the greatest fraction of photons is absorbed by water, all the variability within the budget is caused by biological processes. Source terms include bioluminescence and chlorophyll a fluorescence, which are orders of magnitude less than radiant energy attenuation, but they are detectable and biologically significant. This photon budget is an estimate, on a quantum basis, of how radiant energy is absorbed and how various fractions are converted to chemical energy or lost to nonphotosynthetic processes. The budget serves to focus on sources, transitions, and sinks of photons and elucidate the mechanisms linking biological processes and ocean optical properties; to identify the major absorbers in the ocean and quantify their relative influence; to demonstrate an accounting with respect to the penetration of radiant energy into natural waters and point to major assumptions and uncertainties in our current estimate; and to establish a perspective that can serve as a basis for the predictive linkage of optical variability and bioluminescence.
Microphotometric characterization of phytoplankton and detrital absorption properties in the Sargasso Sea
Authors: Iturriaga Rodolfo , Siegel David A.
Published: April 2010

Microphotometric techniques were used to characterize the spectral absorption properties of individual phytoplankton cells and detrital particles from two sites in the Sargasso Sea during spring 1985. Direct determinations of the absorption efficiency factor, Qa(λ), geometric cross‐sectional area, G, and particle type were made for about 50 individual particles for each water sample analyzed. Large intrasample and intersample variations of Qa(λ) spectra for both phytoplankton and detrital particles were observed. For the mesotrophic northern station, mean values of Qa(λ) and G for phytoplankton cells showed insignificant vertical variations. For detrital particles, however, the mean geometric cross‐sectional area decreased with depth while their mean Qa(λ) values increased. For the oligotrophic southern station these same relationships were observed, although more small‐scale variability was apparent.

The statistical comparison of the mean Qa(λ) values with the total particulate absorption coefficient spectrum, ap(λ), enabled quantification of the contributions phytoplankton and detrital materials made to ap(λ). Results showed that phytoplankton abundances accounted for ∼50–70% of the particulate absorption at 440 nm, although instances were observed where phytoplankton cells accounted for >90% of ap(440 nm). The reconstructed particulate absorption spectrum, âp(λ), compared favorably with the total ap(λ) indicating that nearly all of the optically relevant absorbing particulate material was sampled with the microphotometric technique.
Chlorophyll fluorescence from single cells: Interpretation of flow cytometric signals
Authors: Sosik Heidi M. , Chisholm Sallie W. , Olson Robert J.
Published: April 2010

The relationship between flow cytometric fluorescence signals and photosynthetic pigments was investigated in three species of marine eucaryotic phytoplankton, Thalassiosira weissflogii, Hymenomonas carterae, and Amphidinium carteri. The species were grown over a range of light intensities to provide a spectrum of pigment compositions for the study. Both interspecific and intraspecific differences were observed. Variations among the species in fluorescence per unit of chlorophyll a (Chl a) could be explained by differences in the relative abundance of Chl a and accessory pigments. Amphidinium carteri had much greater fluorescence per unit of Chl a than the other two species and it had the highest Chi c:Chl a ratio. Fluorescence per unit of Chl a decreased as Chl a per cell increased in H. carterae and A. carteri, whereas it remained the same in T. weissflogii. We interpret these differences to have their origins in the “package” effect on light absorption. This effect seems to be least evident in the diatom because cell size increased as Chl a per cell increased in low‐light‐grown cells. In H. carterae and A. carteri the opposite was true, such that the intracellular concentration of Chl a increased substantially in the low‐light cells. Based on these data, we find that to interpret fluorescence signals among species, differences in the relative abundances of Chl a and accessory pigments must be considered, while for intraspecific fluorescence differences, the package effect may be more important.
Molybdenum and sulfate as controls on the abundance of nitrogen‐fixing cyanobacteria in saline lakes in Alberta
Authors: Marino Roxanne , Howarth Robert W. , Shamess Jennifer , Prepas Ellie
Published: April 2010

We studied 13 saline lakes in Alberta to test the hypothesis that molybdenum availability influences the abundance of planktonic, N‐fixing cyanobacteria in saline ecosystems. Our earlier work in oxic seawater showed that the availability of Mo is controlled in part by the ratio of sulfate to molybdenum because sulfate inhibits the assimilation of molybdate. The SO42−: Mo ratio in seawater is very high relative to most freshwater lakes—a finding that is consistent with the scarcity of planktonic, N‐fixing cyanobacteria in coastal marine ecosystems. This ratio is constant in seawater, however, limiting a test of our hypothesis in marine systems. These Alberta salt lakes provide a more robust test in saline systems.

The ratio of sulfate to molybdenum within any given saline lake was relatively constant over a summer season, but the ratio between lakes varied and ranged from values typical of freshwater lakes to values higher than in seawater. N‐fixing cyanobacteria are significant fractions of the plankton in six of the 13 lakes we studied and are rare or absent in the others. The SO42−: Mo ratio was a strong predictor of the abundance of planktonic, N‐fixing cyanobacteria. Sulfate or Mo concentrations alone, however, were not. This finding is consistent with our hypothesis that sulfate can control Mo availability in oxic waters.

Phosphorus concentrations, and the ratio of N to P, were not good predictors of the abundance of N‐fixing cyanobacteria in these saline lakes, as they often are in freshwater lakes. The differences between predictions from a freshwater, P regression model and actual abundances of N‐fixing cyanobacteria in the saline lakes were best explained by the SO42−: Mo ratio.
Amino acid utilization by marine phytoplankton: A novel mechanism
Authors: Palenik B. , Morel F.M.M
Published: April 2010

An enzyme on the cell surface of some marine phytoplankton, particularly the genus Pleurochrysis (Hymenomonas), oxidizes many l‐amino acids to produce H2O2, NH3 and an α‐keto acid extracellularly. The NH4+ is subsequently taken up and used for growth. The enzyme synthesized by Pleurochrysis carterae (clone CoccoII) has a half‐saturation constant of 0.25 µM assayed with l‐α‐aminobutyric acid as a model substrate. The enzyme activity is absent in NH4+‐grown (logarithmic phase) cells, is present in NO3‐grown (logarithmic phase) cells, and is enhanced 3.5‐fold in N‐limited cells. Some Pleurochrysis species show different patterns of regulation. The existence of this novel, high‐affinity mechanism for amino acid utilization—one that would not be detected by typical field methods—suggests that amino acids may be a more important source of N for phytoplankton than is currently believed.
Estimation of ammonification and ammonium assimilation in surficial coastal and estuarine sediments
Authors: Sumi Takayuki , Koike Isao
Published: April 2010

Ammonification and NH4+ assimilation in slurries of surface sediments from Japanese coastal and estuarine areas were studied with 15NH4+ tracers. In completely aerobic sediments, where NO3− reduction is negligible, the Blackburn 15NH4+ dilution model can be applied to estimate the ammonification rate after a correction for nitrification is made. In semiaerobic sediments, where significant NO3− reduction occurs, a mathematical model based on the change of 15NH4+ and 15NO3− with time was successfully applied to estimate the ammonification rate. The rate of NH4+ assimilation can be obtained directly from the incorporation of 15NH4+ into particles in the sediments after correcting for 15NH4+ dilution during incubation.

The rate of ammonification ranged from 5.8 to 220 ng‐atoms N (g sediment)−1 h−1 and that of NH,,’ assimilation ranged from 6.2 to 114, indicating both large seasonal and local variations. We found, however, that both NH4+ assimilation and ammonification were significantly correlated with ATP biomass, NH4+, and organic N contents in sediments. Several lines of evidence also suggested that NH4+ assimilation is primarily an aerobic microbial process.
Lead in marine planktonic organisms and pelagic food webs
Authors: Michaels Anthony F. , Flegal A. Russell
Published: April 2010

The bioaccumulation of lead in biological ecosystems traditionally has been interpreted in terms of the atomic ratio of Pb to Ca. In marine planktonic ecosystems, however, most of the particulate Ca is skeletal and its amount variable among taxa. The Pb in plankton can be partitioned between skeletal and nonskeletal components. In planktonic samples collected in the equatorial Pacific Ocean, <0.5% of the Pb was associated with CaCO3 (primarily foraminiferan, coccolithophorid, and pteropod skeletons), while up to 54% of the Pb in these samples may have been associated with the SrSO4 skeletons and protoplasm of Acantharia. Atomic ratios of Pb to Ca were highly variable, principally because of the varying amounts of CaCO3 in the samples. Therefore, normalizing Pb concentrations to biomass rather than Ca is preferable for interpreting the bioactivity of Pb in planktonic food webs. We develop a simple model based on the ratio of surface area to volume of organisms to make predictions about the relative importance of organism size and food‐web interactions in the transfer of Pb between trophic levels. For small organisms (<270‐µm spherical radius or the equivalent surface: volume ratio), Pb concentration is determined almost entirely by surface area. For larger organisms, total body Pb will be a function of both the size of the prey and the distribution of Pb within tissues. The role of food‐web interactions (e.g. grazing) in determining the amount of Pb in plankton of different sizes will only be important for large plankton and nekton, where very little of it is adsorbed on the animal surface.
Microbial biomass in the coastal plume of Chesapeake Bay: Phytoplankton‐bacterioplankton relationships
Authors: Malone Thomas C. , Ducklow Hugh W.
Published: April 2010

Turnover rate of suspended organic matter (POC) increased seasonally with temperature as the proportions of POC accounted for by bacterioplankton increased relative to phytoplankton. The proportion of phytoplankton productivity that cycled through bacterioplankton averaged 13% and showed little seasonal variability. These results imply changes in the pathways and rates by which phytoplankton and bacterioplankton production were consumed or exported from the plume.

Time series of 1–3 d next to surface drifters within the plume provided some insight into the nature of these changes. In February when the turnover rate of POC was low, phytoplankton biomass declined relative to bacterioplankton due to sedimentation of large diatoms. Low bacterioplankton biomass was associated with high rates of predation by heterotrophic microflagellates. In August when POC was turning over rapidly, phytoplankton biomass declined relative to bacterioplankton due to selective grazing by copepods. High bacterioplankton biomass appeared to be a consequence of enhanced DOC flux associated with high copepod grazing and POC turnover rates as well as with low predation by heterotrophic microflagellates.
Diel cycles in microbial manganese oxidation and manganese redox speciation in coastal waters of the Bahama Islands
Authors: Sunda William G. , Huntsman Susan A.
Published: April 2010

We observed pronounced diel cycles in formation rates of particulate Mn in coastal waters of the Bahama Islands. Specific rates during the day were 1/20th–1/70th of maximum nighttime rates and there was an associated 3–5‐fold decrease in the ratio of particulate to dissolved Mn during the day. The strong suppression of rates after sunrise probably results from photoinhibition of microbially catalyzed Mn(II) oxidation. The decrease in Mn(II) oxidation during the day along with photodissolution of Mn oxides observed in previous investigations appear to contribute to the increased ratio of dissolved Mn to particulate Mn oxides during daylight.
Growth and voltinism of lotic midge larvae: Patterns across an Appalachian Mountain basin
Authors: Huryn Alexander D.
Published: April 2010

The influence of thermal regime upon community‐level growth rates and voltinism was estimated for larval Chironomidae inhabiting litter accumulations in four streams located in an Appalachian Mountain basin. Groups of larvae were confined in growth chambers and incubated in situ at time intervals representing the observed range of annual thermal variation. Estimates of daily growth rates (g) were derived from change in average length over the incubation period. Using multiple regression, I found temperature and larval size to have significant positive and negative effects on g, respectively. Equations derived for each stream described a substantial proportion of the variance among observed g values (R2 = 0.71–0.82) but did not differ significantly. Therefore, the data from all streams were combined to derive a single general equation which, along with larval size distribution, biomass, and temperature data, was used to model the variation in annual biomass turnover (G) and hypothetical size‐dependent voltinism among the study streams. Size distribution of larvae did not differ significantly among streams and variation in G (range = 12.8–18.6) was attributed primarily to variation in thermal regime. Differences in voltinism were predicted to be minor but were closely dependent on both terminal size of larvae and thermal regime. The model provides evidence that spatial variation of G on the order of 31% can be expected for midge communities within a <30 km2 area of this Appalachian Mountain basin.
Biogeochemistry of carbon in the Amazon River
Authors: Richey Jeffrey E. , Hedges John I. , Devol Allan H. , Quay Paul D. , Victoria Reynaldo , Martinelli Luiz , Forsberg Bruce R.
Published: April 2010

Depth‐integrated, discharge‐weighted water samples were collected over 1,800 km of the Amazon River on eight cruises at different stages of the hydrograph, 1982–1984. Fine (FPOC, <63 µm) and coarse (CPOC, >63 µm) particulate organic carbon as weight percentage of suspended sediment varied between 0.9–1.5% for FPOC and 0.5–3.4% for CPOC. Concentrations of FPOC ranged from 5 mg liter−1 upriver to 2 mg liter−1 downriver in the mainstem and from 6 mg liter−1 in the Rio Madeira to <1 in the Rio Negro. CPOC had similar distribution patterns, but with concentrations 15–30% those of FPOC. Dissolved organic carbon (DOC) averaged 4–6 mg liter−1 in the mainstem and up to 12 mg liter−1 in the Rio Negro. Upriver dissolved inorganic carbon (DIC) concentrations of about 1,200 µM were diluted by tributaries and floodplain drainage to 600 µM at the most downriver site. Evasion of CO2, invasion of O2, and in situ oxidation were of comparable magnitude, 3–8 µmol m−2 s−1.

The average export of total organic carbon (TOC) was 36.1 Tg yr−1 (8.5 g m−2 yr−1), of which 62% was DOC, 34% was FPOC, and 4% was CPOC. TOC inputs were insufficient to support in situ oxidation by a factor of at least two. A relatively small, rapidly cycling pool of labile organic matter may coexist with a much larger pool of more refractory material.
Fluxes and transformations of aquatic pigments in Lake Mendota, Wisconsin
Authors: Hurley James P. , Armstrong David E.
Published: April 2010

Concentrations and fluxes of chlorophyll and carotenoid pigments were measured in suspended and settling particulate matter and in surface sediments in Lake Mendota. Flux comparisons were used to calculate the extent of alteration or degradation within the water column and at the sediment surface. Losses within the water column for specific time intervals ranged from almost negligible for diatoxanthin to 96% for peridinin. The extent of loss was influenced by pigment type and transport process.

Surface sediment diagenesis in Lake Mendota resulted in differential degradation rates among chlorophyll and carotenoid constituents. Deposition of pheophorbide a—a grazing indicator—was most important during late spring, as zooplankton populations increased and chlorophyll levels in the water column dropped below 1 nmol liter−1. The ability to trace the magnitude of this annual event through the sedimentary record was obscured by selective degradation of pheophorbide relative to chlorophyll and pheophytin. Similarly, carotenoid composition was dramatically altered both within the water column and at the sediment surface. Fucoxanthin and peridinin, major water‐column carotenoids, were degraded extensively before incorporation in the sediments.
Mechanism for the hydrogen sulfide‐induced growth limitation in wetland macrophytes
Authors: Koch Marguerite S. , Mendelssohn Irving A. , McKee Karen L.
Published: April 2010

Hydrogen sulfide, a phytotoxin that often accumulates in anoxic marine and freshwater marsh soils, suppressed the activity of alcohol dehydrogenase (ADH), the enzyme that catalyzes the terminal step in alcoholic fermentation, in the roots of two wetland macrophytes. This inhibition of root ADH activity with increasing sulfide concentration was associated with decreases in root total adenine nucleotide pool (ATP + ADP + AMP), the adenylate energy charge ratio (AEC), nitrogen uptake (percent recovery of 15NH4+‐N) and growth (leaf elongation). These responses were species‐specific with a greater negative impact in the freshwater marsh species that naturally inhabits low‐sulfide environments. These findings lend support to the hypotheses that ADH activity, as a measure of fermentative metabolism, is important in maintaining the root energy status of wetland plants under hypoxic‐anoxic conditions, that there is a significant negative effect of H2S on the anoxic production of energy in these roots, and that an important negative effect of H2S on plant growth is an inhibition of the energy‐dependent process of N uptake.
Recruitment of encrusting benthic invertebrates in boundary‐layer flows: A deep‐water experiment on Cross Seamount
Authors: Mullineaux Lauren S. , Butman Cheryl Ann
Published: April 2010

A 48‐d field experiment on recruitment of metazoan larvae and other foraminiferal propagules of deep‐water, encrusting invertebrates was conducted on the summit of Cross Seamount (central North Pacific, 410‐m depth). Experimental substrata were circular flat plates with differing thicknesses and surface characteristics, designed so that larval responses to the plate boundary‐layer flow could be evaluated relative to other factors, such as substratum composition and texture. Flume studies indicated that rectangular plates with thin edges (1.5 mm) develop a boundary layer that thickens gradually downstream from the upstream edge, while plates with thick edges (10.0 mm) develop a separation eddy extending 2–3 cm downstream from the leading edge. Dissolution patterns of alabaster disks deployed on Cross Seamount indicated that similar flow patterns developed over plates at the field site. Recruitment of organisms (mostly benthic foraminifers) onto the thin plates was significantly lower very near the edges than near the centers of the plates. Recruits on the thick plates were most abundant 2–3 cm in from the edges of the plates, where the attachment point of the separation eddy was expected to occur most frequently. These results suggest that larval settlement may be a function of very small‐scale variations in the boundary‐layer flow, reflecting, for example, larval supply to the plate, larval retention on the plate surface, and active larval responses to the flow regime over the plates. Several taxa recruited exclusively onto thick plates covered with finely powdered ferromanganese crust, however, suggesting active selection for substratum composition or texture.
Rapid ammonium cycling and concentration‐dependent partitioning of ammonium and phosphate: Implications for carbon transfer in planktonic communities
Authors: Suttle Curtis A. , Fuhrman Jed A. , Capone Douglas G.
Published: April 2010

A short‐lived radioactive isotope of nitrogen (13N, half‐life = 10 min) of very high specific activity (>100 mCi µmol−1) was used to study NH4+ uptake at near‐ambient concentrations in natural planktonic communities. The turnover times of the dissolved NH4+ pool in Long Island Sound ranged from tens of hours between April and early June to a fraction of an hour between mid‐June and late July. The NH4+ turnover time was also rapid in a nearby eutrophic lake. Up to 50% of the ambient NH4+ flux into particulate material from Long Island Sound was attributable to organisms passing 1.0‐µm polycarbonate filters. Partitioning of NH4+ uptake among size classes was, however, very concentration‐dependent. A 0.5 µM addition resulted in an increase in NH4+ uptake by the >3‐µm size class of from 33% to >80% of the total. Similar results were obtained for PO43− uptake into particulate matter from the Sargasso Sea. Although <20% of the ambient PO43− uptake was into particles >1 µm, a 100 nM pulse resulted in about 50% of the uptake entering the >1‐µm fraction. Because slight increases in NH4+ and PO43– concentration result in greater uptake by larger organisms with higher C : N and C : P ratios, distributing these nutrients in “patches” of elevated concentration results in more C being transferred to higher level consumers.
Distribution of labile dissolved organic carbon in Lake Michigan
Authors: Laird Gwenyth A. , Scavia Donald
Published: April 2010

Bioassay‐measured, labile dissolved organic carbon (LDOC) concentrations were compared in near‐bottom and near‐surface Lake Michigan water between April and October 1986. In five of seven experiments, the LDOC concentration was higher in near‐bottom water. LDOC reached 40.2% of the total DOC pool in the near‐bottom water in late May and 13.8% in the near‐surface water in early July. Concentration in near‐bottom water was highest during early stratification; concentration in surface water varied less but was highest in early July. The data suggest that an allochthonous source of labile organic C may be important.
he influence of copepod “swimmers” on pigment fluxes in brine‐filled vs. ambient seawater‐filled sediment traps
Authors: Peterson William , Dam Hans G.
Published: April 2010

We compared pigment fluxes measured by particle traps filled with 60‰ filtered seawater and traps filled with filtered seawater of ambient salinity in central Long Island Sound. Pigment fluxes were significantly higher in the brine‐filled traps. Extremely high numbers of copepods were present in the brine‐filled traps as well, up to 4,000 individuals per 4‐h deployment compared to 150 in the seawater‐filled traps. On average 44% of the copepods in the brine‐filled traps had injuries associated with immersion in a hypertonic solution: in some the ovaries had burst through the thoraxes but in most, the gut protruded outside the body wall (similar to a hernia), suggesting that the stomach contents spilled into the trap water, thus biasing our flux measurements. Flux in the brine‐filled traps was 20– 30% greater than that in the seawater‐filled traps. Spillage of gut contents into the trap sample could explain up to 41% of the excess of pigments found in the brine‐filled traps (mean of 13% over the study period).
The vertical flux of metazoans (holoplankton, meiofauna, and larval invertebrates) due to their association with marine snow
Authors: Shanks Alan L. , Edmondson Elizabeth W.
Published: April 2010

We investigated the association of meiofauna (nematodes and harpactacoid copepods), larval polychaetes, and holoplankton with marine snow. Using a sediment trap equipped with a time‐lapse camera, we measured the vertical flux of these organisms due to their association with marine snow. On average, 83 and 74% of the nematodes and competent larval polychaetes were on marine snow as were only 15 and 9% of the harpacticoid copepods and precompetent larval polychaetes. On average, 94, 80, and 25% of the vertical fluxes of nematodes, competent larval polychaetes, and harpacticoid copepods were due to individuals on marine snow. The vertical flux of precompetent larval polychaetes was negligible. By inhabiting passively sinking aggregates, nematodes and competent larval polychaetes would deposit on the seabed according to the hydrodynamical processes controlling marine snow deposition.

Of the holoplankton (calanoid and cyclopoid copepods, nauplii, and larvaceans), <2% was on marine snow. Vertical fluxes of calanoid copepods and nauplii were negligible. The vertical fluxes of cyclopoid copepods and larvaceans were large, but ony 3% was due to individuals on marine snow.
Relationship between primary and export production in the boreal coastal zone of the North Atlantic
Authors: Wassmann Paul
Published: April 2010

Data from the literature on long‐term, simultaneous measurements of total primary production (PT) and sedimentation of particulate organic C (POC) close to the bottom of the photic zone, i.e. the export production (PE), are compared. Sufficient data are available only from the boreal coastal zone of the North Atlantic. A regression analysis revealed that PE is positively and nonlinearly related to PT and a power model (r2 = 0.94) was chosen. Comparison with published models predicting the vertical flux of POC from the upper water column (bottom of the photic zone or 50‐m depth) revealed that they do not adequately predict PE on the basis of PT in boreal coastal environments. It is suggested that PE in the boreal coastal zone should be calculated with the equation PE = 0.049 PT1.41. The 〈f〉 ratio, i.e. the ratio of PE : PT characterizing lengthy time intervals and the regenerated production (Pr) were calculated. Botht 〈f〉 and Pr are positively, nonlinearly correlated with PT, and the upper limit for 〈f〉 is about 0.5 in boreal coastal environments. Solar radiation at various latitudes influences the relationships among PE, Pr, 〈f〉, and PT.
Oceanic and estuarine ammonium oxidation: Effects of light
Authors: Horrigan S.G. , Springer A.L.
Published: April 2010

We examined the effect of light on the oxidation of NH4+ to NO2 by oceanic and estuarine bacteria. Inhibition of NH4+ oxidation by light was more pronounced in the oceanic isolates. The estuarine bacteria, isolated from Chesapeake Bay, produced NO2− at a rate faster than the oceanic isolates. We conclude that photoinhibition of NH4+ oxidation may be less important in estuarine environments than in oceanic ones.
Algal use of sedimentary phosphorus from an Amazon floodplain lake: Implications for total phosphorus analysis in turbid waters
Authors: Engie Diana L. , Sarnelle Orlando
Published: April 2010

Chemical forms of P and their availabilities to Selenastrum capricornutum were measured in sediments collected from Lago Calado, an Amazon floodplain lake. Postbioassay analysis confirmed that Selenastrum used ∼60– 70% of the P in the NaOH‐extracted fraction during a 9‐d incubation. No evidence for algal use of Ca‐bound P or organic P was found. Methodological comparisons revealed that persulfate digestion may not adequately recover algal‐available particulate P in waters high in inorganic turbidity. An average of 26% of the agal‐available P in Amazon River water was in particulate form.
Aphotic pigment degradation in the hypolimnion: Implications for sedimentation studies and paleolimnology
Authors: Leavitt P.R. , Carpenter S.R.
Published: April 2010

Reversed‐phase high pressure liquid chromatography was used to quantify carotenoid and Chl degradation resulting from bacterial and microfaunal action during aphotic, hypolimnetic incubations of natural phytoplankton assemblages and detrital material in three lakes. Decay of carotenoids (to −0.0870 d−1) and chlorophylls (to −0.1226 d−1was potentially rapid but site‐specific. Chl a decay spanned a wide range (to −0.1226 d−1) with greatest losses in circumneutral, unstained Peter Lake and least in acidic, stained Tuesday Lake. The usefulness of Chl a as an indicator of algal sedimentation was compromised by its rapid degradation, lack of compensatory production of recognizable derivatives, and an abundance of unknown, chlorophyllous compounds. β‐carotene degraded less rapidly and variably (to −0.0167 d−1) and is a useful addition to both sedimentation and paleolimnological studies. Differences among ca rotenoids in decay pose difficulties in reconstructing accurate estimates of former algal community composition, especially dinoflagellates, whose peridinin decays rapidly (−0.0843 d−1). Changes in the relative (within‐core) abundance of individual pigments may be combined, however, with changes in Chl a : β‐carotene ratios to differentiate between periods of enhanced productivity (or pigment preservation) and changes in the vertical zonation of algal communities.
Contribution of organic acids to alkalinity in lakes within the Mount St. Helens blast zone
Authors: Wissmar Robert C. , Mcknight Diane M. , Dahm Clifford N.
Published: April 2010

The volcanic eruption of Mount St. Helens in May 1980 severely affected lakes in the surrounding blast zone. Existing and newly formed lakes had high total alkalinities (TA) and concentrations of dissolved organic carbon (DOC). In Spirit Lake, TA and DOC were 36 and 64 times pre‐eruption values. Dissolved organic acids, primarily ionized fulvic acids and hydrophilic acids, constituted 80–90% of the dissolved organic material. High TA values during 1980 and 1981 included two major components, carbonate (CA) and surplus alkalinity (R−). A comparison of minimal estimates for organic acid alkalinity from ionized fulvic acids (Af) and hydrophilic acids (Ah) with values of R− showed that the dissociation of organic acids contributed between 20 and 100% to R− in 1980 and 1981. During 1981, surplus alkalinity and organic acid alkalinities relative to TA declined while CA increased. This increase in CA reflected the influence of dilution of lake volumes with runoff waters and a major decrease in organic acids due to dilution and microbial mineralization. CA appeared controlled by contributions of bicarbonate ions due to chemical weathering, possible anionic exchange, and microbially mediated reactions. These reactions involving organic acids in combination with the geochemical characteristics of the eruption (e.g. moderate SO42− and Cl concentrations and massive loadings of inorganic and organic materials) led to well‐buffered lakes that had a sizable proportion of the alkalinity being contributed by dissociated organic acids.
Spectral absorption coefficients of living phytoplankton and nonalgal biogenous matter: A comparison between the Peru upwelling areaand the Sargasso Sea
Authors: Bricaud Annick , Stramski Dariusz
Published: April 2010

Absorption coefficients of total particulate (biogenous) matter were determined in the mesotrophic waters of the Peruvian upwelling and the oligotrophic waters of the Sargasso Sea. A method based on spectral criteria was used to partition these coefficients into absorption by living algal cells and by nonalgal (mainly detrital) material. This method was tested by independently measuring absorption by nonalgal material for samples from the Sargasso Sea.

The average Chl‐specific absorption coefficients measured in the Sargasso Sea are significantly higher than in the Peruvian upwelling and also higher in the surface layer than in the deep Chl maximum layer. These systematic variations appear to be mainly due to differences in sizes and intracellular pigment concentrations of the cells, inducing differences in the amplitude of the package effect.
A test of the assumptions and predictions of recent microalgal growth models with the marine phytoplankter Pavlova lutheri
Authors: Chalup Michael S. , Laws Edward A.
Published: April 2010

The marine phytoplankter Pavlova lutheri was grown in both batch and continuous culture under various conditions of light and nitrate limitation in order to examine the accuracy of certain assumptions and predictions of growth models. The N : C ratio cells was found to be uniquely related to their relative growth rate. There was no unique relationship, however, between Chl a : C ratios and relative growth rate. Optical absorption coefficients normalized to Chl a were negatively correlated with relative growth rate at a fixed irradiance and positively correlated with irradiance at a fixed relative growth rate when light intensity was varied with neutral‐density filters. Quantum yields were positively correlated with relative growth rate at a fixed irradiance and negatively correlated with irradiance at a fixed relative growth rate. Certain parameters or combinations of parameters which appear in nutrient‐saturated growth models were found to be either independent of relative growth rate at a fixed irradiance or uniquely correlated with relative growth rate. This discovery facilitates extension of nutrient‐saturated growth models to nutrient‐limited conditions.
A microalgal growth model
Authors: Laws Edward A. , Chalup Michael S.
Published: April 2010

Recent experimental evidence has made it clear that effects of irradiance and nutrient limitation on light absorption and photosynthetic quantum yields of microalgae and the relationship between cellular N: C ratios and nutrient‐limited growth rates are inconsistent with the assumptions and predictions of current models of algal growth. A new algal growth model was therefore developed to overcome these inconsistencies. The new model predicts a hyperbolic relationship between nutrient‐saturated growth rates and irradiance and a linear relationship between growth rate and both respiration rate and Chl a : C ratios. The correlation between growth rate and Chl a : C is positive under nutrient‐limited conditions and negative under nutrient‐saturated (light‐limited) conditions. The requirement that N: C ratios be linearly related to relative growth rates leads to the conclusion that the product of the Chl a‐specific absorption coefficient and the quantum yield coefficient be hyperbolically related to nutrient‐limited growth rates, a result consistent with experimental observations. The equations relating respiration rate and compositional ratios to absolute and relative growth rates appear to be insensitive to photoperiod.
Significance of photosynthetic endosymbionts to the carbon budget of the scyphomedusa Linuche unguiculata
Authors: Kremer Patricia , Costello John , Kremer James , Canino Michael
Published: April 2010

Symbiotic dinoflagellates (zooxanthellae) associated with the medusa of Linuche unguiculata constituted 22–26% of the total C and N biomass. The maximal net production for intact medusae (Pm) averaged 4.5 mg O2 (mg Chl a)−1 h−1, equivalent to an assimilation number of 2.0 mg C (mg Chl a)−1 h−1. At the midday maximum, gross oxygen production averaged four times the respiration rate. The saturating light intensity was 200–300 µEinst m−2 s−1 (Einstein = mol quanta) and the compensation light intensity (dO2 = 0) was ∼20 µEinst mn−2 s−1. On a diel basis Pgrow : R averaged 1.7 for intact medusae at ambient near‐surface light. Diel periodicity with a midday maximum was measured for the production potential under artificial, saturating light. Both intact medusae and freshly isolated zooxanthellae demonstrated similar diel production patterns. Respiration did not show the same strong diel pattern as net production, but respiration declined steadily when medusae were held unfed in the dark. Respiration was independent of the ambient oxygen concentration over a range from 4 to 16 mg O2 liter−1. Diel periodicity was measured in egg release and division rates of zooxanthellae. Estimates of both algal and host growth ranged from 0.01 to 0.04 d−1. Calculations indicated that only 21% of the C fixed in photosynthesis was used in algal respiration and growth. If the remaining photosynthate were translocated, it could provide all the C required for host respiration and somatic growth. Egg production represented another large C flux in adult females, with a daily release equivalent to 4–8% of host body C for medusae of 0.2–1.2 ml in displacement volume.
Bacterial mediation in the utilization of carbon and nitrogen from detrital complexes by Crassostrea virginica
Authors: Crosby Michael P. , Newell Roger I. E. , Langdon Christopher J.
Published: April 2010

Unattached, cellulolytic bacteria isolated from a salt marsh were cultured on [15N]ammonium sulfate and [14C]glucose and fed to the American oyster Crassostrea virginica. Oysters were able to digest and assimilate bacterial C with an assimilation efficiency of 52.5%. We estimate that free‐living bacteria may be capable of supplying up to ∼9.5% of the total C requirements of oysters in their natural habitat. Cellulolytic bacteria were also cultured on 14C‐labeled refractory Spartina alterniflora particles as the sole C source and [15N]ammonium sulfate as a source of N. These labeled bacteria, together with the S. alterniflora, were fed to the oysters. The refractory C from these detrital complexes was assimilated by the oysters with an efficiency of 10.3%. It was (P= 0.0007) greater than the assimilation efficiency of 2.7% measured in a previous study for oysters feeding on the refractory S. alterniflora substrate alone. This result provides direct experimental evidence that cellulolytic bacteria in the environment can contribute to the transfer of C from refractory detritus to an ecologically important suspension‐feeding macroinvertebrate. We calculated that C. virginica, when fed detrital complexes, assimilated bacterial N with an efficiency of 57.2% but that assimilation of total N present in the detrital complexes was only 3.4%. We speculate that this low assimilation efficiency was due to most (94%) of the N being in the form of condensation products such as humic geopolymers and extracellular polymeric substances secreted by bacteria which could not be digested and absorbed by the oysters. Calculations show that detrital complexes in the natural environment may provide a significant contribution to an oyster’s C demand. The magnitude of this contribution can increase from 1.3 to 60% as both absolute bacterial abundance and proportion of bacteria attached to detrital particles increase, raising the oysters’ efficiency of filtration for these substrates.