bluuebunny/crossref_metadata_2025 huggingface dataset:
Flow cytometry for observing the distribution of adsorption sites on particles
Authors: Baier Rodger W. , Cucci Terry L. , Yentsch Clarice M.
Published: April 2010

Flow cytometry was found to be useful for describing the distribution of adsorption sites for yellow substance on mineral particles. Fewer than 0.1% of the particles measured in clay samples adsorbed enough fluorescing sorbate at 80 mg liter−1 to be detected with 150 mW of JV excitation energy. All of the particles would have been observed if the coverage had been uniform. Gravimetric measurements made on subsamples showed that clay components adsorb up to 2% of their weight of carbon as organic compounds and could provide a significant sink for the fluorescent products of decomposed vegetation.
Historical development and use of thousand‐year‐old tide‐prediction tables
Authors: Zuosheng Yang , Emery K. O. , Yuix Xui
Published: April 2010

Tide‐prediction tables require an understanding of the relation of tide to moon and sun, as expressed by correspondence of tide heights to phases of the moon and by the lag of high tide after local meridional transit of the moon. Such tables were compiled earlier in China than elsewhere‐more to satisfy the interests of sightseers of spectacular river bores than for convenience of shipping. We used the earliest extant Chinese tables of a.d. 1056 to compare ancient predictions with those from modern tide tables for the Qiantang river bore near Hangzhou. The fit of hour and height is excellent for the 10 d or so of highest (perigean) tides, but the ancient tables do not select the higher of the two daily apogean high tides during much of the rest of a month.
Extracellular proteolytic enzyme activity in sediments of an intertidal mudflat
Authors: Mayer Lawrence M.
Published: April 2010

Extracellular proteolytic activity (EPA) on an intertidal mudflat was examined over a 2‐yr period, with focus on characteristics of enzyme systems and the controlling influences on enzyme activity levels. EPA was primarily associated with the particulate rather than the pore‐water phase. Inhibitor studies indicated the presence of primarily metallo‐ and thiol proteases, with pH optima in the range 8–9.5. Temperature optima increased with depth in the sediment, being in the 20°–35°C range for surficial sediments and the 40°–50°C range in the subsurface. Activation energies at environmental temperatures were in the 63–67 kJ mol−1 range. The hypothesis of progressive humification of enzyme activity with depth was discarded on the basis of results from thermal denaturation experiments. EPA levels decreased with depth and hence correlated with substrate concentration and bacterial populations, but this correlation was not a tight one. Seasonal variations in EPA varied with the temperature cycle consistent with, though somewhat damped relative to, the temperature dependence of the enzymes themselves and showed no response to variations in substrate concentrations or bacterial numbers.
Feeding depths and organic absorption for the deposit feeding benthic amphipods Pontoporera affinis and Pontoporeia femorata
Authors: Lopez Glenn , Elmgren Ragnar
Published: April 2010

Using fluorescent particles as sediment markers, we show that the congeneric, deposit‐feeding amphipods Pontoporeia affinis and Pontoporeia femorata feed almost exclusively on the surface layer (upper centimeter) of sediment, even though they may spend much of their time deeper. Pontoporeia affinis feeds more rapidly than P. femorata. There was some evidence that food intake decreased at night for P. affinis, but not for P. femorata.

The two species were equally good at absorbing sedimentary organic carbon, both absorbing ~ 40% from surficial and 28% from deeper sediment. Neither species was very selective in ingesting the organic fraction of sediment.

Pontoporeia femorata resides deeper in the sediment than its morphologically similar congener P. affinis, and this difference is enhanced in sympatric populations. Yet, there is no evidence of food partitioning between the two species. An innate tendency of P. affinis to move up, and P. femorata down, upon disturbance from burrowing activities of neighbors may be the primary cause of the enhanced vertical stratification in sympatric populations. It may result in differential susceptibility to predation. In addition, P. affinis swims more actively than P. femorata and should more easily find new patches of high‐quality, surficial sediment. Thus predation and microhabitat partitioning may contribute to the coexistence commonly observed in the two species, in spite of suspected exploitative food competition.
Interactions between Chironomus plumosus (L.) and the microbial community in surficial sediments of a shallow, eutrophic lake
Authors: K. Johnson Richard , Boström Bengt , van de Bund Wouter
Published: April 2010

Feeding by Chironomus plumosus (L.) larvae on sedimentary microbiota was studied in eutrophic Vallentunasjön, where microbial biomass constitutes a large portion of sedimentary organic matter. The life history of C. plumosus consisted of two univoltine cohorts with an overall production of 1.4 g ash‐free dry wt m−2. Gut concentrations of bacteria, Microcystis, and Melosira were several times higher than sedimentary concentrations, indicating that the larvae are foraging selectively. Assimilation of bacteria and newly sedimented Melosira cells on average accounted for 11 and 49% of the estimated carbon requirement (production + respiration) of the larvae. Digestive efficiencies for bacteria and Melosira seasonally averaged 43 and 34%. “Overwintering” Microcystis colonies, which constitute the dominant proportion of microbial biomass in the sediments, were used to a small extent ifat all as a carbon source by the chironomids. Ifa decrease in autofluorescence intensity of cells during gut passage is indicative of partial digestion of the cells, Microcystis was used with a digestive efficiency of 9% and accounted for ~ 10% of the carbon requirements of the larvae. On the basis of ambient Chironomus densities, gut passage time, enrichment factor (gut vs. sedimentary density of bacteria), and digestive efficiency, chironomid grazing is not a dominant sink for sedimentary bacteria in Vallentunasjön. The feeding activity of Chironomus larvae decreased bacterial densities but increased the cell‐specific production in laboratory experiments. The decrease was not proportional to grazer density, indicating that indirect effects of the chironomids (on sedimentary structure and chemistry) also affect the abundance of bacteria.
Nitrification‐denitrification at the plant root‐sediment interface in wetlands
Authors: Reddy K. R. , Patrick W. H. , Lindau C. W.
Published: April 2010

Oxygen transport through the air spaces (aerenchyma tissue) of the stem and roots of aquatic macrophytes into the root zone supports nitrification of NH4+, with the NO3− formed diffusing into the adjacent anaerobic zone where it undergoes denitrification. To test this hypothesis, we conducted a growth chamber study to determine the transformation of applied15NH4+‐N to 15N2 in the root zone of three aquatic macrophytes: rice (Oryza sativa L.), pickerel weed (Pontederia cordata L.), and soft rush (Juncus effusus L.). Detection of gaseous 15N2 in the air above the floodwater of the soil column with aquatic plants provided direct evidence of nitrification‐denitrification in the root zone, while such losses were not measurable for soil columns without plants. Air spaces in aquatic plants can also function as conduits for denitrified gases from anaerobic sediments to the atmosphere. Maximal 15N2 flux due to this process was 102, 113, and 122 mg N m−2 d−1 for soft rush, rice, and pickerel weed. This N loss mechanism has important agronomic and ecological consequences.
Formation and bacterial utilization of dissolved organic carbon derived from detrital lignocellulose
Authors: Moran Mary Ann , Hodson Robert E.
Published: April 2010

In various wetland ecosystems, lignocellulose from aquatic vascular plants is the most abundant reservoir of organic material. During microbial degradation of lignocellulose, soluble decomposition products are released into the environment. The importance of lignocellulose‐derived dissolved organic carbon (LC‐DOC) to ecological and geochemical processes depends on the rate of formation of these compounds and their subsequent fates. In laboratory microcosms, rates of formation of LC‐DOC from the salt marsh plant Spartina alterniflora varied from 0.7 to 1.0% of particulate lignocellulose per day and decreased as decomposition progressed. Rates of bacterial utilization of LC‐DOC for pools formed at 1, 2, 7, and 13 weeks into decomposition indicated that soluble intermediates produced throughout the first 3 months of lignocellulose degradation, although gradually decreasing in amount, were of similar composition. Bacterial mineralization of each pool was initially very rapid (12% in 16 h), indicating the presence of labile compounds in LC‐DOC. Rates slowed after the first day, however, resulting in mineralization of 30% of the original pool after 30 d. LC‐DOC formation and its subsequent bacterial utilization were also documented for the dominant vascular plant in two other aquatic ecosystems—a freshwater swamp and a mangrove swamp. Up to 40% of total lignocellulose mineralization in these marine and freshwater systems can be traced to use of LC‐DOC by both free‐living and attached bacteria. However, some components of LC‐DOC, presumably those compounds recalcitrant to microbial action, accumulated during lignocellulose decomposition. This unused LC‐DOC may play a role in the formation of humic substances in wetland environments or other aquatic ecosystems with substantial inputs of vascular plant detritus.
Changes in phytoplankton and zooplankton biomass and composition reflected by sedimentation
Authors: Bloesch Jürg , Bürgi Hans‐Rudolf
Published: April 2010

Eight 2‐week limnocorral (LC) experiments were performed in Lake Lucerne, Switzerland, during 1982–1984 to study the effects of biomanipulation. The large zooplankton were removed by 95‐µm plankton nets in some LCs and different phosphorus fertilization regimes were applied. The chlorophyll a and sestonic POC and PP concentrations decreased significantly in the presence of crustacean zooplankton, whereas algal biomass was less affected. Within the short period of 2 weeks this “top‐down” regulation seemed to be balanced by “bottom‐up” control, because phosphate fertilization and favorable light conditions stimulated phytoplankton production and increased seston concentrations. The significant shift from nanoplankton to net plankton in both the filtered and control LCs, which caused the sedimentation rates to increase during all the experiments, could not be attributed solely to selective zooplankton grazing but was also induced by different algal nutrient strategies. In the control (unfiltered) LCs, the herbivorous crustaceans (usually >80% Daphnia spp.) increased POC and PP sedimentation by 14–50 and 25–57% due to fecal pellet production.
Copepod diel migration, feeding, and the vertical flux of pheopigments.
Authors: Dagg M. J. , Frost B. W. , Walser W. E.
Published: April 2010

Feeding and diel vertical migration in the copepods Calanus pacificus Brodsky and Metridia lucens Boeck were examined during dusk and dawn in Dabob Bay, Washington. Both species migrated from below 75 m during the day into the upper 25 m at night. Feeding on phytoplankton was confined to periods spent in the surface layer.

Metridia lucens arrived in the surface 0.5 h after sunset, fed at high rates throughout the night until 1.0 h before sunrise, and then returned to depth. In contrast, C. pacificus appeared in the surface layer 0.5–1.5 h before sunset but fed at low rates until ~1 h after sunset, then increased its feeding rate. Feeding decreased before sunrise, although migratory descent was not completed until after sunrise. These patterns are not in agreement with models of diel migration that predict the onset of feeding 1–2 h before sunset.

During the night in surface waters, these copepods defecated 2.3–2.9 mg pigment m−2. In comparison, active transport of pigment to deep waters via migratory descent was only 0.01–0.02 mg pigment m−2 d−1.
The effect of Daphnia body size on filtering rate inhibition in the presence of a filamentous cyanobacterium.
Authors: Peter Hawkins , Lampert Winfried
Published: April 2010

We tested the hypothesis that shifts in the size structure of daphnid assemblages may be caused by differing sensitivities of particular species to interfering filamentous cyanobacteria. Three Daphnia species of different size were fed the green alga Scenedesmus and filtering rates were measured in the presence and absence of straight filaments of the cyanobacterium Cylindrospermopsis raciborskii. Cylindrospermopsis was not lethally toxic to Daphnia, but was inadequate as the sole food. The filtering rates of all three Daphnia species were reduced in the presence of the filaments. The larger Daphnia pulicaria and Daphnia hyalina were more affected than the smallest, Daphnia cucullata, and within the size range of each species larger individuals were more affected than smaller ones. Our results are consistent with field observations that body size is an important factor determining the competitive success of Daphnia species in the presence of cyanobacterial filaments.
Microhabitats of ciliates: Specific adaptations to different substrates
Authors: Nicola Ricci
Published: April 2010

Several traits of the biology of the ciliate hypotrichs Oxytricha bifaria and Euplotes crassus suggested that, although they share a clear‐cut thigmotactism, they could be expected to differ in some respects from each other as to microhabitat. A bidimensional flat substrate (such as that represented by sunken leaves and stems) was considered suitable for the former species, while a tridimensionally articulated one (such as the network of tunnels between grains of sand) was expected to be the preferred substrate for the latter. Single and paired specimens of these species were tested separately, in order to observe their distribution when flat and sandy substrates (with different granulometry, for different tests) were made available contemporaneously. The results showed that the working hypothesis holds perfectly for the species considered. Thus, for the first time it was demonstrated that two species, both well known for their thigmotactism and therefore believed to be very similar to each other in their “life styles,” are actually adapted to different microhabitats defined by their dimensionalities.
The influence of growth conditions on the size dependence of maximal algal density and biomass
Authors: Agusti Susana , Kalff Jacob
Published: April 2010

The maximal density achieved by 11 freshwater microalgae (mostly Chlorophyta) with a wide range in cell size, grown under standardized conditions, varied as the −0.79 power of their cell volume. The proximity of this exponent to 0.75 (¾ rule) and the fact that the relationship was not significatively altered by light limitation (11 µEinst m−2 s−1) suggest that physiological constraints, and not self‐shading as proposed in the past, should be responsible for the existence of the size‐dependent maximum density. The results also demonstrate a positive relationship between cell size and maximal biomass that is in agreement with previous field observations.
The distribution of benthic Foraminifera with respect to oxygen concentration and organic carbon levels in shallow‐water Antarctic sediments
Authors: Bernhard Joan M.
Published: April 2010

The vertical distribution of living benthic Foraminifera from 12 sediment cores (12.2–18.3‐m water depth) collected in Explorers Cove and Winter Quarter’s Bay, McMurdo Sound, Antarctica, was determined and compared with pore‐water oxygen, sedimentary organic carbon, and grain size. Oxygen measurements were made with microelectrodes to depths greater than the anoxic‐oxic interface (0.1 ml O2 liter−1; 4.4 µM O2 kg−1). Sedimentary organic carbon contents were low (0.1–0.5% dry wt). Maximal standing stocks, as determined by adenosine triphosphate (ATP) assay, occurred in the top 0.5 cm of all cores. No distinct segregation in species occurrence with respect to depth in the sediment was observed. Individuals of both calcareous and arenaceous species (Cassidulinoides porrectus, Cribrostomoides jeffreysii, Globocassidulina cf. G. biora, Portatrochammina antarctica, Psammosphaera parva) were found living in anoxic sediment layers. Relative to ATP, Rose Bengal staining grossly overestimated and Sudan Black B underestimated living standing stocks.
Respiratory losses in the light in a marine diatom: Measurements by short‐term mass spectrometry
Authors: Weger Harold G. , Herzig Ronny , Falkowski Paul G. , Turpin1 David H.
Published: April 2010

Mass spectrometric analysis of gas exchange by the diatom Thalassiosira weisflogii grown under 12 : 12 L/D cycles indicates that mitochondrial respiration is highest in the light, averaging 54 µmol O2(mg Chl a)−1 h−1 while gross photosynthesis was 162 µmol O2(mg Chl a)−1 h−1. In the dark, mitochondrial O2 consumption slowly decreased to a minimum of 29 µmol(mg Chl a)−1 h−1 at the end of scotophase. When cells were poised at the DIC (dissolved inorganic carbon) compensation point in the light (DIC concentration where net photosynthesis equals zero), mitochondrial O2 consumption was only slightly higher than in the dark. Adding DIC to cells at the compensation point resulted in a rapid increase in both photosynthetic O2 evolution and mitochondrial O2 consumption, indicating that the higher mitochondrial respiration rates observed in the light are probably due to an increase in substrate supply from photosynthesis. If estimates of primary production are based on oxygen exchange, this effect is accounted for; however if radiocarbon is used to measure production, especially in short‐term measurements, net production may be significantly overestimated.
Nutrient status and nutrient competition of phytoplankton in a shallow, hypertrophic lake
Authors: Sommer Ulrich
Published: April 2010

The nutritional status of phytoplankton in a shallow, hypertrophic lake was analyzed by stoichiometry of seston and by enrichment bioassays during a 6‐month period. Both methods suggested moderate and temporally interrupted nutrient limitation of reproductive rates. Nitrogen was the most frequently limiting nutrient, phosphorus was next, and silicate limitation of three diatom species occurred only once. The nutritional status of the most abundant individual species could be described by the Monod equation. The nutritional status of the entire phytoplankton assemblage could be described by a modified version of the Droop equation. In accordance with competition theory, phytoplankton species were arrayed along resource ratio gradients. These results are consistent with ecophysiological models derived from culture experiments.
A time‐series study of the vertical structure of nitrogen and particle dynamics in the Sargasso Sea
Authors: Altabet Mark A.
Published: April 2010

A time‐series study of nitrogen and particle dynamics at a site near Bermuda was made with natural nitrogen isotopic ratios as an in situ tracer. Vertical structure in δ15N values and other quantities varied both seasonally and interannually. At times during stratification, weak to moderate minima in δ15N and maxima in suspended particulate nitrogen concentration (PN) were observed in association with the top of the nitracline at the base of the euphotic zone indicative of local NO3− utilization. Net transport of PN as sinking particles enriched in15N to the lower half of the euphotic zone, however, acted to weaken or erase these features. A return flux of nitrogen from the lower to upper half of the euphotic zone was required, on a 1–3‐week time scale, to prevent depletion of suspended PN in the upper 50 m. Persistently higher particle flux at 50 vs. 100 m contrasts with the findings of the VERTEX study for the NE Pacific; the upper half of the euphotic zone in the Sargasso Sea appeared to be substantially less efficient at recycling nutrients than the euphotic zone as a whole. Destruction of sinking particles within the euphotic zone was critical for determining both the overall efficiency of nutrient recycling and the vertical variations observed.
Internal sources and sinks of water, P, N, Ca, and Cl in Lake Kinneret, Israel
Authors: Smith S. V. , Serruya S. , Geifman Y. , Berman T.
Published: April 2010

Mass‐balance budgets linked among several materials are used to infer rates of processes affecting Lake Kinneret. Comparisons among budgets reveal the magnitudes of “internal” sources and sinks that cannot be directly inferred from individual budgets.

A water budget indicates that ~180 × 106 m3 of sublacustrine spring water plus ungauged surface flow enters the lake annually‐about a fifth the total inflow and two‐thirds as much water as is lost to evaporation. This total ungauged inflow delivers about 90,000 t of Cl yr−1, nine times the stream input. Ca input from total ungauged flow is about a third the stream input, and the net internal Ca sink in the system is sufficient to precipitate 60,000 t of CaCO3 yr−1.

Stream delivery of P, mainly as particulate material, is largely sequestered in the sediments (~100 t yr−1). At least 1,100 1 yr−1 of N, primarily as NO3− delivered by streams, are apparently lost to denitrification, while only 200 t yr−1 are sedimented. Cycling of N and P within the lake dominates over throughput in controlling standing stocks. Vertical mixing within the lake may play a dominating role in this cycling. Cycling of Pin the lake can be regarded as “closed”—a sediment‐water column turnover of materials with only minor hydrographic loss from the system. By contrast, N cycling is “open,” with an important net loss to the atmosphere.
The solubility of halite as a function of temperature in the highly saline Dead Sea brine system
Authors: Gavrieli Ittai , Starinsky Avraham , Bein Amos
Published: April 2010

The Dead Sea brine is characterized by high ionic strength (9–10 m) and a Ca‐Cl composition. The lake is currently saturated with respect to aragonite, gypsum, and halite. Harned's rule is applied to calculate the saturation index of halite in the Dead Sea brine system. This system includes brines at ionic strengths in the range of 9–16 m, derived from evaporating Dead Sea brine. To facilitate the calculation, we determined new interaction coefficients experimentally. These were found to be a function of the ionic strength of the solution as well as of the temperature.

urn:x-wiley:00243590:media:lno19893471224:lno19893471224-math-0001

The new parameters are used to predict the effect of temperature on halite precipitation in the lake from both the evaporating surface layer and the entire upper water body. The calculated weight of halite expected to precipitate before the onset of carnallite precipitation is on the order of 1010 t. At the present rate of evaporation at least 120 yr will pass before that point is reached.
Vertical distributions of the epifauna on manganese nodules: Implications for settlement and feeding
Authors: Mullineaux Lauren S.
Published: April 2010

Over 65% of the sessile organisms living on manganese nodules from the tropical North Pacific belong to taxa whose abundances are related to vertical position on the nodule. The nodule surface texture and boundary layer flow environment, two factors that also vary vertically, were investigated to determine whether they could account for the observed faunal distributions. The surface texture of nodules from the tropical Pacific is generally rough and knobby at the nodule base and smooth near the summit. Twenty‐five taxa, including 68% of the total individuals, were found in significantly different abundances between the rough and smooth surfaces of 34 nodules. These distributions may be due to larval responses to surface texture and can account for much of the observed vertical zonation of the fauna. Boundary layer flows over nodules were characterized from laboratory flume studies and field observations. In flows at the field site, it is expected that mean boundary shear stress and horizontal flux of particles (food or larvae) will increase from the nodule base to the summit, while particle contact rate and deposition will decrease. The observations that suspension feeders persist near the nodule summit and deposit feeders concentrate near the base suggest that vertical distributions of some taxa may be determined by adult feeding requirements. Individuals of most taxa are relatively scarce at the nodule base, indicating that their larvae are not colonizing where they accumulate passively. High abundances of matlike agglutinated foraminifers (of unknown feeding type) at the nodule summit may be due to larval responses to the relatively higher shear stresses.
The effects of patch size and substrate isolation on colonization modes and rates in an intertidal sediment
Authors: Smith Craig R. , Brumsickle Steven J.
Published: April 2010

The dynamics of soft‐bottom disturbance mosaics may be strongly influenced by life stages of colonists, disturbance size, and patch isolation. We assessed the effects of postlarval immigration, patch size, and vertical isolation on colonization following small‐scale disturbance in a mudflat in Barnstable Harbor, Massachusetts. Defaunated sediment plugs of two sizes (50 and 1,750 cm2 in plan area) and two levels of isolation (flush with the seafloor and elevated 5 cm) were implanted in the flat and sampled after 4–41 d. Postlarval immigration proved a major colonization mode for both treatment sizes. Colonization rates and successional patterns varied markedly between patch sizes, however. Faunal abundance and species number increased more rapidly, and species proportions differed, in smaller treatments primarily because the contribution of postlarval immigration varied inversely with patch size. Colonization in elevated plugs bore little resemblance to that in flush treatments, with macrofauna accumulating in raised plugs at markedly lower rates. We conclude that postlarval immigration may be a major mode of colonization at our site and perhaps in soft bottoms generally, following small‐scale disturbance, that patch size must be considered in models of benthic colonization and succession, and that interpreting results from colonization studies with raised substrata may be problematic.
Rapid growth rates of chironomids in three habitats of a subtropical blackwater river and their implications for P : B ratios
Authors: Stites David L. , Benke Arthur C.
Published: April 2010

Growth rates of chironomids from communities characteristic of three major stream habitats were examined at a field laboratory on the 6th‐order Ogeechee River in the lower Coastal Plain of Georgia. Artificial systems that simulated environmental conditions of snags, sand, and backwater habitats were used to compare growth rates of members from these different communities. Three or more growth trials were run in each system for between 9 and 16 d. The average daily biomass growth rate for individuals across all trials was highest in the snag community (0.50 d−1) followed by the backwater (0.25 d−1) and sand (0.16 d−1). The low rate in sand was attributed primarily to psammophilous taxa, Lopescladius sp. and Rheosmittia sp. For taxa found in more than one habitat, we did not find significant differences in growth among habitats. Taxon‐specific growth rates were linearly and negatively related with the natural logarithm of mass for Corynoneura taris and groups of related taxa within the Tanytarsini and Polypedilum spp. Size‐specific growth rates were applied to quantitative field data from summer 1982 to calculate daily productivity of selected chironomids from the sand habitat. Daily biomass turnover (P : B g) ranged from 0.13 to 0.51. The mean growth rate for selected sand taxa (0.31) translates into a 6‐month P : B ratio (with temperatures >20°C) of ~57. With the exception of the psammophilous taxa, annual P : B ratios for most taxa in all three habitats approach or exceed 100.
General allometric equations for rates of nutrient uptake, ingestion, and respiration in plankton organisms
Authors: Moloney Coleen L. , Field John G.
Published: April 2010

General allometric equations are derived for rates of nutrient uptake, ingestion, and respiration by planktonic organisms. Previous studies commonly calculated parameters a and b in the allometric equation R = aMb by linear regressions on log‐transformed data. This practice results in variability between data sets in estimates of both a and b, making meaningful comparisons difficult. This problem is overcome by assuming the mass‐specific form of b to be −0.25, based on accumulated empirical evidence. Values of a arc then recalculated from published data, with log transformations and an assumed regression slope of −0.25. Resulting regressions predict values of a (in pg C0.25 d−1) at 20°C as follows: 3.6 for nutrient uptake by phytoplankton and bacteria; 63 and 13 for ingestion and respiration by particle‐feeding heterotrophs. It is hypothesized that organisms that take up dissolved nutrients from solution (autotrophs and osmotrophs, e.g. phytoplankton and bacteria) have lower specific respiration rates (i.e. smaller a) when compared with organisms (either unicellular or multicellular) that ingest particulate material.
A serious inhibition problem from a Niskin sampler during plankton productivity studies
Authors: Williams P. J. leB. , Robertson J. I.
Published: April 2010

Low photosynthetic rates and reductions in chlorophyll concentrations were observed in incubations of samples taken with a 30‐liter Niskin sampler during productivity studies of oligotrophic waters in the Indian Ocean. By contrast there appeared to be no effect on community respiration. The rates of photosynthesis were 5‐fold to 10‐fold greater in samples taken with Teflon‐lined 10‐liter GoFlo bottles, and there was no systematic loss of chlorophyll. The central rubber cord of the Niskin sampler was identified as a potent source of contamination.
Carbon isotopic compositions of estuarine bacteria
Authors: Coffin Richard B. , Fry Brian , Peterson Bruce J. , Wright Richard T.
Published: April 2010

A bioassay was developed to assess the stable carbon isotopic compositions of planktonic bacteria from the Parker River estuary, Massachusetts. A small inoculum of natural bacteria was added to filtered estuarine water, then incubated for 24–48 h until bacteria reached the end of log‐phase growth. Bacteria harvested at the end of these bioassays exhibited a wide range of δ13C values from −11.5% (near the −13% value of Spartina) to −27.4‰ (near the −29‰ value of upland C‐3 plants). This wide range of δ13C values suggests that bacteria in the estuary use substrates from a variety of primary producers. Experiments with glucose and dissolved organic carbon leached from oak and Spartina leaves showed that bacteria had δ13C values within ±2‰ of their growth substrates. The results suggest that carbon isotopic measurements are useful for tracing the linkage between bacteria and the plant sources of substrates that support bacterial growth.
The dependence of the assimilation efficiency in Daphnia magna on the 14C‐labeling period of the food alga Scenedesmus acutus
Authors: Nielsen Marianne V. , Olsen Yngvar
Published: April 2010

The efficiency of carbon assimilation in Daphnia magna was estimated as a function of the 14C‐labeling time of the food alga Scenedesmus acutus. The assimilation efficiency of 14C was up to 24% higher at low labeling times (≤ 1.4 generations) (P < 0.05) than at high labeling times (≥ 4.2 generations). In uniformly labeled cells the assimilation efficiency in D. magna was 71 ± 2% SE. Variation in the assimilation efficiency with labeling time is associated with change in the relative distribution of 14C among the different cell compartments in the food alga. Uniform labeling of algae is achieved effectively via exponential growth over several generations in batch cultures from sparse inocula.
Interdependence of phosphorus, fish, and site effects on phytoplankton biomass and zooplankton
Authors: Drenner Ray W. , Threlkeld Stephen T. , Smith J. Durward , Mummert John R. , Cantrell Patricia A.
Published: April 2010

We conducted an outdoor tank experiment of factorial design with three levels of phosphorus addition cross‐classified with two levels of mosquitofish (Gambusia affinis) at two lake sites, allowing us to examine both main effects and interaction effects of phosphorus, fish, and site on phytoplankton biomass and zooplankton. Phosphorus addition significantly increased total phosphorus concentration and chlorophyll and decreased Secchi depth. Fish significantly decreased cladoceran densities and Secchi depth and increased chlorophyll and turbidity. Most phosphorus and fish effects were independent of each other except for a significant phosphorus × fish interaction on rotifers. The two sites had significant differences in total phosphorus concentration, turbidity, Secchi depth, chlorophyll, and densities of cladocerans, copepods, and rotifers. The only significant site ×phosphorus interaction was for total phosphorus. Significant site x fish interactions were detected for turbidity, Secchi depth, chlorophyll, and densities of cladocerans and rotifers. Fish effects were independent of phosphorus addition but dependent on site‐specific plankton community composition.
Changes in pigmentation associated with the bleaching of stony corals
Authors: Kleppel G. S. , Dodge R. E. , Reese C. J.
Published: April 2010

Bleaching (loss of pigmentation) is a common response by corals to environmental stress. Changes in pigmentation and the processes that caused them were studied in Montastrea annularis during a natural bleaching event off southeast Florida. Chlorophyll c, peridinin, and diadinoxanthin levels were 35, 17, and 20 times higher in normal corals than in bleached ones. Two processes, loss of zooxanthellae from the coral and loss of pigments from the remaining zooxanthellae, contributed to bleaching. Loss of zooxanthellar pigment accounted for 72% of the decrease in Chl c. The two processes contributed about equally to reduced carotenoid levels.
The humic content of lake water and its relationship to watershed and lake morphometry
Authors: Rasmussen Joseph B. , Godbout Lyse , Schallenberg Marc
Published: April 2010

The relationship of lake water color (mg liter−1 Pt) to watershed and lake morphometry, derived from topographical, hydrological, and bathymetric maps, was examined by log‐linear multiple regression on a data set obtained from 337 lakes from the northern United States and Canada. Color was positively related to the drainage ratio, and negatively related to watershed slope, mean lake depth, and lake area. Lakes that receive significant indirect drainage from other lakes were less colored than headwater lakes. The best regression model explained 60% of the variance in lake water color. Regression models were calculated separately for four geographic regions (the Laurentians of Quebec, eastern Quebec‐Maine, northeastern Wisconsin, and the Experimental Lakes Area of western Ontario). The regression coefficients for the most significant variables, drainage ratio, watershed slope, and lake area were similar over these four areas, but the regional models still had significantly smaller standard errors than the general model based on the whole data set.
Loss of total sulfur and changes in sulfur isotopic ratios due to drying of lacustrine sediments
Authors: Amaral J. A. , Hesslein R. H. , Rudd J. W. M. , Fox D. E.
Published: April 2010

Two independent methods for measuring total sulfur were used to show that underestimates of sulfur content of lacustrine sediments can occur when sediments are dried before total sulfur analysis. Different types of sediments were oven dried at 60° or 100°C or lyophilized to assess the effect of the drying method on the amount of sulfur lost. Losses ranged from 0 to 86%. Common losses were 6–22% and dependent on the sample and drying method used. Lyophilization caused greater sulfur losses (1.5‐fold) than the two oven‐drying methods. These sulfur losses caused changes in the sulfur isotopic content of the sediments and could underestimate rates of sulfur burial in sediments, organic‐S formation in sediments, and internal alkalinity production in lakes.
Predicting changes in hypolimnetic oxygen concentrations with phosphorus retention, temperature, and morphometry
Authors: Cornett R. J.
Published: April 2010

A statistical analysis of the rate of change in oxygen concentrations (VOD, mg O2 m−3 d−1) in 1‐m‐thick strata in the hypolimnia of 29 lakes suggests that these rates can be predicted from a knowledge of the annual retention of phosphorus by the lake sediments, the mean summer temperature of the stratum, and the morphometry of the stratum. VOD values increased as temperature and phosphorus retention increased. Rates were inversely proportional to the ratio of the volume of the stratum divided by the area of sediments that are contiguous to the stratum. The statistical model was tested by measuring VOD values in an independent group of 12 lakes. Predictions agreed well with the measured values. An analysis of the combined data explained 91% of the variance in VOD values. The regression correctly predicted the vertical variation in VOD values in lakes that exhibited negative heterograde, orthograde, and clinograde oxygen profiles. After further testing, this model should provide a method of predicting changes in oxygen concentrations in lakes that are subject to perturbations such as changes in temperature or nutrient loading.
Can the Lambert‐Beer law be applied to the diffuse attenuation coefficient of ocean water?
Authors: Gordon Howard R.
Published: April 2010

Radiative transfer theory is combined with a bio‐optical model of Case 1 waters and an optical model of the atmosphere to simulate the transport of radiation in the ocean‐atmosphere system. The results are treated as experimental data to study the downwelling irradiance attenuation coefficient. It is shown that the downwelling irradiance attenuation coefficient just beneath the surface and the mean downwelling irradiance attenuation coefficient from the surface to the depth where the irradiance falls to 10% of its value at the surface can be corrected for the geometric structure of the in‐water light field to yield quantities that are—to a high degree of accuracy— inherent optical properties. For Case 1 waters these geometry‐corrected attenuation coefficients are shown to satisfy the Lambert‐Beer law with a maximum error of 5–10% depending on wavelength. This near‐validity of the Lambert‐Beer law, when there are compelling reasons to believe that it should fail, is shown to result from three independent facts: the dependence of the diffuse attenuation coefficients on the geometric structure of the light field can be removed; pure seawater is a much better absorber than scatterer at optical frequencies; and the phase function for particles suspended in the ocean differs significantly from that of pure seawater. Finally, it is shown that extrapolation of the corrected diffuse attenuation coefficients to the limit c → cw yields quantities that are within 2% of the corresponding quantities that would be measured for an ocean consisting of pure seawater with the sun at zenith and the atmosphere removed.
An asymptotic closure theory for irradiance in the sea and its inversion to obtain the inherent optical properties
Authors: Zaneveld J. Ronald V.
Published: April 2010

An expression is derived for the rate at which the diffuse attenuation coefficient for vector irradiance approaches its asymptotic value in a homogeneous medium. The asymptotic approach rate is shown to be a function of boundary conditions at the surface and the asymptotic diffuse attenuation coefficient which is an inherent optical property. The asymptotic approach rate is then used to derive the vertical structure of the vector and scalar irradiances, the vector and scalar diffuse attenuation coefficients, the average cosine of the light field, and the remotely sensed reflectance at the surface, based only on the surface values of the vector and scalar irradiances and the vector and scalar diffuse attenuation coefficients. This theory is inverted and combined with previously derived radiative transfer relations to show that in principle the vertical structure of the absorption, scattering, attenuation, and backscattering coefficients can be derived from the vertical structure of the scalar and vector irradiances and the nadir radiance. An example for the western North Atlantic Ocean is provided.
Stokes vector calculations of the submarine light field in an atmosphere‐ocean with scattering according to a Rayleigh phase matrix: Effect of interface refractive index on radiance and polarization
Authors: Kattawar George W. , Adams Charles N.
Published: April 2010

A large‐scale Monte Carlo program has been written to calculate the complete four‐component Stokes vector at any region in a fully inhomogeneous atmosphere‐ocean system with inclusion of a stochastic interface. The program uses as input the Mueller matrices for the aerosols in the atmosphere as well as the hydrosols in the ocean. The Mueller matrix for the dielectric interface is also accurately accounted for. Rigorous testing was performed by comparing the Monte Carlo technique with a completely independent invariant imbedding approach; the agreement was excellent. To study the effect of the dielectric interface between atmosphere and ocean we set up a model system consisting of only Rayleigh scattering with a calm ocean, although the program can handle a stochastic boundary as well. Results are presented for both the radiance and degree of polarization at various locations in the atmosphere‐ocean system as the refractive index of the dielectric interface varies from 1.338, typical of ocean water, to a value of 1.0 which makes the interface disappear.
A numerical model for the computation of radiance distributions in natural waters with wind‐roughened surfaces
Authors: Mobley Curtis D.
Published: April 2010

A numerical technique is presented for computing radiance distributions in natural waters that have wind‐blown surfaces and depth‐dependent inherent optical properties. Input to the numerical model consists of the radiance distribution incident on the air‐water surface from above, the wind velocity, which specifies the state of randomness of the air‐water surface via a wind speed‐wave slope spectrum, the volume scattering and volume attenuation functions of the water body as functions of depth and wavelength, and the type of bottom boundary. Primary output from the model consists of directionally discretized radiances as functions of wavelength, direction, and depth throughout and above the water body.
Dependence of the diffuse reflectance of natural waters on the sun angle
Authors: Gordon Howard R.
Published: April 2010

Through Monte Carlo simulation, the variation of the diffuse reflectance of natural waters with sun angle is found to be dependent on the shape of the volume scattering function (VSF) of the medium. It is shown that single scattering theory can be used to estimate the reflectance—sun angle variation given the VSF—and, conversely, the VSF over a limited range of scattering angles can be estimated from measurements of the variation of the reflectance with sun angle. The complex variation of reflectance with the incident illumination and surface roughness can be reduced to the variation of a single parameter: the downwelling distribution function in the absence of scattering. These observations are applicable to all but the most reflective of natural waters.
A two‐component description of spectral absorption by marine particles
Authors: Morrow J. H. , Chamberlin W. S. , Kiefer D. A.
Published: April 2010

Values for the spectral absorption coefficient of particles sampled in the Sargasso Sea (34°N, 70°W) in 1987 were subjected to a multiple regression analysis to assess contributions to light absorption by phytoplankton and detritus. Specifically, values for the spectral absorption coefficient at a given wavelength were treated as a function of the values for absorption at 675 and 570 nm. The spectrum for slopes for the 675‐nm component has a slope like that of phytoplankton, and the slopes for the 570‐nm component resemble that of detritus. Individual spectra were then partitioned into phytoplankton and detrital spectral absorption coefficients with an algorithm that minimized the difference between the original spectrum and sum of the two components. The two‐component model accounted for >90% of the observed spectral absorption coefficients for all samples collected within the upper 300 m of the water column. Profiles of the two components indicated that there was little variation in mean absorption coefficient for detritus with depth. In contrast, the greatest variability was accounted for by changes in the phytoplankton component, both with depth and seasonally during 1987. This seasonal variation is interpreted in terms of photoadaptation by cells to changes in the light and vertical mixing fields.
Modeling in situ phytoplankton absorption from total absorption spectra in productive inland marine waters
Authors: Roesler Collin S. , Perry Mary Jane , Carder Kendall L.
Published: April 2010

Dissolved and suspended materials in the ocean modify the in‐water light field by absorbing and scattering photons. Direct measurement of inherent optical properties of individual optical constituents is difficult since the constituents themselves cannot all be separated. A model was developed to resolve in situ phytoplankton absorption from a measured in situ total absorption spectrum which includes water, dissolved organics, particulate detritus, and phytoplankton. The model was tested on a set of absorption spectra obtained from the productive waters around the San Juan Islands, Washington. Results indicate that the model can predict the spectral shape of phytoplankton absorption (r2 > 0.9) and total photon absorption by phytoplankton with <27% error. Total photon absorption can be used to estimate phytoplankton absorption of light energy for improved primary production predictions, given submarine light field measurements or model calculations. Although developed for high chlorophyll waters, the model parameters are easily modified for various Case 1 optical domains.