bluuebunny/crossref_metadata_2025 huggingface dataset:
The sea surface microlayer: Measurements of dissolved iodine species and nutrients in coastal waters1
Authors: Chapman Piers , Liss Peter S.
Published: March 2010

Sea surface microlayer concentrations of the dissolved iodine species iodate, iodide, and total iodine as well as the nutrients nitrite, nitrate, ammonium, and phosphate have been compared with their amounts in subsurface seawater. Little or no microlayer enhancement was found for any of these species in any of the coastal samples studied. The reason for this may be that for the species investigated there is no mechanism by which elevated microlayer concentrations can be maintained in the face of processes leading to vertical mixing into the subsurface water.
Sea urchins and kelp: The effects of short term changes in urchin diet1
Authors: Duggins David O.
Published: March 2010

Sea urchins structure benthic algal associations in many shallow subtidal communities. The kelps increased in abundance in 1978 at Torch Bay, Alaska, when Strongy‐locentrotus spp. fed upon an unusually plentiful supply of benthic diatoms and pelagic salps, reaching a safe size as a result of a temporary interruption in the normal feeding patterns of the sea urchins.
Zooplankton sample variability in a tidal estuary: An interpretative model1
Authors: Gagnon Marc , Lacroix Guy
Published: March 2010

A series of 347 vertical zooplankton hauls was made at a 175‐h anchor station in the upper St. Lawrence estuary, Québec, and current meter profiles were recorded. The 95% confidence interval of a single observation in most of the copepod time series was about 25–400% of the mean. Temporal variability consisted for the most part of semidiurnal fluctuations superimposed on a long term trend. Other periodic components were also evident. Most components were related to the advection, at discrete frequencies, of longitudinal zooplankton gradients of different magnitude and sign. The relationship was generalized by a mathematical model which shows that a distinct component of sample variability can be found at all frequencies of the current tidal constituents, provided that a longitudinal gradient is present. The relative magnitude of the variability components, for a constant gradient slope in both time and space, is identical to that of the amplitude/frequency product of the current tidal constituents. Other components not explained by the model can be related to periodic vertical displacements of the pycnocline caused by the interaction of an internal tide with a sill in the sampling area.
Feeding ecology of Rhizophysa eysenhardti, a siphonophore predator of fish larvae1
Authors: Purcell Jennifer E.
Published: March 2010

Analysis of the gastrozooids (stomachs) of 646 colonies of the cystonect siphonophore Rhizophysa eysenhardti collected by hand in the Gulf of California showed that these specimens had fed only on fish larvae. Siphonophore density during bloom conditions averaged 0.038 ± 0.004 individuals · m‒3 in an open‐water channel, and 0.91 ± 0.55 in a shallow cove. Siphonophore feeding was greater in the cove where fish larvae were more abundant than in the channel, and during dawn and dusk in the cove when prev were more available. Gastrozooid analysis and behavioral experiments showed that siphonophores fed only in the light. Digestion of fish larvae required 3–7 h, increasing with prey size. Food was assimilated by the siphonophores with 72% efficiency. Each siphonophore was estimated to consume an average of 8.8 fish larvae during a day in the cove. The heavy predation on fish larvae by R. eysenhardti suggests that both fish mortality and siphonophore population growth may be strongly affected.
The recolonization of Lake Tahoe by Bosmina longirostris: Evaluating the importance of reduced My sis relicta populations1
Authors: Threlkeld Stephen T.
Published: March 2010

On 28 August 7978, Bosmina longirostris (Crustacea: Cladocera) reappeared in the plankton of Lake Tahoe, following an absence of more than 3 years and a reduction in Mysis relicta density to 27·m‒2 from about 380·m‒2 in 1975. Bosmina seems to have been reintroduced by wind‐induced advection from Emerald Bay, a semi‐isolated embayment of the lake, suggesting the importance of chance events to zooplankton community structure. Demographic analyses of Bosmina population dynamics from 1967–1978 in Lake Tahoe indicate that reduced populations of M. relicta were not solely responsible for the timing of the Bosmina reappearance.
Selective predation by Neomysis mercedis in Lake Washington1
Authors: Murtaugh Paul A.
Published: March 2010

Feeding experiments and examination of gut contents show that Neomysis mercedis is an effective predator on zooplankton in Lake Washington. Daphnia is consistently preferred to other prey; Diaptomus and Cyclops copepodids and nauplii are always underrepresented in mysid diets. This pattern of selectivity is consistent with the hypothesis that a large population of Neomysis formerly excluded Daphnia from the lake.
Primary production and rates of algal growth in Lake Tanganyika1
Authors: Hecky R. E. , Fee E. J.
Published: March 2010

In October–November 1975 the mean rate of integral primary production in Lake Tanganyika was 1.4 g C·m‒2·d‒1 (for cloudless weather). The range of values for daily integral primary production observed at this time of year over the whole lake could occur at a single station in the course of a day. Small‐scale spatial variability was equally extreme. There was no consistent pattern of diurnal variation. The mean annual daily rate of primary production for the lake was estimated to be 1 g C·m‒2·d‒1, assuming cloudless weather. Because phytoplankton biomass was low in October–November the rates of primary production observed imply very high algal growth rates, ranging from 0.1 to 3.0·d‒1 with a mean of 0.9. This mean rate and the range of growth rates are the highest so far known for tropical lakes. High growth rates combined with persistently low algal biomass require tl: at loss rates be high also. The high fish production of the lake requires either very high trophic efficiency based on the measured pelagic primary production or an additional source of energy derived from the perenially anoxic deep water.
The phytoplankton and protozooplankton of the euphotic zone of Lake Tanganyika: Species composition, biomass, chlorophyll content, and spatio‐temporal distribution1
Authors: Hecky R. E. , Kling H. J.
Published: March 2010

The seasonal cycle of phytoplankton and protozooplankton biomass observed at two widely separated pelagic stations in the euphotic zone of Lake Tanganyika from February through November 1975 could be divided into three phases, based on algal abundance and species succession and coinciding with three phases of annual thermal stratification. Phytoplankton biomass was minimal (as low as 60 mg·m‒3) during the phase of stable stratification and maximal, as high as 930 mg·m‒3, at the end of the period of deep mixing. Diatoms, especially Nitzschia spp., were abundant only during the period of mixing, while filamentous blue‐greens, principally Anabaena sp., were prominent during a period of rapid surface warming which produced shallow mixed layers following the period of deepest mixing. The biomass of Strombidium cf. viride nearly equaled or exceeded the phytoplankton biomass during much of the stably stratified period; this protozoan probably has a symbiotic relationship with zoochlorellae, which were always present in it.

Lake Tanganyika showed a greater relative annual range between maximum and minimum phytoplankton and chlorophyll a concentrations than other tropical lakes and the temperate Great Lakes. Chlorophyll a ranged from 0.1 to 4.5 mg·m‒3 in the euphotic zone and from 0.2 to 20.4 in surface waters; phytoplankton biomass ranged from 25 to 1,570 mg·m‒3 in the euphotic zone. Annual mean concentrations were among the lowest known, 140 mg·m‒3 for phytoplankton biomass and 1.2 mg·m‒3 for chlorophyll a. Explanations for both the low annual means and the high annual variabilities may lie in he lake’s steep morphometry, which affects nutrient regeneration, and in high loss which cause high algal growth rates but low algal biomass much of the year.
Some types of temperature inversion encountered in a freshwater lake with short residence time
Authors: Wiegand Ronald C. , Carmack Eddy C.
Published: March 2010

We describe the occurrence and characteristics of temperature inversions in a deep, short residence‐time lake. Six types of fine‐scale inversions are identified on the basis of their location in the lake and the associated physical mechanism leading to their formation. For one example, potential energy considerations are used to calculate the minimum amount of work done on the water column to produce the observed deformation.
Large cod‐end reservoirs as an aid to the live collection of delicate zooplankton
Authors: Reeve M. R.
Published: March 2010

Cod‐end reservoirs up to 30 liters in volume and an ascent mechanism with paired nets are designed to increase the survival rate of delicate zooplankton for experimental studies.
Sediment trapping—A subaquatic in situ experiment1
Authors: Blomqvist Sven
Published: March 2010

A sediment trapping experiment was carried out 1.5 m above a soft bottom, at a water depth of 10 m, near the island of Askö in the archipelago of Trosa, Sweden, to investigate particulate settling in interceptor traps in an environment with moderate turbulence and currents. To ensure consistent trapping in cylinders with an interior diameter of 21–57 mm requires a height:diameter ratio ≥3. Variable trapping effects occurred in cylinders with i.d. <103 mm and a constant height:diameter ratio (8). Cylinders with small diameters strongly concentrated organic matter.
Asymmetrical relationships between absorbance, fluorescence, and dissolved organic carbon1
Authors: Stewart Arthur J. , Wetzel Robert G.
Published: March 2010

Relationships between ultraviolet absorbance, fluorescence, and concentrations of dissolved organic carbon (DOC) were examined in four model materials fractionated by gel permeation chromatography. Fluorescence was consistently a poor predictor of DOC concentration, and absorbance correctly predicted DOC concentration only in the more labile materials. Asymmetry between DOC and the two optical parameters was related to the apparent molecular weight of the dissolved organic matter (DOM) and could be explained by greater levels of internal quenching and shielding in compounds of larger apparent molecular weight. A lake‐to‐lake comparison (n = 55) showed a calcium‐related selective loss of high molecular weight humic materials, which invalidates the use of either optical characteristic as a good predictor of DOC concentration in hard‐water systems. Calcium‐related seasonal and between‐lake differences in the relative molecular weight of the DOM may selectively alter trace metal availability.
Estimating the daily contribution of carbon from zooxanthellae to coral animal respiration1
Authors: Muscatine L. , R. McCloskey L. , E. Marian R.
Published: March 2010

An equation is derived which rigorously defines the photosynthesis: respiration ratio (P:R) for any alga: invertebrate symbiotic association arid permits the computation of the fractional contribution of translocated algal carbon to the daily respiratory carbon requirement of the host animal. The equation is applied to two species of symbiotic reef corals, using O2 flux data from 24‐h continuous measurements in situ. Given certain assumptions, the algae in the shallow‐water Hawaiian reef corals Pocillopora damicornis and Fungia scutaria can supply of the order of 63 and 69% of the daily respiratory carbon demand of their respective animal hosts.
The Houtman Abrolhos Islands: Carbon metabolism of coral reefs at high latitude1
Authors: Smith S. V.
Published: March 2010

CaCO3 production by a coral community in the Houtman Abrolhos Islands (≈ 29°S latitude) proceeds at an average rate of about 32 g CaCO3·m‒2·d‒1, and organic carbon production at about 17 g C·m‒2·d‒1. Both rates are high compared to rates determined for tropical reefs, and both show strong seasonality. Complex coral reef communities do not necessarily suffer substantial metabolic depression as they approach their latitudinal limits.
Role of nutrient limitation and competition in controlling the populations of Asterionella formosa and Microcystis aeruginosa in semicontinuous culture1
Authors: Holm Nancy Peterson , Armstrong David E.
Published: March 2010

The nutrient uptake and growth kinetics of the freshwater diatom Asterionella formosa and the blue‐green alga Microcystis aeruginosa under P or Si limitation were determined in batch cultures at 20°C. Asterionella had a higher maximum growth rate and a lower half‐saturation constant for growth than Microcystis under P limitation. The maximum uptake velocity for P was higher for Asterionella than for Microcystis while the half‐saturation constants for P uptake were similar for the two species.

The Monod model of growth predicted a switch from Si limitation to P limitation for Asterionella at Si:P of about 93 (±15). In experiments with the two species grown together at various Si:P ratios, Asterionella dominated steady state semicontinuous cultures when both species were P‐limited, Si:P > 100. Microcystis became dominant when Asterionella was Si‐limited, Si:P < 100. The competition experiments showed the importance of the concentration of nutrients, as well as the ratio of the nutrients and rate of supply, in controlling the cell densities of the algal species.
The effect of environmental factors on phytoplankton growth: Light and the interactions of light with nitrate limitation1
Authors: Rhee G-‐ull , Gotham Ivan J.
Published: March 2010

The effects of simultaneous limitations of light and nutrient on growth were investigated with turbidostat and chemostat cultures of Scenedesmus sp. and Fragilaria crotonensis. The combined effects were greater than the sum of individual effects and were not multiplicative.

Under nitrate‐limited conditions the cell quota of the limiting nutrient for a constant growth rate and the subsistance quota (qo) increased as irradiance decreased. Within a certain limit of growth rates, light and qN can compensate for each other in maintaining growth rate.

Under nutrient‐sufficient conditions, cell quotas of C, N, and P, and cellular chlorophyll a concentration increased as light decreased below saturation. The cell quotas are the maximum level (qm) that can be achieved at a given irradiance. Cell quotas of nonlimiting nutrients in nutrient‐limited cultures are the same as these qm values. The increasing levels of qm and qo with decreasing irradiance indicate that nutrient requirements increase as irradiance decreases.
Light utilization by phytoplankton in Lake Kinneret (Israel)
Authors: Dubinsky Zvy , Berman Thomas
Published: March 2010

Seasonal changes in light penetration, photosynthesis, and related processes were measured in Lake Kinneret, Israel. The efficiency of penetrating light utilization for the trophogenic water column ranged from 0.33 to 4.01% and was highest when cells in high concentrations were close to the surface. The lowest specific photosynthetic assimilation values were associated with the major bloom‐forming dinoflagellate, Peridinium cinctum, which dominated the phytoplankton from February to June. On all occasions, in situ photosynthetic efficiencies increased steadily with depth as light intensity decreased in the euphotic zone. The various types of light utilization efficiencies are defined.
An optical classification of coastal and oceanic waters based on the specific spectral absorption curves of phytoplankton pigments, dissolved organic matter, and other particulate materials1
Authors: Prieur Louis , Sathyendranath Shubha
Published: March 2010

The variations of the spectral absorption coefficient of seawater can be attributed to three principal factors—phytoplankton, nonchlorophyllous particles, and yellow substances— whose concentrations are represented in this study in terms of chlorophyll a and pheophytin a content (C), the total scattering coefficient (b), and the absorption by filtered seawater at a given wavelength (Y). By assuming an exponential absorption by yellow substances, we developed a new iterative method for identifying the in situ apparent specific spectral absorption curves of the other two factors. The weighting coefficients for each of the three components are calculated for over 80 spectral absorption measurements from different representative marine regions. The reconstruction of spectral absorption curves from the three coefficients and the three specific absorption curves fits the original data with an overall average error of 3%. Relationships between these coefficients and C, b, and Y are examined. Results show that, though the spectral form of absorption by pigments can be considered as more or less invariant, the absorption “efficiency” per unit C depends on the nature of the water, and hence on the type of phytoplankton population considered. An optical classification based on the three optical coefficients related to three absorbing agents is proposed.
Primary production of microalgae in sediments measured by oxygen microprofile, H14CO3 ‐ fixation, and oxygen exchange methods1
Authors: Revsbech Niels Peter , JØrgensen Bo Barker , Brix Ole
Published: March 2010

A platinum microelectrode was used to measure changes in dissolved oxygen profiles in surface sediment exposed to light and darkness. Estimates of production by microalgae thus derived were compared with those derived from conventional methods of measuring changes in dissolved oxygen and H14CO3‒ uptake. For each particular depth in the sediment, the primary production can be determined within a few seconds by the new method. Undisturbed sediment cores were used for the H14CO3‒ fixation assay of benthic photosynthesis. Measurements of the specific activity of HCO3‒ within the photic zone showed a steep gradient of H14CO3‒ at the sediment surface. Calculations of benthic photosynthesis taking the actual specific activity into account yielded 2–5 times higher estimates than calculations using the specific activity in the overlying water. In a highly oxidized sediment, the three methods yielded almost identical results at low light intensities (200 µEinst·m‒ 2·s‒1). The oxygen methods grossly underestimated the primary productivity at higher light intensities, due to bubble formation. The conventional oxygen method grossly underestimated the primary productivity in sulfuretum‐type sediments as compared to the two other methods. In addition to photosynthesis, the oxygen consumption by the sediment was determined by oxygen microprofiles.
Nitrate and ammonia uptake in the apex of the New York Bight1
Authors: Garside C.
Published: March 2010

Nitrate and amMonia uptake were measured under seasonally extreme conditions in the apex of the New York Bight. Uptake velocities were highest in spring and summer under bloom conditions, low in winter, and lowest in fall. Uptake was saturated at 50 µEinst·m‒2·s‒1 or less throughout the year and was inhibited at high light intensities. Total inorganic nitrogen uptake was regulated by light intensity throughout the year, and the form of nitrogen taken was regulated by ammonia inhibition of nitrate uptake. Doubling times of the particulate nitrogen pool and the depletion times of the nitrate and ammonia pools proved to be sensitive indicators of the termination of a spring bloom (silicate‐limited) and a summer bloom (possibly nitrogen‐limited). Comparison of turnover times with the flushing time of the apex showed that blooms were impossible in fall and winter and were likely in spring and summer. Similar turnover times of all pools in summer suggest a quasi‐steady state between phytoplankton growth, grazing, and nutrient regeneration; perturbation of this steady state may allow nutrient‐limited conditions for phytoplankton growth to occur.
Summer internal phosphorus supplies in Shagawa Lake, Minnesota
Authors: Larsen David P. , Schults Donald W. , Malueg Kenneth W.
Published: March 2010

Phosphorus budget calculations for Shagawa Lake show that significant increases in lake P during July and August 1971–1975 originated from within the lake basin. Mass increases of 2,000–2,900 kg (35–50 µg·liter‒1) were measured, corresponding to internal supply rates of 240–680 kg·wk‒1 over a 3–9‐week interval. After anaerobi: conditions developed in late June, release from the profundal zone sediments contributed significant amounts of P to lake water.

Sediment chemical properties were determined to estimate the size of the P reservoir in the profundal zone (at water depths > 6.5 m). The P content of the surficial profundal zone sediments was 0.2–0.5% (dry wt) and a significant fraction was potentially mobile (NaOH extractable). We calculate that the upper 10 cm of these sediments contain 50,000 kg of potentially mobile P, of which a small fraction is released each summer. Although external sources of phosphorus have been reduced by about 80%, the feedback of P from the sediments is supporting the productivity of Shagawa Lake and may continue to do so for many years.
Metabolism of a Florida lake ecosystem1,2
Authors: Fontaine Thomas D. , Ewel Katherine Carter
Published: March 2010

Ecosystem and plankton community metabolism were measured for 1 year in a central Florida lake. Values of ecosystem production and respiration were similar throughout the year, suggesting that little net production accumulates seasonally or annually. Gross production and respiration were 3,071 and 3,180 g O2·m‒2·yr‒1. The plankton community was responsible for 44% of the gross production; the remainder was attributable to submersed macrophytes and associated epiphytes. Of the annual respiration, 54% was due to the plankton. Measurements of metabolism suggested that submersed plant photosynthesis and respiration were severely diminished for 1 month in summer, possibly as a result of high temperature.
Comparison between destructive and nondestructive sampling of sessile epibenthic organisms1,2
Authors: Schoener Amy , Greene Charles H.
Published: March 2010

One subset of a series of identical fouling panels was observed by a nondestructive sampling technique and results were compared with those from a second subset of panels which was destructively sampled. Initially there was no evidence for differences in development of organisms on the panels between sampling techniques. However, later results indicated that treatment effects associated with handling the nondestructively sampled panels could influence panel development.
Kinetic examination of nitrogen release by zooplankters1
Authors: Gardner Wayne S. , Scavia Donald
Published: March 2010

Kinetics of nitrogen release by Daphnia magna (0.2–0.4 mg dry wt) and Daphnia pulex (ca. 0.03 mg dry wt) were followed by measuring ammonium (plus primary amines) in water flowing past individual animals. Culture media water was pumped slowly (6 ml · h−1) through an incubation chamber (volume 0.05 ml) containing a daphnid and then either mixed with o‐phthalaldehyde reagent for continuous analysis of nitrogen compounds or passed into a sample loop of an ammonium analyzer for measurements of ammonium release at discrete intervals. Within the resolution of the technique (3 min), nutrient regeneration appeared continuous rather than pulsed. Highest rates of ammonium release, 44 nmol·(mg dry wt)−1·h−1 (SE = 5, N = 8), were typically observed immediately after the animals were removed from food. Regeneration rates for D. magna gradually decreased during the first hour to a mean steady state rate of 11 nmol·(mg dry wt)−1·h−1 (SE = 2, N = 8).
Inferring properties of mysid predation from injuries to Daphnia1
Authors: Murtaugh Paul A.
Published: March 2010

Daphnia from Lake Washington occasionally have injured tail spines; laboratory observations suggest that such injuries are caused by handling by the crustacean predator Neomysis mercedis. A short‐lived, brown “scar” that forms shortly after the tail spine is amputated provides the basis for a simple model for interpreting injury data. When combined with laboratory estimates of the duration of tail spine “scars,” the model is used to infer some properties of mysid predation: the dependence of ingestion efficiency on prey size, vertical variation in predation intensity, and the absolute in situ feeding rate of Neomysis are estimated from injury frequencies in the plankton.
The relative importance of protozoans, rotifers, and crustaceans in a freshwater zooplankton community1
Authors: Pace Michael L. , Orcutt John D.
Published: March 2010

A complete analysis of the macro‐ and microzooplankton of a monomictic lake indicates that Protozoa dominate the community numerically. During winter mixis, ciliates are found at densities of 1–8 × 103·liter−1 and constitute up to 32% of the zooplankton community biomass. With summer stratification crustaceans decline, while both the relative and absolute abundance of protozoans and rotifers increase. Densities of protozoans are highest (1–2 × 105·liter−1) in the metalimnion where scuticociliates bloom in zones of intense bacterial activity. During the period of these blooms (July–October), Protozoa account for 15–62% of the zooplankton biomass. This suggests that Protozoa make a significant contribution to rates of grazing, nutrient regeneration, and secondary productivity and should not be overlooked in zooplankton community studies.
Nonselective, nonsaturated feeding by three calanid copepod species in the Labrador Sea1
Authors: Huntley Mark
Published: March 2010

Copepod grazing experiments were conducted in suspensions of natural particulate matter during the spring bloom in the Labrador Sea to examine the phenomena of saturated ingestion rates and particle selection. There was no critical concentration of available food at which ingestion rates were saturated. Calanus finmarchicus, Calanus glacialis, and Calanus hyperboreus removed all phytoplankton in direct proportion to their abundance at chlorophyll a concentrations ranging from 0.53 to 12.1 µg·liter−1. For phytoplankton >20 µm in diameter there appeared to be no selective ingestion according to the size, shape, or species of cell. The filtration rate for a given copepod species did not change over time or space. Weight‐specific ingestion rate increased as copepod body weight increased.
Nitrous oxide concentrations in lakes: Variations with depth and time1
Authors: Knowles Roger , Lean David R. S. , Chan Yiu Kwok
Published: March 2010

Nitrous oxide (N2O) concentrations in several lakes which varied in size, depth, and trophic state were strongly influenced by oxygen concentration. High concentrations of N2O (343 µg N2O · liter−1) were found in the metalimnion of a eutrophic lake during early spring stratification when hypolimnetic O2 and NO3− were already being depleted. Up to 4 µg N2O · liter −1 were observed in oxygenated NO3−‐containing bottom waters where both nitrification and denitrification were likely occurring.
Nitrous oxide in fresh waters of the Great Lakes Basin1
Authors: Lemon Edgar , Lemon Donna
Published: March 2010

Evidence presented favors the hypothesis that little N2O is transported by rivers into or out of the Great Lakes; rather it is generated or consumed in situ. However transport of nutrients into and out of the lakes probably influences production and consumption within the lakes, i.e. NO3− and organic matter in runoff from land and effluent from cities.

Exchange values of N2O between the atmosphere and the lakes calculated from two models are related to the degree of N2O saturation of surface water. The range of fluxes is about 10 times larger than estimates made for the open ocean, i.e. ± 4 pg·cm−2·s−1.

Groundwater under a large dairy farm was rich in N2O, but once the N2O seeped into a headwaters tributary it was lost to the atmosphere.
The role of phototrophic bacteria in the sulfur cycle of a meromictic lake1
Authors: Parkin T. B. , Brock T. D.
Published: March 2010

During the summer months a dense population of green sulfur bacteria was observed in meromictic Knaack Lake, Wisconsin, at a depth where oxygen was not present. During the day, H2S was also absent at this depth but built up at night. 14CO2 studies revealed that in the light the green bacteria were photosynthetically active and oxidized the H2S. The ratio of H2S oxidized to CO2 fixed was about 0.5, indicating that H2S was completely oxidized to sulfate. In the dark, CO2 fixation did not occur and H2S accumulated. These results are related to the diurnal changes of H2S in the lake and to sulfate reduction rates in the water column.
The contributions of temperature and of the input of organic matter in controlling rates of sediment methanogenesis1
Authors: Kelly Carol A. , Chynoweth David P.
Published: March 2010

The roles of temperature and organic input in determining the rate of methane flux from anoxic sediments were examined under various laboratory and field conditions in two small Michigan lakes. As in other studies, rapid temperature increases in incubating sediment caused immediate increases in methane production rates (avg Q10 = 2.4). Under in situ conditions, where the hypolimnetic temperature is relatively cold and unchanging for long periods, methane flux was linearly related ⩽ 0.01) to organic input in these two and three other lakes for which data were available. In addition, the proportion of organic input released as methane (47 ± 9%) was close to the theoretical maximum (40 ± 8%) and was not related to temperature. When temperature is constant for long periods, as during summer stratification, CH4 production adjusts maximally to organic input. When temperature changes rapidly, its effect will be predictably superimposed upon that of organic input.
ATP and chlorophyll a as estimators of phytoplankton carbon biomass1
Authors: Hunter Bonita L. , Laws Edward A.
Published: March 2010

Thalassiosira fluviatilis, Amphiprora paludosa, and Dunaliella tertiolecta were grown in continuous culture at 20°C on a 12:12 L:D cycle under nutrient and light limitation. Diurnal periodicity was clearly evident in both ATP:C and Chl a:C ratios, but the magnitude of the diurnal changes was relatively small. The greatest range of ATP:C and Chl a:C ratios was found at low growth rates, the highest ratios being characteristic of light limitation and the lowest associated with nutrient limitation. Under strictly nitrogen limitation the range of ATP:C ratios was about 2.5–5.5 mg·g−1; Chl a:C ratios were more variable. Under phosphate limitation both ATP:C and Chl a:C ratios varied by about a factor of six. Under light limitation ATP:C ratios were insensitive to growth rate, as were Chl a:C ratios at low growth rates. Interspecific differences in both ATP:C and Chl a:C ratios were great enough to suggest that even a cursory examination of phytoplankton species composition could improve estimates of phytoplankton carbon based on ATP or Chl a measurements.
Bubble scavenging of bacteria in freshwater quickly produces bacterial enrichment in airborne jet drops1
Authors: Blanchard Duncan C. , Syzdek Lawrence D. , Weber Martin E.
Published: March 2010

Air bubbles rising through laboratory bacterial suspensions collect bacteria by interception, a collection mechanism that depends on the size of the bacteria. Many of the scavenged bacteria are transferred to the jet drops when the bubbles burst at the surface. The enrichment factor (EF) for bacteria in the top jet drops increases rapidly with the distance the bubbles rise through the water, reaching values of about 400 after only 3 cm of rise for a bubble of 380‐µm diameter. Although these numbers vary with bubble size and other parameters, cautious extrapolation to natural waters suggests that bubble scavenging is an important factor in the water‐to‐air transfer of bacteria by jet drops.
On the use of carotenoid stratigraphy in lake sediments for detecting past developments of phytoplankton
Authors: Züllig Hans
Published: March 2010

A method is described on one‐ dimensional chromatography with four sequential development steps for the separation of carotenoids in plankton and in lake sediments. Quantitative measurements of various carotenoids in cores of sediments from Swiss lakes allow the composition and development of the phytoplankton over the past 150–500 years to be worked out and also show the changing trophic condition of the lakes. an example from lake zürich shows how the change from oligotrophy to eutrophy, as documented by limnological studies, is reflected in the composition and changing concentration of specific carotenoids.
A method for preparing permanent mounts of phytoplankton for critical microscopy and cell counting1
Authors: Crumpton William G. , Wetzel Robert G.
Published: March 2010

A method is described for preparing permanent mounts of phytoplankton for critical microscopy and cell counting. Preserved phytoplankton are settled onto cover glasses (or slides), dehydrated by ethanol vapor substitution, and mounted in one of several ethanol‐soluble resins. The resulting
Competition and nutrient kinetics along a temperature gradient: An experimental test of a mechanistic approach to niche theory1
Authors: Tilman David , Mattson Mark , Langer Sara
Published: March 2010

A resource‐based model of competition correctly predicted the equilibrium outcome and approximated the population and nutrient dynamics of many nutrient‐limited competition experiments with two algal species at temperatures from 8° to 24°C. Silicate growth kinetics of temperature‐acclimated Asterionella formosa and Synedra ulna predicted that Asterionella should competitively displace Synedra below 20°C and Synedra should displace Asterionella above 20°C, as was observed. Although the growth kinetics showed no significant difference in silicate requirements at 20°C, Synedra displaced Asterionella for all starting conditions at 20°C. These experiments support a major prediction of an equilibrium theory of competition for a single resource: independent of initial population densities, the species with the lowest resource requirement should displace all competitors. Thus resource requirements, as defined by a mechanistic model, may be appropriate for defining niche boundaries.

In single species experiments, fit to the Monod model with a nutrient threshold, the nutrient‐saturated growth rate of Synedra increased from 0.16·d−1 at 8°C to 0.75 at 13°C and above; its half‐saturation constant for growth was ca. 5.0 µM SiO2, independent of temperature from 8° to 24°C. The nutrient‐saturated growth rate of Asterionella increased from 0.35·d−1 at 4°C to 0.8 at 13°C, and decreased to 0.66 at 24°C; its half‐saturation constant for growth had a temperature‐independent value of 2.1 µM SiO2 from 4° to 13°C, but increased to 10 µM SiO2 at 24°C. Half‐saturation constants for silicate‐limited growth may be temperature‐independent for temperatures within or below the optimal temperature range, but increase sharply for temperatures above it.
Copepod feeding currents: Food capture at low Reynolds number1
Authors: Koehl M. A. R. , Strickier J. Rudi
Published: March 2010

High‐speed motion pictures of dye streams around feeding calanoid copepods revealed that these important planktonic herbivores do not strain algae out of the water as previously described. Rather, a copepod flaps four pairs of feeding appendages to propel water past itself and uses its second maxillae to actively capture parcels of that water containing food particles. The feeding appendages of Eucalanus pileatus operate at Reynolds numbers of only 10−2 to 10−1. In the viscous world of a feeding copepod, water flow is laminar, bristled appendages behave as solid paddles rather then open rakes, particles can neither be scooped up nor left behind because appendages have thick layers of water adhering to them, and water and particle movement stops immediately when an animal stops beating its appendages.
Effects of island mass: Water flow and plankton pattern around a reef in the Great Barrier Reef lagoon, Australia1
Authors: Hamner W. M. , Hauri I. R.
Published: March 2010

Water currents and zooplankton distributions are described for Pandora Reef, a coralline platform reef topped by a small sand spit, subject to tidal currents within the Great Barrier Reef lagoon (Queensland, Australia). Oncoming tidal currents separated 500 m upstream of the 1‐km oblong reef. Zooplankton accumulated around the reef variously according to taxonomic group. Copepods and chaetognaths were most abundant directly upstream in an entrained water mass near the reef face and on top of the reef at high tide. Larvaceans were less abundant near the reef and were at low densities downstream. Zooplankton distributions were correlated with flow patterns. Water currents flowed asymmetrically around the reef due to shape of the platform and direction of main tidal flow. Flow separation at one end of the reef created a shear zone and strong gyres that shed periodically downstream. The other end of the reef was without flow separation but generated eddies and a weaker, stationary gyre. Downstream effects of flood and ebb exhibited major differences in flow, due to subtleties of reef morphology, and tidal height. The “island mass effect” of upstream increased primary productivity is in reality a spectrum of biological and physical events upstream, adjacent to, and downstream of islands and reefs. Existing laboratory models and mathematical theory apparently correctly predict flow around islands. At Pandora Reef little upstream water passed directly over the reef top at high tide in calm weather, and prior estimates of coral reef nutrition based on the assumption that nutrient‐poor oceanic water crosses the reef may be in error.
Nutrient mass balances for the watershed, headwaters intertidal zone, and basin of the Rhode River Estuary1
Authors: Correll David L.
Published: March 2010

Mass balances were determined for a 13‐month period for three parts of the Rhode River ecosystem, a small subestuary of the Chesapeake Bay. Organic matter, nitrogen, and phosphorus budgets were calculated for a 2,300‐ha upland watershed dominated by agriculture and secondary successional vegetation, 88 ha of tidal marshes and mudflats, and an estuarine open water basin. Less organic matter moved out to the estuary (27 t of C) than was discharged into the intertidal zone from the watersheds (71 t of C) and deposited in precipitation (3.4 t of C). Of the 2.7 t of P discharged from uplands into the intertidal zone, only 1.9 t moved into the estuary. Generally, high discharges of P from the watersheds were followed in a week or two by high discharges into the estuary from the intertidal zone. Orthophosphate constituted a significantly lower fraction of the P that moved into the estuary (38%) than of the P that was discharged from the watershed (49%). Of the 10 t of N discharged from the watershed into the intertidal zone, only 7.4 t moved into the estuary. These data indicate overall removal and storage of nutrients from land runoff by the intertidal zone. When land runoff was low the intertidal zone scavenged nutrients from tidal waters. Only when runoff was high, due to storms, were some of the stored nutrients flushed from the intertidal zone.
Comparison of two approaches used to calculate zooplankton mortality
Authors: Polishchuk L. V. , Ghilarov A. M.
Published: March 2010

Two different approaches were used to determine mortality of Diaphanosoma brachyurum collected in the central part of 59‐ha Glubokoye Lake. The first approach, the traditional one, was based on the difference between birth rate and rate of population change under the assumptions of Paloheimo’s model. The second approach involved detailed observations of size and age distribution dynamics. The mortality estimates from the two methods were nearly identical. This means that the assumptions of the traditional approach really hold in natural populations and, consequently, that this approach gives sufficiently accurate mortality estimates.
Searching for zooplankton just outside Snell's window1
Authors: Janssen John
Published: March 2010

Blueback herring (Alosa aesti valis) feeding in a visual “gulping” mode pref erentially swim toward the water surface at a region just outside Snell’s window. Outside of Snell’s window the water’s surface reflects light from the dark water beneath the fish. This dark background provides maximum contrast for zooplankters which reflect and refract light entering through their own Snell’s window. The principle is similar to that used in dark field microscopy.
Dissolved oxygen and pH relationships in northern Australian mangrove waterways
Authors: Boto Kevin G. , Bunt John S.
Published: March 2010

Consistent, highly significant linear correlations (r2 ⩾ 0.8) between pH and dissolved oxygen levels have been found in northern Australian mangrove waterways. These properties seem to be influenced by dissolved organic matter, mainly polyphenolic compounds, present in the creeks and tidal channel waters.
Primary production and the anchovy population in the Southern California Bight: Comparison of time series1
Authors: Smith Paul E. , Eppley Richard W.
Published: March 2010

Two new time series for the Southern California Bight are presented: anchovy biomass, 1951–1979, and primary production, estimated for the years 1920–1979 from 15 cruises conducted between 1974 and 1979. Annual and longer term averages show little relationship to each other except that values for both were low in the climatically warm water years 1957– 1958. The primary production time series is similar to two existing time series: CalCOFI zooplankton in the bight and microplankton in Santa Monica Bay, 1951–1966. Thus estimated primary production does reflect the carrying capacity of these waters for lower trophic level consumers.

Seasonal averages of anchovy larvae are highest in the winter and spring quarters when primary production is increasing. Interannual variation was pronounced in both seasonal average primary production and seasonal average abundance of anchovy larvae. About 50% of the variation in number of anchovy larvae was explained by variation in primary production in the same quarter and zooplankton standing stock three quarters earlier. In 1966, the year of maximum anchovy abundance, the energy expended in anchovy egg production was equivalent to about 1.8% of primary production. The anchovy ration was about 18% of primary production. The ratio of zooplankton biomass to primary production was highest in years when anchovy biomass was greatest.
Functions of coccolith formation1
Authors: Sikes C. Steven , Wilbur Karl M.
Published: March 2010

Measurements of discrimination in fixation of stable carbon isotopes by two species of coccolithophorids support the concept that coccolith formation depends on a supply of HCO3− but that CO2 is the principal substrate of photosynthesis. This in turn suggests that coccolith formation and photosynthesis are linked through their complementary influence on the internal equilibrium of dissolved inorganic carbon. Measurements of osmotic responses and transmembrane potential differences of calcified and noncalcified cells showed that although coccolithophorids behaved as if they were walled cells, the coccoliths themselves did not always contribute to this property. Also coccoliths did not protect cells from predation by marine copepods, which fed equally on calcified and noncalcified cells. The presence of a coccosphere did, however, seem to impart a greater tolerance to low salinity, allowing calcified cells to grow when noncalcified cells did not.
Inorganic nitrogen assimilation in a subalpine lake1
Authors: Axler Richard P. , Gersberg Richard M. , Goldman Charles R.
Published: March 2010

Isotope tracer techniques were used to determine the seasonal patterns of inorganic nitrogen and carbon assimilation in the epilimnion of meso‐oligotrophic Castle Lake, California. Kinetics experiments with 15N‐labeled ammonium and nitrate indicated that the nitrogen assimilation rate was generally limited by low ambient concentrations of inorganic nitrogen (DIN). The half‐saturation constants for DIN assimilation were low (0.7–9.3 µg · liter−1) and comparable to ambient levels during the nutrient‐depleted, ice‐free growing season. Ammonium assimilation was always higher than nitrate assimilation, even when nitrate concentration greatly exceeded ammonium during early summer, This observation was also supported by the results of 13NO3− uptake experiments.

The midsummer proliferation of nonheterocystous blue‐green algae was accompanied by increased carbon and nitrogen assimilation, and higher rates of particulate C and N turnover. Carbon to nitrogen and carbon to maximum nitrogen assimilation ratios were generally high (34.5 ± 13.3 and 15.6 ± 4.5 g C:g N), did not show obvious seasonal differences, and were not correlated significantly with seston compositional ratios.

These results integrated with other Castle Lake studies suggest that phytoplankton growth is maintained by efficient use of internally regenerated ammonium, in agreement with many such studies in nitrogen‐deficient marine waters.
Modeling exchangeable NH4+ adsorption in marine sediments: Process and controls of adsorption1,2
Authors: Boatman Charles D. , Murray James W.
Published: March 2010

The process and controls of ammonium adsorption in marine sediments have been studied using data from adsorption experiments with sediments from Saanich Inlet, British Columbia, and with standard reference clays. The average NH4+ adsorption constant determined experimentally for a Saanich Inlet core of 5.3 ± 1.8 liters·mol−1 was not significantly different from the constant measured in situ of 6.1 liters·mol−1.

Equations similar to a Langmuir‐type isotherm are derived which express ammonium adsorption in terms of equilibrium exchange expressions (selectivity coefficients) and activities of the major cations. An ammonium adsorption constant calculated from the model for a montmorillonite clay of 12.6 ± 1.7 liters·mol−1 agrees very well with the experimentally measured values of 11.7 ± 0.3 for a montmorillonite reference clay and 11.8 ± 1.2 for a montmorillonite‐rich pelagic sediment. The proposed model is also general enough to describe the adsorption of any minor component in seawater which undergoes ion exchange.

Comparison of ammonium adsorption constants before and after the extraction of organic matter indicates that in organic‐rich sediments a “clay‐humic complex” may be controlling ammonium adsorption. However, in organic‐poor sediments, the clay mineralogy will tend to dictate ammonium adsorption behavior.
Accumulation and transport of Cd, Cu, and Pb in an estuarine salt marsh surface microlayer1
Authors: Lion Leonard W. , Leckie James O.
Published: March 2010

Dissolved and particulate Cd, Cu, and Pb were measured in bulk solution and surface microlayer samples from an intertidal salt marsh in south San Francisco Bay. The phase distribution (dissolved vs. particulate) of metals was consistent with their calculated speciation in computer‐simulated sea‐salt matrices. Trace metal enrichment at the microlayer corresponded with physical events at the sample site. Advective exchange of Cd, Cu, and Pb between the estuary and marsh systems was dominated by transport of bulk suspended particulate metals, with an apparent net export from the marsh to the bay.