bluuebunny/crossref_metadata_2025 huggingface dataset:
Postlarval settlement of the spiny lobster Panulirus argus along the Caribbean coast of Mexico: Patterns, influence of physical factors, and possible sources of origin
Authors: Briones‐FourzÁn Patricia , Candela Julio , Lozano‐Álvarez Enrique
Published: November 2010

We analyzed and compared 17 yr of monthly settlement indices of postlarvae of the Caribbean spiny lobster, Panulirus argus, at two locations on the Mexican Caribbean coast. Along this coast, the shelf is very narrow and the local circulation is driven by waves overtopping subtidal coral reef crests. Settlement occurred year‐round, but both locations showed annual rhythmicity, average seasonal maxima during the autumn, and similar interannual variation, reflecting the influence of mesoscale oceanographic processes on settlement. Significant correlations between settlement indices and a number of interrelated physical factors indicate that sea‐level variation is the main factor influencing settlement. There was further association between extreme settlement pulses and extreme weather events (tropical storms and hurricanes) during the late summer‐autumn. The autumn settlement peak indicates that large hurricane waves enhance the onshore transport of postlarvae that originated during the spring spawning peak. The geographic range of potential sources of larvae that settle along this coast during the periods of March‐April and September‐October, 5‐9 months after hatching (the estimated larval duration for P. argus), was investigated by stochastic simulations integrating passive trajectories backward in time using 6 yr of stable outputs from a well‐established numerical model for the entire Atlantic Ocean. Trajectories from the model indicate that the local population of P. argus depends to a large extent on larval supply from many potential source regions across and outside the Caribbean but that some larvae follow pathways that permit selfrecruitment.
Biogeochemical responses to mass coral spawning at the Great Barrier Reef: Effects on respiration and primary production
Authors: Glud Ronnie N. , Eyre Bradley D. , Patten Nicole
Published: November 2010

Coral mass‐spawning represents a spectacular annual, short‐term, fertilization event of many oligotrophic reef communities. The spawning event in 2005 at Heron Island, Great Barrier Reef, was followed by an intense bloom of benthic dinoflagellates. Within a day from the first observed spawning, the primary production of the water column and the benthic compartment increased by factors of 4 and 2.5, respectively. However, the phototrophic communities were intensively grazed by macrozoans, and after 4‐5 d the net photosynthesis (P) returned to the pre‐spawning background level. The heterotrophic activity (R) mirrored the phototrophic response: a short term of elevated activity was followed by a rapid decline. However, the net autotrophic microbial communities exhibited a marked increase in the P :R ratio just after coral mass‐spawning, indicating a preferential phototrophic recycling of nutrients rather than a microbial exploitation of the release of labile organic carbon. The heterotrophic and phototrophic activity of the benthic community exceeded the pelagic activity by ~2‐ and ~5‐fold, respectively, underlining the importance of benthic activity for coral reef ecosystem function. Mass balance calculations indicated an efficient recycling of spawn‐derived nitrogen (N) and carbon (C) within the benthic reef community. This was presumably facilitated by advective solute transport within the coarse, permeable, carbonate sand.
Carbon and nitrogen loss rates during aging of lake sediment: Changes over 27 years studied in varved lake sediment
Authors: Gälman Veronika , Rydberg Johan , de‐Luna Sara Sjöstedt , Bindler Richard , Renberg Ingemar
Published: November 2010

We used a collection of ten freeze cores of annually laminated (varved) lake sediment from Nylandssjön in northern Sweden collected from 1979 to 2007 to follow the long‐term loss of carbon (C) and nitrogen (N) due to processes that occur in the lake bottom as sediment ages. We compared specific years in the different cores. For example, the loss of C from the surface varve of the 1979 core (sediment deposited during 1978) was followed in the cores from 1980, 1985, 1989, and so on until 2006. The C concentration of the sediment decreased by 20% and N decreased by 30% within the first five years after deposition, and after 27 yr in the sediment, there was a 23% loss of C and 35% loss of N. Because the relative loss of C with time was smaller than loss of N, the C:N ratio increased with increasing age of the sediment; the surface varves start with a ratio of ~10, which then increases to ~12.
Resting stages and ecology of the planktonic diatom Aulacoseira skvortzowii in Lake Baikal
Authors: Jewson David H. , Granin Nick G. , Zhdanov Andre A. , Gorbunova Ludmila A. , Bondarenko Nina A. , Gnatovsky Ruslan Yu.
Published: November 2010

Populations of the planktonic diatom Aulacoseira skvortzowii in Lake Baikal developed below 4°C, with mortality increasing rapidly at temperatures above 6.5°C. Resting spores were produced before the temperature rise associated with summer stratification. The main cue for sporulation was a decline in phosphate concentration below 15‐20 µg L‐1 P‐PO4. If phosphate declined after the onset of stratification, sporulation was poor. In culture, all cells sporulated when phosphate limited but only 15% did so when nitrate limited. Also, spore formation was diameter dependent, with most narrow cells switching to size regeneration. This affected population dynamics, with high biomasses developing in the south and middle basins but only rarely in the north basin, because phosphate did not always fall below the induction threshold necessary for sporulation and size regeneration, leading to poor recruitment. In culture, germination occurred when spores were placed in new media, with stored reserves sufficient to complete two to three divisions, even in the dark. This helped populations re‐establish when resuspended by wave action from coastal sediments where they lay dormant during summer.
Carbon dioxide fixation in the dark by photosynthetic bacteria in sulfide‐rich stratified lakes with oxic‐anoxic interfaces
Authors: Casamayor Emilio O. , García-Cantizano Josefina , Pedrós-Alió Carlos
Published: November 2010

Carbon fixation was analyzed in a series of stratified lakes with oxygen‐sulfide interfaces following 14C‐bicarbonate incorporation into oxygenic phototrophic, anoxygenic phototrophic (photosynthetic sulfur bacteria; PSB), and chemolithoautotrophic guilds (dark fixation processes), respectively. One of the lakes (Lake Cisó, Banyoles) was studied in more detail using microautoradiography of 14C‐labeled cells and microscopic observations during day and night. Dark carbon fixation was high for many of the depths sampled in all the lakes studied and there was a correspondence between carbon (C) fixation in the dark and abundance of photosynthetic purple sulfur bacteria (PSB). After in‐situ dark incubations, microautoradiographies revealed labeled cells actively incorporating inorganic carbon belonging to both unidentified rod bacteria but also to PSB (Amoebobacter sp. and Thiocystis sp.). The concentration of labeled rod bacteria was very similar in light and dark incubations, as well as in day and night samplings, and had a tendency to increase in the anoxic dark hipolimnion. Surprisingly, PSB consistently incorporated inorganic carbon in dark incubations at high rates during the day but much less at night. This suggests that photosynthetic organisms are capable of substantial dark C fixation after being subjected to light, and that "light dependent" dark carbon‐fixation activity is an issue that has to be carefully addressed in future experiments.
Direct measurement of the d13C signature of carbon respired by bacteria in lakes: Linkages to potential carbon sources, ecosystem baseline metabolism, and CO2 fluxes
Authors: Leigh McCallister S. , del Giorgio Paul A.
Published: November 2010

Using a novel method to measure the isotopic signature (δd13C) of respiratory CO2 produced by bacterioplankton, we determined the proportion of terrigenous vs. algal‐derived organic carbon (OC) respired by bacteria in a series of eight lakes in southern Que'bec (Canada). The lakes are located within the same general basin but span a large range in trophic status, morphometry, and dissolved OC (DOC) concentrations. Isotopic δ13C values of respired CO2 ranged from ‐28.4‰ to ‐32.5‰ across a gradient of lakes and streams. These values were compared with those of potential OC sources within the lakes (terrigenous and algal) using a mass balance model. The proportion of terrigenous OC respired varied from 3% to >70% and was strongly negatively correlated to lake chlorophyll a (Chl a) concentrations and weakly positively correlated to DOC: Chl a concentrations. While both total plankton and bacterial respiration (BR) increase with lake Chl a concentration, the component of BR that is supported by terrigenous OC, which ranges from 0.7 to 1.7 mg C L‐1 h‐1, stays essentially constant along the trophic gradient, increasing only slightly with DOC concentration. There is a relatively constant baseline BR supported by terrigenous OC, which becomes diluted by the BR of algal OC as the lakes become more productive. The estimated production of CO2 through BR of terrigenous OC in the epilimnion explains on average 60% of the estimated air‐water CO2 flux calculated for these lakes, suggesting that the processing of allochthonous OC by bacteria is a major component of this flux.
Agent‐based modeling of the complex life cycle of a cyanobacterium (Anabaena) in a shallow reservoir
Authors: Hellweger Ferdi L. , Kravchuk Elena S. , Novotny Vladimir , Gladyshev Michail I.
Published: November 2010

The cyanobacterium Anabaena flos‐aquae and many other phytoplankton species have a complex life cycle that includes a resting stage (akinete). We present a new agent‐based (also known as individual‐based) model of Anabaena that includes the formation and behavior of akinetes. The model is part of a coupled Eulerian‐Lagrangian model and can reproduce the main features of the observed seasonal and interannual population dynamics in Bugach Reservoir (Siberia), including an unexpectedly large bloom in a year with low nutrient concentrations. Model analysis shows that the internal loading of phosphorus (P) due to germination from the sediment bed is ~10% of the total input. However, most of the long‐term nutrient uptake for Anabaena occurs in the sediment bed, which suggests that the sediment bed is not just a convenient overwintering location but may also be the primary source of nutrients. An in silico tracing experiment showed that most water column cells (~90%) originated from cells located in the sediment bed during the preceding winter. An in silico gene knockout experiment (akinete formation is prohibited) showed that the formation of resting stages is of critical importance to the survival of the population on an annual basis. A nutrient‐reduction management scenario indicates that Anabaena densities increase because they are less sensitive to water column nutrient levels (because of the sediment bed source) than other species.
Temporal and vertical variability in photosynthesis in the North Pacific Subtropical Gyre
Authors: Corno Guido , Letelier Ricardo M. , Abbott Mark R. , Karl David M.
Published: November 2010

In situ fast‐repetition‐rate fluorometric (FRRF) surveys were conducted in the North Pacific Subtropical Gyre (NPSG) at Station ALOHA (Sta. ALOHA, 22°459N, 158°009W), from September 2002 to December 2004, to assess temporal and vertical photosynthetic variability in relation to environmental conditions. The nighttime potential photosynthetic efficiency of the photoautotrophic microbial assemblage (given as the ratio of variable to maximal fluorescence, FV:FM) was low in the mixed layer and increased with depth. High FV:FM values were observed at and below the deep chlorophyll maximum layer (DCML); some values approached the theoretical maximum for prokaryotes grown under nutrient‐replete conditions in the laboratory (0.60). In contrast, the absorption cross section of photosystem II (ςPSII) was high at the surface and decreased with depth; minima (1,000 A° 2 quanta‐1) occurred around the DCML. These vertical patterns suggest photosynthetic stress conditions in surface photoautotrophic populations. No significant seasonal cycles were found for FV:FM, but surface ςPSII values peaked in winter and decreased during summer, suggesting that seasonal variations in light availability may influence the observed ςPSII variability. A significant correlation was found among surface FV:FM, ςPSII, and the distance from the mixed‐layer depth (MLD) to the top of the nutricline. Neither nutrient nor light variations were significantly related to FV:FM and ςPSII in the DCML. Within this layer, FV:FM variability was positively and negatively related to concentrations of chlorophyll b and zeaxanthin, respectively. Our results suggest that, at Sta. ALOHA, surface photosynthesis takes place under chronic nutrient limitation, while higher photosynthetic efficiency in the lower euphotic zone appears to be sensitive to community‐structure changes.
Resilience of North Sea phytoplankton spring bloom dynamics: An analysis of long‐term data at Helgoland Roads
Authors: Wiltshire Karen Helen , Malzahn Arne Michael , Wirtz Kai , Greve Wulf , Janisch Silvia , Mangelsdorf Peter , Manly Bryan F. J. , Boersma Maarten
Published: November 2010

Analyzing one of the most extensive long‐term data series in the North Sea, the Helgoland Roads time series, we investigated the changes in the factors that potentially drive phytoplankton bloom dynamics in the German Bight. We compared the changes in these factors with the changes in the spring bloom phenology. We combined zooplankton, nutrient, weather, and phytoplankton data to analyze whether there has been a shift in trophic interactions in the North Sea affecting the spring bloom timing. The potential influence of temperature, with a mean increase of 1.5°C, was investigated. We showed that the German Bight around Helgoland is a highly dynamic system and has undergone considerable change in the last 30 yr. Nutrient levels, temperature, underwater light climate and wind speed have all changed. However, the spring bloom dynamics have hardly changed at all. We showed that the spring bloom tends to come later in warmer years but that this is not directly correlated with the overall warming trend. The known regime shift of the late 1980s is clearly visible in our data in terms of average phytoplankton winter densities and average cell size, but even so the start of the spring bloom has not changed.
Bacterial vs. zooplankton control of sinking particle flux in the ocean's twilight zone
Authors: Steinberg Deborah K. , Van Mooy Benjamin A. S. , Buesseler Ken O. , Boyd Philip W. , Kobari Toru , Karl David M.
Published: November 2010

The downward flux of particulate organic carbon (POC) decreases significantly in the oceanÂs mesopelagic or ‘twilight’ zone due both to abiotic processes and metabolism by resident biota. Bacteria and zooplankton solubilize and consume POC to support their metabolism, but the relative importance of bacteria vs. zooplankton in the consumption of sinking particles in the twilight zone is unknown. We compared losses of sinking POC, using differences in export flux measured by neutrally buoyant sediment traps at a range of depths, with bacteria and zooplankton metabolic requirements at the Hawaii Ocean Time‐series station ALOHA in the subtropical Pacific and the Japanese times‐series site K2 in the subarctic Pacific. Integrated (150‐1,000 m) mesopelagic bacterial C demand exceeded that of zooplankton by up to 3‐fold at ALOHA, while bacteria and zooplankton required relatively equal amounts of POC at K2. However, sinking POC flux was inadequate to meet metabolic demands at either site. Mesopelagic bacterial C demand was 3‐ to 4‐fold (ALOHA), and 10‐fold (K2) greater than the loss of sinking POC flux, while zooplankton C demand was 1‐ to 2‐fold (ALOHA), and 3‐ to 9‐fold (K2) greater (using our ‘middle’ estimate conversion factors to calculate C demand). Assuming the particle flux estimates are accurate, we posit that this additional C demand must be met by diel vertical migration of zooplankton feeding at the surface and by carnivory at depthÂ—with both processes ultimately supplying organic C to mesopelagic bacteria. These pathways need to be incorporated into biogeochemical models that predict global C sequestration in the deep sea.
Improved predictions of coral bleaching using seasonal baselines and higher spatial resolution
Authors: Weeks S. J. , Anthony K. R. N. , Bakun A , Feldman G. C. , Guldberg O. Hoegh-
Published: November 2010

Coral bleaching spread across the southern Great Barrier Reef in January 2006, after sea temperatures reached climatological summer maxima 2 months before normal. Current satellite‐derived warning systems were unable to detect severe bleaching conditions in the region because of their use of a constant thermal threshold (summer maximum monthly mean) and low spatial resolution (50 km). Here it is shown that such problems can be ameliorated if the thermal threshold is adjusted for seasonal variation and a 4‐km spatial resolution is used. We develop a seasonally and spatially improved thermal threshold for coral bleaching on the basis of a weekly climatology of sea surface temperatures extending from austral spring to late summer, and apply the method to two case‐study sites. At both sites, and in particular at the nearshore site that was undetected by the 50‐km satellite product, the seasonally adjusted thermal threshold produced a greatly improved consistency between accumulated heating and bleaching severity. The application of thermal stress algorithms that reflect the long‐term mean pattern in seasonal variation allows coral bleaching to be forecast with higher precision.
Tracing 13C‐enriched dissolved and particulate organic carbon in the bacteria‐containing coral reef sponge Halisarca caerulea: Evidence for DOM‐feeding
Authors: de Goeij Jasper M. , Moodley Leon , Houtekamer Marco , Carballeira Néstor M. , van Duyl Fleur C.
Published: November 2010

Here we report on the trophodynamics of the bacteria‐containing coral reef sponge Halisarca caerulea. The assimilation and respiration of the 13C‐enriched substrates glucose, algal‐derived dissolved and particulate organic matter (diatom‐DOM and ‐POM), and bacteria were followed in 1‐ and 6‐h incubations. Except for glucose, all substrates were readily processed by the sponge, with assimilation being the major fate. 13C‐Enrichment patterns in fatty acid biomarkers revealed that sponge dissolved organic 13C assimilation was both direct and bacteria mediated as tracer carbon was recovered both in bacteria‐specific and nonbacterial fatty acid. This is the first direct evidence of DOM incorporation by sponges. The present study demonstrates that the encrusting sponge H. caerulea feeds on both DOM and POM and given their dominant coverage of the largest coral reef habitat (coral cavities) it is proposed that organic matter assimilation by cryptic reef sponges may represent an important, largely overlooked ecological function. Quantitatively significant DOM processing may not be the exclusive function of the microbial world on coral reefs; sponges transform DOM to biomass, and thus retain and store organic matter in the reef system.
The source and fate of organic matter and the significance of detrital pathways in a tropical coastal ecosystem
Authors: Wai Tak-Cheung , Ng Jasmine S. S. , Leung Kenneth M. Y. , Dudgeon David , Williams Gray A.
Published: November 2010

Stable isotope analysis (SIA) and fatty acid profiling were used to elucidate the supply and fate of energy in a tropical coastal ecosystem in Hong Kong, southern China. To investigate seasonal changes in source supply on the diets of different trophic guilds, measurements were taken in three rocky bays before and after the onset of the summer monsoon, when supply of both marine macroalgal and streamborne terrestrial detritus increases. Particulate organic matter, comprising a mixture of marine and terrestrial sources, was the ultimate food source (>60%) for suspension feeders, which were the major prey items of a predatory gastropod (Thais). Increased levels of bacterial fatty acid biomarkers (BaFA) were recorded after the onset of the summer monsoon, indicating amplified dependence on detrital materials in both primary and secondary consumers. The considerable increase in the detritus fraction of sedimentary organic matter at the onset of the summer monsoon was reflected by enhanced levels of BaFA, possibly due to the degeneration of macroalgae. Significant contributions of this marine algal detritus to deposit feeders (Holothuria, 36%) and of terrestrial detritus to an echinoid grazer (Salmacis, 14%) were revealed by SIA mixing models as well as elevated BaFA concentrations. These results indicate a higher dependence on heterotrophic food chains based on decomposing marine algae and terrestrial detritus after the onset of the summer monsoon. Such seasonal variation in the importance of detrital energy sources is, therefore, likely to be important to coastal ecosystem functioning in the monsoonal tropics.
Carbon stable isotopes reveal relative contribution of shelf‐slope production to the Northern California Current pelagic community
Authors: Miller Todd W. , Brodeur Richard D. , Rau Greg H.
Published: November 2010

To better delineate the relative contribution of shelf and slope production to the northern California Current (NCC) pelagic community, we examined the cross‐shelf distribution of δ13C in 19 species of nekton, three species of Cancer decapod larvae, five gelatinous zooplankton, two dominant euphausiid species (Thysanoessa spinifera and Euphausia pacifica), calanoid copepods (Acartia sp. and Pseudocalanus sp.), and particulate organic matter (POM). Results showed 13C enrichment from nearshore shelf sites relative to offshore slope sites at all trophic levels. For POM, a significant trend in δ13C with log chlorophyll a (Chl a) was observed, with high Chl a values associated with shelf primary production. Copepods, gelatinous zooplankton, and nekton showed a significant linear decrease in δ13C with distance offshore. Nekton and gelatinous zooplankton associated with very nearshore shelf waters (<10 km distance offshore) had the highest δ13C values, whereas those off the slope (>20 km offshore) were more depleted in 13C. A comparison of results from nonparametric analysis of the pelagic community data to environmental variables also showed variables associated with the shelf and oceanic waters, with distance offshore, sea surface temperature (10 m in depth), and bottom depth being significant. Because pelagic systems are highly dynamic in space and time, our study indicated that δ13C could be used as an indicator of relative nearshore and offshore production across multiple trophic levels, even in active upwelling ecosystems such as the NCC.
Tide‐driven deep pore‐water flow in intertidal sand flats
Authors: Røy Hans , Lee Jae Seong , Jansen Stefan , de Beer Dirk
Published: November 2010

Sulfidic seeps with methane ebullition were observed at the low‐water line of intertidal sand flats at a number of locations in the Wadden Sea. Bioturbating fauna was absent in the seep areas but abundant in the more central areas of the tidal flat. At one site, the vertical methane and sulfate distribution in pore water was determined along transects from the low‐water line toward the interior of the sand flat. The resulting two‐dimensional distributions showed a plume of methane‐rich and sulfate‐depleted pore water reaching from a depth below 1.2 m beneath the sand surface up to the sediment surface at the low‐water line. The δ13C of methane released at the seeps was −68.6‰, indicating a biological origin. The 14C signature of methane was clearly elevated by anthropogenic radiocarbon, which shows that the methane was formed less than 50 yr ago. The observations indicate an internal circulation, where water enters the sand flats in the central area and exits at the low‐water line. Pore‐water flow patterns in the sand flat during the tidal cycle were calculated from the surface topography and from the pressure distribution at the flat surface across the tidal cycle. The calculated flow patterns explain the measured methane and sulfate distributions and predict a residence time of the seepage water of about 30 yr. Intertidal sand flats act as one‐way valves, passing water from the central surface through the interior of the flat to an outflow zone at and below the low‐water line with a velocity of millimeters to centimeters per day. The flow causes permeable tidal flats to emit methane to the surface water and atmosphere in substantial amounts.
Interaction between hydrodynamics and seagrass canopy structure: Spatially explicit effects on ammonium uptake rates
Authors: Morris E. P. , Peralta G. , Brun F. G. , van Duren L. , Bouma T. J. , Perez-Llorens J. L.
Published: November 2010

The hypotheses that (1) different seagrass morphologies may facilitate different nutrient uptake rates under similar hydrodynamic forcing and (2) this effect on nutrient uptake rates is spatially explicit, with the highest uptake rates at edges of patches, where currents and turbulence are highest, were examined under unidirectional flow conditions. Homogeneous patches (2 m long) of two seagrass species (Cymodocea nodosa and Zostera noltii) with contrasting shoot size and density were placed in a race track flume. 15NH4+ uptake and hydrodynamic properties along a gradient from outside to inside the patch were measured at a range of current velocities (0.05 to 0.3 m s‐1). For each velocity we also determined the height and bending of the canopy. Water velocity affected the ammonium uptake rate of both species. The almost double uptake rates of C. nodosa shoots, compared to those of Z. noltii, were mainly attributed to a twofold difference in the within‐canopy water flow (Qc, m3 s‐1). Spatial patterns in canopy water flow were highly correlated with spatial patterns in NH4+ uptake, thereby explaining the 20% higher uptake rates at the leading edge of both canopies. The correlation between spatial patterns in canopy water flow and ammonium uptake rates underlines the role of canopy and patch configuration in determining the functioning of seagrass landscapes and their associated ecosystem services, such as nitrogen assimilation.
Seagrass nurseries contribute to coral reef fish populations
Authors: Verweij Marieke C. , Nagelkerken Ivan , Hans Ingmar , Ruseler Susanne M. , Mason Paul R. D.
Published: November 2010

We here provide strong evidence that seagrass beds act as nurseries providing fish to adult populations of a coral reef fish. We studied this habitat connectivity by tracing life history movements of the Caribbean reef fish Ocyurus chrysurus (yellowtail snapper). Carbon‐ and nitrogen‐stable isotope variations in muscle tissue and otoliths (ear bones) record former food sources and show that 98% of the O. chrysurus reef population has likely passed through seagrass nurseries as juveniles during their first 2 yr of life. Our findings indicate a significant degree of habitat connectivity and stress; in order to conserve healthy reefs and sustainable fisheries of O. chrysurus, marine protected areas and fisheries reserves that traditionally focus on protecting only the coral reef habitat should be expanded to include seagrass nurseries.
Heat budget and thermal microenvironment of shallow‐water corals: Do massive corals get warmer than branching corals?
Authors: Jimenez Isabel M. , Kühl Michael , Larkum A. W. D. , Ralph P. J.
Published: November 2010

Coral surface temperature was investigated with multiple temperature sensors mounted on hemispherical and branching corals under (a) artificial lighting and controlled flow; (b) natural sunlight and controlled flow; and (c) in situ conditions in a shallow lagoon, under naturally fluctuating irradiance, water flow, and temperature. Under high irradiance and low flow conditions, hemispherical corals were 0.6°C warmer than the surrounding water. Hemispherical corals reached higher temperatures than branching corals, by a measure of 0.2°C to 0.4°C. Microsensor temperature measurements showed the presence of a thermal boundary layer (TBL). The TBL thickness was flow dependent, and under low flow conditions, a TBL up to 3 mm thick limited heat transfer to the ambient water. Combined microsensor measurements of temperature and oxygen showed that the TBL was approximately four times thicker than the diffusive boundary layer, as predicted from heat and mass transfer theory. A simple conceptual model describes coral surface temperature as a function of heat fluxes between coral tissue, skeleton, and surroundings. The slope of the predicted linear relationship between coral temperature and solar irradiance is fixed by the efficiencies of light absorption and the heat losses to the skeleton and the water. Although spectral absorptivity may play a significant role in coral warming, shape‐related differences in thermal properties can cause hemispherical corals to reach higher temperatures than branching corals. Shape‐related differences in thermal histories may thus help explain differences in susceptibility to coral bleaching between branching and hemispherical coral species.
Energetics and damping of basin‐scale internal waves in a strongly stratified lake
Authors: Shimizu Kenji , Imberger Jörg
Published: November 2010

Energetics and damping of basin‐scale internal waves and subsequent near‐bottom transport processes in Lake Kinneret were investigated using the modal analysis in a layer‐stratified irregular basin. The theory was extended to include small linear damping, and energy budgets and damping rates of five dominant internal waves were extracted by fitting numerically calculated internal waves to isotherm displacements measured by six thermistor chains distributed throughout the lake. Energy contained in the dominant internal waves (~3 GJ) resulted from a balance between energy input from diurnal winds and dissipation within a day, both of which were estimated to be 3~4 GJ d−1. Damping was caused primarily by bottom friction, and the damping rates (e‐folding time) varied from 1 to 3 d, depending on the velocity structure. Currents induced by the internal waves caused considerable spatial variability of the bottom shear stress and near‐bottom transport processes, such as entrainment rate at the top of the benthic boundary layer and mass transfer at the sediment–water interface.
Physical pathways and utilization of nitrate supply to the giant kelp, Macrocystis pyrifera
Authors: Fram Jonathan P. , Stewart Hannah L. , Brzezinski Mark A. , Gaylord Brian , Reed Daniel C. , Williams Susan L. , MacIntyre Sally
Published: November 2010

To determine the relative importance of different sources of nitrate to the annual nitrogen needs of the giant kelp Macrocystis pyrifera, we measured ambient nitrate concentrations at a kelp forest for 13 months and characterized nitrate delivery using water column thermal structure and flow data collected in the forest and at its offshore edge. The forest's monthly nitrate supply varied by a factor of 50, while measured net nitrogen acquisition varied only fivefold. Maximum net nitrogen acquisition rates for fronds in the forest interior were 0.18 mmol N g−1 month−1 during spring upwelling in 2005 and declined fourfold during autumn until upwelling resumed the following year. Modeled gross nitrogen uptake with consideration of Michaelis–Menten kinetics for nitrate and mass transfer limitation was higher than observed net acquisition except during the warm stratified summer and autumn months, when net acquisition exceeded modeled gross uptake. This shortfall indicates that the kelp forest received over half its nitrogen from sources other than nitrate such as ammonium from epibionts. Most of the nitrate in the forest was delivered as a result of upwelling‐favorable winds and convection. Internal waves and local streams contributed <9% of the nitrate delivered to the forest on an annual basis and 20% during stratified periods. Kelp used less than 5% of the nitrate supplied to the forest. Nitrate delivery to this modest sized kelp forest was roughly equivalent between alongshore (45%) and cross‐shore flows (55%), which distinguishes it from large kelp forests in which cross‐shore flows dominate exchange.
Dispersal limitations and history explain community composition of metaphyton in desert springs of the Bonneville Basin, Utah: A multiscale analysis
Authors: Keleher Mary Jane , Rader Russell B.
Published: November 2010

We examined patterns of metaphyton community composition from 150 sites in spring wetlands of the Bonneville Basin across three spatial scales: valleys, wetlands nested in valleys, and habitat types nested in wetlands (springs, channels, and marshes) to determine which scale(s) accounted for the greatest variation in metaphyton community composition. We expected local processes at the habitat scale, especially physicochemical differences between springs and marshes, to account for the majority of variation in local community composition but found that the valley scale accounted for 6.3 times more variation than the habitat scale. We suggest the importance of factors that operate at the valley scale, such as historical events (i.e., the draining of ancient Lake Bonneville) and island effects (dispersal limitations) in determining metaphyton community composition. We emphasize that dispersal limitations among valleys may have an important effect on metaphyton community composition despite the prevailing opinion that algae have exceptional powers of dispersal attributed to the worldwide distribution of some species. We base this assertion on three observations: first, the absence of species in isolated springs compared to springs associated with large complexes; second, 67% of the taxa in the Bonneville Basin occurred in only three or fewer sites; and third, the average Bray‐Curtis similarity between all sites based on all taxa (242) was only 14.1%, which is an unlikely low value if metaphyton taxa can freely disperse between sites. Future studies should incorporate the potential importance of history and dispersal limitations as researchers continue to explore patterns of algal community composition across multiple scales.
Dissolution of biogenic silica from land to ocean: Role of salinity and pH
Authors: , Socratis Loucaide , Cappelle Philippe Van , Behrends Thilo
Published: November 2010

The dissolution rates of diatom frustules, phytoliths, two diatomaceous lake sediments, a siliceous ooze from the Southern Ocean, a diatomite deposit, and a synthetic amorphous silica were measured in flow‐through reactors supplied with either seawater or freshwater. Although the rates varied by more than one order of magnitude among the different siliceous materials, for any given solid the rate was systematically higher in seawater than freshwater, on average by a factor of five. Flow‐through reactor experiments with the diatom frustules and synthetic silica using mixtures of freshwater and seawater indicated that most of the rate increase occurred for seawater fractions between 0 and 50%. The observed rate enhancement is attributed to the higher pH of seawater and the catalytic effect of seawater cations on the hydrolysis of siloxane bonds at the silica surface. Because of their abundance in seawater, Na+ and Mg2+ are mainly responsible for the salinity‐induced rate increase. The large difference in dissolution kinetics between freshwater and seawater helps explain the very efficient recycling of biogenic silica in marine environments compared with freshwater lakes. Enhanced dissolution at the land‐ocean transition of biogenic silica produced by terrestrial plants and freshwater diatoms may represent a significant, but largely overlooked, source of nutrient silicon for estuarine and nearshore marine ecosystems.
Tracking natal origins of salmon using isotopes, otoliths, and landscape geology
Authors: Rachel Barnett-Johnson , Pearson Thomas E. , Ramos Frank C. , Grimes Churchill B. , Bruce MacFarlane R.
Published: November 2010

The inability to identify natal origins (i.e., individual rivers and hatcheries) of adult Pacific salmon in the ocean has impeded our understanding of their ocean ecology and the management of mixed‐stock fisheries. Strontium isotope (87Sr : 86Sr) ratios recorded in otoliths of fall‐run Chinook salmon (Oncorhynchus tshawytscha) from all major natural and hatchery spawning sites in the California Central Valley can be used as natural tags to identify natal origins with high accuracy (82%) and improved when additional otolith markers identified fish to hatchery (98%) or naturally spawned (94%) sources. A spatial baseline of 87Sr : 86Sr signatures was developed by targeting 87Sr : 86Sr within juvenile portions of otoliths accreted in natal streams and hatcheries using laser ablation and a multicollector inductively coupled plasma mass spectrometer. The availability and analyses of known‐origin coded wire tagged adults provides a rare test of this technique to reconstruct early life‐histories of adults (90% correct classification). By quantifying the area of watershed influenced by granitic rocks using hydrologic and geologic data layers, we explained 94% of the geographic variability in 87Sr : 86Sr in salmon otoliths. Creating a spatial map in geographic information systems relating landscape geology to Sr isotopes is a useful framework for evaluating the efficacy of Sr isotopes to track the natal origin and movement of salmonids in freshwater, estuarine, and marine environments to better understand how processes occurring in these habitats influence the growth, survival, and reproductive success of anadromous fishes.
Rainwater as a source of Fe(II)‐stabilizing ligands to seawater
Authors: Willey Joan D. , Kieber Robert J. , Seaton Pamela J. , Miller Carrie
Published: November 2010

Rainwater hydrophobic extractable dissolved organic matter (EDOM) contains ligand(s) that completely prevent Fe(II) oxidation for at least 4 h after rain is mixed with seawater. The EDOM Fe(II) complex is at least of comparable strength to the ferrozine complex, indicating that this rainwater Fe(II) ligand is among the strongest Fe(II) ligands ever observed in natural waters. In addition to the strong class of ligands that prevent oxidation, rainwater EDOM also contains weaker Fe(II) ligands that slow oxidation of Fe(II) in seawater. Rainwater EDOM is not a single molecule but rather a complex mixture of relatively hydrophobic compounds, even in marine rain with minimal continental influence. When EDOM from the nearby Cape Fear River was extracted using the same method as for rainwater, the river EDOM could not prevent or even slow the oxidation of Fe(II) on mixing with seawater. Therefore, rainwater EDOM is fundamentally different than surface‐water EDOM with respect to the strength of Fe(II) ligands. The stability of EDOM complexed Fe(II) most likely affects the bioavailability of rainwater‐derived Fe in the surface ocean because the length of time atmospherically deposited Fe remains dissolved in seawater is critical to its role as a phytoplankton nutrient.
Excess carbon in aquatic organisms and ecosystems: Physiological, ecological, and evolutionary implications
Authors: Hessen Dag O. , Anderson Thomas R.
Published: November 2010

Cells and organisms, both autotrophs and heterotrophs, commonly face imbalanced access to and uptake of elements relative to their requirements. C is often in excess relative to key nutrient elements like N or P in photoautotrophs. Likewise, one of the lessons from ecological stoichiometry is that the growth of consumers, especially herbivores and detritivores, is commonly limited by N or P such that they also experience C in excess in relative terms. "Excess" implies wastage, yet this definition, which is consistent with purely stoichiometric arguments, is by no means straightforward. In fact, many organisms put this apparently surplus C to good use for fitness‐promoting purposes like storage, structure, and defense or mutualistic goals like symbiosis. Nevertheless, genuine excesses do occur, in which case the remaining "leftover C" must be disposed of, either in organic or inorganic form via increased metabolic activity and respiration. These fluxes of C in various forms have major effects on the C balance of organisms, as well as governing the energy flux and C pathways at the ecosystem level. We here discuss evolutionary and ecological implications of "excess C" both at the organism and ecosystem level.
Large, non‐Redfieldian drawdown of nutrients and carbon in the extratropical North Atlantic Ocean (46°N): Evidence for dinitrogen fixation?
Authors: Park Geun-Ha , Lee Kitack , Wanninkhof Rik , Zhang Jia-Zhong , Hansell Dennis A. , Feely Richard A.
Published: November 2010

Considerable drawdown of total dissolved inorganic carbon (CT) and oversaturation of oxygen (O2) within a cold (15°C) oligotrophic eddy in the extratropical North Atlantic Ocean (46°N, 20.5°W) indicate that, despite the absence of nitrate (NO3−), the eddy was highly productive. Estimates of net community production using the mass balances of CT and O2 were two to five times greater than those obtained using the mass balance of NO3−. The remineralization rates obtained using the integrated rates of CT and NO3− accumulation and O2 utilization for the upper thermocline waters (35‐300‐m depth) were in agreement with CT‐ and O2‐based net community production over the same period; however, all the estimates exceeded the NO3− ‐based net community production by a factor of two to five, pointing to a considerable accumulation of NO3− in the upper thermocline in excess of changes in the mixed‐layer NO3− inventory. The amount of this excess NO3− suggests that a considerable fraction of the net community production was not supported by the mixed‐layer NO3− inventory and that an external source of NO3− must be present. Of the various mechanisms that might explain the inequity between NO3− drawdown in the surface layer and NO3− accumulation in the upper thermocline, N2 fixation is the most viable yet surprising mechanism for producing such excess NO3− in this oligotrophic eddy. A significant fraction of net community production in oligotrophic extratropical waters could be supported by processes that are not fully explored or to date have been considered to be insignificant.
Nutrient limitation of picophytoplankton photosynthesis and growth in the tropical North Atlantic
Authors: Davey Margaret , Tarran Glen A. , Mills Matthew M. , Ridame Celine , Geider Richard J. , LaRoche Julie
Published: November 2010

Identification of the proximal nutrient limiting primary production is a necessary first step toward evaluating the physiological state of phytoplankton communities and the biogeochemical constraints on the current oceanic carbon cycle. We conducted 48‐h nutrient addition bioassay experiments to evaluate nitrogen, phosphorus, and iron limitation of primary productivity, net chlorophyll synthesis, and net increase in cell numbers of the dominant picophytoplankton from the tropical North Atlantic. Our results indicate that N was the proximal limiting factor for primary production during the autumn of 2002, followed by P and then Fe. Net chlorophyll synthesis was significantly stimulated by addition of N alone and further stimulated by addition of P. Analysis of picophytoplankton populations by analytical flow cytometry revealed a more complex response. Cellular red fluorescence, an index of cell chlorophyll content, increased in Prochlorococcus, Synechococcus, and picoeukaryotes in response to addition of NH4NO3 but was not affected by single or combined additions of P and Fe. In contrast, cell abundance in these picophytoplankton populations increased only after combined N and P (63% of comparisons) or N and Fe (21% of comparisons) additions. Thus, our experiments revealed that chlorophyll synthesis and primary production were limited by the availability of nitrogen alone, while net increase in cell abundance was colimited by N and P or N and Fe in the majority of these picophytoplankton populations.
Propagation of an atmospheric climate signal to phytoplankton in a small marine basin
Authors: Li William K. W. , Glen Harrison W.
Published: November 2010

A 14‐yr record of weekly observations in Bedford Basin (Canada) was used to describe the direction and magnitude of departures from long‐term mean conditions in both climate and plankton components, for the purpose of detecting common patterns. Seasonal vertical stratification of the water column is determined primarily by temperature, but multiyear change in the annual deseasonalized average stratification is induced by salinity, which is linked to precipitation and river discharge. Stratification anomalies explain significant amounts of variability in the anomalies of nutrients and total phytoplankton biomass, especially that contributed by diatoms, but not the biomass of nanophytoplankton and picophytoplankton. Instead, the responses of the small phytoplankton groups appear directly related to temperature. Trophic linkage between phytoplankton and copepods is not statistically demonstrable, but there is strong evidence of linkage between phytoplankton and bacterioplankton. Temporal sign switching, which is the coherent departure from norm in both an ecosystem driver and response, strongly indicates the propagation of an atmospheric signal to phytoplankton in surface waters of Bedford Basin and thence further through trophic linkage and export.
Local and large‐scale climate forcing of Puget Sound oceanographic properties on seasonal to interdecadal timescales
Authors: Moore Stephanie K. , Mantua Nathan J. , Kellogg Jonathan P. , Newton Jan A.
Published: November 2010

The influence of climate on Puget Sound oceanographic properties is investigated on seasonal to interannual timescales using continuous profile data at 16 stations from 1993 to 2002 and records of sea surface temperature (SST) and sea surface salinity (SSS) from 1951 to 2002. Principal components analyses of profile data identify indices representing 42%, 58%, and 56% of the total variability at depth‐station combinations for temperature, salinity, and density, respectively, and 22% for water column stratification. Variability in the leading pattern of Puget Sound water temperature and salinity profiles is well correlated with local surface air temperatures and freshwater inflows to Puget Sound from major river basins, respectively. SST and SSS anomalies are informative proxies for the leading patterns of variations in Puget Sound temperature and salinity profiles. Using this longer time history of observations, we find that SST and SSS anomalies also have significant correlations with Aleutian Low, El Niñntilde;o‐Southern Oscillation, and Pacific Decadal Oscillation variations in winter that can persist for up to three seasons or reemerge the following year. However, correlations with large‐scale climate variations are weaker compared to those with local environmental forcing parameters.
Spatial variations in time‐integrated plankton metabolic rates in Sagami Bay using triple oxygen isotopes and O2:Ar ratios
Authors: Sarma V. V. S. S. , Abe O. , Saino T.
Published: November 2010

Plankton metabolic rates, such as rates of gross, net community production and community respiration, were measured in the surface waters using triple oxygen isotopes and O2 : Ar ratios. The 17D anomaly showed clear coastal and offshore gradients that were consistent with the distribution of chlorophyll a and oxygen saturation. Gross primary production (GPP) rates in coastal regions were several times higher than offshore regions, and the net‐to‐gross production ratio (N : G) indicated that coastal regions were net autotrophic, whereas offshore regions were net heterotrophic. On a seasonal scale, about 73% of the phytoplankton‐produced carbon was respired. Based on floating‐sediment‐trap data, export production to the aphotic zone was about 12‐20% of the GPP; the rest accumulated as dissolved organic carbon (DOC) or was respired.