Articles

Published journal articles by MLML faculty, staff and students. Full text is included when copyright allows.


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Synthesis of iron fertilization experiments: From the iron age in the age of enlightenment
Synthesis of iron fertilization experiments: From the iron age in the age of enlightenment
Comparison of eight iron experiments shows that maximum Chl a, the maximum DIC removal, and the overall DIC/Fe efficiency all scale inversely with depth of the wind mixed layer (WML) defining the light environment. Moreover, lateral patch dilution, sea surface irradiance, temperature, and grazing play additional roles. The Southern Ocean experiments were most influenced by very deep WMLs. In contrast, light conditions were most favorable during SEEDS and SERIES as well as during IronEx-2. The two extreme experiments, EisenEx and SEEDS, can be linked via EisenEx bottle incubations with shallower simulated WML depth. Large diatoms always benefit the most from Fe addition, where a remarkably small group of thriving diatom species is dominated by universal response of Pseudo-nitzschia spp. Significant response of these moderate (10-30 μm), medium (30-60 μm), and large (>60 μm) diatoms is consistent with growth physiology determined for single species in natural seawater. The minimum level of "dissolved" Fe (filtrate < 0.2 μm) maintained during an experiment determines the dominant diatom size class. However, this is further complicated by continuous transfer of original truly dissolved reduced Fe(II) into the colloidal pool, which may constitute some 75% of the "dissolved" pool. Depth integration of carbon inventory changes partly compensates the adverse effects of a deep WML due to its greater integration depths, decreasing the differences in responses between the eight experiments. About half of depth-integrated overall primary productivity is reflected in a decrease of DIC. The overall C/Fe efficiency of DIC uptake is DIC/Fe ∼ 5600 for all eight experiments. The increase of particulate organic carbon is about a quarter of the primary production, suggesting food web losses for the other three quarters. Replenishment of DIC by air/sea exchange tends to be a minor few percent of primary CO2 fixation but will continue well after observations have stopped. Export of carbon into deeper waters is difficult to assess and is until now firmly proven and quite modest in only two experiments. Copyright 2005 by the American Geophysical Union., Cited By (since 1996):271, Oceanography, Art. No.: C09S16, Downloaded from: http://onlinelibrary.wiley.com/doi/10.1029/2004JC002601/pdf (16 June 2014).
Synthesizing mechanisms of density dependence in reef fishes: Behavior, habitat configuration, and observational scale
Synthesizing mechanisms of density dependence in reef fishes: Behavior, habitat configuration, and observational scale
Coral and rocky reef fish populations are widely used as model systems for the experimental exploration of density-dependent vital rates, but patterns of density-dependent mortality in these systems are not yet fully understood. In particular, the paradigm for strong, directly density-dependent (DDD) postsettlement mortality stands in contrast to recent evidence for inversely density-dependent (IDD) mortality. We review the processes responsible for DDD and IDD per capita mortality in reef fishes, noting that the pattern observed depends on predator and prey behavior, the spatial configuration of the reef habitat, and the spatial and temporal scales of observation. Specifically, predators tend to produce DDD prey mortality at their characteristic spatial scale of foraging, but prey mortality is IDD at smaller spatial scales due to attack-abatement effects (e.g., risk dilution). As a result, DDD mortality may be more common than IDD mortality on patch reefs, which tend to constrain predator foraging to the same scale as prey aggregation, eliminating attack-abatement effects. Additionally, adjacent groups of prey on continuous reefs may share a subset of refuges, increasing per capita refuge availability and relaxing DDD mortality relative to prey on patch reefs, where the patch edge could prevent such refuge sharing. These hypotheses lead to a synthetic framework to predict expected mortality patterns for a variety of scenarios. For nonsocial, nonaggregating species and species that aggregate in order to take advantage of spatially clumped refuges, IDD mortality is possible but likely superseded by DDD refuge competition, especially on patch reefs. By contrast, for species that aggregate socially, mortality should be IDD at the scale of individual aggregations but DDD at larger scales. The results of nearly all prior reef fish studies fit within this framework, although additional work is needed to test many of the predicted outcomes. This synthesis reconciles some apparent contradictions in the recent reef fish literature and suggests the importance of accounting for the scale-sensitive details of predator and prey behavior in any study system.
System of quasi-zonal jets off California revealed from satellite altimetry
System of quasi-zonal jets off California revealed from satellite altimetry
A discrete wavelet transform was applied to satellite altimetry data for the period 1992-2007 off California to decompose the SSH signal into inter-annual, annual, semiannual and shorter period components. For the lowest frequency (inter-annual) component, a system of alternating quasi-zonal jets was detected. The jet system was delineated by a north-south series of quasi-zonal bands of co-rotating eddies; that is, the eddies were embedded in a shearing zonal flow. The direction of eddy rotation alternated between adjacent bands. The temporal behavior of the jet system showed the existence of quasi-stationary states and transitions between them. Observed non-linear effects of the evolution of the jets included southward drift at about 0.2 cm sec -1, deviations of the jets from the zonal direction, and re-forming of the jet system through decay and merging of eddy chains. Copyright 2009 by the American Geophysical Union., Cited By (since 1996):6, Oceanography, Art. No.: L03609, CODEN: GPRLA, Downloaded from:http://onlinelibrary.wiley.com/doi/10.1029/2008GL036327/pdf (16 June 2014).
Systematics and biodiversity of sharks, rays, and chimaeras (Chondrichthyes) of Taiwan
Systematics and biodiversity of sharks, rays, and chimaeras (Chondrichthyes) of Taiwan
All 13 orders of chondrichthyan fishes occur in Taiwanese waters, representing 52 chondrichthyan families (31 shark, 19 batoid, 2 chimaeroid) and 98 genera (64 shark, 31 batoid, 3 chimaeroid). A total of 119 shark, 58 batoid, and 4 chimaera species may occur in the waters surrounding Taiwan, pending taxonomic resolution of some groups. Of the 34 nominally described species from Taiwan, 17 are currently considered valid. The majority of named species occurred during two peak periods in Taiwanese chondrichthyan research; the first between 1959–63, when 13 nominal species were described, of which 7 remain valid today, and a second peak period between 2003–13 when 9 nominal species were described, of which 6 remain valid. The overall species diversity of Taiwan’s chondrichthyan fauna is comparable to that of other adjacent marine zoogeographic hotspots, e.g. Japan (126 shark, 75 batoid, 11 chimaeroid species) and the Philippines (81 shark, 46 batoid, 2 chimaeroid species). The Carcharhiniformes, Squaliformes, Myliobatiformes, and Rajiformes are the most dominant orders in terms of abundance and species-richness within this region. Each of these groups may increase in relative diversity with improved taxonomic resolution resulting from the incorporation of molecular tools and renewed morphological studies. Improved identification of Taiwan’s chondrichthyan fauna will aid in developing better conservation and management practices.
THE RESPONSE OF A PREDATORY FISH, OPHIODON ELONGATUS, TO A MARINE PROTECTED AREA: VARIATION IN DIET, CATCH RATES, AND SIZE COMPOSITION
THE RESPONSE OF A PREDATORY FISH, OPHIODON ELONGATUS, TO A MARINE PROTECTED AREA: VARIATION IN DIET, CATCH RATES, AND SIZE COMPOSITION
Marine Protected Areas (MPAs) are a management tool used to protect and sustain many ecologically and economically important fish species from overexploitation by recreational and commercial fishing. Lingcod (Ophiodon elongatus) and some of its prey species, such as rockfish (Sebastes spp.), are species that are protected from fishing in some California MPAs. Lingcod is an apex predator that consumes a variety of fish and invertebrate species. In this study, I sought to assess the effect of an MPA on the abundance, size and diet of Lingcod. I hypothesized that Lingcod in a no-take MPA would be more abundant and larger than Lingcod in an adjacent reference site (REF) that was open to fishing. Furthermore, I hypothesized that diet would differ between Lingcod in caught the MPA and Lingcod in the REF. I collected Lingcod from the Point Buchon State Marine Reserve (MPA) and an adjacent REF site that was open to fishing. I measured, weighed, sexed, and collected stomach contents from Lingcod using the gastric lavage (stomach pumping) technique. Then, I identified prey items from Lingcod stomach contents down to the lowest taxonomic level possible and quantified diet composition by percent by occurrence, percent by number, and percent by mass. Lingcod in the MPA consumed more fish prey items than Lingcod in the REF site. Lingcod in the REF consumed more cephalopod prey items than Lingcod in the MPA. I analyzed the four most common prey items (rockfish, anchovies, flatfish, and octopus) for nutritional content. My data suggest that Lingcod increased in size and abundance in a no-take MPA because they do not suffer from fishing mortality. However, a more nutritious diet could also contribute to a biologically significant advantage for Lingcod in the MPA. To address this would require further research focused on calculating the net energy (gross energy extracted from the prey item minus the energetic costs of handling and digesting the prey item) obtained by Lingcod from consuming different fish and cephalopod prey items. MPAs can be an effective management tool for protecting fish stocks, although, it is important to understand the interspecific interactions between predator and prey
Targeting Abundant Fish Stocks while Avoiding Overfished Species
Targeting Abundant Fish Stocks while Avoiding Overfished Species
Historically, it has been difficult to balance conservation goals and yield objectives when managing multispecies fisheries that include stocks with various vulnerabilities to fishing. As managers try to maximize yield in mixed-stock fisheries, exploitation rates can lead to less productive stocks becoming overfished. In the late 1990s, population declines of several U.S. West Coast groundfish species caused the U.S. Pacific Fishery Management Council to create coast-wide fishery closures, known as Rockfish Conservation Areas, to rebuild overfished species. The fishery closures and other management measures successfully reduced fishing mortality of these species, but constrained fishing opportunities on abundant stocks. Restrictive regulations also caused the unintended consequence of reducing fishery-dependent data available to assess population status of fished species. As stocks rebuild, managers are faced with the challenge of increasing fishing opportunities while minimizing fishing mortality on rebuilding species. We designed a camera system to evaluate fishes in coastal habitats and used experimental gear and fishing techniques paired with video surveys to determine if abundant species could be caught in rocky habitats with minimal catches of co-occurring rebuilding species. We fished a total of 58 days and completed 741 sets with vertical hook-and-line fishing gear. We also conducted 299 video surveys in the same locations where fishing occurred. Comparison of fishing and stereo-video surveys indicated that fishermen could fish with modified hook-and-line gear to catch abundant species while limiting bycatch of rebuilding species. As populations of overfished species continue to recover along the U.S. West Coast, it is important to improve data collection, and video and fishing surveys may be key to assessing species that occur in rocky habitats.
Taxon-specific analysis of microzooplankton grazing rates and phytoplankton growth rates
Taxon-specific analysis of microzooplankton grazing rates and phytoplankton growth rates
Cited By (since 1996):34, Oceanography, CODEN: LIOCA, We performed laboratory experiments to test the accuracy of using HPLC to estimate taxon-specific grazing and growth rates obtained by the dilution technique. In seven of nine experiments, this technique underesti- mated microzooplankton grazing rates. The average estimated grazing rates were 52% of the true grazing rates for chlorophyll a and 33% for taxon-specific pigments. With the food sources Phaeodactylum tricornutum, Isochrysis galbana, Gymnodinium sp., and Emiliania huxleyi, the clearance rates for Oxyrrhis marina were between 2 x 10-3 and 7 x 10-3 ml grazer- 1 d- 1, at initial food concentrations of ~ 5 x 103 cells ml- 1. At higher food concentrations (1 x 105 cells ml-1) clearance rates decreased to 1 X 10-4 ml graz- er- 1 d- 1. In field experiments performed in September 1991 and March 1992 in Monterey Bay, California, 21-55% of the phytoplankton standing stock was consumed daily by microzooplankton grazing. The underestimation of grazing rates in the laboratory experiments implies that rates obtained in field incubations may be in error., Downloaded from: aslo.org/lo/toc/vol_40/issue_4/0827.pdf (16 June 2014).
Taxonomic reassessment of rhodolith-forming species of Lithophyllum (Corallinales, Rhodophyta) in the Gulf of California, Mexico
Taxonomic reassessment of rhodolith-forming species of Lithophyllum (Corallinales, Rhodophyta) in the Gulf of California, Mexico
Rhodolith beds (beds composed of unattached coralline red algae) in the Gulf of California, Mexico, are widespread and commonly dominated by specimens belonging to Lithophyllum. The number of rhodolith-forming species of Lithophyllum in these beds, however, has been uncertain, and there are contradictory statements in the recent literature concerning putative species. Five species have been recognized, but it also has been suggested that these represent only a single polymorphic species. More than 700 specimens from 45 localities were examined and compared with all relevant types to determine how many species are represented and how they might be distinguished. Most of the types analyzed agree with the modern concept of Lithophyllum; however, two species, Lithophyllum californiense Heydrich and Lithophyllum bracchiatum (Heydrich) Me. Lemoine, do not agree with the modern concept of Lithophyllum and have been excluded from the genus. None of the characters used previously to delimit species in the group was taxonomically reliable. Moreover, an evaluation of all specimens based on modern characters, especially relating to tetrasporangial conceptacle anatomy, showed that only a single species was present, namely Lithophyllum margaritae (Hariot) Heydrich. Both within and between populations, L. margaritae exhibits a continuum of growth forms: encrusting to foliose to fruticose to warty to lumpy. The dominance of particular growth forms within an area appears to be linked to local environmental conditions., Cited By (since 1996):41, Seaweeds, CODEN: PYCOA
Taxonomic revision of the agaraceae with a description of Neoagarum gen. nov. and reinstatement of Thalassiophyllum
Taxonomic revision of the agaraceae with a description of Neoagarum gen. nov. and reinstatement of Thalassiophyllum
We confirmed the monophyly of the Agaraceae based on phylogenetic analyses of 6 mitochondrial and 6 chloroplast gene sequences from Agarum, Costaria, Dictyoneurum and Thalassiophyllum species as well as representative species from other laminarialean families. However, the genus Agarum was paraphyletic, comprising two independent clades, A. clathratum/A. turneri and A. fimbriatum/A. oharaense. The latter clade was genetically most closely related to Dictyoneurum spp., and morphologically the species shared a flattened stipe bearing fimbriae (potential secondary haptera) in the mid to upper portion. The phylogenetic position of Thalassiophyllum differed between the two datasets: in the chloroplast gene phylogeny Thalassiophyllum was included in the A. clathratum/A. turneri clade, but in the mitochondrial gene phylogeny, it formed an independent clade at the base of the Agaraceae, the same position it took in the phylogeny when the data from both genomes were combined despite a larger number of bp being contributed by the chloroplast gene sequences. Considering the remarkable morphological differences between Thalassiophyllum and other Agaraceae, and the molecular support, we conclude that Thalassiophyllum should be reinstated as an independent genus. Dictyoneurum reticulatum was morphologically distinguishable from D. californicum due to its midrib, but because of their close genetic relationship, further investigations are needed to clarify species level taxonomy. In summary, we propose the establishment of a new genus Neoagarum to accommodate A. fimbriatum and A. oharanese and the reinstatement of the genus Thalassiophyllum.
Techniques for enhancing vertebral bands in age estimation of California elasmobranchs
Techniques for enhancing vertebral bands in age estimation of California elasmobranchs
Vertebrae from 1,152 elasmobranchs representing 22 species were collected between 1979 and 1981 to assess methods of enhancing incremental growth bands for age estimation. Thus far, we have tested methods previouslyreported in the literature, and have developed new procedures to enhance growth increments on 684 individuals of 14 species of elasmobranchs. Silver nitrate impregnation, X-radiograpby, and cedarwood oil clearing were the most successful techniques. Less effeetive were alizarin red staining, paraffin impregnation, alcohol immersiorn, and formic acid etching. Methods for preparing vertebrae and enhancing and counting growth increments are presented, and the problems associated with interpreting tile annual nature of such counts are discussed.
Tectonic and glacial related seafloor geomorphology as possible demersal shelf rockfish habitat surrogates-Examples along the Alaskan convergent transform plate boundary
Tectonic and glacial related seafloor geomorphology as possible demersal shelf rockfish habitat surrogates-Examples along the Alaskan convergent transform plate boundary
Seafloor geology plays a major role in habitat formation and can be used to remotely identify key habitats for some commercially important fish species. We have used a combination of side-scan sonar mosaics, multibeam bathymetry, and backscatter data, and in situ observations and video from the submersible Delta to investigate marine benthic habitats in the Eastern Gulf of Alaska. The intent of this paper is to review the results of previous marine benthic habitat mapping efforts completed by us along the transform plate boundary of Alaska and to present new information that show how volcanic, plutonic, and glacial submarine geomorphology can be used to identify potentially important discrete habitat areas. Demersal shelf rockfish, a seven-species management complex of nearshore rockfish, including yellow-eye rockfish (Sebastes ruberrimus), are found in rugged and highly rugose geomorphologic features. Eroded volcanic edifices, lava fields, and a pit crater, as well as a small shutterridge, deformed and differentially eroded sedimentary bedrock, and highly fractured and faulted plutonic rock outcrops are features that attract adult rockfish. Volcanic edifices that lie along the leaky (magma-conducting) Fairweather transform fault system intercept ocean currents, in turn producing upward eddies that bring nutrients to species residing on the features. We show that geologic processes such as fault deformation, volcanism, and glaciation are critical to the development of Essential Fish Habitats (EFH) for demersal shelf rockfish. Our work is the first attempt to determine a common geologic link between desperate commercial fishing areas in SE Alaska, USA, and to suggest how tectonic and glacial processes, including sea level rise and transgression, can be used to identify seafloor geologic characteristics as surrogates for marine groundfish habitats. © 2010 Elsevier Ltd., Cited By (since 1996):2, Ecology, Fish and Fisheries, CODEN: CSHRD
Temperature and redox effect on mineral colonization in Juan de Fuca Ridge flank subsurface crustal fluids
Temperature and redox effect on mineral colonization in Juan de Fuca Ridge flank subsurface crustal fluids
To examine microbe-mineral interactions in subsurface oceanic crust, we evaluated microbial colonization on crustal minerals that were incubated in borehole fluids for one year at the seafloor wellhead of a crustal borehole observatory (IODP Hole U1301A, Juan de Fuca Ridge flank) as compared to an experiment that was not exposed to subsurface crustal fluids (at nearby IODP Hole U1301B). In comparison to previous studies at these same sites, this approach allowed assessment of the effects of temperature, fluid chemistry, and/or mineralogy on colonization patterns of different mineral substrates, and an opportunity to verify the approach of deploying colonization experiments at an observatory wellhead at the seafloor instead of within the borehole. The Hole U1301B deployment did not have biofilm growth, based on microscopy and DNA extraction, thereby confirming the integrity of the colonization design against bottom seawater intrusion. In contrast, the Hole U1301A deployment supported biofilms dominated by Epsilonproteobacteria (43.5% of 370 16S rRNA gene clone sequences) and Gammaproteobacteria (29.3%). Sequence analysis revealed overlap in microbial communities between different minerals incubated at the Hole U1301A wellhead, indicating that mineralogy did not separate biofilm structure within the one-year colonization experiment. Differences in the Hole U1301A wellhead biofilm community composition relative to previous studies from within the borehole using similar substrates suggest that temperature and the diffusion of dissolved oxygen through plastic components influenced the mineral colonization experiments positioned at the wellhead. This highlight the capacity of low abundance crustal fluid taxa to rapidly establish communities on diverse mineral substrates under changing environmental conditions such as from temperature and oxygen., Article Number 396
Temperature dependence of nitrate reductase activity in marine phytoplankton: Biochemical analysis and ecological implications
Temperature dependence of nitrate reductase activity in marine phytoplankton: Biochemical analysis and ecological implications
The temperature dependence of NADH:NR activity was examined in several marine phytoplankton species and vascular plants. These species inhabit divergent thermal environments, including the chromophytes Skeletonema costatum (12-15°C), Skeletonema tropicum (18-25°C), Thalassiosira antarctica (-2 to 4°C), and Phaeocystis antarctica (-2 to 4°C), the green alga Dunaliella tertiolecta (14-28°C), and the vascular plants Cucurbita maxima (20-35°C) and Zea mays (20-25°C). Despite the difference in growth habitats, similar temperature response curves were observed among the chromophytic phytoplankton, with temperatures optimal for NR activity being between 10-20°C. In contrast, the chlorophyll b-containing alga and vascular plants exhibited optimal temperatures for NR activity above 30°C. Such dramatic differences in NR thermal characteristics from the two taxonomic groups reflect a divergence in NR structure that may be associated with the evolutionary diversification of chromophytes and chlorophytes. Further, it suggests a potential contribution of the thermal performance of NR to the geographic distributions, seasonal abundance patterns, and species composition of phytoplankton communities. NR partial activities, which assess the individual functions of Mo-pterin and FAD domains, were evaluated on NR purified from S. costatum to determine the possible causes for high temperature (>20°C) inactivation of NR from chromophytes. It was found that the FAD domain and electron transport among redox centers were sensitive to elevated temperatures. S. costatum cells grown at 5, 15, and 25°C exhibited an identical optimal temperature (15°C) for NADH:NR activity, whereas the maximal NR activity and NR protein levels differed and were positively correlated with growth temperature and growth rate. These findings demonstrate that thermal acclimation of NO 3 - reduction capacity is largely at the level of NR protein expression. The consequences of these features on NO 3 - utilization are discussed., Cited By (since 1996):26, Seaweeds, Oceanography, CODEN: JPYLA
Temporal and geographical variation in songs of humpback whales, Megaptera novaeangliae: Synchronous change in Hawaiian and Mexican breeding assemblages
Temporal and geographical variation in songs of humpback whales, Megaptera novaeangliae: Synchronous change in Hawaiian and Mexican breeding assemblages
Humpback whale song, a male breeding display, shows a remarkable degree of similarity among distant breeding assemblages, despite constant progressive change. It has been hypothesized that whales maintain continuity through cultural transmission via migratory movements of males. We examined songs of whales breeding off Hawaii and Mexico to determine whether they changed similarly in both areas during the course of a breeding season. Songs recorded off Kauai, Hawaii (11 individuals) and Isla Socorro, Mexico (13 individuals) during winter and spring of 1991, were compared qualitatively and quantitatively. We measured 44 acoustic variables describing all known levels of song structure for each singer and we grouped these variables into six categories. We used two-factor analyses of variance to assess change across the season in each area, comparing the two regions and two 3-week periods (January/February and April). Twenty-seven variables changed significantly during the 12-week study in at least one area. Variables within categories displayed similar trends of change. Time and frequency characteristics describing the structure of song elements (units and phrases) changed synchronously in each area, with 21 of 25 variables displaying significant differences between periods and no interaction with region. Structures of song patterns, as defined by frequency of occurrence and number of unit and phrase types, changed differently in each area, with five of 12 variables indicating a significant interaction between region and period. Our results may suggest cultural transmission during the season, since many variables changed in similar manners. We propose an alternative hypothesis, that whales may be predisposed to gradually change certain features of song independently of cultural influences; change of structural elements may be governed by a discrete set of rules, or according to an innate template. Therefore, continuity of song patterns across the ocean basin may be due to a combination of mechanisms, only partially involving cultural transmission. We assess these hypotheses in relation to humpback whale behaviour and population structure, and cultural transmission and evolution of avian song. © 2001 The Association for the Study of Animal Behaviour., Cited By (since 1996):40, Marine Mammals, Birds & Turtles, CODEN: ANBEA
Temporal and sex-specific variability in Rhinoceros Auklet diet in the central California Current system
Temporal and sex-specific variability in Rhinoceros Auklet diet in the central California Current system
We used stable isotopes (δ15N and δ13C) and compared prey provided to chicks by each sex to evaluate seasonal and sex-specific diets in Rhinoceros Auklets (Cerorhinca monocerata) in the central California Current system during 2012-2013. Mixing models indicated northern anchovy (Engraulis mordax) were important prey for adults during fall/winter and juvenile rockfishes (Sebastes spp.) were important prey during incubation both years. Adult trophic level increased between incubation and chick-rearing periods in both years. During 2012, δ15N and δ13C of chick-rearing males and females differed significantly; mixing models indicated that females ate more Pacific saury (Cololabis saira) and less market squid (Doryteuthis opalescens) than males. Likewise, females delivered significantly more Pacific saury and less market squid to chicks than males during 2012. Chick growth (g d-1) and chick survival to fledging were significantly lower during 2012 than 2013, likely because chicks were fed lesser quality prey or fed less frequently in 2012. Lesser body mass of females during incubation in 2012 indicated sex-specific diet differences may have been related to female energetic constraints. The observed variability in Rhinoceros Auklet diet underscores the importance of managing multiple prey populations in this system so that generalist predators have sufficient resources through changing conditions. © 2014 Elsevier B.V., Cited By :1, Export Date: 4 September 2015
Temporal and sex-specific variability in Rhinoceros Auklet diet in the central California Current system
Temporal and sex-specific variability in Rhinoceros Auklet diet in the central California Current system
We used stable isotopes (δ 15N and δ13C) and compared prey provided to chicks by each sex to evaluate seasonal and sex-specific diets in Rhinoceros Auklets (Cerorhinca monocerata) in the central California Current system during 2012-2013. Mixing models indicated northern anchovy (Engraulis mordax) were important prey for adults during fall/winter and juvenile rockfishes (Sebastes spp.) were important prey during incubation both years. Adult trophic level increased between incubation and chick-rearing periods in both years. During 2012, δ 15N and δ13C of chick-rearing males and females differed significantly; mixing models indicated that females ate more Pacific saury (Cololabis saira) and less market squid (Doryteuthis opalescens) than males. Likewise, females delivered significantly more Pacific saury and less market squid to chicks than males during 2012. Chick growth (g d-1) and chick survival to fledging were significantly lower during 2012 than 2013, likely because chicks were fed lesser quality prey or fed less frequently in 2012. Lesser body mass of females during incubation in 2012 indicated sex-specific diet differences may have been related to female energetic constraints. The observed variability in Rhinoceros Auklet diet underscores the importance of managing multiple prey populations in this system so that generalist predators have sufficient resources through changing conditions.
Temporal and spatial patterns in abundance and diversity of fish assemblages in Elkhorn Slough, California
Temporal and spatial patterns in abundance and diversity of fish assemblages in Elkhorn Slough, California
Assemblages of ichthyofauna of shallow inshore habitats along Californía's central coast are described in terms of species composition, abundance, and life-style categories. A total of 22,334 fishes from 65 species and 27 families was collected with otter trawls at six sites in the main channel and tidal creeks of Elkhorn Slough, a tidal embayment and seasonal estuary, and two nearshore ocean stations in Monterey Bay during 44 months between August 1974 and June 1980. Greater than 90% of the catch comprised 10 species. The four dominant species, Cymatogaster aggregata, Leptocottus armatus, Phanerodon furcatus, and Embiotoca jacksoni, occurred during most or all seasons and were classified as residents or partial residents. Several abundant species were marine immigrants that seasonally use the slough as spawning and nursery grounds; this resulted in higher abundance and species richness during summer. Species collected during winter largely were slough residents. Species compsosition and richness varied with distance from the slough entrance. The ocean assemblage was most different, and its similarity to other stations decreased progressively with distance inland and into the tidal creeks. During our study, 5,074 fishes were collected by beach seine in Bennett Slough, a remote shallow marsh basin adjacent to the entrance of Elkhorn Slough. Species richness was relatively low and three euryhaline species accounted for >80% of the total catch. The species assemblage was most similar to those at the tidal creek and most shallow stations of Elkhorn Slough. Resident species numerically dominated assemblages in Bennett Slough and the most inland areas of Elkhorn Slough. The high relative abundance of marine-related fishes (classified as marine, marine immigrant, and partial resident), entering Elkhorn Slough early in life or as spawning adults indicates the importance of this habitat to nearshore fish assemblages. © 1991 Estuarine Research Federation., Cited By (since 1996):32, Fish and Fisheries, CODEN: ESTUD
Temporal and spatial trends in sediment contaminants associated with toxicity in California watersheds
Temporal and spatial trends in sediment contaminants associated with toxicity in California watersheds
Abstract California's Stream Pollution Trends program (SPoT) assesses long-term water quality trends, using 100 base-of-the-watershed sampling sites. Annual statewide sediment surveys from 2008 to 2012 identified consistent levels of statewide toxicity (19%), using the freshwater amphipod Hyalella azteca. Significant contaminant trends included a decrease in PCBs, stable concentrations of metals and PAHs, and a statewide increase in detections and concentrations of pyrethroid pesticides. The pyrethroid pesticide bifenthrin was detected in 69% of samples (n = 410). Detection of toxicity increased in a subset of samples tested at a more environmentally relevant test temperature (15 °C), and the magnitude of toxicity was much greater, indicating pyrethroid pesticides as a probable cause. Pyrethroid toxicity thresholds (LC50) were exceeded in 83% of samples with high toxicity. Principal components analysis related pyrethroids, metals and total organic carbon to urban land use.
Temporal changes in deep-sea sponge populations are correlated to changes in surface climate and food supply
Temporal changes in deep-sea sponge populations are correlated to changes in surface climate and food supply
Density and average size of two species of abyssal sponges were analyzed at Station M (~4100. m depth) over an 18-year time-series (1989-2006) using camera sled transects. Both sponge taxa share a similar plate-like morphology despite being within different families, and both showed similar variations in density and average body size over time, suggesting that the same factors may control the demographics of both species. Peaks in significant cross correlations between increases in particulate organic carbon flux and corresponding increases in sponge density occurred with a time lag of 13 months. Sponge density also fluctuated with changes in two climate indices: the NOI with a time lag of 18 months and NPGO with a time lag of 15 months. The results support previous suggestions that increased particulate organic carbon flux may induce recruitment or regeneration in deep-sea sponges. It is unknown whether the appearance of young individuals results from recruitment, regeneration, or both, but the population responses to seasonal and inter-annual changes in food supply demonstrate that sponge populations are dynamic and are capable of responding to inter-annual changes despite being sessile and presumably slow-growing. © 2012 Elsevier Ltd., Cited By (since 1996):4, Export Date: 24 September 2013, Source: Scopus, CODEN: DRORE
Temporal changes in marine environments in the Antarctic Peninsula area during the 1994/95 austral summer
Temporal changes in marine environments in the Antarctic Peninsula area during the 1994/95 austral summer
To reveal the temporal changes in Antarctic marine environments during the 1994/95 austral summer, oceanographic surveys were carried out in the Antarctic Peninsula area by Germany, Japan, Korea, and the USA. Five oceanographic stations at 15 nautical mile intervals were selected north of Elephant Island along 55°W; water temperature, salinity, nutrients, phytoplankton, krill and other zooplankton, and acoustic backscatter were sampled by similar sampling protocols. The transect was surveyed six times during the austral summer, from early December 1994 to late February 1995. The major findings from this time-series were : 1) The north/south position of the oceanic frontal zone north of Elephant Island along 55°W varied by 15 nautical miles; the northeasterly current associated with this front, determined by geostrophy, varied in strength depending on position of the front; 2) Most chl-a was concentrated in the upper 50m above or near the pycnocline. Surface chl-a concentrations ranged from 0.5mg/m^3 to >3.5mg/m^3. Peak chl-a (3.62mg/m^3) was found in the surface water during 18 February 1995. 3) Krill spawning during the 1994/95 season was early, extensive and apparently successful compared to previous years; and 4) Taxa other than krill may have contributed substantially to the observed acoustic backscattering.
Temporal stability and origin of chemoclines in the deep hypersaline anoxic Urania basin
Temporal stability and origin of chemoclines in the deep hypersaline anoxic Urania basin
Submarine brine lakes feature sharp and persistent concentration gradients between seawater and brine, though these should be smoothed out by free diffusion in open ocean settings. The anoxic Urania basin of the eastern Mediterranean contains an ultrasulfidic, hypersaline brine of Messinian origin above a thick layer of suspended sediments. With a dual modeling approach we reconstruct its contemporary stratification by geochemical solute transport fundamentals and show that thermal convection is required to maintain mixing in the brine and mud layer. The origin of the Urania basin stratification was dated to 1650 years B.P., which may be linked to a major earthquake in the region. The persistence of the chemoclines may be key to the development of diverse and specialized microbial communities. Ongoing thermal convection in the fluid mud layer may have important yet unresolved consequences for sedimentological and geochemical processes, also in similar environments. © 2015. American Geophysical Union. All Rights Reserved., Export Date: 19 February 2016, Article
Temporal stability and origin of chemoclines in the deep hypersaline anoxic Urania basin
Temporal stability and origin of chemoclines in the deep hypersaline anoxic Urania basin
Submarine brine lakes feature sharp and persistent concentration gradients between seawater and brine, though these should be smoothed out by free diffusion in open ocean settings. The anoxic Urania basin of the eastern Mediterranean contains an ultrasulfidic, hypersaline brine of Messinian origin above a thick layer of suspended sediments. With a dual modeling approach we reconstruct its contemporary stratification by geochemical solute transport fundamentals and show that thermal convection is required to maintain mixing in the brine and mud layer. The origin of the Urania basin stratification was dated to 1650 years B.P., which may be linked to a major earthquake in the region. The persistence of the chemoclines may be key to the development of diverse and specialized microbial communities. Ongoing thermal convection in the fluid mud layer may have important yet unresolved consequences for sedimentological and geochemical processes, also in similar environments. © 2015. American Geophysical Union. All Rights Reserved., Export Date: 11 December 2015
Temporal variability in ocean climate and California sea lion diet and biomass consumption: Implications for fisheries management
Temporal variability in ocean climate and California sea lion diet and biomass consumption: Implications for fisheries management
Key to understanding ecosystem structure and function in the California Current System is quantitative modeling of trophic interactions of California sea lions Zalophus californianus, one of the largest and most abundant predators in this system, and how these interactions are affected by climate variability. Because sea lions consume almost exclusively commercially important prey species, we hypothesized that the potential for competition for specific prey resources would vary with environmental conditions. We evaluated seasonal and annual variation in sea lion diet in Monterey Bay during the strong 1997-98 El Niño and subsequent 1999 La Niña through the examination and identification of prey hard parts found in fecal samples. Annual consumption was modeled using population size, dietary data, sea lion energetics, and prey energy content. Sea lions were plastic specialists, feeding on seasonally abundant aggregating prey, exploiting several species at a time. Short-term seasonal changes in diet corresponded with prey movement and life history patterns, whereas long-term annual changes corresponded with large-scale ocean climate shifts, namely the large 1997-98 El Niño and 1999 La Niña. Annual sea lion consumption of specific prey varied as a function of ocean climate, with an estimated 17 154 t prey consumed in 1998 and 20 229 t in 1999. Sea lion consumption was similar in magnitude to fisheries landings for several prey species and has the potential to adversely impact specific prey resources and directly compete with these fisheries; however, the degree of competition depends on spatial and temporal overlap of fisheries and sea lion foraging efforts. © Inter-Research 2008., Cited By (since 1996):8, Marine Mammals, Birds & Turtles, CODEN: MESED, Downloaded from: http://www.int-res.com/abstracts/meps/v373/p157-172/ (16 June 2014).
Temporal variation and succession in an algal-dominated high intertidal assemblage
Temporal variation and succession in an algal-dominated high intertidal assemblage
We determined whether temporal variation and succession were similar among sites with similar species composition by sampling unmanipulated and cleared plots in a high intertidal assemblage dominated by Endocladia muricata and Mastocarpus papillatus. Sampling was done for 6 years at six sites spanning over 4° of latitude in California. Ten 1 × 2-m permanent plots were chosen in the central portion of the assemblage at each site. Four of these served as unmanipulated controls, three were cleared (scraped and burned) in the spring of 1985, and three were cleared in the fall of 1985. The cover of sessile and density of motile species were determined by subsampling within the plots from 1985 until 1991. Recovery of the clearings was determined by their similarity to the controls. The algae E. muricata, M. papillatus, and Fucus gardneri, and the barnacle Balanus glandula, were the most abundant sessile organisms in the control plots, although the latter never exceeded 12% cover at any site. The grazing gastropods Littorina scutulata/plena, various limpets, and Tegula funebralis were the most common mobile organisms. The species composition of the common species remained constant in the control plots over the study period and there were few large changes in relative abundance. Significant seasonal variation was detected in 11 species but variation was commonly site-specific. Ephemeral algae were abundant during early succession at only two of the six sites, and barnacle cover was low (< 15% cover) at four sites and moderate (15-50% cover) at the remaining two throughout succession. Recovery rate varied considerably among sites and between times of clearing (1-10%/month). Correlations between ephemeral algae and grazer abundance, and between these variables and recovery rate were not significant. The effects of grazers on recovery rate were only evident at one site where they appeared to reduce an initially high cover of ephemeral algae and delay the establishment of perennials. Some of the largest differences in recovery rate were between clearing times, associated with differences in the phenology of the dominant perennial algae. In spite of these differences, most plots recovered by the end of the study period. These results indicate that the assemblages in the control plots at each site were relatively stable and, while successional pathways and processes varied, the assemblage at most sites still recovered. Current models, based largely on biological interactions, that attempt to explain within assemblage structure and succession were not broadly applicable. © 2003 Elsevier Science B.V. All rights reserved., Cited By (since 1996):31, Seaweeds, CODEN: JEMBA

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