Articles

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


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U.S. "Mussel watch" 1976-1978: An overview of the trace-metal, DDE, PCB, hydrocarbon, and artificial radionuclide data
U.S. "Mussel watch" 1976-1978: An overview of the trace-metal, DDE, PCB, hydrocarbon, and artificial radionuclide data
Data are presented for trace metals, polychlorinated biphenyls (PCBs), aromatic hydrocarbons and 239,240Pu in Mytilus edulis, M. californianus, and Crassostrea sp. colected in the U.S. Mussel Watch program in 1976-1978 from 62 locations on the U.S. east and west coasts. General similarities in geographical distributions of concentrations were present in all 3 years with at least an order of magnitude elevation of concentrations of Pb, PCBs, and fossil fuel hydrocarbons in bivalves sampled near the larger urban areas. Elevated Cd and 239,240Pu concentrations in bivalves from the central California coast are apparently related to enrichments of Cd and nuclear weapons testing fallout 239,240Pu in intermediate depth water of the North Pacific and upwelling of this water associated with the California Current system. Our data have revealed no evidence of local or regional systematic elevations of environmental concentrations of 239,240Pu as a result of effluent releases from nuclear power reactors. © 1983 American Chemical Society., Cited By (since 1996):159
Underwater sound measurements of a high-speed jet-propelled marine craft
Underwater sound measurements of a high-speed jet-propelled marine craft
Radiated noise from a high-speed jet-propelled watercraft (the M/V Alakai, 1,646 tons, length 117 m) was measured at hydrophone depths of 3, 6, and 10 m while the ship passed by at speeds of 6.1733 m/sec (12 knots), 12.3467 m/sec (24 knots), and 19.0344 m/sec (37 knots). Noise spectra were similar for all speeds and hydrophone depths. Spectra peaked below 100 Hz and dropped off continuously at higher frequencies. Calculated source level noise was 10 to 20 dB lower than noise from propeller-driven ships and much lower than for ships of similar speed. Although exposure to noise radiating from the M/V Alakai over short time periods is unlikely to cause hearing damage to whales, the combination of low radiated noise levels and high transit speeds leads to a shorter closing time (defined as time between when source level of the ship at a stationary receiver is greater than ambient noise and time that a ship traveling directly toward the receiver arrives at its location) between ship and whale. Compared with other types of ships traveling at similar speeds, closing time for the Alakai ranges from 20 sec shorter (at 6.17333 m/sec [12 knots]) to 22 min shorter (at 19.0344 m/sec [37 knots]). Shortest closing time for the Alakai is 89.1 sec at a speed of 6.17333 m/sec (12 knots). Shortened closing time might reduce successful detection and avoidance of high-speed jet-propelled ships by whales, and increased speed shortens the time during which whales have the opportunity to respond to this detection.
Unnatural selection of antarctic toothfish in the Ross Sea, Antarctica
Unnatural selection of antarctic toothfish in the Ross Sea, Antarctica
The Antarctic Treaty Consultative Powers formed the Convention for the Conservation of Antarctic Marine Living Resources (CCAMLR) in 1982, a Commission charged with the wise management of the biotic resources of the Antarctic, south of 60oS. As a fishery treaty, CCAMLR has been ahead of its time, despite operating on the basis of consensus - a modus operandi generally not fairing well in the management of fisheries elsewhere (Longhurst 2010). Besides regulating fish catches, CCAMLR has accomplished the establishment of several legislations towards the protection of Antarctic marine living resources, such as the ban of gill nets and bottom trawling, and the protection of shallow-water benthic communities. On the other hand, current Antarctic fisheries management largely depends on mathematical models to determine catch rates, but these models frequently fail in the absence of adequate and accurate life history data and ecological information for the target species. In 1996, CCAMLR opened an exploratory fishery for Antarctic toothfish (Dissostichus mawsoni) in the Ross Sea with the aim of reducing the spawning biomass to 50% in the next 35 years. This fishery is managed in the absence of crucial data on life history and ecology. Here we provide a summary of what is currently known about Antarctic toothfish life history and its ecological role in the Ross Sea. Further, by drawing parallels to other fisheries targeting long-lived, deep-sea fish, we review problems with the current management of this fishery and provide suggestions for better management. We urge that until more is known about basic life history of Antarctic toothfish and its ecological role in the Ross Sea, managers would be wise to apply a more precautionary fishery management approach. © 2012 Springer. All rights are reserved., Cited By :3, Export Date: 26 June 2015
Unusual coastal flood impacts in Salmon Valley, McMurdo Sound, Antarctica
Unusual coastal flood impacts in Salmon Valley, McMurdo Sound, Antarctica
Large floods bringing significant sediments into the coastal oceans have not been observed in Antarctica. We report evidence of a large flood event depositing over 50 cm of sediment onto the nearshore benthic habitat at Salmon Bay, Antarctica, between 1990 and 2010. Besides direct observations of the sedimentation, the evidence involves a debris flow covering old tyre tracks from the early 1960s, as well as evidence of a considerable amount of sediment transported onto the Salmon Creek delta. We believe that the flood was sourced from the Salmon Glacier and possibly the smaller Blackwelder Glacier. Such floods will be more common in the future and it is important to better understand their ecological impacts with good monitoring programmes. © Antarctic Science Ltd 2016, Export Date: 13 May 2016, Article in Press
Unusual kinematics and jaw morphology associated with piscivory in the poeciliid, Belonesox belizanus
Unusual kinematics and jaw morphology associated with piscivory in the poeciliid, Belonesox belizanus
Piscivory in fishes is often associated with the evolution of highly elongate jaws that achieve a large mouth opening, or gape. Belonesox belizanus, the pike killifish, has independently evolved this morphology, which is derived from short-jawed poeciliids within the Cyprinodontiformes. Using kinematic analysis of high-speed video footage, we observed a novel aspect of the elongate jaws of Belonesox; the premaxilla rotates dorsally during mouth opening, while the lower jaw rotates ventrally. Anatomical study revealed that this unusual motion is facilitated by the architecture of the premaxillomandibular ligament, prominent within cyprinodontiforms. In Belonesox, it allows force to be transferred from the lower jaw directly to the premaxilla, thereby causing it to rotate dorsally. This dorsal rotation of the premaxilla appears to be assisted by a mediolateral twisting of the maxilla during jaw opening. Twisting maxillae are found in members of the group such as Fundulus, but are lost in Gambusia. Models revealed that elongate jaws partially account for the enlarged gape, but enhanced rotation at the quadrato-mandibular joint was equally important. The large gape is therefore created by: (i) the convergent evolution of elongate jaws; (ii) enhanced jaw rotation, facilitated by loss of a characteristic cyprinodontiform trait, the lip membrane; and (iii) premaxilla rotation in a novel direction, facilitated by the retention and co-option of additional cyprinodontiform traits, the premaxillomandibular ligament and a twisting maxilla. © 2010 Elsevier GmbH., Cited By (since 1996):2, Fish and Fisheries
Upwelling age: An indicator of local tendency for coastal upwelling
Upwelling age: An indicator of local tendency for coastal upwelling
A proxy named "upwelling age", defined as the ratio of wind time scale to "advection time", was developed to quantify the local tendency for coastal upwelling. The formulation of the "advection time" was derived from Ekman theory. A 3D numerical model was used to validate and refine the theoretical formula by simulating a total of 30 cases of different bottom topographies and wind stresses. The results agree reasonably well with the theoretical formulation although some modifications are necessary. The final formulation of the "advection time" was parameterized as a function of pycnocline depth, bottom slope, and wind stress. © 2011 The Oceanographic Society of Japan and Springer., Cited By (since 1996):1, Oceanography
Upwelling rebound, ephemeral secondary pycnoclines, and the creation of a near-bottom wave guide over the Monterey Bay continental shelf
Upwelling rebound, ephemeral secondary pycnoclines, and the creation of a near-bottom wave guide over the Monterey Bay continental shelf
Several sequential upwelling events were observed in fall 2012, using measurements from the outer half of the continental shelf in Monterey Bay, during which the infiltration of dense water onto the shelf created a secondary, near-bottom pycnocline. This deep pycnocline existed in concert with the near-surface pycnocline and enabled the propagation of near-bottom, cold, semidiurnal internal tidal bores, as well as energetic, high-frequency, nonlinear internal waves of elevation (IWOE). The IWOE occurred within 20 m of the bottom, had amplitudes of 8-24 m, periods of 6-45 min, and depth-integrated energy fluxes up to 200 W m-1. Iribarren numbers (<0.03) indicate that these IWOE were nonbreaking in this region of the shelf. These observations further demonstrate how regional upwelling dynamics and the resulting bulk, cross-margin hydrography is a first-order control on the ability of internal waves, at tidal and higher frequencies, to propagate through continental shelf waters., Oceanography
Use of acoustic tags to estimate natural mortality, spillover, and movements of lingcod (Ophiodon elongatus) in a marine reserve
Use of acoustic tags to estimate natural mortality, spillover, and movements of lingcod (Ophiodon elongatus) in a marine reserve
Advances in electronic telemetry systems have led to fish tagging studies that are sufficiently long to provide estimates of natural mortality of many marine fishes. We used acoustic transmitters and an array of recording receivers to estimate natural mortality, residence times, and rates of movements of lingcod (Ophiodon elongatus) in a marine reserve in southeast Alaska. We surgically implanted acoustic tags in a total of 83 lingcod in December 1999 and July 2000, and distributed recording monitors with receiving ranges of at least 800 m throughout the reserve. The receivers were anchored on the seafloor in locations that resulted in overlapping receiving ranges, and thus created an array of receivers that completely encompassed an 8 km 2 reserve. In this way, we were able to estimate natural mortality rates and track movements of tagged lingcod into and out of the reserve from December 1999 through October 2001. Acoustic tag results indicated that most of the tagged fish frequently left the reserve, but were only absent for short time periods. Tagged fish showed a high degree of site fidelity. The large number of signals received from tagged fish enabled us to generate models that provided a way to predict the effects of marine reserves on yield and eggs per recruit for a cohort of female lingcod., Cited By (since 1996):8, Fish and Fisheries
Using Digital Tags With Integrated Video and Inertial Sensors to Study Moving Morphology and Associated Function in Large Aquatic Vertebrates
Using Digital Tags With Integrated Video and Inertial Sensors to Study Moving Morphology and Associated Function in Large Aquatic Vertebrates
The anatomy of large cetaceans has been well documented, mostly through dissection of dead specimens. However, the difficulty of studying the world's largest animals in their natural environment means the functions of anatomical structures must be inferred. Recently, non-invasive tracking devices have been developed that measure body position and orientation, thereby enabling the detailed reconstruction of underwater trajectories. The addition of cameras to the whale-borne tags allows the sensor data to be matched with real-time observations of how whales use their morphological structures, such as flukes, flippers, feeding apparatuses, and blowholes for the physiological functions of locomotion, feeding, and breathing. Here, we describe a new tag design with integrated video and inertial sensors and how it can be used to provide insights to the function of whale anatomy. This technology has the potential to facilitate a wide range of discoveries and comparative studies, but many challenges remain to increase the resolution and applicability of the data. Anat Rec, 300:1935–1941, 2017.
Using accelerometers to determine the calling behavior of tagged baleen whales
Using accelerometers to determine the calling behavior of tagged baleen whales
Low-frequency acoustic signals generated by baleen whales can propgate over vast distances, making the assignment of calls to specific individuals problematic. Here, we report the novel use of acoustic recording tags equipped with high-resolution accelerometers to detect vibrations from the surface of two tagged fin whales that directly match the timing of recorded acoustic signals. A tag deployed on a buoy in the vicinity of calling fin whales and a recording from a tag that had just fallen off a whale were able to detect calls acoustically but did not record corresponding accelerometer signals that were measured on calling individuals. Across the hundreds of calls measured on two tagged fin whales, the accelerometers response was generally anisotropic across all three axes, appeared to depend on tag placement and increased with the level of received sound. These data demonstrate that high-sample rate accelerometry can provide important insights into the acoustic behavior of baleen whales that communicate at low frequencies. This method helps identify vocalizing whales, which in turn enables the quantification of call rates, a fundamental component of models used to estimate baleen whale abundance and distribution from passive acoustic monitoring.
Using bomb radiocarbon analyses to validate age and growth estimates for the tiger shark, Galeocerdo cuvier, in the western North Atlantic
Using bomb radiocarbon analyses to validate age and growth estimates for the tiger shark, Galeocerdo cuvier, in the western North Atlantic
Refined and validated age and growth determinations are necessary for a proper understanding of tiger shark (Galeocerdo cuvier) life history characteristics in the western North Atlantic (WNA). Age and growth estimates were derived from band counts of 238-sectioned vertebral centra. Bomb radiocarbon analysis of ten band pairs extracted from four vertebral sections suggested that band pairs are deposited annually up to age 20. Males and females were aged to 20 and 22 years, respectively, although longevity estimates predict maximum ages of 27 and 29 years, respectively. Two- and three-parameter von Bertalanffy and Gompertz growth functions fit to length at age data demonstrated that growth rates were similar for males and females up to around 200 cm fork length (FL) after which male growth slowed. Both sexes appear to reach maturity at age 10. The two-parameter von Bertalanffy growth function provided the best biological fit to length at age data generating parameter estimates of: L ∞ = 330 cm FL, k = 0.131 for males and L ∞ = 347 cm FL, k = 0.124 for females, with L 0 set at 62 cm FL. This study provides a rigorous description of tiger shark age and growth in the WNA and further demonstrates the utility of bomb radiocarbon as an age validation tool for elasmobranch fish. © 2008 Springer-Verlag., Cited By (since 1996):6, Fish and Fisheries, CODEN: MBIOA
Using carapace measurements to determine the sex of Antarctic krill, Euphausia superba
Using carapace measurements to determine the sex of Antarctic krill, Euphausia superba
Krill (Euphausia superba) carapace measurements (length and width; mm) collected from plankton tows in the South Shetland Islands (SSI), Antarctica are used to test the generality of a common discriminant function developed to reconstruct krill length frequencies in Antarctic fur seal diets for the area surrounding South Georgia (SG). Total length and sex ratio of krill in the SSI were overestimated by 5.6 and 154%, respectively, when the SG allometric equations were applied to 3 years (2003-2005) of data. These errors arise and increase as a result of krill population dynamics, specifically recruitment that contributes large proportions of immature krill, misclassified as males by the SG discriminant function. We develop sex-specific regression models based on separate discriminant functions that provide significantly better discriminatory power. However, our analysis indicates that reconstructions of krill sex ratio and length composition in the ocean environment are less reliable in years when the ratio of immature to mature krill is high. For the SSI area, five out of 14 years (35.7%) surveyed (1992-2005) had proportions of immature to mature adult krill ≥ 0.50. © 2006 Springer-Verlag., Cited By (since 1996):2, CODEN: POBID
Using in situ substratum sterilization and fluorescence microscopy in studies of microscopic stages of marine macroalgae
Using in situ substratum sterilization and fluorescence microscopy in studies of microscopic stages of marine macroalgae
The methods currently used for examining the relative contribution of microscopic stages to the persistence of natural populations of marine macroalgae can be inappropriate for use in subtidal habitats. Also, because of their microscopic size, direct examination and obtaining an estimate of recruitment, growth and mortality of these stages in the field is difficult. A method of removing microscopic algal stages from natural rock surfaces using watertight tents and water-soluble chemicals is presented. Also discussed is the use of a previously described method of fluorescent labelling these microscopic stages that, when examined under UV light, allows for their precise identification and growth to be determined. Together, these methods can be effective in examining the ecology of algal microscopic stages in the field., Cited By (since 1996):1, Seaweeds, CODEN: HYDRB
Using paired visual and passive acoustic surveys to estimate passive acoustic detection parameters for harbor porpoise abundance estimates
Using paired visual and passive acoustic surveys to estimate passive acoustic detection parameters for harbor porpoise abundance estimates
Passive acoustic monitoring is a promising approach for monitoring long-term trends in harbor porpoise (Phocoena phocoena) abundance. Before passive acoustic monitoring can be implemented to estimate harbor porpoise abundance, information about the detectability of harbor porpoise is needed to convert recorded numbers of echolocation clicks to harbor porpoise densities. In the present study, paired data from a grid of nine passive acoustic click detectors (C-PODs, Chelonia Ltd., United Kingdom) and three days of simultaneous aerial line-transect visual surveys were collected over a 370 km2 study area. The focus of the study was estimating the effective detection area of the passive acoustic sensors, which was defined as the product of the sound production rate of individual animals and the area within which those sounds are detected by the passive acoustic sensors. Visually estimated porpoise densities were used as informative priors in a Bayesian model to solve for the effective detection area for individual harbor porpoises. This model-based approach resulted in a posterior distribution of the effective detection area of individual harbor porpoises consistent with previously published values. This technique is a viable alternative for estimating the effective detection area of passive acoustic sensors when other experimental approaches are not feasible.
Using stable isotopes to investigate foraging variation and habitat use of sperm whales from northern Peru
Using stable isotopes to investigate foraging variation and habitat use of sperm whales from northern Peru
Article, Female sperm whales Physeter macrocephalus are top predators in mesopelagic ecosystems, integrating chemical information about ecosystems through their diet. Proxies for diet and habitat use may be useful to learn about how sperm whales' foraging behavior and environment change through time. We measured stable isotopes of carbon (δ13C) and nitrogen (δ15N) from individual growth layer groups from the teeth of 10 female sperm whales, to track changes in diet and habitat use from ca. 1926 to 1960. We found that bulk δ13C and δ15N records fell into 3 temporal patterns, which may indicate different ontogenetic changes in diet, habitat, or both. Average bulk δ13C and δ15N values for each tooth were positively correlated, and individual whales generally separated according to temporal patterns. To determine the underlying driver of the bulk relationship, we measured δ13C and δ15N values from individual amino acids (AAs) in a subset of samples. AA isotope results indicated that the bulk isotopic trend was due to baseline differences. Specifically, whales from each identified pattern likely used different feeding regions, but had similar trophic positions. This conclusion is supported by the relationships between bulk and compound-specific AA isotope values for both nitrogen and carbon. We suggest that these female sperm whales inhabiting northern Peruvian waters had 3 different lifelong foraging strategies, having the same trophic position but feeding overall in different regions. These results provide novel insights into social bonds among female sperm whales, since whales with similar foraging patterns likely shared the same habitat and diet over their lifetime, whereas whales with different foraging strategies had separate trophic niches.
Using the Turner Designs model 10 Analog, the 10 AU Digital, or the TD-700 fluorometer with EPA method 445.0
Using the Turner Designs model 10 Analog, the 10 AU Digital, or the TD-700 fluorometer with EPA method 445.0
The United States Environmental Protection Agency (EPA) has recently published a chlorophyll method, Method 445.0, rev 1.2. Method 4450 describes the use of a Turner Designs Model 10Series Fluorometer (Section 61)? This fluorometer has been redesigned to make it easier to use. It is now called the Turner Designs Model 10-AU Fluorometer. The Model 10-AU is digital and is capable of performing calculations formerly done by the user ...
Using the molecular toolbox to compare harmful algal blooms in upwelling systems
Using the molecular toolbox to compare harmful algal blooms in upwelling systems
Harmful algal blooms (HABs) are now generally recognized as occurring over a wide range of habitats from oligotrophic to hypernutrified, and appear to be expanding globally. Unlike many other ecosystems impacted by HABs, upwelling systems worldwide share a common set of physical parameters and are likely to respond similarly, regardless of locale. The Core Research Project on HABs in Upwelling Systems, a component of the scientific programme on the Global Ecology and Oceanography of Harmful Algal Blooms (GEOHAB), promotes a comparative approach to identify the similarities and differences in the manifestation of HAB events in these systems. As applied to the goals of this programme, molecular techniques are a powerful suite of tools for HAB species identification, for determining genetic similarity within morphologically indistinguishable species, and ultimately, for assessing spatial and temporal patterns in ecophysiological responses in these upwelling systems. Knowledge of HAB organisms will be enhanced by comparing and contrasting the responses of these organisms in similar upwelling regions. Here, we provide an update on the availability of molecular and genetic tools for comparative HAB programmes in upwelling systems, focusing on four broad applications: cell enumeration and identification, molecular phylogenetics, functional/comparative genomics, and applications of high throughput sequencing methods. We highlight the rapid evolution, the promise, and the potential pitfalls, of the molecular toolbox, focusing on specific examples of how scientists and resource managers currently apply these methods. Specific examples are developed using relevant case studies from the California, Benguela and Iberian systems. We summarise by providing a synthesis of future research directions and goals that would be particularly relevant to advancing the comparative method for HAB genetics with an emphasis on upwelling systems. © 2010 Elsevier Ltd. All rights reserved., Cited By (since 1996):6, CODEN: POCNA, Oceanography
Using x-ray microscopy and Hg L3 XANES to study Hg binding in the rhizosphere of spartina cordgrass
Using x-ray microscopy and Hg L3 XANES to study Hg binding in the rhizosphere of spartina cordgrass
San Francisco Bay has been contaminated historically by mercury from mine tailings as well as contemporary industrial sources. Native Spartina foliosa and non-native S. alterniflora-hybrid cordgrasses are dominant florae within the SF Bay estuary environment. Understanding mercury uptake and transformations in these plants will help to characterize the significance of their roles in mercury biogeochemical cycling in the estuarine environment. Methylated mercury can be biomagnified up the food web, resulting in levels in sport fish up to 1 million times greater than in surrounding waters and resulting in advisories to limit fish intake. Understanding the uptake and methylation of mercury in the plant rhizosphere can yield insight into ways to manage mercury contamination. The transmission X-ray microscope on beamline 6-2 at the Stanford Synchrotron Radiation Lightsource (SSRL) was used to obtain absorption contrast images and 3D tomography of Spartina foliosa roots that were exposed to 1 ppm Hg (as HgCl2) hydroponically for 1 week. Absorption contrast images of micrometer-sized roots from S. foliosa revealed dark particles, and dark channels within the root, due to Hg absorption. 3D tomography showed that the particles are on the root surface, and slices from the tomographic reconstruction revealed that the particles are hollow, consistent with microorganisms with a thin layer of Hg on the surface. Hg L3 XANES of ground-up plant roots and Hg L3 micro-XANES from microprobe analysis of micrometer-sized roots (60-120 μm in size) revealed three main types of speciation in both Spartina species: Hg-S ligation in a form similar to Hg(II) cysteine, Hg-S bonding as in cinnabar and metacinnabar, and methylmercury- carboxyl bonding in a form similar to methylmercury acetate. These results are interpreted within the context of obtaining a "snapshot" of mercury methylation in progress. © 2009 American Chemical Society., Cited By (since 1996):27, CODEN: ESTHA
Utilizing fishermen knowledge and expertise: Keys to success for collaborative fisheries research
Utilizing fishermen knowledge and expertise: Keys to success for collaborative fisheries research
Collaborative fisheries research provides a mechanism for integrating the unique knowledge, experience, and skills of fishermen and scientists. It is a joint intellectual endeavor that begins with the inception of a project and continues until its final stages, with each group having mutual investment in-and ownership of- the project. Collaborative fisheries research promotes communication and trust among fishermen, scientists, and managers and can provide much-needed scientifically valid data for fisheries management. It can enhance federal and state management data collection programs, which span broad sections of coastline, by increasing the ability to detect changes in local metapopulations that may be overfished or underutilized. We describe a methodology for conducting collaborative fisheries surveys and apply it to marine protected areas along the central California coast. During a series of workshops in 2006, attended by members of the fishing, academic, environmental, and management communities, protocols were established for conducting hook-and-line surveys collaboratively with commercial passenger fishing vessel captains and volunteer recreational anglers. The protocols have been implemented annually since 2007. This case study highlights the effectiveness of-and the essential steps in-developing our collaborative fisheries research and monitoring projects., Cited By (since 1996):1, Fish and Fisheries
Utilizing spatial demographic and life history variation to optimize sustainable yield of a temperate sex-changing fish
Utilizing spatial demographic and life history variation to optimize sustainable yield of a temperate sex-changing fish
Fish populations vary geographically in demography and life history due to environmental and ecological processes and in response to exploitation. However, population dynamic models and stock assessments, used to manage fisheries, rarely explicitly incorporate spatial variation to inform management decisions. Here, we describe extensive geographic variation in several demographic and life history characteristics (e.g., size structure, growth, survivorship, maturation, and sex change) of California sheephead (Semicossyphus pulcher), a temperate rocky reef fish targeted by recreational and commercial fisheries. Fish were sampled from nine locations throughout southern California in 2007-2008. We developed a dynamic size and age-structured model, parameterized separately for each location, to assess the potential cost or benefit in terms of fisheries yield and conservation objectives of changing minimum size limits and/or fishing mortality rates (compared to the status quo). Results indicate that managing populations individually, with location-specific regulations, could increase yield by over 26% while maintaining conservative levels of spawning biomass. While this local management approach would be challenging to implement in practice, we found statistically similar increases in yield could be achieved by dividing southern California into two separate management regions, reflecting geographic similarities in demography. To maximize yield, size limits should be increased by 90 mm in the northern region and held at current levels in the south. We also found that managing the fishery as one single stock (the status quo), but with a size limit 50 mm greater than the current regulations, could increase overall fishery yield by 15%. Increases in size limits are predicted to enhance fishery yield and may also have important ecological consequences for the predatory role of sheephead in kelp forests. This framework for incorporating demographic variation into fisheries models can be exported generally to other species and may aid in identifying the appropriate spatial scales for fisheries management. © 2011 Hamilton et al., Cited By (since 1996):3, Fish and Fisheries, Art. No.: e24580
VERTEX biological implications of total attenuation
VERTEX biological implications of total attenuation
A 2000 m deep section of total attenuation and chlorophyll and phycoerythrin fluorescence from 26° to 59°N latitude in the northeast Pacific is discussed in terms of inferred biological processes. Photic zone distributions of these quantities vary from nutrient-limited conditions in the subtropics to light-limited conditions in the subarctic. Phycoerythrin-containing organisms, probably Synechococcus, contribute to a strong, near-surface orange fluorescence signal in the Gulf of Alaska. We now recognize that the fluorescence minimum (about 300 m) between the photic zone and the tertiary fluorescence maximum may be related to secondary producers that "repackage" organic matter produced in the photic zone. The tertiary fluorescence maximum (about 1000 m) is a continuous feature of the oxygen minimum zone in the North Pacific. The presence of phycoerythrin in the tertiary maximum is consistent with heterotrophic cyanobacteria and other unidentified microbial assemblages in the oxygen minimum, though there is no strong biological evidence that this is true. © 1992., Cited By (since 1996):2, Oceanography, Source: Scopus
VERTEX lateral transport: The lateral transport of manganese in the northeast Pacific
VERTEX lateral transport: The lateral transport of manganese in the northeast Pacific
Vertical distributions (0 to 2000 m) of dissolved Mn were measured at 5 stations on a 3200-km east-west (California to Hawaii) transect during the VERTEX (Vertical Transport and Exchange) IV and V cruises. All profiles shared common features: surface maxima, subsurface minima, maxima associated with the oxygen minimum, and relatively low levels at depth. Particulate Mn fluxes, measured at four of the five stations using free-floating particle traps (∼ 100 to 2000 m), indicated that in situ particulate scavenging was not responsible for the formation of the subsurface dissolved Mn minimum nor was in situ particulate Mn regeneration responsible for the dissolved Mn maximum associated with the oxygen minimum. Thus, these dissolved Mn extrema result primarily from lateral advective transport processes. The Mn minimum is associated with the shallow salinity minimum, a water mass that sinks away from the surface in the North Pacific (∼ 47°N), and spreads to the south and east in our study area. Additional evidence of the onshore flow of open-ocean, near-surface water is provided by the high Pb concentrations (∼ 50 pmol kg -1 associated with this feature. Waters in the oxygen minimum/ Mn maximum appear to have northerly and offshore flow in our study area. Box model estimates indicate that offshore lateral advective velocities must approach 0.4 cm s -1 to balance vertical diffusive losses from the oxygen minimum/dissolved Mn maximum. Maintenance of the subsurface Mn minimum requires onshore lateral transport of water with low Mn content at velocities on the order of 0.9 cm s -1 offshore, increasing to 4.4 cm s -1 inshore. These velocities represent maximum estimates since north-south Mn distribution data were not available. © 1985., Cited By (since 1996):23, Oceanography
VERTEX manganese transport with CaCO3
VERTEX manganese transport with CaCO3
Manganese transport was studied off central California in August and September 1981 as part of the VERTEX (Vertica l Transport and Exchange) research program. Refractory, leachable, and dissolved Mn fractions associated with particles caught in traps set at 11 depths (50 to 2000 m) were analyzed. Through intentional and unintentional CaCO3 dissolution 'experiments', it was learned that the weakly leachable Mn was originally in association with the carbonate phase. Adsorption on surfaces rather than absorption in CaCO3 matrices was indicated by the finding that Mn was not released in proportion to the CaCo3 dissolved, instead it appeared to keep readsorbing to the dissolving surface. Ultimately, Mn went into solution when the particulate CaCO3 was essentially depleted, suggesting that sufficient sites for adsorption were no longer available. Manganese fluxes with CaCO3 were low near the surface (0.1 mg cm-2 ky-1), but increased rapidly in the 50 to 200-m depth interval, and then became more or less constant (1.3 mg cm-2 ky-1 for the remainder of the water column (300 to 2000 m). Rate-of-change estimates indicate that Mn is rapidly scavenged in near-surface waters (-130 ng 1-1 y-1) and slowly regenerated at depth (2.7 ng 1-1 y-1) in our near-shore study area. Residence times for dissolved Mn were estimated at 1.2 y for surface waters and 17 y at depth. The implications of Mn transport with CaCO3 in relation to open-ocean sediment excess Mn are discussed. © 1983., Cited By (since 1996):15, Oceanography

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