Articles

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


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Benthic changes during 10 years of organic enrichment by McMurdo Station, Antarctica
Benthic changes during 10 years of organic enrichment by McMurdo Station, Antarctica
A benthic habitat along the coast of McMurdo Station in the Ross Sea, Antarctica is enriched by sewage from the station and altered by hydrocarbons and heavy metals in an adjacent historic dumpsite. We report on 10 years of change in the benthic communities from 1988 to 1998 and compare enrichment effects at Australia's Casey Station, East Antarctica. Despite being 14 km apart, reference communities upcurrent and downcurrent of McMurdo Station remained closely similar over time, dominated in all years by a tube building polychaete, Spiophanes tcherniae. The community bordering McMurdo Station was generally a third as abundant as communities at the reference sites over the decade of sampling, although diversity was as high or higher, except in the most contaminated areas. In 1992, organic enrichment of the outfall community intensified and within the year, the opportunistic polychaetes Aphelochaeta sp., Ophryotrocha notialis, Capitella perarmata, and Leitoscoloplos kerguelensis became dominant. Since 1996, two of the three enriched communities have increased in resemblance to the reference communities. Given the observed responsiveness of the benthos to the outfall so far, further changes are anticipated within the year following implementation of sewage treatment in 2003. Organic enrichment by McMurdo Station has had a greater impact on benthic community structure than at Australia's Casey Station. © 2004 Elsevier Ltd. All rights reserved., Cited By (since 1996):37, CODEN: MPNBA
Benthic fluxes and pore water studies from sediments of the central equatorial north Pacific
Benthic fluxes and pore water studies from sediments of the central equatorial north Pacific
Benthic exchange rates of radon-222, oxygen, nitrate, ammonia, and silica were determined using an in situ benthic flux chamber and by modeling pore water profiles at three sites in the central equatorial north Pacific. A comparison of these results reveals several artifacts of pore water collection and processing. Whole-core squeezer (WCS) silica profiles are influenced by adsorption during squeezing and yield calculated fluxes that are too large. Pore water ammonia profiles show near-surface maxima that appear to be an artifact of core recovery. Near-surface nitrate measurements may also be suspect due to oxidation of the ammonia released, causing anomalously large nitrate gradients that yield overestimates of benthic exchange rates. Fluxes of radon, oxygen, and nitrate calculated from WCS profiles agree with chamber fluxes to better than 40% at all sites. Fluxes of silica and nitrate calculated from pore water data collected at coarser scales (> 1 cm intervals) agree within 50% with chamber measurements. Previous flux estimates from pore water and solid phase models established at two of these sites using data collected 6 years prior to this work differ from these chamber measurements, in some cases by up to a factor of 5 due to modeling uncertainties and temporal variabilities in the delivery of organic matter to a site. The benthic oxygen consumption rates measured at these sites are similar (they average 0.36 ± 0.03 mmol m-2 day-1) and are consistent with a trend of oxygen uptake vs. water depth previously established by others on a transect through the oligotrophic north Pacific gyre. © 1990., Cited By (since 1996):62, Rocks and Cores
Benthic infaunal distributions in shallow hydrothermal vent sediments
Benthic infaunal distributions in shallow hydrothermal vent sediments
This study examined the macrofaunal communities of two shallow hydrothermal vent areas, in Bahía Concepción (12 m depth), Mexico, and White Point (8 m depth), California. We tested whether the infaunal community compositions in these systems were different from the surrounding communities, and if the observed differences were related to pore-water and other habitat variables. A combination of temperature, hydrogen sulfide, salinity, and pH influenced the species composition within zones of venting. The vent communities, with a few exceptions, were a sub-set of the surrounding community, represented by a limited diversity of outside fauna in lower abundance. Examination of infaunal life-histories revealed that tube-dwelling and mobile species represented a relatively higher proportion of the fauna near vents than away. Tubes were proposed as a beneficial life-history strategy to inhabitants of the high temperatures of Bahía Concepción, but did not predominate in the high sulfide sediments of White Point. Furthermore, there was no evidence for chemosynthetic strategies amongst the shallow vent infauna, unlike fauna at deep-sea hydrothermal vents and cold seeps. © 2008 Elsevier Masson SAS. All rights reserved., Cited By (since 1996):5, Invertebrates, CODEN: ACOEE
Benthic invertebrate communities on three seamounts off southern and central California, USA
Benthic invertebrate communities on three seamounts off southern and central California, USA
Seamounts are unique and biologically productive deep-sea habitats that have often been described as having high levels of endemism, highly productive fisheries, and benthic communities vulnerable to trawl fishing. We describe the abundance and distribution of benthic megafaunal invertebrates found on 3 seamounts off central and southern California. Video observations were taken during 27 dives of a remotely operated vehicle (ROV) and were annotated in detail using the Monterey Bay Aquarium Research Institute's (MBARI) video annotation reference system (VARS, http://vars.sourceforge.net/). Video analysis yielded 134 477 observations of 202 identified invertebrate taxa. Video transects were analyzed to quantify organism density. Thirteen new species were observed and collected. Invertebrate communities at Davidson and Pioneer Seamounts were dominated by passive suspension-feeding cnidarians (mostly corals), but at Rodriguez Seamount, a guyot, the invertebrate community was dominated by holothurian echinoderms. We found no evidence of endemism among the megafauna at these 3 seamounts, which are all in close proximity to each other and the continental margin. © Inter-Research 2009., Cited By (since 1996):19, Invertebrates, CODEN: MESED
Benthic manganese fluxes along the Oregon-California continental shelf and slope
Benthic manganese fluxes along the Oregon-California continental shelf and slope
Here we examine the factors that influence the manganese (Mn) benthic flux from eastern North Pacific marine sediments, with a primary emphasis on continental shelf locations off Oregon and California and studies that involve the use of in situ benthic chambers. Typical shelf-to-shallow margin (<~350m) sites have benthic Mn efflux rates that average ~8±5μmolm-2d-1. In contrast, for the Eel River continental shelf region the benthic Mn efflux can be an order of magnitude higher than other shelf settings with benthic effluxes exceeding ~50μmolm-2d-1. Based on prior work and some new results, continental margin and slope sites (350-~4000m) have benthic Mn efflux rates that average ~1±1μmolm-2d-1. The combination of the benthic flux and Mn solid-phase data, indicate that for the continental shelf off the Umpqua and Eel Rivers, approximately 15±10% of the total Mn that is delivered to the seafloor is remobilized. The compiled data set shows that the benthic Mn efflux co-varies with the organic carbon oxidation rate with a Mn to organic carbon oxidation (Cox) ratio of ~0.8mmol Mn mol-1. Although this ratio can be as high as ~5 for some Eel River sites, the generally close correspondence between Mn and organic carbon implies that the organic carbon oxidation rate exerts some primary control over the rate of the Mn efflux. The amount of organic carbon oxidized by Mn-oxides, however, represents a small fraction (i.e., generally <1%) of the total organic carbon oxidized in these seafloor sediments. © 2012 Elsevier Ltd., Cited By (since 1996):5, Oceanography, CODEN: CSHRD
Benthic processes and overlying fish assemblages drive the composition of benthic detritus on a central Pacific coral reef
Benthic processes and overlying fish assemblages drive the composition of benthic detritus on a central Pacific coral reef
While detrital material is recognized as an important food source on coral reefs, its role in reef food webs remains unclear. We quantified standing stock and input rates to the detrital resource pool in exposed forereef and protected backreef habitats of Palmyra Atoll National Wildlife Refuge and measured the trophic structure of the overlying fish assemblage. While detrital standing stock was 1.6 times higher on the backreef than on the forereef, detrital input rates were 1.7 to 2.9 times higher on the forereef. Planktivores were the most abundant guild in the fore reef habitat, and stable isotope signatures of detritus reflected a greater input from pelagic sources (i.e. depleted in 13C). In contrast, herbivores and detritivores numerically dominated the backreef habitat and detrital stable isotope signatures appeared to be predominately of benthic origin (i.e. enriched in 13C). Through total organic carbon (TOC) and nitrogen analyses we found that benthic detritus may represent a significant nutritional source. Converting total nitrogen into maximum protein estimates, we found high benthic deposition of protein (104 to 124 mg m-2 d-1) and organic carbon (184 to 190 mg m -2 d-1), but very low standing stocks of these materials (protein: 5 to 6 mg m-2, organic carbon: 46 to 63 mg m-2). While high water flow rates may explain low standing stocks of detritus in forereef habitats, the lower flow rates in backreef habitats suggest that removal of this material is via consumption by abundant roving detritivorous fishes. Our results provide support for the hypothesis that reef fish detritivory represents a significant consumer-mediated energy pathway, promoting nutrient recycling by linking many elements of a complex food web. © Inter-Research 2013., Cited By (since 1996):1, Fish and Fisheries, CODEN: MESED
Benthic succession on an artificial reef designed to support a kelp-reef community
Benthic succession on an artificial reef designed to support a kelp-reef community
Pendleton Artificial Reef (PAR) was constructed to determine the potential of artificial reefs to mitigate for possible losses of kelp-reef habitat resulting from operation of coastal power plants. Placed in August 1980, PAR consists of eight boulder modules (some topped with cobble) on a featureless sand bottom at a depth of 13.1 m below MLLW. We studied benthic succession on PAR from September 1981 through August 1983 using a point quadrat sampling technique to describe abundances and vertical distribution of organisms. During this period, small foliose and filamentous algae growing on or over other organisms accounted for 56% of the overstory cover. Cryptoarachnidium (a sediment fixing, encrusting ectoproct) and barnacles accounted for 66% of the understory cover. Cryptoarachnidium was particularly abundant on all modules, while algal turf cover was highest on modules constructed primarily of boulders. On module crests where light and water motion were highest, algal turf was greatest and negatively correlated with erect ectoprocts that were greatest on the slopes of modules. Since erect ectoprocts may inhibit algal colonization and were most abundant on the slopes, we suggest that light, turbidity, and competitive interactions with erect ectoprocts limit the comparatively high cover of algal turf to the module crests. Cover of algal turf was also greatest during periods of clear water in late fall and early winter, while erect ectoproct cover increased during the study period. Cryptoarachnidium cover increased rapidly during the first year after reef placement and stabilized during 1982-1983. Barnacles were the only organisms to show a decline in abundance during the study period. PAR has been in place over 3 years, but relatively to a local natural reef, is still dominated by early successional species. This phenomena appears to result from a number of factors, but especially environmental conditions at the time of reef placement and the isolation of PAR from other shallow reefs in the area.
Beyond Jaws
Beyond Jaws
Southern Africa has one of the richest and most diverse chondrichthyan faunas in the world, comprising all 13 orders, 49 families, 111 genera and approximately 204 species. This represents nearly 20% of all known chondrichthyans, and includes 117 shark, 79 batoid and 8 chimaera species. A greater diversity of chondrichthyan species is seen on the east coast (n = 175) compared to the west coast (n = 96), especially among the families Carcharhinidae and Dasyatidae. The cumulative number of species added to the fauna has increased over the past 112 years from 28 to 204. A golden age of southern African chondrichthyan research occurred between 1967 and 1976 when 46 species were added to the fauna, 16 of which were newly described. A total of 5 families, 23 genera and 130 species have been described from southern Africa. Three families, 17 genera and 75 species are still considered valid. In all, 59 researchers have authored new species descriptions of southern African chondrichthyans, with 95 of 130 species being described by just 14 authors. The most new species described were by JLB Smith with 18, followed by J Müller and FGJ Henle, who collaborated to author 12 new species descriptions. A review of the conservation status of 189 chondrichthyan species indicates that 29% have been assessed as Vulnerable or higher (more threatened), a much higher percentage than the 17.4% of chondrichthyans globally. Of particular concern is that 13% are species endemic to southern Africa. Despite increased chondrichthyan awareness and popularity, most research and conservation efforts centre on a few charismatic species, while the future of little-known species remains ‘lost’ from the public and scientific consciousness. © 2015 NISC (Pty) Ltd., Cited By :4, Export Date: 4 September 2015
Biodiversity and systematics of skates (Chondrichthyes: Rajiformes: Rajoidei)
Biodiversity and systematics of skates (Chondrichthyes: Rajiformes: Rajoidei)
Skates (Rajiformes: Rajoidei) are a highly diverse fish group, comprising more valid species than any other group of cartilaginous fishes. The high degree of endemism exhibited by the skates is somewhat enigmatic given their relatively conserved body morphology and apparent restrictive habitat, e.g. soft bottom substrates. Skates are primarily marine benthic dwellers found from the intertidal down to depths in excess of 3,000 m. They are most diverse at higher latitudes and in deepwater, but are replaced in shallower, warm temperate to tropical waters by stingrays (Myliobatodei). The number of valid skate species has increased exponentially, with more species having been described since 1950 (n = 126) than had been described in the previous 200 years (n = 119). Much of the renaissance in skate systematics has largely been through the efforts of a few individuals who through author-coauthor collaboration have accounted for 78 of the 131 species described since 1948 and for nine of 13 genera named since 1950. Furthermore, detailed regional surveys and accounts of skate biodiversity have also contributed to a better understanding of the diversity of the skates. A checklist of the living valid skate species is presented. © 2007 Springer Science+Business Media, Inc., Cited By (since 1996):31, Fish and Fisheries, CODEN: EBFID
Biodiversity, Life History, and Conservation of Northeastern Pacific Chondrichthyans
Biodiversity, Life History, and Conservation of Northeastern Pacific Chondrichthyans
The sharks, batoids, and chimaeras, collectively the class Chondrichthyes, are one of the most successful groups of fishes, with over 1250 species globally. Recent taxonomic revisions have increased their diversity by about 20% over the past 17 years (2000–2016). The Northeast Pacific Ocean is one of the top 20 most diverse regions/countries on the globe with 77 chondrichthyan species, a number less than a quarter that of the most species-rich area (Australia) but that has increased by 10% since 2000 to include three new species (two skates and a chimaera). In this chapter we discuss the species richness of chondrichthyans occurring in the Northeast Pacific Ocean, characterize their life histories, briefly review several fisheries, and summarize the conservation status of those chondrichthyans occurring in the region. Detailed descriptions and evaluations of fisheries can be found in Chapter 7 of AMB Volume 78.
Biogenic matter diagenesis on the sea floor
Biogenic matter diagenesis on the sea floor
Benthic chamber measurements of the reactants and products involved with biogenic matter diagenesis (oxygen, ammonium, nitrate, silicate, phosphate, TCO2, alkalinity) were used to define fluxes of these solutes into and out of the sediments off southern and central California. Onshore to offshore transects indicate many similarities in benthic fluxes between these regions. The pattern of benthic organic carbon oxidation as a function of water depth, combined with published sediment trap records, suggest that the supply of organic carbon from vertical rain can just meet the sedimentary carbon oxidation + burial demand for the central California region between the depths 100-3500 m. However, there is not enough organic carbon raining through the upper water column to support its oxidation and burial in the basins off southern California. Lateral transport and focusing of refractory carbon within these basins is proposed to account for the carbon buried. The organic carbon burial efficiency is greater off southern California (40-60%) compared to central California (2-20%), even though carbon rain rates are comparable. Oxygen uptake rates are not sensitive to bottom water oxygen concentrations nor to the bulk wt. % organic carbon in surficial sediments. Nitrate uptake rates are well defined by the depth of oxygen penetration into the sediments and the overlying water column nitrate concentration. Nitrate uptake accounts for about 50% of the total denitrification taking place in shelf sediments and denitrification (0.1-1.0 mmolN/m2d) occurs throughout the entire study region. The ratio of carbon oxidized to opal dissolved on the sea floor is constant (0.8 ± 0.2) through a wide range of depths, supporting the hypothesis that opal dissolution kinetics may be dominated by a highly reactive phase. Sea floor carbonate dissolution is negligible within the oxygen minimum zone and reaches maximal rates just above and below this zone (0.2-2.0 mmol/m2d)., Cited By (since 1996):72, Oceanography
Biogeochemistry of hydrothermal vent mussel communities
Biogeochemistry of hydrothermal vent mussel communities
Cited By (since 1996):64, Invertebrates, CODEN: DRORE, Continuous measurements of sulfide, silicate and temperature were made in situ from the submersible Alvin in the Rose Garden and New Vent hydrothermal fields of the Galapagos Spreading Center. Continuous measurements of temperature also were made for an 18 day period in the Rose Garden field. The results demonstrate several adaptations that appear to have contributed to the success of the vent mussel Bathymodiolus thermophilus in the Rose Garden. Dense clusters of B. thermophilus can disperse the hydrothermal fluids laterally for distances of several meters. This results in a large increase in the area of the redox transition zone, where both dissolved oxygen and hydrogen sulfide are available. As a result, the animal communities can grow to occupy areas that would not otherwise provide adequate reduced substrates. Measurements of the temperature demonstrate a distinct tidal periodicity. This periodicity will result in a large range of environmental conditions within the vent community. The mussel can tolerate these wide ranges in condition because of its ability to accept long periods of anoxia and to filter feed.
Biologic and geologic characteristics of cold seeps in Monterey Bay, California
Biologic and geologic characteristics of cold seeps in Monterey Bay, California
Cold seep communities discovered at three previously unknown sites between 600 and 1000 m in Monterey Bay, California, are dominated by chemoautotrophic bacteria (Beggiatoa sp.) and vesicomyid clams (5 sp.). Other seep-associated fauna included galatheid crabs (Munidopsis sp.), vestimentiferan worms (Lamellibrachia barhami?), solemyid clams (Solemya sp.), columbellid snails (Mitrella permodesta, Amphissa sp.), and pyropeltid limpets (Pyropelta sp.). More than 50 species of regional (i.e. non-seep) benthic fauna were also observed at seeps. Ratios of stable carbon isotopes (δ13C) in clam tissues near -36‰ indicate sulfur-oxidizing chemosynthetic production, rather than non-seep food sources, as their principal trophic pathway. The 'Mt Crushmore' cold seep site is located in a vertically faulted and fractured region of the Pliocene Purisima Formation along the walls of Monterey Canyon (~635 m), where seepage appears to derive from sulfide-rich fluids within the Purisima Formation. The 'Clam Field' cold seep site, also in Monterey Canyon (~900 m) is located near outcrops in the hydrocarbon-bearing Monterey Formation. Chemosynthetic communities were also found at an accretionary-like prism on the continental slope near 1000 m depth (Clam Flat site). Fluid flow at the 'Clam Flat' site is thought to represent dewatering of accretionary sediments by tectonic compression, or hydrocarbon formation at depth, or both. Sulfide levels in pore waters were low at Mt Crushmore (ca 0.2 mM), and high at the two deeper sites (ca 7.011.0 mM). Methane was not detected at the Mt Crushmore site, but ranged from 0.06 to 2.0 mM at the other sites., Cited By (since 1996):108, Invertebrates, CODEN: DRORE
Biological aspects of the sixgill shark, Hexanchus griseus.
Biological aspects of the sixgill shark, Hexanchus griseus.
Life history information on 28 sixgill sharks, collected off California, was obtained from May 1982 through Sept. 1984. Only one mature sixgill shark, a 421 cm TL female with term embryos, was examined. Size at maturity was estimated for females by comparing gonad development with length-weight measurements. Gut analysis revealed that the sixgill shark's diet consists mainly of bony and cartilaginous fishes. Since sixgill sharks do not appear to be abundant anywhere, their distribution and movement patterns along the deep coastal waters off California are, for the most part, unknown., Cited By (since 1996):19, Fish and Fisheries
Biological notes on the Pacific sleeper shark, Somniosus Pacificus (Chondrichthyes soualidae)
Biological notes on the Pacific sleeper shark, Somniosus Pacificus (Chondrichthyes soualidae)
Information was obtained on the Pacific sleeper shark, Somniosus pacificus Bigelow and Schroeder, 1944, along the California coast from fishermen who caught specimens incidentally in sablefish traps and trawls. Morphometric and tooth-count data were taken from several specimens. An estimate of fecundity was based on one specimen with 372 yellow, vascularized, ovarian eggs. The approximate size at marurity was determined using gonadal development and a length-weight curve. Pacific sleeper sharks are considered sluggish, bottom-dwelling, cephalopod and fish feeders, yet they may occasionally consume fast swimming epipelagic fish.
Biological response to iron fertilization in the eastern equatorial Pacific (IronEx II). I. Microplankton community abundances and biomass
Biological response to iron fertilization in the eastern equatorial Pacific (IronEx II). I. Microplankton community abundances and biomass
During the IronEx II experiment in the eastern equatorial Pacific (May to June 1995), the response of the microplankton community to mesoscale iron fertilization was followed using a combination of marker-pigment, microscopical and flow cytometric techniques. Phytoplankton standing stock bloomed dramatically over a period of 6 d following 3 iron additions of 2 and 1 nM, respectively. Carbon biomass in the patch increased by a factor of 4, chlorophyll a by about a factor of 16 and diatoms by > 70-fold relative to contemporaneous levels in the ambient community. The bloom then plateaued sharply and remained at a more or less constant level for 4 d, despite the addition of more iron (1 nM) and physiological indices (low C:chl a ratio and elevated photochemical quantum efficiency) suggesting that the cells were healthy and growing rapidly. Relatively large pennate diatoms (Nitzschia spp., median length 20 to 24 μm) dominated the patch bloom, with smaller pennate species and centric diatoms declining in relative importance. Heterotrophic bacteria increased at a slow rate (0.08 d -1) for > 10 d during the experiment, as did heterotrophic nanoflagellates. There were also indications of enhanced cell size, cellular pigment content and possibly growth rates of small phytoplankton. Nonetheless, little difference was observed between the ambient community and the peak patch bloom with respect to the size composition of auto- and heterotrophic populations < 10 μm in cell size. The relative constancy of the smaller size fractions, the sharp curtailment of net growth of the bloom after 6 d, and > 3-fold increase in large heterotrophic dinoflagellates and ciliates suggest that protistan grazers may have played an active role in controlling the phytoplankton response to increased iron availability.
Biology of the White Shark (Carcharodon carcharias) in Aquaria
Biology of the White Shark (Carcharodon carcharias) in Aquaria
Since 2004, the Monterey Bay Aquarium, California, has displayed six juvenile white sharks, Carcharodon carcharias (Linnaeus, 1758), in the 3,800 m3 Outer Bay exhibit. Upon capture, the sharks (132 - 164 cm total length (TL) and 19.6 - 47.0 kg body mass (BM)) were held in a 13,800 m3 ocean pen to initiate feeding prior to transport. Oxygen consumption rates of free-swimming C. carcharias during transports were analyzed, yielding one of the highest reported mass-specific muscle oxygen consumptions (MO2) for any shark species (246 ± 13 mg O2/kg/h). While on display (70 - 198 days), four of the C. carcharias fed consistently at a daily ration of 747 ± 46 g, or 1.62 ± 0.15% BM/day. One shark did not feed and was released after 11 days; another shark fed intermittently and was released after 55 days, but died immediately post-release. Mean mass growth rate for C. carcharias at the Monterey Bay Aquarium was 71.6 ± 8.2 kg/yr, with a corresponding mean dietary gross conversion efficiency of 27.1 ± 3.8%. The mean length growth rate (64.9 ± 8.5 cm/yr), was approximately twice the rate estimated from a published von Bertalanffy growth function. All C. carcharias were fitted with pop-up archival satellite tags upon release, which provided evidence of post-release survivorship.
Bioluminescence profile in the deep Pacific Ocean
Bioluminescence profile in the deep Pacific Ocean
The vertical profile of bioluminescence at a station hear Hawaii has been measured to a depth of 4300 m using a calibrated instrument with a threshold sensitivity of 400 photons cm-2 s-1. The measured light is dominated by flashes over a very faint ambient background. The median light levels follow an exponential scaling law below 2000 m and decrease at the rate of 1/e per kilometer. Stimulated bioluminescence is observed in the wake of the instrument, even at depth. © 1987., Cited By (since 1996):14, Oceanography
Biomass and production of heterotrophic bacterioplankton in the oceanic subarctic Pacific
Biomass and production of heterotrophic bacterioplankton in the oceanic subarctic Pacific
As part of the Subarctic Pacific Ecosystem Research (SUPER) program, we measured the abundance and biomass production of heterotrophic bacterioplankton in the subarctic Pacific and compared these parameters with those of phytoplankton during four cruises in 1987 and 1988. Bacterial biomass was about equal to phytoplankton biomass during all cruises. Based on rates of bacterial biomass production and assuming a growth efficiency of 50%, we estimate that heterotrophic bacteria consumed 10% (June 1987) to 24% (August 1988) of primary production in the euphotic zone. These percentages are low compared with other aquatic ecosystems, apparently due to low bacterial growth rates (<0.1 day-1) iin the subarctic Pacific. In contrast, phytoplankton growth rates were much higher (0.1-8.8 day-1). Bacterial growth rates were limited by the supply of dissolved organic matter and temperature. Even with these low growth rates, however, bacterial biomass and rates of biomass production increased by 2-5-fold in May and August 1988, changes that were not obviously related to corresponding changes in phytoplankton biomass nor primary production. Heterotrophic bacterioplankton constitutes a large reservoir of carbon and nitrogen that needs to be considered in modelling ecosystem dynamics of the subarctic Pacific. © 1993., Cited By (since 1996):101, Oceanography, CODEN: DRORE
Biomass loss reduces growth and resource translocation in giant kelp Macrocystis pyrifera
Biomass loss reduces growth and resource translocation in giant kelp Macrocystis pyrifera
The biomass dynamics of primary producers have important implications for the structure and function of ecosystems. Along the wave-swept coastline of central California, USA, biomass removal by wave action is a key driver in the primary productivity of giant kelp forests, yet the mechanisms of regrowth within giant kelp Macrocystis pyrifera are not well understood. To examine the physiological consequences of biomass loss on Macrocystis, a manipulative experiment was used to simulate biomass removal by wave action. Growth rates were measured as the number of new fronds produced through time, and the δ13C and δ15N values of juvenile fronds were used as a proxy for carbon and nitrogen translocation in support of growth. The experimental removal of biomass significantly constrained the growth of new fronds and, under extreme levels, led to mortality. The growth rate and isotopic composition of juvenile fronds on sporophytes with a portion of canopy biomass intact recovered to pre-disturbance values within 4 mo. In contrast, a reduction in growth rates as well as a permanent depletion in δ13C and δ15N values was observed when the canopy was completely removed and the magnitude scaled with biomass loss. These results suggest that the translocation of carbon and nitrogen to juvenile fronds from near-surface biomass is a critical process affecting growth in giant kelp. The spatial variability and physiological consequences of biomass loss among individuals may therefore play an important role in the biomass dynamics of giant kelp forests across multiple temporal and spatial scales.
Black pools of death: Hypoxic, brine-filled ice gouge depressions become lethal traps for benthic organisms in a shallow Arctic embayment
Black pools of death: Hypoxic, brine-filled ice gouge depressions become lethal traps for benthic organisms in a shallow Arctic embayment
Numerous small (9 ± 7 m2, mean ± SD) depressions filled with dark water were found covering 14% of the shallows (<10 m) sea floor of Resolute Bay, NWT, Canada, on July 28, 1995. The water in these black pools was hypoxic, warmer, and more saline and sulfide rich than surrounding bottom water. These pools also contained high numbers of dead epibenthic species, including: shrimps, amphipods, mysids, bivalves, gastropods, sea cucumbers, and fishes. Infaunal abundance and biomass, as well as benthic chlorophyll concentrations, were significantly lower inside the black pools than in the surrounding sediments. The pools persisted until the first strong wind to occur after annual sea-ice break-up. A year (July 1996), sulfide-rich black saline pools were again found in the same depressions as well as in new depressions formed by grounding ice during the previous summer. We hypothesize that the pools form annually, as the sea ice expels dense brine, which sinks and collects in previously formed ice gouge depressions on the shallow of Resolute Bay. Benthic respiration would be sufficient to drive the stratified water in the pools to anoxia in the absence of currents and turnover, resulting in microbial production of highly toxic sulfides. Once established, the pools persist as lethal traps for benthic and demersal organisms until dispersed by wind or waves after breakup of the annual ice cover., Cited By (since 1996):27, Invertebrates, CODEN: MESED
Bomb radiocarbon and lead-radium disequilibria in otoliths of bocaccio rockfish (Sebastes paucispinis)
Bomb radiocarbon and lead-radium disequilibria in otoliths of bocaccio rockfish (Sebastes paucispinis)
Longevity estimates for the bocaccio rockfish (Sebastes paucispinis) using traditional techniques range from less than 20 years to approximately 50 years. Otoliths of bocaccio are difficult to age, and previous attempts to validate ages have been unsuccessful. Because otolith age suggests the bocaccio are reasonably long-lived, lead-radium dating was used in an attempt to independently age bocaccio otoliths. The measured 210Pb and 226Ra activities were among the lowest reported and resulted in poor radiometric age resolution; however, the break-and-burn technique clearly underestimated age in some cases with the longevity of the bocaccio being at least 31 years. To provide better age resolution, the bomb radiocarbon approach was applied to individual otoliths. Based on measured radiocarbon levels relative to a reference time-series, several specimens were aged at approximately 30-40 years. To evaluate these determinations, the remaining otolith of the pair was sectioned and aged blind. The result was an excellent fit to the reference time-series and a validation of the age estimates. The maximum age from growth zone counts was 37 ± 2 years, which is consistent with a reported maximum age of approximately 50 years. © CSIRO 2005., Cited By (since 1996):18, Fish and Fisheries, CODEN: AJMFA

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