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An in situ study of recruitment, growth and survival of subtidal marine algae,
Neushul, Foster, Coon, Woessner, Harger
Statistical significance of sediment toxicity test results: Threshold values derived by the detectable significance approach
A number of methods have been employed to determine the statistical significance of sediment toxicity test results. To allow consistency among comparisons, regardless of among-replicate variability, a protocol-specific approach has been used that considers protocol performance over a large number of comparisons. Ninetieth-percentile minimum significant difference (MSD) values were calculated to determine a critical threshold for statistically significant sample toxicity. Significant toxicity threshold values (as a percentage of laboratory control values) are presented for six species and nine endpoints based on data from as many as 720 stations. These threshold values are useful for interpreting sediment toxicity data from large studies and in eliminating cases where statistical significance is assigned in individual cases because among-replicate variability is small.
Phillips, Hunt, Anderson, Puckett, Fairey, Wilson, Tjeerdema
Acoustic monitoring of Atlantic cod (Gadus morhua) in Massachusetts Bay,
Atlantic cod (Gadus morhua) stocks in northeastern US waters are depleted and stock recovery has been slow; research into the spawning behaviour of this species can help inform conservation and management measures. Male cod produce low-frequency grunts during courtship and spawning. Passive acoustic monitoring (PAM) offers a different perspective from which to investigate the occurrence, spatial extent and duration of spawning cod aggregations. A marine autonomous recording unit was deployed in the "Spring Cod Conservation Zone" (SCCZ) located in Massachusetts Bay, western Atlantic, to record cod grunts from April-June 2011. Cod grunts were present on 98.67% of the recording days (n = 75 days). They occurred across all 24 h, although significantly more grunts were found during the day than night-time (p = 0.0065). Grunt durations ranged from 57-360 ms, and the fundamental frequency and second harmonic had mean peak frequencies of 49.7 ± 5.6 and 102.9 Hz ± 10.9 sd, respectively. Cod grunt rates were low compared with those reported for other spawning fish, and may be indicative of diel movement patterns. Next steps will focus on expanding PAM coverage within the SCCZ, alongside prospecting for unknown spawning grounds within existing archival data. © 2013 © United States Government [NOAA] 2013. Published by Oxford University Press., Fish and Fisheries, CODEN: ICESE, ,
Hernandez, Risch, Cholewiak, Dean, Hatch, Hoffman, Rice, Zemeckis, Van Parijs
Vertex: Phytoplankton/iron studies in the Gulf of Alaska,
VERTEX studies were performed in the Gulf of Alaska in order to test the hypothesis that iron deficiency was responsible for the phytoplankton's failure to remove major plant nutrients from these waters. In view of the observed Fe distributions and the results of phytoplankton Fe enrichment experiments, it was concluded that Gulf of Alaska atmospheric Fe input rates are sufficient to support moderately high rates of primary productivity; however, not enough Fe is available to support the high growth rates that would lead to normal major nutrient depletion. Enhanced Fe input does occur along the Alaska continental margin, where normal NO 3 surface depletion is observed. Coccolithophorids appear to be best able to cope with low Fe conditions; however, they cannot compete with diatoms when Fe is readily available. Iron may be more important than available N in determining global rates of phytoplankton new production. Offshore Pacific Ocean water, replete with major nutrients, appears to be infertile without supplemental iron from the atmosphere or continental margin. © 1989., Cited By (since 1996):399, ,
Martin, Gordon, Fitzwater, Broenkow
Ozone depletion: Ultraviolet radiation and phytoplankton biology in Antarctic waters,
The springtime stratospheric ozone (O 3) layer over the Antarctic is thinning by as much as 50 percent, resulting in increased midultraviolet (UVB) radiation reaching the surface of the Southern Ocean. There is concern that phytoplankton communities confined to near-surface waters of the marginal ice zone will be harmed by increased UVB irradiance penetrating the ocean surface, thereby altering the dynamics of Antarctic marine ecosystems. Results from a 6-week cruise (Icecolors) in the marginal ice zone of the Bellingshausen Sea in austral spring of 1990 indicated that as the O 3 layer thinned: (i) sea surface- and depth-dependent ratios of UVB irradiance (280 to 320 nanometers) to total irradiance (280 to 700 nanometers) increased and (ii) UVB inhibition of photosynthesis increased. These and other Icecolors findings suggest that O 3-dependent shifts of in-water spectral irradiances alter the balance of spectrally dependent phytoplankton processes, including photoinhibition, photoreactivation, photoprotection, and photosynthesis. A minimum 6 to 12 percent reduction in primary production associated with O 3 depletion was estimated for the duration of the cruise., Cited By (since 1996):544, CODEN: SCIEA, ,
Smith, Prézelin, Baker, Bidigare, Boucher, Coley, Karentz, Macintyre, Matlick, Menzies, Ondrusek, Wan, Waters
Growth rates, grazing, sinking, and iron limitation of equatorial Pacific phytoplankton,
, , , Concentrations of phytoplankton and NO, are consistently low (0.2-0.4 μg Chl a liter-1) and high (4-12 μM) in surface waters of the oceanic eastern and central equatorial Pacific, and phytoplankton populations are dominated by small solitary phytoplankton (< 10 μm). Growth rates of natural phytoplankton populations, needed to assess the relative importance of many of the processes considered important in maintaining the high-nutrient, low-phytoplankton biomass condition observed in the equatorial Pacific, were estimated by several methods. The growth rates of natural phytoplankton populations were found to be -0.7 d-1 or biomass doubling d-1 and were similar for all methods. To keep this system in its observed balance requires that loss rates approximate observed growth rates. Grazing rates, measured with a dilution grazing experiment, were high (-0.5 d-1), accounting for a large fraction of the daily production. Additions of various forms of Fe to 5-7-d incubations utilizing ultraclean techniques resulted in significant shifts in autotrophic (from picoplankton to diatom dominated) and heterotrophic assemblages between initial samples, controls, and Fe enrichments, which were presumably due to Fe, grazing by both protistan and metazoan components, and incubation artifacts. Estimated growth rates of small pennate diatoms (2 x 10 μm) showed increases in Fe enrichments (mean ± SD = 1.60 ± 0.04 d-1) with respect to controls (mean ± SD = 1.21 ± 0.33 d-1). The growth rates of the pennate diatoms were similar to those estimated for the larger (~5 μm) size fraction of the natural populations (mean = 1.42 d-1). We hypothesize that biomass regulation of the larger size fraction of phytoplankton is by a combination of grazing, Fe limitation, and sinking and that understanding the controls over the larger phytoplankton is fundamental to unraveling the high-nutrient, low-biomass paradigm., ,
The behaviour of iron and other trace elements during the IronEx-I and PlumEx experiments in the Equatorial Pacific,
Dissolved (< 0.4 μm) and particulate (0.4-5 μm and > 5 μm, leachable and refractory) trace elements were measured during the IronEx I and PlumEx experiments in October and November 1993 near the Galapagos Islands. Iron was measured in the enriched patch and at control stations over a 9 day period following fertilization. The dissolved iron was initially depleted at a rate that gave an iron half-life of 28-40 h. The loss rate gradually decreased, and dissolved iron concentrations did not decrease below about 0.25 nmol kg-1 throughout the experiment. These results were most consistent with a kinetic model that was second order in iron concentration for the scavenging removal of each iron fraction. Other trace elements measured did not change significantly either in concentration or partitioning during the IronEx I experiment. Biological production tracked iron concentrations over time, which suggests that productivity within the fertilized patch was regulated by the availability of iron. The PlumEx study consisted primarily of two transects, a meridional course to the east of the Galapagos Islands and a zonal section to the west. Surface dissolved iron was very low at all stations except those near the Galapagos Islands. Sections of trace metal and other properties distinctly confirm the upwelling of the Equatorial Undercurrent as it intersects the islands. This upwelling has a great effect on the surface distributions of the trace metals on the west side of the islands. Productivity within the mixed layer of this region is highly correlated with iron and nitrate. West of the islands highest productivity is found at stations with the highest iron. North of the Equatorial front, in nitrate-depleted waters, elevated iron concentrations do not enhance productivity., Cited By (since 1996):58, Oceanography, CODEN: DSROE, ,
Gordon, Johnson, Coale
Dr. Michael Neushul,
Reed, Norris, Foster
What sharks can tell us about the evolution of MHC genes,
Similarity in structural features would argue that sharks possess class I, class IIA and class IIB genes, coding for classical peptide-presenting molecules, as well as non-classical class I genes. Some aspects of shark major histocompatibility complex genes are similar to teleost genes and others are similar to tetrapod genes. Shark class I genes form a monophyletic group, as also seen for tetrapods, but the classical and nonclassical genes form two orthologous clades, as seen for teleosts. Teleost class I genes arose independently at least four different times with the nonclassical genes of ray-finned fishes and all the shark and lobe-finned fish class I genes forming 1 clade. The ray-finned fish classical class I genes arose separately. In phylogenetic trees of class II α2 and β2 domains, the shark and tetrapod genes cluster more closely than the teleost genes and, unlike the teleost sequences, the class II α1 domains of sharks and tetrapods lack cysteines. On the other hand, both shark and teleost genes display sequence motifs in the antigen-binding cleft that have persisted over very long time periods. The similarities may reflect common selective pressures on species in aqueous environments while differences may be due to different evolutionary rates., Cited By (since 1996):19, CODEN: IMRED, ,
The flux of iron from continental shelf sediments,
The flux of dissolved iron from sediments to the water column was measured with flux chambers along the California coast over a five-year period. High fluxes were observed from sediments on the continental shelf. The measured fluxes were an average of 75 times larger than flux values derived from pore-water iron gradients. The iron flux was significantly correlated with the oxidation of organic matter, which allows an extrapolation to the global shelf. The input from shelf sediments is at least as significant as the global input of dissolved iron from aerosols, which has been presumed to be the dominant external iron source. Evidence of this input is seen 100's of kilometers offshore where it can enable the high productivity of broad coastal regions seen in satellite images. Copyright 2004 by the American Geophysical Union., Cited By (since 1996):125, Oceanography, CODEN: GPRLA, ,
Elrod, Berelson, Coale, Johnson
Settlement, growth and reproduction of benthic algae within Macrocystis forests in California,
Harger, Coon, Foster, Neushul, Woessner
Erratum to Functional significance of intramandibular bending in Poeciliid fishes,
Fish and Fisheries, CODEN: EBFID, , ,
Gibb, Ferry-Graham, Hernandez, Romasco, Blanton
The validity of using morphological characteristics as predictors of age in the kelp, Pterygophora californica (Laminariales, Phaeophyta),
Previous studies have used stipe ring counts to estimate the age of several species in the Laminariales. Although this method is widely accepted, it has rarely been validated. To test the validity of aging Pterygophora californica by counting rings formed in the stipe, we sampled plants of known age between 1.0 and 4.4 yr old and plants with a calculated age of 12 yr. For a given cohort, the number of complete rings closely approximated the known age in years. indicating ring counts are a reliable method for estimating the age structure of P califomica populations. However, ring counts from individual plants of known age can vary by ± 2 yr (95 % CI), and among readers counting the same plants by ± 1 yr (95 % CI). Single plants, there fore, could not be reliably aged by ring counts Linear relationships between 2 morphometric measures (stipe length and stipe diameter) and number of rings varied both within and between stands and sites, suggesting these measures are not reliable for estimating the age of this alga in the areas sampled. Stand density may be an important factor contributing to the variation in these morphome tric measures. Short-term (22 wk) field manipulations of stand density showed that plants at high density (30 plants m^-2) grew faster in stipe length and slower in stipe diameter than those at medium (6 plants m^-2) and low (2 plants m^-2) densities. Plants collected in a multi-site survey, however, showed no relationship between stand density and stipe morphology, indicating factors other than density also influence stipe growth Short-term (22 wk) field manipulations, which reduced ambient light levels by up to 58 %. had no significant effects on stipe morphology., , ,
Hymanson, Reed, Foster, Carter
Brittle star distribution patterns and population densities on the continental slope off central California (Echinodermata: Ophiuroidea),
The ophiuroid communities on the continental slope off central California were examined using box cores and trawls. Box cores were taken between 550 and 3085 m at sites southwest of the Farallon Islands, and otter and beam trawls were used below 2300 m at three sites between the Farallon Islands and Point Sur. Eighteen ophiuroid species from six families were identified. Eighty percent of the individuals collected with box cores belonged to two species, Ophiura leptoctenia and Ophiacantha normani, which were dominant between 1000 and 2000 m. The largest ophiuroid faunal break occurred at around 2000 m and was associated with elevated dissolved oxygen levels, decreasing sediment grain size, and increasing sediment organic content. A comparison of box-core and trawl data from below 2300 m showed that box cores undersampled the ophiuroid community on the continental slope, missing almost 50% of the species collected by trawls within the same area, whereas trawls underestimated ophiuroid densities, reporting on average 243 times fewer ophiuroids per m2 than did box cores. There was a change in species relative abundance patterns between sampling locations. Ophiuroids exhibited patchy spatial distribution patterns on both a small scale of around 0.1 m2 and a large scale on the order of 100-1000 s of square meters. (C) 2000 Elsevier Science Ltd., Cited By (since 1996):14, Invertebrates, CODEN: DSROE, ,
Summers, Nybakken
Variations in the biomass of Antarctic krill (Euphausia superba) around the South Shetland Islands, 1996-2006,
The time-series of acoustically surveyed Antarctic krill (Euphausia superba) biomass near the South Shetland Islands (SSI) between 1996 and 2006 is re-estimated using a validated physics-based model of target strength (TS), and a species-discrimination algorithm based on the length-range of krill in plankton samples to identify krill acoustically, derived from TS-model predictions. The SSI area is surveyed each austral summer by the US Antarctic Marine Living Resources Program, and the acoustic data are used to examine trends in krill biomass and to assess the potential impact of fishing to the reproductive success of land-based predators (seals and penguins). The time-series of recomputed biomass densities varies greatly from that computed using an empirical log-linear TS-model and fixed-ranges of differences in volume-backscattering strengths (ΔS v), conventionally used to identify krill acoustically. The new acoustic estimates of biomass are significantly correlated with both proportional recruitment and krill abundance estimated from zooplankton samples. Two distinct peaks in biomass (1996 and 2003) are in accord with recruitment events shown by net-based krill time-series. The foundation for the new TS-model and the associated krill-discrimination algorithm, coupled with the agreement between acoustic- and net-survey results, provides strong support for the use of the new analytical technique. Variable biases in the re-estimated krill biomass have been greatly reduced. However, survey variability increased as a result of the increased rejection of acoustic backscatter previously attributed to krill. Management of Southern Ocean krill stocks based on a precautionary approach may therefore result in decreased allocations of krill, given its dependence on the variability of survey estimates. © 2008 US Government and the Department of Commerce/National Oceanic and Atmospheric Administration/National Marine Fisheries Service/Southwest Fisheries Science Center., Cited By (since 1996):41, CODEN: ICESE, Antartica, ,
Reiss, Cossio, Loeb, Demer
Geographic variation in density, demography, and life history traits of a harvested temperate sex-changing reef fish
Geographic variation in ecological and environmental factors may lead to intraspecific differences among populations. For the California sheephead (Semicossyphus pulcher), an important predator in kelp forests and a target of commercial and recreational fisheries, we evaluated the degree to which different populations exhibited variation in density, demography, and life history traits. We assessed biogeographic patterns of abundance through underwater visual census at 39 sites spanning a major portion of the species range (southern California, USA, to Baja California, Mexico) and made collections from seven focal sites to investigate geographic differences in demography and life histories. California sheephead densities were significantly greater in the southern part of their range and at offshore islands than along the mainland coast. At the focal sites, we found significant spatial variation in density, fecundity, size structure, growth rates, annual survivorship, and the timing of maturation and sex change. Density- and temperature-dependent effects helped to explain the intraspecific differences in these parameters. Studies such as this one will allow for demographic plasticity to be incorporated into future stock assessments. Management of temperate reef fishes may best be achieved on smaller spatial scales as we increase our understanding of geographic variation among populations.
Caselle, Hamilton, Schroeder, Love, Standish, Rosales-Casián, Sosa-Nishizaki