Temporal and spatial patterns in abundance and diversity of fish assemblages in Elkhorn Slough,California     

Mary M. Yoklavich  Gregor M. Cailliet  James P. Barry  David A. Ambrose  Brooke S. Antrim 《Estuaries and Coasts》1991,14(4):465-480

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, andEmbiotoca 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.  相似文献   

A pleistocene origin for shore platforms along the Northern Illawarra Coast,New South Wales     

B.P. Brooke  R.W. Young  E.A. Bryant  C.V. Murray‐Wallace  D.M. Price 《The Australian geographer》1994,25(2):178-185

This paper examines the composition, structure and age of clastic deposits situated behind shore platforms at Austinmer and Coledale on the northern Illawarra coast, New South Wales. Our results support earlier chronological evidence of a Pleistocene history for shore platforms along the Illawarra coast. The size and fabric of sediments within these deposits indicate rapid, high‐energy deposition of bedrock eroded from platforms adjacent to the deposits. The elevations of the deposits above the modern shoreline suggest higher sea levels or higher wave energy gradients than presently occurs across these platforms. Dating of sediments within these deposits using ¹⁴C, AAR and TL techniques indicates Late Pleistocene and Late Holocene erosion of the shore platforms. Platform development was initiated before the Last Interglacial as correlative sediments lie atop relict platform surfaces landward of the modern platforms.  相似文献   

Reply to the Discussion by John Nott on ‘Coarse‐sand beach ridges at Cowley Beach,north‐eastern Australia: Their formative processes and potential as records of tropical cyclone history’ by Tamura et al. (2018), Sedimentology,65, 721–744     

Toru Tamura  William A. Nicholas  Thomas S. N. Oliver  Brendan P. Brooke 《Sedimentology》2019,66(2):769-773

Tamura et al. (2018) refined our understanding of formative processes that have resulted in a series of coarse‐sand beach ridges at Cowley Beach in north‐eastern Australia. Nott (2018) claimed that there are several shortcomings in the findings Tamura et al. (2018) presented. However, his criticism mostly derived from his misunderstanding of the data and discussion presented in Tamura et al. (2018), which thus should be clarified here. This reply also reiterates how his method for estimating the magnitude of past tropical cyclones from beach ridges is inconsistent with our observations of beach morphology and beach‐ridge formative processes.  相似文献   

Towards a model for the solar dynamo     

David Moss  John Brooke 《Monthly notices of the Royal Astronomical Society》2000,315(3):521-533

We study a mean field model of the solar dynamo, in which the non-linearity is the action of the azimuthal component of the Lorentz force of the dynamo-generated magnetic field on the angular velocity. The underlying zero-order angular velocity is consistent with recent determinations of the solar rotation law, and the form of the alpha effect is chosen so as to give a plausible butterfly diagram. For small Prandtl numbers we find regular, intermittent and apparently chaotic behaviour, depending on the size of the alpha coefficient. For certain parameters, the intermittency displays some of the characteristics believed to be associated with the Maunder minimum. We thus believe that we are capturing some features of the solar dynamo.  相似文献   

Stable isotopes reveal ecological differences amongst now‐extinct proboscideans from the Cincinnati region,USA          下载免费PDF全文

Eric J. Baumann Jr  Brooke E. Crowley 《Boreas: An International Journal of Quaternary Research》2015,44(1):240-254

The mobility and dietary preferences of now‐extinct proboscideans have not been comprehensively examined in the central USA. We used stable carbon (δ¹³C), oxygen (δ¹⁸O) and strontium (⁸⁷Sr/⁸⁶Sr) isotopic signatures in molar enamel to investigate the foraging ecology of four mastodons (Mammut americanum) and eight mammoths (Mammuthus spp.) from southwestern Ohio and northwestern Kentucky. We tested two hypotheses: (i) these individuals were nomadic migrants that were passing through the region when they died; and (ii) mammoths and mastodons foraged in different environments. Unexpectedly, our results suggest that 11 of the 12 sampled individuals were regional residents. With the exception of one mastodon, ⁸⁷Sr/⁸⁶Sr ratios for proboscideans and regional water samples were statistically indistinguishable; slightly lower ratios for waters suggest glacial loess has an impact on modern samples. Amongst the individuals identified as residents, ⁸⁷Sr/⁸⁶Sr ratios indicate that mammoths and mastodons foraged in discrete geographical areas, and δ¹³C values imply dietary differences between the genera, which is consistent with our expectations. Oxygen isotope values may be able to distinguish animals that lived during the Last Glacial Maximum (LGM) from those that lived more recently. Three mammoths and one mastodon yielded δ¹⁸O values that are similar to modern regional precipitation and surface water, but too high for estimated drinking water during the LGM. We propose that these individuals lived during a relatively warm period following the LGM. Compellingly, the mammoth with the highest δ¹⁸O value also has the lowest δ¹³C value, suggesting that this individual was alive after regional vegetation shifted from open parkland to deciduous forest dominated by C₃ species. Our results demonstrate that a wealth of information can be gleaned from fossil museum specimens and lay a foundation for future work on the foraging ecology of proboscideans and other extinct megafauna from the Midwest USA.  相似文献   

Superhumps in the helium dwarf nova KL Draconis     

Matt A. Wood  Matthew J. Casey †  Peter M. Garnavich  Brooke Haag ‡ 《Monthly notices of the Royal Astronomical Society》2002,334(1):87-93

We report on the discovery of a 25.5-min superhump period for the suspected helium dwarf nova system KL Draconis in a high state. The presence of superhumps combined with the previously observed helium spectrum and large-amplitude photometric variations confirm that KL Dra is an AM CVn system similar to CR Bootis, V803 Cen and CP Eridani. We also find a low-state photometric period at 25.0 min that we suggest may be the orbital period. With this assumption, we estimate   q =0.075  ,   M ₁=0.76 M_⊙  and   M ₂=0.057 M_⊙  .  相似文献   

Plankton dynamics due to rainfall,eutrophication, dilution,grazing and assimilation in an urbanized coastal lagoon     

David Rissik  Edward Ho Shon  Brooke Newell  Mark E. Baird  Iain M. Suthers 《Estuarine, Coastal and Shelf Science》2009

After a prolonged summer dry period, the effects of a distinctive and continuing rainfall on the nutrients and plankton of an urban coastal lagoon were investigated over 2 months. The lagoon filled up over 5 weeks from <10% of its maximum volume until it broke open to the sea. Nutrients (ammonia and oxidised nitrogen) significantly increased the day after initial rainfall, before returning to pre-rainfall conditions within 5 days. Phytoplankton biomass grew 10 fold within a week after initial rainfall in the 25–30 °C water and declined to near initial levels 2 weeks later. The assemblage of phytoplankton and zooplankton changed dramatically after 1 day and again by 6 days later, gradually returning to the original community by 2 weeks after the initial rainfall. Zooplankton responded within a day with a two fold increase in the adult stages of the calanoid copepod Oithona sp., followed a week later by nauplii and adult Acartia bispinosa. The influx of adult Oithona indicates resting populations that were previously under sampled by our plankton net. The plankton community returned to the initial state by 2 weeks, to being dominated by a centric diatom and A. bispinosa after 5 weeks. Dilution of the lagoon reached a maximum of 0.25 d⁻¹, while growth rates of the phytoplankton population reached a maximum of 1 d⁻¹, and A. bispinosa nauplii growth of 2.5 d⁻¹. Declines in chlorophyll biomass from the maximum 10 μg l⁻¹, at a rate of approximately 10% d⁻¹ are consistent with the modelled uptake by zooplankton. The nutrients from runoff, growth and the influx of new zooplankton into the water column, resulted in a depleted δ¹³C and δ¹⁵N stable isotope signature of A. bispinosa by 2–4 ppt within 1–2 weeks, consistent with diatom growth and the terrestrial supply of depleted nutrients. δ³⁴S of A. bispinosa was enriched by 2 ppt for 1–2 weeks after rainfall, but unlike C and N, returned to pre-rainfall levels by the end of the study period. We suggest that plankton studies in coastal lakes with variable water levels that are not tidally driven, should account for the influence of changes in water levels to help explain data variability.  相似文献   

Erratum: Towards a model for the solar dynamo     

David Moss  John Brooke 《Monthly notices of the Royal Astronomical Society》2001,322(1):206-206

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Trophic ecology of the dominant fishes in Elkhorn Slough,California, 1974–1980     

James P. Barry  Mary M. Yoklavich  Gregor M. Cailliet  David A. Ambrose  Brooke S. Antrim 《Estuaries and Coasts》1996,19(1):115-138

Food habits of the dominant fishes collected from 1974 to 1980 at eight locations in Elkhorn Slough, California, and the adjacent ocean were investigated. Epifaunal crustacea was the major prey group identified from stomach contents of more than 2,000 fishes, followed by epifaunal and infaunal worms, and molluscs. Overall, 18 fish species consumed 263 different prey taxa, ranging from 10 taxa to 125 taxa per fish species and including 99 crustacean, 56 polychaete, and 39 molluscan taxa. Mean prey richness was greatest at stations near the ocean and lowest at inshore stations. Detailed dietary data for all prey taxa were summarized as trophic spectra for each fish species. Trophic spectra represented functional groups of prey and were used for comparisons of dietary similarity. Cluster analyses, based on trophic spectra, resulted in four feeding guilds of fishes. Of 18 fish species, seven (Amphistichus argenteus, Leptocottus armatus, Embiotoca jacksoni, Clevelandia ios, Gillichthys mirabilis, Cymatogaster aggregata, andCitharichthys stimaeus) fed principally on epifaunal crustacea. Four species (Pleuronectes vetulus, Platichthys stellatus, Phanerodon furcatus, andMyliobatus californica) consumed mostly molluscs and infaunal worms. Two species (Psettichthys melanostictus andTriakis semifasciata) fed on mobile crustacea, and five species (Hyperprosopon anale, Engraulis mordax, Clupea pallasi, Atherinopsis californiensis, andAtherinops affinis) fed largely on zooplankton and plant material. Our results suggest that high food availability enhances the nursery function of imshore habitats, and emphasize the importance of invertebrate prey populations and the indirect linkage of plant production to the ichthyofaunal assemblarly marine immigrant species that are likely ‘estuarine dependent’.  相似文献   

High-precision array element localization for vertical line arraysin the Arctic Ocean     

Dosso  S.E. Brooke  G.H. Kilistoff  S.J. Sotirin  B.J. McDonald  V.K. Fallat  M.R. Collison  N.E. 《Oceanic Engineering, IEEE Journal of》1998,23(4):365-379

Array element localization (AEL) surveys are often required to accurately localize acoustic instruments (transponders or sensors) in the ocean. These are typically based on transmitting or recording acoustic signals from or at a set of well-known positions. A significant limiting factor in many AEL surveys is the uncertainty inherent in these “known” positions. In this paper, an inversion algorithm is developed which properly treats both transponder and sensor positions as unknowns, subject to available a priori information in the form of position estimates and uncertainties. The algorithm essentially consists of an iterative linearized inversion of the raytracing equations employing the method of regularization. The approach is applied to independently localize transponders and vertical line array (VLA) sensors that form part of a three-dimensional sensor array in the Arctic Ocean. Confidence limits estimated via Monte Carlo simulation indicate that transponders and sensors are localized to less than 1 m in three dimensions. The VLA sensor motion, monitored over a seven-week period, appears to be predominately driven by tidal currents and is consistent with historical current measurements for the region  相似文献