Late Quaternary chironomid community structure shaped by rate and magnitude of climate change     

Roseanna J. Mayfield  Peter G. Langdon  C. Patrick Doncaster  John A. Dearing  Rong Wang  Gaute Velle  Kimberley L. Davies  Stephen J. Brooks 《第四纪科学杂志》2021,36(3):360-376

Much is known about how climate change impacts ecosystem richness and turnover, but we have less understanding of its influence on ecosystem structures. Here, we use ecological metrics (beta diversity, compositional disorder and network skewness) to quantify the community structural responses of temperature-sensitive chironomids (Diptera: Chironomidae) during the Late Glacial (14 700–11 700 cal a bp ) and Holocene (11 700 cal a bp to present). Analyses demonstrate high turnover (beta diversity) of chironomid composition across both epochs; however, structural metrics stayed relatively intact. Compositional disorder and skewness show greatest structural change in the Younger Dryas, following the rapid, high-magnitude climate change at the Bølling–Allerød to Younger Dryas transition. There were fewer climate-related structural changes across the early to mid–late Holocene, where climate change was more gradual and lower in magnitude. The reduced impact on structural metrics could be due to greater functional resilience provided by the wider chironomid community, or to the replacement of same functional-type taxa in the network structure. These results provide insight into how future rapid climate change may alter chironomid communities and could suggest that while turnover may remain high under a rapidly warming climate, community structural dynamics retain some resilience.  相似文献   

Archaeological and paleoenvironmental investigations in the dutchess quarry caves,orange county,new york,R. E. Funk and D. W. Steadman, 1994, Persimmon Press Monographs in Archaeology, 125 pp., $16.95 (paperbound)     

Patrick J. Julig 《Geoarchaeology》1995,10(5):413-416

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Revision of the Carboniferous cystoporate bryozoan Fistulipora incrustans (Phillips, 1836), with remarks on the type species of Fistulipora M'Coy, 1849     

Adrian J. Bancroft  Patrick N. Wyse Jackson 《Geological Journal》1995,30(2):129-143

The type species of the Palaeozoic cystoporate bryozoan genus Fistulipora M'Coy, 1849 is redescribed. Fistulipora minor M'Coy, 1849 is the type species, and was the first species described under the genus Fistulipora. Quantitative assessment of type and figured specimens of Calamopora incrustans Phillips, 1836 and F. minor has shown them to fall within the range of morphological variation exhibited by abundant comparative material collected at several horizons and they are referable to one morphologically variable taxon. F. minor is the junior subjective synonym of C. incrustans and the form can be quoted as F. minor M'Coy, 1849 = C. incrustans Phillips, 1836 with a valid name of F. incrustans (Phillips, 1836). However, this does not alter the name of the type species, which is F. minor M'Coy, 1849. The type specimen of Berenicea megastoma M'Coy, 1844 has also been examined, and this form is also conspecific with F. minor M'Coy, 1849 = C. incrustans Phillips, 1836. Examination of the type specimen of F. major M'Coy (1849) has shown it to be referable to the tabulate coral genus Chaetetes. A lectotype and paralectotypes are designated for F. minor and the status of the type specimens of F. incrustans is clarified.  相似文献   

Late Pleistocene to Holocene sedimentation and hydrocarbon seeps on the continental shelf of a steep,tectonically active margin,southern California,USA   总被引：1，自引：0，他引：1  

Amy E. Draut  Patrick E. Hart  Thomas D. Lorenson  Holly F. Ryan  Florence L. Wong  Ray W. Sliter  James E. Conrad 《Marine Geophysical Researches》2009,30(3):193-206

Small, steep, uplifting coastal watersheds are prolific sediment producers that contribute significantly to the global marine sediment budget. This study illustrates how sedimentation evolves in one such system where the continental shelf is largely sediment-starved, with most terrestrial sediment bypassing the shelf in favor of deposition in deeper basins. The Santa Barbara–Ventura coast of southern California, USA, is considered a classic area for the study of active tectonics and of Tertiary and Quaternary climatic evolution, interpretations of which depend upon an understanding of sedimentation patterns. High-resolution seismic-reflection data over >570 km² of this shelf show that sediment production is concentrated in a few drainage basins, with the Ventura and Santa Clara River deltas containing most of the upper Pleistocene to Holocene sediment on the shelf. Away from those deltas, the major factor controlling shelf sedimentation is the interaction of wave energy with coastline geometry. Depocenters containing sediment 5–20 m thick exist opposite broad coastal embayments, whereas relict material (bedrock below a regional unconformity) is exposed at the sea floor in areas of the shelf opposite coastal headlands. Locally, natural hydrocarbon seeps interact with sediment deposition either to produce elevated tar-and-sediment mounds or as gas plumes that hinder sediment settling. As much as 80% of fluvial sediment delivered by the Ventura and Santa Clara Rivers is transported off the shelf (some into the Santa Barbara Basin and some into the Santa Monica Basin via Hueneme Canyon), leaving a shelf with relatively little recent sediment accumulation. Understanding factors that control large-scale sediment dispersal along a rapidly uplifting coast that produces substantial quantities of sediment has implications for interpreting the ancient stratigraphic record of active and transform continental margins, and for inferring the distribution of hydrocarbon resources in relict shelf deposits.  相似文献   

Spurious diapycnal mixing in terrain-following coordinate models: The problem and a solution   总被引：5，自引：0，他引：5  

Patrick Marchesiello  Laurent Debreu  Xavier Couvelard 《Ocean Modelling》2009,26(3-4):156-169

In this paper, we identify a crucial numerical problem in sigma coordinate models, leading to unacceptable spurious diapycnal mixing. This error is a by-product of recent advances in numerical methods, namely the implementation of high-order diffusive advection schemes. In the case of ROMS, spurious mixing is produced by its third-order upwind advection scheme, but our analysis suggests that all diffusive advection schemes would behave similarly in all sigma models. We show that the common idea that spurious mixing decreases with resolution is generally false. In a coarse-resolution regime, spurious mixing increases as resolution is refined, and may reach its peak value when eddy-driven lateral mixing becomes explicitly resolved. At finer resolution, diffusivities are expected to decrease but with values that only become acceptable at resolutions finer than the kilometer. The solution to this problem requires a specifically designed advection scheme. We propose and validate the RSUP3 scheme, where diffusion is split from advection and is represented by a rotated biharmonic diffusion scheme with flow-dependent hyperdiffusivity satisfying the Peclet constraint. The rotated diffusion operator is designed for numerical stability, which includes improvements of linear stability limits and a clipping method adapted to the sigma-coordinate. Realistic model experiments in a southwest Pacific configuration show that RSUP3 is able to preserve low dispersion and diffusion capabilities of the original third-order upwind scheme, while preserving water mass characteristics. There are residual errors from the rotated diffusion operator, but they remain acceptable. The use of a constant diffusivity rather than the Peclet hyperdiffusivity tends to increase these residual errors which become unacceptable with Laplacian diffusion. Finally, we have left some options open concerning the use of time filters as an alternative to spatial diffusion. A temporal discretization approach to the present problem (including implicit discretization) will be reported in a following paper.  相似文献   

Parameter estimation for basin-scale ecosystem-linked population models of large pelagic predators: Application to skipjack tuna   总被引：2，自引：1，他引：1  

Inna Senina  John Sibert  Patrick Lehodey 《Progress in Oceanography》2008,78(4):319-335

A Spatial Ecosystem and Population Dynamic Model (SEAPODYM) is used in a data assimilation study aiming to estimate model parameters that describe dynamics of Pacific skipjack tuna population on ocean-based scale. The model based on advection–diffusion–reaction equations explicitly predicts spatial dynamics of large pelagic predators, while taking into account data on several mid-trophic level components, oceanic primary productivity and physical environment. In order to improve its quantitative ability, the model was parameterized through assimilation with commercial fisheries data, and optimization was carried out using maximum likelihood estimation approach. To address the optimization task we implemented an adjoint technique to obtain an exact, analytical evaluation of the likelihood gradient. We conducted a series of computer experiments in order to (i) determine model sensitivity with respect to variable parameters and, hence, investigate their observability; (ii) estimate observable parameters and their errors; and (iii) justify the reliability of the computed solution. Parameters describing recruitment, movement, habitat preferences, natural and fishing mortality of skipjack population were analysed and estimated. Results of the study suggest that SEAPODYM with achieved parameterization scheme can help to investigate the impact of fishing under various management scenarios, and also conduct forecasts of a given species stock and spatial dynamics in a context of environmental and climate changes.  相似文献   

The Belgian sandy beach ecosystem: a review     

Jeroen Speybroeck  Dries Bonte  Wouter Courtens  Tom Gheskiere  Patrick Grootaert  Jean-Pierre Maelfait  Sam Provoost  Koen Sabbe  Eric W. M. Stienen  Vera Van Lancker  Wouter Van Landuyt  Magda Vincx  & Steven Degraer 《Marine Ecology》2008,29(S1):171-185

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Spatiotemporal aspects of silica buffering in restored tidal marshes     

Sander Jacobs  Eric Struyf  Tom Maris  Patrick Meire 《Estuarine, Coastal and Shelf Science》2008

Losses of pelagic diatom production resulting from silica limitation have not only been blamed for toxic algal blooms, but for the reduction in ability of coastal food webs to support higher trophic levels. Recent research has shown the importance of advective seepage water fluxes of dissolved silica (DSi) from freshwater marshes to pelagic waters during moments of riverine Si-limitation. In this study, we investigated the potential impact of recently installed new tidal areas along the Schelde estuary, located in former polder areas and characterized by so-called controlled reduced tidal regimes (CRT). Nine mass-balance studies were conducted in a newly constructed CRT in the freshwater Schelde estuary. During complete tidal cycles both DSi and amorphous silica (ASi) concentrations were monitored at the entrance culverts and in different habitats in the marsh. A swift DSi-delivery capacity was observed despite the shifted spatiotemporal frame of exchange processes compared to reference marshes. As silica-accumulating vegetation is not yet present, and difference with reference marshes’ deliveries is surprisingly small, we indicate diatomaceous debris and phytoliths to be the main silica source. Although further research is necessary on the driving forces of the different processes involved, restoration of former agricultural areas under CRT-regime provide the potential to buffer silica in the estuary.  相似文献   

Dissolved aluminium and the silicon cycle in the Arctic Ocean   总被引：1，自引：0，他引：1  

R. Middag  H.J.W. de Baar  P. Laan  K. Bakker 《Marine Chemistry》2009,115(3-4):176-195

Concentrations of dissolved (0.2 µm filtered) aluminium (Al) have been determined for the first time in the Eurasian part of the Arctic Ocean over the entire water column during expedition ARK XXII/2 aboard R.V. Polarstern (2007). An unprecedented number of 666 samples was analysed for 44 stations along 5 ocean transects. Dissolved Al in surface layer water (SLW) was very low, close to 1 nM, with lowest SLW concentrations towards the Canadian part of the Arctic Ocean and higher values adjacent to and in the shelf seas. The low SLW concentrations indicate no or little influence from aeolian dust input. Dissolved Al showed a nutrient-type increase with depth up to 28 nM, but large differences existed between the different deep Arctic basins. The differences in concentrations of Al between water masses and basins could largely be related to the different origins of the water masses. In the SLW and intermediate water layers, Atlantic and Pacific inflows were of importance. Deep shelf convection appeared to influence the Al distribution in the deep Eurasian Basin. The Al distribution of the deep Makarov Basin provides evidence for Eurasian Basin water inflow into the deep Makarov Basin. A strong correlation between Al and Silicon (Si) was observed in all basins. This correlation and the nutrient-like profile indicate a strong biological influence on the cycling and distribution of Al. The biological influence can be direct by the incorporation of Al in biogenic silica, indirect by preferential scavenging of Al onto biogenic siliceous particles, or by a combination of both processes. From the slope of the overall Al–Si relationship in the intermediate water layer (AIDW; ~ 200–2000 m depth), an Al/Si ratio of 2.2 atoms Al per 1000 atoms Si was derived. This ratio is consistent with the range of previously reported Al/Si uptake ratio in biogenic opal frustules of diatoms. In the deepest waters (>2000 m depth) a steeper slope of the Al–Si relationship of 7.4 to 13 atoms Al per 1000 atoms Si likely results from entrainment of cold shelf water into the deep basins, carrying the signal of dissolution of terrigenous particles with a much higher Al:Si ratio of crustal abundance. Only a small enrichment with such crustal Al and Si component may readily account for the higher Al:Si slope in the deepest waters.  相似文献   

Mesoscale distribution of zooplankton biomass in the northeast Atlantic Ocean determined with an Optical Plankton Counter: Relationships with environmental structures     

Jean-Philippe Labat  Stephane Gasparini  Laure Mousseau  Louis Prieur  Marc Boutoute  Patrick Mayzaud   《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(10):1742-1756

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