Species‐specific photosynthetic responses of symbiotic zoanthids to thermal stress and ocean acidification          下载免费PDF全文

Erin R. Graham  Robert W. Sanders 《Marine Ecology》2016,37(2):442-458

Increasing sea‐surface temperatures and ocean acidification (OA) are impacting physiologic processes in a variety of marine organisms. Many sea anemones, corals and jellies in the phylum Cnidaria form endosymbiotic relationships with Symbiodinium spp. (phylum Dinoflagellata) supply the hosts with fixed carbon from photosynthesis. Much work has focused on the generally negative effects of rising temperature and OA on calcification in Symbiodinium‐coral symbioses, but has not directly measured symbiont photosynthesis in hospite or fixed carbon translocation from symbiont to host. Symbiodinium species or types vary in their environmental tolerance and photosynthetic capacity; therefore, primary production in symbiotic associations can vary with symbiont type. However, symbiont type has not been identified in a large portion of Symbiodinium?cnidarian studies. Future climate conditions and OA may favor non‐calcifying, soft‐bodied cnidarians, including zoanthids. Here we show that two zoanthid species, Palythoa sp. and Zoanthus sp., harboring different symbiont types (C1 and A4), had very different responses to increased temperature and increased partial pressure of CO₂ (pCO₂), or dissolved CO₂, and low pH. Thermal stress did not affect carbon fixation or fixed carbon translocation in the Zoanthus sp./A4 association, and high pCO₂/low pH increased carbon fixation. In contrast, both thermal stress and high pCO₂/low pH greatly inhibited carbon fixation in the Palythoa sp./C1 association. However, the combined treatment of high temperature and high pCO₂ increased carbon fixation relative to the treatment of high temperature alone. Our observations support the growing body of evidence that demonstrates that the response of symbiotic cnidarians to thermal stress and OA must be considered on a host‐specific and symbiont‐specific basis. In addition, we show that the effects of increased temperature and pCO₂ on photosynthesis may change when these two stressors are combined. Understanding how carbon fixation and translocation varies among different host?symbiont combinations is critical to predicting which Symbiodinium associations may persist in warm, acidified oceans.  相似文献   

Mats of Beggiatoa bacteria reveal that organic pollution from lumber mills inhibits growth of Zostera marina     

Joel K. Elliott  Erin Spear  & Sandy Wyllie-Echeverria 《Marine Ecology》2006,27(4):372-380

The objectives of this study were to determine the distribution and abundance of Zostera marina (eelgrass) in relation to the distribution of the mat forming bacteria Beggiatoa spp., and the levels of sulfide and organic material (wood waste) in the sediment. Underwater videography and intertidal surveys were used to map the distribution and abundance of Z. marina beds and Beggiatoa in the nearshore area of Commencement Bay, WA (USA), a location that has a long history of sawmill activity. Zostera marina occurred from the intertidal to ?6 m mean lower low water (MLLW) on sandy substrates in areas with low levels of sulfide (<50 μm ) and organic material (<5 % total volatile solids). Areas with high sulfide levels (>200 μm ) occurred where there were significant amounts of organic material in the sediments, which was found to be wood waste that had been discarded from sawmills. Zostera marina was absent from the intertidal and occurred at lower densities in areas with high sulfide levels. In contrast, mats of Beggiatoa were only found in areas where the sulfide levels were >1000 μm and there were significant deposits of wood. Thus, the negative correlation between the distribution and abundance of Z. marina and Beggiatoa suggests that the presence of Beggiatoa mats could be used as a biological indicator of inhibiting levels of hydrogen sulfide in the marine environment.  相似文献   

Statistical testing of a new testate amoeba‐based transfer function for water‐table depth reconstruction on ombrotrophic peatlands in north‐eastern Canada and Maine,United States     

Matthew J. Amesbury  Gunnar Mallon  Dan J. Charman  Paul D. M. Hughes  Robert K. Booth  Timothy J. Daley  Michelle Garneau 《第四纪科学杂志》2013,28(1):27-39

Proxy reconstructions of climatic parameters developed using transfer functions are central to the testing of many palaeoclimatic hypotheses on Holocene timescales. However, recent work shows that the mathematical models underpinning many existing transfer functions are susceptible to spatial autocorrelation, clustered training set design and the uneven sampling of environmental gradients. This may result in over‐optimistic performance statistics or, in extreme cases, a lack of predictive power. A new testate amoeba‐based transfer function is presented that fully incorporates the new recommended statistical tests to address these issues. Leave‐one‐out cross‐validation, the most commonly applied method in recent studies to assess model performance, produced over‐optimistic performance statistics for all models tested. However, the preferred model, developed using weighted averaging with tolerance downweighting, retained a predictive capacity equivalent to other published models even when less optimistic performance statistics were chosen. Application of the new statistical tests in the development of transfer functions provides a more thorough assessment of performance and greater confidence in reconstructions based on them. Only when the wider research community have sufficient confidence in transfer function‐based proxy reconstructions will they be commonly used in data comparison and palaeoclimate modelling studies of broader scientific relevance. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

The application of non‐linear normal mode initialization to an operational forecast model     

Roger Daley 《大气与海洋》2013,51(2):97-124

Abstract

The non‐linear normal mode initialization technique used in shallow water equation models by Baer (1977) and Machenhauer (1977) is now applied to a full baroclinic primitive equations forecast model. The initialization procedure is shown to be capable of completely removing high frequency oscillations from model integrations, even in the presence of topography. The procedure also produces a consistent and physically realistic initial vertical motion field.  相似文献