Using an individual-based model to examine the roles of habitat fragmentation and behavior on predator–prey relationships in seagrass landscapes     

Kevin A. Hovel  Helen M. Regan 《Landscape Ecology》2008,23(1):75-89

Seagrasses, which form critical subtidal habitats for marine organisms worldwide, are fragmented via natural processes but are increasingly being fragmented and degraded by boating, fishing, and coastal development. We constructed an individual-based model to test how habitat fragmentation and loss influenced predator–prey interactions and cohort size for a group of settling juvenile blue crabs (Callinectes sapidus Rathbun) in seagrass landscapes. Using results from field studies suggesting that strong top-down processes influence the relationship between cannibalistic blue crab populations and seagrass landscape structure, we constructed a model in which prey (juvenile blue crabs) are eaten by mesopredators (larger blue crabs) which in turn are eaten by top-level predators (e.g., large fishes). In our model, we varied the following parameters within four increasingly fragmented seagrass landscapes to test for their relative effects on cohort size: juvenile blue crab (prey) predator avoidance response, hunting ability of mesopredators and predators, the presence of a top-level predator, and prey settlement routines. Generally, prey cohort size was maximized in the presence of top-level predators and when mesopredators and predators exhibited random searching behavior vs. directed hunting. Cohort size for stationary (tethered) prey was maximized in fragmented landscapes, which corresponds to results from field experiments, whereas mobile prey able to detect and avoid predators had higher survival in continuous landscapes. Prey settlement patterns had relatively small influences on cohort size. We conclude that the effects of seagrass fragmentation and loss on organisms such as blue crabs will depend heavily on behaviors of prey and predatory organisms and how these behaviors change with landscape structure.  相似文献   

Dry-matter production and botanical composition of multispecies and perennial ryegrass swards under varying defoliation management     

Shona Baker  Mary B. Lynch  Fionnuala Godwin  Eugene Brennan  Tommy M. Boland  Alexander C. O. Evans  Alan K. Kelly  Helen Sheridan 《Grass and Forage Science》2023,78(3):390-401

Multispecies swards, comprised of different plant functional groups have comparable production potential to high N input L. perenne swards at reduced N when legumes are included. However, information on the appropriate management of multispecies swards is limited. The effect of differing management practices on the herbage dry-matter (DM) production and botanical composition of different sward types was investigated using a 3 × 2 × 2 factorial design plot experiment. The experiment consisted of three sward types: L. perenne-only receiving (LP; 250 kg N ha⁻¹ a⁻¹); L. perenne-Trifolium repens (LP-TR); multispecies sward containing L. perenne, Phleum pratense, Trifolium repens, Trifolium pratense, Plantago lanceolata and Cichorium intybus (MSS). LP-TR and MSS received 90 kg N ha⁻¹ a⁻¹. Harvesting of plot herbage took place every 21 or 28 days to a defoliation height of 4 or 6 cm, over two growing seasons (March to November 2020 and 2021 inclusive). Annual herbage produced by both LP and LP-TR was not significantly affected by defoliation frequency. However, MSS produced 1923 kg DM ha⁻¹ a⁻¹ more herbage when harvested less frequently. Unsown species contributed significantly less to the herbage DM of MSS compared to LP and LP-TR and remained similar in 2020 and 2021, whereas the contribution of unsown species to herbage DM increased in LP and LP-TR from 2020 to 2021, with noxious species more associated with LP and LP-TR than MSS. Results demonstrate the role of multispecies swards in improving the sustainability of grass-based agricultural systems in an environment of reduced fertilizer inputs.  相似文献   

Seasonal movements of immature Kemp's ridley sea turtles (Lepidochelys kempii) in the northern gulf of Mexico          下载免费PDF全文

Andrew T. Coleman  Jonathan L. Pitchford  Helen Bailey  Moby Solangi 《水产资源保护:海洋与淡水生态系统》2017,27(1):253-267

Effect of an intensive mechanical removal effort on a population of non‐native rainbow trout Oncorhynchus mykiss in a South African headwater stream          下载免费PDF全文

Jeremy Shelton  Olaf Weyl  Johannes Van Der Walt  Sean Marr  Dean Impson  Kristine Maciejewski  Donovan Tye  Helen Dallas  Karen Esler 《水产资源保护:海洋与淡水生态系统》2017,27(5):1051-1055

Heat-Induced Fragmentation of the Maize Waxy Protein During Protein Extraction from Starch Granules     

Helen He Mu  Chen Mu-Forster  Monica Bohonko  Bruce P. Wasserman 《Cereal Chemistry》1998,75(4):480-483

The starch granule of maize contains a characteristic set of tightly bound polypeptides. Granule-associated polypeptides are typically extracted from starch granules by heating starch granule suspensions at 90–100°C in a detergent such as SDS. Solubilized proteins are recovered by centrifugation and analyzed by gel electrophoresis. Previously identified tightly bound granule intrinsic proteins consist of the 85-kDa starch-branching enzyme IIb, the 76-kDa starch synthase I, and the 60-kD waxy (Wx) protein, also known as granule-bound starch synthase I. However, SDS extracts from starch granules of maize also contain a cluster of proteins ranging in mass between 47 and 32 kDa In this study, we analyzed this group of granule-associated proteins and found that each was recognized by the Wx antibody. A 15 amino acid N-terminal sequence from the 47-kDa polypeptide was identical to the predicted N-terminus of the Wx protein. Further analysis revealed that each immunoreactive polypeptide between 47 and 32 kDa was a heat-induced fragmentation product of the Wx protein. Conditions for the extraction of granule proteins were evaluated. Our results demonstrate that granule proteins are effectively released by mild extraction (10-min incubation at 72°C). Relative to the Wx protein, starch synthase I and starch branching enzyme IIb were less susceptible to thermal fragmentation. These results demonstrate that the 85-, 76-, and 60-kDa polypeptides are authentic granule-intrinsic proteins, and that the majority of polypeptides between 47 and 32 kDa are artifacts of high-temperature granule extraction procedures.  相似文献   

Effects of a highly purified fucoidan from Undaria pinnatifida on growth performance and intestine health status of gibel carp Carassius auratus gibelio     

Hao Cui  Zhaoguang Wang  Jun Liu  Yexiaoxu Wang  Zhenxing Wang  Jianping Fu  Zhenyu Wan  Ruodan Li  Qingwen Li  Janet Helen Fitton  Yi Liu  Ming Zhang 《Aquaculture Nutrition》2020,26(1):47-59

A six‐week feeding trial was conducted to determine the effects of different concentrations of fucoidan (1 g/kg, 10 g/kg and 30 g/kg; w/w) from Undaria pinnatifida on gibel carp (Carassius auratus gibelio). Our results demonstrated that 30 g/kg fucoidan significantly increased (p < .05) growth performance, intestinal digestive enzyme activities, acid phosphatase activity and immunoglobulin M content. Histological examinations revealed that gibel carp receiving 30 g/kg fucoidan had significant higher abundance of mucin‐containing goblet cells in middle and distal intestine as compared with control treatment (p < .05). Intestinal microbiota analysis showed that 30 g/kg fucoidan supplementation significantly increased (p < .05) the abundance of Cetobacterium and Aeromonas, but lowered (p < .05) the prevalence of pathogenic bacteria Plesiomonas and a mucin‐degrading bacterium Mucinivorans. Furthermore, RNA‐seq and RT‐qPCR analysis indicated that 30 g/kg fucoidan caused significant changes (p < .05) in the expression of genes involved in immune regulation (such as interleukin‐8 and cyclooxygenase), signal transduction (such as phosphatidylinositol‐4,5‐bisphosphate 3‐kinase and protein kinase B) and nutrition utilization (maltase–glucoamylase and muscarinic acetylcholine receptor 3). Together, the current study shows that fucoidan supplementation could elevate the activity of intestinal digestive enzymes, modulate intestinal microbial communities and potentiate a higher state of immune readiness, which might consequently improve growth performance and intestine health status of gibel carp.  相似文献   

Effect of pancreas disease caused by SAV 2 on protein and fat digestion in Atlantic salmon     

Magnus Vikan Rsg  Espen Rimstad  Arne Guttvik  Brd Skjelstad  Eldar sgard Bendiksen  se Helen Garseth 《Journal of fish diseases》2019,42(1):97-108

Salmonid alphavirus (SAV) causes pancreas disease (PD) in farmed Atlantic salmon (Salmo salar L.), and exocrine pancreas tissue is a primary target of the virus. Digestive enzymes secreted by the exocrine pancreas break down macromolecules in feed into smaller molecules that can be absorbed. The effect of SAV infection on digestion has been poorly studied. In this study, longitudinal observations of PD outbreaks caused by SAV subtype 2 (SAV2) in Atlantic salmon at two commercial sea sites were performed. The development of PD was assessed by measurement of SAV2 RNA load and evaluation of histopathological lesions typical of PD. Reduced digestion of both protein and fat co‐varied with the severity of PD lesions and viral load. Also, the study found that during a PD outbreak, the pen population comprise several subpopulations, with different likelihoods of being sampled. The body length of sampled fish deviated from the expected increase or steady state over time, and the infection status in sampled fish deviated from the expected course of infection in the population. Both conditions indicate that disease status of the individual fish influenced the likelihood of being sampled, which may cause sampling bias in population studies.  相似文献   

Nitrogen transformation rates and N<Subscript>2</Subscript>O producing pathways in two pasture soils     

Ting Lan  Helen Suter  Rui Liu  Xuesong Gao  Deli Chen 《Journal of Soils and Sediments》2018,18(9):2970-2979

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A proposed framework for accelerating technology trajectories in agriculture: a case study in China     

Beth CLARK  Glyn D. JONES  Helen KENDALL  James TAYLOR  Yiying CAO  Wenjing LI  Chunjiang ZHAO  Jing CHEN  Guijun YANG  Liping CHEN  Zhenhong LI  Rachel GAULTON  Lynn J. FREWER 《农业科学与工程前沿(英文版)》2018,5(4):485

Precision agriculture (PA) technologies have great potential for promoting sustainable intensification of food production, ensuring targeted delivery of agricultural inputs, and hence food security and environmental protection. The benefits of PA technologies are applicable across a broad range of agronomic, environmental and rural socio-economic contexts globally. However, farmer and land-manager adoption in low to middle income countries has typically been slower than that observed in more affluent countries. China is currently engaged in the process of agricultural modernisation to ensure food security for its 1.4 billion population and has developed a portfolio of policies designed to improve food security, while simultaneously promoting environmental protection. Particular attention has been paid to the reduction of agricultural inputs such as fertilisers and pesticides. The widespread adoption of PA technologies across the Chinese agricultural landscape is central to the success of these policies. However, socio-economic and cultural barriers, farm scale, (in particular the prevalence of smaller family farms) and demographic changes in the rural population, (for example, the movement of younger people to the cities) represent barriers to PA adoption across China. A framework for ensuring an acceptable and accelerated PA technology trajectory is proposed which combines systematic understanding of farmer and end-user priorities and preferences for technology design throughout the technology development process, and subsequent end-user requirements for implementation (including demonstration of economic and agronomic benefits, and knowledge transfer). Future research will validate the framework against qualitative and quantitative socio-economic, cultural and agronomic indicators of successful, or otherwise, PA implementation. The results will provide the evidence upon which to develop further policies regarding how to secure sustainable food production and how best to implement PA in China, as well as practical recommendations for optimising end-user uptake.  相似文献   

Effects of 3,4-dimethylpyrazole phosphate (DMPP) on nitrification and the abundance and community composition of soil ammonia oxidizers in three land uses     

Xiuzhen Shi  Hangwei Hu  Jizheng He  Deli Chen  Helen Charlotte Suter 《Biology and Fertility of Soils》2016,52(7):927-939

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