scholarly journals Geographical and Seasonal Thermal Sensitivity of Grazing Pressure by Microzooplankton in Contrasting Marine Ecosystems

2021 ◽  
Vol 12 ◽  
Author(s):  
Marco J. Cabrerizo ◽  
Emilio Marañón
Keyword(s):  
Thermal Sensitivity ◽  
Grazing Pressure ◽  
Open Ocean ◽  
Effect Of Temperature ◽  
Extensive Literature ◽  
Thermal Dependence ◽  
Food Web Structure ◽  
Element Cycling ◽  
Large Variability ◽  
Microzooplankton Grazing

Grazing pressure, estimated as the ratio between microzooplankton grazing and phytoplankton growth rates (g:μ), is a strong determinant of microbial food-web structure and element cycling in the upper ocean. It is generally accepted that g is more sensitive to temperature than μ, but it remains unknown how the thermal dependence (activation energy, Ea) of g:μ varies over spatial and temporal scales. To tackle this uncertainty, we used an extensive literature analysis obtaining 751 paired rate estimates of μ and g from dilution experiments performed throughout the world’s marine environments. On a geographical scale, we found a stimulatory effect of temperature in polar open-ocean (∼0.5 eV) and tropical coastal (∼0.2 eV) regions, and an inhibitory one in the remaining biomes (values between −0.1 and −0.4 eV). On a seasonal scale, the temperature effect on g:μ ratios was stimulatory, particularly in polar environments; however, the large variability existing between estimates resulted in non-significant differences among biomes. We observed that increases in nitrate availability stimulated the temperature dependence of grazing pressure (i.e., led to more positive Ea of g:μ) in open-ocean ecosystems and inhibited it in coastal ones, particularly in polar environments. The percentage of primary production grazed by microzooplankton (∼56%) was similar in all regions. Our results suggest that warming of surface ocean waters could exert a highly variable impact, in terms of both magnitude and direction (stimulation or inhibition), on microzooplankton grazing pressure in different ocean regions.

Cardiovascular and metabolic responses to temperature in Coluber constrictor

1987 ◽  
Vol 253 (2) ◽  
pp. R222-R227 ◽  
Author(s):  
J. N. Stinner
Keyword(s):  
Blood Pressure ◽  
Body Temperature ◽  
Stroke Volume ◽  
Minute Ventilation ◽  
Marked Change ◽  
Effect Of Temperature ◽  
Metabolic Demand ◽  
Thermal Dependence ◽  
Arterial Blood ◽  
Coluber Constrictor

The cardiovascular adjustments associated with elevated metabolic demand caused by rising body temperature were investigated in Coluber constrictor. From 16 to 35 degrees C, O2 consumption increased roughly ninefold. Systemic blood flow, determined by the Fick method, increased approximately 4.5-fold and arteriovenous O2 difference increased approximately 2-fold. Heart rate steadily increased over the temperature range examined. At the cooler temperatures stroke volume also increased but, above approximately 25 degrees C, stroke volume declined with rising temperature. The changes in stroke volume may result from the direct effect of temperature on myocardial contractility. The thermal dependence of blood convection requirement in C. constrictor is similar to changes in air convection requirement determined in a previous study. Consequently the minute ventilation-to-perfusion ratio appears to be independent of temperature, at least from 20 to 35 degrees C. Systemic arterial blood pressure increases with rising body temperature due to the rise in cardiac output, whereas vascular resistance declines. Blood pressure in snakes disturbed by the investigator is roughly two times higher than in resting animals at all temperatures studied. This marked change in blood pressure suggests an "alarm reaction" mediated by the sympathetic nervous system.

scholarly journals Preferred temperature and thermal breadth of birds wintering in peninsular Spain – the limited effect of temperature on species distribution

2016 ◽  
Author(s):  
Luis M. Carrascal ◽  
Sara Villén-Pérez ◽  
David Palomino
Keyword(s):  
Species Abundance ◽  
Bird Species ◽  
Effect Of Temperature ◽  
Response Curves ◽  
Large Variability ◽  
Preferred Temperature ◽  
Mean Temperature ◽  
The Mean ◽  
Thermal Preferences ◽  
Peninsular Spain

Background. Availability of environmental energy, as measured by temperature, is expected to limit the abundance and distribution of endotherms wintering at temperate latitudes. A prediction of this hypothesis is that birds should attain their highest abundances in warmer areas. However, there may be a spatial mismatch between species preferred habitats and species preferred temperatures, so some species might end-up wintering in sub-optimal thermal environments. Methods. We model the influence of minimum winter temperature on the relative abundance of 106 terrestrial bird species wintering in peninsular Spain, at 10x10 Km2 resolution, using 95%-quantile regressions. We analyze general trends across species on the shape of the response curves, the environmental preferred temperature (at which the species abundance is maximized), the mean temperature in the area of distribution and the thermal breadth (area under the abundance-temperature curve). Results. There is a large interspecific variability on the thermal preferences and specialization of species. Despite this large variability, there is a preponderance of positive relationships between species abundance and temperature, and on average species attain their maximum abundances in areas 1.9 ºC warmer than the average temperature available in peninsular Spain. The mean temperature in the area of distribution is lower than the thermal preferences of the species, although both parameters are highly correlated. Discussion. Most species prefer the warmest environments to overwinter, which suggests that temperature imposes important restrictions to birds wintering in the Iberian Peninsula. However, most individuals overwinter in locations colder than the species thermal preferences, probably reflecting a limitation of environments combining habitat and thermal preferences. Beyond these general trends, there is a high inter-specific variation in the versatility of species using the available thermal space .

Coastal carbon transfer in the past - a box model study

2021 ◽  
Author(s):  
Anne Kruijt ◽  
Jack Middelburg ◽  
Appy Sluijs
Keyword(s):  
Carbon Cycle ◽  
Coastal Zone ◽  
Light Attenuation ◽  
Global Carbon Cycle ◽  
Open Ocean ◽  
Box Model ◽  
Zone Model ◽  
Large Variability ◽  
Carbon Transfer ◽  
Global Carbon

<p>The shelf represents a relatively small fraction of global oceanic area but plays an important role in the global carbon cycle because of high production and burial of organic matter and calcium carbonate. Biological processes on the shelf can greatly alter the partial pressure of dissolved CO2, causing disequilibrium with the atmosphere and fluxes significantly larger than those in the open ocean. Also the transport of major ions from land to open ocean is mediated by shelf processes. Available models resolving the governing processes are typically designed to simulate specific regions. Global carbon cycle models typically implement all shelf processes in one simple box. Global earth system models typically impose a flux of riverine export products from land directly into the open ocean without accounting for processes in the coastal zone. However, the global role of the coastal zone in the carbon cycle on various time scales remains poorly quantified, partly due to the large variability in continental margin environments, hampering proper understanding of past, present and future global carbon cycle dynamics.<br>We develop a new coastal zone model that links river biogeochemistry with open ocean models, focusing on the transfer of carbon. Our first approach represents a box model in which number, size and depth of boxes can be varied. We apply global fluxes of carbon into the system and include functions describing first order organic and inorganic carbon processes in each of the boxes. With this conceptual model of the coastal zone we aim to test the effect of changes in bathymetry, temperature and light attenuation on the way carbon is transferred through the coastal interface, suitable for paleo and future applications.</p>

scholarly journals Warming effect on nitrogen fixation in Mediterranean macrophyte sediments

2019 ◽  
Vol 16 (1) ◽  
pp. 167-175 ◽  
Author(s):  
Neus Garcias-Bonet ◽  
Raquel Vaquer-Sunyer ◽  
Carlos M. Duarte ◽  
Núria Marbà
Keyword(s):  
N2 Fixation ◽  
Thermal Sensitivity ◽  
Thermal Response ◽  
Sharp Decrease ◽  
Posidonia Oceanica ◽  
Global Ocean ◽  
Thermal Dependence ◽  
High Productivity ◽  
Marine Macrophytes ◽  
The Impact

Abstract. The Mediterranean Sea is warming faster than the global ocean, with important consequences for organisms and biogeochemical cycles. Warming is a major stressor for key marine benthic macrophytes. However, the effect of warming on marine N2 fixation remains unknown, despite the fact that the high productivity of macrophytes in oligotrophic waters is partially sustained by the input of new nitrogen (N) into the system by N2 fixation. Here, we assess the impact of warming on the N2 fixation rates of three key marine macrophytes: Posidonia oceanica, Cymodocea nodosa, and Caulerpa prolifera. We experimentally measured N2 fixation rates in vegetated and bare sediments at temperatures encompassing current summer mean (25 and 27 ∘C), projected summer mean (29 and 31 ∘C), and projected summer maximum (33 ∘C) seawater surface temperatures (SSTs) by the end of the century under a scenario of moderate greenhouse gas emissions. We found that N2 fixation rates in vegetated sediments were 2.8-fold higher than in bare sediments at current summer mean SST, with no differences among macrophytes. Currently, the contribution of N2 fixation to macrophyte productivity could account for up to 7 %, 13.8 %, and 1.8 % of N requirements for P. oceanica, C. nodosa, and C. prolifera, respectively. We show the temperature dependence of sediment N2 fixation rates. However, the thermal response differed for vegetated sediments, in which rates showed an optimum at 31 ∘C followed by a sharp decrease at 33 ∘C, and bare sediments, in which rates increased along the range of the experimental temperatures. The activation energy and Q10 were lower in vegetated than bare sediments, indicating the lower thermal sensitivity of vegetated sediments. The projected warming is expected to increase the contribution of N2 fixation to Mediterranean macrophyte productivity. Therefore, the thermal dependence of N2 fixation might have important consequences for primary production in coastal ecosystems in the context of warming.

scholarly journals Integrating bioenergetics and conservation biology: thermal sensitivity of digestive performance in Eastern Collared Lizards (Crotaphytus collaris) may affect population persistence

2020 ◽  
Vol 8 (1) ◽  
Author(s):  
Casey L Brewster ◽  
Jason Ortega ◽  
Steven J Beaupre
Keyword(s):  
Thermal Sensitivity ◽  
Metabolizable Energy ◽  
Effect Of Temperature ◽  
Valuable Insight ◽  
Feeding Rates ◽  
Crotaphytus Collaris ◽  
Reduced Body ◽  
Heat Loads ◽  
Passage Times ◽  
Collared Lizards

Abstract Information on bioenergetics can provide valuable insight into the ecology, life history and population dynamics of organisms. For ectothermic animals, thermal sensitivity of digestion is an important determinant of net assimilated energy budgets. A recent study in the Ozark Mountains indicated that eastern collared lizards (Crotaphytus collaris) restricted to encroached glades (characterized by woody vegetation encroachment) experience reduced environmental heat loads and have reduced age-specific growth and reproductive rates compared to populations in intact glades. To assess the potential impact of reduced body temperatures on assimilation rates of C. collaris in encroached glades, we conducted feeding trials across four temperature treatments (28, 31, 34 and 37°C). We tested for temperature effects on voluntary feeding rates, passage times, apparent assimilated energy (AE) and metabolizable energy (ME). Passage times decreased and voluntary feeding rates increased significantly with increasing temperature. Consumption explained the majority of variance in AE and ME, followed by the effect of temperature treatments. Using data on voluntary feeding rates, passage times and ME as a function of temperature, we estimated over a 10-fold increase in predicted daily assimilated energy across temperature treatments (28°C = 0.58 kJ/day, 31°C = 1.20 kJ/day, 34°C = 4.30 kJ/day, 37°C = 7.95 kJ/day). Thus, lower heat loads in encroached glades may cause reduced body temperature and result in restricted energy assimilation rates. Our study provides a novel approach to the integration of bioenergetics and conservation and shows the efficacy of using information on digestive performance to investigate underlying mechanisms in a conservation context.

scholarly journals Fungi and viruses as important players in microbial mats

2020 ◽  
Vol 96 (11) ◽  
Author(s):  
Cátia Carreira ◽  
Christian Lønborg ◽  
Michael Kühl ◽  
Ana I Lillebø ◽  
Ruth-Anne Sandaa ◽  
...  
Keyword(s):  
Organic Matter ◽  
Aquatic Ecosystems ◽  
Microbial Mats ◽  
Freshwater Ecosystems ◽  
Food Web Structure ◽  
Element Cycling ◽  
Functional Roles ◽  
Web Structure ◽  
Experimental Approaches ◽  
And Function

ABSTRACT Microbial mats are compacted, surface-associated microbial ecosystems reminiscent of the first living communities on early Earth. While often considered predominantly prokaryotic, recent findings show that both fungi and viruses are ubiquitous in microbial mats, albeit their functional roles remain unknown. Fungal research has mostly focused on terrestrial and freshwater ecosystems where fungi are known as important recyclers of organic matter, whereas viruses are exceptionally abundant and important in aquatic ecosystems. Here, viruses have shown to affect organic matter cycling and the diversity of microbial communities by facilitating horizontal gene transfer and cell lysis. We hypothesise fungi and viruses to have similar roles in microbial mats. Based on the analysis of previous research in terrestrial and aquatic ecosystems, we outline novel hypotheses proposing strong impacts of fungi and viruses on element cycling, food web structure and function in microbial mats, and outline experimental approaches for studies needed to understand these interactions.

An Inverse Model Analysis of Planktonic Food Webs in Experimental Lakes

1994 ◽  
Vol 51 (9) ◽  
pp. 2034-2044 ◽  
Author(s):  
Alain F. Vézina ◽  
Michael L. Pace
Keyword(s):  
Food Web ◽  
Heterotrophic Bacteria ◽  
Grazing Pressure ◽  
Inverse Methods ◽  
Trophic Levels ◽  
Microbial Food Web ◽  
Food Web Structure ◽  
Planktonic Food ◽  
Size Groups ◽  
The Impact

We used inverse methods to reconstruct carbon flows in experimental lakes where the fish community had been purposely altered. These analyses were applied to three years of data from a reference lake and two experimental lakes located in Gogebic County, Michigan. We reconstructed seasonally averaged flows among two size groups of phytoplankton, heterotrophic bacteria, microzooplankton, cladocerans, and copepods. The inverse analysis produced significantly different flow networks for the different lakes that agreed qualitatively with known chemical and biological differences between lakes and with other analyses of the impact of fish manipulations on food web structure and dynamics. The results pointed to alterations in grazing pressure on the phytoplankton that parallel changes in the size and abundance of cladocerans and copepods among lakes. Estimated flows through the microbial food web indicated low bacterial production efficiencies and small carbon transfers from the microbial food web to the larger zooplankton. This study demonstrates the use of inverse methods to identify and compare flow patterns across ecosystems and suggests that microbial flows are relatively insensitive to changes at the upper trophic levels.

Thermal dependence of food assimilation and locomotor performance in juvenile blue-tailed skinks, Eumeces elegans

2007 ◽  
Vol 57 (1) ◽  
pp. 29-38 ◽  
Author(s):  
Yi-Xin Bao ◽  
Wei-Guo Du ◽  
Lin Shu ◽  
Yi-Wei Lu
Keyword(s):  
Food Intake ◽  
Thermal Sensitivity ◽  
Eastern China ◽  
Assimilation Efficiency ◽  
Age Difference ◽  
Locomotor Performance ◽  
Thermal Dependence ◽  
Physiological Performance ◽  
Effects Of Temperature ◽  
Food Assimilation

AbstractVariation in the physiological performance and behaviour of ectotherms as a result of changes in body temperature can affect important life-history traits. Studies investigating the effects of temperature on physiological performance and behaviour have thus clear ecological significance. We captured juvenile blue-tailed skinks, Eumeces elegans, from a population in Zhejiang, eastern China, and determined the effects of temperature on their food assimilation and locomotor performance. Food intake of the juveniles generally increased with increase in temperatures within the range of 24-30°C and decreased at higher temperatures. The temperature significantly affected the apparent digestive coefficient (ADC) and the assimilation efficiency (AE) of juveniles; the ADC and AE of the skinks at 32°C were higher than those of skinks at other temperatures. The sprint speed increased with increase in temperature within the range of 12-32°C and decreased at higher temperatures. These results suggest the patterns of thermal sensitivity may differ in various functional performances, and hence support the 'multiple optima hypothesis', which suggests that no specific temperature maximises all functional performance. In addition, this study indicates significant between-age difference in thermal physiology by comparing our data with those on adult skinks, including different thermal sensitivity of AE, and different ranges of thermal-performance breadth for food intake and locomotor performance between juvenile and adult E. elegans.

scholarly journals Shaped to kill: The evolution of siphonophore tentilla for specialized prey capture in the open ocean

2019 ◽  
Author(s):  
Alejandro Damian-Serrano ◽  
Steven H.D. Haddock ◽  
Casey W. Dunn
Keyword(s):  
Prey Capture ◽  
Morphological Changes ◽  
Morphological Evolution ◽  
Genetic Correlations ◽  
Prey Type ◽  
Morphological Characters ◽  
Open Ocean ◽  
Food Web Structure ◽  
Dead End ◽  
Modular Structures

AbstractPredator specialization has often been considered an evolutionary ‘dead-end’ due to the constraints associated with the evolution of morphological and functional optimizations throughout the organism. However, in some predators, these changes are localized in separate structures dedicated to prey capture. One of the most extreme cases of this modularity can be observed in siphonophores, a clade of pelagic colonial cnidarians that use tentilla (tentacle side branches armed with nematocysts) exclusively for prey capture. Here we study how siphonophore specialists and generalists evolve, and what morphological changes are associated with these transitions. To answer these questions, we: (1) measured 29 morphological characters of tentacles from 45 siphonophore species, (2) mapped these data to a phylogenetic tree, and (3) analyzed the evolutionary associations between morphological characters and prey type data from the literature. Instead of a dead-end, we found that siphonophore specialists can evolve into generalists, and that specialists on one prey type have directly evolved into specialists on other prey types. Our results show that siphonophore tentillum morphology has strong evolutionary associations with prey type, and suggest that shifts between prey types are linked to shifts in the morphology, mode of evolution, and genetic correlations of tentilla and their nematocysts. The evolutionary history of siphonophore specialization helps build a broader perspective on predatory niche diversification via morphological innovation and evolution. These findings contribute to understanding how specialization and morphological evolution have shaped present-day food webs.Significance StatementPredatory specialization is often associated with the evolution of modifications in the morphology of the prey capture apparatus. Specialization has been considered an evolutionary ‘dead-end’ due to the constraints associated with these morphological changes. However, in predators like siphonophores, armed with modular structures used exclusively for prey capture, this assumption is challenged. Our results show that siphonophores can evolve generalism and new prey-type specializations by modifying the morphological states, modes of evolution, and genetic correlations between the parts of their prey capture apparatus. These findings demonstrate how studying open-ocean non-bilaterian predators can reveal novel patterns and mechanisms in the evolution of specialization. Understanding these evolutionary processes is fundamental to the study of food-web structure and complexity.

scholarly journals Effect of 940 nm Gallium Arsenide Laser on dental hard tissues temperature propagation

2015 ◽  
Vol 18 (4) ◽  
pp. 104
Author(s):  
Javier Higuera ◽  
Ariel Denis Espinoza ◽  
Sebastian Contreras Marino
Keyword(s):  
Laser Radiation ◽  
Temperature Increase ◽  
Effect Of Temperature ◽  
Extensive Literature ◽  
Major Powers ◽  
Pulsed Mode ◽  
Dental Hard Tissues ◽  
Hard Tissues ◽  
Lower Incisors

<p align="left"><span style="color: #212121;"><span><span>Despite the extensive literature available on laser at the present, there are few articles about the temperature of laser radiation and its propagation on dental hard tissues. The present study general objective is to evaluate </span></span></span><span style="color: #212121;"><span><span><em>in vitro</em></span></span></span><span style="color: #212121;"><span><span><span> the effect of temperature increase produced by the laser radiation of 940 nm on the dental hard tissues and, as specific objectives a) analyze current parameters using 940 nm laser on dental hard tissues b) assess the most appropriate criteria for this wavelength on dental hard tissues. 4 groups of 5 teeth each (lower incisors, upper incisors, canines and molars) were irradiated with 6 powers and frequencies (0.1 to 0.4W, in continuous or pulsed mode). The results of this study allow us to ensure that, in the chosen parameters, major powers, but delivered in pulsed manner, generate less temperature rise. Extremely significant differences were found between groups of lower incisors and molars. 0.1W power, pulsed mode for 20 msec, with 20 millisecond intervals, generated less than 4 Celsius degrees of temperature increase in all the cases studied. In conclusion, the use of powers of up to 0.4W, in pulsed mode, generated thermal effects of less than 4 Celsius degrees.</span></span></span></span></p>

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