scholarly journals Chloroplasts of symbiotic microalgae remain active during bleaching induced by thermal stress in Collodaria (Radiolaria)

2018 ◽  
Author(s):  
Emilie Villar ◽  
Vincent Dani ◽  
Estelle Bigeard ◽  
Tatiana Linhart ◽  
Miguel Mendez Sandin ◽  
...  
Keyword(s):  
Thermal Stress ◽  
Global Change ◽  
Biogeochemical Processes ◽  
Natural Conditions ◽  
Symbiotic Interaction ◽  
Respiration Rates ◽  
Ecological Success ◽  
Symbiotic Microalgae ◽  
Photosynthetic Capacities ◽  
Planktonic Communities

AbstractCollodaria (Radiolaria) are important contributors to planktonic communities and biogeochemical processes (e.g. the biologic pump) in oligotrophic oceans. Similarly to corals, Collodaria live in symbiosis with dinoflagellate algae, a relationship that is thought to explain partly their ecological success. In the context of global change, the robustness of the symbiotic interaction and potential subsequent bleaching events are worth consideration. In the present study, we compared the ultrastructure morphology, symbiont density, photosynthetic capacities and respiration rates of colonial Collodaria exposed to a range of temperatures corresponding to natural conditions (21°C), moderate (25°C) and high (28°C) thermal stress. We showed that symbiont density immediately decreased when temperature rises to 25°C and the collodaria holobiont metabolic activity increased. When temperature reached 28°C, the collodarian host arrived at a tolerance threshold with a respiration nearly stopped and largely damaged morphological structures. Over the course of the experiment the photosynthetic capacities of remaining symbionts were stable, chloroplasts being the last degraded organelles from the microalgae. These results contribute to a better characterization and understanding of temperature-induced bleaching processes in planktonic photosymbiosis.

Global change effects on biogeochemical processes of Argentinian estuaries: An overview of vulnerabilities and ecohydrological adaptive outlooks

2015 ◽  
Vol 91 (2) ◽  
pp. 554-562 ◽  
Author(s):  
Germán A. Kopprio ◽  
Florencia Biancalana ◽  
Anna Fricke ◽  
John E. Garzón Cardona ◽  
Ana Martínez ◽  
...  
Keyword(s):  
Global Change ◽  
Biogeochemical Processes

Dormancy, germination and seedling growth of two Kalaharian perennials of the genus Harpagophytum (Pedaliaceae)

1988 ◽  
Vol 4 (2) ◽  
pp. 185-198 ◽  
Author(s):  
W. H. O. Ernst ◽  
T. Tietema ◽  
E. M. Veenendaal ◽  
R. Masene
Keyword(s):  
Gibberellic Acid ◽  
High Temperatures ◽  
Seedling Growth ◽  
Seed Coat ◽  
Growth Rates ◽  
Natural Conditions ◽  
Relative Growth ◽  
Relative Growth Rates ◽  
Respiration Rates ◽  
Drought Avoidance

ABSTRACTDormancy and germination ecology of two Harpagophytum species (Pedaliaceae) from an open Acacia savanna in Botswana were investigated. The maintenance of dormancy is governed partly by the seed coat but mainly by the endosperm and the embryo itself, as demonstrated by removal of the endosperm. Dissemination of the seed from the fruit can be delayed for several years without affecting the viability of the embryo, due to very low respiration rates.Germination can be enhanced slightly by high temperatures under natural conditions, and by gibberellic acid or removal of the endosperm under laboratory conditions. Relative growth rates for both Harpagophytum species are lower than for subtropical grasses and legumes, due to a strong investment in root and tuber biomass. Germination and seedling growth is discussed in relation to the drought avoidance syndrome and the animal disperser syndrome.

scholarly journals Microplastics ingestion and heterotrophy in thermally stressed corals

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Jeremy B. Axworthy ◽  
Jacqueline L. Padilla-Gamiño
Keyword(s):  
Thermal Stress ◽  
Global Change ◽  
Coral Reefs ◽  
Coral Species ◽  
Pocillopora Damicornis ◽  
Montipora Capitata ◽  
Thermally Stressed

AbstractRising sea temperatures and increasing pollution threaten the fate of coral reefs and millions of people who depend on them. Some reef-building corals respond to thermal stress and subsequent bleaching with increases in heterotrophy, which may increase the risk of ingesting microplastics. Whether this heterotrophic plasticity affects microplastics ingestion or whether ingesting microplastics affects heterotrophic feeding in corals is unknown. To determine this, two coral species, Montipora capitata and Pocillopora damicornis, were exposed to ambient (~27 °C) and increased (~30 °C) temperature and then fed microplastics, Artemia nauplii, or both. Following thermal stress, both species significantly reduced feeding on Artemia but no significant decrease in microplastics ingestion was observed. Interestingly, P. damicornis only ingested microplastics when Artemia were also present, providing evidence that microplastics are not selectively ingested by this species and are only incidentally ingested when food is available. As the first study to examine microplastics ingestion following thermal stress in corals, our results highlight the variability in the risk of microplastics ingestion among species and the importance of considering multiple drivers to project how corals will be affected by global change.

A New System for Continuous Respirometry of Small Air-Breathing Invertebrates Under Near-Natural Conditions

1961 ◽  
Vol 38 (2) ◽  
pp. 323-341
Author(s):  
A. MACFADYEN
Keyword(s):  
Natural Conditions ◽  
Copper Sulphate Solution ◽  
Air Breathing ◽  
Temperature Changes ◽  
Diurnal Cycles ◽  
Respiration Rates ◽  
Special Control ◽  
New System ◽  
Better Than

1. A new system of respirometry for long-term experiments on small air-breathing invertebrates is described for use in work where changing temperature conditions are essential. There is no reason why the same system should not be used for larger animals. 2. The respirometer is of the Barcroft, compensating type, isolated from the atmosphere, and has provision for temperature equilibration in the two vessels. 3. Oxygen is automatically replenished by electrolysis of copper sulphate solution in the chamber as it is used by the animal and the rate of replenishment is recorded. 4. The main features in design of such an apparatus, its limitations and accuracy are discussed. The accuracy is comparable with that of a Warburg respirometer and the sensitivity, at better than 0.1 mm.3 of oxygen/hour, is about ten times as great. 5. A special control and recording system has been developed in order to reduce expense and simplify the interpretation of the data from six respirometers over long periods. 6. It is shown that the errors arising from temperature changes can be reduced to acceptable levels for most purposes. The apparatus is therefore suitable for use in the study of acclimatization and of responses to rhythmical temperature changes. 7. Examples of respiration records are given which illustrate the possibilities of being able to follow respiration rates through several diurnal cycles. 8. Practical details of construction are given in the appendices.

Effect of Thermal Stress on Predator Avoidance in Sockeye Salmon

1972 ◽  
Vol 29 (5) ◽  
pp. 601-603 ◽  
Author(s):  
J. R. Sylvester
Keyword(s):  
Thermal Stress ◽  
Predator Avoidance ◽  
Sockeye Salmon ◽  
Coho Salmon ◽  
Oncorhynchus Kisutch ◽  
Acclimation Temperature ◽  
Natural Conditions ◽  
Predator Prey ◽  
Salmon Fry ◽  
Predation Rates

Under laboratory conditions, predation rates of yearling coho salmon (Oncorhynchus kisutch) on sockeye salmon fry (Oncorhynchus nerka) increased with increasing acclimation temperature. Elevated temperature doses significantly decreased survival of sockeye salmon fry. The results suggest that under natural conditions, sudden increases in water temperature could alter predator–prey interactions of some fish by increasing predation mortalities.

Measurement of Lichen Photosynthesis in the Field with a Portable Steady-State Co2-Porometer

1984 ◽  
Vol 16 (1) ◽  
pp. 1-9 ◽  
Author(s):  
O. L. Lange ◽  
Ellen Kilian ◽  
Angelika Meyer ◽  
J. D. Tenhunen
Keyword(s):  
Gas Exchange ◽  
Natural Conditions ◽  
Diurnal Courses ◽  
Respiration Rates ◽  
Mediterranean Habitat ◽  
Portable System ◽  
Exchange Measurement ◽  
Microclimate Conditions ◽  
Photosynthesis And Respiration

AbstractA portable system for CO2 gas exchange measurements is described which allows determination of photosynthesis and respiration rates of lichens (and mosses) in the field under light, humidity and temperature conditions which are close to ambient. Time periods for enclosure of the thalli in a cuvette of this CO2-porometer for gas exchange measurement are shortened to between 1 and 2 min, so that an experimental influence on their water relations is small. Between the periods of gas exchange measurement, the lichens experience their natural microclimate conditions. Thus, measurements approximate closely the true gas exchange rates of the lichens under natural conditions. Diurnal courses of CO2 exchange of lichens found growing in a Mediterranean habitat in the spring are demonstrated, as determined by this method.

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