Population collapse dynamics in Acropora downingi,an Arabian/Persian Gulf ecosystem‐engineering coral,linked to rising temperature

As in the tropical Atlantic, Acropora populations in the southern Persian/Arabian Gulf plummeted within two decades after having been ecosystem engineers on most wave‐exposed reefs since the Pleistocene. Since 1996/1998 live coral cover in the Gulf declined by over 90% in many areas, primarily due to bleaching and diseases caused by rising temperatures. In the formerly dominant table‐coral species A. downingi, population dynamics corresponding to disturbance regimes was quantified in three transition matrices (lower disturbance pre‐1996; moderate disturbance from 1998 to 2010 and 2013 to 2017, disturbed in 1996/1998, 2010/11/12, 2017). Increased disturbance frequency and severity caused progressive reduction in coral size, cover, and population fecundity. Small size‐classes were bolstered more by partial colony mortality than sexual recruitment. Some large corals had a size refuge and resisted die‐back but were also lost with increasing disturbance. Matrix and biophysical larval flow models suggested one metapopulation. Southern, Arabian, populations could be connected to northern, Iranian, populations but this connectivity was lost under assumptions of pelagic larval duration at rising temperatures shortened to a third. Then, the metapopulation disintegrated into isolated populations. Connectivity required to avoid extinctions increased exponentially with disturbance frequency and correlation of disturbances across the metapopulation. Populations became unsustainable at eight disturbances in 15 years, when even highest theoretical recruitment no longer compensated mortality. This lethal disturbance frequency was 3‐fold that of the moderately disturbed monitoring period and 4‐fold of the preceding low‐disturbance period—suggesting ongoing shortening of the disturbance‐free period. Observed population collapse and environmental changes in the Gulf suggest that A. downingi is heading toward at least functional extinction mainly due to increasingly frequent temperature‐induced mortality events, clearly linked to climate change.     

Validation of the binary designation Symbiodinium thermophilum (Dinophyceae)

The binary designation Symbiodinium thermophilum was invalid due to the absence of an illustration as required by Article 44.2 of the ICN. Herein, it is validated. This species is the most common symbiont in reef corals in the southern Persian/Arabian Gulf, the world's hottest body of water sustaining reef coral growth.     

Effects of solar and artificial radiation on motility and pigmentation in Cyanophora paradoxa

The effects of solar radiation and artificial UV irradiation on motility and pigmentation were studied in the flagellate system Cyanophora paradoxa. Both percentage of motile cells and average velocity decreased drastically after a solar exposure of a few hours. This effect was not due to an overheating since the cells were exposed under temperaturecontrolled conditions. Partial reduction of the UV-B radiation by cut-off filters or by insertion of an artificial ozone layer increased the tolerated exposure times. Artificial UV radiation also induced the same effects. Under both solar and artificial UV irradiation the photosynthetic pigments within the cyanelles were bleached also within short exposure times. Kinetics of pigment destruction showed that the accessory phycobilins are lost with a half life of 1.3 h while the chlorophylls had a half life of 33 h and a carotenoid with an absorption maximum at 480 nm of 17.3 h.     

Mechanismen der pathologischen Pigmentbleichung bei Pflanzen

Viele pathologische Pigmentbleichungen sind oxidative Prozesse. In einer Reihe von Simulationsversuchen und Modellreaktionen wurden die Grundbedingungen für die Auslösung dieser Prozesse studiert und mit ?in vivo” Meßdaten verglichen. Bei den verwendeten oxidativen Bedingungen, unter denen Pigmente gebleicht werden, handelt es sich um chemische, enzymkatalysierte und lichtabhängige Oxidationen, wobei der Singulettsauerstoff, neben weiteren reaktiven Sauerstoffspezies eine herausragende Rolle spielt. Ausgelöst werden solche Pigmentbleichungen unabhängig davon, ob der ?aktivierte Sauerstoff” außerhalb oder innerhalb der Thylakoidmembranen erzeugt wird, wobei jedoch die zugrunde liegenden Mechanismen unterschiedlich sind. Parallel zur Pigmentbleichung wird grundsätzlich eine Oxidation von Lipiden gemessen; wird primär eine Lipidperoxidation induziert, so ist die Pigmentbleichung als Kooxidation von Lipiden zu sehen. Mit Hilfe der empfindlichen HPLC-Technik wurden Kinetiken der Bleichraten von Chlorophyll a, Chlorophyll b, β-Karotin, Neoxanthin, Violaxanthin und Lutein gemessen. Die schnellsten Bleichungsraten werden unter Bedingungen erzielt, die einen stark limitierten Elektronenfluß hervorrufen. Die erzielten Ergebnisse erlauben den Vergleich mit ?in vivo” Beobachtungen. Es können Rückschlüsse über die basalen Mechanismen der virus- bzw. pilzbedingten Vergilbung von Zuckerrüben sowie der Vergilbung von Fichtennadeln gezogen werden.     

The effect of glycerol on the Chlorella symbiosis in Hydra viridis

In green hydra strains that are bleached by glycerol, photosynthesis is arrested in both intact hydra and freshly extracted algae whereas photosynthesis is not affected by glycerol in resistant hydra strains and their algae. Glycerol sensitivity is an inherent property of the algae and sensitivity can be transferred to resistant aposymbiotic hydra by infecting them with sensitive algae. It is suggested that the host hydra recognizes glycerol induced changes, other than photosynthetic incompetance, in the algae and either ejects or digests them.Australian Institute of Marine Science, P.M.B. No. 3, Townsville M.S.O. 4810 Australia     

Modulation of polymorphonuclear leukocyte locomotion by synthetic amphiphiles

The capacity of synthetic amphiphiles, poly(ethyleneglycol) 6000 (PEG) esterified with saturated fatty acids (C₂–C₁₈), to modify polymorphonuclear leukocyte (PMNL) locomotion has been investigated. It was noticed that PEG-myristate (M-PEG; C₁₄) stimulated the random locomotion of PMNL populations in concentrations up to about 1 g/L. The esters with shorter aliphatic chains had negligible effects, whereas those with longer chains, PEG-palmitate (P-PEG; C₁₆) and PEG-stearate (S-PEG; C₁₈) reduced the locomotion, irrespectively of concentration. The ability of the PMNL to be stimulated by an attractant liberated from normal human serum was slightly impaired by M-PEG, but not by P-PEG. The response to M-PEG of individual PMNL was heterogeneous in that some cells were stimulated and others were inhibited. However, the average result was a reduction of the motility. This indicates that methods used for the study of the locomotion of cell populations may not always reflect the average behavior of the whole population. It was also concluded that the different effects of M-PEG and P-PEG owed to dissimilar effects on the membrane structure of the PMNL since (1) M-PEG perturbated the PMNL membrane more than P-PEG, as assayed by the release of superoxide anion (0 ₂ ⁻ , although the binding was smaller, and (2) M-PEG and P-PEG increased and decreased the membrane fluidity, respectively, as measured with fluorescent bleaching and recovery after bleaching of labeled PMNL. The results indicate a subtle coupling between membrane structure and PMNL locomotion.     

Growth and photosynthetic activities of wild-type and antenna-deficient mutant strains of Rhodobacter capsulatus

Cells of Rhodobacter capsulatus wild-type strains (37b4, B 10) and mutant strains, lacking lightharvesting (LH) complex II (B800–850) and defective in formation of LH I (B870) complex [U 43 (pTXB 87), U43 (pTXA6-10)] were grown photosynthetically at high and low light intensities in a turbidostate. The mutant strain U43 (pTXA6-10), lacking any LH system, was able to grow at high and low light intensities with doubling times of 4.6 and 9.8 h, respectively. In this mutant the concentration of photochemical reaction centers (RC) per cell and per membrane protein was several times higher than in wild type cells, but the bacteriochlorophyll content, the size of the photosynthetic unit and the rate of photophosphorylation were lower than in wild type cells. Reversible bleaching of reaction center and photophosphorylation were measured under different excitation light intensities. The charge recombination in the RC between the primary donor and Q_B was very slow in the mutant strains. Two membrane fractions differing in absorption spectra and light saturation behaviour of reversible bleaching and photophosphorylation were isolated from the mutant strains. The experimental data indicate that photosynthetic units of different composition and/or organization are present in the mutant cells.Abbreviations DSM Deutsche Sammlung von Mikroorganismen, Braunschweig     

山茱萸果核抗氧作用研究

用胡萝卜素漂白法初步探查到山茱萸果核的抗氧活性后,接着用烘箱试验法进一步证明它的水提物和甲醇提取物对市售豆油猪油也呈现明显抗氧作用,说明它有实际应用价值,从核甲醇提取物中分离鉴定了没食子酸及其中酯两种抗氧活性成分。     

Coral bleaching patterns are the outcome of complex biological and environmental networking

Continued declines in coral reef health over the past three decades have been punctuated by severe mass coral bleaching‐induced mortality events that have grown in intensity and frequency under climate change. Intensive global research efforts have therefore persistently focused on bleaching phenomena to understand where corals bleach, when and why—resulting in a large—yet still somewhat patchy—knowledge base. Particularly catastrophic bleaching‐induced coral mortality events in the past 5 years have catalyzed calls for a more diverse set of reef management tools, extending far beyond climate mitigation and reef protection, to also include more aggressive interventions. However, the effectiveness of these various tools now rests on rapidly assimilating our knowledge base of coral bleaching into more integrated frameworks. Here, we consider how the past three decades of intensive coral bleaching research has established the basis for complex biological and environmental networks, which together regulate outcomes of bleaching severity. We discuss how we now have enough scaffold for conceptual biological and environmental frameworks underpinning bleaching susceptibility, but that new tools are urgently required to translate this to an operational system informing—and testing—bleaching outcomes. Specifically, adopting network models that can fully describe and predict metabolic functioning of coral holobionts, and how this functioning is regulated by complex doses and interactions among environmental factors. Identifying knowledge gaps limiting operation of such models is the logical step to immediately guide and prioritize future experiments and observations. We are at a time‐critical point where we can implement new capacity to resolve how coral bleaching patterns emerge from complex biological–environmental networks, and so more effectively inform rapidly evolving ecological management and social adaptation frameworks aimed at securing the future of coral reefs.