Changes in quantum efficiency of Photosystem II of symbiotic dinoflagellates of corals after heat stress, and of bleached corals sampled after the 1998 Great Barrier Reef mass bleaching event

2000 ◽  
Vol 51 (1) ◽  
pp. 63 ◽  
Author(s):  
Ross J. Jones ◽  
Selina Ward ◽  
Affendi Yang Amri ◽  
Ove Hoegh-Guldberg
Keyword(s):  
Heat Stress ◽  
Coral Bleaching ◽  
Seawater Temperature ◽  
Recovery Period ◽  
Pulse Amplitude ◽  
Bleaching Event ◽  
Algal Density ◽  
Symbiotic Algae ◽  
Temperate Coral ◽  
Symbiotic Dinoflagellates

Pulse–amplitude–modulation chlorophyll fluorometry was used to examine changes in dark-adapted Fv/Fm of endosymbiotic dinoflagellate microalgae within the tissues of the temperate coral Plesiastrea versipora exposed to elevated seawater temperature. The Fv/Fm was markedly reduced following exposure of corals to 28°C for 48 h. When corals were returned to ambient (24°C) conditions, Fv/Fm increased in an initial rapid and then secondary slower phase. Tissue discolouration (coral bleaching), caused by a significant decrease in the density of algae, was observed during the first 2–3 days of the recovery period. After 14 days, Fv/Fm was still significantly lower than in control corals. The recovery of Fv/Fm is discussed in terms of repair processes within the symbiotic algae, division of healthy algae and also the selective removal of photo-damaged dinoflagellates. Under field conditions, bleached corals sampled at Heron Island Reef during a bleaching event had significantly lower Fv/Fm than non-bleached colonies; four months after the bleaching event, there were no differences in F v /F m or algal density in corals marked as having bleached or having shown no signs of colour loss. The results of this laboratory and field study are consistent with the hypothesis that an impairment of photosynthesis occurs during heat-stress, and is the underlying cause of coral bleaching.

scholarly journals Loss of symbiont infectivity following thermal stress can be a factor limiting recovery from bleaching in cnidarians

2020 ◽  
Vol 14 (12) ◽  
pp. 3149-3152 ◽  
Author(s):  
Mariko Kishimoto ◽  
Andrew H. Baird ◽  
Shinichiro Maruyama ◽  
Jun Minagawa ◽  
Shunichi Takahashi
Keyword(s):  
Heat Stress ◽  
Seawater Temperature ◽  
External Environment ◽  
Host Cells ◽  
Coral Mortality ◽  
Free Living ◽  
Experimental Conditions ◽  
Symbiotic Algae ◽  
The Family ◽  
In The Wild

Abstract Increases in seawater temperature can cause coral bleaching through loss of symbiotic algae (dinoflagellates of the family Symbiodiniaceae). Corals can recover from bleaching by recruiting algae into host cells from the residual symbiont population or from the external environment. However, the high coral mortality that often follows mass-bleaching events suggests that recovery is often limited in the wild. Here, we examine the effect of pre-exposure to heat stress on the capacity of symbiotic algae to infect cnidarian hosts using the Aiptasia (sea-anemone)-Symbiodiniaceae model system. We found that the symbiont strain Breviolum sp. CS-164 (ITS2 type B1), both free-living and in symbiosis, loses the capacity to infect the host following exposure to heat stress. This loss of infectivity is reversible, however, a longer exposure to heat stress increases the time taken for reversal. Under the same experimental conditions, the loss of infectivity was not observed in another strain Breviolum psygmophilum CCMP2459 (ITS2 type B2). Our results suggest that recovery from bleaching can be limited by the loss of symbiont infectivity following exposure to heat stress.

scholarly journals Bleaching and post-bleaching mortality of Acropora corals on a heat-susceptible reef in 2016

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e8138 ◽  
Author(s):  
Kazuhiko Sakai ◽  
Tanya Singh ◽  
Akira Iguchi
Keyword(s):  
Heat Stress ◽  
Coral Bleaching ◽  
Reef Flat ◽  
Spatial Scales ◽  
Seawater Temperature ◽  
Partial Mortality ◽  
Large Spatial Scale ◽  
Scale Temperature ◽  
Morphological Differences ◽  
The Impact

In 2016, global temperatures were the highest on record, and mass coral bleaching occurred world-wide. However, around Sesoko Island, Okinawa, southwestern Japan, the heat stress assessed by degree heating week (DHW) based on local temperature measurements was moderate in 2016; in 1998, DHW was three times higher than in 2016 (10.6 vs. 3.3 in September in respective years). On a reef flat of Sesoko Island where the effect of severe coral bleaching on coral assemblage was monitored in 1998, significant coral bleaching occurred in 2016. Bleaching of the heat stress sensitive Acropora corals began in July 2016 on the reef flat as seawater temperature rose. We observed the bleaching and post-bleaching mortality status of individual colonies of Acropora spp. in 2016 in fixed plots on the reef flat. In total, 123 Acropora colonies were followed for six months after seawater temperature became normal by multiple surveys. At the beginning of September 2016, 99.2% of colonies, were either completely (92.7%) or partially (6.5%) bleached. Of those, the dominant species or species groups were A. gemmifera (Ag), A. digitifera (Ad), and tabular Acropora (tA). For all Acropora colonies, the overall whole and partial mortality was 41.5% and 11.4%, respectively. Whole mortality rate differed significantly among species; 72.5%, 17.9%, and 27.8% in Ag, Ad, and tA, respectively. Mortality rates at the end of the surveys were similar in smaller (≤10 cm in diameter) and larger Ag, but the former suffered mortality earlier than the latter. Higher survival of smaller colonies was observed only in tA (100%), which may be associated with large morphological differences between smaller and larger colonies. Some of the dominant Acropora colonies had survived without partial mortality including 15.0% survival of the most vulnerable Ag at the end of the surveys. These results suggest that moderate heat stress may have a potential for selecting heat-tolerant genotypes. A longer period of mortality lasting for six months, was observed in Ag in addition to immediate whole mortality after bleaching, due to the continuous loss of living tissue by partial mortality. This highlights the need for multiple surveys at least during several months to accurately assess the impact of thermal stress event to corals. In contrast to DHW based on local measurements, DHW obtained from satellite data were similar between 1998 and 2016. Although satellite-based measurement of sea surface temperature is very useful to reveal variations in heat stress at a large spatial scale, temperature should be measured on site when variations at smaller spatial scales are of interest.

scholarly journals Reef location has a greater impact than coral bleaching severity on the microbiome of Pocillopora acuta

Coral Reefs ◽  
2021 ◽  
Author(s):  
Emmanuelle S. Botté ◽  
Neal E. Cantin ◽  
Véronique J. L. Mocellin ◽  
Paul A. O’Brien ◽  
Melissa M. Rocker ◽  
...  
Keyword(s):  
Heat Stress ◽  
Microbial Communities ◽  
Coral Bleaching ◽  
Health Indicators ◽  
Amplicon Sequencing ◽  
Coral Community ◽  
16S Rrna Genes ◽  
Rrna Genes ◽  
Bleaching Event ◽  
The Impact

AbstractCoral reefs are increasingly threatened by heat stress events leading to coral bleaching. In 2016, a mass bleaching event affected large parts of the Great Barrier Reef (GBR). Whilst bleaching severity and coral mortality are usually monitored throughout major bleaching events, other health indicators, such as changes in microbial partners, are rarely assessed. We examined the impact of the 2016 bleaching event on the composition of the microbial communities in the coral Pocillopora acuta at Havannah Island Pandora reef, separated by 12 km on the inshore central GBR. Corals experienced moderate heat stress (3.6 and 5.3 degree heating weeks), inducing major bleaching (30–60%) at the coral community level. Samples were partitioned according to Symbiodiniaceae densities into three bleaching severity categories (mild, moderate, and severe). Whilst Symbiodiniaceae densities were similar at both reef locations, sequencing of the Symbiodiniaceae ITS2 and prokaryotic 16S rRNA genes revealed that microbial communities were significantly different between reefs, but not according to bleaching severity. Symbiodiniaceae composition was dominated by the genus Cladocopium with low abundances of Durusdinium detected in moderately and severely bleached colonies at both sites, despite site-specific ITS2 profiles. Bacterial communities were dominated by Proteobacteria and were almost entirely lacking the common Pocilloporid associate Endozoicomonas regardless of bleaching severity. Strikingly, only 11.2% of the bacterial Amplicon Sequencing Variants (ASVs) were shared between sites. This reef specificity was driven by 165 ASVs, mainly from the family Rhodobacteraceae. Comparison with previous studies suggests that the moderate heat stress experienced on the central GBR in 2016 caused the near-complete absence of Endozoicomonas. Symbiodiniaceae and bacteria (particularly Rhodobacteraceae) can be vertically transmitted in P. acuta, and larval propagation can be spatially restricted for this brooding species. Our results demonstrate that, unlike bleaching severity, location-specific factors and species-specific life history traits might have been paramount in shaping the P. acuta microbiome.

scholarly journals Assessing population collapse of Drupella spp. (Mollusca: Gastropoda) 2 years after a coral bleaching event in the Republic of Maldives

Hydrobiologia ◽  
2021 ◽  
Author(s):  
L. Saponari ◽  
I. Dehnert ◽  
P. Galli ◽  
S. Montano
Keyword(s):  
Coral Bleaching ◽  
Prey Availability ◽  
Coral Cover ◽  
Environmental Data ◽  
High Plasticity ◽  
Bleaching Event ◽  
Coral Recovery ◽  
The Republic ◽  
The Impact ◽  
Line Intercept

AbstractCorallivory causes considerable damage to coral reefs and can exacerbate other disturbances. Among coral predators, Drupella spp. are considered as delayer of coral recovery in the Republic of Maldives, although little information is available on their ecology. Thus, we aimed to assess their population structure, feeding behaviour and spatial distribution around 2 years after a coral bleaching event in 2016. Biological and environmental data were collected using belt and line intercept transects in six shallow reefs in Maldives. The snails occurred in aggregations with a maximum of 62 individuals and exhibited a preference for branching corals. Yet, the gastropods showed a high plasticity in adapting feeding preferences to prey availability. Drupella spp. were homogenously distributed in the study area with an average of 9.04 ± 19.72 ind/200 m2. However, their occurrence was significantly different at the reef scale with the highest densities found in locations with higher coral cover. The impact of Drupella spp. appeared to be minimal with the population suffering from the loss of coral cover. We suggest that monitoring programs collect temporal- and spatial-scale data on non-outbreaking populations or non-aggregating populations to understand the dynamics of predation related to the co-occurrence of anthropogenic and natural impacts.

scholarly journals Extreme white colouration of frogfish Antennarius maculatus due to coral bleaching event

Coral Reefs ◽  
2016 ◽  
Vol 36 (1) ◽  
pp. 167-167 ◽  
Author(s):  
Gabriel Grimsditch ◽  
Ahmed Basheer ◽  
D. E. P. Bryant
Keyword(s):  
Coral Bleaching ◽  
Bleaching Event

Prior heat stress enhances survival of renal epithelial cells after ATP depletion

1996 ◽  
Vol 270 (6) ◽  
pp. F1057-F1065 ◽  
Author(s):  
Y. H. Wang ◽  
S. C. Borkan
Keyword(s):  
Heat Stress ◽  
Epithelial Cells ◽  
Recovery Period ◽  
Atp Depletion ◽  
Protective Effects ◽  
Atp Content ◽  
Renal Epithelial Cells ◽  
Opossum Kidney ◽  
Ok Cells

The 72-kDa heat stress protein (HSP-72) is an inducible cytoprotectant protein. Although transient renal ischemia in vivo induces HSP-72, it is not known whether prior heat stress protects renal epithelial cells from injury mediated by ATP depletion. To evaluate this hypothesis, opossum kidney (OK) cells were exposed to sodium cyanide and 2-deoxy-D-glucose in the absence of medium glucose, a maneuver that reduced cell ATP content to < 10% of the control value within 10 min and decreased cell survival. One day after 2 h of ATP depletion, OK cells previously exposed to heat stress (to induce accumulation of HSP-72) exhibited marked improvement in survival (a > 4-fold increase in total DNA), less uptake of vital dye, and less release of lactate dehydrogenase (LDH) than cells subjected to ATP depletion alone (23.0 +/- 1.6 vs. 34.1 +/- 1.2% of total LDH, respectively). Enhanced clonogenicity post-heat stress was completely prevented by cycloheximide and positively correlated with the steady-state content of HSP-72. In the recovery period after ATP depletion, cell ATP content, maximum mitochondrial ATP production rate, and total LDH activity were all significantly higher in cells with abundant HSP-72. Although the protective effects associated with heat stress are likely to be multifactoral, preserved cell metabolism and higher ATP content could enhance cellular repair processes after ATP depletion.

Elevated sea-water temperature and solar UV-B flux associated with two successive coral mass bleaching events in Tahiti

1995 ◽  
Vol 46 (8) ◽  
pp. 1153 ◽  
Author(s):  
JH Drollet ◽  
M Faucon ◽  
PMV Martin
Keyword(s):  
Water Temperature ◽  
Coral Bleaching ◽  
Sea Water ◽  
Bleaching Event ◽  
Chemical Parameters ◽  
Physico Chemical ◽  
Long Line ◽  
Solar Uv ◽  
Line Transects ◽  
A Minor

After a minor coral bleaching event in 1993, a more dramatic episode occurred in Tahiti from March to July 1994. Coral bleaching was recorded along four continuous 25-m-long line transects. Physico-chemical parameters of the sea water (temperature, salinity, dissolved oxygen and pH) were noted once a week, and solar UV-B flux was recorded daily before and during the bleaching episode. Results emphasized the importance of the taxonomic position of coral in susceptibility to bleaching. The evolution of bleaching through time was related to mean daily solar UV-B flux and sea-water temperature. Moreover, comparison of the 1993 and 1994 data suggested temperature and/or UV-B thresholds that may elicit minor or severe bleaching events.

289 Phytogenic Feed Additives as a Potential Strategy to Mitigate the Negative Effects of Heat Stress in Growing Heifers

2021 ◽  
Vol 99 (Supplement_3) ◽  
pp. 156-157
Author(s):  
Shelby M Ramirez ◽  
Janaka Wickramasinghe ◽  
Nadiia Stepanchenko ◽  
Maria Oconitrillo ◽  
Jayamuni Silva ◽  
...  
Keyword(s):  
Heat Stress ◽  
Fixed Effects ◽  
Recovery Period ◽  
Random Effect ◽  
Antioxidant Properties ◽  
Feed Additives ◽  
Feed Additive ◽  
Negative Effects ◽  
Humidity Index ◽  
Potential Strategy

Abstract Phytogenic feed additives that contain anti-inflammatory and antioxidant properties may have potential to reduce inflammation and oxidation observed during bouts of heat stress. The trial objective was to determine the effects of a phytogenic feed additive on markers of stress in heifers subjected to diurnal heat stress (dHS). Eighteen Holstein and four Jersey heifers (5–6 months of age; d1 BW=205±9 kg) were assigned to two dietary treatments (n = 11) based on breed and age; 1) a basal TMR diet (CTL), 2) CTL supplemented with 0.25 g/head/d of a proprietary blend of phytogenics (PFA; BIOMIN America, Inc., Overland Park, KS). Heifers were housed individually and fed their respective treatments for 14d prior to dHS (d-14-1), subjected dHS (d1-7), and followed through a recovery period (d8-11). Weights were collected at d1 (baseline), d7 (end of dHS), and d11 (end of recovery). The temperature set point was assigned at 33°C from 0900 to 2100 h and allowed to equilibrate with outside temperature during night (24°C) for a total of 7d dHS. Total DMI (tDMI) and DMI from 0900 to 2100 h (hsDMI) were recorded daily. Serum was collected at d1, 2, 7 and 11 to determine effect of treatment on markers of oxidation, inflammation, and stress. Treatment effects were analyzed using PROC MIXED in SAS with treatment and time as fixed effects and heifer as a random effect. Temperature humidity index during dHS was greater during the day (84.5) versus night (73.3). There were no treatment differences (P&gt;0.05) in d 0–11 on ADG, ADFI, or GF between treatments. However, PFA numerically increased hsDMI, reduced (P&lt; 0.05) haptoglobin and tended to reduce (P&lt; 0.10) lipopolysaccharide binding protein compared with CTL. Overall, dietary PFA may be a potential strategy to mitigate the stresses that heifers experience during dHS.

Sign in / Sign up

Export Citation Format

Share Document