scholarly journals Detecting 2020 Coral Bleaching Event in the Northwest Hainan Island Using CoralTemp SST and Sentinel-2B MSI Imagery

2021 ◽  
Vol 13 (23) ◽  
pp. 4948
Author(s):  
Bailu Liu ◽  
Lei Guan ◽  
Hong Chen
Keyword(s):  
Coral Bleaching ◽  
Large Scale ◽  
Global Climate ◽  
Hainan Island ◽  
Threshold Value ◽  
Bleaching Event ◽  
Wide Range ◽  
Coral Reef Ecosystems ◽  
The Difference ◽  
Difference Images

In recent years, coral reef ecosystems have been affected by global climate change and human factors, resulting in frequent coral bleaching events. A severe coral bleaching event occurred in the northwest of Hainan Island, South China Sea, in 2020. In this study, we used the CoralTemp sea surface temperature (SST) and Sentinel-2B imagery to detect the coral bleaching event. From 31 May to 3 October, the average SST of the study area was 31.01 °C, which is higher than the local bleaching warning threshold value of 30.33 °C. In the difference images of 26 July and 4 September, a wide range of coral bleaching was found. According to the temporal variation in single band reflectance, the development process of bleaching is consistent with the changes in coral bleaching thermal alerts. The results show that the thermal stress level is an effective parameter for early warning of large-scale coral bleaching. High-resolution difference images can be used to detect the extent of coral bleaching. The combination of the two methods can provide better support for coral protection and research.

scholarly journals Great Salt Lake–Effect Precipitation: Observed Frequency, Characteristics, and Associated Environmental Factors

2012 ◽  
Vol 27 (4) ◽  
pp. 954-971 ◽  
Author(s):  
Trevor I. Alcott ◽  
W. James Steenburgh ◽  
Neil F. Laird
Keyword(s):  
Environmental Factors ◽  
Temperature Difference ◽  
Large Scale ◽  
Salt Lake ◽  
Great Salt Lake ◽  
Threshold Value ◽  
Substantial Improvement ◽  
Lake Area ◽  
Lake Effect ◽  
The Difference

Abstract This climatology examines the environmental factors controlling the frequency, occurrence, and morphology of Great Salt Lake–effect (GSLE) precipitation events using cool season (16 September–15 May) Weather Surveillance Radar-1988 Doppler (WSR-88D) imagery, radiosonde soundings, and MesoWest surface observations from 1997/98 to 2009/10. During this period, the frequency of GSLE events features considerable interannual variability that is more strongly correlated to large-scale circulation changes than lake-area variations. Events are most frequent in fall and spring, with a minimum in January when the climatological lake surface temperature is lowest. Although forecasters commonly use a 16°C lake–700-hPa temperature difference (ΔT) as a threshold for GSLE occurrence, GSLE was found to occur in winter when ΔT was only 12.4°C. Conversely, GSLE is associated with much higher values of ΔT in the fall and spring. Therefore, a seasonally varying threshold based on a quadratic fit to the monthly minimum ΔT values during GSLE events is more appropriate than a single threshold value. A probabilistic forecast method based on the difference between ΔT and this seasonally varying threshold, 850–700-hPa relative humidity, and 700-hPa wind direction offers substantial improvement over existing methods, although forecast skill is diminished by temperature and moisture errors in operational models. An important consideration for forecasting because of their higher precipitation rates, banded features—with a horizontal aspect ratio of 6:1 or greater—dominate only 20% of the time that GSLE is occurring, while widespread, nonbanded precipitation is much more common. Banded periods are associated with stronger low-level winds and a larger lake–land temperature difference.

Large Scale TIDs climatology over Europe using HF Interferometry method

2020 ◽  
Author(s):  
Estefania Blanch ◽  
Antoni Segarra ◽  
David Altadill ◽  
Vadym Paznukhov ◽  
Jose Miguel Juan
Keyword(s):  
Solar Activity ◽  
Propagation Velocity ◽  
Large Scale ◽  
Large Data ◽  
Density Fluctuations ◽  
Night Time ◽  
Wide Range ◽  
Propagation Parameters ◽  
The Difference ◽  
Sporadic E

<p>Travelling Ionospheric Disturbances (TIDs) are ionospheric irregularities that occur as plasma density fluctuations that propagate as waves through the ionosphere over a wide range of velocities and frequencies. It has been demonstrated that Large Scale TIDs (LSTID) can be detected with several ionospheric sensors such as ionosondes and their main characteristics such as velocity, direction of propagation and amplitude can be inferred.</p><p>We have applied the recent developed HF Interferometry (HF-Int) method to detect the occurrence and main characteristics of LSTIDs over Europe for different solar activities (2014 – 2019) in order to perform a climatological analysis. HF-Int determines the dominant period of oscillation and the amplitude of the LSTIDs using spectral analysis, and estimates the propagation parameters of the LSTIDs from the measured time delays of the disturbance detected at different sensor sites.</p><p>The results show that larger diurnal and seasonal occurrence of LSTID happens near sunrise hours and night-time, especially during equinox. In the morning sector, prevailing velocity propagation is westward influenced by the solar terminator effect and it also depends on the season: during winter the dominant propagation velocity is north-westward and during summer is south-westward. In the evening and night sector, the prevailing propagation velocity is southward suggesting auroral origin of the disturbance. The higher activity at night-time might be the result that neutral winds favour equatorward propagation at night whereas at day might prevent to propagate to low latitudes.</p><p>Similar behaviour has been found for high and low solar activity with the difference that during summer at low solar activity, large occurrence of sporadic E layer happens during day time. Then, ionospheric data experience large data gaps at the F region because of screening of the Es (Es Blanketing effect). This results in a poor statistic under such a conditions for daytime summer low solar activity and the number of detected LSTID is lower.</p>

scholarly journals Fingerprints of the Anthropocene: the 2016 Coral Bleaching Event in an Equatorial Archipelago

2018 ◽  
Author(s):  
Abigail Moore ◽  
Samliok Ndobe ◽  
Jamaluddin Jompa
Keyword(s):  
Coral Reef ◽  
Coral Bleaching ◽  
Monitoring Network ◽  
Life Forms ◽  
Iucn Red List ◽  
Bleaching Event ◽  
Colour Scale ◽  
Coral Reef Ecosystems ◽  
The Caribbean ◽  
Central Sulawesi

Coral reef ecosystems worldwide are experiencing increasingly frequent episodes of temperature-related “coral bleaching”. The Banggai Archipelago in Central Sulawesi, Indonesia, has extensive coral reefs and is home to the endemic Banggai cardinalfish, Pterapogon kauderni, a species listed as Endangered in the IUCN red List. A rapid survey was undertaken at seven sites (1.2°S-2°S) in this archipelago, in response to the national call for action during the 2016 global bleaching event. The CoralWatch method (6 point colour scale: CW1-CW6) was used; colony life-form (Global Coral Reef Monitoring Network categories) and genus (Indo-Pacific Coral-finder) were recorded. Partial and full bleaching were observed at all sites; of 1166 colonies, 64.7% were fully bleached (CW1) or very pale (CW2); with 13.5% in CW4-CW6. Water temperatures were 1-3°C above recorded maxima from 2004-2012. Branching and encrusting life-forms had the highest full/severe bleaching rates. Common genera with above average bleaching rates included Stylophora, Seriatopora, Pocillopora, Isopora, Merulina, Galaxea, some forms of Acropora and Porites. Algal overgrowth was observed on both live (fully/partially) bleached and dead colonies. Densities of Diadema sp. urchins, a key simbiont of the Banggai cardinalfish, until recently the most abundant coral reef herbivore, were extremely low (orders of magnitude less than 2004 densities), with few adult individuals present at 5/7 sites. The Caribbean experience underlines the urgency of addressing the unregulated Diadema fishery which has developed in the Banggai Archipelago since around 2007. Rehabilitating populations of this key invertebrate herbivore would contribute to biodiversity conservation and reef resilience/recovery in this equatorial archipelago.

scholarly journals Simultaneous evolution of multiple dispersal components and kernel

2016 ◽  
Author(s):  
Sudipta Tung ◽  
Abhishek Mishra ◽  
P.M. Shreenidhi ◽  
Mohammed Aamir Sadiq ◽  
Sripad Joshi ◽  
...  
Keyword(s):  
Drosophila Melanogaster ◽  
Large Scale ◽  
Global Climate ◽  
Rapid Evolution ◽  
Field Studies ◽  
Disease Spread ◽  
Long Distance ◽  
Data Accessibility ◽  
The Difference ◽  
Dispersal Evolution

AbstractGlobal climate is changing rapidly and is accompanied by large-scale fragmentation and destruction of habitats. Since dispersal is the first line of defense for mobile organisms to cope with such adversities in their environment, it is important to understand the causes and consequences of evolution of dispersal. Although dispersal is a complex phenomenon involving multiple dispersal-traits like propensity (tendency to leave the natal patch) and ability (to travel long distances), the relationship between these traits is not always straight-forward, it is not clear whether these traits can evolve simultaneously or not, and how their interactions affect the overall dispersal profile. To investigate these issues, we subjected four large (N∼2500) outbred populations of Drosophila melanogaster to artificial selection for increased dispersal, in a setup that mimicked increasing habitat fragmentation over 33 generations. The propensity and ability of the selected populations were significantly greater than the non-selected controls and the difference persisted even in the absence of proximate drivers for dispersal. The dispersal kernel evolved to have significantly greater standard deviation and reduced values of skew and kurtosis, which ultimately translated into the evolution of a greater frequency of long-distance dispersers (LDDs). We also found that although sex-biased dispersal exists in Drosophila melanogaster, its expression can vary depending on which dispersal component is being measured and the environmental condition under which dispersal takes place. Interestingly though, there was no difference between the two sexes in terms of dispersal evolution. We discuss possible reasons for why some of our results do not agree with previous laboratory and field studies. The rapid evolution of multiple components of dispersal and the kernel, expressed even in the absence of stress, indicates that dispersal evolution cannot be ignored while investigating eco-evolutionary phenomena like speed of range expansion, disease spread, evolution of invasive species and destabilization of metapopulation dynamics.Data AccessibilityData will be deposited to dryad if accepted.

scholarly journals Land–Ocean Warming Contrast over a Wide Range of Climates: Convective Quasi-Equilibrium Theory and Idealized Simulations

2013 ◽  
Vol 26 (12) ◽  
pp. 4000-4016 ◽  
Author(s):  
Michael P. Byrne ◽  
Paul A. O’Gorman
Keyword(s):  
Land Surface ◽  
General Circulation ◽  
Large Scale ◽  
Circulation Model ◽  
Ocean Warming ◽  
Quasi Equilibrium ◽  
Wide Range ◽  
The Difference ◽  
Limited Moisture ◽  
Lapse Rates

Abstract Surface temperatures increase at a greater rate over land than ocean in simulations and observations of global warming. It has previously been proposed that this land–ocean warming contrast is related to different changes in lapse rates over land and ocean because of limited moisture availability over land. A simple theory of the land–ocean warming contrast is developed here in which lapse rates are determined by an assumption of convective quasi-equilibrium. The theory predicts that the difference between land and ocean temperatures increases monotonically as the climate warms or as the land becomes more arid. However, the ratio of differential warming over land and ocean varies nonmonotonically with temperature for constant relative humidities and reaches a maximum at roughly 290 K. The theory is applied to simulations with an idealized general circulation model in which the continental configuration and climate are varied systematically. The simulated warming contrast is confined to latitudes below 50° when climate is varied by changes in longwave optical thickness. The warming contrast depends on land aridity and is larger for zonal land bands than for continents with finite zonal extent. A land–ocean temperature contrast may be induced at higher latitudes by enforcing an arid land surface, but its magnitude is relatively small. The warming contrast is generally well described by the theory, although inclusion of a land–ocean albedo contrast causes the theory to overestimate the land temperatures. Extensions of the theory are discussed to include the effect of large-scale eddies on the extratropical thermal stratification and to account for warming contrasts in both surface air and surface skin temperatures.

MONITORING CORAL RECOVERY AT NEARSHORE CORAL REEFS IN PHANGNGA PROVINCE, THE ANDAMAN SEA FOLLOWING THE 2010 CORAL BLEACHING EVENT

2017 ◽  
Author(s):  
Makamas Sutthacheep ◽  
Makamas Sutthacheep ◽  
Thamasak Yeemin ◽  
Thamasak Yeemin ◽  
Sittiporn Pengsakun ◽  
...  
Keyword(s):  
Coral Reef ◽  
Coral Reefs ◽  
Coral Bleaching ◽  
Coral Cover ◽  
Global Climate ◽  
Andaman Sea ◽  
Live Coral ◽  
Bleaching Event ◽  
Sea Star ◽  
Coral Recovery

Mass bleaching and subsequent mortality of scleractinian corals in response to elevated seawater temperatures has been considered as one of the most impacts of global climate change. Three extensive coral bleaching events in the Andaman Sea were reported, in the years 1991, 1995 and 2010. Studies on survival of coral colonies, coral recruitment and community structure of coral reef associated macrofauna would predict the trends for coral recovery from the impacts of coral bleaching events. The present study aimed to examine the status of coral communities, density of coral recruits and coral reef associated macrofauna at nearshore coral reefs in Phangnga Province, the Andaman Sea following the 2010 coral bleaching event. The dead coral cover was high (>50%) while the live coral cover was in the range of 13-21%. There was high diversity of coral recruits on natural substrates. The average densities of macrobenthic fauna varied from 1.9 to 2.6 individuals.m-2, with significant differences among study sites. The dominant macrobenthic species were a soft coral (Lobophytum sp.), a sea star (Linckia laevigata) and a sea urchin (Echinostrephus molaris). Coral recovery at these coral reefs would be possible but local anthropogenic stressors must be overwhelmingly reduced in order to enhance coral reef resilience. The long-term monitoring programs in the Andaman Sea are required for decision makers to support their adaptive management approaches.

scholarly journals Remote sensing of submerged aquatic vegetation: an introduction and best practices review

2020 ◽  
Author(s):  
Gillian Rowan ◽  
Margaret Kalacska
Keyword(s):  
Remote Sensing ◽  
Best Practices ◽  
Large Scale ◽  
Submerged Aquatic Vegetation ◽  
Aquatic Vegetation ◽  
Global Climate ◽  
Underwater Environment ◽  
Sensor Platform ◽  
Wide Range ◽  
Optical Imagery

Submerged aquatic vegetation (SAV) is a critical component of aquatic ecosystems. It is however understudied and rapidly changing due to global climate change and anthropogenic disturbances. Remote sensing can provide the efficient, accurate and large-scale monitoring needed to ensure proper SAV management. Our objective is to introduce remote sensing to researchers in the field of aquatic ecology. Applying remote sensing to the underwater environment is more complex in comparison to terrestrial studies due to the water column. A wide range of sensors and platforms from remotely operated vehicles to satellites are available for use in the underwater environment, a sample of which being presented herein. The utility of any sensor/platform combination varies depending on the aquatic conditions being observed. An overview of the required corrections, processing, and analysis methods for passive optical imagery is presented and discussed. Previous applications of remote sensing to identify and detecting SAV are briefly presented and notable results and lessons are discussed.

scholarly journals Shifting Baselines: Physiological legacies contribute to the response of reef coral to frequent heat waves

2020 ◽  
Author(s):  
Christopher B. Wall ◽  
Contessa A. Ricci ◽  
Alexandra D. Wen ◽  
Bren E. Ledbetter ◽  
Delania E. Klinger ◽  
...  
Keyword(s):  
Environmental History ◽  
Heat Waves ◽  
Global Climate ◽  
Abiotic Factors ◽  
Reef Coral ◽  
List Type ◽  
Bleaching Event ◽  
Reef Corals ◽  
Legacy Effect ◽  
Coral Reef Ecosystems

AbstractGlobal climate change is altering coral reef ecosystems. Notably, marine heat waves are producing widespread coral bleaching events that are increasing in frequency, with projections for annual bleaching events on reefs worldwide by mid-century.The response of corals to elevated seawater temperatures can be modulated by abiotic factors at site of origin and dominant endosymbiont type, which can result in a shift in multiple coral traits and drive physiological legacy effects that influence the trajectory of reef corals under subsequent thermal stress events. It is critical, therefore, to evaluate the potential for shifting physiological and cellular baselines driven by these factors in in situ bleaching (and recovery) events. Here, we use the back-to-back regional bleaching events of 2014 and 2015 in the Hawaiian Islands and subsequent recovery periods to test the hypothesis that coral multivariate trait space (here termed physiotype, sensu (Van Straalen, 2003) shift in multiple bleaching events, modulated by both environmental histories and symbiotic partnerships (Symbiodiniaceae).Despite fewer degree heating weeks in the first-bleaching event relative to the second (7 vs. 10), bleaching severity in a dominant reef building coral on Hawaiian reefs, Montipora capitata, was greater (~70% vs. 50% bleached cover) and differences due to environmental history (reef site) were more pronounced. Melanin, an immune cytotoxic response, provided an initial defense during the first event, potentially priming antioxidant activity, which peaked in the second-bleaching event (i.e., a legacy effect). While magnitude of bleaching differed, immune response patterns were shared among corals harboring heat-sensitive and heat-tolerant Symbiodiniaceae. This supports a pattern of increased constitutive immunity in corals resulting from repeat bleaching events, with greater specialized enzymes (catalase, peroxidase, superoxide dismutase) and attenuated melanin synthesis.This study demonstrates bleaching events have implications for reef corals beyond shaping their ecological assemblages. These events can change the magnitude and/or identity of response variables contributing to physiotype, thus generating physiological legacies carried over into the future. Quantifying baseline coral physiotypes and tracking their shifts will be critical to understanding and forecasting the effects of increased bleaching frequency on coral biology and ecology in the Anthropocene.

MONITORING CORAL RECOVERY AT NEARSHORE CORAL REEFS IN PHANGNGA PROVINCE, THE ANDAMAN SEA FOLLOWING THE 2010 CORAL BLEACHING EVENT

2017 ◽  
Author(s):  
Makamas Sutthacheep ◽  
Makamas Sutthacheep ◽  
Thamasak Yeemin ◽  
Thamasak Yeemin ◽  
Sittiporn Pengsakun ◽  
...  
Keyword(s):  
Coral Reef ◽  
Coral Reefs ◽  
Coral Bleaching ◽  
Coral Cover ◽  
Global Climate ◽  
Andaman Sea ◽  
Live Coral ◽  
Bleaching Event ◽  
Sea Star ◽  
Coral Recovery

Mass bleaching and subsequent mortality of scleractinian corals in response to elevated seawater temperatures has been considered as one of the most impacts of global climate change. Three extensive coral bleaching events in the Andaman Sea were reported, in the years 1991, 1995 and 2010. Studies on survival of coral colonies, coral recruitment and community structure of coral reef associated macrofauna would predict the trends for coral recovery from the impacts of coral bleaching events. The present study aimed to examine the status of coral communities, density of coral recruits and coral reef associated macrofauna at nearshore coral reefs in Phangnga Province, the Andaman Sea following the 2010 coral bleaching event. The dead coral cover was high (>50%) while the live coral cover was in the range of 13-21%. There was high diversity of coral recruits on natural substrates. The average densities of macrobenthic fauna varied from 1.9 to 2.6 individuals.m-2, with significant differences among study sites. The dominant macrobenthic species were a soft coral (Lobophytum sp.), a sea star (Linckia laevigata) and a sea urchin (Echinostrephus molaris). Coral recovery at these coral reefs would be possible but local anthropogenic stressors must be overwhelmingly reduced in order to enhance coral reef resilience. The long-term monitoring programs in the Andaman Sea are required for decision makers to support their adaptive management approaches.

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