Facts About Remote Monitoring of Coral Reefs
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Facts About Remote Monitoring of Coral Reefs

This article goes into the different depts in which coral reefs use remote sening in their environment. This is very important aspect in corals because, it can lead to the advancement in monitering, conserving, and forecasting the health in coral reefs which is very important since corals are decreasing in numbers very drastically. Coral reefs usually span over a large geographic range and they host complex and diverse communities of species. Worldwide, coral reefs face threats such as coral bleaching, disease outbreaks, storms, and pollution inputs from land. Coral reef health is often monitored by teams of scuba divers; however this approach is time-consuming and expensive. Divers are limited in the distance they can cover and the frequency of their observations. Some reefs are not accessible to divers at all. An alternative approach to monitoring reef health is the use of satellites to gather images of coral reefs: this approach is called remote sensing. Satellites are commonly used to observe ecosystems on land. For example, satellite images are used to determine the time and location of illegal deforestation in rainforests. The benefits of remote sensing on land, to acquire big-picture views, fine-scale details, and repeated measurements through time, have inspired scientists to investigate whether remote sensing can be applied to more secluded environments such as coral reefs. The barrier of water provides plenty of challenges to the widespread use of satellite sensors in ocean observation. Water has unique spectral properties: compared to air, water reflects more of the shorter wavelengths of light and absorbs more of the longer wavelengths. This makes it a challenge to determine which satellite to use, and at what resolution. The accuracy in the resulting images must also be carefully tested. Remote sensing of coral reefs is also difficult because reef habitats themselves have many features that interfere with satellite imagery: windy conditions contribute to rough seas, there is often increased cloud cover in tropical reef environments due to high evaporation, and reefs with high sediment density can appear brighter than water in satellite images. In addition, each reef system is unique in its combination of coral composition, depth profiles, algal concentration, and bottom substrate. The variation between each reef system makes it difficult to identify the single, unique spectral signature for a type of object underwater, similar to what has been done for objects on land. In addition, there is a human challenge: individual scientists have different interests in the ecological properties of a coral reef. They may disagree about which properties are most important to monitor. Scientists could use remote sensing to identify and locate different reef species (such as branching Acropora species compared to encrusting corals like Montastraea), to monitor bleaching events, to record the total cover of live corals versus dead corals, to distinguish between algal dominated and coral-dominated reefs, or to identify specific geological formations. Different satellite capabilities might be needed for each type of study. Satellite imagery of coral reefs will be most useful when used in combination with other kinds of data: For example, coral reef health may not be easy to measure with satellite imagery, but it can be indirectly understood by collecting additional environmental information and studying how corals respond to different combinations of environmental factors. Satellite data could also be combined with ecological modeling to predict the future locations of healthy coral populations. Coral bleaching is a phenomenon that is particularly important to monitor over short timescales; this may be a phenomenon that is particularly suitable for satellite monitoring. A coral bleaching event creates a distinct spectral signature in a coral reef ecosystem. Completely bleached corals reflect the most light because of their bright white color. Using remote sensing to observe bleaching events would allow these changes to be recorded with high frequency through time and with high accuracy. Satellite monitoring would also eliminate the need for diver surveys, which can be biased by the fact that individual divers’ may score the degree of paleness with slight differences. Determining spectral signatures from one bleaching event could be used to determine the severity of future bleaching events on the same reef. Despite many challenges, the technology for remote monitoring of reef systems has come a long way since the launch of the first Landsat satellite in 1972 (Campbell 2008). Recently, high resolution data, 10 meters or less, acquired from modern satellites has been collected and analyzed from for content and accuracy. The overall goal of coral reef remote sensing is to obtain high-resolution data about reefs on a worldwide scale that will provide accurate assessment of the reef state. Remote sensing would be particularly beneficial for monitoring coral reef degradation because of its ability to obtain wide-scale views and at closely-spaced intervals. Using satellites to monitor coral reef communities has many obstacles still to overcome. However, the remote sensing field is rapidly advancing. Scientists continue to launch newer satellites designed specifically to capture images below the water’s surface, with increasing accuracy and at increasing depths. In addition, scientists continue to research ways to combine satellite imagery with ecological models. At present, this technique still requires calibration with diver-collected information. As the resolution of satellite imagery improves in time, space, and across the light spectrum, remote sensing will become increasingly useful for monitoring, protecting, conserving, and forecasting the health of coral reef ecosystems.

Coral reefs usually span over a large geographic range and they host complex and diverse communities of species.  Worldwide, coral reefs face threats such as coral bleaching, disease outbreaks, storms, and pollution inputs from land. Coral reef health is often monitored by teams of scuba divers; however this approach is time-consuming and expensive. Divers are limited in the distance they can cover and the frequency of their observations. Some reefs are not accessible to divers at all. An alternative approach to monitoring reef health is the use of satellites to gather images of coral reefs: this approach is called remote sensing. Satellites are commonly used to observe ecosystems on land. For example, satellite images are used to determine the time and location of illegal deforestation in rainforests. The benefits of remote sensing on land, to acquire big-picture views, fine-scale details, and repeated measurements through time, have inspired scientists to investigate whether remote sensing can be applied to more secluded environments such as coral reefs.

The barrier of water provides plenty of challenges to the widespread use of satellite sensors in ocean observation.  Water has unique spectral properties: compared to air, water reflects more of the shorter wavelengths of light and absorbs more of the longer wavelengths. This makes it a challenge to determine which satellite to use, and at what resolution. The accuracy in the resulting images must also be carefully tested. 

Remote sensing of coral reefs is also difficult because reef habitats themselves have many features that interfere with satellite imagery: windy conditions contribute to rough seas, there is often increased cloud cover in tropical reef environments due to high evaporation, and reefs with high sediment density can appear brighter than water in satellite images. In addition, each reef system is unique in its combination of coral composition, depth profiles, algal concentration, and bottom substrate. The variation between each reef system makes it difficult to identify the single, unique spectral signature for a type of object underwater, similar to what has been done for objects on land.

In addition, there is a human challenge: individual scientists have different interests in the ecological properties of a coral reef.  They may disagree about which properties are most important to monitor. Scientists could use remote sensing to identify and locate different reef species (such as branching Acropora species compared to encrusting corals like Montastraea), to monitor bleaching events, to record the total cover of live corals versus dead corals, to distinguish between algal dominated and coral-dominated reefs, or to identify specific geological formations. Different satellite capabilities might be needed for each type of study.

Satellite imagery of coral reefs will be most useful when used in combination with other kinds of data: For example, coral reef health may not be easy to measure with satellite imagery, but it can be indirectly understood by collecting additional environmental information and studying how corals respond to different combinations of environmental factors.  Satellite data could also be combined with ecological modeling to predict the future locations of healthy coral populations.

Coral bleaching is a phenomenon that is particularly important to monitor over short timescales; this may be a phenomenon that is particularly suitable for satellite monitoring. A coral bleaching event creates a distinct spectral signature in a coral reef ecosystem.  Completely bleached corals reflect the most light because of their bright white color. Using remote sensing to observe bleaching events would allow these changes to be recorded with high frequency through time and with high accuracy. Satellite monitoring would also eliminate the need for diver surveys, which can be biased by the fact that individual divers’ may score the degree of paleness with slight differences. Determining spectral signatures from one bleaching event could be used to determine the severity of future bleaching events on the same reef. 

Despite many challenges, the technology for remote monitoring of reef systems has come a long way since the launch of the first Landsat satellite in 1972 (Campbell 2008). Recently, high resolution data, 10 meters or less, acquired from modern satellites has been collected and analyzed from for content and accuracy. The overall goal of coral reef remote sensing is to obtain high-resolution data about reefs on a worldwide scale that will provide accurate assessment of the reef state. Remote sensing would be particularly beneficial for monitoring coral reef degradation because of its ability to obtain wide-scale views and at closely-spaced intervals.

Using satellites to monitor coral reef communities has many obstacles still to overcome.   However, the remote sensing field is rapidly advancing.  Scientists continue to launch newer satellites designed specifically to capture images below the water’s surface, with increasing accuracy and at increasing depths. In addition, scientists continue to research ways to combine satellite imagery with ecological models.  At present, this technique still requires calibration with diver-collected information. As the resolution of satellite imagery improves in time, space, and across the light spectrum, remote sensing will become increasingly useful for monitoring, protecting, conserving, and forecasting the health of coral reef ecosystems.

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Comments (1)

I hope you have a nice day! Very good article, well written and very thought out. I am looking forward to reading more of your posts in the future. singapore budget hotels

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