Use of Remote Sensing to Monitor the Health of Coral Reef Systems

Remote sensing can be utilized in order to give succinct information regarding the arrangement and the constituents of coral reef materials. The biological and physical attributes of the water bodies in which the coral reefs exist are monitored over a period of time and the changes note. This paper explores the different technologies available in the field of remote sensing. Over time, there has been a large improvement as the access to remotely sensed data is concerned. This turn of events mainly fueled by the advancements in the field of Information Technology has resulted in better, improved and more accurate and faster information extraction techniques. This has been accelerated by the fact that governments and institutions have heavily invested in improved technology that has enabled faster results and dissemination of the data obtained over the internet. This paper provides a complete and detailed approach as to the various methods that are used in the field of remote sensing, as the study of coral reefs is concerned. The adverse climatic changes that result due to global; warming have caused massive damages to coral reefs across the globe. It has therefore become necessary to exploit the latest technology in an effort to conserve the remaining coral reef deposits.

Introduction

The coastal regions, the points where the sea waters come into contact with the mainland are places of unique value and importance indeed. They make a very considerable part of the global landscape and are habitats to a very diverse range of ecosystems such as coral reefs, sea grass, mangroves etc.They indeed are important in many ways. There are several significances attached to the existence of the coastal features. The coastal regions provide perfect locations for ports and beautiful harbor which possess great economic value. The coastal features also attract tourism to several regions and provide beautiful spots for the construction of luxurious apartment and villas. The existence of freshwater and salt water in the numerous coastal estuaries provides some of the best places to live on earth. Indeed coastal features are of great economic value to the coastal nations.However, all this beauty and its associated economic value could soon be over if the coastal environment is not properly managed. The continuing pollution in the coastal belts greatly reduce the total production of fish in these regions and also results in massive degradation of the coastal scenery destruction and other valuable resources associated with the coastal wetlands (Pandolfi et al., 2003). It is worth noting that the coastal landscape feature is also act as shield against the very destructive nature of large waves and tsunamis. The storm protection that is provided by the coastal landforms could also be soon lost and this would result in the exposure of the mainland to the massive destruction cased by the sea waves. Such destruction could include losses of life, destruction of property and erosion. In case the coastal mangrove forests are destroyed and the coral reefs are killed, the result would be unimaginable as the storm protection and the economic importances that are associated with the coastal features would be lost. It therefore calls for proper and systematic real time management of the coastal features. This is to ensure that their productivity and growth are maintained for now and the future generations and environmental stability. It is therefore important for the coastal nations across the globe to devise and implement proper ecosystem management in order to realize the sustainable utilization, protection and development of the coastal landforms

In order to succeed in the conservation and preservation processes, it is important to understand the variables and processes that affect the coastal environments and the myriad ways in which they correlate. It is of utmost importance to adopt a holistic approach or a step-by-step one on this process of solving the coastal bottle-necks. It is worth noting the understanding of the processes and the outcome of the interaction in the coastal environment setting is a complex one. A careful, thorough, systematic assessment is therefore mandatory for accuracy to be achieved. Proper understanding of the variables affecting the coastal environment and the coastal landscape is of utmost importance as the management of the coastal ecosystem is concerned. Accuracy can therefore be obtained through the use of proper audit of the data collection and processing techniques.The set of data collected should be handled with accuracy and care.The utilization of remote sensing technology has of late proven to be the best means of providing the information need for the proper management of resources such as the coastal coral reefs. This is because they provide monitoring capabilities.Ther use of and application of Geographical Information System also helps in the trend analysis and forecast of future scenarios. Thus GIS forms a major element of decision making as the conservation and management of coastal features are concerned.

Remote Sensing Technology

The application of remote sensing technique of coming up with useful information about items on the surface of the earth without the actual physical need of contact is indeed a great milestone.

The processes that are involved in this procedure rely mainly o sensors that are fitted with transducers and signal processors. The sensors that are employed in the operation include and are not limited to the following: scanners, cameras, radar, radiometers etc.These sensors are erected on platforms such as satellites and aero planes all of which are at a certain great distance from the surface of the earth..The sensors record their findings onto storage media such as photo.The principle of operation of the earlier recording media such as the magnetic tapes is that when electromagnetic waves fall onto certain surfaces, various forms of absorption, transmission and reflection of the radiation takes place. There is a portion that is reflected, some of the radiation is transmitted through the receiving surface. All surfaces also emit varying degrees of radiation. It is this emitted radiation that is often recorded by the sensors. The intensity if the radiation together with its wavelength are both functions of the surface under study. Each surface therefore possesses a unique spectral signature. There is specialized equipment that is utilized distinguishing the various spectral signatures. The existence of such equipment makes it possible to isolate and identify to a high degree the different spectral signatures and their possible sources. Such a system also makes it very possible to map the surface limits and conditions using the remote sensing technology. It is for this reason that satellite remote sensing has now found its place in the management of several natural resources in various fields in the world. It has made it possible to monitor the activities that occur on the earths continental plates and shelves which harbor coral reefs, major and minor islands, mangrove forests and plankton rich waters that are evident in the various costal estuaries.

Satellites use in remote sensing

The satellites in use for the purpose of data collection in the mapping process can either be geostationary thereby making it possible to continuously record data from a given portion of the earth, moon or it can be synchronous in that it could be sensing information from all over the earth surface while being in continuous movement above the equator. Such is the system used by the Landsat satellites which has a repeat moment ranging in different length of time of between sixteen to eighteen days. The IRS however has a period of twenty two days. The satellites cover a constant area size continuously. The synchronous satellites that monitor the sun possess a synoptic coverage area. The evaluation of the ground area that is covered by the satellite can be evaluated by making a reference to the satellites row and path.

The devices that are used in the making of the observation are the sensors. They mainly consist of an intricate system of lenses and mechanisms which have filter coatings that aid in focusing on the area that is under observation. The detectors are placed on the planes of focus. The sensors possess the ability of sensitivity to certain parts of the field of observation. The sensors then produce output in accordance to the input signals that are fed into it. The output could be in analog or digital form.

Attributes used in remote sensing

Spatial resolution: This is measure of the least angular or directly linear distance between two separate objects that can be resolved distinctively by the sensor. The higher the resolution of the sensor, the higher the volume of data it can capture and the smaller the areas that it can cover. The resolution of a sensor and its area of coverage are the factors that determine their scale of imagery.

Temporal resolution: This refers to the number of times the sensor gets imagery of a given area under study. usually the sensor would take repeated data samples in order to outline the little differences that exists between them.

Spectral resolution: This refers to the magnitude and the interval of wavelengths on the electromagnetic spectrum that a sensor is sensitive enough to detect.

Radiometric sensitivity: This is the sensors ability to differentiate the reflectance or the remittance of the spectral radiation from various predetermined targets. This however depend s on the various quantum levels that exists within a certain spectral band.

Problems with remotely sensed information

The major problem with remotely sensed information is that the path that exists between the object under study and the sensor is never clear.Therefore, the process of trying to derive quantitative information becomes almost impossible since in this case the underwater habitats are completely submerged and covered with various objects and particles. There also exists variable levels of reflectance at various water bottom depths (Ahmad,1994).In order to take care of this anomaly, an algorithm for water column correction has been derived and is therefore employed in coming up with clearer images.The water column correction algorithm is however not adopted for areas with shallow water depths.

The application of GIS and remote sensing in the management of coral reef along the Caribbean

1. SeaWiFS's Global Shallow Bathymetry

The process of characterization of the depth of water in the oceans is an initial step towards improving the method of identifying and characterizing coral reefs.Scientists from NOAA has come up with a revolutionary new method that is an improvement of the earlier bathymetry algorithms. This method was originally used in the 4-Metre IKONOS imagery and can be utilized in the analysis of data from a variety of other sensors (Stumpf et al. 2003b).The algorithm is applied in the one kilometer bathymetry map obtained in the SeaWiFS data. Each pixel's value in the maximum resolution SeaWiFS depth classification technique is taken out of the distances that are worked out from different SeaWiFS flights in order for the cloud pixels to be eliminated. The very best results are obtained after the elimination of the various effects cause d by the following elements: chlorophyll and sediments. Median measurements are then used after being subjected to cloud pixel removal in order to come up with an appropriate representation on the map.

The introduction of the latest technology in the satellite design has resulted in the existence of powerful satellites such as IRS -- 1C, P4, P6 and, 1D.Thes satellites possess increased levels of spatial resolution of varying degrees of tolerances. For example The PAN has a . spatial resolution of 5.8m,LISS IV has spatial resolution of 5.8 m while WiFS and AWiFS have spatial resolution of 188m and 56 meters respectively. These satellites also have extended ranges and increased repetivity of up to 4 days of data.

The data obtained from PAN when used in conjunction with the data obtained from LISS-III and IV generates information of very high special detail regarding ecological activities. The information derived from the PAN and LISS three and LISS four give important information regarding coral reef zonation.These information are particularly accurate for atolls, coral pinnacles and patch coral reefs.

Problems with remotely sensed information

The major problem with remotely sensed information is that the path that exists between the object under study and the sensor is never clear.Therefore, the process of trying to derive quantitative information becomes almost impossible since in this case the underwater habitats are completely submerged and covered with various objects and particles. There also exists variable levels of reflectance at various water bottom depths (Ahmad,1994).

In order to take care of this anomaly, an algorithm for water column correction has been derived and is therefore employed in coming up with clearer images.The water column correction algorithm is however not adopted for areas with shallow water depths.

Fig1.A flow chart showing the processes involved in the study of ecosystem changes using satellite data