**2. Remote sensing applications in marine ecosystems**

**Sea Surface temperature:** Most industries use seawater as cooling water. When the water used as a coolant returns to the natural environment at a higher temperature, temperature changes reduce oxygen and affect the marine ecosystem [9]. SST information is needed in remote sensing assessment for fisheries applications [10]. Satellite SST observations help to understand regional diversity and global climate change, and allow the visualization of a wide range of ocean zones. In 1981, SST satellite infrared observations began with the launch of the AVHRR sensor on the NOAA 7 satellite, so that there are now three decades of SST satellite data [11].

**Coral reef:** Coral reefs are formed by living coral polyps and calcareous algae that grow at sea levels between 77 and 86 degrees Fahrenheit with normal salinity. Coral reefs act as feeding, reproductive, breeding, and aquatic habitats for many oceanic organisms, so the density and distribution of corals alter the populations of fish and other organisms [12]. The advantages of remote sensing systems in this area are the ability to survey the area on a large scale, continuous monitoring and the ability to check the system ecosystem in remote areas without direct contact

#### *Application of Remote Sensing in Natural Sciences DOI: http://dx.doi.org/10.5772/intechopen.94468*

with it. Among these, optical Remote sensing systems including multispectral and hyperspectral sensors have been most used in this field [13, 14].

**Mangrove forest:** Mangrove forests are tropical and subtropical ecosystems that grow on the margins of two different environments, sea and land [15–17]. These forests play an essential role in ecology and are considered as carbon reserves [18–20]. Due to their location in the tropics, they are prone to hiding under clouds, so a reliable monitoring tool is essential to measure deforestation. Radar remote sensing has been shown to be useful in distinguishing mangrove cover from other ground cover due to its long wavelengths that can penetrate the cloud [21].

**Ocean Color:** The color of the ocean is a unique property for water. Mapping and understanding ocean color changes can help monitor water quality and identify natural and human contaminants (oil slicks and algae blooms) that are dangerous to aquaculture and even to humans [8]. Remote sensing optical data can detect targets such as suspended sediments, algal blooms, chlorophyll-A, and oil slicks at various scales [21]. In the next section, which is research-oriented, we want to examine the application of remote sensing in estimating the concentration of chlorophyll- a phytoplankton in coastal waters (**Figure 1**).
