Reef Research Stations

Introduction

This module served as an introduction to Geographic Information Systems (GIS) whereby I acquired the skillset necessary to perform spatial analyses. I became familiar with the various geospatial tools offered through the ArcGIS Pro software, and applied these functions to publicly available spatial data archives to investigate marine biology related research questions.

Study Background

The aim of the following study is to examine the aerial extent of snorkeling to a coral reef habitat on 5 research stations located in Queensland, Australia and 1 research station located in the Philippines. All research stations are positioned next to coral reefs. These stations include Heron Island, Orpheus Island, Daydream Island, Lizard Island, Hamilton Island, and Pagasa Island.

Research Question: What is likely to be the best station to visit in terms of reef extent and class diversity?

Methods

Benthic maps associated with the study area (Heron Island, Orpheus Island, Daydream Island, Lizard Island, Hamilton Island, and Pagasa Island) were downloaded in a shape file format from publicly available spatial data archives via Allen Coral Atlas. This data was subsequently uploaded as a new data layer into ArcGISPro [version 3.1].
In order to differentiate the various substratum categories within the benthic map dataset, unique colours were assigned to each of the different benthic classes. This was done by navigating to the symbology panel -> unique values -> add all values.
Using both the world imagery layer and benthic dataset layer, a standard map was created and exported in JPEG format for two of the six research station sites: Heron Island and Pagasa Island. Following proper GIS standard practice, the finalised map layouts include the map body, title, legend, north arrow, scale bar, source, author, and date (Fig 1, 2).
A feature class was created for each research station by navigating to the gdb file in the contents panel -> new -> feature class -> create new feature class. 'ReefStations' was used as the name of the new feature class. The point location data of Heron Island Research Station and Pagasa Island Research station were utilised to define the feature class. The new field name was 'Site_Name.' This creates a point vector data file to store the research station location in.
To mark & digitise the location of the research stations on the map, the coordinate information was inserted into the 'Go to XY' function. Then, navigating to the 'edit' tab -> create -> create features -> 'Reefstations.' Using the crosshair cursor to left click on the marker point base, the digitsation was finalised.
An attribute table was opened for the 'Reefstations' map and the research station names were entered under the 'Site_Name' column.
The 'buffer' tool was used to examine the aerial extent of snorkeling to a coral reef around Heron and Pagasa Island Research Stations. The buffer distance was set to 1 kilometer, which is the general snorkeling distance of most tourists.
The 'clip' tool was utilised to subset the Allen Coral Atlas benthic cover map layer to my study sites. In the clip settings, benthic cover map was set as the input feature, and the research stations buffer layer was set as the clip features.
To extract the benthic cover class area within each of the research station buffer sites (1 km), the 'tabulate intersection' tool was used. The research stations buffer layer was set as the input zone features and the associated zone fields was set to 'Site_Name.' The input class features was set as the benthic cover map clip layer with class fields set to 'class' and sum fields set to 'Shape_Area.' Square meters were used as the output units.
The 'table to excel' tool was used to copy the tabulate intersection table to excel (Table 1, 2).

Results

Figure 1. Benthic Cover in a Coral Reef Adjacent to Heron Island within the general snorkeling distance of most tourists (1 km).

Figure 2. Benthic Cover in a Reef Adjacent to Pagasa Island within the general snorkeling distance of most tourists (1 km).

Conclusion

In regards to class diversity, the Pagasa Island research station is the best place to visit. In this location, tourists that snorkel within 1 kilometer of the research station will see five different classes including coral/algae, rock, rubble, sand, and seagrass (albeit there is only a 0.3% coverage of seagrass). In contrast, the reef adjacent to the Heron Island research station is composed of four classes including coral/algae, rock, rubble, and sand. Although Pagasa Island showcases greater class diversity, Heron Island has a larger coral reef extent. At Heron Island, coral/algae cover accounts for 15.1% of the total area surrounding the research station (within 1 km), compared to just 9.2% at Pagasa Island.

Workbook Questions

What is the smallest human-made object you can see? What is the largest human made-object you can see?

The smallest human-made object I can see is a shed (5.07 m). The area of the shed is 17.38 squared meters. The largest human-made object I can see is the dock (110.14 m). The area of the dock is 633.36 squared meters. In contrast, the area of the island is 234,087.90 squared meters. The area of the atoll is 34.42 squared kilometers.

What important information have you discovered? What is the source of the ‘World Imagery’ layer? What is the accuracy and resolution (pixel size) of the imagery over Heron island? When was the image captured?

I have discovered how to obtain the metadata for any particular point on my map. The source of the ‘World Imagery’ layer is ArcGIS Map Service whereby the service name is world_imagery. The accuracy and resolution (pixel size) of the imagery over Heron Island is resolution = 0.5M and accuracy = 5M. The image was captured on June 24, 2021.

How does vector data represent features? What type of vector data is the benthic cover map?

Vector data represents features as points, lines, and shapes. The benthic cover map is made up of polygons.

What information can you see in the attribute table?

In the attribute table, I can see the type of shape assigned for each feature class. In our case, all of the shapes are polygons. I can also view the FID and class value. The class values on the benthic map include rubble, rock, coral/algae, sand, seagrass, and microalgal mats.

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