In order keep the data clearly organized and accessible a relational database was created using Microsoft Access. The database objects, data elements and the relationships between the objects are visualized in Figure 4.12. All real world objects are represented in the flow diagram as separate boxes and in the actual database as a table. All database elements associated with an object are listed within the object box and are table columns in the actual database. The real world objects represented in the database are summarized in Table 4.8. The data elements associated with the data objects are described in Table 4.9.
Table 4.8 Description of each object in the comprehensive relational database for this study.
Object name Object description
Points The three points randomly scattered on each image by CPCe Point occupants The coral species, coral species cluster, other reef organism or
substrate type that lies under a point Images The photoquadrat images
Transects Combinations of sequential images at each reef site Sites Reef site (i.e. A1)
Coral Traits Scleractinian coral traits (i.e. calice width, growth rate)
I Intersecting object to manage ‘many to many’ relationship that occurs between point occupant and trait
II Intersecting object to manage ‘many to many’ relationship that occurs between point occupant and trait
Table 4.9 Description of each data element in the comprehensive relational database for this study.
Data element name Data element description
Point name The unique name assigned to each identification point scattered on the photoquadrat images by CPCe (i.e. A01_20091127123134_NBR_06.4.jpgA
Point code The unique code assigned in the CPCe code file to identify each coral species, coral species cluster, other reef organism, or substrate type (i.e. BT = brown turf algae)
Point type General substrate type (hard coral, soft coral, sponges, algae, other, substrate, unknown)
Genus code A code referring to the genera that coral species belongs to (i.e. Acropora)
CH 4: Field sampling
Data element name Data element description
Species cluster The coral species cluster that a coral species belongs to
in the case were a number of species are difficult to identify based on photos alone (i.e. Acropora bushy)
Weighting The weighting given to a coral species in a cluster that
determines its likelihood of being selected as representative of the cluster in the calculation of functional diversity metrics. The weighting is based on the commonality cited in Veron (2000) i.e. rare, uncommon, common
Trait name The name of a coral trait (i.e. branching: 2D dominant) Trait category The name of the category to which a trait can belong
(i.e. branching)
Trait description Description of a coral trait (i.e. 2 dimensional branching structure)
Trait publication reference The source of the trait data (i.e. Veron, 2000)
Image Name The unique name of a photoquadrat image (i.e.
A01_20091127123134_NBR_06.4)
Image depth The depth at which the photoquadrat image was taken
(i.e. 6.4 m)
Longitude Longitude for the location at which the image was taken
in decimal degrees (i.e. 43.26645)
Latitude Latitude for the location at which the image was taken
in decimal degrees (i.e. -21.873606)!
Transect ID name The name of a particular transect on a particular reef site (i.e. A1.T1)
Depth category The depth category to which an image or transect
belongs (i.e. 5-10 m).
Site code The site code for a reef site (i.e. A1)
Site name The name for a reef site (i.e. No Bad Reef)
Region name The name of the study region in which a reef site is found (i.e. Velondriake)
Geomorphology The geomorphology of a particular reef site: patch reef,
fringing reef, or spur and groove system
Reef type The reef type of a particular site (i.e. M.1; see Ch. 4)
Number of huts The number of Vezo fishing huts within a 10 km radius
of the reef site as counted from satellite images.
Distance to river The distance in km between a reef site and the nearest
river mouth as measured from satellite images.
Average annual SST The average annual sea surface temperature (SST) in Celsius for a reef site calculated using NOAA satellite images.
Fetch The distance in km seaward from the reef site to the
Figure 4.12 Overview of comprehensive relational database constructed for the study. Each box represents a real world object and the name of that object is indicated by the bold text. The data elements are listed in non-bold text and the primary keys are indicated by italic text. The arrows show the relationships between the objects. The many-to-many relationship that exists between point occupants and coral traits is managed by the intersecting objects I and II.
153 4.5.Sampling area and effort
The cost of underwater reef surveys is high, especially in remote areas like Madagascar, where poor road infrastructure makes petrol delivery for boats exceptionally expensive. Because of the high costs involved, in combination with the logistical and safety challenges of conducting reef surveys in a remote region, it was essential to streamline data collection and collect as much data as possible during each 25-75 minute dive.
The amount of total dive time spent allocated to each reef site was directly related to the depth of the reef (air consumption rates increase with depth) and the strength of the currents present at each site (strong currents require increased physical effort which increases air consumption rates). The amount of total dive time allocated to each reef site determined how many photoquadrat images could be taken and how much area could be sampled.
It is common to predetermine the number of photoquadrat images and transects to be conducted at each reef site and depth. Unfortunately, this was not a practical approach for surveying the reef sites in Southwest Madagascar since documentation for most of the reef sites were either poor or absent. Information about reef type, depth, and size were often not known prior to surveying. Therefore the goal became to gather as much data as possible and to then construct a sampling design based on the data that could be collected. This involved determining: 1.) the depth zones to compare between sites, 2.) the level of total sampling area (i.e. no. of images) at which to compare reef sites in each depth zone and 3.) the level of sampling effort (per image) at which to compare the the sites. The methodology used for making these decisions is laid out in the following three sections.
CH4: Field sampling