Pocillopora Head Sampling and DNA Sequencing
The two key methodological components upon which CReefs focused are molecular analyses and standardized sampling.
Systematic Sampling Via Pocillopora Heads (see also ARMS)
A major component of the CReefs strategy to better understand reef biodiversity is systematic sampling, with samples analyzed using molecular techniques (described below), widely applied. One of the most efficient methods to find species when they are large enough to be seen is via hand sampling, using divers ranging over a reef. However, the effort required to enumerate diversity properly can be daunting (May 2004), and divers vary enormously in their abilities in this regard, making it very difficult to compare work from different places and times involving different people.
In response to this, two particular methods have been developed by CReefs:
- Assessment of organisms (esp. crustacean) living in heads of dead Pocillopora coral
Images (Courtesy Smithsonian and Juergen Freund@FreundFactory, Scripps): Invertebrate extractions from dead Pocillopora coral heads, (left to right) Laetitia Plaisance breaks open dead coral head; Plaisance instructs youth at Moorea
- Assessments of organisms settling into Autonomous Reef Monitoring Structures (ARMS) placed on the reef for one to three years.
Image: Model of single ARMS unit developed by Daniel Merritt, NOAA Fisheries
Systematic Sampling Using Dead Pocillopora Coral Heads
Using communities of invertebrates living in dead heads of the coral Pocillopora as proxies for reef diversity has multiple advantages:
- Can be implemented immediately (important consideration given the short time-frame for CReefs from its founding to the close of the initial Census of Marine Life funding)
- Interpretation is not confounded by concerns associated with artificial substrates
- Assessment of Pocillopora heads can be replicated from the Red Sea to the Eastern Pacific (and with some adjustments, reef rubble in the Caribbean can also be compared)
- Dead coral head sizes can be only roughly standardized
- Ages cannot be known with any precision (one can collect heads that are old enough to be covered with fouling sessile organisms but young enough not to have been substantially bioeroded, to provide some standardization)
- Removal of reef (esp. live rock) requires permits with much stricter regulations