<<  <  >  >>

 

Usefulness

Suggested sampling periods include late spring or

early summer (May to June), when highest densities

Amphistegina makes an ideal bioindicator because:

will be observed in healthy populations and when

photic stress (bleaching) will be most prevalent in

· They require similar environmental conditions to

impacted populations, and in late summer (August to

zooxanthellate corals,

September) when shell damage will be most prevalent

under chronic stress.

· They are an easily identifiable, widely distributed

genus  that  is  abundant  in  healthy  reef

The equipment needed to take actual UV radiation

environments,

measurements on the reef are relatively expensive and

require frequent measurements. In lieu of expensive

· They have relatively short life spans and are sensitive

direct UV measurements, the Amphi Index provides

to changes in environmental conditions over days to

a time-integrated response to UV stress that also

weeks, providing an early warning signal of declining

has relevance for corals due to the synergistic effect

water quality or episodic stress events, and

of UV stress affecting corals exposed to elevated

temperatures.

· Statistically-significant  sample  sizes  can  be

collected quickly and relatively inexpensively with

Status

Status

minimal impact on reef resources.

Data on the density of MAR Amphistegina populations

High densities of adult and juvenile Amphistegina

are not currently available, but the index has been

with low percentages of bleaching and breakage are

well developed for the Florida Keys. Historically,

representative of optimal reef conditions. Absence

Amphistegina were abundant in reef sediments with

of Amphistegina or low densities with some juveniles

densities > 104 #/m2 and exhibited 0% bleaching and

but few to no adults are indications of water quality

<5% damage54. However, bleaching in Amphistegina

unsuitable for maturation and successful reproduction

populations was observed in samples from Montego

of Amphistegina. The assumption of the index is that

Bay, Jamaica, in 1992; at Glover's Reef, Belize, in

such conditions will not support other reef-building

1998; and in Roatan, Honduras, during several years

organisms either.

since 199555.

This index is most suitable for assessing reef

Data Needs

Data

environments between approximately 6 and 30 m

depth. However, it is not suitable for assessing the

Formal evaluation of the Photic (Amphi) index by

condition of nearshore reef environments that contain

EPA standards is not yet complete.  The index is

silty sediments. Comparisons should be made among

currently being assessed using large data sets from

similar reef types and depths due to natural variability.

throughout the Florida Keys spanning the early 1990s

to the present. Data collection in the MAR should be

conducted in coordination with the collection of other

climate change indicators at the same sites.

Pamela Hallock

D1 3

D1

Gradient of bleaching from normal (upper left) to bleached (lower

right).

115