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E  C O S Y S T E M FU N C T I O N I  N D I C AT O R S

REEF ACCRETION & BIOEROSION

Conservation Objective

To promote the environmental and ecological conditions that sustain reef accretion and the maintenance

of reef frameworks for long-term viability. Identify areas and causes of high bioerosion (e.g., areas of

nutrient enrichment) and implement mitigative measures.

Threats

Coral growth can be reduced by disease, bleaching, competition/predation, hurricanes, pollution

(including sedimentation and nutrification), direct removal or damage, and global climate change.

Nutrient enrichment from sewage and continental runoff (due, for example, to coastal development or

agriculture) can increase bioeroders. Increased atmospheric carbon dioxide concentrations could lead

to reduced coral calcification, which would further reduce reef accretion.

Management Actions

·

Improve our understanding of bioerosion and reef accretion in the MAR.

·

Eliminate sources of direct human impact, especially dredging and boat groundings.

·

Restore coral abundance to levels sufficient to maintain net reef accretion.

·

Re-evaluate MPA design to ensure reef accretion is incorporated into planning.

·

Reduce runoff, especially nutrients associated with agricultural practices and coastal development

(through better farm management and sewage treatment).

· Reduce human activities contributing to global climate change.

also rising sea level. It is unclear whether projected

Reef accretion (that is, reef build-up or reef growth)

rates of future sea level rise may outpace some slow-

occurs when reef framework (which is composed

growing reefs.

mostly of calcium carbonate) accumulates faster than

it is eroded.

If calcification rates decrease for some reason -- for

example, due to a detrimental change in water quality

Processes contributing to reef accumulation include

-- a reef's ability to keep up with rising sea level may

calcium carbonate deposition by reef organisms

decrease; its susceptibility to bioerosion and physical

(e.g., corals), as well as lithification or submarine

damage may increase; and its community structure

cementation (e.g., by coralline and calcareous algae).

may change from calcifying to non-calcifying.

Processes contributing to reef erosion can be physical

Ultimately, there may be a loss of the reef structure

or biological. Bioerosion is the erosion of rock and

itself.

skeletons by boring algae, sponges and other species

that consume calcified materials.

Reef accretion, which receives little to no attention in

most monitoring programs, is really the "bottom line"

Community composition is an important determinant

of the reef's ecological balance sheet.

of reef accretion -- or non-accretion. If the community

is dominated by non-calcifying organisms, such as

Indicators selected to track reef accretion and

fleshy macroalgae, reef accumulation may not be

bioerosion are:

able to "keep up" with erosion. If a reef experiences

a die-off of corals, coralline and calcareous algae,

F8

Coral Growth

it may actually shift from a state of net framework

construction to a state of net erosion.

F9

Bioeroders on Coral

Reefs in most areas must also grow fast enough,

F10

Reef Accretion

over the long term, to outpace not just erosion but

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