RUGOSIT Y
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What
What Is It?
BENCHMARK
Rugosity is a measure of the "ruggedness" or
No reduction in current MAR-wide
topographic complexity of the reef surface. One
average rugosity values by habitat.
expression of rugosity (among many) is given
Measurable increase in rugosity in
by the maximum reef relief. In this book we use
shallow reefs impacted by recent
the terms "rugosity" and "maximum reef relief"
hurricanes.
interchangeably.
TA R G E T
Reef relief is defined as the distance between the
tallest coral or reef rock and the lowest point on
To be developed after additional data
the reef substratum16. Thus this is different than
are
are acquired.
measuring the overall extent of the reef's structural
RED FL AG
development (e.g. a hard bottom versus high-relief
spur and groove which would be measured down to
To be developed after additional data
To
the sand floor off of the reef substrate).
are
are acquired.
Why
Why Do We Measure It?
Usefulne s s
A reef's structural complexity affects how the reef
functions. Reefs provide shelter and microhabitats
Rugosity is a useful indicator of overall reef structure.
for many organisms. The spatial distribution of
reef organisms is often closely related to a reef's
As an indicator of reef structure, rugosity is not an early
rugosity. Branching corals and massive species (e.g.,
warning signal. However it can provide a useful tool in
Montastrea faveolata), in particular, give a reef higher
assessing damage from human (e.g., boat groundings)
rugosity and complexity than most other, smaller
or natural (e.g., hurricane) events. Rugosity varies
corals.
naturally with reef type (i.e., some reefs have low
complexity and are `healthy'). Comparisons among
Reefs that are more structurally complex provide a
different reefs should take into account different
wider variety of habitat (although a higher rugosity
habitat types.
may not equate directly to overall better health). Loss
of habitat complexity has direct impacts on numerous
Reef relief (i.e., distance between highest and lowest
plant and animal inhabitants and associated
point along a transect line) is quick and easy to
productivity.
measure and can be done over small and large spatial
scales, although some resolution of microhabitat
How Do We Measure It?
How
complexity may be lost.
We recommend using the AGRRA methodology, which
St atus
Status
entails a diver making five quick measurements along
the same 10-m transect lines used for studies of
Overall, the status of MAR reef rugosity is considered
benthic cover16. The diver measures the reef height
fair because it is an "average" of the "poor" state
-- that is, the distance from reef top to reef bottom.
of rugosity at shallow reefs (low rugosity due to
(Reef bottom in this case refers to the base level at
widespread coral breakage during hurricanes), and
which corals grow. Measurements should not include
the "good" state (high rugosity) at deep fore reefs19.
the lower sand valleys in spur-and-groove systems).
This metric of "maximum reef relief" is measured as
For shallow reefs, the Caribbean average for rugosity
the difference (in centimeters) between the highest
(AGRRA maximum reef relief) is 72 cm. Reefs in
and lowest points within a one-meter radius of
Mexico (64 cm) and Belize (49 cm) are below the
established intervals along the benthic transect line,
Caribbean norm19. Shallow reefs throughout the MAR
as in AGRRA.
region were affected by the 1998 bleaching event and
catastrophic hurricane (Mitch) that killed, flattened
and even removed many corals.
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