Status
Status
Given the great variety of reefs and communities
in the MAR, macroalgal abundance varies greatly
over the region. Some local reefs have very high
macroalgal abundance. Glover's Atoll (Belize) patch
reefs experienced a 315% increase in algae (mostly
Lobophora, Dictyota, Turbinaria and Sargassum)45.
Algal production was estimated to be about 8 g (wet)
per m2 per day -- very close to the theoretical upper
limit of about 9 g per m2 per day (projected amount of
biomass a sugar cane field might produce)40.
In 1999-2004 AGRRA surveys, the average macroalgal
index (i.e., the product of percent macroalgal cover
and average canopy height) was higher for Mexico
(index = 99) than Belize (62). Both MAR values are
lower than the Caribbean average value of 1299.
The macroalgal index is generally higher on fore reefs
than on shallow reefs. In the 1999-2004 AGRRA
surveys, the index ranged from 36 to 163 (average =
87) on reef crests and from 25 to 192 (average = 105)
on fore reefs in Mexico. In Belize, the index ranged
from 13 to 93 (average = 42) for shallow reefs and
Shalini Cawich / WWF
from 33 to 249 (average = 69) on fore reefs9.
Data Needs
Fair amounts of data are available for algal cover and
average algal height from the AGRRA database, MBRS
database and various published studies. No complete
synthesis has yet been attempted.
Additional regional AGRRA data on macroalgal
abundance were collected across the MAR in 2006.
These data, which complement the MBRS SMP data,
will help us understand how macroalgal distribution is
related to other factors such as coral cover, herbivore
abundance and level of protection from fishing (in
MPAs).
Additional information is needed on how best to
proactively reduce macroalgal abundance or increase
levels of herbivory.
Refinements of this target should consider
complementary targets for herbivore biomass,
Diadema densities, coral cover, water quality and
level of human alteration.
Melanie McField / WWF
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