Extracted from Turneffe Atoll Status Report 2010, Discussion Section
Turneffe Atoll is widely known for its extensive mangrove cover which represents
approximately 12% of the Belize's national mangrove cover (Meerman, 2005). The mangrove
site located on the leeward side (West Mangrove) of the atoll presented larger DBH, taller
canopy height and lower density than the site on the windward side of the atoll (Calabash Caye).
These differences in measurements may indicate that conditions on the leeward side of the atoll
have been more conducive to development of the mangrove forest structure as indicated by the
tall mangrove canopies and large DBH measurements. A more mature forest structure (based on
measurement of DBH and height) may not necessarily indicate a healthy habitat, since this may
be compromised by very low densities of plants that could affect the life cycle of plants,
particularly at the early stage. Low density forests usually tend to have large gaps of terrain,
giving opportunistic plant species (grass) the chance to become established and out compete
seedlings and saplings. On the other hand, high density habitats may be unhealthy due to short
height and small DBH (MBRS, 2006). In order to track the health of mangrove habitats, long
term monitoring of the forest structure and habitat is recommended. These differences between
the windward and leeward side of the atoll may indicate differences in mangrove habitat type.
Based on the extensive mangrove cover at Turneffe Atoll it is recommended that at least two
more permanent sites be established across the atoll to be representative of the different regions.
The results generated will allow for comparison across spatial and temporal scales.
The most extensive ecosystem in the Turneffe Atoll is seagrass beds. Seagrass represents
approximately 67% of Turneffe Atoll (Meerman, 2005). Seagrass is crucial as the primary food
source for species such as sea turtles and manatees and also as habitat for juvenile reef fish,
invertebrates and commercial species such as conch and lobsters (MBRS 2006). After
mangroves, seagrass serve as a secondary barrier to stabilize coastal seabottoms, absorb nutrient
runoff from coastal development and stabilize sediments. In Belize five species have been
documented Thalassia testudinum, Syringodium filiforme, Halodule wrightii, Halophila
decipiens and Halophila bailloni (SeagrassNet 2004). Three of the five species of seagrass are
present at Turneffe Atoll; two were documented at the established sites: Thalassia testudinum,
Syringodium filiforme.
The seagrass sites were very alike in terms of biomass; this is despite the difference in location
within the atoll (windward and leeward). The distribution of biomass across the different sections
of the plant differs however. In the results obtained for Calabash Caye site, the biomass ratio of
above ground: below ground appear to indicate that the site is not a healthy one. An above
ground biomass larger than the below ground biomass suggests that the plant does not have the
necessary components (roots and rhizomes) to uptake sufficient nutrients and store starch. This
may be as a result of poor water quality and can affect stability during storms and asexual
reproduction (MBRS 2006). It is important to note that this result is based on one monitoring
session and thus further regular monitoring is recommended to support or confirm this
assessment.
Coral reefs support two major industries in Belize: tourism and fisheries. Reefs also provide
shoreline protection that is crucial for the development and settlement along the coast. In 2008, the World Resource Institute estimated that the economic contribution of the reef to Belize is between USD 268 and 370 million dollars (WRI 2008). Turneffe Atoll represents 15% of Belize's coral reefs, (Meerman, 2005) and like the Caribbean and Mesoamerican region, over the
past decades it has experienced numerous impacts both natural and anthropogenic, such as
storms, coral bleaching, ship groundings and coastal development.
In general the reefs at Turneffe Atoll were identified as being in POOR health. The major
contributing factors were lowered abundance of herbivores (urchins and fish) and poor coral
cover. Healthy Reefs 2010 reported a fleshy macroalgae cover of 17.3% for 2009. The 2010
MBRS assessment show a macroalgae cover of 16.5%. This cover of macroalgae may not yet
reflect the large absence of herbivores, which was reported to be twice as abundant in 2009 with
a mean biomass of 1144 g/100m2 (Healthy Reefs 2010). The 2010 MBRS assessment show a
mean biomass of 781 g/100m2. This impact of a decline in herbivore fish abundance may not yet
be reflected and will require long term monitoring to detect changes.
The dominant benthic component was sand, with 40% cover ( Figure 13). The
abundance of sand however is not factored into determining the reef health and therefore may
often be underrepresented. A large abundance of sand may be indicative of large scale sand
production through processes such as the break-down of calcareous algae, erosion, and
consumption of calcareous algae by herbivorous species.
Stony coral only comprised 9.55% of the benthic community. Most of these stony corals were
made up of branching and plate corals such as Millepora and Agaricia. Due to their structural
formation, these corals provide critical habitat to reef fish, however this feature also limits the
size of fish that can inhabit the crevices. These corals are also very prone to storm impacts which
often results in fragmentation and loss of habitat. Therefore these corals may be limited in their
capacity as habitat for juvenile and sub-adult fish. The major reef building or reef framework
species such as Montastraea and Diploria were uncommon. These species creates more ideal and
three-dimensionally complex habitats than the smaller plate or branching species. Also Acropora
abundance is severely limited, indicating their continued endangered status.
The healthiest coral reef habitat observed across Turneffe Atoll was back reefs (Figure 20) with
a health ranking of FAIR. The largest biomass of herbivorous and commercial fish species were
observed in these habitats along with low percentages of macroalgae cover and in some instances
good coral cover, 20%-39%. These back reef habitats were located near to channels and thus the
constant exchange and circulation of water along with protection from wave action and access to
reef fish may contribute to the health of the back reef habitats.
Another pattern noted was that the three sites identified in the best health condition (FAIR),
were located on the southern part of the atoll. Three factors were noted to greatly influence this
result. Macroalgae cover was much less on the southern part of the atoll. Coral diseases were
almost absent at the sites monitored. And commercial fish biomass was usually between the
FAIR and VERY GOOD categories. Based on this information, a difference in reef health is
noted between the northern and southern parts of Turneffe Atoll. This trend has also been
highlighted by fishermen of Turneffe Atoll. This information needs to be incorporated into any further assessments or considerations for management of the Turneffe Atoll.
AmbergrisCaye.com 
