Land-reef and reef-reef connectivity in Meso-America inferred from satellite
ocean color observations during 1998-2006
Inia Soto1, Serge Andréfouët2, Chuanmin Hu1, Frank E. Muller-Karger1, Carrie Wall1, Jinyu
Sheng3, and Bruce G. Hatcher4
1
Institute for Marine Remote Sensing, College of Marine Science, University of South Florida, St.
Petersburg, FL 33701, USA
2
UR 128 Coréus, Institut de Recherche pour le Développement, BP A5-98848, Noumea Cedex,
New-Caledonia
3
Department of Oceanography, Dalhousie University, Halifax, Nova Scotia, B3H 4J1, Canada
4
Marine Ecosystem Research, Cape Breton University, Sydney, Nova Scotia, B1P 6L2, Canada
Abstract
Weekly time series of Sea-viewing Wide Field-of-view Sensor (SeaWiFS) satellite ocean color
images acquired from 1998 to 2006 were used to determine connectivity patterns between land and
reefs, and among reefs in the Mesoamerican Barrier Reef System (MBRS) of the northwestern
Caribbean Sea. A connectivity matrix was constructed for seventeen domains that cover major
reefs in the MBRS and coastal waters off the most prominent rivers in Honduras and Nicaragua.
Ocean color images (weekly mean and weekly climatology) were carefully examined, and spatial
connections between domains were recorded. The weekly time series of 466 images provide not
only a clear view of seasonal distributions of the connectivity patterns, but also evolutions of
estuarine plumes and transitions in the aftermaths of major perturbations like hurricanes in the
MBRS. River plumes leaving Honduras impacted the Bay Islands (Utila, Guanaja, and Roatán) in
Honduras as much as 969 times over the 9-year periods [where does this 969 come from? You
have only 466 weekly images]. Reefs in Belize, in particular the southern part of the Belizean
barrier reef and Glovers atoll, were hit every year mostly during the rainy season during the 9-year
period. Glovers was reached by different rivers in Honduras 104 times during the study period.
Turneffe, the closest atoll from the land, was impacted directly mostly by materials from Belize
lagoon 222 times. Plumes from eastern Honduras reached as far as Chinchorro and Cozumel in
Mexico. Chinchorro appeared more frequently connected to Turneffe and Honduras than from
Glovers and Lighthouse atolls. These results bring new products to be used in quantitatively
reassessing long term connectivity in the region and validating fields produced by other modern
approaches based on numerical modeling.
1. Introduction
The conservation and management of marine resources requires not only a good understanding
of environmental factors affecting coral reefs at local levels, but also reasonable knowledge of
large-scale connectivity with terrestrial environments and with other marine environments. A
better understanding of the physical connectivity associated with the water movement is necessary
to study accurately marine processes (e.g. larval dispersal), manage marine resources in a
sustainable way (e.g. fisheries and marine biodiversity), and protect their biodiversity (e.g.
implement marine protected areas). Thus, connectivity in marine resources should be seen as a
transboundary international issue. The limits of the management unit should be defined based on
local and large-scales circulation patterns, both coastal and oceanic [Roberts, 1997].
Increased terrestrial runoff carrying sediments, nutrients and other pollutants into the ocean is a
concern for coral reef managers [ISRS, 2004]. Direct exposure of corals to runoff can cause
smothering, energy expenditure for surface cleaning and shading among other effects depending
on the pollutant and nutrients involved [Rogers, 1990]. A better understanding of the connectivity
(especially between land and reefs) can be used as a decision tool for managers to regulate
agricultural practices, coastal development and any other anthropogenic factors that might affect
marine resources. In the Caribbean Sea, land clearing, coastal and agriculture development have
made the issues even more pressing and contribute with other stressors (e.g. coral bleaching,
diseases, physical destruction due to hurricanes) to the coral reef ecosystem decline. For instance,
Honduras and Belize experienced in 1998 a devastating hurricane kown as Hurricane Mitch and a
major bleaching event [Mumby, 1999; Harborne et al., 2001]. The combination of elevated
temperatures with the effects of Hurricane Mitch probably caused a stressful combined effect to
coral communities in the Mesoamerican Barrier Reef System (MBRS) [Kramer and Kramer,
2002].
Satellite ocean color imagery provides a valuable tool to trace water movement and to
document surface patterns, plumes, and connectivity between various environments (Andréfouët et
al., 2002; Hu et al., 2004). This is particularly useful for the subtropical and tropical coastal oceans
during summer when sea surface temperature is nearly uniform and therefore lacks any spatial
contrast to detect patterns (e.g., Hu et al., 2005). Further, analysis of ocean color time-series may
yield information on the potential causes of benthic degradation (e.g., Hu et al., 2003), which is
otherwise difficult to obtain. The coastal water movement generated by Hurricane Mitch was
examined using Sea-viewing Wide Field Sensor (SeaWiFS, Hooker and Esaias, 1993) imagery by
Andréfouët et al. [2002]. River plumes generated by Mitch coming out of Honduras were seen
reaching Belize and as far as Cozumel and other areas in Mexico, and lasted for almost two
months. The patterns revealing Glovers atoll surrounded by colored water originating from
Honduras were discussed under the angle of reef connectivity. The results proved that, during
extreme events, Glover was not isolated from river plumes, neither from Belize nor Honduras
contrary to previous belief [e.g. McClanahan et al., 1998]. In addition to specific events like
hurricanes, Andréfouët et al. [2002] also suggested the possibility of connectivity between MBRS
reefs by river plumes coming out of Honduras and Belize during normal conditions or on a
seasonal basis since such recurrent patterns were observed in other Caribbean regions [e.g. Hallock
et al., 1993; Muller-Karger et al., 1995]. In recent years, scientists focused on developing
numerical models in order to understand reef connectivity in the Caribbean Sea and in particular in
MBRS. However, these models were often not validated by any in situ observations [Cowen et al.,
2006; Tang et al., 2006]. Sheng et al. [2007] revisited the impact of Hurricane Mitch using a
nested-grid three-dimensional (3D) ocean circulation model, validated by the SeaWiFS
observations highlighted by Andréfouët et al. [2002]. The combination of both tools, numerical
modeling and remote sensing, was followed by others to study reef connectivity [Cherubin et al.,
2007] but the number of scenarios remain limited to few specific cases like Hurricane Mitch.
This study aims to construct climatology of connectivity between the MBRS land and reefs and
between reefs from nine-year time-series of SeaWiFS ocean color data during 1998-2006. Both
normal conditions and hurricane-like events are considered through the examination of SeaWiFS
data.
2. Methods
The study area is the Mesoamerican Barrier Reef System (MBRS), which includes Mexican
reefs (reefs along the Yucatan Coast, Cozumel Island, and Chinchorro Bank atoll), Belizean reefs
(three atolls: Lighthouse, Turneffe, and Glovers), a large barrier reef, and fringing and rhomboidshaped reefs in the south of the northwestern Caribbean Sea. The MBRS also includes fringing
reefs surrounding the Bay Islands (Roatán, Guanaja, and Utila) and Cayos Cochinos, a coastal
barrier reef along North side of Roatan, Honduras shelf areas known to have high coral cover, and
the reefs along the Swan Islands and the Mosquitia cays and banks [Harborne et al., 2001].
[Hu: These places need to be annotated on Fig. 1.]
The MBRS receives river runoff from Belize, Guatemala, Honduras, and Mexico. Most of the
sediment and nearly 80% of the nutrients originated from (?) Honduras [Burke and Sugg, 2006].
To understand the connectivity between rivers and reefs, and reef to reef, seventeen domains were
chosen for major reefs and coastal waters off major river mouths in the study region (Fig. 1). Areas
covering atolls and Islands such as Turneffe Atoll (TUR), Lighthouse Atoll (LH), Glovers Atoll
(GLO), Banco Chinchoro, Cozumel, and Bay Islands (Utila, Guanaja, and Roatán) were
considered as individual domains. The Belizean Barrier Reef was divided into three domains
(BR1, BR2, and BR3) from south to north based on natural boundaries (mangrove forest
abundance, reef passes and inflexion in the direction of the barrier reef). The five domains along
the Caribbean Coast of Honduras include major river deltas of Honduras; R1 (Ulúa River), R2 (El
Cangrejal River), R3 (Aguán River), R4 (Sico Tinto River), and R5 (Patuca River). Another
domain (NIC) was added for the border between Nicaragua and Honduras that includes Coco
River (Nicaragua) and Caratasca Lagoon (Honduras).
Full resolution (1 km2 / pixel at nadir) SeaWiFS ocean color data were used in this study. Daily
images collected using the High Resolution Picture Transmission (HRPT) antenna located at the
University of South Florida (USF) in St. Petersburg of Florida (USA) were processed using the
SeaDAS software (Version 4) developed at the National Aeronautics and Space Administration
(NASA). After calibration of the satellite spectral signal, atmospheric effects were removed using
algorithms developed by Gordon and Wang [1994] and others, and the resulting surface spectral
reflectance was used with an empirical band-ratio algorithm (OC4v4, O’Reilly et al., 2000) to
estimate chlorophyll-a (Chl-a) concentrations in the surface ocean. Chl-a products from 1998 to
2006 were mapped to a cylindrical equidistant projection, and then used to compute weekly mean
and weekly climatology for the 9-year period, resulting in 466 weekly mean images and 52 weekly
climatology images. During computing the mean, all suspicious pixels, as defined by the various
quality-control flags (e.g., large sun or viewing angle, clouds, stray light, etc.) were excluded. No
images were available for the first 2 weeks of October 2002 due to satellite or antenna malfunctioning. The use of the weekly time-step is to retain both high temporal resolution and cloudfree coverage.
Weekly mean images were analyzed by visual analysis and by using the Single Image Edge
Detection (SIED) histogram algorithm developed by Cayula and Cornillon [1992, 1995]. The
SIED algorithm uses a bi-modal histogram distribution within a specific area of the image to
automatically detect oceanic fronts from satellite data. The distance between the two modes
determines the strength of the front; the farther away the modes, the larger the frontal gradient. The
histogram analysis is followed by several steps to statistically verify the existence of a front and
reduce the influence of clouds or noisy data. Threshold adjustments were made to compensate for
the study area’s coastal environment. Details of those changes can be found in Wall [2006].
Additionally, a 16 x 16 pixel window was used to calculate the histogram instead of the default 32
x 32 pixel window to increase its sensitivity. SIED was used to quantitatively verify the visual
interpretation. Visual analysis has been proven to be more efficient in subtle low contrast areas, but
it is subjective and may not be consistent from one analyst to another. Even though the entire timeseries was analyzed visually, objective and repeatable confirmation was sought using SIED. SIED
was previously used to detect thermal fronts [e.g. Ullman and Cornillon, 1999] and chlorophyll
fronts in the coastal zone of the northwest Atlantic [Stegmann and Ullman, 2004] and off westcentral Florida [Wall, 2006]. The SIED algorithm was applied to every weekly image from 1998 to
2006 (466 images in total) to determine the frequency when a front connected two or more of the
defined domains (Fig 1).
For most images, the SIED algorithm detected successfully fronts and plumes, but visual
interpretation detected many more connections. For some images, the SIED algorithm failed to
distinguish some patterns that were visually distinguishable. Curvilinear features are a known
limitation for the SIED algorithm, as it does not delineate a front that rotates over 90° within a 16 x
16 pixel box due to a violation in the cohesion analysis, a verification step within SIED.
Additionally, noisy images impede the ability of the algorithm to detect fronts that may be visually
identified in the composite image. Verification of these plumes was completed by visually
validating the spatial location of the front within individual daily images used to derive the weekly
composite image. Since images were processed and color-coded the same way, the threshold in
mg/m3 of Chl-a used to define a front or a plume was relatively constant. However, it should be
noted that the color of plumes is not only due to Chl-a, but also due to other materials, for example
colored dissolved organic matter (CDOM) and suspended sediments. These materials are rich in
riverine waters, and they may lead to large errors in the SeaWiFS Chl-a data
because the
empirical band-ratio algorithm does not explicitly distinguish them from Chl-a. However,
SeaWiFS Chl-a in this study was used only as a relative color index to define fronts and plumes,
and the errors in the absolute value should not alter our results.
3. Results
The weekly mean climatology (averaged over the 9-year period between 1998 and 2006)
captures the typical seasonality of ocean color images for the study region. Precipitation in the
Carribbean coast of Honduras and Belize is dominated by the easterly tradewinds. The wettest
months of the year are usually from June to September, and the driest months are February to
March [Heyman and Kjerfve, 1999]. During the winter, the northerly cold fronts also contribute to
the total annual precipitation [Portig, 1976]. The climatology does not show specific events (e.g.
hurricanes) or single plumes. However, there are several dominant features in the climatology (Fig.
2), suggesting recurrent patterns in most years. Plume dispersal was at their lowest between
February 19 to June 17 (weeks 8 to 24) (Fig. 2a). Outside this time window, a series of prominent
plumes from the Ulúa River (domain R1) reached Glovers atoll and the Belize barrier reef (Figs.
2b,c,d) and Lighthouse (Fig. 2c). Plumes seen in figure 2b(?) and 2c might be associated with the
rainy season, while the activity of river plumes in figure 2d might be associated with heavy rains
caused the seasonal northerly cold fronts. Connectivity was evidenced between the barrier reef
and the Belizean atoll (Figs. 2b,c,d). Glovers, Turneffe, Lighthouse, and the Bay Islands received
discharges from Aguán River (domain R3) (Fig. 2d).
In the weekly mean ocean color images, a variety of plumes and connections from reef to reef
and from river to reef were apparent (Fig. 3). Plumes generated originally in the coastal waters off
Honduras reached reefs in Belize and the remote Mexican reefs (Chinchoro and Cozumel) a few
weeks to a few months later (Figs. 3B-D). In the dry season, by contrast, the connectivity in the
MBRS is very low (Fig. 3a). Large and single events are also evident in the weekly mean timeseries (fig. 3). Figs. 3B and 3C show the Chl-a distributions before and after Hurricane Mitch,
revealing significant perturbation and river runoff, which lasted at least one month, as shown in
Fig. 3c. In contrast to this extreme event, Figs. 3D-I illustrate various connections among different
domains that were common but not related to any specific events.
For simplicity, the synthesis of the census is presented in the form of a connectivity matrix
shown in Table 1. The connectivity matrix provides the frequency of river-reef and reef-reef
connections, and is a simple representation of how many times the domains are connected in a
given period. Connectivity matrices have been used to characterize larval dispersal in the past. For
example, Cowen et al. [2006] used connectivity matrices based on a biophysical model to
represent the probability of virtual larval leaving a reef site and being recruited at another reef site
during a given period of 30 days. A connectivity matrix was created for the 9-year period and for
the 17 domains to summarize the census in terms of actual count, and probabilities. The
directionality of the connectivity between islands and atoll was not accounted for in the matrix, but
plume motion through a series of images provides direction if needed. Connectivity number was
thus assigned only to one of the two possibilities (e.g. Guanaja to Roatán, and not Roatán to
Guanaja).
The connectivity matrix in Table 1 demonstrates that the Bay Islands (Guanaja, Roatan and
Utila) are almost constantly influenced by river run-offs along the Caribbean Coast of Honduras
[why? Is this shown by a connectivity number? Say so if yes. Also, in the Table caption, describe
what the symbols mean], including Ulūa, El Cangrejal, Aguán , Sico Tinto and Patuca River
among other smaller rivers in the area. Domain R2 includes El Cangrejal River and other small
rivers near the third largest city of Honduras, La Ceiba. Utila and Cayo Cochinos reefs are
downstream of R2, and the plumes reached them more than 65% of the time (303/466). Roatan and
Guanaja Islands were reached mainly by the R3 domain (Aguán River), more than 46% of the
study time (215/466 for Guanaja and 230/466 for Roatán). They were also less frequently reached
by other domains. For example, Guanaja was reached by R4 more than 12% of the time (59/466),
and Roatán was reached by R2 more than 9% of the time (44/466). Connections also occurred
among the Bay Islands in Honduras: Guanaja and Roatán were connected 40% of the time
(189/466), while 26% (123/466) from Roatán to Utila and 12% (55/466) from Guanaja to Utila.
Honduran rivers also reached Belize atolls and the Belizean barrier reef. The Ulúa River
reached the southern part of Belizean Barrier Reef (BR1) 60% of the time (283/466). Other parts
of the Belizean barrier reef were also affected by the discharge of River Ulúa. This river also
reached Belize atolls, especially Glovers (17% (81/466) more than other atolls further north
(Lighthouse: 4% (19/466). Other Honduras-born river plumes reached the Belizean atolls, but far
less frequently (less than 18 counts total). The remote Mexican reefs like Chinchoro and Cozumel
were also affected by plumes leaving Honduras, especially after hurricanes and extreme weather
events (e.g. Chinchoro : 23 counts from R4, Cozumel: 6 counts from R4).
Other land-reef connections are visible offshore Belize, coming from Belize mainland and
rivers and flowing through the main barrier reef channels. These plumes are short, but reach
frequently the atolls (e.g. 24% (116/466), Glovers), enhancing inter-atoll connectivity. The
connectivity among the atolls was high for Glovers and Turneffe (81/466, 17%), slightly lower for
Glovers and Lighthouse (50/466, 11%), and rare between Turneffe and Lighthouse (8/466, 2%).
In general, Lighthouse and Mexican reefs are the most isolated from land sources, and from
other reefs in the area.
4. Discussion
The main objective of this study was to quantify connectivity between coral reefs and rivers in
the MBRS using SeaWiFS satellite ocean color imagery. The weekly climatology over the 9-year
period from 1998 to 2006 provided the mean seasonal patterns, while the weekly time series
showed a more detailed, temporally continuous, picture of the coastal and offshore water patterns.
Estuarine plumes and those caused by hurricane-like events were easily detected in the weekly
time series.
Numerical ocean circulation models have increasingly been used in quantifying the ecological
connections in the coastal and open waters [Roberts, 1997; Cowen et al., 2006; Tang et al., 2006].
The connectivity matrices elaborated here could in principle be used in validating numerical
results, if the modeling exercise aims to compute connectivity between coastal and reef domains
close to those defined here. This work is a follow up of Sheng et al. [2007] where SeaWiFS data
were used to validate their numerical predictions. In the long run, more connectivity modeling, like
in Tang et al. [2006], should be compared with ocean color climatology for validation. The present
study also complements the study by Cherubin et al. [submitted, 2007] where few selected daily
SeaWiFS images were used. Cherubin et al. [submitted, 2007] also provides a detailed
connectivity matrix elaborated by numerical models. Theoretically, this matrix and those provided
here should be comparable and should agree [do they? This should be briefed here. Otherwise a
reviewer may raise the same question]. This is the case since both matrices provide similar patterns
and connectivity climate. [so they do agree. In what sense? Can you give some quantitative
numbers?]
One of our findings is that estuarine plumes originated at the coastal waters off Honduras nearly
always reach the Bay Islands and periodically reach the Belize reefs, especially during the rainy
season and more effectively during extreme storm events like hurricanes during the study period.
Mexico reefs are not remote enough to avoid exchanges with Honduras and Nicaragua rivers, and
with reefs between [?]. Our results suggest that river plumes travel farther than what was
previously thought, confirming the importance of international reef management from Mexico to
Nicaragua. Glovers Atoll is one of the reef atolls most connected to Honduran river, especially
from the Ulúa River. A hydrological model provides an overview of regional patterns of
sediments, nutrient runoff and delivery in the MBRS Flowing over 400 km through economically
important Valle de Sula before discharging into the Caribbean Sea, the Ulúa river is one of the
largest rivers in Honduras [Merrill, 1995; Burke and Sugg, 2006]. The hydrological model [Burke
and Sugg, 2006] also suggested that near 80% of the sediments and half of the nutrients (nitrogen
and phosphorous) that is delivered to the Mesoamerica region originates in Honduras, and the Ulúa
Watershed was the largest contributor of sediment and nutrients. The findings of Burke and Sugg
[2006] and this study suggest that the reefs in Honduras and Belize are directly impacted from
land-based activities in Honduras. Also, river plumes leaving Belize directly impact the Belizean
Barrier Reefs and often the atolls, namely Turneffe.
Increased land erosion, climate change with more rains, and sediment transport may all present
a threat to local and remote coral reefs through the connections demonstrated here. The use of
ocean color products as a tool to identify connectivity provides an opportunity to promote
management partnership between countries in the Caribbean. The impacts of increased regional
activities and developments (e.g. citrus plantations and shrimp aquaculture in Belize; banana
plantations in Guatemala and Honduras) could potentially be detected by similar analysis
conducted for different periods. Here, it is premature to say that there is any long-term trend in
plume activity. A comparison between the year matrices using one way ANOVA showed that there
was no significant difference between the matrices (F=0.28, P=0.973) [what does this mean? No
difference between matrices => no trend or no interannual difference? I don’t get it]. For further
management in terms of MPA implementation, this research also provides a tool to understand
larval dispersal between reefs. The identification of “sources” of marine larvae and “sinks” is
critical for placement of marine reserves [Ogden, 1997]. Satellite ocean color data provide a
synoptic view of the connectivity patterns, which can be complemented by field data and
numerical models to facilitate management decision process. Given the fairly easy accessibility of
ocean color data compared to implementing a full modeling program well calibrated,
parameterized and validated, ocean color data should be considered for similar applications in
other regions.
5. Summary and Conclusion
A novel approach to study coral reef connectivity was presented here, where satellite ocean
color products from 1998 to 2006 were used to create a reef-to-reef and land-to-reef connectivity
matrix for the Mesoamerican Barrier Reef System (MBRS). The sources of more than 60% of all
the interactions that were counted in the connectivity matrix were from rivers off the Honduras
coast. During extreme events some of the estuarine plumes generated by rivers in Honduras
traveled as north as Cozumel. The Bay Islands were constantly impacted by river run-off from
mainland Honduras during the study period. Reefs and atolls in Belize were not exempt from
plumes coming out of Honduras. The southern part of the Belize barrier reefs was constantly
affected by the Ulúa River, which also frequently impacts Glovers Reef and more occasionally
Lighthouse Reef. The results of this research demonstrate a strong connectivity between Belize
and Honduras. Satellite ocean color time series provided a cost-effective insight of connectivity in
the MBRS. Future research on this topic should combine these results with field observations as
well as numerical models to improve management of the coastal marine ecosystems of this region.
Acknowledgments.
This work was supported by NASA Interdisciplinary Program grant NNG04F090G.
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µ
Cozumel
20°0'0"N
Chinchoro
18°0'0"N
BR3
BR2
TUR
LH
GLO
Guanaja
Roatan
Utila
BR1
R3
R1
R2
R4
16°0'0"N
R5
NIC
14°0'0"N
0 10 20
40
88°0'0"W
60
80
Nautical Miles
86°0'0"W
84°0'0"W
Figure 1: Map of the Meso-American Barrier Reef System (MBRS). Main reef formations are
shown in gray. The small boxes represent the 17 domains used in the connectivity calculation,
namely: [list them here, and spell out].
88W
86W
84W
88W
86W
84W
B
A
20N
18N
Week 15 (April 9 – 15)
C
Week 29 (July 16 – 22)
D
20N
18N
Week 31 (July 30 – August 5)
Week 46 (November 12 – 18)
Figure 2: Chl-a patterns off the MBRS from SeaWiFS weekly climatology [include color legend
here]. Regions with no data (e.g. clouds and land) were colored black [what about the white
color?]. Black lines denote “fronts” derived from the SEID algorithm. A. Typical dry season
conditions: few or no river plumes. B. River plumes coming out of R1 domain and reaching
Glovers and BR1, R2 reaching Utila, R4 reaching Guanaja, BR3 reaching Turneffe. [annotate each
region and reef site] C. River plumes from R1 and R2 Reaching Glovers and Light House, R1
reaching BR1, R2 reaching Utila, and R3 reaching Guanaja. D River plumes from R3 reaching
Guanaja and Roatan, R2 reaching Utila, R1 reaching BR1 and Glovers, BR3 reaching Turneffe,
connectivity between the Bay Islands, and betweenTurneffe and Glovers, also a slightly plume
leaving R4 is seen close to Chinchoro.
88W
86W
84W
A
88W
86W
84W
B
88W
86W
84W
C
20N
18N
April 2 – 8, 1999
D
November 12 – 18, 1998 December 3 – 9, 1998
E
F
20N
18N
January 1 – 7, 1998
G
April 9 – 15, 1998
H
March 12 – 18, 2001
I
20N
18N
February 12 –18, 2003
January 8 – 14, 2004
November 19 – 25, 2004
Figure 3: Weekly Chl-a patterns off the MBRS [include color legend here]. Regions with no data
(e.g. clouds and land) were colored black. (A) Typical dry season conditions: few or no river
plumes. (B) The river plumes in this image are caused by Hurricane Mitch [give date]: every reef
is affected by the plumes leaving Honduras and Belize, and connectivity between the Bay Islands
and the Belizean atolls is apparent. (C) One month after Mitch. (D) River plumes from R3,R4,R5,
and Nicaragua reached Chinchoro and Cozumel. There is connectivity between the Bay Islands,
between Roatan and Chinchoro, and between the Belizean atolls. (E) Connectivity between R4
and Chinchoro, R2 and Utila, and R3 and Guanaja. (F) R1 is reaching Glovers and Light House,
R3 is reaching Roatan and Guanaja, R2 is reaching Utila, and BR3 is reaching Turneffe. There is
connectivity between the Belizean atolls. (G) A plume leaving R3 and R4 is reaching Cozumel and
Chinchoro (there is connectivity between the two), and Roatan and Guanaja. R1 is reaching BR1,
and R1 combine with R2 are reaching Utila, Glovers, Light House and Turneffe. There is
connectivity between the atolls, and between the Bay Islands. (H) A plume leaving R3 and R4 is
reaching Cozumel, Roatan and Guanaja. There is connectivity between Chinchoro, Light House
and Turneffe, also between the Bay Islands. (I) A plume leaving R1 is reaching BR1, Glovers,
Light House, Turneffe, and Chinchoro, consequently this reefs are connected. Sediment coming
out of BR3 is seen reaching Turneffe. [lots of grammar errors – I leave this to Bruce or Frank]
Table 1: Connectivity matrix. The number represents the total number of weekly connections
between the 9 years study period. For example, a number of “4” means that for the 466 weekly
images in the 9 years there are four images that show connectivity.