AN ECOLOGICAL SURVEY OF A JAMAICAN MANGROVE SWAMP

AN ECOLOGICAL SURVEY
OF A JAMAICAN MANGROVE
SWAMP
Steven H. Vee
Rock Valley College
Rockford, Illinois

Introduction
A study was done on various aspects of a small mangrove swamp as a research
portion of a sabbatical leave in the fall of 1987. The work was done under the
direction of Dr. Eugene Kaplan, with some help from the author's daughter,
Annette Vee.
The site was chosen because of its convenient location, walking distance
from the Hofstra University Marine Lab Station. The site is visited by many
student groups.
While a field guide to the swamp has been written by Dr. Thomas
Byrnes, more information about the area will increase its value to all who
visit.
The physical aspects of the swamp were recorded, including its location,
climate of the area, salinity, water temperature, tidal fluctuations, prevailing
winds, and hurricane history.
A detailed mapping of the swamp was done. No previous maps of any detail
were in existence. The map in this study was used in the Byrnes' field guide to
the mangrove swamp. (Byrnes, 1987)
Much of the field research involved an estimation of the structural
parameters of the mangrove forest. Methods were used similar to those used by
Pool, Snedaker, and Lugo, (1977) and Curtis and McIntosh, (1951). Species
density per 0.1 ha, Basal area (m 2 /ha measured by diameter at breast height),
tree density (number/ha), stand height (meters), and species importance value
were determined for the swamp. By using methods similar to what other
researchers have used to study other mangrove swamps in the Caribbean,
comparisons can be made with a high degree of validity.
Many collecting field trips were made to the mangrove swamp. While many
other species were encountered, major attention was focused on animals of the
Phyla Cnidaria, Mollusca, Arthropoda (Class Crustacea), and Echinodermata.
Many

of the common members of these groups had previously been collected by Dr.
Byrnes, but a number of different species were found. This is meant to aid
future researchers in cataloging specimens, and also as an ongoing list which
can be added to.
It is hoped this paper will be used by instructors and students at the
Hofstra University Marine Lab who wish to study in detail the Reader's Point
Mangrove Swamp.

Literature Review
The mangrove swamp is an ecosystem which, while not being ignored, has
certainly not received the research attention it deserves. Despite the fact
that mangrove swampSdominate a)! estimated 75% of all coastline between 25 ° North
and 25 ° South latitude (Golley, Odum, and Wildon, 1962) and 25% of all Caribbean
coastline (Jones and Sefton, 1978), good, comprehensive ecological surveys are
notably lacking.
The difficulties encountered in the swamp, as well as prevailing
misconceptions may have accounted for the paucity of good research. The nearly
impenetrable nature of the red mangrove prop root system, biting ants, knee-deep
bottom ooze, anaerobic odors, pesky mosquitoes and the remote location from
major research facilities have thwarted most scientists.
Local myths have not promoted a positive attitude about mangrove swamps.
This researcher has heard local residents say such things as "mangrove where de
shark go durin de day" or "look out de alligator don't get ya".
Mangroves exist to some extent on almost all West Indian Islands. They
dominate protected shores such as the south coasts of Cuba, Puerto Rico and
Jamaica, especially where rivers bring down silt or where lagoons exist.
Patches of mangroves can be found in almost any area where protection from wave
action will allow siltation to occur. (Jones and Sefton, 1978). While the
mangrove swamp is technically limited to the forest area below the high tide
mark (sometimes called a "tidal forest") the mangrove can extend farther inland
(Lugo and Snedaker, 1974).
Most mangrove swamps are dominated by the red mangrove, Rhizophora mangle.
This species is the same world-wide, and is able to grow with its roots
completely immersed in salt water. With its extensive prop root system
supporting it, the tree promotes siltation by slowing wave action and water

currents. In this way, the red mangrove "walks out to sea", creating shallower
water in a complex succession story. Whether or not this is a true succession
story has been challenged by Egler, (1952), who found that in Florida mangroves
the increase in peat formation in the swamps just kept up with the increase in
sea level.
Behind the Rhizophora mangle, moving landward, is a zone containing the
black mangrove Avicennia germinans. Here it is not flooded with salt water
except at high spring tides, but the soil is extremely saline and low in oxygen.
(Lugo and Snekader, 1974). Special vertical pheumatophores on the root system
extend above the ground in a very characteristic pattern and allow the roots to
absorb oxygen from the air. As in the case with the Rhizophora, Avicennia can
excrete salt from its tissues. Salt crystals are characteristically found on
the surface of its leaves. (Bullard and Harrell, 1979)
Above the reach of high tide, yet still in a muddy, water-logged soil,
white mangroves, Laguncularia racemosa, can be found. Each species does its
part in consolidating the swamp sediments to render the conditions more suitable
for the next stage in the succession story. (Jones and Sefton, 1978).
On dryer land behind the true black and white mangrove zones is found the
gray mangrove or buttonwood, Conocarpus erectus, which is actually a terrestrial
species of the scrub forest and not a true mangrove. (Jones and Sefton, 1978).
In an actual mangrove swamp, such distinct red, black, white, and gray
zones cannot be clearly delineated. Warner (1968) describes five zones of a
Jamaican mangrove swamp beginning at the deep water of the lagoon.

First zone - "Fringe zone", 5% of the total swamp area,
characterized by open growth of pure stands of
Rhizophora.
Second zone - "Rhizophora zone", 20-25% of the total swamp
area, characterized by a tangled mesh of prop
roots of pure stands of Rhizophora.
Third zone - "Transition zone", 5-10% of the total swamp
area. Rhizophora dominates this zone, but it
is mixed with Avicennia and Laguncularia.
Fourth zone - "Laguncularia and Avicennia zone", 40% of the
swamp area.
One half of the trees here are
still Rhizophora but fully half of the trees
are Laguncularia or Avicennia.
Fifth zone - "Backzone", 15% of the swamp area. Dominated
by Laguncularia and Avicennia.
While it appears no two mangrove swamps are identical, Lugo and Snedaker,
(1974) have defined five different basic types:
Fringe mangrove forest - Found on edges of protected
shorelines and islands, they are best defined along
shorelines whose elevation are higher than the mean
tide line.
The coming and going of the tides is at a
slow velocity and the swamp traps most of the debris.
Riverine mangrove forest - This is an area that is flushed
by daily tides, but is separated from drainage by a
shallow berm.
The flooding river will wash out excess
salts and deliver nutrients to the swamp.

Overwash mangrove forest - This occurs on small, low islands
or cays and fingerlike projections of land. The tidal
flow overwashes it, as the name itself implies. Tidal
velocities are high, and most organic debris is removed
from the swamp.
Basin mangrove forest - This occurs in inland areas where
terrestrial runoff toward the coast is trapped by
drainage depressions and tidal water enters from the
sea.
Dwarf mangrove forest - Also called a "scrub mangrove
forest" by Pool, et. al. (1977) it is found on shallow,
flat coastal fringes. Although all four major species
of mangrove may be present, growth is stunted by high
salinity, and/or lack of nutrients so that the height
of the trees is less than 1.5 meters.
Rhizophora mangle dominates the fringe, overwash, and dwarf mangrove
forests. While it is also very prominent near the open water in riverine and
basin mangrove forests, the red mangrove co-dominates with Avicennia in these
swamps.
The fact that there are fewer than ten species of New World plants which
are halophytic (there are thirty-six in the Indo-West Pacific) which may be a
clue that life in the mangrove swamps is not easy. Plants which grow in high
saline environments transpire less than other plants. This is because the
transpiration process requires a lot of energy to work against the osmotic
gradient. If salinity increases, net productivity of the mangroves decreases.
If salinity is decreased too much competition with other plants becomes more
intense.
(Lugo and Snedaker, 1974).

Each species of mangrove is, as one might surmise, best suited to the
salinity of the zone in which it is predominantly found. Rhizophora
productivity declines with increasing salinity, while Avicennia and Laguncularia
productivity increase with increasing salinity. (Soto, et. al., 1982). The
white mangrove is more halophytic than the black mangrove. This corresponds
with the zones in which each predominates, as salinity increases shoreward away
from the open water. (Carter, 1973).
Canopy height can be used as a rough indicator of mangrove swamp
productivity. Riverine and basin mangrove exhibit greater canopy height than
dwarf, fringe, and overwash types. This ranking of productivity is consistent
with rankings done by leaf-litter-fall production studies. (Pool, et. al.,
1977)
Productivity of a swamp is determined by a complex interplay of many
different factors. The riverine and basin mangrove swamps receive enough
flushing from fresh water to keep salinities low enough to permit high
productivity. They are not flushed so much, however, that essential nutrients
are washed away (as occurs in the overwash mangrove). The freshwater will also
bring in nutrient-rich water from the land. (Pool, et. al., 1977)
The dwarf or scrub mangrove and fringe mangroves are less productive due to
high salinities from the lack of fresh-water flushing. The fringe mangrove,
however, is not subject to excessive wave action to carry away its nutrients
(Lugo and Snedaker, 1974), and ranks just below basin and riverine mangroves in
productivity. (Pool, et. al., 1977)
In the Caribbean, one generally expects a higher percentage of the
coastline on the protected south shores of is:Lands to have mangroves, but the
humid north coast mangrove swamps will be taller and more productive. (Pool et.
al., 1977)

Holdrige (1971) reported maximum canopy height of Rhizophora at 30 meters
+PUN F -
with a maximum diameter of 90 cm. Bullard and Harrell (1975) list heights of 18
meters for Avicennia and 10 meters for Laguncularia.
The mangrove serves a very important ecological function as a bridge
between the land and the sea. The swamp provides protection to the land during
storms, but it also helps the productivity of the surrounding sea. The
mangroves use the inorganic compounds of the land, and export organic compounds
to the sea. (Lugo and Snedaker, 1974) Odum and Heald (1979) showed the
connection between red mangrove detritus production and Florida sport fishing
with a classic ecological study. In Florida's Fahkahatchee and Fahka Union
Bays, Lugo and Snedaker (1974) estimated at least 57% and probably 80% of the
total energy budget was supported by exports from mangrove forests. They also
described the importance of crabs in breaking down mangrove leaves to eventually
make the organic matter available to other levels of the food chain.
An interesting study by John and Price (1979) noted a paucity of fleshy and
filamentous algae on rocks and coral hummocks in Antigua. Taylor et. al. (1986)
reported dominance of calcifying algae such as Halimeda on substrate-penetrating
roots of Rhizophora.
On "hanging" prop roots (those which did not touch the
bottom sediments), however, they found domination by fleshy algae such as
Acanthophora spic*fera, Caulerpa racemosa, and Spyrii"'dia filamentosa. Since
fleshy algae do not have to expend energy making a calcareous skeleton, their
productivity is higher, and they will dominate in a predator-free environment.
In both studies, the presence of urchin predators, notably Echinometra lucunter,
Diadema antillarum, Lytechinus variegatus, and Eucidaris tribuloides was causing
the less-easily predated calcareous algae to be favored over the more productive
fleshy algae. Only on hanging prop roots where these bottom-dwelling predators
could not reach them were fleshy algae dominant.

To measure productivity of a mangrove swamp, many different approaches can
be taken. Various exhaustive studies have involved collecting fallen leaves.
Holdredge et. al. (1971) devised a "complexity index" as an "expression of the
diversity and abundance within various types of forest communities." This index
was made from the product of the number of species in a study area, the number
of trees, the basal area, and the stand height. Using stand height alone as an
indicator of productivity may have some validity as Cintron et. al. (1975)
correlated decreasing stand height with increasing soil salinity. Odum (1970),
however, showed that mangroves recovering from hurricane damage will have high
productivity yet shorter canopy height.
Measuring basal area (diameter of trunks at breast height; DBH) can also be
done to determine productivity. Pool et. al. (1977) reported mangroves in
general to be not as productive (in basal area) as other forest ecosystems with
a low number of tree species, any or all of these methods can be used to compare
one mangrove swamp's productivity to others previously studied.
To report numerically the dominance of tree species in a forest, Curtis and
McIntosh (1951) developed a Species Importance Value. This is determined by a
summing of the relative percentages of basal area, density, and frequency for
each species.
Very few ecological surveys have been attempted which listed the species
found in a mangrove swamp. The most useful survey for the Readers Point
mangrove swamp is the HUML Field Guide by Dr. Thomas Byrnes (1987). Warner
(1969) did a good job with Jamaican mangrove crabs of the Port Royal area.
Barnwell (1986) reviewed the fiddler crabs of Jamaica, with emphasis on the
history of their classification.
Other studies have been done dealing with the
ecology of mangroves in other Caribbean islands, but they are less helpful.
Mangrove swamps around the world are threatened by a variety of forces.

Hurricanes are a natural way the swamps are destroyed. By absorbing the force
of such storms, mangroves help to protect shorelines from hurricane damage.
Some swamps are protected by their secluded location, but others will be
devasted by hurricanes. (Lugo and Snedaker, 1974)
Man, as is so often the case with other ecosystems, is the major threat to
mangrove swamps. The need for such products as tannin, construction timber and
charcoal, which can be obtained from mangroves, sometimes depletes the swamp
faster than it can grow. Far greater damage, however, is done by herbicides,
stream channelization and drainage.
Man's pressing desire for more land for
tourist developments, harbors, and agricultural land is rapidly depleting this
valuable resource. (Lugo and Snekader, 1974)

Methods and Materials
Complexity indexing which involves the major portion of the research data,
is a method which has been used to express diversity and abundance within
various forest ecosystems. Complexity indexes were obtained for a variety of
mangrove forests by Pool, Snedaker and Lugo (1977). Calculating this data for
the Reader's Point Mangrove Swamp allows a comparison with forests in other
parts of the Caribbean.
The complexity index was calculated both for trees over 10 cm in diameter
at breast height (DBH) and for trees under 10 cm DBH but over 2.5 cm DBH. The
index is the product of the number of species in the study plot (s), the stand
density (number of individual trees) (d), basal area in square meters (b),
height of the stand in meters (h), and 10 -3 .
Two plots were selected at random for analysis. Each plot was 12.5 meters
x 40 meters for a combined area of 1000 sq. meters or 0.1 hectare. Sites were
roped off and all stems measured and recorded. Chalk was used to mark the trees
to avoid counting any tree twice. In Rhizophora that were-developed, the
diameter was not measured at breast height, but rather at the point just above
the entry of the last prop root (in some cases this was 3-4 meters above water
level.)
Stand height was determined by formation of an isosceles triangle. No
inclinometer or Haga altimeter was available due to the remote location, so a
device was constructed to measure 45 0 angles. Distance from the tree trunk
where the tree top measured 45 0 from the plane of the ground was estimated to be
the stand height.
Species Importance Value was developed by Curtis and McIntosh (1951) to
show quantitatively the importance of various species in relation to each other
in a mixed stand of trees. It is calculated by averaging the relative
percentages of basal area, density, and frequency contributed by each species.

Mapping of the swamp was accomplished by :measuring (with string) as many
dimensions as possible and noting compass points with each measurement.
Comparisons were made with available local maps, but no maps of the area showed
the mangroves very precisely.
Collecting was done mostly by hand. Hand nets were used to probe the
bottom surface, and to sift through bottom sediments for crabs and mollusks.
Salinity was determined by use of a hydrometer and thermometer.
Measurement of the specific gravity of the water was then translated to salinity
by use of a standard conversion chart.

Site Description
The mangrove swamp studied shall be called the Reader's Point Mangrove
Swamp since no other name appears to exist. It is located on the north shore of
Jamaica about 1.5 miles southeast of the Hofstra University Marine Lab Station.
Its location at the southeast end of Prioy Bay gives it protection, by Lee Reef,
from high seas. It is also protected from the north-easterly trade winds by its
location behind Reader's Point.
North.
Jamaican climate is classified as tropical with a local latitude of 18 ° 26'
The temperature of the sea varies from 81 ° --F to 84 ° --F with the high
extreme being the case during the study period of September.
October and May are the wettest months of the year, while February and
March are the driest. The rainfall in Jamaica is highly variable across the
island. Charts show the St. Ann's Bay area, including the lab, to receive about
1500-2000 mm (60-80 inches) of rain per year. The local people seem skeptical
of that figure, citing recent changes in weather patterns bringing less rain.
Even at 2000 mm per year, for a north coast location, that is fairly dry.
While two small drainage ditches lead into the mangrove swamp, an influx of
fresh water occurs only after a heavy rain. During dry periods, there is no
flow into the swamp, and salinity levels are quite high. During September,
which is normally a wet month, salinity levels of 43 ppt were recorded after a
full week with no rain.
Tides all around Jamaica are very small. In Prioy Bay there are two high
tides and two low tides per day with the extremes from maximum spring high to
minimum spring low at 51 cm. Normal fluctuation is 20-30 mm. In the mangroves
the velocity of the tides is so slow that no flushing of detritus into the bay
occurs. After severe storms, a sulfur smell from the mangroves can be detected
at the marine lab, however.

The Reader's Point Mangrove Swamp should be classified as a fringe type.
It extends about 500 meters along the coast, and varies from about 5 meters to
50 meters in width. Determining the width depends upon how far inland one
defines swamp to extend. The tides are so small, and the bank elevation
increases so fast, that the horizontal distance on the shore from low-low tide
to high-high tide in most areas is five meters or less. Some white mangrove and
gray mangrove trees can be found at considerable distances form the high tide
mark, farther inland than Coccoloba and Acacia trees, in fact.
Defining the edge of the swamp to be just above the high tide mark, where
scrub forest species begin to appear, the Reader's Point Mangrove Swamp has an
area of about 1.2 hectares. It is bounded on one side by a refuse dump, and by
Reader's Point on the other. Its small size, while perhaps limiting the
diversity of species, makes it a manageable study area.
Allen.
In 1980, the north coast of Jamaica was severely damaged by Hurricane
Perhaps because of its protected location behind Reader's Point, no
obvious evidence of hurricane destruction was found. No large tree stumps or
fallen trees were present, although it is possible that in seven years, the
swamp could have recycled such vegetation. Judging from the size of many of the
Red Mangrove trees, however, it appeared most of the trees were pre-hurricane.

Structural Parameters
Results and Conclusions
The complexity index was calculated for both trees over 10 cm in diameter
at breast height (DBH) and for trees under 10 cm but over 2.5 cm DBH, because
Pool et. al. (1977) used this method. In this way, the Reader's Point Mangrove
Swamp can be compared with swamps in Florida, Puerto Rico, Mexico, and Costa
Rica for which similar data ha'ebeen published. The author feels a combined
complexity index, which would include all trees over 2.5 cm DBH would be much
more meaningful, but results are reported so they can be compared with
previously studied areas.
In the two study plots (whose combined area was 0.1 hectare) there were
three species of mangrove trees found, Rhizophora mangle (red), Laguncularia
racemosa (white), and Avicennia germinans (black). The fourth type, Conocarpus
erectus (grey or button) is prevalent in the driest zones of the swamp, but did
not happen to occur in the selected study plots. There were 101 red mangroves
measured over 10 cm DBH, and 38 between 2.5cm and 10 cm DBH. There were 8 white
mangroves measured over 10 cm DBH, and 3 between 2.5 cm and 10 cm DBH. Only one
black mangrove over 10 cm DBH and one over 2.5 cm but under 10 cm DBH were found
in the plots.
The basal area for all. trees over 10 cm DBH was 2.524 m 2 per 0.1 hectare,
or 25.24 m 2 per hectare (See table A). For trees over 2.5 cm but under 10 DBH,
the basal area was 0.158 m2 per 0.1 hectare or 1.58m 2 per hectare (See table B).
One meaningful measure of the productivity of a forest, which Pool et. al.
(1977) failed to report, is the total basal area. For the Reader's Point
Mangrove Swamp there is a total basal area of 26.82m 2 /ha.
Stand height was measured at 14 meters. Many trees in both plots exceeded
12 meters in height. This was slightly higher than reported values for other
fringe mangrove swamps. (See Reprint 112, "figure 11")

The complexity index for trees greater than 2.5 cm DBH but under 10 cm DBH
was 2.8. For those trees greater than 10 cm DBH the complexity index was 11.6
(See table D). These numbers can be compared with values obtained by Pool et.
al. (1977) (See reprint #1, "Table 2"). The same researchers reported a mean
complexity index of 4.8 (for DBH>10 cm) for all mangrove forests in tropical dry
life zones. For tropical moist life zones, an index of 72.0 was reported
(Reprint #2 "Table 5").
The author was not as certain of the validity of complexity indexing at the
end of the study as anticipated. The index varies dramatically from study area
to study area. In the Reader's Point Mangrove Swamp three species were found,
but only one black mangrove was counted. Had that one tree not been in the
study area, the complexity index would be 33% lower than reported. In a scrub
mangrove swamp, where no trees over 2.5 cm can be found, the complexity index
for trees over 10 cm DBH must be zero. A formula to replace the present method
should be devised.
The complexity index for the Reader's Point Mangrove Swamp fell within the
wide range of figures reported in "Table 2". The basal area which may give a
better indication of the productivity of the swamp, was very similar to other
fringe mangroves. The figures reported for basin-type mangrove swamps varied
widely, but riverine-type swamps were much higher in basal area.
Riverine mangrove swamps have two major advantages over the fringe type
found at Reader's Point. Salt concentrations, which will decrease the
productivity, are not allowed to build through evaporation, as there is a
constant addition of fresh water. Mineral nutrients from the land are also
continually being added to the riverine swamp at a faster rate than occurs in
the fringe-type swamp.

The Reader's Point Mangrove Swamp is not in a truly moist tropical zone,
yet its rainfall is near the high end of the dry tropical zone designation (See
Reprint #2, "figure 12"). The data reported for complexity index and basal area
fall within expected values.
Another interesting aspect of the data collected is the calculating of
importance value. The summing of basal area, density and frequency for each
tree species of the Reader's Point Mangrove Swamp shows a strong dominance of
Rhizophora mangle (91.9%), :followed by Laguncularia racemosa (7.0%), and
Avicennia germinans (1.1%) (See table C). The dominance of red mangrove is
typical of a fringe mangrove swamp because of the small intertidal zone where
the other mangrove species can co-exist. The short distance from a niche which
is nearly constantly immersed to that which never receives tidal wash also
explains why white mangroves, which are better suited to dry land than black
mangroves, are dominant over blacks.
Species Encountered
A mangrove swamp offers a wide variety of physical conditions within its
broad boundaries. These varied microenvironments make many niches available for
numerous, vastly different species to occupy. In a fringe-type mangrove swamp
such as found at Reader's Point, this is strikingly apparent because of the
compaction of the zones. In a distance of as little as 5-10 meters, the
environment changes from terrestrial to intertidal, to sub-tidal.
In the Phylum Cnidaria, two Scyphozoans were found in the open water near
Rhizophora. Carybdea alata (sea wasp) was seen rarely during the day, in small
schools near open, silty bottoms. Cassiopeia xamachana (upside-down jellyfish)
was consistently found on the bottom in 2-4 feet of water.

Although no corals were present, a small number of species of class
Anthozoa had large populations. The anemone Anthopleura krebsi (rock anemone)
was the most numerous, coating many of the Rhizophora prop roots. Searches for
Aiptasia tagetes revealed none on prop roots. On the muddy bottom near prop
roots numerous Phyllactis flosculifera (collared sand anemone) were found,
especially in shallow water.. In the open water, under clumps of Halimeda were
many Bartholomea annulata (ringed anemone) with only their characteristic
tentacles exposed.
Heteractis luc 4a was not found, which leaves only supposition to explain
the stinging experienced by scientists. B. annulata was not capable of stinging
this investigator, but something on the blades of Halimeda and Thalassia was. A
possible answer may be nematocysts drifting in from elsewhere, or possibly
unseen hydrozoans on the vegetation. H. luc +a may also be present, but not
i~ , ~~~w s aa,~,v~~-+vt tl=
" . 5 rN~irNq au '=irvLE A~ , ec, gv~~~at~~,~s,
collected. Y
C,rrCi~IiQN$IS,~ S - fi~'r- 4 ,'4rArs~ 52 .t,~i fvc CAI VI -i # ~( t1 C-f obsc*Yrr'S.
The mollusks found in the mangroves were mainly Gastropods, but some
bivalves were encountered. Isognomon alata (flat tree oyster) can be easily
located on Rhizophora prop roots, stacked like pancakes just above or just below
the water level near the low tide level. Arcopagia fausta (faust's tellin), a
dead shell commonly found around octopus dens in other parts of the bay, was
found alive in the mud of the open water. The only other bivalve found was the
diminutive Tellina exilis (pink-thin tellin), from the mud near Rhizophora prop
roots.
Of the Gastropods, many were extremely abundant and easily found.
Littorina angulifera (angulate periwinkle) common on Rhizophora prop roots, just
above water level. Neritina virginea (virgin nerite), Cerithium littoratum,
Batillaria minima (false cerith), and Cerithium variabile (dwarf cerith) which
looks much like Batillaria minima, was found by the hundreds on blades of
Halodule grass in very shallow water. The virgin nerite is interesting to look
at under a dissecting microscope because of the ornate patterns and the fact
+hn+ r,n +w,,n ehnllc coom to lnnk alike.

Also common were the pulmonate snails on the leaf litter above the tide
level. Melampus coffeus (coffee melampus) and Melampus monile (yellowish
melampus)were in mixed groups, and nearly indistinguishable.
Encountered less often were the voracious Fasciolaria tulipa (true tulip)
and cerithium algicola (middle-spined cerith). The dead shells of the former
were many times seen occupied by the striped hermit crab, Clibanarius vittatus.
The same crab was found in shells of Tonna maculosa (Partridge tun), although
live specimens of this allusive snail were not collected.
The spotted sea hare, Aplysis dactylomela, was either quite numerous, or
not present at all. Migration in and out of the mangrove swamp may be linked to
moon cycles for this beautiful gastropod.
Other dead shells collected were Thais haemastoma floridana, Murex
antillarum, Codakia orbicularis, and Asaphis deflorata. Whether these were
present live or were washed in is not known. Three specimens of a small
polished white snail, probably of the Pyramidellidae family were found near and
inside the anus of a Holothuria mexicana sea cucumber.
The Phylum Arthropoda was well represented by the numerous ants,
butterflies, termites and spiders, but no effort was made to collect these.
Collection was confined to the class Crustacea, with concentration on the
Brachyuran crabs.
Since many crustaceans are either detritus feeders or scavengers, they are
very numerous in the mangrove swamp with its abundant leaf-litter. De La Cruz
and Banaag (1967) reported crabs to be the dominant faunal inhabitants of
Philippine mangroves.
Probably the most numerous crab was the mangrove tree crab, Aratus pisonii,
found mostly on the seaward edge of the swamp. This beautifully colored crab
has the interesting behavior of hiding on the side of Rhizophora prop roots

opposite the observer. Seemingly scarce at first, this crab appears everywhere
once one knows where to look. This researcher found as many as five on one prop
root!
Another group of crabs found near the seaward side of the mangrove swamp
was the Callinectes crabs. Although difficult to tell apart, Callinectes
sapidus, Callinectes exasperatus, and CQllinectes danae were probably all
present.
Microphyrys bicornutus (decorator crab) was also common in the subtidal
areas. This crab was occasionally collected from the inside of clothing, as it
seems to like crawling up pant legs. A small crab found in muddy bottom areas
throughout the swamp was difficult to classify. It was a Xanthid crab,
probably Actae sp.
Some of the most interesting crabs found were the fiddler crabs, named for
the males "fiddle and bow" claws. Barnwell (1986) reported historic collections
of eight species of Uca in Jamaican waters. Uca thayeri, Uca rapax, Uca
leptodactyla, Uca major, Uca burgersi (formerly called Uca mordax (Holthuis,
1967), Uca cumulanta, Uca spinicarpa, and Uca heterochelos have all been
reported, but the last two are extremely rare. In one small area near Reader's
Point, five species (U. thayeri, U. rapax, U. leptodactyla, U. major, and U.
burgersi) were easily collected. The smallest, U. leptodactyla, was the most
numerous. (Vee, 1987)
The hermit crabs found most often were Clibanarius tricolor (red, white and
blue hermit crab) on shore, and Clibanarious vittatus (striped hermit crab) in
the water. Immature Coenobita clypeatus were also found as hermit crabs, while
the adults were encountered farther from the high tide mark.
In the leaf litter above the high-tide mark, Sesarma curacoensis and
Sesarma ricordi were found, but they were not as numerous as Pachygrapsus

gracilis. Goniopsis cruentata (mangrove crab) with the beautiful red legs was
surprisingly plentiful, especially among the roots of mangroves stumps where
trees had been cleared.
Many Cardisoma guanhum:i (Great Land Crab) could be seen any night, but
unlike the fiddler crabs, they are most active during high tide. Far less
numerous, but occupying similar large holes, Ucides cordatus was also found. In
drier areas, Gecarcinus ruricola was collected.
Mantis shrimp, Gonodactylus oerstedi, were common, and probably occupy a
majority of the holes seen on the open bottom areas.
Synalpheus brevicarpus
shrimps could be heard in most shallow areas at night. Living among the dense
epiphytes and epizoites of the Rhizophora prop roots, an, occasional pair of
banded shrimp, Stenopus hispip dus could be seen. Only immature Panulirus argus
were found. Lysmata wurdemanni shrimps were also found in collections made with
a fine-mesh net.
Phylum Echinodermata was not well represented in the species collected.
Only four species were found, but all were quite common.
Synaptula hydriformis,
called "green snot sea cucumber" by Byrnes (1987) was the most numerous species,
being found in heavy densities on the Rhizophora prop roots.
Also extremely
common was the Donkey Dung Sea Cucumber, Holothuria mexicana, which occupies
open areas of the swamp. Mixed in with Holothuria mexi(ana was the five-toothed
sea cucumber, Actinopygja agassizii, many times housing a resident pearl fish in
the digestive tract. In small groups scattered at the base of Rhizophora prop
roots were smaller, yellow-footed sea cucumbers, Holothuria rg isea.
All Echinoderms found were in the class Holothuroidea, no representative of
the other four classes was encountered. The paucity of other Echinoderms,
especially of the class Echinodea was a surprise. The abundance of algae and
grasses on which to feed should support a good population of the common sea eggs

or other urchins. These species are not commonly used for food in the area.
Except for an occasional fisherman, few natives venture into the mangrove swamp,
so overcollecting of any species is not a problem. The lack of urchins probably
accounted for the variety of fleshy and calcaerous algae observed on Rhizophora
prop roots. No domination by predator-resistent calcereous algae was observed.

Summary
The small mangrove swamp at Reader's Point turned out to be a very
interesting area for ecological study. It is a fringe-type mangrove swamp of
about 1.2 hectare size, with typical heavy domination by Rhizophora mangle
trees.
All four species of mangrove were well-represented in their classic
zones, and a healthy scrub forest ecosystem exists behind the swamp.
The productivity of the swamp as measured by basal area of the trees, stand
height, and complexity is within an expected range for similar fringe-mangrove
swamps.
Lack of higher productivity is probably due to lack of nutrients from
the location away from streams, and seasonal high salinity from lack of regular
fresh-water flushing.
A good variety of species was encountered, a sign of good ecological health
of the swamp. The surprising number of different crab species and populations
of each was of special interest. The lack of non-Holothuroidean Echinoderms
remains a mystery.
It is hoped this study can be followed up by periodic checks on the growth
in area of the swamp, and increases in basal area and stand height. The lists
of species encountered can also be used by future student groups or researchers
as a starting point for further collections.

Phylum: Cnidaria
Class: Scyphozoa
Carybdea alata
Cassiopea xamachana
Class: Anthozoa
Phylum: Mollusca
Phyllactis flosculifera
Anthopleura krebsi
Bartholomea annulata
Class: Bivalva
Arcopagia fausta
Tellina exilis
Isognomon alata
Codakia orbicularis (dead)
Asaphis deflorata (dead)
Class: Gastropoda
Fasciolaria tulina
Cerithium algicola
Cerithium variabile
Batillaria minima
Neritina virginea
Littorina angulifera
Tonna maculosa (dead)
Aplysis dactylomela
Melampus coffeus
Melampus monile
Species Encountered
Thais haemastoma floridana (dead)
Cerithium littoratum
Murex antillarum (dead)
Pyramidellidian snail (probably Mellanella sp.)

Phylum: Arthropoda
Class: Crustacea
Clibanarius tricolor
Clibanarius vittatus
Aratus pisonii
Goniopsis cruentata
Cardisoma ug anhum
Ucides cordatus
Callinectes sapidus
Callinectes exasperatus
Callinectes danae
Microphyrus bicornutus
Sesarma curacoensis
Sesarma ricordi
Pachygrapsus gracilis
Coenobita clypeatus
Actae sc.
Gecarcinus ruricola
Gonodactylus oerstedi
Synalpheus brevicarpus
Stenopus hispidus
Panulirus argus
Lysmata wurdemann:
Uca thayeri
Uca burgersi
Uca rapax
Uca leptodactyla
Uca major
Phylum: Echinodermata
Class: Holothuroidea
Holothuris grisea
Synaptula hydriformis
Actinopygia agassizii
Holothuria mexicana

Table A
Diameter and Basal Area of All Trees over 10cm
[combined Data, Plots 1 and 2 (total = 0.1 hectare)]
Rhizopora> 10 cm (101 trees)
Diameter Area (TT R ) Diameter Area Diameter Area
19cm 283cm 23 415 22 380
18 254 13 133 11 95
14 154 23 415 11 95
11 95 14 154 17 227
13 133 26 531 14 154
15 177 11 95 14 154
13 133 15 177 11 95
22 380 20 314 11 95
20 314 15 177 10 79
14 154 10 79
14 154 11 95 Total area 23,298cm 2
14 154 11 95
10 79 17 227 Laguncularia> 10cm (8 trees)
12 113 26 531 Diameter Area 2
26 531 11 95
24cm 452cm
12 113 27 572 17 227
16 201 23 415 15 177
13 133 15 177 12 113
26 531 22 380 14 154
22 380 14 154 14 154
13 133 12 113 15 177
16 201 15 177 15 177
17 227 10 79
12 113 10 79 Total area 1,631cm 2
15 177 11 95
18 254 18 254 Avicennia > 10cm (1 tree)
21 346 17 227 Diameter Area 2
13 133 10 79
20cm 314cm
10 79 10 79
18 254 14 154
13 133 21 346 Total Basal Area
11 95 11 95 Rhizophora 23,298cm 2
19 283 15 177 Laguncularia 1,631
13 133 19 283 Avicennia 314
25 491 15 177
16 201 27 572 25,243cm 2
27 572 17 227
31 754 28 615 = 2.524 m 2 /0.lha
16 201 11 95 = 25.24 m 2 /ha
10 79 28 615
16 201 20 314
23 415 19 283
12 113 23 415
11 95 15 177
16 201 11 95
14 154 18 254
12
113

Table B
Diameter and Basal Area of All Trees between 2.5 cm and 10 cm
[combined data plots 1 and 2, (total = 0.1 hectare)]
Rhizophora >2.5cm < 10 2cm. (38 trees) Laguncularia >2.5cm < 10 cm. (3 trees)
Diameter Area (TTR ) Diameter Area
5cm 20cm 2
7 cm
2
38cm
6 28 9 64
7 38 7 38
6 28
9 64
2
Total Area = 140cm
5 20
5 20
7 38
5 20
9 64 Avicennia >2.5cm < 10 cm. (1 tree)
6 28 Diameter Area2 7 38 7cm 38cm
7 38
9 64
7 38
6 28
7 38
9 64
8 50 Total Basal Area
9 64 Rhizophora 1402cm 2
6 28 Laguncularia 140
8 50 Avicennia 38
4 13
5 20 1580cm 2
8 50
6 28 = . 158 m2 /0.lha
8 50 = 1.58 m2 /ha
4 13
4 13 Combined Basal Area
5 20 Table A 2.524 m2/0.1 ha
6 28 Table B . 158 m /0.1 ha
7 38
8 50
5 20 Grand total for all trees 2.682 m2/0.1 ha
4 13 or 26.82 m /ha
9 64
9 64
8 50
Total Area = 1402 cm 2

Table D
Table C
Importance Values
Tree Species Basal Area Density Frequency Importance Value
Rhizophora mangle 92.3% 91.8% 91.5% 91.9%
Laguncularia racemosa 6.5% 7.3% 7.2% 7.0%
Avicennia germinans 1.2% 0.9% 1.3% 1.1%
Complexity Index
Number of Number of Trees Basal area m 2 /O.lha Stand Complexity
Species >2.5cm10cm >2.5cm10cm height (m) Index
>2.5cm10cm
3 4.2 110 . 158 2.52 14 . 28 11.6

TABLE 2. Structural comparisons of mangrove forests of southern Florida, Puerto Rico, Mexico, and Costa Rica. Complexity components are expressed on a 0.1
ha basis.
Number
SITE classification) c s e species
>2.5 mDBH> 10DBH
(m 2 )
>2.5 mDBH> $ c )
Stand
height
( m)
Complexity i c h
>2.5 cm DBH >10 m DBH'
Florida, U.S.A.
Ten Thousand Islands
Plots 3-7, 3-8 (overwash) 2 180 60 1.50 1.10 6.3 3.4 0.8
Plots 5-11, 5-12, 5-13 (fringe) 2 280 80 2.35 1.24 7.3 9.6 1.4
Plots 6-14, 6-15 (riverine) 2 400 60 3.85 2.17 9.0 27.7 2.3
Rookery Bay (basin) 3 590 66 2.03 1.44 6.5 23.4 1.9
Turkey Point (scrub) 1 2503 0 0.60 0.00 1.0 1.5 0.0
Puerto Rico
Pifiones I (basin) 3 197 57 1.58 0.37 14.0 13.1 0.9
Pifiones II (basin) 3 321 46 1.69 0.56 11.5 18.7 0.9
Pifiones III (basin) 3 138 68 1.69 1.55 16.0 11.2 5.1
Pifiones IV (basin) 3 285 81 2.16 0.96 13.0 24.0 3.0
Vacia Talega (riverine) 3 189 98 2.09 1.71 13.0 15.4 6.5
Ceiba (fringe) 2 569 26 1.67 0.34 8.5 16.2 0.2
Morn Island (basin)% 2 293 179 3.50 2.97 15.0 30.8 15.9
Aguirre (fringe) 3 367 111 2.26 1.39 12.0 29.9 5.6
Jobos Bayb
Plots 1-6 (overwash) 3(1)e 1165 26 1.55 0.32 4.8 26.0 0.0d
Plots 7-11 (fringe) 2 2059 0 1.44 0.00 4.4 26.1 0.0
Plots 12-35 (fringe) 3(2)e 4733 17 1.43 0.17 4.8 97.5 0.0d
Ptsnta Gorda (fringe) 1 178 26 0.69 0.31 7.0 0.9 0.0d
Mexico
Roblitos (riverine) 2 224 91 2.96 2.41 8.0 10.6 3.5
'-- (riv
1°Ia * i- s s -
Pall - 11a weririe) 3 23u 145 6.08 5.59 17.0 73.2 41.3
Isla Roscell (overwash) 3 148 91 2.85 2.62 8.0 10.1 5.7
El Cal6n (basin) 2 312 61 1.52 0.83 9.0 8.5 09
Rio de las Canas (riverine) 3 179 103 5.78 5.61 16.0 49.7 27.7
Costa Rica
Moin (riverine)e 4 137 118 9.64 9.53 16.0 84.5 72.0
Boca Barranca (riverine)t 3 110 66 3.29 3.18 9.5 10.3 6.0
Santa Rosa (fringe) 2 105 80 2.32 2.22 10.0 4.9 3.6
'Data from Rogers and Cintr6n 1974.
b Data from the Natural History Society of Puerto Rico 1972.
'Only one and two species respectively were recorded in stem diameter class greater than 10 cm.
d Complexity indices calculated were less than 0.1.
Measured red, black and white mangroves and Pterocarpus officinalis.
r Measured red and black mangroves and Pelliciere rhizophorae.

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