Restoration of gorgonian (soft coral) populations by Puerto Rico Sea Grant

PROJECT BACKGROUND

AND RELEVANCE

Gorgonians (soft corals) are common in many shallow-water areas throughout the Caribbean (Bayer 1961). Although gorgonians and hard corals (scleractinians) usually co-occur on rocky substrates in coral reef ecosystems, the relative abundance of these taxa may differ considerably. Scleractinians are often the visually dominant organisms in topographically complex areas (e.g. Goreau 1959) whereas gorgonians generally predominate in low relief “hard ground” habitats (Goldberg, 1973, Kinzie 1973, Opresko 1973, Muzik 1982, Lasker and coffroth 1983, Jordan 1989, Yoshioka 1989). The hard ground biotope is prevalent in many areas of the Caribbean. For example, recent sidescan sonar surveys have revealed that the areal coverage of gorgonian versus scleractinian-dominated reefs are roughly equal in La Parguera on the southwest coast of Puerto Rico (M. Prada, pers. comm.). Given their high abundances and areal extent of their associated habitat, it is reasonable to presume that gorgonians play an important role in the ecology of Caribbean coastal systems. For example, the gorgonian biotope serves as an important nursery area for ecologically and commercially important fish and invertebrate populations (Lindeman and Synder 1999). In addition, because of their aesthetic impact on human observers, gorgonians undoubtedly represent an important marine resource for the recreational tourist industry.

Along with scleractinians and other sessile coral reef organisms, gorgonians are confronted by a variety of natural and anthropogenic threats. A fungal disease, Aspergillosis is currently affecting populations of the sea fan, Gorgonia spp. (Smith et al. 1996, Nagelkerken et al. 1997a,b) and possible another gorgonian, the sea plume Pseudopterogorgia spp. (G.W. Smith, pers. comm.). The widely reported bleachings of scleractinians in recent years also affects some gorgonian taxa, especially the slit pore sea rod Plexaurella spp. (Williams and BunkleyWilliams 1990). Hurricanes can also have devastating effects on gorgonian and other coral reef organisms (Stoddart 1962, Woodley et al. 1981, Yoshioka and Yoshioka 1987, Rogers et al. 1991). Finally, gorgonians can be impacted by ship groundings and pollution.

Especially troubling with respect to natural and anthropogenic disturbances are indications that gorgonian populations do not recover quickly after such events. For instance, no recolonization of gorgonians was noted at a study site located off Caja de Muertos (near Ponce, Puerto Rico) several years after the passage of Hurricane David in 1979 (Yoshioka and Yoshioka

1987). Also, at the present time (2006) gorgonians have not repopulated experimental quadrats cleared on gorgonians in 1987 (Yoshioka 1996). As detailed below, the recovery of gorgonian populations following disturbances is probably slow because gorgonians are “recruitmentlimited”. This study investigates the efficacy of restoring gorgonian populations by using transplantations of colony branches to bypass this bottleneck in gorgonian populations.

Finally, although not directly related to the goals of this project, results may be relevant to the mariculture of gorgonians and related taxa for the “live rock” aquarium industry or for the jewelry trade (e.g. the black coral Antipathes spp. in the Caribbean). For example, as with the shallow-water gorgonians, Grigg (1988) concluded that populations of the precious deep-water Pacific gorgonian Corallium spp. are also recruitment-limited.

Essential features of this project were based on a long-term monitoring program on gorgonians. We have monitored about 15,000 colonies since 1983 to elucidate various aspects of the ecology of gorgonians (spatial pattern, demography, population dynamics, etc.) at two sites near La Parguera on the southwest coast of Puerto Rico (Yoshioka and Yoshioka 1989a, 1991; Yoshioka 1994, 1996, 1997a, 2000). The reasons why results of the monitoring study were important for the present project are discussed below. I also discuss the relevance of the research results with respect to life history theory and “natural background” features.

Life History Strategy and Population Dynamics of Gorgonians

Along with scleractinians, sponges and other sessile organisms of Caribbean coral reef systems, gorgonians are long-lived and have high reproductive potentials. This combination of life history traits represents a major exception to the theory of “r-K selection” (Pianka 1970). Instead these life history traits conform to the “bet-hedging” interpretation (Stearns 1976) of life history pattern. In brief, bet-hedging is often characterized by high and constant survivorships of adults (large colonies) and low and variable reproductive success (i.e. recruitment and recruit colony survivorships). In terms of natural selection, long life and repeated reproduction would be a strategy to cope with uncertain reproductive success. In turn, reproductive success is variable in some (but not all) cases because of “recruitment-limitation” (Hubbell 2001). In such instances, recruitment is the “bottleneck” limiting population sizes. Depending on the specific factors responsible for recruitment-limitation, the recovery of populations may be slow or rapid following disturbances.

Our long-term monitoring studies indicate that recruitment of gorgonians is limited by an extrinsic factor, colony smothering by bedload (sediment transport). In turn, because the deleterious effects of bedload are restricted to short (recruit) colonies, these results indicated that transplantations of colony branches would bypass this population bottleneck. Further evidence supporting this contention is given below.

Ecology of Large (Adult) Gorgonian Colonies

Consistent with the bet-hedging scenario, survivorships of large (>10 cm tall) colonies were high and constant, averaging about 92% per year with year to year deviations generally within the range of random variations (Yoshioka and Yoshioka 1991). In concordance with theoretical results of Murphy (1968), a simple population model indicated that the gorgonian populations at the study sites could persist for >50 years even if recruitment is completely unsuccessful (Yoshioka 1998). The high survival of large colonial organisms in coral reef systems is attributed to a “refuge in size” from many potential sources of mortality by Jackson (1977) among others. For example, predation usually results in complete mortality for small gorgonians, but only in “partial mortality” of large colonies (Harvell and Suchanek 1987).

Similarly, partial mortality in the form of branch breakage did not have a statistically detectable effect on large colony mortalities (Yoshioka and Yoshioka 1991). This result indicates that branch transplants would not adversely affect the survival of donor colonies.

Causal factors responsible for albeit low mortalities of large colonies (8% per year) provide additional support for transplantation as a restoration strategy. Harvell et al (1993) and others found that biological interactions such as competition and predation play minor roles in large colony mortalities because gorgonians are chemically defended and are fed on by only a few species (the fire worm Hermodice carunculata and the mollusk Cyphoma gibbosum).

Despite intensive efforts, Yoshioka and Yoshioka (1989a) found no indications that competition for substrate space among gorgonians was a source of colony mortalities. Competitive interactions are limited to overgrowth by other taxa as algae, sponges such as Desmapsamma anchorata (McLean 2006) and the hydrocoral Millepora spp (Wahle 1980). However, competitive overgrowth by other taxa only accounted for about 10% of large colony mortalities at our study sites (Yoshioka and Yoshioka 1991).

Instead of competition and predation, various studies suggest that physical factors responsible for basal fracture and detachment are the major sources of large colony mortalities (Birkeland 1974, Wahle 1985, Yoshioka and Yoshioka 1991). Wahle (1985) also notes that detachment was primarily due to the failure of the substratum rather than the colony holdfast itself. In other words, detachment results from the structural weakness of the underlying substrate rather than the attachment of the colony to the substrate. These observations suggested that survivorships could equal or even surpass natural levels if attachments of transplants to the substrate could be strengthened by appropriate techniques. Similarly, basal fracture could be decreased if the axial skeleton near the transplant base is strengthened and protected from damage.

Gorgonian Recruitment: sexual reproduction

Various features of gorgonian recruitment provide further support for transplantation as a restoration strategy. One of the more prominent aspects of a long-term monitoring program was a 7.5 fold increase in gorgonian colony densities (8 to 60 colonies/m2) resulting from a relatively short period (1984-85) of episodic recruitment when populations were not recruitment-limited (Yoshioka 1998). During this period semi-annual recruitment rates peaked at about 45 colonies/m2 compared to about 5 colonies/m2 at other times.

A detailed examination of the dynamics of recruit colonies provided valuable insights into causal factors responsible for recruitment-limitation of gorgonian populations. A “key factor” analysis (Varley 1973) indicated that variations in recruitment reflected variations in the survival of newly settled planula larvae, rather than the “supply” of larvae available for settlement (Yoshioka 1997b). In other words, recruitment-limitation in gorgonians is largely attributable to post-settlement factors rather pre-settlement factors related to reproduction and larval abundance.

The preceding results also indicate that factors affecting post-settlement survivorships underlie the ability of gorgonian populations to recover quickly by sexual reproduction following natural or anthropogenic disturbances. Recovery may be rapid (< 1 generation) if competition with adult gorgonians (or other sessile organisms) is responsible for post-settlement mortalities. An example of this scenario is the California redwood trees where competition from adult trees

prevents the successful survival of seedlings (Murphy 1968). Alternatively, recovery may be slow and unpredictable if juvenile survival is controlled by extrinsic “weather” factors, as is the case for parasitic tapeworms (Murphy 1968).

Analogous to the situation with tapeworms, field observations and experiments indicate that natural recovery of gorgonian populations are slow because survival of newly-settled gorgonians is controlled by extrinsic environmental conditions rather than competitive interactions among colonies. For example, virtually no recovery of gorgonian populations were noted for at least 3 years following the passage of Hurricane David at a site on the south coast of Puerto Rico in 1979 (Yoshioka and Yoshioka 1987). Similarly, little recovery has been observed for nearly 20 years in experimental quadrats that were cleared of colonies in 1987 (e.g. Yoshioka 1996). Moreover, significantly higher recruitment occurred in uncleared control quadrats (probably because of gregarious settling behavior) indicating the presence of an inverse density dependent effect (i.e. the Allee effect). The inverse density dependent survival of newly-settled colonies would tend to prevent the recovery from low population densities, as may be the case of some exploited fish populations (Myers et al 1995).

Size-specific survivorship patterns of recruit colonies provided valuable insights into the causal factors underlying recruitment-limitation of gorgonian populations. Survivorships of recruit gorgonians increase with increasing colony height (Yoshioka 1994). For instance, average annual survivorships of 1, 2, 3, 4 and 6 cm tall Pseudopterogorgia recruits were 17%, 84%, 85%, 88% and 90% respectively. In addition, recruit survivals varied significantly among gorgonian species. However, these species-specific patterns were largely attributable to differences in growth rates with faster (taller) growing taxa having higher survivorships than slower growing groups. For example, Pseudopterogorgia, Eunicea laxispica, and Plexaurella grow at rates of about 5, 3 and 1 cm per yr, respectively. Correspondingly, about 50%, 20% and 3% of their recruits survive till the age of 5 years respectively (Yoshioka 2001). Thus, these results indicate that the causal factor underlying recruitment-limitation is closely associated with colony heights. Moreover, the high survivorship of adult (>10cm tall) colonies indicates that the causal factor only affects short colonies.

Additional observations provide several clues about the identity of the height-specific factor responsible for recruitment-limitation. Mortality from various species including the urchin Diadema antillarum (Sammarco 1980), the fire worm Hermodice carunculata, and the mollusc

Cyphoma is undoubtedly size-specific because predator damage is more likely to cause whole colony mortality with smaller colonies (e.g. Harvell and Suchanek, 1987). Certainly, the period of episodic recruitment from 1984-85 is related to decreased grazing pressure due to the mass mortality of Diadema in January 1984 (Yoshioka 1996). However, grazing by Diadema is not a satisfactory explanation because gorgonian recruitment became limiting after 1986 in the continued absence of Diadema. Nor can other predators be responsible for low recruitment because no increase in activities of Hermodice or other predators were evident during this period. The preceding results suggest that competition and predation are not responsible for recruitment-limitation of gorgonian populations. Alternatively, other indications implicate bedload (sediment transport) as the causal mechanism. Variations in bedload are apparently an indirect effect of the disappearance of Diadema (Yoshioka 1996). In conjunction with its grazing activities, Diadema produces ‘clean’, easily transportable sediments that can smother short (but not tall) colonies. Visual observations indicated that most of the Diadema-produced sediments were transported away from the study sites soon after its mass mortality. Sediments that remained were largely consolidated and immobilized by microflora (Ruyter van Stevenick and Bak 1986). Thus, in addition to the decreased grazing effects of Diadema, low bedload levels due to the decreased production and increased consolidation of sediments was responsible for the absence of recruitment-limitation in 1984-85. Field observations indicated that the consequent buildup of consolidated sediments was again responsible for recruitment limitation after 1986. These results and considerations implicate bedload as the primary agent responsible for recruitment limitation in gorgonians. Because the effects of bedload is highly height-specific, these results also indicate that the population bottleneck in gorgonians can be bypassed by transplantations of large gorgonian branches.

Gorgonian recruitment: asexual fragmentation

Many colonial organisms in coral reefs also reproduce by asexual reproduction. However, unlike many branching (ramose) scleractinians (e.g. Knowlton et al. 1981) reproduction by fragmentation is relatively uncommon among shallow-water gorgonians of the Caribbean. Of the approximately 30 species at our study site, recruitment by fragmentation is essentially limited to 3 taxa; and undescribed Eunicea species, Pterogorgia anceps and Briareum asbestinum (unpublished data). In general these gorgonians have colony branches that lie

prostrate to the bottom substrate that serve as “runners” to form new upright (vertical) branches. The runners eventually die, severing the physiological connection between the parent colony and its asexual fragment.

Fragmentation by branch breakage commonly occurs among many gorgonian species. However, these branches eventually die unless the branch becomes securely wedged in a crevice in an upright position (pers. obs.). This situation has occurred only a few (<10) times over a long-term monitoring study. The best-studied example of asexual recruitment by fragmentation among gorgonians is of Plexaura kuna by Lasker (1984, 1990). P. kuna is apparently very rare in Puerto Rico (Coffroth and Lasker, pers. com.) and is evidently “programmed” for asexual reproduction by fragmentation because its axial skeleton is structurally weak at the branch node, and therefore prone to breakage (Lasker 1984). More importantly, survivorships of P. kuna branchs have a similar height-specific pattern as sexual recruits. For example, short (<10 cm) fragments have a relatively low survivorship (54% per year) compared to long branches (95% per year, Lasker 1990). Thus, as with sexual reproduction, these features of asexual recruitment also indicate that gorgonian populations can be successfully restored by transplantations of large branches.

METHODS

Study Site

The study site (17o56.2’ N, 67o3.2’ W) was located in a hardground habitat near Media Reef on the southwest coast of Puerto Rico. As with many other hardground habitats, the study site has low topographic relief, and the macroinvertebrate biota is visually dominated by gorgonians. Substrate cover by sponges, corals and other sessile fauna is low (<10%). Also, similar to most hardground areas on the south coast of Puerto Rico, the study is fully exposed to wave action generated by the tradewinds and other and other climatic factors. This environmental feature of hardground areas is especially relevant to the results of this study because water motion is the primary underlying cause of large colony mortalities. (Alternatively, results of this study must be interpreted with caution with respect to protected habitats (e.g. the backreef zone).

Field Methods

The primary goal of this study was to develop simple and time/cost effective methods of branch transplants. Because detachment and basal fracture are the major sources of large colony mortalities, the field procedures focused on methods to (i) securing transplants to the substrate, and (ii) preventing damage/fracture of axial skeletons. Several procedures were used to secure transplants. In most cases holes were chiseled or drilled into the substrate and the axial skeletons of branches were secured with underwater epoxy or cement. The proximal end of branches were stripped of live tissue so that the epoxy/cement was in direct contact with the axial skeleton.

Plastic collars were placed around the lower 2 cm of half of the transplants to assess whether this procedure would prevent injury to transplant bases by rocks and other transported objects. In some cases, branchs were fastened with electrical cable ties to nails pounded into the substrate.

Transplant branches were collected from colonies in the immediate area, and were about ~20 cm long based on a baseline study (Yoshioka and Yoshioka 1991) that colonies of this size enjoyed a refuge in size from mortality. Transplants were placed about 25 cm apart along prepositioned 5 m long transects. Effects of the spatial arrangement of transplants on survivorships were not examined because previous results indicated that interactions among colonies have no effect on mortalities (Yoshioka 1997a). Although previous studies also indicated no statistical differences in large colony survival among species, we tested for possible taxa-specific differences, we tested for species-specific effects by transplanting two species Plexaura flexuosa and Pseudoplexaura spp. These species were chosen because they are both abundant in the study site but differ in colony morphologies. Plexaura flexuosa colonies are highly branched and stiff, while Pseudoplexaura spp colonies are more flexible with long terminal branches.

Because natural survivorship rates of large colonies are low (>90% per year) a potential problem in the statistical detection of differences in survivorships are small numbers of transplant mortalities. For this reason, much of the field effort involved transplantations of the largest number of branches logistically feasible. Thus, in general, sample sizes of each constraint examined exceeded 50 transplants.

Field observations generally occurred at semi-annual intervals and concentrated mostly on transplant mortalities. Because mortalities of large natural colonies were often preceded by damage to the colony base (Yoshioka and Yoshioka 1991), we also paid close attention to the bases of the transplants. Also, heights of transplants were measured to assess effects of transplantation on growth rates. Finally, because axial fracture was hypothesized to be a major

source of transplant mortalities the diameters of the axial skeleton 15 cm from the branch tips were measured as an index of the mechanical strength of the transplants.

Data analyses

Terminology used to describe life history features (demography) was used summarize transplant survivals. Overall transplant survivals were expressed as lx, the age-specific survivorship which represents the proportion of the original population surviving to age x. For this study x was defined as the post-transplant age rather than the age of the donor colony. However, because branches were transplanted at various times during the study, all transplants could not be observed for equal periods of time. For this reason, lx was constructed using annual survivals, or 1.0- qx, where qx is age-specific death rate, or the proportion of the transplants alive at the beginning of time period x that die during period x. Statistical analyses of survivorships employed Chi-Square tests because surviving transplants involve discrete data (e.g. numbers of transplants).

Estimates of growth rates were based only on colonies surviving until the end of the study. However, because unequal periods of observations were involved, growth data was standardized to annual rates (cm/y) for statistical analyses. Also, because colony heights are measurements and because distributions of growth rates were generally non-normal with unequal variances, nonparametric procedures were used for statistical analyses.

RESULTS

Survivorships: Epoxied/Cemented transplants

No difference was detected on the effects of underwater epoxy versus cement on the survival (and growth) of transplants so the epoxy and cement data were pooled for all analyses presented below. A prominent aspect of the results was a significantly higher detachments (X2 = 46.6, p<0.005, df =1) for Pseudoplexaura (34%) compared to Plexaura flexuosa (6%) in the initial observations following epoxy/cement transplantations (Table 1). In addition, differences in detachment between collared/uncollared transplants were not significant for P. flexuosa (X2 = 0.08, p>0.50, df =1), whereas significantly higher detachments occurred for uncollared

Pseudoplexaura transplants (X2 = 19.7, p<0.005, df =1). Initial detachments are probably a methodological ‘artifact’ due to movement of the transplants from water motion during the hardening period of the epoxy/cement. In turn, differences between Pseudoplexaura and P. flexuosa are probably due to differences in the colony morphologies of these taxa as discussed below.

After discounting initial detachment as a methodological artifact, survivorships of Pseudoplexaura and Plexaura flexuosa transplants displayed several similarities and dissimilarities with natural colonies. Age-specific survivorships 2 years after transplantation (l2) was about 34% and 84% for Pseudoplexaura and Plexaura flexuosa respectively (Table 2), or annual survival rates of 57.9% and 91.5% respectively. The latter rate is essentially equivalent to an average annual rate of 91.9% obtained for natural colonies of all species at the study site. Not surprisingly however, survivorships were significantly lower for Pseudoplexaura compared to Plexaura flexuosa (e.g. X2 = 47.7, p<0.005, df =1, for l1 of transplants).

Examinations of the inferred sources of mortality revealed that the lower survivorships of Pseudoplexaura are largely attributable to likelihoods of axial fracture being 3.5 times more frequent than Plexaura flexuosa (X2 = 66.3, p<0.005, df =1, Table 3). In essentially all cases of mortality due to this factor, fracture occurred immediately above the junction of the epoxy/cement (and nails) to the axial skeleton. (Axial fractures above the junction were classified as nonlethal injuries and were analyzed in terms of transplant growth.)

Survivorships: Effects of Nails

In contrast to the epoxied/cemented transplants, initial detachment was not a major factor affecting the fate of transplants fastened to nails pounded into the substrate. Only a few of these transplants suffered initial detachment (Plexaura flexuosa: 2 ex 50; Pseudoplexaura: 0 ex 50).

Compared to the epoxy/cement treatments, detachment rates were significantly lower for Pseudoplexaura (X2 = 19.5, p<0.005, df =1). The lower detachment rates were not significant for P. flexuosa (X2 = 0.67, p<0.005, df =1).

The nail treatment resulted in low mortalities of P. flexuosa transplants during the first year of observation (1 ex 48 transplants) that was not significantly different for this species with

the epoxy/cement treatments (X2 = 0.06, p<0.005, df =1). Unfortunately, the nail treatments resulted in high mortalities from axial fracture (36 ex 50 transplants) for Pseudoplexaura that was significantly higher for this species with the epoxy/cement treatments (X2 = 21.0, p<0.005, df =1). In other words, for Pseudoplexaura there was a tradeoff between greater rates of initial detachment and lower rates of axial fracture with the epoxy/cement treatments and vice versa for the nail treatment.

Survivorships: Effects of Axial Skeleton Diameters

Differences in the diameters of the axial skeletons apparently underlie the higher rates of initial detachment and skeletal fracture for Pseudoplexaura compared to Plexaura flexuosa. Median diameters of axial skeletons measured 15 cm below the distal end of branches were 2.1 and 1.4 mm for Plexaura flexuosa and Pseudoplexaura respectively (n = 15 branches each). This difference is highly significantly (p<0.01, Rank-Sum Test). Because adherence to epoxy/cement and mechanical strength of the axial skeleton depends on the surface and cross sectional areas of the axial skeleton respectively, the adherence and ability to resist fracture would be proportional to the square of diameters. Thus as a first approximation, the ability of Plexaura flexuosa to resist detachment and fracture is about 2.25 times great than Pseudoplexaura. This mechanism is also consistent with the nail treatments because greater support for attachment probability resulted in greater drag forces on transplant branches. Unlike Plexaura flexuosa, the axial skeleton of Pseudoplexaura is apparently unable to withstand such drag forces.

Growth Rates

No significant within taxa differences was evident in growth rates among transplant treatments (e.g. epoxy/cement/nails) so treatment data were pooled for comparisons between Pseudoplexaura (n = 56) and Plexaura flexuosa (n=210). The median growth rates of Plexaura flexuosa (1.04 cm/y) were significantly greater than Pseudoplexaura (0.28 cm/y, Rank Sum Test, z = 2.1, p<0.05)). In addition, these growth rates were considerably lower than median rates observed for natural colonies at the study site (Plexaura flexuosa: 1.42 cm/y; Pseudoplexaura: 2.81 cm/y). Also, as with natural colonies growth rates were highly variable within taxa (Plexaura flexuosa - range: -17.2 to +6.8 cm/y; Pseudoplexaura - range: -17.0 to +5.4 cm/y).

(Negative growth rates are also common for natural colonies and reflect branch breakage rather than shrinkage.)

DISCUSSION

The results of this study indicate that branch transplants are a feasible strategy for the restoration of gorgonian populations in rocky areas experiencing relatively high levels of water motion. As demonstrated with Plexaura flexuosa, survivorships of transplants can be high (>90%/y) and essentially equivalent to natural colonies under these conditions. However, as indicated by Pseudoplexaura, improvement of transplant techniques may be warranted for some taxa. In the case of Pseudoplexaura, detachment and fracture of the axial skeleton due to drag forces associated with water motion are the major obstacles to successful transplantations. The low survivals of Pseudoplexaura transplants unexpected because natural colonies of equivalent heights (~20 cm) have survivorship rates similar to Plexaura flexuosa. Apparently natural Pseudoplexaura colonies are able to adapt drag forces while growing but transplanted branches are not.

Comparisons of Plexaura flexuosa and Pseudoplexaura also indicated that the size (diameter) of the axial skeleton is a key factor affecting the success of transplants. For transplants ~20 cm in length, the diameter of the axial skeleton of Plexaura flexuosa is about 1.5 times thicker than Pseudoplexaura. The consequent ability to withstand drag forces would be proportional to the cross sectional area of the axial skeleton and the adherence of the axial skeleton to epoxy/cement would be proportional to surface areas. Thus, as a first approximation the ability to withstand drag and adhere to epoxy/cement is 2.25 times greater for Plexaura flexuosa. Other factors affecting drag such as the chemical composition of the axial skeleton (Jeyasuria and Lewis 1987) and overall colony morphology (Vogel 1994) may also be involved. In retrospect, differences in the ability of Pseudoplexaura and Plexaura flexuosa to withstand drag can be inferred from the appearance of colonies in the field. Terminal branches of Plexaura flexuosa are generally short and are upright while terminal branches of Pseudoplexaura are generally long and droop downwards. Apparently different mechanical strategies are involved; Plexaura flexuosa resists drag forces directly while Pseudoplexaura flexes to decrease

drag. Thus, the immobilization of Pseudoplexaura branches in the transplant treatment increased probabilities of axial fracture.

These inferences indicate that survivals of Pseudoplexaura transplants can be greatly improved by using longer branches (which have thicker axial skeletons) that are trimmed at the distal ends (to reduce drag). (It should be noted that, although the underlying reasons differ, trimming is a strategy often employed in transplanting trees.) To be sure, trimming incurs a physiological shock to transplants but based on natural colonies as well as the transplants, this deleterious effect has no detectable effect on survivorships. In any event, growth rates indicate that, as with many terrestrial plants, transplantation in itself has sublethal effects.

Finally, from a more general perspective, the results of this study indicate that with respect to drag forces, the development of species-specific transplant techniques for gorgonians should involve examinations of the biomechanics of gorgonians including properties of the axial skeleton and other aspects of colony morphology.

LIST OF REFERENCES

Bayer, F.M. 1961. The shallow-water octocorallia of the West Indian region. Nijhoff, The Hague.

Birkeland, C. 1974. The effect of wave action on the population dynamics of Gorgonai ventlina Linnaeus. Stud. Trop. Oceanogr. 12:115-126.

Fisher, R.A. 1963. Statisticl methods for research workers. Oliver and Boyd, Ltd., Edinburgh.

Goldberg, W.M. 1973. The ecology of the coral-octocoral communities of the southeast Florida coast: geomorphology, species composition and zonation. Bull. Mar. Sci. 23:465-488.

Goreau, T.F. 1959. The ecology of Jamaican reefs. I. Species composition and zonation. Ecology 40:67-90.

Grigg, R.W. 1988. Recruitment limitation of a deep benthic hard-bottom octocoral population in the Hawaiian Islands. Mar. Ecol. Prog. Ser. 45:121-126.

Harvell, C.D. and T.H. Suchenek. 1987. Partial predation on tropical gorgonians by Cyphoma gibbosum (Gastropoda). Mar. Ecol. Prog. Ser. 38:37-44.

Harvell, C.D., W. Fenical, V. Roussis, J.L. Ruesink, C.M. Griggs, and C.M. Greene. 1993. Local and geographic variation in the defensive chemistry of a West Indian gorgonian coral Briareum asbestinum. Mar. Ecol. Prog. Ser. 93:165-173.

Hubbell, S.P. 2001. The unified theory of biodiversity and biogeography. Princeton University Press. Princeton, New Jersey.

Hudson, J.H. and W.B. Goodwin. 1997. Restoration and growth rate of hurricane damaged pillar coral (Dendrogyra cyclindricus) in the Key largo National Marine Sanctuary, Florida. 8th I.C.R.S. 1:567-570.

Jackson, J.B.C. 1977. Competition on marine hard substrata: the adaptive significance of solitary and colonial strategies. Am. Nat. 111:743-767.

Jeyasuria, P. and J.C. Lewis. 1987. Mechanical properties of the axial skeleton in gorgonians. Coral Reefs 5:213-219.

Jordan, E. 1989. Gorgonian community structure and reef zonation patterns on Yucatan coral reefs. Bull. Mar. Sci. 45:678-696.

Kinzie III, R.A. 1973. The zonation of West Indian gorgonians. Bull. Mar. Sci. 23:93-155.

Knowlton, N., J.C. Lang, M.C. Rooney, and P.A. Clifford. 1981. Evidence for delayed mortality in hurricane damaged Jamaican staghorn corals. Nature 294: 251-252.

Lasker, H.R. 1984. Asexual reproduction, fragmentation and skeletal morphology of a plexaurid gorgonian. Mar . Ecol. Prog. Ser. 19: 261-268.

Lasker, H.R. 1990. Clonal propagation and population dynamics of a gorgonian coral. Ecology 71: 1578-1589.

Lasker, H.R. and M.A. Coffroth. 1983. Octocoral distributions at Carrie Bow Key, Belize. Mar. Ecol. Prog. Ser. 13;21-28.

Lindeman, K.C. and D.B. Synder. 1999. Nearshore hardbottom fishes of southeast Florida and effects of habitat burial caused by dredging. Fish. Bull. U.S. 97:508-525.

McLean, E.L. 2006. Ecology of the encrusting sponge Desmapsamma anchorata. MS thesis, University of Puerto Rico, Mayaguez.

Murphy, G.I. 1968. Pattern in life history and the environment. Am. Nat. 102:390-404.

Muzik, K. 1982. Octocorallia (Cnidaria) from Carrie Bow Key, Belize. In: Rutzler, K. and I.G. McIntire (eds.) The Atlantic barrier reef system at Carrie Bow Key, Belize I. Structure and communities. Smithson. Contrib. Mar. Sci. 12: 309-316.

Myers, R.A., N.J. Barrowman, J.A. Hutchins, and A.A. Rosenburg. 1995. Population dynamics of exploited fish stocks at low population levels. Science 269: 1106-1108.

Nagelkerken, I., K. Buchman, G.W. Smith, K. Bonair, P. Bush, J. Garzon-Ferreira, L. Botero, P. Gayle, C.D. Harvell, C. Heberer, K. Kim, C. Petrovic, L. Pors, and P. M. Yoshioka. 1997a. Widespread disease in Caribbean sea fans I.Patterns of infection and tissue loss. Mar. Ecol. Prog. Ser. 160: 255-263.

Nagelkerken, I., K. Buchman, G.w. Smith, K. Bonair, P. Bush, J. Garzon-Ferreira, L. Botero, P. Gayle, C. Heberer, C. Petrovic, L. Pors, and P. M. Yoshioka. 1997b. Widespread disease in Caribbean sea fans II. Spreading and general characteristics. 8th I.C.R.S. 1: 679-682.

Opresko, D.M. 1973. Abundance and distribution of shallow-water gorgonians in the area of Miami, Florida. Bull. Mar. Sci. 23:535-558.

Pianka, E.R. 1970. On r and K selection. Am. Nat. 104:592-597.

Rogers, C.S., C.N. McLain, and C.R. Tobias. 1991. Effects of Hurricane Hugo (1989) on a coral reef in St. Johns, USVI. Mar. Ecol. Prog. Ser. 78. 189-199.

Ruyter van Stevenick, E.D. and R.P.M. Bak. 1986. Changes in abundance of coral reef bottom components related to mass mortality of the sea urchin Diadema antillarum. Mar. Ecol. Prog. Ser. 34: 87-94.

Sammarco, P.W. 1980. Diadema and its relationship to coral spat mortaltiy: grazing, competition and biological disturbance. J. Exp. Mar. Biopl. Ecol. 45: 245-272.

Smith, G.W., L. Ives, I. Nagelkerken, and K.B. Ritchie, 1996. Caribbean sea fan mortalities. Nature 383: 487.

Stearns, S.C. 1976. Life history tactics: a review of the ideas. Quart. Rev. Biol. 51: 3-47.

Stoddart, D.R. 1962. Catastrophic storm effects on the British Honduras reefs and cays. Nature 196: 512-515.

Varley, G.C., G.R. Gradwell, and M.P. Hassell. 1973. Insect pop[ulation ecology. Blackwell Scientific Publications. London.

Vogel, S. 1994. Life in moving fluids. Princeton University Press. Princeton, New Jersey.

Wahle, C.M. 1980. Detection, pursuit and overgrowth of tropical gorgonians by milleporid hydrocorals; Perseus and Medusa revisited. Science 209: 689-691.

Wahle, C.M. 1985. Habitat-related patterns of injury and mortality among Jamaican gorgonians. Bull Mar. Sci. 37: 905-927.

Williams, E.H. Jr. and L. Bunkley Williams. 1990. The world-wide coral reef bleaching cycle and related sources of coral mortality. Atoll Res. Bull. 335: 1-71.

Woodley, J.D., E.A. Chornesky, A.A. Clifford, J.B.C. Jackson, L.S. Kaufman, N. Knowlton, J.C. Lang, M.P. Pearson, J.W. Porter, M.C. Rooney, K.W. Rylaarsdom, V.J. Tunnicliffe, C.M. Wahle, J.L. Wulff, A.S.G. Curtis, M.D. Dallmeyer, B.P. Jupp, M.A.R. Koehl, J. Niefel, and E.M. Sides. 1981. Hurricane Allen’s impact on Jamaican coral reefs. Science 214: 749-755.

Yoshioka, P.M. 1994. Size-specific life history pattern of a shallow-water gorgonian. J. Exp. Mar. Biol. Ecol. 184: 111-122.

Yoshioka, P.M. 1996. Variable recruitment and its effects on the population and community structure of shallow-water gorgonians. Bull. Mar. Sci. 59: 433-443.

Yoshioka, P.M. 1997a. A community-level analysis of spatial mortality patterns. J. Exp. Mar. Biol. Ecol. 214: 167-178.

Yoshioka, P.M. 1997b. Are variations in gorgonian recruitment determined by “pre-settlement” or “post-settlemnnt” processes? 8th I,C.R.S. 2: 1175-1178.

Yoshioka, P.M. 1998. Are large colonies a “key factor” in the dynamics of gorgonian populations? Rev. Biol. Trop. 46 (supl. 5):137-143.

Yoshioka, P.M. 2000. The biotic neighborhoods of shallow-water gorgonians of Puerto Rico. Bull. Mar. Sci. 76: 625-636.

Yoshioka, P.M. 2001. Why “hard grounds” are not coral reefs. Assoc. Mar. Lab. Carib., la Paguera (Abstract)

Yoshioka, P.M. and B.B. Yoshioka. 1987. Variable effects of Hurricane David on the shallowwater gorgonians of Puerto Rico. Bull. Mar. Sci. 40: 132-144.

Yoshioka, P.M. and B.B. Yoshioka. 1989a. A multispecies, multiscale analysis of spatial patterns and its application to a shallow-water gorgonian community. Mar. Ecol. Prog. Ser. 54: 257264.

Yoshioka, P.M. and B.B. Yoshioka. 1989b. Effects of water motion, topographic relief and sediment transport on the distribution of shallow-water gorgonians of Puerto Rico. Coral Reefs 8: 145-152.

Yoshioka, P.M. and B.B. Yoshioka. 1991. A comparison of the survivorship and growth of shallow-water gorgonian species of Puerto Rico. Mar. Ecol. Prog. Ser. 69: 253-260.

Table 1. Effects of collared/non-collared transplants on the initial detachment of Plexaura flexuosa and Pseudoplexaura spp.

Plexaura flexuosa Detached Not Detached

X2 (1 df) = 0.13, NS

Pseudoplexaura spp. Detached Not Detached

X2 (1 df) = 19.2, p<0.005

Table 2. Transplant survivals of Plexaura flexuosa and Pseudoplexaura lx = Age-specific survivorships; qx = age-specific death rates; n = # transplants; and n/a = not applicable.

Plexaura flexuosa

Table 3. Numbers of colonies suffering mortality from axial fracture and other sources (excluding initial detachment).

Pseudoplexaura