Assessment of Coral Reef Damage in Aqaba, Jordan
Oct 15th to 31st 2000
Pierre MADL (Salzburg - AUT);
Ines LEMMBERGER; Andreas ROETZER
(both Vienna - AUT);
This years course focused on three main topics. At first it was tried
to evaluate the Diver Carrying Capacity at the dives sites in front
of the Royal Diving Center (RDC) according to an index based key
Coral Damage Index (CDI). This index revealed that divers in the
first 10m and snorkelers in the first 4m do contribute to a certain degree to the deterioration
of that contour reef, thus greatly reducing the yearly allowance of dives per year.
The gulf of Aqaba presents itself as a deep basin, which is limited by the flat shelf in the north and the submarine swell (which drops sharply into the Red Sea to 1423m depth) in the south. As the RDC is located some 10km south of Aqaba and 3km north of the Saudi Border, the gulf there extends already to depths of 500m and is approximately 7km wide.
The meteorological data from the middle and south end of the Red Sea
reveal a complete periodical and seasonal wind-system change. In winter the north to east wind
prevails while a south to west wind dominates over the summer months (Wahbeh and Hulings, 1987).
The hydrographic conditions of the gulf are highly dependent on its
topographical shape. The only 170m deep swell in the south (Street of Tiran) limits the water
exchange between the gulf and the main basin of the Red Sea.
Up until year 1965 the Jordanian share of the gulf coast was limited to
a short stretch of only 11km length. In connection with the development of the port of Aqaba,
the border has been pushed some 14km south and now runs 6 km north of Haql in Saudi Arabia.
A phosphate-loading facility which belongs to the port of Aqaba is situated close to the Saudi
border in near vicinity to the RDC.
Our study site:
|Currently, the south coast of Aqaba is designated as an area in which large scale development is being planned. Fun-parks, extensive accommodation facilities and other infrastructural requirements may soon cover the sandy and rocky desert south of the city. Already at this stage, the Jordan authorities have completed a 4-lane road project that paves the way for the following construction phases (fig. 1.1). It could well be that these projects will undergo major revision as more evidence is emerging that such activities might exert detrimental effects on the reef ecosystem.|
Fig. 1.1 The section south of Aqaba, depicting the future developments and the sites visited during this year's survey.
Purpose of the Field Study:
The Royal Diving Center (RDC) is a small but dynamic facility that was built to boost scuba diving activities in Jordan. We used the RDC to survey dive-related impacts on a small scale. About 8000 divers visit the RDC annually, with probably 3 to 4 times that many snorklers (A. Qatawneh, RDC managing director; pers. comm.). These figures strongly suggest that coral damage should be monitored. Breakage of corals by humans is one of the most common causes of coral decay especially within the upper 10m depth range of popular reef sites. Branching corals of the genus Acropora, Millepora and Stylophora are the most frequently affected genera.
In order to quantify such damages it is necessary to design appropriate monitoring programs that respect both scientific and management guidelines. This includes a practicable method to quickly asses the conditions of the reef ecosystems and the extent of potential environmental threats. According to sites Riegl and Velimirov (1991), one approach to evaluate to bulk impact of recreational activity can be expressed by the Diver Carrying Capacities (DCC). It is defined as the number of divers per site per year and is a measure of the number of divers a reef can tolerate without becoming significantly degraded. It plays an important role in the management of physical damage on a coral reef.
Up to now, DCCs have rarely been considered by planners and developers.
There is a need to provide background knowledge and understanding about these fragile ecosystems,
and to support reef managers with this powerful tool for both sustainable development and management.
Finally, we attempted to apply the Revised Rapid Assessment Program (RRAP, Ginsburg 2000) to a short stretch of the reef off the RDC. The RRAP provides accurate data regarding coral species richness, bioerosive activity by echinoderms, and the epifaunal presence of marine algae. As it requires a profound knowledge about coral taxonomy, the RRAP is a very complex and time-consuming procedure.
Coral Damage Index (CDI):
Fig 2.1 Underwater sign language used for a rapid CDI procedure.
All transects were measured at intervals of 5 cm and the categories were expressed as percent coverage in reference to every 10 m transect. CDI in the broken and damaged category are based on the overall coral coverage of each transect (excluding the sandy substrate). As soft corals were not censused in our survey, we classed them as inaccessible substrate (with regard to potential hard substrate for coral settlement) and grouped them into the substrate category.
In accordance to Riegl and Velimorov (1991), we summarised the data into the following two main classes:
In our survey, the least affected site, which has been visually determined (was relatively untouched by divers during the two week course) was then used to obtain reference data (transect #5 at 4m depth and transect #1 at 8m depth). Fortunately, divers accessing the reef off the RDC use the 35m jetty; therefore, boat traffic and anchoring were not recorded at all (boat traffic in the area was negligible).
In-Situ Identification of coral species: It should be the aim of any naturalist and scientist to encourage in situ identification of corals wherever possible. This had been an impossible task before the advent of SCUBA diving and underwater photography, and even with these aids several problems remain. The major one is that corals are still classified principally based on skeletal features. Some of these are obscured by living tissues and others are so small as to be difficult to distinguish underwater. This difficulty can either be overcome by carrying a magnifying lens or by removing a small portion of the colony for examination on land. This should be done with great care in order to minimize damage, and never in protected areas where collecting restrictions apply. Many genera are distinct and can be readily recognized from good photographs. Others are more edifficult, and thus it is advisable to combine photographs with detailed notes. As corals are extremely "plastic" organisms - even a single species is capable of showing great morphological variations - it takes several minutes to complete this exercise, and as time under water is limited, it is essential to be suitably prepared before entering the water.
What to record:
Coral Diseases (CD):
As it proved to be difficult to relocate sites monitored in 1999, we agreed it would be helpful to generate a more accurate map that not only lists major diseases affecting particular colonies but also depicts geographical data regarding depth, inter-coral distances, and angular orientation with regard to fixed reference points (both above and under water). With the help of a 30 m measurement tape, a compass and a depth gauge, we were able to generate a map that should greatly simplify finding those sites in future field courses.
Revised Rapid Assessment Protocol (RRAP):
Algal abundance was recorded at 2 m intervals (i.e. at 1, 3, 5, 7, and 9 m) on both
sides of the transect line using a grid measuring 20 cm per side. Both the percentage of algal coverage
and the approximate height of algae each quadrate were recorded.
Fig. 2.2 Photo Nr.6 (of 23)1 displaying a short section of the RRAP-transect. Centered section shows Gap "D" (all other photos are listed under this web-address.
Coral Damage Index (CDI):
The category "sand" was the only one with a higher standard deviation (16.59) at 8m
and therefore a higher variability than at 4m (5.28). All other categories were more inhomogeneous at the 4m
The coral rubble at 4m average 12.5 %, thus being higher than 7.8 % at 8m. The rubble
indices at 4 m range from 4 % to 24 %, whereas at the 8m level they range from 4 to 11 %. In any case the
measured values were significantly higher than those gained from pristine reefs (Riegl and Velimirov, 1991).
The coral rubble distribution at 8m was the most even of all categories, having a standard deviation of only
Coral Diseases (CD):
Tab. 3.1 Cross-reference of the investigated sites ("used buoys"; refer to the markers used during the survey, whereas "permanent buoys"; were placed for future surveys).
Fig 3.5 MAP portraying the research area of the coral disease survey.
|Used buoy||Index on film||perm. buoy||Genus|
|32||1, 2||K9||Astreopora sp.|
|A-alpha||4, 5||buoy A alphaK9||Astreopora sp.|
|MY2||6||buoy MY2||Goniopora sp.|
|TC||7, 8, 9||no marker||large Acropora sp.|
|P8||11, 13||next 2||Coscinaraea sp.|
|F2'||12, 14||2||Plesiatrea versipora|
|new BBD||16||K2||Coscinaraea sp.|
|F2||17, 18, 19, 20||K2||Plesiatrea versipora|
|P1b||21||K7||Plesiatrea sp. or Echinopora sp.|
|F6||22, 23||K4||Coscinaraea monile|
|< Pocillo||24||no marker||Pocillopora verrucosa|
|Astrep||28, 29||K6||Astreopora sp.|
|R||-||no marker||large Platygyra lamellina|
The listed corals belong to the following families Acroporidae, Poritidae, Siderastreidae and Faviidae. Branching corals seem to be less affected by diseases.
A brief selection of decaying corals showing black-band disease (BBD) and tissue bleaching (TBL):
Fig.3.6 Site 36: Coscinaraea sp. with BBD (192kB)
Fig.3.7 Site F: slowly degrading Plesiastrea sp. and dead Acropora sp. (ex-TBL) (205kB)
Fig.3.8 Site F2: Plesiastrea sp. with BBD (190kB)
Rubble of Styllophora sp.
Fig.3.9 Site MY2: Goniopora sp. with TBL (210kB)
Fig.3.10 Site P10: dead Coscinaraea sp. (195kB)
Fig.3.11 Site P8: unhealthy Coscinaraea sp. showing endolithic activity by Cliona sp (290kB)
Fig.3.12 Site TC: Acropora sp>. probably suffering from WBD (205kB)
Rapid Reef Assessment Program (RRAP):
Tab. 3.2 Detailed list of coral species and their dimensions
|Picture-#||Genus (bandwidth of 15cm within shadow of transect line)||Height [cm]||Width [cm]|
|1, 2||Softy (brown)||-||-|
|1, 2||Echinopora gemmacea||9||8|
|1, 2||Sarcophyton sp. (?yellow)||-||-|
|1, 2||Goniopora sp.||-||-|
|1, 2||Montipora sp.||15||43|
|4, 5||Favia sp.||3||5|
|4, 5||Favia sp.||4||6|
|4, 5||Turbinaria mesenterina||3||18|
|4, 5||Fungia sp.||3||11|
|4, 5||Porites sp.||16||24|
|4, 5||Acropora sp.||7||7|
|4, 5||Favia sp.||9||19|
|4, 5, 6||Coscinaraea sp.||15||15|
|5, 6||Favia sp.||8||10|
|5, 6||Montipora sp.||7||16|
|5, 6||Sarcophyton sp.||-||-|
|n. v.||Pocillopora sp.||6||8|
|6, 7||Sarcophyton sp.||-||-|
|6, 7||Acropora sp.||15||58|
|6, 8||Fungia sp.||7||14|
|7, 8||Montipora sp.||7||14|
|7, 8, 9||Favia sp.||13||21|
|7, 8, 9||? Favia sp.||13||21|
|7, 8, 9||Pocillopora sp.||15||16|
|7, 8, 9||Cyphastrea sp.||5||7|
|7, 8, 9||? Coscinaraea sp.||15||22|
|6, 7||Platygyra daedalea||27||25|
|n. v.||Montipora sp.||5||10|
|14, 15||Favites sp.||5||8|
|n. v.||Cyphastrea sp.||9||16|
|14, 15||?Echinopora sp.||14||19|
|14, 15||Stylophora sp.||16||21|
|15, 16||Acropora sp.||14||19|
|16, 17||?Montipora sp.||9||21|
|15, 16||red sponge||-||-|
|17, 18||Stylophora sp.||19||26|
|17, 18||Cyphastrea sp.||8||21|
|18||? Sarcophyton sp.||-||-|
|17, 18||Favia sp.||8||15|
|17, 18||Montipora sp.||29||28|
|17, 18||Favites sp.||9||11|
|18, 19||Leptoseris sp.||24||86|
|18, 19||Astreopora sp.||11||16|
|18, 19||? Echinopora sp.||12||17|
|18, 19||Porites sp.||11||15|
|18, 19||Acropora sp.||7||10|
|18, 19||Echinopora sp.||12||13|
|19, 20||Favia sp.||6||12|
|19, 20||Favites sp.||4||6|
|19, 20, 21||Favia sp.||10||14|
|19, 20, 21||Favia sp.||12||16|
|20, 21||Favia sp.||4||7|
|20, 21||Acropora sp.||7||8|
|20, 21||Goniopora sp.||7||14|
|20, 21, 22||Xeniidae ?Clavularia sp.||-||-|
|21, 22||? Favites sp.||9||11|
|21, 22||Stylophora sp.||12||18|
|19, 20, 21||yelollow, partly dead coral||-||-|
|21, 22||Lobophyllia sp.||9||18|
|19, 20, 21||Coscinaraea sp.||8||17|
|n .v||Psammocora sp.||5||8|
|n .v||Echinophyllia aspera||4||11|
|n .v||Cyphastrea sp.||5||8|
|21, 22||Echinophyllia aspera||12||21|
|22, 23, 24||Xeniidae||12||21|
|23, 24||Echinopora sp.||9||17|
|n .v||Leptoseris sp.||6||15|
|n .v||Gyrosmilia sp.||19||46|
|23, 24||Acropora sp.||18||29|
|23, 24||Acropora sp.||6||10|
The estimation of algal coverage in percent. The sampling frames measuring 20x20cm were placed along the transect line in 2m intervals. 15 individual sea-urchins (Diadema sp.) were found along this 10m stretch.
Tab. 3.3 Percentage data of the algal coverage along this transect.
|Square-ID||1 (at 1m)||2 (at 3m)||3 (at 5m)||4 (at 7m)||5 (at 9m)|
In the marine environment, most potential threats (biological and physical) broadly decrease with increasing depth. Apart from natural disturbances (earthquakes, cyclones, bioerosion, etc), manmade disturbances may range from extensive exploitation of carbonate reef rock by local inhabitants to intensified ENSO-effects (El-Nino-Southern Oscillation) due to globally changed climate patterns. In this year's field excursion we focused mainly on the issue of diver- and snorkeler-related impacts that derive from the booming tourist industry.
Corals under stress: Most coral diseases are stress related. Stress is considered to be a significant deviation from conditions optimal for life; it elicits changes and responses at all functional levels of an organism, and these changes may be reversible. If stress is very intense or persists for a longer period of time, however, these changes can be permanent, thus reducing the overall resistance, and can ultimately kill the organism (Fig.4.1).
The dynamic response of the whole organism to external influences can lead to
distress, comprising a destabilizing effect upon the organism, or eustress, promoting a
stabilizing and resisting effect (Larcher 1995).
Fig.4.1. Phase model of stress events and responses of corals (Larcher 1995).
Unfortunately, the current state of many coral reefs seems to have passed the resistance phase and is apparently entering the final phase of exhaustion. Stress that increases a coral’s susceptibility to diseases can have natural causes (e.g. inter-/intraspecific competition, predation etc.) but can also be anthropogenically induced.
Other damaging impacts include construction activities and the operation and maintenance of these completed facilities (especially freshwater run-off and wastewater management - that nowadays can be partially controlled by introducing renewable energies to maintain sustainable development). The objective of this year's field course, however, was to extensively investigate the direct damages exerted by watersport activities. As the coast south of Aqaba is designated for major touristic development it is crucial to focus on the potential effects on the reef ecosystem caused by unregulated access to the visiting public.
Fig 4.2 Photos of injured snorkeler after being washed against the reef crest by a wave.
Already today, the growing number of snorkelers and divers cause increased damage to coral reefs worldwide. Figure 4.2 shows a snorkeler that was drifted onto the reef (in Nov. 2000). The harm caused by SCUBA diving and snorkelers depends not only on the skills and training of the individual but also upon the dive operators who provide access to a particular reef site. Especially at heavily frequented spots, divers stir up sediments, break corals, and their scuba bubbles damage sensitive overhanging soft corals, while their urine poses an additional stress factor to the fragile ecosystem (Green, 1997). However, unless one actually observes the damage taking place, it is difficult to know for certain the cause of a physically damaged coral. In very shallow areas, where fragile branching corals are abundant, damage by snorkelers can determine whether an underwater "trail" should be closed and snorkelers moved to another location to allow the initial site to recover. Ideally, underwater trails should be placed in areas deep enough to reduce damage from fins, but the best protection comes from educating snorkelers and divers alike.
CDI: The CDI (Coral Damage Index) was used to screen the reef site off the shore of the RDC to obtain a perspective on the extent and severity of physical damages caused to the corals. According to Jameson et al. (1999), sites are listed as "hot spots"; if in any transect the percentage of broken coral colonies is greater than or equal to 4% or if the percentage of coral rubble is greater than or equal to 3%.
DCC (Diver Carrying Capacities) are rarely considered "up-front"; by
planners and developers. As a result, coral reef managers in many areas have to fight uphill battles to
convince authorities to limit sport diving and snorkeling volumes. In areas such as the coast south of
Aqaba, where new development is being planned, DCC can be used to effectively design the size and
configuration of the tourist development so it is in balance with potential diver-related economic revenues.
Finally, the activity of local fishermen probably contributes to the overall negative impact on the reef. At various reef sites we visited, numerous traces and remnants of fishing activity were found. Simple stone anchors are apparently dropped randomly onto densely covered reef sites (Gorgonia I + II, and Saudi Border Drop-Off - see fig. 4.3) often damaging the corals beneath. Abundant fishing nets are entangled in and suffocate the live coral tissue. In consequence, the affected coral parts enables algal turfs to settle, which in turn block off essential sunlight further promoting the colonies decay (e.g. attract larger numbers of bioeroding echinoderms).
Fig 4.3 Damage caused by fishing practices.
Coral Diseases (CD): As mentioned previously, corals can die as a result
of both natural causes and human activities. If these corals are not replaced through the process of
reproduction and recruitment, the reef will eventually degenerate.
In contrast to BBD, however, some infested species (see figure 3.12, the large table
coral Acropora sp.) did not show a consistent assemblage of microorganisms at the junction separating
the sloughing tissue from bare coral skeleton. It was obvious that in these cases we were dealing with white
band disease (WBD, also been referred as “white plague” and “white death”). The etiology of WBD is unknown.
Unusual aggregations of GramNEG rod-shaped bacteria were found scattered in the calcioblastic
epidermis (skeleton-producing tissue) that lined the gastrovascular canals of the porous skeleton. WBD
usually starts at the base of the branches and moves up toward the apical end of the branch tips at the rate
of a few millimeters per day (Birkeland, 1997). As coral tissue dies and is sloughed off the skeleton, endolithic
boring sponges, algae, and other organisms quickly invade the calcium-carbonate substratum, breaking it
down and destroying the coral. Thus, large scale WBD-outbreaks may alter the reef topography, eventually
causing the collapse of the reef itself. Extensive loss of topographic relief affects fish populations as protective
niches and important habitats are altered. The decline of coral-reef fisheries with the concomitant effect of
overfishing probably contributes to further losses in fish species diversity (Rogers, 1985).
During this years survey, we noted that an almost 50% of dead coral coverage among the 4m deep transects (refer to figure 3.1). This result may well be an indicator that unfavorable surface water currents regularly inundate the first few meters. The loss of zooxanthellae and/or to the loss of photosynthetic pigments from the zooxanthellae, which normally give the coral tissue a brownish coloration, may have triggered a massive die off at this depth range. One explanation can be found in the occurrence of a lesser dense surface layer (than the remaining water body) during the hot summer months. It seems that unfavorable conditions may have persisted for more than just a few days, thus killing sensitive corals and paving the way for bioeroding organisms. Again, the r-strategists (like Stylophora, Acropora, and Pocillopora - refer to figure 3.5, and Pocillopora sp. next to F6) were the species most affected by TBL.
This phenomenon is generally referred to as coral bleaching or tissue bleaching (TBL).
Bleached corals, gorgonaceans, alcyonaceans, scleractinians, and anemones have been attributed to
the exposure to high light levels, increased solar UV radiation, high turbidity (sedimentation resulting in
reduced light levels), temperature and salinity extremes, and other factors. The nature and extent of
bleaching vary between individuals and among species at the same location during a bleaching event
and have been attributed to different physiological tolerances of the species of zooxanthellae and the
coral hosts. Chronic partial or widespread loss of zooxanthellae, for whatever reason, signals a disturbance
in the normal metabolism of the coral host and can lead to delayed or reduced reproduction, tissue
degradation, reduced growth, and death of the affected tissue (Williams and Binkley-Williams, 1990).
Revised Rapid Assessment Program (RRAP): The vitality of a reef (apart from bioeroding invertebrates) depends on complex relationships among corals, fishes and algae (fig. 4.4). When changes occur in the community dynamics of one of these components (e.g., algal abundance), the other two components are affected as well and the whole relationship can be disrupted. Therefore, to evaluate the condition of a reef from a one-time assessment, it is critical that multiple indicators of the corals-algae-fishes relationships are examined. RRAP is one of few programs that have been developed to generate an extensive regional database on Caribbean coral reef condition. Apart from the CDI-program, our working group attempted to apply the RRAP in order to assess damage that go beyond the impact of diver and snorkeler related effects.
The application of this program turned out to be a major challenge to all participants,
as essential knowledge regarding coral taxonomy, invertebrate recognition, and fish identification was
extensively applied during this attempt.
Fig.4.4 Reef interdependence (adapted from Ginsburg - originally Jackson,1994).
The herbivores (Pomacentridae, Signaidae, Acanthuroidae, Echinoidae and Scaridae)
serve several functions. They result in a higher, overall ecosystem primary-productivity, they facilitate the
flow of energy to higher levels in the trophic web, and if intense, they lead to the predominance of sessile
organisms, particularly those with calcareous skeletons (Wood, 1999).
Ataxonomic Approach - Identification of damage within an ecosystem:
It may rather undergo drastic changes regarding the balance between producers and
consumers (see fig. 4.5).
Accordingly, ecosystem stability does not exist as such, but rather is a constantly
tuned system that dynamically adapts to variability, recovery, migrative patterns, loss of species, and distinct
characteristics in time. In order to determine the integrity of an ecosystem, a long-term monitoring program on
species composition can provide an answer.
Fig.4.5 Disturbance and recovery within the reef ecosystem; c, colonizers, p, persisters (adapted from Steinberg, 1999) 2.
Fig.4.6 Ataxonomic approach (adapted from Steinberg, 1999)2.
Bacteria are the most abundant but also the least heavy, while the fish are the most heavy and the least abundant. In ecosystems that are shifted out of balance, larger gaps (as seen in figure 4.6) indicate a disrupted population composition. Such patterns are usually characterized by the absence of certain "size class"- predators. This absence can either be the result of incomplete data material, insufficient sampling methods, or simply the consequence of a perturbed ecosystem. Thus, the ataxonomic approach enables a quick and efficient check of a reef-ecosystem. By pin-pointing the absent size-class(es), this approach enables the identification of key-species and their use as indicator organisms. The only question that cannot be answered under these circumstances regards the dimensions of the disrupted pattern (within the logarithmic plot). For example, what is the threshold size of a gap in order to assign an ecosystem stressed or even disrupted properties? We assume that this question can only be answered when confronting the gap size data with the species abundance data of the reef ecosystem.
Conclusion: Although coral reefs are among the most productive ecosystems in
the sea, reefs are among the most vulnerable to overexploitation. This years survey revealed that the dive
sites off the RDC are under stress by both the diving community, the snorkeling public, the fisheries, and
presumably several abiotic factors exert a too heavy extra burden onto the coral population. In all aspects,
from the coral damage index, via the diver carrying capacity, to the coral diseases, we found enough
evidence that this stretch of reef is no longer in balance in regards to the construction and the (bioerosive)
destruction of calcium-carbonate matter.
Finally a short checklist for responsible "coral reef divers":
Acknowledgements: We would like to express special thanks to Dr. K. Kleeman for helping us to correctly identify coral species.
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General links regarding Coral Reef Damages
Ataxonomic approach - Dr. Steinberg (Stein@IGB-Berlin.de) or at http://www-3.igb-berlin.de/
lecture given at Salzburg University, 2001: