Preliminary Site Only – In Development to include Technical Reports and Previous Underwater Monitoring

 

 

 

Observations of Benthic Biology and Geology at a Location of 0.5 km off the center of the Crescent at Palm Island, Dubai.

 

By

Professor Joe Valencic

May 2003

 

OVERVIEW

Based on a limited number of SCUBA dives, the bottom conditions at various distances off the center of the Crescent at Palm Island were observed and documented via underwater digital video.  The intent of these research SCUBA dives was to determine suitability of habitat for the Palm Island Dive Center and the artificial reef site consisting of two large commercial jet aircraft.

 

CONDITIONS

Because of the turbidity from the construction of the Palm, visibility was relatively poor ranging from a low of 2-3 meters to a maximum of approximately 7-8 meters.  Water temperatures were approximately 82 degrees F with a vertical thermocline of no more than 1-2 degrees F.  Previous measurements of salinity using a Saline Refractometer indicate ocean salinity in the range of 39 to 42 parts per thousand.  (Normal ocean salinity is approximately 35 parts per thousand)  These recorded high temperatures and salinity levels provide a difficult environment for coral growth in general although a number of species thrive provided there are no excessive warming conditions, like El Nino.

 

The depth of the water was measured at 11-12 meters in the area surveyed.  However closer to the center of the Crescent we measured depths of 13 meters.  Tidal range was not taken into account so this could account for the slight difference in depth.

 

OBSERVATIONS

The bottom conditions 0.5 km off the center of the Crescent at Palm Island consisted primarily of a hard consolidated substrate with a thin layer of loose sediment that was both  lithogenous and biogenous in composition.  Because of the relatively shallow depth, the sand was arranged in shallow troughs resembling wave patterns with crest-to-crest distances of approximately 20 to 50 cm.  Between the sand crests, the hard consolidated substrate was evident and verified with a hammer.  I understand that the thickness of this consolidated hard layer is approximately 40 cm deep however this has not been verified. 

 

The hard substrate provides a foothold for various benthic marine organisms.  Several species of mollusks were attached to the bottom including a species of pearl oysters.  Sea Urchins were also observed. There was a noticeable lack of rocky reef structure or even boulder rubble in this area.  As a result, fish populations were minimal.  However, a stepped fracture in the hard consolidated sediment was observed creating a small 20 to 40 cm ledge with an undercut shelf.  In this area numerous Arabian Angel fish were observed and several small damselfish.  Fish require a moderate degree of protection that is normally afforded by rocky reef or coral benthic conditions.  Lacking this protective habitat, vertebrate populations are minimal.  If is for this exact reason that the artificial reef structures that will be placed on the bottom in the Dive Park area of the Crescent should significantly increase marine communities including at least 12 different fish species.  This was verified on several other SCUBA dives on the Cement Barge and on the Car Dump Area just south of Palm Island.

 

SCUBA dives that were made between the 0.5 km point and the actual center of the Crescent breakwater produced slightly different bottom topography.  When moving shoreward of the 0.5 KM mark the sediment becomes very fine with no distinguishable hard consolidated bottom.  In this area, PVC reference stakes could be easily hammered into the soft bottom.  However, boulder piles and loose rock assemblages were common and often observed as we explored the bottom.  Typically these rocky outcroppings were about a meter in diameter with a vertical elevation of approximately 0.5 meters or less.  Since they were composed of large rocks rather than a single uplifted slab of consolidated sediment, there were numerous small cares and crevices for marine life to find protection.  These small rocky outcroppings were often rich in fish yielding sometimes as many as 4 to 5 different species clustered in this tiny area.  These observations again verify the importance of artificial reef structures to insure healthy marine invertebrate and fish populations.

 

SUMMARY

 Additional SCUBA dives and the accompanying digital video and still photos are required to more accurately access conditions in the area seaward of the Crescent at The Palm.  Technology is currently being considered for implementation that will permit live, Internet monitoring of oceanographic conditions (turbidity, temperature and salinity primarily), and marine communities off the Crescent area of The Palm.