Opinions differ on use of cenote by Nova Shrimp
On June 25th, Dr. Thomas M. Illiffe of Texas A & M University, and one of his graduate students, Brad Dodson, dove into the cenote. (Dr. Illiffe was not acting on behalf of the university.) According to his report, "The purpose of our visit to the cave was to evaluate the possible effects of disposal of large volumes of waste water from the proposed Nova Shrimp Hatchery into the cenote." The trip to the cave was organized and facilitated by representatives of Nova and the Department of the Environment.
In his report dated July 31st, 1997, Dr. Illiffe explained some of his qualifications, citing a 1988 dive into Giant Cave at Caye Caulker. This cave is a large submerged system under that island. He also has made many other underwater cave dives in the Yucatan. Dr. Illiffe described the cenote as approximately 1.5 meters in diameter and being surrounded by a stone wall, possible of Mayan origin. This same cenote was dived by Alan Forman some years ago. The cenote was also tested some years ago for salinity of water by Mr. Garcia. He determined the cenote was not a source for fresh water as the salinity increased as the pumping went on, indicating a connection to salt water, and not an underground fresh water source.
Dr. Illiffe described diving through chambers and passages, some back sections of caves with exposed rock covered with a 5 centimeter thick coating of bright orange, filamentous bacteria. In addition, he noted numerous eyeless white shrimp. "This type of cave-limited shrimp is also present in caves and cenotes in the Yucatan and Quintana Roo." He said there was fresh water until 12 meters and full salinity was found at 16 meters. Dr. Illiffe said, concerning the cenote, "The overall orientation (primarily north-south) and the depth at which most of the cave passage development occurs is quite similar to Giant Cave on adjacent Caye Caulker. It is likely that these two caves were formed about the same time and under similar conditions. (During the ice ages when the sea level was as much as 100 meters lower than today. He determined this since there are stalactites and stalagmites at the lowest levels of the cave and these are created in air by dripping, mineral-bearing water.) If this is true, then much larger passages and cave chambers such as those in Giant Cave are likely to be present under Ambergris Caye." Dr. Illiffe maintains these cave systems are delicate and easily polluted, citing a single incident in Bermuda where leaves and trash were dumped, polluting not just the one cave, but at least 5 other caves within a 2 kilometer radius. "Since many cave animals are known only from a single cave and nowhere else, pollution of caves can result in extinction of entire species. Considering the apparent size of the North Ambergris Cenote and the significant biology that is present there, this cave is of considerable importance. Therefore, I strongly oppose the disposal of waste water into this cave.
I would like to see more data on the exact composition of this effluent, especially a chemical comparison of water entering and leaving the hatchery. In this way, it would be apparent precisely what is accumulating in the effluent water.... Perhaps the effluent could be cleaned with gravel filters or other means before disposal through a pipe line in deep water well outside the reef."
A copy of the report was forwarded to the Department of the Environment and to Nova Shrimp. José Pepe Garcia, who is preparing an Environmental Impact Assessment on the project, replied to the report. We have not received a copy of his letter. Dr. Illiffe disagrees with some of the statements made by Mr. Garcia in the letter such as "....sure that the effluent entering this one cenote will not have a detrimental effect." Dr. Illiffe states that he and Mr. Garcia disagree in their assessments of the direct effects of waste water disposal of this cave and the potential for the pollution to spread to adjacent caves. Dr. Illiffe also indicates his questions regarding the chemical composition of the water entering and leaving the hatchery were not addressed. Mr. Garcia said in his letter that the "quality of the effluent would be almost similar to sea water." Dr. Illiffe would like to know how it is different and wrote, "In what ways is it different? What volumes of effluent would be disposed of in the cenote? With detailed information on the chemical loading added to sea water by the hatchery and the volume of this effluent, it should be possible to calculate what extent to which the groundwater would be impacted. Since water currents in these caves are probably slight, it may take months to years for water masses to be transported through the cave system. Thus, a short term dye tracing study is unlikely to provide significant data relative to the groundwater movement.
If the waste water effluent is so similar to seawater as Mr. Garcia claims, why can't it be recycled or returned to the ocean?"
