bay paracas contamination
Project: Study of marine contamination in the Bay of Paracas
Time of implementation: December 2003 to January 2004
Project Director: Stefan Austermühle
• Review and resume existing information on the level of contamination of the Bay of Paracas and the sources of contamination.
• Measure the environmental impact of marine contamination within the Bay of Paracas.
Why was this project necessary?
Because of its semi-closed shape, the Bay of Paracas is sensitive to marine contamination. For forty years, the fish meal production plants situated in the north of the bay have discharged more than 30,000 tons of protein and 8,000 tons of fish oil every year, as well as thousands of tons of fish waste from the fishing boats and chemicals used to clean the plant’s machinery into the bay without any previous treatment. According to a study from the year 2000, the contamination produced every day of production by the seven fishmeal plants equals the domestic sewage of a city of 75,000 inhabitants.
The huge influx of organic sewage exceeds, by far, the bay’s natural capacity of decomposition. During the last years, massive deaths of fish has become a common phenomenon in the area of Pisco-Paracas, generally during the summer months and correlating with the periods of high production in the fish meal plants. The beach of Santo Domingo, south of the fish meal plants, has been the most frequent location for this mass die-off and the fish species liza (Mugil cephalus), has been the most affected one.
Using metal frames of 50 X 50 cms of size 144, samples of benthic life and sediment have been collected in 6 transects within 8 sample stations and 3 replics per station. The positions of the sample stations have been taken using a GPS Garmin 200. In each station, the exact position of the replics taken was at random.
All marine specimen collected were preserved in alcohol. In Mundo Azul’s laboratory in Lima, specimens were finally preserved, species and number of specimen per species of each sample where determined. Total biomass of each species per sample was measured. Several statistic methods were used in order to analyze the samples.
The information collected from the samples and transects demonstrate a very high level of contamination resulting in an extensive dead zone within the bay. In most of the samples, there was zero biomass.
Generally, life was concentrated within the first 200 meters of the shoreline in-depth lower than 2 meters, where the small waveaction within the sheltered bay still delivers some oxygen. In these areas, unnaturally high concentrations of several marine species have been found. These shallow areas, where wave action provides oxygen and avoids the sedimentation of organic material seem to be used as last refuges for survival by several species, leading to this high concentration of specimen.
In areas deeper than two meters and further offshore, no life could be found except very few specimens of the crab species, “Eurypanopeus transversus, walking extremely slow or sitting immobile on the toxic layer of undecomposed, organic material, which was covered by slimy bacterial growth. The crab’s bodies themselves were covered by white bacterial growth and the specimen moved very slowly, nearly not reacting when pushed with the finger by the divers. In other areas, only juveniles of the species have been found in the samples, but no adults – sign of a seriously outbalanced population.
In most samples, with zero living biomass, very high concentrations of empty tubes of polyquetes have been found indicating the serious contamination of the area. Not one fish has been seen during the entire sampling period.
Typical result in the sampling transect. Only in the first sample station (1), being closest to the shoreline, less than a hundred grams of living biomass per square meter have been found. The weight of empty tubes of dead polyquetes however, found in several simple stations varied between 1.4 and 3.2 kilograms per square meter. This area is biologically dead and heavily contaminated.
Near the fish meal plants, divers could push their arms until their shoulders into the soft layer of undecomposed organic material without reaching ground. In the first two transects, divers had to wash their mouths with mineral water as the seawater started burning within their mouths and an acid taste was felt. While sampling near the fish meal plants and in the southern end of the bay, divers could smell the sulfur gas concentrated in the sea bed underwater, while it was entering their diving masks.
As expected, the value for species diversity never was higher than 0.1, being the lowest ever encountered by Mundo Azul divers.
The study concludes that the entire area of the Bay of Paracas, being deeper than two meters and further off shore than 200 meters, is biologically dead – an approximate extension of 17 square kilometers.