A Marine Pollution Topic

1. Evaluating the Impact of Sewage
Discharges on the Marine
Environment with a lightweight
AUV (Autonomous Underwater
Vehicle)
PRESENTED BY: DIANE C. BISAYA
ANETTE JAY P. QUIAMCO

2. INTRODUCTION

3. Introduction
• There are two main sewage treatment plants in Palma (Mallorca, Spain),
EDAR I and EDAR II, built between 1971 and 1975, were expanded several
times until 2005 to cater the increasing population.
• The EDAR I sewage treatment plant is unable to treat properly the waters,
and the nitrogen and phosphorus present in the discharges exceed the
amount set by the European Directive 91/271/ CEE

4. Introduction
It is well known that wastewater discharges affects twofold the
marine environment, first, augmenting the risk of human infectious
diseases in leisure bathing areas and, second, liberating organic and
chemical pollutants which degrade the environment affecting the
marine communities health and the food chain of aquatic biota,
potentially suppressing the primary production of phytoplankton,
macroalgae and submerged aquatic plants.

5. Introduction
a b
Fig. 1. (a) One of the reddish spots found in September 2016 and (b) diver taking core samples in situ.

6. MATERIALS &
METHODS

7. Materials and Methods
2.1. Bio-analysis of substrate samples
In September 2016, the divers manually collected water samples at the
sediment surface in sterile water bottles and 30 cm in the sediment covered by
the red mats using a 50 cm core and transported to the laboratory for
microcosms experiments.

8. Materials and Methods
Fig. 2. Phase contrast and autofluorescence micrograph of a marine Spirulina sp. culture obtained from the samples of Palma Bay.

9. Materials and Methods
Fig. 3. (a) One of the core samples in its initial state. (b) A close image of the same sample with visible iron sulfide (FeS2) (blackish
sand) and red cyanobacteria areas. (c) The same core sample, six months later, with incipient micro and filamentous algae.

10. Materials and Methods
Fig. 4. (a) The sample core re-contaminated with synthetic wastewater. (b) The same sample core with new cyanobacteria. (c)
Recuperation of the filamentous algae.

11. Materials and Methods
2.1. The robotic setup
Turbot a lightweight Autonomous Underwater Vehicle (AUV) model Sparus
II unit was programed to six missions, surveying areas near or away from the
discharge point of the sewage system in Palma (Mallorca, Spain). Recording
the Posidonia regression due to wastewater discharges and estimating the
extension, location, and evolution in time of the damaged area.

12. Materials and Methods
Fig. 5. Turbot AUV (a) on the stern of a boat and (b) moving underwater.

13. Materials and Methods
Fig. 6. Location of the missions completed by the AUV.

14. Materials and Methods

15. RESULTS

16. Results
3.1. Cyanobacteria analysis
In Section 2.1, a detailed experiment is presented indicating that
cyanobacteria pioneers the recuperation of the benthic community, because of
their tolerance to H2S and other organic matter present in the water. It shows
that due to the organic pollution, the endemic biota disappears and it is
substituted by another, if no further wastewater is provided.

17. Results
Fig. 4. (a) The sample core re-contaminated with synthetic wastewater. (b) The same sample core with new cyanobacteria. (c)
Recuperation of the filamentous algae.

18. Results
3.2. Robotic missions
A total of six missions were programed for Turbot (Autonomous Underwater
Vehicle) covering the seabed of Palma for Posidonia oceanica observation.
With the data obtained by the AUV, the P.o. are visible and progressively more
frequent as the vehicle moves away from the discharge point of the sewage.

19. Results
Fig. 7. Vehicle trajectory of mission R1. Dimensions are expressed in meters. b) Photo-mosaic of the surveyed area.

20. Results
Fig. 8. (a and b) Mosaic segments of a longer transect in mission R4, showing sand and P.o. remains. (c) Mosaic of a region visited
during mission R4 including a highly fragmented P.o. meadow. (For interpretation of the references to color in this figure legend, the
reader is referred to the web version of this article.)

21. Results
Fig. 9. Photo-mosaic covering 400m2 of mission R5. Fragmented P.o. is highlighted in red. (For interpretation of the references to
color in this figure legend, the reader is referred to the web version of this article.)

22. Results
Fig. 10. Enhanced images, taken from the AUV during mission R5.

23. Results
Fig. 11. Samples of cyanobacteria mats found in R5, photographed during the immersion of September 2017.

24. Results
Fig. 12. Individual images recorded during mission R6 used for the mosaic of Fig. 13.

25. Results
Fig. 13. Photo-mosaic of an area of about 400m2 covered by Posidonia oceanica.

26. Results
3.3. Last scuba divers sampling mission
A scuba dive in the area corresponding to mission R5 is conducted as
recorded on Table 1, labeled D2, where new core samples are taken and
observations to reddish patches are recorded. An analysis have been
organized, confirming the presence not only of cyanobacteria but also
presence of 20 Escherichia coli and 105 Clostridium perfringens spores per
100 ml of marine water. Degradation of P.o. in the same area concludes the
zone as highly polluted and contaminated.

27. CONCLUSION
&
DISCUSSION

28. Discussion and Conclusion
By persistent marine pollution caused by land and coastal activities,
researchers have gone through means and actions in order to determine the
presence of pollution in an area and how to eradicate it. A study is conducted
in the marine areas of Palma (Mallorca, Spain) as several amateur divers
have reported the unusual presence of reddish spots in the seabed and the
degradation of Posidonia oceanica, a seagrass species endemic to the area.
The objective of the study is to use AUV (Autonomous Underwater Vehicle to
explore the area, sending the divers to precise locations for sample
collection that will be analyzed and studied in the microbiology lab for
presence of other substance.

29. Discussion and Conclusion
The analysis base from the photo-mosaics and videos taken from the AUV
and laboratory analysis concludes the following:
● The regions near the sewage outfall is barren and the Posidonia oceanica
that could be present are with high mortality.
● There are visible reddish spots around the discharge point, suggesting the
presence of cyanobacteria, sediment samples are collected, revealing the
presence of cyanobacteria, Escherichia coli, and Clostridium perfrigens,
which confirms the persistent organic pollution in the area.
● Areas 8 km away from the discharge point showing ecosystems with
excellent heath with a dense population of Posidonia oceanica.