River dolphin deaths are still rising in Amazonas state and ICMBio takes over operations in Coari

09 novembro 2023

Adding the 70 carcasses recorded in the municipality to 159 found in Tefé, the number of animals that lost their lives reaches 229
By Solange Azevedo, WWF-Brazil

With the growth in the number of river dolphin deaths in Lake Coari, inner Amazonas state, ICMBio (Chico Mendes Institute for Biodiversity Conservation) decided to take on leadership of the task force that operates in the area. Upon that, a new monitoring protocol could be established in the municipality's main lake, where 70 carcasses have been recorded so far, in order to investigate the reason for the deaths. Adding up the 159 cases documented in Tefé since the beginning of the crisis affecting the state, the number of animals of the pink river dolphin (Inia geoffrensis) and tucuxi river dolphin (Sotalia fluviatilis) species that have lost their lives now reaches 229.

“Unlike what happened in Tefé, here the water temperature did not rise as much. It reached a maximum of 34º Celsius since the beginning of measurements, two weeks ago. However, we identified a higher concentration of Euglena sanguinea, an alga that can be toxic to fish. But there are no studies proving whether it is also toxic to mammals”, says professor Waleska Gravena, from UFAM (Federal University of Amazonas state), who has headed the operation in Coari since the beginning. “What increases the mystery and doubts is that the proliferation of this type of algae occurs due to the incidence of solar radiation for many days.”

As the animals were found scattered throughout Lake Coari, according to Waleska, one of the hypotheses is that they died in other points, some of them inaccessible to the research team, and the carcasses ended up carried by the current. “Although in Tefé the cause of death was not water contamination, we are collecting samples for laboratory analysis to assess the level of toxicity. Furthermore, the carcasses will be necropsied”, adds the professor. Some of them show signs of interaction with humans, such as marks from fishing nets and cuts on the tail. The region is known for the activity of illegal manatee hunters.

The ICMBio team arriving in Coari will join professionals from UFAM, which has coordinated the operation so far through professor Waleska, and Sea Shepherd Brasil, an NGO for the conservation of aquatic animals. Other people who were decisive in Tefé also reinforced the team, including three from the Mamirauá Sustainable Development Institute (IDSM) – oceanographer Miriam Marmontel, leader of the Amazon Aquatic Mammal Research Group, and researchers Ayan Fleischmann and André Zumak, from Research Group on Geosciences and Environmental Dynamics in the Amazon –, in addition to Mariana Paschoalini Frias, Conservation analyst at WWF-Brazil and coordinator of SARDI (South American River Dolphin Initiative). Other support, such as from City Hall and the Municipal Environment Secretariat, is also expected.

Situation in Tefé

The IDSM, which continues to monitor Lake Tefé and has not detected abnormal behavior among the dolphins, highlights that this period of water movement is critical for the river dolphins, as new waves of mass deaths may occur. “I'm sure there were deaths in other places because there are more than 50 lakes in the region”, warns Miriam Marmontel. “This is the first time in the world that heat, and the climate crisis, has killed aquatic mammals in this way. What is happening in the Amazon is comparable to what is happening in the Arctic with walruses and polar bears.”

If in the Arctic animals are dying due to the melting of glaciers, in the Amazon one of the most serious consequences of climate change for aquatic fauna is the increase in the temperature of water bodies, which in 2023 was aggravated by an abnormally warm North Tropical Atlantic Ocean and an El Niño phenomenon, generating an unprecedented drought in the biome. All 62 municipalities in Amazonas, for example, are in a state of emergency, according to Civil Defence. More than 600 thousand people have been harmed so far.

“Extreme droughts and floods will happen with increasing frequency and intensity. And the tendency is for the situation in the Amazon region to worsen, as the expectation is that next year El Niño will be even stronger”, highlights Miriam. “River dolphins are perfectly adaptable to the movement of water during floods, they move with tremendous flexibility in the flooded forest to feed. But they are not adapted to drought. Reversing this scenario does not depend on us, researchers, it depends on all of humanity mobilising.”

Thermal stress

Ayan Fleischmann, also from IDSM, points out that in Tefé the most likely hypothesis is that, as a result of heat stress, the animals stopped eating and, therefore, lost the ability to regulate their body temperature. “In situations like this, blood pressure rises and there may be a brain collapse, such as congestion or stroke. But we are still waiting for the histopathology analyses to find it out,” he says. “If the increase in blood pressure is confirmed in the tests, we will have discovered in the worst possible way the temperature limit that the dolphins can withstand. That’s why the next few years terrify us.”

The crisis in Tefé broke out on September 23. On the 28th of the same month, the deadliest day for animals in the municipality, when the water temperature reached 39.1°C in Papucu Cove, 70 river dolphins lost their lives. “Above Papucu we measured almost 41°C, but the temperature dropped along its course until it reached 33°C or 32°C in the Solimões River. We saw that the flow of water was dissipating the heat”, says Fleischmann.

Among the results documented so far by the task force operating in Tefé, there is no evidence of infectious agents related to the primary cause of mortality. Molecular diagnostics were also negative for the infectious agents Morbillivirus, Toxoplasma, Clostridium, Mycobacterium and Pan-fungal, which are associated with mass deaths of cetaceans.

Several institutions took part in the operation involving the river dolphins, including: Aiuká Consultancy for Environmental Solutions, Aqua Viridi, Aquasis, Tefé Fire Department, Regional Council of Veterinary Medicine of Amazonas State, European Association for Aquatic Mammals, Brazilian Army, Friends of Nuremberg Zoo Association, Aquatic Mammals Foundation, Fundación Mundo Marino, GRAD - Disaster Animal Rescue Group, Greenpeace, IBAMA - Brazilian Institute for the Environment and Renewable Natural Resources, ICMBio, IDSM, INPA – National Institute for Amazon Research, Institute Aqualie,  Humpback Whale Institute, Oswaldo Cruz Institute (IOC/Fiocruz), International Fund for Animal Welfare, IPAAM - Institute for Environmental Protection of Amazonas, Lapcom-USP, Loro Parque Fundación, Brazilian Navy, National Marine Mammal Foundation, Nuremberg Zoo, Oceanogràfic València, Planète Sauvage, Military Police of Amazonas State, Tefé City Hall, R3 Animal, Rancho Texas, Sea Shepherd Brazil, Sea Shepherd France, SeaWorld & Busch Gardens Conservation Fund, SEMMAC - Municipal Secretariat for the Environment and Conservation of Tefé, University of Las Palmas de Gran Canaria, WWF-Germany, WWF-Austria, WWF-Brazil, WWF-Netherlands, WWF-United Kingdom, YAQU PACHA and Zoomarine Portugal.

What WWF-Brazil is doing

WWF-Brazil has been working in partnership with IDSM and the task force in Coari, providing fuel, Personal Protective Equipment (PPE), veterinary supplies and logistical support for the movement of volunteers. It is also in contact with local partners and mobilised to support them in facing the humanitarian crisis caused by the drought in the Amazon region, as the consequences are especially dramatic for the most vulnerable populations, such as indigenous people, quilombolas, extractivists and riverside dwellers. At this moment, our main area of activity is distributing food to communities impacted by shortages. We are also working on providing equipment for fire fighting brigades, due to the intense wildfires that have been occurring in the region.

“In the Amazon, we are experiencing a historic drought, with forest fires and high temperatures, caused by increased deforestation and intensified by El Niño. The consequences of this drought are serious for local populations and biodiversity, so much so that we have already recorded the death of 229 river dolphins in the region”, says Mariana Paschoalini Frias, Conservation analyst at WWF-Brazil and coordinator of SARDI (South American Initiative for River Dolphins). “This tragedy shows the urgency of adopting joint measures to conserve the Amazon, a key biome for climate dynamics around the world, and river dolphins, species that are fundamental to ecological balance and that allow us to assess the health status of ecosystems where they live.”
159 botos cor-de-rosa e tucuxis foram encontrados mortos no Lago Tefé, no vizinho Lago Coari, 70 carcaças foram encontradas até o dia 09 de novembro de 2023
159 pink river dolphins and tucuxis were found dead on Lake Tefé, at Lake Coari 70 animals were found in the same conditions by november 9th
© Miguel Monteiro / Instituto Mamirauá