Dolphins

Toxic Algae Blooms: Health Threat to Dolphins and People

Over the past 50 years, a great number of previously un-known human diseases emerged, while other well-known maladies, including cholera and tuberculosis, have seen a significant resurgence. Not surprisingly, dolphins and other marine mammals experience a similar trend, with various papillomaviruses, dolphin poxvirus, lobomycosis, various neoplastic diseases, and algal bloom bio-intoxication being among the better-understood disease agents or diseases. Our experience in human medicine should cause all of us to be concerned about the deterioration of aquatic eco-systems, coastal freshwater or marine, especially since they support more than half of the population in the U.S. alone.

Monitoring the overall health status of dolphins provides an excellent avenue to evaluate the wellbeing of entire aquatic systems, and identify possible environmental trends. Dolphins are the ocean canaries, warning us about existing and emerging threats not only to the aquatic eco-systems, but also to human health. No doubt, it is in our own best interest to closely observe any patterns affecting their behavior or health as it could affect humans in the long run.

Let’s focus on the recent water-related issue in south Florida: the catastrophic, harmful algae bloom that descended onto the Port St. Lucie River lagoon and associated waterways and tributaries to both the east and west coastlines of Florida. Algae blooms have become a regular occurrence in this area for years, but this year’s outbreak was larger by order of several magnitudes.

While some people may think that such algae blooms represent little, if any dangers, it is well established that such blooms produce neurotoxins that can kill dolphins and other marine life, as well as biotoxins that affect human health. Among those threats to our own wellbeing are brevetoxins and saxitoxins that cause poisoning, and okadaic acid, which causes diarrhea.

Some recent disease outbreaks (epizootics) among bottlenose dolphin populations in southeast Florida serve as prime examples of how studying dolphins can help us manage health risks. Several of these outbreaks were associated with brevetoxins, produced by a dinoflagellate called Karenia brevis. That is the same species causing the so-called red tides. Brevetoxins are known to kill and/or contaminate fish and shellfish. Once we consume those, or simply inhale toxic aerosols, we will fall ill. It is noteworthy to emphasize that the actual exposure may be delayed, meaning that the risk to human health continues long after, or far away, from the original dinoflagellate bloom.

Some of the visible impact of exp083_bb_032411__0890_skin-lesion-600x400osure to toxins and viruses manifests itself in form of changes on the dolphin’s skin (see image), just as sun- chemical burns damage our skin. Some of these damages may be short-term, changing the color of the skin, or leading to the shedding of dead skin (common results of sunburns in humans), but long-term impacts, including skin cancer are well documented. In summary, any increase in toxins, whether due to natural or anthropogenic cause, in our coastal habitats must be of great concern to us.
While we may not yet fully understand how these toxins are absorbed and travel through the entire food chain, there is no doubt that dolphins can serve as the sentinels for ocean and human health.

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Why it is important to study wild dolphins

Most people love whales and dolphins. They think of them as intelligent creatures. They have heard stories of dolphins coming to the aid of stranded sailors, guiding swimmers back to shore and engaging in cooperative hunting with local fishermen. They feel whales and dolphins are important. And they are right! Maybe more than you might think!
Whales and dolphins embody most of what we need to understand about oceans. They are predators at the top of the food chain and can tell us a lot about what is important in the ocean; where are sites of high productivity, what is the most energy efficient way to travel, and what are the best senses to use in the water.
Because of their complex behavior and social structure, whales and dolphins are especially interesting. But they also offer us a window into the physiological and anatomical adaptations to aquatic life; information we can apply to echolocation and boat sonar. More than valuable intellectual exercises, these studies help us understand phenomena such as population decline, recovery, and extinction, and teach us to care about the world. Generally, understanding begets caring.
Further, whales and dolphins are a vibrant part of the global ecosystem and their populations have been severely affected by, and continue to be extremely vulnerable to human impact, including interactions with fisheries and whaling. Above all, marine pollution and habitat degradation looms as the most menacing threats of all. If we have any philosophical leanings towards preserving nature, either for future generations or for its own value, than learning enough to prevent this damage is crucial.
Lastly, whales and dolphins, are the archetypal ‘charismatic mega-vertebrates’. Throughout centuries, whales and dolphins have played major roles in myths and legends. Every culture that has come into contact with an ocean, have created myths and legends about how whales and/or dolphins came into being, and what their existence means to the world and to us.

In our times, whales and dolphins have come so symbolize, more than any other species, the concern for the environment and have become a special symbol of sharing the earth. People react to them with empathy and express concern for their welfare. They epitomize and illustrate many of the problems humans inflict on the sea. They engender, in people who might not otherwise care, a wish to improve the ‘health’ of the marine environment. The huge interest in these animals can therefore be used to encourage interest in the sea more generally, with whales and dolphins becoming flagships or ambassadors of the oceans.

All that makes it important to study these wonderful creatures. If you understand dolphin echolocation and how it works, then you have the tools to apply that knowledge. If you are a conservationist and are concerned about dolphin entanglement in nets, knowledge allows you to reduce that risk. The application of the knowledge depends on what you value: for an academic, to further knowledge and understanding; for an applied researcher, to be able to provide information to managers on the implications of a range of management options, for a conservation biologist: to find ways of ensuring the health of populations and habitats.

For more than thirty years, bottlenose dolphins (Tursiops truncatus) have been studied along the west coast of the United States, the Gulf of Mexico and along the eastern sea border, from the Carolinas to the southern tip of Florida. I have been involved with Coastal Dolphin Conservation through the Palm Beach Dolphin project of the Taras Oceanographic Foundation, headquartered in Jupiter, Florida. This project provides critical information on coastal dolphin communities, their lives and societies and shed light on how the health of these top predators, and the conditions of the natural resources they depend on, may directly or indirectly impact our own health and well-being.

In light of the enormous impact whales and dolphins have on humans and their lives, it is not difficult to understand why studying them serves the support of all of us. Search the Internet for the word dolphin sometime and see how many ‘hits’ you get. People believe that whales and dolphins have value and people put their money in things they hold interesting.
Why do dolphins hear sounds up to 150kHz while we hear only to 15? What is there to listen to anyway? Why do only male humpback whales sing and why don’t females? What directs Humpback whales in Hawaii to swim directly north in the summer? How do they know which way is North? Do dolphins ‘see’ an image in their brain from echolocation signals that is similar to what we see with our eyes? Does a dolphin think, and if he does, what does he think about? Do whales dream? Why are blue whales the biggest animals that have ever lived on earth? Why do dolphins have pointy rostrums? But most importantly why does anyone care about the answers to these questions? The main point is that people do care, and this is why we should all take a stand, and invest our time and money into understanding and protecting these marvelous marine mammals. No doubt, life is better with dolphins around.

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Threats to Whales and Dolphins

Wales and dolphins are a vibrant part of the global ecosystem and their populations have been severely affected in various ways. Many species have been over-hunted in the past, and several populations are reduced to a small fraction of their original levels. They are vulnerable to entanglement in fishing gear and incidental catch in gillnets is one of the most serious threats to marine mammals. These fishery operations may well cause the extinction of several small cetacean populations within the next few decades, including the Vaquita and Chilean dolphins. Collisions between larger whales and ships (ship strikes) occur with regular frequency and represent a significant cause of death and traumatic injury. Because toothed whales and dolphins are top predators and thus at a higher tropic level in the food chain, they are especially prone to bio-accumulating toxins, such as heavy metals, persistent organic pollutants (POPs) and endocrine disrupting chemicals (EDCs). However, as recent research has demonstrated, such toxins and pollutants also negatively impact baleen whales.

Another threat to the health of whales and dolphins comes from the petroleum industry. Seismic surveys, which are used to discover oil and gas field situated below the seabed are, at a minimum, suspected to damage the complex hearing system of these marine mammals. Once the oil extraction processes is under way, the negative impacts shift habitat loss and exposure to hydrocarbons, lubricants and outright pollutants and toxins used in the process.

Loss of whale and dolphin habitat is directly linked to increasing human activity in and along marine environments. The aggregation of wastes we allow to flow into our streams and estuaries, and ultimately into the oceans, is a biochemical soup carrying thousands of different chemicals. Rainwater and snow melt, that run off from congested urban areas, collect street oil and chemicals as well as many metals. Runoff into streams and rivers adjacent to farmlands carry tons of suspended particles of soil. This is not only damaging to fish but can also choke-out submerged oxygen-giving grasses in coastal woodlands, bays or estuaries. Runoff from timber harvesting activities, especially clear cutting, deprives the exposed land of thousands of tons of soil and has caused the pollution of some of the most valuable spawning grounds for trout and salmon in the Pacific Northwest. Runoff of the nitrogen and phosphorus components of fertilizers leads to an oxygen depletion in the water. This depletion has caused massive fish die-offs and can wipe out whole areas of marine habitat necessary to maintain the life cycles of myriads of species of aquatic life.

Marine debris is a visible expression of human impact on the marine environment. Debris is more than an aesthetic problem, it poses a real danger. Ocean currents carry milk cartons, toothbrushes, cigarette lighters, and other familiar plastic items around the world. In some areas, such as the Central Pacific Gyre, plastics outnumber plankton seven to one. The number of marine mammals that die each year due to ingestion and entanglement of debris approaches 100,000 in the North Pacific Ocean alone. Worldwide, 82 of 144 bird species examined contained small debris in their stomachs. Plastic is the most far-reaching man-made threat facing many marine species. Over time, it reacts with sunlight and turns into small plastic polymer molecules. It turns out that these plastic polymers are sponges for DDT, PCBs and other toxins that don’t dissolve in seawater. Plastic pellets have been found to accumulate up to one million times the level of these poisons that are floating in the water itself. These pellets are consumed by baitfish, which in turn are consumed by larger fish, eventually finding their way into the stomachs of large predators, such as dolphins and toothed whales, and our own.

Other human activities, such as the construction of shipping channels and marinas, and the recreational use of coastal areas, including resort development, are likely to have a negative impact on the lives of whales and dolphins using the same areas.

Last but not least, climate change, with its changes of sea temperature, sea level rise, changes in salinity, just to name a few, will undoubtedly change the socio-ecology of whales and dolphins. Species inhabiting the high latitudes, such as bowhead, narwhal, beluga may be the first to feel the impact due to diminishing food resources, such as krill. But other species, such as humpback whales and killer whales will likely experience significant changes in their food supply, resulting in changes of existing migration patterns and a shift of home ranges.

Whales and dolphins are facing enormous challenges and threats. They are the ocean canaries, warning us about the disastrous effects of pollution and habitat destruction, and they can be our guides to where to look for answers about how our oceans work. If we have any philosophical leanings towards preserving these wonderful creatures and the oceans, either for future generations or for its own value, than learning enough to prevent any further damage is crucial.

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