Harmful Algal Blooms Intoxicate Marine Animals
At least some sea animals that regularly feed on the algae seem to experience a temporary high.
Toxins released by harmful algal blooms (HABs) can poison and even kill humans who mistakenly ingest them, but at least some marine animals that regularly feed on the algae seem to experience a temporary high that causes them to swim faster and in an abnormal pattern.
The unusual reaction, reported in the journal Proceedings of the Royal Society B, suggests that HAB toxins affect animals differently. But, they can lead to similar, fatal consequences: However enjoyable the intoxication might be for marine animal consumers, the condition makes them more vulnerable to predation.
The study's lead author Rachel Lasley-Rasher, of the University of Maine's School of Marine Sciences, told Discovery News that the intoxication increases encounter rates with predators in two ways.
She explained: "First, they have a higher probability of encountering predators simply because they are covering more 'new ground.' If you walk around the block for 20 minutes, you are likely to encounter more neighbors than you would if you paced back and forth in your yard for 20 minutes."
"Secondly," she added, "when you move faster in the water you create a larger fluid wake. This is why you drive your boat slowly in a 'no-wake zone.'"
HABs are consumed by filter-feeding organisms such as certain fish, jellyfish, shrimp, clams, oysters and many other species. An HAB bloom recently parked off the coast of California for several months and ruined that state's crab season. Crabs ingested or were otherwise exposed to the toxins -- primarily domoic acid -- and became dangerous for people to eat.
For the study, Lasley-Rasher and colleagues Kathryn Nagel, Aakanksha Angra and Jeannette Yen focused on how HAB ingestion affects the common copepod Temora longicornis. Copepods are small aquatic crustaceans.
The researchers exposed the crustacean to Alexandrium fundyense, a microalgae that contains HAB toxins. They had no trouble getting the little animals to eat the algae. In fact, they "readily ingested" it.
Normally the crustaceans are rather low key, swimming back and forth at a slow rate. But the toxins in the algae seemed to affect them like caffeine, causing them to zip around in straight lines. (Intoxicated humans, on the other hand, are known to weave and have trouble walking in a straight line.)
The copepods remained in this state long after ingesting the microalgae. "Therefore, it appears to be a physiological response," Lasley-Rasher said, "but we still don't understand the mechanism at work."
It also remains unclear what precisely happens to the toxins as they are passed down the food chain, except that the outcome is not beneficial, especially for humans.
"Many commercially important fishes depend on copepods as a first food item when they are young," Lasley-Rasher said. "Copepods are also important in the diets of adult fishes such as herring and mackerel and also whales, such as the endangered North Atlantic right whale."
She added: "Copepods that have been feeding on harmful algal blooms can act as a vector, transferring HAB toxins to these predators."
Hans Dam, a professor with the University of Connecticut's department of marine sciences, has also studied HABs' effects on copepods in his own lab. He believes that the microalgae strain used in his studies had a higher toxin content: It caused his crustaceans to become lethargic.
"Instead [in the new study], the copepods swam faster, which can lead to increased encounter rates with their predators, and higher mortality," Dam told Discovery News. "This kind of indirect effect can actually lead to decreased fitness, and is something that is typically not considered in toxicological studies."
HABs are naturally occurring, but researchers at the National Oceanic and Atmospheric Administration and other organizations believe that human activities that disturb ecosystems likely play a role in their growing frequency and intensity.
Lasley-Rasher and her team call for additional studies on animals that consume such blooms, to better determine their impact on not only these grazing species but also on those that feast on them up the food chain.
Dogfish, along with many other animals, regularly consume algae that can harbor toxins.
Winners of the 2015 Ocean Art Underwater Photo Competition were announced this week, and they include images of rarely seen marine life. The contest, in its fifth year, attracted entrants from over 50 countries. Organized by the
, Ocean Art 2015 judges were professional underwater photographers, including the guide's publisher, Scott Gietler. The Best of Show image, which also won first place in the "Macro" category, is this photo of a larval stage eel. It was snapped at night in 4,000 feet of water off the coast of Kailua-Kona, Hawaii. Gietler told Discovery News, "These subjects are incredibly difficult to find, focus on, and light -- a true winner." Photographer Jeff Milisen explained that he took the image while "on a blackwater dive with a member of the Roddenberry family (of "Star Trek" fame) watching a parade of underwater aliens drift past when this larval cusk eel swam by. The external stomach helps the developing fish grow as fast as possible by eking every last bit of nutrition from its every meal." Milisen added, "Out of the four divers underwater that day, we had over 1000 blackwater dives under our belt and none of us had ever seen anything like it, whether on earth or boldly going elsewhere!"
Gietler says this is "one of the most unique wide-angle photos we've seen in a long time. The photographer (Francesco Visintin) captured both the jellyfish and Snell's window with impeccable lighting." "Snell's window" is a phenomenon by which an underwater viewer sees everything above the surface through a cone of light. The effect is caused by refraction of light entering water. Of the photo, taken in waters off of Tuscany, Italy, Visintin said, "(A) calm sea and unusually good visibility motivated me to explore this fascinating subject from a photographic standpoint, exploiting the soft light of the early morning and sunset."
A North Sea anemone, found deep in the waters of the Oslo Forjd, Norway, was backlit with a strobe to produce this winning shot. Photographer Lill Haugen said that "certain species of red shrimps can be found seeking shelter under this type of large, cold water anemone," which appears to dwarf the diver seen in the background.
A pod of pilot whales was the subject of this portrait image, taken in waters off of Nice, France. Photographer Greg LeCoeur said, "During a sailing day off the shore of the Mediterranean Sea, I spotted a big pod of pilot whales that accepted me in the blue water. They were turning around me in the crystal blue water. It was an amazing experience and a great opportunity to photograph them." Gietler said, "Pilot whales are notoriously shy and difficult to photograph. The sun rays and size of this pod made this portrait a clear winner."
Look closely, as this image captures a moment that has only been seen by a handful of people. A female Striated frogfish is shown rising toward the surface of water at Lake Worth Lagoon near Riviera Beach, Florida. Photographer Steven Kovacs pressed his camera's shutter at the exact moment that the female released her egg mass, above a waiting male that later fertilized the eggs. Gietler said, "Frogfish have only been photographed spawning a few times before. Capturing this type of photo takes a lot of patience and many hours in the water."
This photo of a pregnant blacktip shark ("ma' o mauri" in Tahitian) was taken during a shark-monitoring project with the French Polynesia Shark Observatory. Photographer Lauric Thiault was to capture images of tiger sharks, but had no luck during two lengthy dives at La Vallée Blanche, Tahiti. At the end of the second dive, Thiault said, "I held my breath, facing the surface and waiting for a shark to come between the sun and me." After a few attempts, this impressive female, surrounded by other sharks, "came right into the frame." Gietler said that French Polynesia is one of the few places in the world where you can see sharks in their natural environment.
Winner Simon Chiu took this photo of a filefish camouflaged in coral at Mactan in Cebu, Philippines. Gietler said, "This tiny filefish has evolved to look exactly like the small soft coral polyps that it is hiding in, but it could not help ‘peeking' at the photographer, who captured the essence of underwater cuteness."
Parental care can be a literal and figurative mouthful for marine life, as this jawfish with a mouth crammed with eggs shows. Photographer Yen Ngee Koh took the photo on a dive at Tulamben in Bali, Indonesia. Koh said, "After some frontal shots, I noticed that more eggs were spilling out on the top left side (of the jawfish's mouth). So I decided to shift more to the left and lowered the angle even more, as low as I could. I'm happy to see that it helped to showcase the mouthful of eggs even more."
Photographer Matthew Sullivan spotted this juvenile wood turtle at a mountain creek near the Bridge Waterfall in Pennsylvania. "These turtles are endangered and finding them is a privilege," Sullivan said. "Getting to photograph her in her aquatic habitat was well worth the effort of lugging all my camera gear up into the mountains.
This photo shows a glowing Cerianthus, which is a type of tube anemone. The creature, from Noli, Italy, takes on an otherworldly appearance in the image due to clever use of lighting and camera filters. Gietler explained, "Only certain subjects react to ultraviolet light underwater, and special filters on the camera are needed to truly capture the beauty."
When a predatory houndfish (also called a crocodile needlefish) nabbed a brassy chub at Ouemo Bay in New Caledonia, photographer Jack Berthomier was there to capture the moment. Berthomier likes to dive and take images in this eco-rich location. The houndfish appears to have taken in more than it could handle, however, as Berthomier never did see the predator successfully manage to swallow the fish. Sadly, the photographer also never saw the houndfish again, and suspects that in this fish-eat-fish world, it too was eaten by an even larger hunter. Houndfish are actually feared by many divers and fishermen because of their large size and ability to inflict puncture wounds with their sharp beaks.
This majestic image of a dolphin was snapped at Deshaies, Guadeloupe. Photographer Brian Christiansen had been enjoying coffee on a sailboat in this part of the Caribbean when a pod of curious dolphins swam around the craft. Christiansen said, "I dropped everything, grabbed the nearest camera, mask and maybe a fin, and jumped in. The pod seemed like one family group with an obvious matriarch who had a young one." He continued, "The ones I spent the most time with were two adolescents who were nonstop playing with each other and me. The compact camera worked well in this situation because I could easily play with the dolphins until in the right position, and then snap off a few pictures just the way I imagined." Gietler said, "Most people are familiar with a solar eclipse, but this photographer experienced a 'dolphin eclipse.'"
Nudibranchs are soft-bodied marine mollusks, aka sea slugs, known for their bright colors and striking forms. They are so photogenic that an entire category is devoted to them in the Ocean Art contest. Gietler said, "Sea slugs are normally photographed with a macro lens, but this photographer was able to capture a beautiful photo of the animal with stunning sun rays behind by using a wide-angle lens." The image was taken in waters off the north coast of the Balearic island Minorca in the Mediterranean.
Gietler said, "What happens when you mix an artistic vision with great photography and Photoshop skills? Dancing Manatees, of course." Creator Dennis Vandermeersch came up with the idea in Florida as he "was swimming with these gentle creatures. They were in mating behavior, so it looked like a dance." The shot is actually an artistic composite of multiple images taken in Florida, Belgium and Abu Dhabi, which is the capital of the United Arab Emirates. Vandermeersch, however, said that "imagination shouldn't know any borders or boundaries. Let it run free!"