Red tides and climate change in Tierra del Fuego

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Ushuaia sits at the edge of the world. Nestled on the largest island of the archipelago that makes up Tierra del Fuego—the southern tip of South America—the city has doubled in the last twenty years to 60,000 people. Urbanization, coupled with climate change, is having an adverse effect on the waters that permeate Tierra del Fuego and contaminating the shellfish that are a staple of the local diet.
Marcelo Hernando, a researcher at Argentina’s Austral Center of Scientific Investigations (CADIC) in Ushuaia, has been measuring the effect climate change is having on the local environment by looking at a group of algae called phytoplankton. These photosynthetic microorganisms are the marine version of a canary in a coal mine, living barometers sensitive to changes in water temperature and salinity.
“Ice coverage on the Antarctic peninsula has diminished in the last twenty years,” says Hernando. This is diluting the coastal waters of the Beagle Channel, upon which Ushuaia sits. “This decrease in salinity has important consequences on the marine ecosystem,” explains Hernando.
One of the effects he has seen is the respiration of phytoplankton pushed into over-drive, a phenomenon called oxidative stress. This reduces their ability to photosynthesize, which means they are producing less oxygen. Plankton are the primary producers in our oceans, supporting vast food webs and acting as carbon sinks. “We are seeing a decrease in the growth rate of algal communities as a consequence of lower salinity,” says Hernando. “This can alter the equilibrium of the rest of the organisms in the ecosystem.”
Marcelo Hernando and a team of researchers from all over Argentina have been monitoring the Beagle Channel since 2004 on the lookout for red tides—algal blooms that are a public health concern, especially if the community is eating from these waters.
“I’m interested in the study of toxic species that cause the phenomenons known as harmful algal blooms,” says Gastón Almandoz, a biologist at the University Nacional de La Plata in central Argentina. Almandoz works with Marcelo Hernando in the Beagle Channel and last August they published a study together on red tides in the Journal of Sea Research.
In that study, the team found 10 species of phytoplankton that were potentially toxic, which worries Almandoz. “Red tides can cause human losses through the consumption of contaminated shellfish,” he says, pointing to the popularity of ‘mariscos,’ or shellfish, in the local diet. “They may have a delicious flavor and look great, but their toxins will send anyone to the hospital.” 
Marcelo Hernando says that these algal blooms are another consequence of climate change. He’s looked at local studies that have spanned 20 years and says the biomass of the phytoplankton community has stayed constant. In the summer of 2010, however, it grew by an order of magnitude. Even Palmer Station in Antarctica detected what they called a ‘historic’ level of algal biomass in their waters.
Hernando and Almandoz’s 2011 study suggested that one likely trigger of these algal blooms is agricultural run-off caused by Ushuaia’s population boom. The human population has grown substantially since Magellan first sailed around Patagonia in 1520 and Darwin’s H.M.S. Beagle surveyed and sailed through the same waters 300 years later. Ushuaia is now a bustling port and tourism hub that must bridle its effluents if it is to keep its waters clean. 
-- Aleszu Bajak
Photo – Piffer via Flickr