Dead fish killed by a red tide in Sarasota, Florida, 22 August 2018. Photo: Ephrat Livni / Quartz

By Ephrat Livni
22 August 2018

SARASOTA, Florida (Quartz) – All the water birds—pelicans, egrets, cormorants—are gone.

Flies swarm the coast of the seaside city of Sarasota, Florida. Crows caw. The air stinks of death. Carpets of fish, belly-up, mouths gaping, line the shore. This is the putrid new world created by a toxic red algae bloom spanning 130 miles of the state’s west coast, which has so far killed masses of fish, 12 dolphins, more than 500 manatees, 300 sea turtles, countless horseshoe crabs, a whale shark, and the local economy.

The docks behind otherwise desirable condo buildings are surrounded by fish carcasses. The waters of the bay are dotted with them, silver and white, glinting in the hot sun, looking from a distance like the crests of thousands of small waves. At least 100 tons of sea creatures have fallen victim to the toxic bloom known as “red tide.” Meanwhile, when breezes blow the toxin inland, people cough, and reports of respiratory problems are on the rise in local hospitals.

The bloom occurs almost annually in Florida. But its effects this year have been exceptionally devastating. It’s a terrifying sight to behold, and a stark foreshadowing of what may become commonplace as climate change transforms nature and our lives. Although scientists don’t know exactly what caused this particularly vicious red algae bloom, they do believe that warming waters brought on by human-induced weather changes and the effects of building development have contributed to the ever-more extreme red tides of the last half-century.

There’s a lot of talk about the threats posed by climate change—to animals, people, and the environment. But abstract chatter is hard to fathom. We can’t really imagine what it will be like when the reality we know is replaced, and what’s beautiful turns to rot. The red tide in Florida doesn’t just make the issue of global warming visible; it’s an all-out sensory onslaught. And it’s a reminder that climate change isn’t just dangerous. It’s also going to make the world an increasingly ugly and unpleasant place.

On 13 August 2018, Florida governor Rick Scott declared a state of emergency in Hillsborough, Collier, Lee, Charlotte, Sarasota, Manatee, and Pinellas counties. The order provides added funding and resources for clean-up efforts.

But money is no match for the sea. In Sarasota, the fish carcasses pile up again soon after they’re removed. Yachts are stalled in their dockside slips. Tourists are canceling trips. The sidewalk cafes and restaurants are empty. The tourism group Visit Sarasota County surveyed local businesses and found that 90% of 77 respondents—from hotels to jet-ski rental companies to restaurants— said they had lower sales between Aug. 1-7 because of the toxic algae and resulting dead fish. Locals, too, are staying inside, hiding from the heat and stench and signs of death, hoping that the region’s most redeeming feature, the water, will become hospitable again soon.

Red tide is caused by massive blooms of the toxic organism Karenia brevis. The bloom is composed of millions of minuscule, single-celled plant-like organisms that produce chemicals as a defense, including the compound brevetoxin. […]

Fish washed up after dying in a red tide in Captiva, Florida. Photo: Cristobal Herrera / EPA

The naturally-occurring bloom’s spread seems to have been exacerbated by human activities. In the last 60 years, red tides have become more severe. Some scientists posit (paywall) that this is a result of warming waters in the Gulf of Mexico. Warm waters boost algae growth, and the Gulf’s surface temperature has warmed by about two degrees Fahrenheit since 1977, as oceans soak up more heat in the atmosphere from ever-increasing carbon dioxide emissions.

Also notable is the fact that human endeavors have reshaped the flow of Florida’s waters. Agriculture, building development, canals, levees, and dikes have all changed the way rainwater, containing phosphorous and nitrogen from farm fertilizers, is directed. The rainwater runoff now rushes into rivers and bays, and the nitrogen-laden flow coaxes algae blooms.

Another contributing factor to this year’s red tide: About a year ago, in September of 2017, hurricane Irma struck Florida. The US Army Corps of Engineers had to release loads of nutrient-ridden water from Lake Okeechobee to limit water levels at the Hoover Dike. The latest red tide began about a month later. [more]

Florida’s red tide crisis shows how climate change will make the world an ugly place


Relationship between percent occurrence of cyanobacteria in total phytoplankton biomass with water temperature and total N concentration. This figure was developed from data provided to the authors by Sarian Kosten. Details on the sampling methods used to collect the TN and temperature data may be found in Kosten et al. 2011. Graphic: Havens and Paerl, 2015 / Environ. Sci. Technol. Lett.

By Karl E. Havens and Hans W. Paerl
14 October 2015

(Environmental Science and Technology) – Because of climate change, we are at a crossroad with regard to control of harmful algal blooms, and must aggressively tackle the problem before it becomes so difficult that in many ecosystems we are faced with the option of allowing these micro-organisms to go unchecked.

Many lakes and estuaries around the world, which provide drinking water for millions of people, and support a myriad of ecosystem services, already have toxic, food web-altering, hypoxia-generating blooms of cyanobacteria. The occurrence is driven by high inputs of nitrogen (N) and phosphorus (P) to the ecosystems from human sources.(1) To reduce the frequency and intensity of noxious and sometimes toxic cyanobacteria blooms, sizable reductions of both N and P are urgently needed.(2) Yet, Climate change will severely affect our ability to control blooms, and in some cases could make it near impossible.

The longer we wait to take actions to control blooms, and the more time that climate change has to exert synergistic effects with nutrients,(3) the less likely it becomes that controls will be attained. A climate-driven change in water temperature, including both a general warming and more extremes, can modify phytoplankton community by favoring bloom-forming cyanobacteria, which are able to take advantage of warmer conditions and increasing hydrologic extremes (drier droughts, increased storm activity and greater episodic nutrient loads).(3) Further, rising temperatures are expected to increase the rate of mineralization of soil nutrients and favor more deoxygenation at the lake sediment surface, so that more nutrients are released into the water column in summer.(4) This means that for the many lakes and estuaries in agricultural watersheds, with legacy P in their soils and sediments, conditions could become much worse–again, increasing the urgency for nutrient input reductions.

Hence, climate change poses a serious, additional challenge to formulating nutrient-based bloom thresholds as part of a strategy for controlling blooms. With warmer water, achieving a desired low level of blooms in the future will require greater reductions in the inputs of N and P to lakes than is needed under the current climate conditions. Yet to date, climate change has not been factored into mitigation strategies for algal blooms.

Complicating the problem is the fact that some lakes that are not currently being targeted for nutrient reductions, because of the absence of blooms, could develop dominance by cyanobacteria and experience blooms in a warmer future, even without a further rise in nutrient inputs. As an example, using data from 143 lakes along a latitudinal gradient from Europe to South America, at lower levels of total N (TN), the frequency of occurrence of cyanobacteria is below 30% over a wide range of water temperatures, and it rises very slowly. In contrast, at a high concentration of TN, there is a rapid and nonlinear increase in cyanobacteria frequency with temperature–indicating not only a change in the composition of phytoplankton, but one that happens in a discontinuous and therefore unpredictable manner.(5) This makes anticipating a bloom threshold, and controlling blooms much more challenging.

Conditions may sometimes become so unwieldy that no currently used management strategy can handle the synergistic effects of human nutrient enrichment and warming. [more]

Climate Change at a Crossroad for Control of Harmful Algal Blooms

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