“Anything that can leave has, and anything that couldn’t leave has died.” – Heather Barron, head veterinarian at Florida’s Clinic for the Rehabilitation of Wildlife (via National Geographic)
Florida has the reputation for being a paradise – nicknamed the sunshine state, it is also the birthplace of Walt Disney World. Additionally, the surrounding waters host one of the largest coral reefs in the world, home to a myriad of unique and biologically diverse marine life. Over the last year however, the white sands of Florida’s picturesque beaches have become mass graveyards for thousands of fish, dolphins, turtles and manatees. The cause? The deadly red tide.
The Florida red tide – named after the rusty red colour of the water – is a toxic algal bloom most often caused by the microscopic alga Karenia brevis (K. brevis). Documented as far back as the 1500s, red tides commonly occur in southwest Florida for several weeks in the autumn. During this time, millions of K. brevis produce lethal toxins that can cause neurological, gastrointestinal and respiratory dysfunction. Following this natural phenomenon, marine populations generally recover well with no known lasting effects on the underwater ecosystems. However, the red tide may also pose a threat to human health as the toxin can become airborne with short-term exposure leading to mild airway irritation. The effects of long-term exposure are unknown.
The current red tide began in November 2017. It has now spread across more than 120 miles of the Floridian west coast and miles offshore, carrying a trail of death and destruction in its waters and triggering the declaration of a state of emergency. Despite intense rescue and rehabilitation efforts, wildlife officials and conservationists focus have shifted to carcass recoveries.
The precise cause of the red tide remains unknown as K. brevis is always present in the waters around Florida in low concentrations. However, scientists have suggested that the seasonal changes in water salinity, temperatures and light levels provide optimal conditions for the initial bloom. Yet, understanding why exactly the red tide has devastated marine life for almost 13 months is of great importance and urgency. Is the intensity of the red tide entirely natural or may humans be influencing this biological phenomenon?
To sustain an algal bloom, the algae require a nutrient-rich environment and many researchers believe this is delivered to the sea through the agricultural runoff of fertilisers. Strengthening this view, the most extensive red tides have been documented following powerful hurricanes, including hurricane Katrina in 2005 and hurricane Irma in 2017. The mass flooding caused by these storms led to tonnes of water and runoff from surrounding rivers and farmland to drain into the sea. Therefore it has been suggested that policy-makers and agriculturalists should do more to minimize potentially damaging fertiliser runoff in these environmentally sensitive areas.
What does the future hold? For now, scientists will continue to monitor the water toxicity of Florida’s west coast, whilst persisting with marine rescue operations to salvage and rehabilitate as many animals as possible. In the long-term, scientists from Mote Marine Laboratory and Aquarium are currently undertaking a pilot study using the inorganic molecule ozone – composed of three oxygen atoms – to destroy the K. brevis and its powerful toxins. However, the effects this has on the wider biodiversity will have to be carefully examined.
After a year, the red tide shows no sign of letting up. In light of this, it is imperative that we question the effects of all man-made destruction of wildlife on our delicate marine ecosystems across the globe.
Image credit: psyberartist via Flickr