Fresh Water Skin Disease (in Dolphins and Whales)

Dolphins and whales are used to living in salty seawater. Their skin is adapted to a saline environment. So, what happens when they are exposed for extended periods of time to water with lower than normal levels of salt, a situation called hypo-salinity?

Their skin cannot cope with those alien levels of salinity and severe skin lesions and ulcers will develop.

The problem is called fresh Fresh Water Skin Disease (FWSD) and is a disease of marine cetaceans in coastal and estuarine environments. It has been observed in dolphins that were displaced into freshwater lakes, and in normally-salty lakes and estuaries where salinity has dropped suddenly due to flooding or extensive rains during a prolonged tropical cyclone season[1].

The symptoms of Fresh Water Skin Disease (FWSD) are widespread skin lesions and ulcers. Chronic lesions may have overgrowths of algal and/or fungal mats. Extended exposure can lead to over-hydration, electrolyte imbalance, organ failure, and death.

At the moment, the syndrome has been observed with
[1] bottlenose dolphins (Tursiops truncatus) in Lake Pontchartrain (Louisiana, USA), a brackish lagoon, from 2007, that were thought to have been trapped by Hurricane Katrina in 2005[2];
[2] Burrunan dolphins (Tursiops australis), living in the Australian Gippsland Lakes in 2007. The sudden decrease in salinity was the result of heavy downpours after a slow build-up of salinity levels after during ten years of drought;
[3] Indo-Pacific bottlenose dolphins (Tursiops aduncus) at the Australian Swan Canning Riverpark (Swan and Canning rivers) in 2009[3];
[4] common bottlenose dolphin (Tursiops truncatus) in Texas following Hurricane Harvey in 2017;
[5] Chilean dolphins (Cephalorhynchus eutropia) in waters off Patagonia (Tierra del Fuego);
[6] Guiana dolphins (Sotalia guianensis) in coastal waters off Brazil;
[7] humpback whales (Megaptera novaengliae) in the Pacific Ocean off northern California (USA)[4].

Climate changes, whether the result of global warming or of global cooling, is resulting in more extreme weather patterns. Which means the problems of those dolphins and whales are just beginning and much worse is to come.

[1] Guignan et al: Fresh water skin disease in dolphins: a case definition based on pathology and environmental factors in Australia in Scientific Reports – 2020. See here.
[2] Mulin et al: Common bottlenose dolphins (Tursiops truncatus) in Lake Pontchartrain, Louisiana, 2007 to mid-2014 in National Oceanic and Atmospheric Administration (NOAA) – 2015. See here.
[3] Holyoake et al: Technical report on the Bottlenose dolphin (Tursiops aduncus) unusual mortality event within the Swan Canning Riverpark, June-October 2009 in ResearchGate – 2010
[4] Gulland et al: Health assessment, antibiotic treatment, and behavioral responses to herding efforts of a cow-calf pair of humpback whales (Megaptera novaeangliae) in the Sacramento River Delta, California in Aquatic Mammals – 2008

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