Brief Note: Limu Rash Perhaps?
RH Bennett PhD
Applied Life Sciences LLC
For some time now, people have been asking me why kids are getting strange rashes right after playing in the shallow waters of our beaches. In particular, the reports are most common regarding Kohanaiki Beach Park aka Pine Trees.
I asked people to take a photo with your smartphone and text it to me. A few weeks ago some images arrived. The images showed as diffuse rash as if something had made contact with the skin. Dermatologists aka skin doctors have a term called contact dermatitis, to suggest the source of the rash originates from without and not from within like some allergic-type skin rashes.
We know that our ocean waters are contaminated with Staph. The hot or pathogenic strains of Staphylococcus aureus can cause skin infections. Such infections often cause pustules and larger abscesses. Paddlers and surfers in Hawai‘i are well aware of this problem. The rashes reported to me do not have the appearance of Staph infections. While we should not make a diagnostic decision based solely on appearance, the images are reasonably different and suggestive of the different types of problems.
The suspect limu is a filamentous cyanobacterium Lyngbya majuscule. This is an organism common to tropical waters the world around. It is common to Hawai‘i and was first documented to cause skin rashes on people recreating in the ocean decades ago.
In subtropical Moreton Bay Australia, the problem was so prevalent; it became an economic concern for tourism. We might take heed. Fortunately, the Queensland government took the issue seriously, and as
|Staph. Aureus Pustules|
a result of their work, we know a fair bit about this recreation hazard.
In Hawai‘i, the presence of Lyngbya appears to more common in the warmer summer months. However, from the Australian work, it seems that when the combination of higher, iron, nitrate and phosphate concentrations in the ocean water occur, a Lyngbya bloom is more likely.
Readers of this blog realize that the near coastal waters in Hawai‘i and specifically the Kona Coast, are nitrogen enriched and many locations are phosphate enhanced as well. Iron is available to as it is a common component of lava and blue rock. Thus it seems our water is well fertilized and most suitable when the water temperatures peak in the summer. Perhaps during the El Nino summer, we had a few years ago the Lyngbya may have thrived.
As summer approaches there are a few things we can do, especially for the kiddies that like to play in the nearshore pools.
v Try to avoid tide pools that have filamentous algae or Limu present
v Rinse off quickly if filamentous Limu makes contact with the skin
v The filaments break off easily in rougher surf and handling and can become trapped under the bathing suit. Rinse there well too.
v If a rash occurs, usually within 12 hours, wash it thoroughly with warm water and mild soap. Some physicians recommend treating the site like a sunburn.
v Should the rash be extensive or locally very severe, seek medical attention and don't forget to mention Limu Rash to the healthcare provider.
Protecting the beaches
Readers of this Healthy Hawaiian Oceans Blog will understand we have a nutrient problem. Too much of OUR nitrogen and phosphorus is moving with the groundwater into the sea (Dailer 2010). We can say with a scientific certainty where ever we feel cold water entering or emerging in the sea that water is nutrient rich (Johnson 2008).
At Kohanaiki the nearshore anchialine ponds are far greener today then they were 15 years ago when it was undeveloped. Fertilizers applied to grass areas are known to leach out and move downslope with rain and irrigation water. It is logical to assume that the waters in the ponds are enriched and thus so green. As the tide rises and falls water flows into the sea and if temperatures are conducive the Limu will respond and grow. Furthermore, when there are sufficient nutrients, the Lyngbya makes more toxins. This toxin enhancement may help account for this growing concern.
Ahern, Kathleen S., Colin R. Ahern, and James W. Udy. "In situ field experiment shows Lyngbya majuscula (cyanobacterium) growth stimulated by added iron, phosphorus, and nitrogen." Harmful Algae 7.4 (2008): 389-404.
Dailer, Meghan L., et al. "Using δ15N values in algal tissue to map locations and potential sources of anthropogenic nutrient inputs on the island of Maui, Hawai ‘i, USA." Marine Pollution Bulletin 60.5 (2010): 655-671.
Johnson, Adam G., et al. "Aerial infrared imaging reveals large nutrient‐rich groundwater inputs to the ocean." Geophysical Research Letters 35.15 (2008).
Lyngbya Distribution and Growth Conditions