biology, geography, learning, oceanography, weather

Red tide still affecting many southwest Florida beaches (H. Michael Mogil, CCM, CBM, DMS)

For weeks, a “red tide” (such tides are also referred to as a “harmful algal bloom” or HAB) has affected many beaches from Lee County, FL northward. With the departure of Hurricane Matthew a little over a week ago, the HAB was pushed southward and eastward, finally reaching beaches in Collier County. A day earlier (Fri., Oct. 6, 2016), news reports from Sarasota, FL indicated that with increasing winds and winds blowing from land to water (the approach of Matthew), the tide in its area would likely lessen. Unfortunately, the tide had to go somewhere. On Sat., Oct. 7, 2016, the HAB’s smelly signature arrived in Naples, FL. The tide has since returned to Sarasota area beaches, as well.

According to Florida’s Fish and Wildlife Conservation Commission, a “red tide is a naturally-occurring microscopic alga that has been documented along Florida’s Gulf Coast since the 1840’s and occurs nearly every year. Blooms, or higher-than-normal concentrations, of the Florida red tide alga, Karenia brevis, frequently occur in the Gulf of Mexico at this time of year (late summer or early fall). Red tide begins in the Gulf of Mexico 10 to 40 miles offshore and can be transported in (to) shore by winds and currents.”

fig001-san-diego-area-algal-bloom-imageAs the name “red tide” suggests, this bloom of algae often turns the water red (Fig. 1).

A HAB has two potential components. First, according to NOAA’s National Ocean Service (NOS), are the harmful toxins that some (not all) algal blooms create. Florida’s “red tide” bloom is of the type that can kill fish and make shellfish dangerous to eat. These same toxins may also make the surrounding air difficult to breathe. Both of these can have local economic impacts (fishing and tourism).

Another way the algal bloom (even without the presence of harmful toxins) can harm marine life involves the natural end-of-life of the bloom. According to NOS, “…when masses of algae die and decompose, the decaying process can deplete oxygen in the water, causing the water to become so low in oxygen that animals either leave the area or die.”

fig002-dead-fish-at-vanderbilt-beach-naples-161007Either way, with onshore winds and/or an ocean current with a coastward component, there is the potential for dead fish to wash up on the beach (as I personally witnessed 10 days ago on a north Naples beach). The presence of hundreds to tens of thousands of dead fish makes a beach a very unattractive and very odiferous place to visit (Fig. 2). This setting can easily ruin vacations and impact a local area’s tourism industry.

Local agencies and volunteers often work quickly to clean up the dead fish. However, as long as the tide sits nearby, fish deposition on the shore often continues.

fig003-sfl-watch-warning-map-161017-0630amedtCurrently, the National Weather Service (NWS) offices in Miami and Tampa Bay have posted “beach hazards statements” advising of the HAB’s potential human impacts through this Monday evening (Oct. 17, 2016) along many southwest Florida beaches (including those in Collier, Pineallis, Sarasota and Manatee counties). See Fig. 3 for affected areas in southwest Florida.  These statements note that, the red tide affecting the area may cause, “…possible respiratory irritation in some coastal areas. The irritation can include coughing, sneezing, and/or tearing eyes.” The statements further note that, “…people with respiratory conditions such as asthma, emphysema and other pulmonary diseases may be more sensitive (to these conditions).” The statements also urge people to check out current “red tide” conditions at the following web sites:

http://tidesandcurrents,noaa.gov/hab

http://mote.org/beaches

http://myfwc.com/redtidestatus and consider visiting nearby unaffected beaches.

For health information, people should check with their physician, as appropriate. People can also get medical information at the floridahealth.gov web site or by calling the Poison Control Center at 1-800-222-1222

For links to “red tide” conditions across other coastal states, visit NOAA’s “red tide” web site.

© 2016 H. Michael Mogil

Originally posted 10/17/16

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