# Ocean Circulation Likely to Blame for Severity of 2018 Red Tide

- Link: https://greenlivingguy.com/2019/04/ocean-circulation-likely-to-blame-for-severity-of-2018-red-tide/
- Published: 2019-04-18T23:51:52-04:00
- Author: greenlivingguy

ST. PETERSBURG, Fla. (April 18, 2019) – The harmful algae that causes red tide is
currently at near undetectable levels in Florida waters compared with the much higher
concentrations at this time last year. The red tide algae, Karenia brevis, causes
respiratory issues, is responsible for massive fish kills and is often blamed for
damaging tourism.

![](https://i0.wp.com/greenlivingguy.com/wp-content/uploads/2019/04/pexels-photo-
1974521.jpg?resize=736%2C981&quality=52&ssl=1)

While traces of the bloom are always present offshore in the Gulf of Mexico, a new
study published in the _Journal of Geophysical Research-Oceans_finds ocean circulation
made 2018 the worst year for red tide in more than a decade. 

By affecting the nutrient levels offshore, marine scientists at the University of
South Florida (USF) showed that the ocean circulation played a controlling role.
If nutrient levels offshore are high in spring due to the upwelling of deeper ocean
waters, then there tends not to be major red tide blooms along the shoreline in 
fall.  Such upwelling did not occur in winter and spring of 2018, allowing a new
bloom to form offshore in spring and summer 2018. An upwelling circulation then 
set in toward the end of July, ensuring that the newly formed bloom would be carried
to the coastline along the bottom where it reinforced what had already been in place
from 2017.  

![](https://i0.wp.com/greenlivingguy.com/wp-content/uploads/2019/04/img_7773.jpg?
resize=300%2C199&quality=52&ssl=1)

Tropical Storm Gordon temporarily disrupted the upwelling circulation, allowing 
some of the new bloom to be carried to the Florida Panhandle. After the passage 
of Gordon, the upwelling circulation then allowed the bloom to be transported offshore
at the surface to eventually be carried to the Florida’s east [coast by the Gulf](https://greenlivingguy.com/2015/02/gulf-coast-leaders-urge-end-to-constant-storm/)
Stream. Thus, the rare occurrence of _Karenia brevis_at three different locations(
Florida’s west, Panhandle and east coasts) may be attributed to the ocean circulation.

![](https://i0.wp.com/greenlivingguy.com/wp-content/uploads/2019/04/pexels-photo-
1281670.jpg?resize=736%2C981&quality=52&ssl=1)

“This further demonstrates that the ocean circulation is the major determinant of
Florida’s, _Karenia brevis_harmful algae blooms, dispelling the myth that land-based
fertilizers are to blame,” said Robert Weisberg, PhD, Distinguished University Professor
of Physical Oceanography.“While pollutants can exasperate an existing red tide, 
they are not the root cause.”

In addition to ocean circulation models, the team at USF and collaborators with 
the Florida Fish and Wildlife Conservation Commission (FWC) deployed an autonomous
underwater glider for a near month-long mission. Its sensors detected relatively
high chlorophyll and low oxygen levels near the sea floor, along with upwelling 
circulation. On-site sampling also helped pinpoint the initiation zone for all three
regions to be the middle shelf some 30 to 50 miles off the coast from north of Tampa
Bay to Sarasota Bay. 

Weisberg and his colleagues have accounted for the occurrence or lack of occurrence
of major red tide blooms in 20 of the past 25 years based on the ocean circulation
conditions. While recent sampling shows very low concentrations of _Karenia brevis_offshore,
which is not a cause for immediate concern, it is too early to speculate on what
future conditions may be. Weisberg expects to have a better idea of the possible
severity of 2019’s red tide season in mid-June.

**_Source_**_: **The University of South Florida**, established in 1956 and located
in Tampa, is a high-impact global research university dedicated to student success.
The USF System includes three separately accredited institutions: USF, USF St. Petersburg
and USF Sarasota-Manatee. Serving more than 50,000 students, the USF System has 
an annual budget of $1.8 billion and an annual economic impact of $4.4 billion. 
USF ranks in the top 30 nationally for research expenditures among public universities,
according to the National Science Foundation. In 2018, the Florida Board of Governors
designated USF as a Preeminent State Research University, placing USF in the most
elite category among the state’s 12 public universities. USF is a member of the 
American Athletic Conference._