U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2010–3065

August 2010

Response of Florida Shelf Ecosystems to Climate Change: 

from Macro to Micro Scales

Printed on recycled paper

Introduction

U.S. Geological Survey (USGS) research in St. Petersburg, 

Fla., is focusing attention on marine environments of the Florida 

shelf at three levels, from regional to estuarine to the individual

organism. The USGS is partnering on this project with the 

Florida Department of Agriculture and Consumer Services 

(DACS), National Oceanic and Atmospheric Administration 

(NOAA), and the University of South Florida (USF) in marine 

studies. The specific goals of these combined efforts are an 

improved understanding of the effects of ocean acidification on 

regional carbonate processes, changes in individual estuaries, 

and organism-level response (fig. 1). This understanding 

will assist in developing appropriate Federal, State, and local 

management responses to climate change in coastal areas. 

Ocean Acidification

Our research focuses on climate change impacts to the 

shallow waters of the Florida shelf. With 1,350 miles of 

coastline, productive estuaries, and sandy beaches, Florida’s 

economy relies substantially on marine and coastal resources. A 

major issue is the buffering capacity of oceans in the absorption 

of anthropogenic carbon dioxide (CO2). Excess atmospheric 

CO2 is absorbed at the ocean surface, lowering seawater pH, and 

reducing carbonate ions available to organisms. These changes 

in seawater chemistry are known as “ocean acidification.” The 

pH of the world’s oceans has declined by approximately 0.1 pH 

units since 1750. 

Scientists are monitoring seawater chemical changes, such 

as pH and the aragonite saturation state (Ωarag). These changes are 

important because they affect a range of biological processes in 

marine organisms: precipitation of calcium carbonate, fixation of 

CO2, regulation of internal pH, and uptake of nutrients.

Regional Carbonate Chemistry 

The goals of the combined regional-scale efforts are to 

determine baseline CO2 fluctuation and Ωarag and to synthesize 

existing carbon budget data for the Gulf of Mexico. USGS 

scientists are measuring pH, salinity, temperature, dissolved 

inorganic carbon and pCO2 (partial pressure of CO2 ) on 

the Florida shelf using discrete water samples and a Multiparameter Inorganic Carbon Analyzer (MICA). CO2

 fluxes 

and Ωarag on the shelf are calculated from these data (fig. 2). 

Understanding the seasonal and annual variability of carbonatesaturation states will enable researchers to more accurately 

predict long-term trends. 

Figure 1.  Water chemistry changes associated with ocean acidification

can affect carbonate processes and the survival and competitive

advantages of calcifying organisms from macro to micro scales.

Figure 2.  Preliminary contours of seasonal pCO2 flux and aragonite

saturation (Ωarag) from USGS cruises, February and August 2009.

F L O R I D A

F L O R I D A

February 2009 August 2009

pCO2 flux

 Low High

Ω

arag

 Low High Low High

 Low High

F L O R I D A

F L O R I D AF L O R I D A
Modern Estuarine Water Quality

USGS researchers are evaluating pH and other waterquality parameters from Florida DACS shellfish harvest sites. 

Ten estuaries with data records of 20 years or more are being 

evaluated and compared. Each estuary had multiple monitoring 

stations that were divided into saline to fresh categories for 

analysis. Preliminary analysis at polyhaline stations (average 

salinity 18-30 ppt) from the period of record shows significant 

time-related changes in water quality on Gulf and Atlantic 

coasts. Observed increases in temperature and salinity, and 

decreases in pH (fig. 3) may be associated with effects of 

climate change including sea-level rise, warming temperatures, 

and ocean acidification, and with alterations to freshwater 

supply and water quality. 

Simultaneous changes in pH, salinity, and temperature can 

have deleterious effects on estuarine flora and fauna, exposing

organisms to increased environmental stress and putting 

many species at a disadvantage when faced with competition, 

recovery, and adaptation pressures. Shellfish production in 

many coastal Florida counties may be affected by changes in 

water chemistry.

Figure 3.  Preliminary shellfish-harvest monitoring data around

Florida, showing significant pH decline at 7 of 10 estuaries. pH

decline was accompanied by increases in salinity and temperature.

Laboratory Studies

USGS laboratory studies focus on the organism-level 

response to determine the effects of low pH or reduced 

carbonate-saturation state on single-celled protozoa 

(Foraminifera), calcifying algae (Halimeda; fig. 4), and 

microbes. Organisms respond to environmental changes, such 

as ocean acidification, light levels, nutrients, and temperature, 

with individual physical and chemical alterations and largescale changes in productivity and distribution. 

Laboratory experiments are being conducted at realistic 

forecast levels of pCO2 in enclosed microcosms to assess the 

effects that changes in pH, pCO2, and seawater carbonate 

chemistry will have on aragonitic green algae and benthic 

foraminiferal survival, calcification rates, and shell morphology. 

The selected species are abundant on carbonate shelves around 

Florida, where their tests and segments contribute significantly 

to shelf sedimentation and beach sand. Experiments to assess 

growth, calcification, and survival rates in temperature- and 

light-controlled environmental chambers are being performed. 

Historical archived samples of Halimeda have been analyzed 

for ultra-structural changes via Scanning Electron Microscopy 

(SEM) image analysis. These archived samples are being 

compared with results revealed in laboratory experiments.

Summary

It is expected that absorption of anthropogenic CO2 will 

continue to decrease ocean carbonate-saturation state and have 

significant consequences for organisms that produce calcium 

carbonate. As climate, sea level, and ocean chemistry change, 

so too will Florida’s coastal and marine resources.

Figure 4.  Lab experiments are being conducted on Halimeda 

incrassata, a calcifying benthic green alga, to determine organismlevel response to changes in pCO2

.

Authors: Lisa Robbins, Principal Investigator, and Ellen Raabe, U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center,

600 4th Street South, St. Petersburg, FL 33701

Web sites:  FLaSH Web site go to: http://coastal.er.usgs.gov/flash/ and

USGS Ocean Acidification go to: http://coastal.er.usgs.gov/ocean-acidification/

Gulf Atlantic

SJOE WAK CKEY CIT TAM 10K SJN VOL SBR IR/SL

pH < ns < < < ns < < ns <

Sal. > > > > > > > > > ns

Temp. ns > > > > > > > > >

 < significant decrease, > significant increase, ns = not significant

Atlantic 

 Ocean

 Gulf 

 of

Mexico