Poster Abstracts: Gulf Coast Science Conference
2: Climate Variability and Change
Ocean Acidification and Coral Reef Communities
Ilsa B. Kuffner, Andreas J. Andersson, Paul L. Jokiel, Ku‘ulei S. Rodgers, and Fred T. Mackenzie
U.S.Geological Survey, Florida Integrated Science Center, St. Petersburg, Florida
Laboratory studies predict that calcification rates of reef organisms will decrease within the next century due to ocean acidification (OA). The effects of OA on ecological processes, such as recruitment and competition for space, are relatively unstudied. Theoretically, calcifying organisms will be less competitive in a high-pCO2 world because the rate at which they build their skeletons to occupy space will be reduced. We conducted a nine-month experiment to measure the effects of OA on Hawaiian reef community development, including corals and other calcifying and non-calcifying algae and invertebrates. Six outdoor mesocosms continually received non-filtered seawater from the adjacent reef flat. Three were controls with ambient seawater only, and three were with pCO2 levels exceeding ambient daytime conditions by 365 ±130 µatm. The treatment mesocosms experienced daytime levels of pCO2 predicted for the year 2100 under a business-as-usual climate-change scenario. Recruitment rate and space occupation by crustose coralline algae were severely inhibited in high-pCO2 mesocosms, with a 78% and 92% reduction, respectively, compared to control mesocosms. We propose that accounting for the replacement of calcifying organisms by those that do not calcify, rather than simply extrapolating measurements of decreased calcification rates, will be necessary to predict future carbonate-accretion rates in the face of OA. The results of our study are relevant to carbonate production on Florida reefs and other carbonate-producing systems.
Contact information: Ilsa Kuffner, U.S. Geological Survey, Florida Integrated Science Center, 600 4th St. South, St. Petersburg, Florida 33701; phone: 727-803-8747; email: ikuffner@usgs.gov
Freeze Tolerance of Mangroves and Their Distribution Along the Northern Gulf of Mexico Coast in Response to Climate Change
Thomas C. Michot1, Carrie M. Curelariu2, Richard H. Day1, Christopher J. Wells1, Thomas W. Doyle1
1 U.S.Geological Survey, National Wetlands Research Center, Lafayette
2 Biology Department, University of Louisiana, Lafayette
Three species of mangroves occur in North America: black mangrove (Avicennia germinans), white mangrove (Laguncularia racemosa) and red mangrove (Rhizophora mangle). All three species are highly adapted to intertidal flooding regimes and have occurred historically throughout the Caribbean and into the southern Gulf of Mexico. Mangroves are largely freeze intolerant; thus their northern distributions are limited to subtropical, pan-Gulf environments. The southern Florida Gulf coast consists primarily of mangrove forests of all three species, with trees typically reaching 10-20 m in height. The general northward trend is toward trees of shorter stature and sparse coverage up to the northernmost range extent of the black mangrove in coastal Louisiana where, until recently, the plant rarely attained two meters in height. Historically, the northward decrease in mangrove abundance and stature is correlated with increased abundance of Spartina alterniflora and other salt marsh species. We have noted, however, an increase in coverage and height of mangroves since the last hard freeze in coastal Louisiana occurred in 1989. We hypothesized, therefore, that Global Climate Change is having a direct effect on mangrove distribution because increasing temperatures and changing freeze/drought cycle patterns allow a northward expansion of mangroves into the salt marsh zone. This expansion is a major landscape change that will likely have a significant impact on birds, fish and other species that rely on coastal vegetation, including the human population culturally and financially dependent on the subtropical marsh ecosystem.
Our study consisted of three portions: (1) an aerial survey of mangrove distribution along transects in southeastern Louisiana over a 13-month period, 2001-2002, (2) ground surveys of a single site (near Fourchon, Louisiana) over a 10-year period, 1996-2006, and (3) a greenhouse and freeze chamber experiment to investigate plant response to various temperature and duration regimes, in 2008. Our aerial survey was conducted during a period of salt marsh dieback that resulted in areas of bare, unvegetated substrate where the Spartina died back and disappeared. Many of those areas were quickly vegetated with mangroves, as our results show that the number of sample sites vegetated with Avicennia more than doubled from October 2001 (22 sites) to August 2002 (55 sites). At our Fourchon ground site we have documented that the areal coverage of Avicennia increased from approximately 7% of the vegetated area in 1993 to approximately 92% in 2000, at a rate of 4 ha/y. In our freeze chamber experiment we used at least three replicates each to test black and red mangroves at three temperatures (-5oC, 0oC, and +5oC) for five durations (1, 5, 10, 24, and 48 h). Both species had 100% survival at +5oC, all durations, although some damage was sustained for the 24 h and 48 h groups. At 0oC black mangroves showed some damage at 24 and 48 h duration but no complete mortality, whereas the red mangroves showed complete mortality at 48 h and partial damage at shorter durations of exposure. Both groups showed complete mortality at -5oC for 48 h, and mixed results for the shorter durations at -5oC. We plan to expand our studies to other parts of the Gulf coast pending future funding.
Contact Information: Tommy Michot, U.S. Geological Survey, National Wetlands Research Center, 700 Cajundome Blvd., Lafayette, Louisiana 70506; phone: 337-266-8882; fax: 337-266-8664; email: michott@usgs.gov
Climate change, carbon storage and function of Taxodium distichum swamps
Beth A. Middleton, US Geological Survey National Wetlands Research Center, Lafayette, Louisiana
Predictions can be made about the potential effects of climate change on wide-ranging ecosystems based on shifts in their function across their geographical range. Taxodium distichum is a forested wetland type that spans the southeastern part of North America, and a good candidate for climate analysis. Study sites were established in similar swamps at each of 7 latitudes in the Mississippi River Alluvial Valley from Illinois to Louisiana, to make comparisons of carbon storage and production across the climate gradient. Swamp leaf production, root production and tree height were highest in mid-range, and lower in the northern and southern parts of the range, i.e., a curvilinear pattern. Seed bank densities are generally related to temperature and precipitation levels, so that regeneration patterns may shift with climate change. A climate change model suggests that climate warming and drying could decrease the range of swamps in the western and southern part of the range. Knowledge of the response of baldcypress swamps to differences in climate across the latitudinal range can give evidence of the response of these species to climate change, and thus help lead to models that more accurately predict the distribution of these wetlands in the future.
Contact information: Beth Middleton, U.S.Geological Survey, National Wetlands Research Center, Lafayette LA 70506. Phone: 337-266-8618; Fax: 337-266-8586; email: beth_middleton@usgs.gov
Holocene Climate and Variability in the Northern Gulf of Mexico and Adjacent Northern Gulf Coast
Richard Z. Poore, Lisa E. Osterman, and Kathy Tedesco
U. S. Geological Survey, Florida Integrated Science Center, St. Petersburg, Florida
Marine records from the northern Gulf of Mexico indicate that significant multidecadal and century-scale variability was common during the Holocene. Mean annual sea-surface temperature (SST) during the last 1,400 years may have varied by 3oC, and excursions to cold SST coincide with reductions in solar output. Broad trends in Holocene terrestrial climate and environmental change along the eastern portion of the northern Gulf Coast are evident from existing pollen records, but the high-frequency details are not well known. Continuous and well-dated records of climate and climate variability in the western portion of the northern Gulf Coast are essentially lacking. A network of records from the northern Gulf Coast with sufficient age control and sampling density is needed to resolve multidecadal to century-scale features. High-resolution well-dated marine records from the northern Gulf of Mexico are also needed to determine the magnitude and spatial coherence of Holocene climate variability in this region.
Information on Holocene floods, droughts, and storm frequency along the northern Gulf Coast is limited. Records of floods may be preserved in continental-shelf sediments but establishing continuity and chronologies for sedimentary sequences on the shelf presents challenges due to sediment remobilization and redeposition during storms and floods. Studies of past storm and flood deposits in coastal lakes and marshes show promise for constructing records of past storm frequency but additional work is needed to evaluate techniques and develop regional patterns.
Contact Information: Richard Poore, U.S. Geological Survey, 600 4th Street South, St. Petersburg, FL 33701; phone:727 803 8747; email: rpoore@usgs.gov
Monitoring and Modeling of Florida Shelf Carbonate Saturation State
L. L. Robbins1, P. Knorr2, P. D. Gledhill3, M. Eakin3, S. Liu4, and R. Byrne4
1 U.S.Geological Survey, Florida Integrated Science Center, St. Petersburg, Florida
2 University of South Florida, Department of Geology, Tampa, Florida
3 NOAA Coral Reef Watch, Room 5308, 1335 East West Highway, Silver Spring, Maryland
4 University of South Florida, College of Marine Science, 140 7th Ave. South, St. Petersburg, Florida
Empirical data to evaluate how ocean chemistry is changing due to the absorption of anthropogenic carbon dioxide is severely lacking. How these changes will affect biogenic calcification rates in coastal waters is also unknown. Lack of baseline data on carbonate saturation state and pCO2 on the inner west Florida shelf, a low gradient calcium carbonate platform, inhibits the ability of managers and scientists to predict ecosystem change resulting from ocean acidification. Current saturation state models using remote sensing data are generally too coarse to be useful for the Gulf of Mexico, do not include nearshore and inner-shelf data, and lack information for specific important ecosystems, such as Florida’s coral reefs. Maps depicting pCO2 and carbonate saturation states over large latitudinal gradients are needed on the Florida shelf and for specific localities where significant decline of carbonate ecosystems, habitats, and calcifying organisms are predicted over the next decade.
To address critical information gaps and nearshore variability of carbon fluxes, the US Geological Survey (USGS) is working with the University of South Florida (USF) and NOAA to acquire baseline pCO2, pH, and alkalinity data to create a nearshore to offshore regional carbonate saturation state model for the west Florida shelf. These data are being used in conjunction with habitat data to monitor habitat change over time. Using the Multiparameter Inorganic Carbon Analyzer (MICA) developed by USF, data on air and sea pCO2, pH, and total carbon were collected during a pilot cruise west of Tampa Bay. Maps depicting carbonate saturation state of the marine water, underlying sediment, and habitat data show varying relationships in specific localities. Additional cruises are planned for summer and winter of this year.
Contact information: Lisa L. Robbins, U.S. Geological Survey, Florida Integrated Science Center, 600 4th St. South, St. Petersburg, Florida 33701; phone: 727-803-8747 x3005; fax: 727 803-2030; email: lrobbins@usgs.gov
Monitoring Coastal Louisiana Wetland Impacts from 2005 Hurricanes Using Multi-Temporal MODIS NDVI Data
Gregory D. Steyer1, John A. Barras1, Brady R. Couvillion2
1 USGS National Wetlands Research Center, Coastal Restoration Field Station, Baton Rouge, Louisiana
2 IAP World Services, National Wetlands Research Center, Lafayette, Louisiana
The coastal landscape of Louisiana was subjected to severe environmental stress from hurricanes Katrina and Rita in August and September 2005. The impacts from storm surge, which included physical conversion of marsh to open water, extensive flooding and salt water intrusion effects, varied greatly over time and space. We used a Normalized Difference Vegetation Index (NDVI) calculated from MODerate-resolution Imaging Spectroradiometer (MODIS) imagery to quantify the extent and severity of damage to vegetative communities and subsequent recovery. Species composition and total live cover field data were collected within 232 unique 4m2 plots in multiple time periods across coastal Louisiana to corroborate changes in NDVI over time. A pre-hurricane baseline dataset, using monthly average composites from February 2000 through February 2005 MODIS imagery, was created. The use of multi-year composites minimizes effects of seasonal variations and better isolates post-hurricane effects. Data from March 2005 to November 2006 were compiled on a monthly basis and compared to the baseline average to create a departure from average statistic. NDVI departures suggest over 35% of the pre-storm coastal wetland area (representing 5,009 km2) experienced a substantial decline in the density and vigor of vegetation in October 2005, with greatest amounts of damaged vegetation in the east and west regions of the Louisiana coast, corresponding to hurricane Katrina and Rita landfall areas. New open water areas formed from the immediate removal of wetland or flooding of burned marsh represent approximately 17.4%, 6.6%, and 28.2% of the immediate damage in the east, central and west regions, respectively. The percentage of area of persistent (November 2006) NDVI damage accounted for by persistent new open water in the east, central and west region was 91.8%, 81.0%, and 29.0%, respectively. The remaining damage was likely associated with other factors including saltwater intrusion, flooding and burial by wrack. These factors were most significant in the west region where hydrologic restrictions and drought conditions contributed to 1,045.7 km2 of persistent damage through the observation period. Although below average NDVI values were observed in most marsh community types through November 2006, recovery of vegetation was evident. NDVI provides a useful tool for tracking marsh changes, especially when integrated with physical landscape change assessments and field verifications as conducted in this study.
Contact Information: Greg Steyer, John Barras, USGS National Wetlands Research Center, Coastal Restoration Field Station
Contact Information: P.O. Box 25098, Baton Rouge, LA 70894. Brady Couvillion, IAP World Services, 700 Cajundome Blvd, Lafayette, LA 70506. phone : 225 578 7486; email: bcouvillion@usgs.gov
Impact of Ocean Acidification on Rates of Community Calcification and Dissolution in Coral Reef Ecosystems of South Florida, the Caribbean, and Hawaii
Kimberly K. Yates, Chris Dufore, and Nathan Smiley
U.S. Geological Survey, Florida Integrated Science Center, St. Petersburg, Florida
The severity of the impact of elevated atmospheric pCO2 and ocean acidification to coral reef ecosystems depends, in part, on how seawater pCO2 affects the balance between calcification and dissolution of carbonate sediments. Presently, there are insufficient published data that relate concentrations of pCO2 and CO32- to in situ rates of reef calcification for accurately predicting the impact of elevated atmospheric pCO2 on calcification and dissolution processes.
Rates of community calcification were measured, in situ, on representative habitat types of coral reef ecosystems in Florida Bay, Biscayne National Park, the Molokai reef flat in Hawaii, and the U.S. Virgin Islands using a benthic incubation chamber called the Submersible Habitat for Analyzing Reef Quality (SHARQ). Carbonate system parameters including total alkalinity, pH, and total carbon dioxide were measured every four hours during 24-hour incubation periods, and calcification rates were calculated using the alkalinity anomaly method. Habitat types included patch reef, seagrass, hardbottom, coral rubble, and mud substrates.
Diurnal trends in calcification rates were observed for all substrate types with calcification occurring primarily during daylight hours and dissolution of carbonate sediments observed during dark hours. Average rates of calcification for substrate types in Florida and the U.S. Virgin Islands during 24-hour incubation periods were 0.47 and 1.18 g CaCO3 m-2 for patch reefs and hardbottom communities, respectively. Seagrass and mud bottom communities showed equivalent rates of net carbonate sediment dissolution of -0.22 g CaCO3 m-2. Rates of calcification on the Molokai reef flat ranged from 0.003 to 0.23 g CaCO3 m-2 h-1, and dissolution ranged from -0.005 to -0.33 g CaCO3 m-2 h-1.
Linear correlations were calculated between calcification rates and pCO2, and calcification rates and CO32- concentrations for each substrate type. Carbonate ion and pCO2 thresholds were estimated as the concentrations of CO32- and pCO2 at which rates of calcification and dissolution were equivalent, respectively. The average pCO2 threshold for all substrate types was 585 µatm, and the average CO32- threshold was 203 µmol kg-1. Threshold values varied considerably among substrate types and on similar substrate types during different time periods. Currently, atmospheric pCO2 is approximately 380 µatm and is predicted to reach 700 µatm by the year 2100, surpassing the average pCO2 threshold for these substrate types. The results of this study indicate that a significant amount of sediment in coral reef ecosystems may be lost due to carbonate sediment dissolution.
Contact Information: Kimberly K. Yates, U.S. Geological Survey, Florida Integrated Science Center, 600 4th St. South, St. Petersburg, FL 33701; phone: 727-803-8747; fax: 727-803-2031; email: kyates@usgs.gov
SLRRP: Sea-Level Rise Rectification Program and Seawater Inundation Model under Climate Change
Thomas W. Doyle, U.S. Geological Survey, National Wetlands Research Center, Lafayette, Louisiana
The Sea-Level Rise Rectification Program (SLRRP) is a software program designed with a user-friendly interface to generate a suite of future sea-level projections from various Global Circulation Models (GCM) and emission scenario options obtained from IPCC (2001), Intergovernmental Panel on Climate Change. The SLRRP model allows the user to select a region-based tide station, GCM model, and emission scenario to generate a graph and output file of future sea-level change. Sea-level rise was modeled as a function of historic sea-level conditions at long-term tide stations based on mean monthly tide records projected into the 21st century with the addition of curvilinear rates of eustatic sea level rise expected from climate change. The historical record was retained to mimic the natural cycle of high and low tidal variation attributed to astronomical and meteorological causes. The data record was extended into the next 100 years with the addition of eustatic rates of sea-level rise based on IPCC (2001) low, mid, and high projections obtained from various global climate change models. Model simulations were achieved for each of 7 climate change models and 6 emission scenarios included in the IPCC (2001) dataset. SLRRP rectifies the historic tide record and future eustatic sea-level rise into a common datum (default = NAVD88) to facilitate comparison with landbase features and elevations. The SLRRP model generates a sea-level prediction by wrapping the historic mean monthly records for the period of record for all future years up to year 2100. A series of sequential pop-up windows is used to facilitate user selection of GCM models, scenarios, and manual entries for projecting future sea levels. The SLRRP model allows the user to manually enter a local subsidence rate and a eustatic rise by the year 2100 in lieu of model defaults. After selecting a GCM model and emission scenario, the user can specify the actual effects and components of the GCM results that include degree of glaciation and thermal expansion. The program gives the user options for saving graphical and digital formats of SLRRP predictions and generating a supplemental graph to visualize the timing and extent of yearly flooding potential for a given elevation (NAVD88). In effect, the model shows the prospective data and time period for which sea level will overtop a given landscape feature under a future changing climate. Flooding potential is the percentage of months within a year when there is inundation by seawater at a select land elevation determined by the user.
Contact Information: Tom Doyle, U.S. Geological Survey, National Wetlands Research Center, 700 Cajundome Blvd., Lafayette, Louisiana 70506; phone: 337-266-8647; fax: 337-266-8586; email: doylet@usgs.gov
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