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USGS Mendenhall Postdoctoral  Research Fellowship Program

14-38. Exploring Holocene coral reef accretion rates in the Florida Keys: what drives biogenic calcification, reef accretion, and erosion in an ever-changing ocean?

We seek a postdoctoral fellow who can help unravel the mystery as to why some coral reefs in the Florida Keys continue to accrete calcium-carbonate structure while many others stopped growing sometime during the late Holocene. While it is known that coral reefs and other carbonate environments are sensitive to changes in climate, ocean chemistry, and sea level (Hubbard 1997), the thickness of Holocene reef accumulation varies considerably throughout the Caribbean region. For instance, many areas of the Florida Keys have only minimal (< 2 m) accretion above the Pleistocene-Holocene boundary, while in the Dry Tortugas it is >15 m thick (Shinn et al. 1977; Gischler and Hudson 2004). Distance from large tidal passes that allow flow through the Florida Keys from the West Florida Shelf and Florida Bay, along with antecedent topography, seems to predict well where the thickest Holocene reefs have accumulated (Shinn et al. 1977; Aronson and Precht 2006). This idea is sometimes referred to as the “inimical waters hypothesis,” as it is generally thought that the dynamic waters of these shallow water bodies are not conducive to supporting coral reef growth.  Somewhat paradoxically however, Florida Keys patch reefs inside of the turbid Hawk Channel in closer proximity to near-shore influences continue to be abundantly populated by large reef-building corals, whereas reefs on the outer reef tract have suffered high rates of coral mortality over the past few decades resulting from diseases and bleaching, and have not recovered since (Porter et al. 2002).

Recent USGS research has shown that calcification rate of a major reef-building species of coral calcifies faster in the Dry Tortugas compared to three sites in the main Keys (Kuffner et al. 2013). While the correlation between coral calcification rate of one species and reef accretion rates is intriguing, the patterns cannot be explained given current knowledge of the processes controlling reef-building, biogenic calcification, and bioerosion of reef materials. Reef-building processes are complex and span the geologic and biologic disciplines. Better understanding of relationships between depositional environment, seawater chemistry, and reef accumulation are needed to predict change in reef building and biogenic calcification processes in response to changing climate and ocean chemistry.  Predicting the behavior of carbonate systems during this century is of critical importance to national interests.  Examining the factors that have influenced reef accretion throughout the Holocene should increase our understanding of present-day change in coral reef trajectories as the oceans continue to warm, acidify, and are subjected to land-use change.

The Mendenhall Fellow will have the opportunity to conduct original studies investigating the patterns and processes controlling the development of fossil and/or extant coral reefs in the Florida-Caribbean region, with special focus on Dry Tortugas NP, Biscayne NP, and the Florida Keys National Marine Sanctuary.  We would welcome proposals within a broad area that might encompass Holocene - Pleistocene coring and interpretation, the use of recent Holocene environmental recorders (e.g., corals), or any other retrospective geologic techniques involving paleoreconstruction of climate and/or seawater chemistry and reef-building conditions. As a potential resource, the Fellow would have access to the USGS core archives, which include several hundred modern coral and fossil Quaternary cores from the Florida-Caribbean region and elsewhere (

The Mendenhall Fellow will have the unique opportunity to be a part of a multidisciplinary team with a variety of expertise in coral reef biology, carbonate geology, paleoclimate reconstruction, and ocean chemistry (see the Coral Reef Ecosystem Studies (CREST). website for details). As part of the CREST project team, the Mendenhall Fellow may participate in multi-investigator field missions throughout the Florida Keys and possibly the Virgin Islands. Late Holocene paleoclimate research is also being conducted at the USGS. In addition to researchers at the USGS, the Mendenhall Fellow will have an opportunity to interact with researchers at the College of Marine Science at the University of South Florida (USF), NOAA National Marine Fisheries, the Florida Fish and Wildlife Commission, and the Florida Institute of Oceanography.


Aronson RB, Precht WF (2006) Conservation, precaution, and Caribbean reefs. Coral Reefs 25: 441-450.

Gischler E, Hudson JH (2004) Holocene development of the Belize barrier reef. Sedimentary Geology 164: 223-236.

Hubbard DK (1997) Reef as dynamic systems. In: Birkeland CE (ed) Life and Death of Coral Reefs. Chapman and Hall, New York, pp 43-67.

Kuffner IB, Hickey TD, Morrison JM (2013) Calcification rates of the massive coral Siderastrea siderea and crustose coralline algae along the Florida Keys (USA) outer-reef tract. Coral Reefs (open access

Porter JW, Kosmynin V, Patterson KL, Porter KG, Jaap WC, Wheaton JL, Hackett K, Lybolt M, Tsokos CP, Yanev G, Marcinek DM, Dotten J, Eaken D, Patterson M, Meier OW, Brill M, Dustan P (2002) Detection of coral reef change by the Florida Keys Coral Reef Monitoring Project. In: Porter JW, Porter KG (eds) The Everglades, Florida Bay, and Coral Reefs of the Florida Keys: An Ecosystem Sourcebook. CRC Press, Boca Raton, FL, pp 749-769.

Shinn EA, Hudson JH, Halley RB, Lidz B (1977) Topographic control and accumulation rate of some Holocene coral reefs: South Florida and Dry Tortugas Proc 3rd Int Coral Reef Symp, Miami, pp 1-7.

Proposed Duty Station: St. Petersburg, FL

Areas of Ph.D.: Marine geology, carbonate geology, paleoclimatology, oceanography, or related fields (candidates holding a Ph.D. in other disciplines, but with extensive knowledge and skills relevant to the Research Opportunity may be considered).

Qualifications: Applicants must meet one of the following qualifications - Research Geologist, Research Oceanographer, Research Physical Scientist.

(This type of research is performed by those who have backgrounds for the occupations stated above.  However, other titles may be applicable depending on the applicant's background, education, and research proposal. The final classification of theposition will be made by the Human Resources specialist).

Research Advisor: Ilsa Kuffner, 727-803-8747,

Human Resources Office Contact: Junell Norris, (303) 236-9557,

Go back to Summary of Opportunities

U.S. Department of the Interior, U.S. Geological Survey
URL: Kuffner.htm
Direct inquiries to Rama K. Kotra at
Maintained by: Mendenhall Research Fellowship Program Web Team
Last modified: 17:58:07 Tue 23 Jul 2013
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