Bocas del Toro Research Station

Research Projects

Katie Cramer

STRI Short-Term Fellow (2007)
STRI Pre-doctoral Fellow (2008-2009)

PhD Student at Center for Marine Biodiversity and Conservation, Scripps Institution of Oceanography, University of California at San Diego
Historical changes in coral communities in Caribbean Panama and the land-use connection

Sadly, Caribbean coral reefs are among the most degraded reefs on the planet. The animals which are the physical and ecological foundation of coral reef ecosystems, the corals themselves, have declined greatly in abundance over the past half-century. Multiple human-caused disturbances are responsible for the loss of corals, including overfishing, land clearing, and climate change. Centuries of overfishing have depleted herbivorous reef fish populations, resulting in an increase in the abundance of macroalgae, a major coral competitor. Land use activities such as agriculture and urbanization have washed materials such sediments and pollution onto reef waters. These materials are harmful to coral growth and reproduction, and also stimulate the growth of macroalgae. As a result, many Caribbean reefs that were once dominated by corals are now dominated by algae.

Acropora cervicornis, left and Porites porites spp., right)

Acropora cervicornis, left and Porites porites spp., right)

Because different coral species have varying tolerances to environmental disturbances, changes in coral species composition have recently been observed that are unprecedented on geological time scales. My research aims to reconstruct the coral community composition of reefs from the past few centuries by collecting and analyzing the calcium carbonate skeletons of dead coral colonies. This material is abundant within the sediments surrounding the present reef, and allows me to determine the baseline state of coral communities before the onset of major human disturbances.

Agaricia tenuifolia

Agaricia tenuifolia

My research focuses on the Bocas del Toro (western Panama) and Bahia Las Minas/Costa Arriba (central Panama) regions, at reef sites that span a range of influence from land-based runoff. The work involves conducting an underwater archeological dig of sorts: excavating large pits near the living reef and collecting dead coral skeletons at discrete layers (“time horizons”) within these pits. I am also surveying the present reef to compare coral community composition of past horizons with that of the present. My study aims to answer the following questions:

  1. When and how did coral communities change in Caribbean Panama over historical time scales?
  2. How much of the change in community composition can be attributed to land-based activities?
Excavating rubble from circular (60cm-diameter) pit

Excavating rubble from circular (60cm-diameter) pit

My preliminary results from Bocas del Toro show:

  1. A dramatic decrease in coral diversity occurred over the past few decades
  2. An increase in the relative abundance of weedy, low-relief species and disturbance-tolerant massive species was accompanied by a decrease in relative abundance of branching species
  3. For those species whose relative abundance has changed most, measures of influence from land-based runoff such as distance from the mainland and from rivermouths partially explain this change.

Future work will entail radiocarbon dating coral samples from the different time horizons to assess when changes occurred on reefs as well as chemical analyses of sediments within each horizon to link the timing and extent of changes on reefs with the relative exposure of the reef to land-based runoff.

Examples of coral rubble excavated from sediments surrounding present reef.

Examples of coral rubble excavated from sediments surrounding present reef.


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