Factors Influencing Settlement Patterns on the Barnacle Chthamalus panamensis

Undergraduate #267
Discipline: Ecology Environmental and Earth Sciences
Subcategory: Ecology

Kelvin J. Santana Rodriguez - University of Puerto Rico at Humacao
Co-Author(s): Ariana Gaskin, University of Idaho Rachel Collin, Smithsonian Tropical Research Institute, Panama

The gregarious settlement of dominant intertidal organisms, such as barnacles, is essential for recruitment and it’s a critical determinant in the structure of the adult population. However, the recruitment density of larvae is largely dependent on physical and temporal factors, which interact dynamically in the intertidal. The barnacle, Chthamalus panamensis, found on the Pacific coast of Panama is a dominant organism that has higher settlement during neap tides than spring tides. In this study, diel cycles, substrate composition, and other physical parameters (temperature, wind direction, wind speed, and tide amplitude) were studied during the summer 2016 to understand the settlement behavior of this species, particularly during the quarter moons. A total of 16 plates were made using 3M Safety Walk black and grey tapes. The plates were deployed in the intertidal every low tide and replaced after the next high tide for two weeks. An iButton was used to measure the temperature of the rocks and wind data was recorded by the STRI’s physical monitoring tower database. We expected that C. panamensis would have higher settlement at night, as it is when the zooplankton vertical migration typically occurs. Settlement of C. panamensis was higher during diurnal than nocturnal neap tides, which correlated with the warmer temperatures that occur during the day. We expected that bigger tidal amplitude and stronger inshore winds would enhance settlement rate, since this would provide transport and onshore delivery of more planktonic larvae. However, wind speed and wind direction had no significant effect on settlement, while lower tidal amplitude positively correlated with higher settlement rates. As for substrate composition, color was not a strong driving factor for substrate selection since there was no significant difference in settlement rates between the different colored plates. For substrate texture however, settlement was higher on plates with more abrasive sandpaper-like texture that had a more even microstructure. This study provides a better understanding in the settlement patterns of C. panamensis and the insight that is gained when considering the interactions among temporal, physical and hydrodynamic conditions that exhibit the intertidal ecosystem.

References: Jacinto, D., & Cruz, T. (2008). Tidal settlement of the intertidal barnacles Chthamalus spp. in SW Portugal: interaction between diel and semi-lunar cycles. Marine Ecology Progress Series, 366, 129-135.
Shanks, A. L. (1986). Tidal periodicity in the daily settlement of intertidal barnacle larvae and an hypothesized mechanism for the cross-shelf transport of cyprids. The Biological Bulletin, 170(3), 429-440.
Tapia, F. J., & Navarrete, S. A. (2010). Spatial patterns of barnacle settlement in central Chile: Persistence at daily to inter-annual scales relative to the spatial signature of physical variability. Journal of Experimental Marine Biology and Ecology, 392(1), 151-159.

Funder Acknowledgement(s): Gratitude is owed to my advisor Rachel Collin for her guidance and support. I want to thank my partner Ariana Gaskin and the rest of the Collin Lab members for their help. This work is only possible through the generosity of STRI and the financial support of the NSF’s REU program; grant number 1359299.

Faculty Advisor: Rachel Collin, CollinR@si.edu

Role: I carried out along with my partner Ariana Gaskin the preparation of the equipment and all the fieldwork required to collect the settlement rate and physical monitoring data.