2014 GSA Annual Meeting in Vancouver, British Columbia (19–22 October 2014)

Paper No. 43-7
Presentation Time: 10:30 AM

PRELIMINARY GROWTH AND TRACE ELEMENTAL CHARACTERIZATION OF RHODOLITHS (LITHOTHAMNION SP.) FROM THE GULF OF PANAMA, PANAMA


SLETTEN, Hillary R., Department of Geological Sciences, University of Alabama, 201 7th Ave, Room 2003 Bevill Bldg, Tuscaloosa, AL 35487, ANDRUS, C. Fred T., Geological Sciences, University of Alabama, 2003 Bevill, Tuscaloosa, AL 35487, GILLIKIN, David P., Department of Geology, Union College, 807 Union St, Schenectady, NY 12308 and HALFAR, Jochen, Chemical and Physical Sciences, University of Toronto, Mississauga, 3349 Mississauga Rd N, Mississauga, ON L5L 1C6, Canada, hrsletten@crimson.ua.edu

Rhodoliths, free-living forms of coralline red algae, are an important proxy resource for understanding short and long-term environmental trends in tropical to arctic oceans. Coralline algae produce accretionary, high-Mg skeletons which contain no ontogenetic growth trends, thus permitting the measurement of time series elemental data profiles that may serve as useful proxies for a range of environmental variables. Tropical rhodoliths (n=196) of the Lithothamnion sp. were collected near the southern extent of the Archipelago de Las Perlas, Gulf of Panama via SCUBA diving to test how elemental uptake changes with altered conditions in pH and other environmental parameters related to skeletal growth. For the total sample population, rhodoliths were highly branched and classified as predominantly spheroidal (30.61%) and spheroidal-discoidal (29.08%) with the remaining 40.31% falling into variable categories of spheroidal-ellipsoidal according to the Sneed and Folk (1958) classification scheme. Sizes ranged from 1.5-6.65 cm and average wet weight was 14.4 g. Alizarin Red S (ARS) stain was used to study growth rates for 60 samples randomly selected for mesocosm experiments. Algal growth post-ARS has offered insight into growth rates, sample age, and increment periodicities. To date, samples PRE-028 and PRE-006 have been measured with growth rates of 1.92 µm d-1 and 1.95 µm d-1, respectively, and total sample ages of ca. 13.4 yrs BP and 16.0 yrs BP. Initial tests using LA-ICP-MS indicate that measurable trace elemental patterns (e.g. P and Mn) are present and were analyzed to assess potential environmental variations.