Dataset: (DRAFT) Individual oyster results from reciprocal transplant experiment

A reciprocal transplant experiment was conducted at two sites in an estuary in NE Florida, USA that encompassed different environmental (salinity, aerial exposure) and biotic (predators) stressors.  Juvenile oysters were reciprocally transplanted within and between the two locations. At each location, the home and away oyster ‘demes’ were randomly assigned between a predator exclosure and a control treatment. After one month and then again at nine months, the individual traits (shell length, shell thickness, and condition index) of the oysters were measured and destructively sampled. (Note: multiple oysters observed for each experimental unit/cage)

Spat Collection: Oyster spat that had naturally settled out on dead oyster shells were collected from reefs in two zones of the Guana Tolomato Matanzas National Estuarine Research Reserve (GTMNERR). The zones were the Butler site at 29.77002 N, -81.2641 W, and the Pellicer site at 29.62923 N, -81.2144 W. Shells containing living, juvenile oysters were selected, and the spat (1 to 3) were marked using fingernail polish (red, blue, purple).  Initial sizes (length from umbo to tip) of all spat were recorded prior to outplant. 

The shells containing the living juvenile oysters were attached to a 2 x 2 inch square of bird netting using 2-part marine epoxy.  These dead shell and bird netting combinations were attached to a 1 ft length of PVC using cable ties threaded through the mesh to obtain the density of three spat per PVC length (“oyster pop”). All PVC posts were marked with unique numeric identifiers, and each held three oysters from a single deme.  

Cages: Three spat from one of the locations (either Butler or Pellicer) were placed in each experimental unit (cage or control). Cages were 12” X 12” X 12” made from Industrial Netting (Product Number XB1132). The bottom of the cage was open and buried into the ground. Half-inch PVC pipes 12” long were cabled tied to the inside corners of the cage to give it some stability. The control plots consisted of four PVC posts hammered into the ground 12” apart from each other. Cages were deployed in the vertical midpoint of the reef at both Butler and Pellicer zones to allow for the reciprocal transplant design.

Growth measurements: Each of these experimental units contained posts that were removed one month after deployment (Sept. 2019) and three posts removed after nine months (May 2020). Those time periods correspond approximately to a post-settlement/juvenile stage (vulnerable to mud crabs), and an early adult stage (preferred by crown conch), respectively. At each sampling period, the oysters attached to the sampled post were removed, brought to the lab, and processed to quantify two fitness components: survival (live or dead) and growth (final – initial shell length).

Oysters were destructively sampled at two time points to determine growth and survival. One out of three oysters was selected for initial processing and crushing. One of three oysters were frozen in plastic bags in a standard freezer (-18 degrees C) for further processing (reciprocal_transplant_individual_metadata), and one of three were initially processed and set aside.

In the lab, oysters were removed from the freezer and allowed to thaw on the countertop. Thawed oysters were measured for total height and width, then shucked.  The top valve (shell) and oyster tissue were placed in weighing tins. Wet weights of both were obtained using a Mettler Toledo NewClassic MS balance. Length, width, and thickness of the top valve were measured with digital calipers (Rexbeti 0-1" digital micrometer). Oyster tissue and top valve were placed in a drying oven at 60 degrees C for 72 hours (at which point they were fully dry), and then dry weights of both were recorded.

Each trait (mass, tissue mass, and shell thickness) was standardized by dividing by oyster length; hence standardized shell thickness is dimensionless.