Florida State University Libraries 2016 The interactions of a marine bivalve, Arca zebra, with its epibionts Melissa Marieta Olguin Follow this and additional works at the FSU Digital Library. For more information, please contact [email protected] 1 THE FLORIDA STATE UNIVERSITY COLLEGE OF ARTS AND SCIENCES THE INTERACTION OF A MARINE BIVALVE, Arca zebra, WITH ITS EPIBIONTS By Melissa M. Olguin A Thesis submitted to the Department of Biological Sciences in partial fulfillment of the requirements for graduation with Honors in the Major Degree Awarded: Spring, 2016 2 Dr. Sandra Brooke 3 Abstract The Arca zebra is a marine bivalve that is able to accrue a copious amount of epibionts (Vance 1978). Since Scandland (1979) the epibiont community on these shells for the Big Bend Region has not been looked out. I set out to perform an epibiont community analysis on the Arca zebra off the coast of Dog Island. I found 106 different species of organisms from 14 different Phyla. The most frequent organisms were barnacles (Amphibalanus sp.), a colonial red tunicate (unidentified, Class Ascidiacea), a stringy red alga (Gracilaria sp), a hydroid (Eudendrium carneum), and two encrusting algae (Peyssonnelia sp. and unidentified, Family Corallinaceae). Through a percent cover analysis I found that out of the most dominant encrusting groups, the encrusting coralline algae and the encrusting tunicates covered the most surface area. These results and their differences from Scandland (1979) have many implications and avenues for future study. Introduction This paper is focused on a population of a marine bivalve, the Arca zebra (Order Arcoida, Family Arcidae; Swainson 1833), commonly referred to as the Turkey Wing Clam. These bivalves tend to live in clumps of varying densities from depths of 0m- 140 m (460 ft) in hard-bottom habitats. They can be found as far north on the North American Atlantic coast as New Jersey (Field Museum 2015), and Bermuda (Sarkis 1992, Tunnell et al 2014), down through the Gulf of Mexico (Felder and Camp 2009), throughout the Caribbean (Miloslavich et al 2010), and off the coasts of Mexico, Panama, Columbia, Venezuela, and Brazil (Tunnell et al 4 2014) (Figure 1). They are economically important for Cuba and Venezuala, both which have established fisheries for them (Sarkis 1992). The population specific to this study is found in the Apalachee Bay in the northeastern Gulf of Mexico North Florida at a depth of about 12m. Figure 1. Geographic distribution of Arca zebra. Source: http://www.gbif.org/species/2286214 Arca zebra is a sessile organism anchored through the use of its byssus which is connected to the foot (Sarkis 1992). This can be retracted or intentionally torn off and regenerated, enabling the bivalve to move to other locations. These bivalves usually group together, both attaching to the sea floor and to other A. zebra. These mats provide a hard substrate used for settlement of other sessile organisms (Figure 2). The survival of many marine benthic plants and animals depends on the dispersal and settling ability of propagules (Abelson 5 and Denny 2012). There are a number of living organisms that provide the necessary substrate for the settlement of sessile animals (Wohl and Mark 1999). These animals may be referred to as ‘basibionts’. Many times marine megafauna such as sea turtles (Scaravelli 2003) and cetaceans (Whitehead 2014) can be seen covered with other organisms such as barnacles and mussels. Figure 2. Corals and other epibionts covering Arca zebra. Photo by Sandra Brooke. Epibionts growing on bivalves creates the opportunity to study the communities of microhabitats over small spatial scales (Scandland 1979). In Venezuala, the Atlantic Pearl Oyster, Pinctada imbricata, and the Turkey Wing Clam, A. zebra, provide necessary habitat for epibiont communities, in addition to Thalassia seagrass beds, corals, and rocks (Avila et al. 2013). Denser beds of bivalves allow for more complex macrofaunal communities, while 6 different species of bivalves can harbor different communities of epibionts; for example, some decapod communities vary among bivalve species (Avila et al. 2012). The most recent work on the community composition of A. zebra epibionts in the Big Bend Region region was done by Thomas Scandland in 1979 off the coast of Dog Island, North Florida. He sampled 140 shells which included both A. zebra and A. imbricata, and found 153 different taxa. Scandland’s study on the community composition of epibionts also suggested that the substrate surrounding the Arca beds was unsuitable for most fauna due to coarse shifting sands. This makes the Arca zebra one of the few options for epibiont settlement and survival in this area. One More Time Wreck Figure 3. Location of Arca zebra sampling site for this study; the One More Time wreck near Dog Island in the Apalachee Bay, North Florida Different kinds of interactions arise between epibionts and the organisms that provide hard substrate. In some cases, the basibionts are negatively affected. Increased density of epibionts on periwinkle snails can actually reduce both the speed and reproductive output of the 7 gastropod, thereby only benefiting the epibionts (Buscham and Reise 1999). The interaction between bivalves and epibionts can be mutualistic, such as with the jewel box clam, Chama pellucida (Vance 1978), where both groups benefit from reduced mortality via predation. The epibionts make predation on the bivalves cumbersome for starfish while the bivalves provide substrate habitat outside of the range of foraging sea urchins which would prey on the epibionts. Some studies suggest that the shells of some bivalves have evolved so that they can procure more epibionts, as seen with the spines of the Thorny Oyster, Spondylus americanus (Feifarek 1987) and the Noah’s Ark Shell, Arca noae (Marin and Belluga 2005). Additional studies have shown that the chemical composition of some epibionts provides an even greater deterrent from predation than their physical presence (Laudien and Wahl 2004). The objective of this study was to determine the epibiont community on an Arca zebra population at the One More Time Wreck located near Dog Island in the Apalachicola Bay (Figure 3). My study placed some focus on the differences between the communities of epibionts from the natural site near Dog Island studied by Scandland and the artificial site created by the One More Time Wreck. This led me to question the competitive processes occurring on individual shells and also to examine the use of the Arca zebra by several species of corals in the Gulf of Mexico. Understanding more about the interactions between epibionts and Arca zebra could lead to better management decisions, particularly regarding organisms such as corals. If A. zebra is a significant habitat for corals, then one step would be preventing a fishery from forming for these bivalves, as has been the cases on other countries. 8 Methods Sixty seven Arca zebra shells were collected from the “One More Time” Wreck in the Apalachee Bay (29o42’21”N; 84o37’25”W). The site was at a depth of approximately 12 meters. After collection, the shells were housed at the Gulf Specimen Marine Lab and Aquarium. Upon examination, three of the shells were determined to be Chama sp. which left the sample size at 64. Shells were placed in a grid formation and covered with a tarp covering the tank to prevent algal growth. For initial processing, each shell was removed from the tank using a small Tupperware container. Photographs were taken of each side and the top of the shell along with a floating label documenting the shell number and collection date. The shells are flattened on the dorsal side, adjacent to the hinge so they present a different aspect from the sides of the shells. Next, a description of all visible epibionts was written down. Finally, a razor was used to cut off samples of any soft tissue organisms such as sponges, tunicates, and algae. These samples were preserved in labeled vials of ethanol and recorded on a separate sheet. Calcareous and hard surfaced epibionts were identified and counted. The vials were taken to a lab and the samples were examined under a dissecting microscope at 2x and 4x magnification. Additional epibionts such as mobile macrofauna and a couple of meiofauna were discovered and recorded. For the identification of the polychaetes, the taxonomic information on the Natural History Museum’s website was used. Corals were identified with the help of the Brooke Lab at FSU. Sponges were identified using their spicules with the aid of the Wulff Lab at FSU. 9 Bryozoans were identified with the help of Dr. Burgess at FSU. The rest of the groups were identified using other online papers and databases as well as Felder and Camp (2009). Species accumulation curves were created for comparing species richness of epibionts observed via the naked eye with the diversity of epibionts when aided by technology. Using each shell as a sample and a Bray-Curtis similarity matrix, both a cluster analysis and SIMPROF were run to see if any groupings of shells were created by the communities living on them. Using this, a Non-metric Multi Dimensional Scaling (NMDS) plot was created to display those groupings. Then, using five size classes (6-6.99 cm, 7-7.99 cm… etc) as factors, an Analysis of Similarity (ANOSIM) was run on a Bray Curtis matrix to determine whether there were differences between epibiont communities based on the size of the shell they were on. The images taken of each side of the shells were used to conduct a percent cover analysis of the dominant epibiont groups. Photos taken of the Top, Left, and Right side of each shell were opened in the program, ImageJ and calibrated using a ruler that had been placed underneath the Arca zebra shell in the photo.