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· nO()~_ I ql J . -il t{V3 Mook, D .H. 1.975. Abstract Fouling Community Studies in the Indian River Introduction The development of fouling communities is not well understood, but it is known that the spawning periods of the fouling organisms and local environmental factors will influence the development and structure of the fouling community. Factors such as temperature (Barnes and Powell, 1953), salinity (Barnes and Barnes, 1974), depth (DePalma, 1962), light (McDougall, 1943; Berrill, 1950), substrate material (Pomeratand Weiss, 1946) and position (McDougall, 1953) have been discussed in the literature. Paine (1966) and Connell (1961) discussed the effects of predation and competition in determining the structure of fouling communities. Goodbody (1961) has stated that inhibition of settlement of fouling organisms is also important in determining species composition of fouling communities. Goodbody (1961) states that there is a definite successional process in the fouling community leading to a climax community. Smith et al. (1950) found no evidence of succession in fouling communities in Biscayne Bay and suggested that all changes were a result of some external perturbation. Sutherland and Karlson (1973) discuss the difficulties in discerning the differences between community succession and seasonal progression. In a recent study by Sutherland (1974), the fouling community was found to have several stable states, each with a species missing. He further extrapolates that there may be as many of these stable states or boundlly points as there are species in the community however many of these points may be "trivial". Other studies have indicated that there may be several stable points with all species present. However, they cannot all be considered climax or globally stable communities because they are not resistant to all perturbations. The purpose of this study is to determine if a globally stable or climax situation exists with the local fouling community at the site of our laboratory and to suggest what pathways the community takes to develop into this condition. This paper w~ll report the seasonal settlement of fouling organisms. Methods and Materials Unglazed clay tiles (15 x 15 cm) were suspended about 10 cm below the surface from a barge in the Link Port canal. Plates were put in the water for a 2 wk. , 1 mo., 3 mo., 6 mo . , and 1 yr. time intervals and examined at the end of these periods. All sessile organisms were identified, counted and their percent coverage estimated. Results All of the results are contained in Figure 1. Fig 1. settlement of fouling organisms in Link Port MONTH A M J J AS 0 N D J F M BALANUS SPIRORBlS HYDROJDES BRANCHIOMMA " BUGULA NERITINA BUGULA STOLONIFERA w z u C3 z HI PPOPOR INA ::::> ro -c ~ U w CONOPEUM SCHIZOPORELLA STYELA PLiCATA DIPLOSOMA BOTRYLLI NA E OYSTERS a. Vl Discussion Barnacles were common settlers throughout the year except in the summer and midwinter where they were conspiciously absent. The chief specie was Balanus eburneus but Balanus amphitrite was also present. The decrease in settlement in June may have been due to lower salinities which are known to effect barnacle larvae (Barnes and Barnes, 1974) or competition from Branchioma or Schitzoporella. The dip in the winter may have been due to lower temperatures or competition from Spirorbis. Moore and Albertson, (1974) found a similar pattern of barnacle settlement in Miami and suggested that temperature may play an important part in the settlement of barnacles and that there may be some competition between barnacles and tube worms. Spirorbis settled heavily throughout the winter and its settlement is just beginning to decrease at the present time. Hydroides also settled in the winter months but not in as great numbers as Spirorbis. The sabellid worm, Branchioma bairdi along with the encrusting bryozoan Schiczoporella unicornis settled in the late spring and early summer and quickly dominated the plates and covered up other organisms. Only some of the colonial tunicates and some barnacles were able to compete with them. While these organisms were present little else was able to settle. This may be the reason for the reduced number of species found at that time. Bugula stolonifora and Bugula neritina were common settlers in the winter months but absent from plates the rest of the year. These animals are considered to be winter organisms in Florida (Moore and Albertson, 1974) so this pattern would be expected. Hippoporina verelli, a warm water encrusting bryozoan was absent from most mid-winter plates but present the rest of the year except in the late spring, when it may have been outcompeted by Schitzoporella. Conopeum is present from early fall to late spring. Since Conopeum is generally considered to be a poor competitor (Dudley, 1973), its absence in the late spring and summer could be a result of competition rather than absence of larvae. Late spring and summer plates were generally completely covered with organisms while fall and winter plates were more sparsely settled. The colonial ascidian Diplbsoma macdonaldi was common most of the year however the colonies reached greater size in the spring, often covering large areas of the plates. Some of the Botryllinae tunicates, Botryllus planus, Botrylloides nigrum and Symplegma viride were able to colonize areas on top of the Diplosoma and build rather large colonies in the spring. The solitary tunicate Styela plicata a~d oysters were not common on short term plates even though they seemed COMnon on sea walls and older plates. This indicates that these species may have a preference towards older plates. Long term plates will have to be examined to understand the settlement of these organisms. Summary The differences between short term plates indicate that there is a great difference between pioneer species throughout the year. Because of these differences, the pathways that the fouling community must take towards a potential climax condition must vary widely, depending on what time of year the substrate is immersed in the water. Data collected from 3 and 6 month plates indicates that Styela plicata and oysters may be important in at least one stable state of the fouling community. These organisms have been common fo£ several years on pilings and sea walls in the area but it is not known whether this represents a climax situation. More experiments will have to be done with long term plates to find out what constitutes a climax state of the fouling community. Literature Cited Barnes, H. and M. Barnes. 1974. The responses during development of the embryos of some common cirripeds to wide changes in salinity, J. EXp. Mar. BioI. Ecol. 15:197-202. Barnes, H. and H. Powell. 1953. The growth of Balanus balanoides and B. crenatus under varying conditions of submersion. -J. Mar. BioI. Ass. U. K. 32:107-128. Berrill, N. 1950. The tunicata with an account of the British species. The Ray Society. London. 354 p. Connell, J. 1961. Effects of competition by Thias lapillus and other factors on natural populations of the barnacle Balanus balanoides. Ecol. Monog. 31:61-104. DePalma, J. 1962. Marine fouling and boring organisms in the Tongue of the Ocean, Bahama Exposure 11. Unpublished manuscript. Dudley, J. 1973. Observations in the reproduction, early larval development and colony of Astoseny and Canopeui~ t.enu i.ssirnum. Science 14:270-278. --_._-Goodbody, I. 1961. Inhibition of the development of a marine ~essile community. Nature 190:282-283. McDougall, K. 1943. Beaufort, N. C. Sessile marine invertebrates of Ecological Monog. 13:323-374. Moore, H., H. Albertson and Sigmund Miller. 1974. Long term changes in the settlement of barnacles in the Miami area. Bull. Mar. Sci. 24(1):86-100. Paine, R. 1966. Food web complexity and species diversity. Am. Nat. 100:65-75. Pomerat, C. and C. Weiss. 1946. The influence of texture and composition of surface on the attachment of sedentary marine organisms. Smith, F., R. Williams and C. Davis. 1950. An ecological survey of the subtropical inshore waters adjacent to Miami. Ecol. 31:ll9-r46. Sutherland, J. and R. Karlson. 1973. Succession and seasonal progression in the fouling community at Beaufort, N.C. Unpublished manuscript. Sutherland, J. 1974. Mult~ple stable points in natural communities. Am. Nat. 108:859-873. Presented to the 39th Annual Meeting of the Florida Academy of Sciences