Halocynthia papillosa association with other sessile marine invertebrates in Calvi, Corsica Brittany Boyd University of California Santa Cruz, STARESO Underwater and Oceanography Research Station ABSTRACT Halocynthia papillosa (also known as a Sea Peach or Sea Squirt) is the sessile species studied in this observation. This observational study was conducted at the STARESO research center in Calvi, Corsica. Twenty-eight tunicates were found within a depth range of 6m to 14m along the north side of STARESO. A noted relationship among sponges and the tunicate was taken into account, since a high percent of the Halocynthia papillosa found had the Crambre cambre (orange sponge) nearby. H. papillosa and C. cambre relationship was observed to see if there was an association between them. Not only was H. papillosa and C. cambre association observed but H. papillosa spatial orientation was also observed to further understand this Mediterranean endemic specie. Keywords: STARESO, Tunicates, Mediterranean, Calvi, Halocynthia papillosa, Halocynthia papillosa association with Crambre cambre, Orientation INTRODUCTION The distribution and abundance of marine sessile invertebrate are affected by many factors in the marine environment such as larvae settlement, predation, and habitat availability (Grosberg 1981). The abundance of larvae is controlled by the amount of adults. Larvae settlement can be difficult because there are many factors to be considered. Location is key to sessile invertebrates survival overall. The location and the marine environment are factors that need to be considered during settlement (Hurlbut 1991). Predation would be considered during settlement by larvae. They would either seek a refuge location like a crack or a location with the least fish predators. Predation by fish is a large factor to larvae mortality. Predation affects their distribution, abundance and size distribution (Keough and Downes 1982). Predation and habitat availability is another factor contributing to marine sessile invertebrates abundance and distribution. At times it is impossible for settlement to occur (Holloway and Keough 2002). Competition for space is 1 P a g e
due to the overgrowth of many species (Grosberg 1981). Many species of sponges and tunicates seem to be the stronger colonizers (Keough 1984). Good colonizers like sponges can grow rapidly taking over large amount of space on rocky substrate. The ascidian Halocynthia papillosa is a solitary sessile filter feeder. H. papillosa is commonly found on large rocky substrate surrounded by many other sessile invertebrates (Ribes 1998). Unlike most tunicates, H. papillosa high reproductive activity occurs in late summer early fall, which provides evidence that seasonal factors do not play a role in their reproductive activity. Larval settlement for this MATERIALS AND METHODS Species Description Halocynthia papillosa is important to the ecosystem. They are sessile filter feeders that are important to the biomass production in the marine environment (Ribes 1998). H. papillosa is an endemic species to the Mediterranean Sea (Luna-Pérez, 2010). I observed them primarily on large hard rocky permanent substrate along the edges of the posidonia in the sublittoral zone. H. papillosa is hermaphroditic solitary species (Ribes, 1998). They reproduce once a year towards the end of summer and early fall. This is the time when other sessile species are usually dormant (Luna-Pérez, 2010). species is difficult since it is a solitary species (Péreza 2010). Since tunicates dispersal ability is low, and competition for space is high they may settle in unfavorable areas (Keough 1984). In this work, I hypothesized that there is a direct relationship between H. papillosa and Crambre cambre (orange sponge).tunicates and sponges play a very important role in habitat structure (Fiore 2010). Three questions are addressed in this paper are: (1) Is there a pattern of association between H. papillosa and nearby species? (2) Is there a pattern of association between H. papillosa and C. crambe? (3) What is the spatial orientation of H. papillosa on rocky substrate? Study Area This study took place in the Mediterranean Sea in Calvi, France at the STARESO Research center. The north side of the STARESO harbor was surveyed along the north wall up towards the Marine reserve. This observational study was conducted throughout a four week period in the month of October 2010, (10/06/2010-10/24/2010). All observations were done with SCUBA. H. papillosa was observed in the sublittoral region in the depth ranges of 6m to 14m. The temperature at this depth was typically 18 C. The substrate that they were all found on was a rocky wall. There was an abundance of turf algae on these uneven rocky walls. All twenty-eight H. 2 P a g e
papillosa found were found above the Posidonia line. Is there a pattern of association between H. papillosa and nearby species? To determine the association between H. papillosa and nearby species twenty-eight individual H. papillosa were identified and surveyed. A.5m x.5m square quadrat with twenty-five evenly distributed points was used. Almost all H. papillosa were placed in the center of the quadrat at point thirteen unless the environment did not permit it such as a cliff or crack, then they were merely positioned at a different point on the quadrat. Once centered, at each point the species that was directly under each point was recorded and only sessile invertebrates were surveyed. In order to for the survey to be unbiased a second survey was done similar to the first except the tunicate was not included in the survey. This was twenty-eight random quadrat measurements taken in the general area of the tunicates. Only permanent substances or species where counted in this survey as well. These studies were all done with SCUBA. The data collected from these two surveys should determine if H. papillosa has a general substrate preference along with any species association by comparing the most abundant species or substrate present within the data collected for both surveys. Is there a pattern of association between Halocynthia papillosa and Crambre crambe? In order to determine the association between H. papillosa and C. cambre the following surveys were done. First, I measured the distance from an individual H. papillosa to the nearest patch of C. cambre. A distance greater than 150mm was considered irrelevant. I then determined the likely distance between a random point and the nearest C. cambre, it occurred within 150mm of the target point. Here the fifty random points were selected along the same rock surfaces and at the same depth profile used for the targeted H. papillosa. This was used to create a distribution of distances, based on random points rather based on distances from H. papillosa, and hence represents a null distribution of distances. I tested for a potential pattern of association by comparing the percentage of observations in the targeted survey that were within 150mm to that expected by chance (from the second survey). What is the spatial orientation of H. papillosa on rocky substrate? In order to determine H. papillosa spatial orientation for all twenty-eight tunicates found their height was measured with the use of calipers. The tunicates height was measured from the test (tunic) to the oral siphon (top siphon), once it had shrunk down and 3 P a g e
released most of the water out of its body. The height was simply measured if height played a role in orientation. Second, the depth of each tunicate was recorded using a dive computer. Last measurement taken was the heading (dive compass) of all twenty-eight tunicates with respect to the substrate they were attached to. An average depth and height could be determined along with the average orientation of the tunicate. It will conclude if H. papillosa has a preference with the direction it is positioned in the sea, RESULTS Twenty-eight Halocynthia papillosa were observed at the depth range of 6m to 14m. A number of algae and sessile species were located in the same vicinity, such as sponges, tunicates, and different types of algae mainly turf algae. All H. papillosa were found along permanent rocky substrates mostly shaded by the rocks above. Is there a pattern of association between H. papillosa and nearby species hypothesis can be concluded with Tables 1&2. Table 1 is the ANOSIM test; this statistical analysis measures the variance with in groups. There is a difference among the communities (p=0.09 Table 1). This confirms a SIMPER test must be done to compare which species has the greatest effect. With this being said a further look at the communities must be examined to determine the variance in species. Table 2 is the SIMPER test, which shows what makes the two groups different. In Table 2 the two groups compared are areas with H. papillosa and the second group are areas without the presence of H. papillosa. The contributor column highlighted (Table 2) shows the percentage of each species present around H. papillosa. C. cambre (OS) drives the community s composition (34.32% Table 2). A pattern of association between Halocynthia papillosa and Crambre cambre results can be found within Table 3. Pearson Chi-square test was done to further investigate if there was a pattern of association between H. papillosa and C. cambre. The Pearson Chi-square tested two different types of sites and compared the distribution frequency of C. cambre. The points selected first were the twenty-eight H. papillosa found and used as a reference point and a measurement was taken to the nearest C. cambre if it was within the 150mm marker found. For the results to be unbiased fifty random points were then selected and measured the same. Out of the fifty random points only one point had C. cambre present within the 150mm range. The H. papillosa community is different than non inhabited H. papillosa communities. (Pearson Chi-Square p=0.001 Table 3) The spatial orientation of H. papillosa on rocky substrate is visually 4 P a g e
shown in figure 1. The results prove there is an obvious association between the H. papillosa and C. cambre. There is a noticeable difference in the two distributions (fig. 1). The random points seem to favor the South-West side while H. papillosa favor the North-East. These findings prove that H. papillosa have a preferential direction on rocky substrate. Table 1 ANOSIM Global Test Sample statistic (Global R) 0.072 Significance Level of sample statistic 0.9% Number of permutations (random sample) 999 Number of permuted statistics to Global R 8 (ANOSIM test is to test the difference in communities.) Table 2 SIMPER Group W/ Group W/O Species Av.Abund Av.Abund Av.Diss Diss/SD Contrib% Cum.% OS 1.06 0.81 8.58 1.27 34.32 34.32 A 4.33 4.72 5.19 0.54 20.74 55.06 CT 0.4 0.28 4.17 0.82 16.68 71.74 PS 0.26 0.1 2.31 0.45 9.26 81 B 0.27 0 1.97 0.46 7.89 88.89 R 0.24 0.04 1.77 0.48 7.06 95.95 (SIMPER test is to determine which specie the community is most driven by.) Legend OS= Orange Sponges A= Algae CT= Colonial Tunicates PS=Purple Sponges B=Bryozoans R=Rock Table 3 150mm from OS NO YES TOTAL H. papillosa 7 21 28 Random 49 1 50 Total 56 22 78 Test Statistic Value df p-value Pearson Chi-Square 47.234 1 0.001 (Chi-square: to compare the difference in the communities looking at the C. cambre.) 5 P a g e
90 180 Count 0 5 10 0 HEADING Treatment 270 Halocynthia Random Points Figure 1 (Orientation comparison between H. papillosa and random points) 90 in this figure is West in comparison to a compass. DISCUSSION The goal of this study was to assess a pattern of association with Halocynthia papillosa and other marine sessile invertebrates. Spatial orientation was required for this study to compare whether there was an association among the species and/or a settlement cue by larvae. Larvae usually do not settle to far from their parents, so their location is fairly consistent (Hurlbut, 1991). The results show a very strong association among H. papillosa and C. cambre compared to any of the other species. These are the results I expected. I made an observation of this association between H. papillosa and C. cambre and it was confirmed with the data results. These two species seem to be oriented near each other most of the time and spatial orientation is the main factor. The results in (Table 1) indicate that the two communities (with H. papillosa present or not) are very different. I am glad to have discovered that it is the C. cambre driving the communities distribution (Table 2). The algae may be the most abundant but in terms of an association with H. papillosa and C. cambre, C. cambre is the largest contributor. This further supports my hypothesis that there is an association between H. papillosa and C. cambre. 6 P a g e
Out of twenty-eight H. papillosa, twenty-one had C. cambre present within the measurable range. These results give the expected distribution; the p-value 0.001 is very low which means that the communities are very different and that there is a very strong positive association between the H. papillosa and C. cambre (Table 3). This table gives a better perspective of the distribution in the studied area. Only twenty-eight H. papillosa were found and twenty-one of them had a sponge present near them. The fifty random samples done I only landed on an orange sponge once. This random sample was necessary so the data was unbiased, if not then the distribution analysis of those two species would not be accurate and a true association between them would be undetermined. All twenty-eight H. papillosa were oriented in the North-East direction (fig. 1). There could be many possible reasons for their spatial distribution such as currents, or lighting. None of the H. papillosa studied was found in direct sunlight, they were all shaded by the rock walls above them. H. papillosa prefer reduced lighted areas. They can also withstand strong water currents because of their rhizoids, which brings in a diversity of nutrients for them (Antoniadou, 2006). It seems like the main settling cue would be due to the amount of sunlight. The ascidian Halocynthia papillosa is a solitary sessile filter feeder and the results in this study raise several questions about the association with Crambre cambre. The results were limited to the North of STARESO near a marine reserve; this association may not be seen elsewhere in the Mediterranean. Further study needs to be conducted throughout the Mediterranean to test if this is in fact a true association H. papillosa and C. cambre have or if it is only true in Calvi and if so why. This noted association could have just been a coincidence, after all H. papillosa and C. cambre are both filter feeders and may be near each other for nutritional purposes only. LITERATURE CITED Antoniadou, C., E. Voultsiadou, C. Chintiroglou. 2006. Sublittoral megabenthos along cliffs of different profile (Aegean Sea, Eastern Mediterranean). Belg. J. Zool, 136(1) :69-79 Fiore, C.L., P.C. Jutte. 2010. Characterization of macrofaunal assemblages associated with sponges and tunicates collected off the southeastern United States. Invertebrate Biology 129(2):105-120 Grosberg, R.K. 1981. Competitive ability influences habitat choice in marine invertebrates. Macmillan Journals Vol. 290:700-701. Holloway, M.G, M.J. Keough. 2002. An introduced polychaete affects recruitment and larval abundance of sessile invertebrates. Ecological Society of America Vol. 12, No. 6: 7 P a g e
1803-1823 Hurlbut, C.J. 1991. The effects of larval abundance, settlement, and juvenile mortality on the depth distribution of a colonial ascidian. J. Exp Mar. Biol. Ecol. 150:183-202. Keough, M.J. 1984. Effects of patch size on the abundance of sessile marine invertebrates. Ecological Society of America Vol.65,No.2: 423-437 Keough,M.J, B.J. Downes. 1982. Recruitment of marine invertebrates: The role of active larval choices and early mortality. Oecologia Vol 54:348-352 Ribes, M., R. Coma, J.M Gili. 1998. Seasonal variation of in situ feeding rates by the temperate ascidian Halocynthia papillosa. Marine Ecology Progress Series Vol 175:201-213. Ruitton, S., P. Francour, C.F. Boudouresque.2000. Relationships between algae, benthic herbivorous invertebrates and fishes in rocky sublittoral communites of a temperate sea(mediterranean). Estuarine, Costal and Shelf Science Vol. 50:217-230 Pérez,B.L., C. Valle, T.V. Fernandez, J.L. Sanchez-Lizaso, A.A. Ramos-Espla. 2010. Halocynthia papillosa (Linnaeus,1767) as an indicator of SCUBA diving impact. Ecological Indicators Vol 10:1017-1024. 8 P a g e