 |
 |
|
 |
||
 |
||
|
Research topics in:
|
||
|
Marine biology |
|
Axtell, David D., "Development of Dry Season Hatcheries For Olive Ridley Sea Turtles (Lepidochelys olivacea) in Ostional Wildlife Refuge". Adv. Claudette Mo. Grinnell College. 1997. 13 pp. Two hatcheries for olive ridley sea turtle eggs, Lepidochelys olivacea, were constructed for use from March to May 1997 in Ostional Wildlife Refuge, Santa Cruz, Guanacaste, Costa Rica. Temperature, hatchling success rate, and embryological data were collected and analyzed over a 72-day period. There was no significant difference in hatching percentages between the control or test nests in both hatcheries. Problems with low fertility, probably due to rotation of eggs after ovipositioning, and crab predation decreased the hatching success rate in Site A to 15.13% (121 turtles/800 eggs), and produced no hatchlings in Site B. This was the first time dry season hatcheries have ever been successful in Ostional. For this reason, detailed schematics of the hatcheries were created with Spanish text instructions for use in Ostional and other beaches with similar harsh conditions. Baek, Sung, “Available Area for Nesting by the Olive Ridley (Lepidochelys olivacea) sea turtle in the "Principal Nesting Beach" of Ostional, Guanacaste, Costa Rica”. Advs. MSc. Marta L. Arauz Almengor and MSc. Rodrigo A. Morera Avila. St.Olaf. 2000. 22pp. I studied the population of Olive Ridley, Lepidochelys olivacea, that nest solitarily and during the arribada in the months of March and April of 2000 in the “Principal Nesting Beach” of Ostional, Costa Rica. The objectives of my project was to research the behavior of nesting site selection in different beach zones by the solitary and the arribada turtles and to research the actual utilization of the available nesting area by the solitary Olive Ridley turtle. With daily beach patrols I was able to collect data of the number and exact locations of the nests in different zones and sectors of the beach. This data was later digitized into a computer along with the measured weekly high tide for analysis and calculations. The weekly area available for nesting averaged 24,136 ± 2,683 m2 and an average of 32.3% (7,785 ± 6,631 m2) of that area was used for nesting and 67.7% (16,350 ± 6,197 m2) was not used. The solitary nests concentrated in the medium and low beach zones (50.4%, 39.5% respectively), which borders the high tide line, with only 10.1% in the high zone. During the arribada 53.7% of nests were laid in the low zone, 43.9% in the medium zone, and 2.4% in the high zone. Majority on the solitary nests were laid the week before the arribada (43.4%) and after (32.6%). It was concluded that the nesting concentrates near the tide line but the majority of the beach is actually utilized for nesting. I recommend that parts of the beach, especially the medium and low zones, be more strictly conserved and possibly be closed off from visitors during the dry season. Black, Andrew, "Site Fidelity and Refuge Utilization of G. pulchra in White Mangroves in the Gulf of Nicoya, Costa Rica." Adv. Lizeth Díaz and Bill Szelistowski. Colorado. 1998. 23pp. This study examines Goniopsis pulchra, the Eastern Pacific mangrove crab, site fidelity and utilization of mangrove habitat in the Cocorocas estuary of the Gulf of Nicoya, Costa Rica. Crabs seemed to center their activity around white mangrove trees (Languncularia racemosa) with hollowed out trunks and branches (lairs). Marked crabs remained on these trees for up to 30 days and showed no evidence of movement to other trees. Most of the crabs displaced to mangrove trees between 3-5 m away from original capture tree, returned by the following day, and most non-returning crabs were later seen on larger lair trees. Predation was high on crabs tethered underwater at high tide, but no predation occurred on crabs secured above water to mangrove trees at high tide or to the sediment at low tide. Aggressive interactions suggest that limited resources provided by lair trees, combined with predation threats, keep crabs faithful to white mangrove lair trees. Christenson, Megan, "The Effect of Vegetation on Incubation Temperature of Olive Ridley (Lepidochelys olivacea) Sea Turtle Nests in Ostional National Wildlife Refuge." Advisor: Gerardo Chaves Cordero. St. Olaf College. 2005. 22pp. The purpose of this investigation was to determine the effect of different vegetation types on the incubation temperature of olive ridley (Lepidochelys olivacea) sea turtles in Ostional National Wildlife Refuge in Guanacaste, Costa Rica during March and April of 2005. Four sites along Playa Nosara were studied because each contained a different type of vegetation. At each site temperatures were measured three times daily at four different depths. It was found that in the site lacking vegetation the below surface sand temperatures were hot enough to kill all laid eggs. The sites with hibiscus and mangroves were similar enough to be considered the same statistically. The types of vegetation were quantified for Playa Ostional and Playa Nosara. It was found that lack of vegetation was the most common category and mangrove coverage was the least common. Perhaps the community of Ostional should try to maintain more of the forest and mangrove in order to provide better nesting conditions for olive ridley eggs during the dry season. de Witt, Derek, "The Effects of Temperature, Slope, and Debris on Nesting Behavior of Leatherback Sea Turtles, Dermochelys coriacea, at Playa Gandoca, Costa Rica." Adv. Didiher Chacón, ANAI. Macalester College. 2006. The nesting behavior of leatherback sea turtles, Dermochelys coriacea, was studied during March and April at Playa Gandoca (9.583N, 82.583W), Costa Rica. The main purpose of the research was to determine how a set of factors affected the likelihood that a female would nest once she came up onto the beach. Data was collected on the surface temperature of the sand, the slope of the beach, and the obstructive debris in the area of the turtle in order to determine whether there was a significant difference in those factors between positive and negative nesting events. While previous studies had been done about nest site preferences in turtles, few had been done on D. coriacea and none regarding this specific question. The data collected show a significant positive correlation between nesting result and sand surface temperature and a significant negative correlation between nesting result and slope. No significant correlation was found between nesting result and debris. The temperature correlation may be a behavior based on embryo temperature tolerance levels or temperature dependent hatchling sex ratio. The slope correlation is not entirely conclusive based on observations as turtles will sometimes climb steep slopes to nest and other times will not. Whatever the reason, it is likely that the behavior in question is multi-factorial. The debris factor requires further study to understand its potential effects. Donohue, Micca, "Growth rates of Thalassia testudinum in different environments and organisms associated with this seagrass." Adv. Jorge Cortés. Macalester College. 1995. 24pp. During March and April, 1995 seagrass communities at Cahuita National Park, Costa Rica were studied. Growth rates of Thalassia testudinum (turtle grass) were determined at three sites along Cahuita Point. Seagrass densities of turtle grass and Syringodium filiforme (manatee grass) were collected to investigate the successional stage of each site. Leaf area indices of turtle grass were calculated at each site to study the plant stress at each site. Physical parameters, including temperature, depth, transparency, and current levels were collected daily to investigate the control of environmental conditions on growth rate of turtle grass. Biofouling organisms were counted and identified to compare biodiversity of the three sites and complete a species list of the area. Results of the study did not show significant variations in growth rate among the three sites, although environmental conditions varied significantly. This shows the wide ranges of environmental conditions that are acceptable for turtle grass. Based on densities of turtle and manatee grass, the three sites were at different successional stages ranging from mixed meadows to pure turtle grass meadows. Turtle grass at the three sites was stressed at varying levels. Diversity was quite variable throughout the three sites. Eggers, Eric, "A Survey of Fish Populations and Relations to Habitat Parameters in Curú Bay, Costa Rica." Adv. Christopher Vaughan. Kenyon. 1993. 24 pp. During March and April 1993, research was carried out relating marine fish diversity and selected fish numbers to physical and biological habitat parameters at nine 1000 m² sites. A total of 3251 individuals from 35 fish species, as well as 4 Echinodermata spp., 2 Mollusk spp., 1 Crustacean sp., and 1 Nudibranch sp. were counted in the Bay of Curú Wildlife Refuge, Costa Rica. Species diversity determined by Simpson's test ranged from 0.341 to 0.822 for the nine sites. Two physical habitat parameters (rock and abundance of shelter) were positively correlated with more fish diversity, while sand was negatively correlated. Positive correlations were found between fish species diversity and eight of the biological habitat parameters: 4 algas, Blue-green algae sp., Amphiroa rigida, Padina santae-crucis, y Dictyota bartayresii; 1 Anthozoa, Pacifigorgia sp.; 1 Ascidiacea, Ascidiacea ge. sp.; 1 coral, Portites astereoides; and 1 Hydroid, Lytocarpus nuttingi. The most commonly found fish species were the spotted rose snapper (Lutjanus gutatus), the panamic sergeant major (Abudefduf troscheli), the cortez rainbow wrasse (Thalassoma lucansanum), and the cortez damsel (Pomacentrus rectifranum) respectively. The cortez damsel was found to have eleven positive correlations to the biological and physical habitat parameters. This research marks the beginning of a long-term monitoring project of the size and diversity of fish populations in Curú Bay. |
|
Engels, Mary, “The fossilized reefs of Cahuita, Limón, Costa Rica.” Adv. Jorge Cortés. Colorado. 1999. 12pp. A surface study of fossilized reefs was conducted in Cahuita, Limón, Costa Rica during the month of March and April, 1999. The research involved taking transects from sea level at regular intervals to ascertain differences in elevation which indicate reef topography. Reef profiles and a Post map were delineated with the seven substrate classifications and sample locations. The profile topography indicates a solitary reef system uplifted by a major tectonic event. The samples taken yielded twenty-one coral species from fifteen different families. Feindt, Jenny, “Evaluation of the effect of tourism on the reproductive behavior of Olive ridley (Lepidochelys olivacea) turtles in Playa Ostional, Costa Rica.” Adv. Marta Araúz-Almengor. St.Olaf. 1999. 25pp. During the months of March and April, 1999, I studied the behaviors of tourists on the beach of Ostional towards the Olive ridley (Lepidochelys olivacea) turtles. I noted the actions of tourists on the beach and observed how they effected the nesting turtles. I observed that the behaviors the tourists used most frequently were using a flashlight 34% and standing within 1-3 feet of the nesting turtle 34%. Tourists were also located more often in the middle zone of the beach 57% than in any other part. I also conducted interviews with the tourists and discovered that the majority of tourists knew nothing about turtles 60% and the behaviors humans should use when near turtles. Interviews were also conducted with the habitants of Ostional and I discovered that 100 % of those I interviewed think that tourism is a good thing for the town and they would like to see more. From these interviews I received many recommendations on how to increase tourism and how to inform the tourists about the lifestyle of the turtle and proper behaviors. Frankowski, Deanna, "Sea Turtles: A Conservation Assessment" Adv. Dr. Paul Hanson, Universidad de Costa Rica. Ripon College. 2006. Throughout the months of April and March during the spring of 2006 I studied solitary nesting sea turtles on Playa Junquillal in the Guanacaste province of Costa Rica. My original thesis focused on the effect of artificial light pollution on the nesting behavior of the various species of sea turtles nesting at Playa Junquillal. These species include the Loggerhead (Caretta caretta) the Hawksbill (Eretmochelys imbricata), the Olive Ridley (Lepidochelys olivacea), the Green Turtle (Chelonia mydas), the Pacific Green or Black Turtle (Chelonia mydas agassizii) and the Leatherback (Dermochelys coriacea). However, due to a slow nesting period and lack of significant data I altered my project from a study of the sea turtles to an assessment of the conservational efforts that are in place to protect these endangered species. As a result, using sea turtles as an example, I provide an in-depth analysis of various factors that members of the science community should consider when operating a long-term conservation program in a foreign country. Recommendations for future research included a comparison of nest protection methods (relocation versus no relocation), a comparison of predator deterrents, and analysis of the effectiveness of converting poachers to conservationists. Gamble, Allison, "Fish Community Composition in the Coral Reefs of Cahuita National Park and Gandoca-Manzanillo National Wildlife Refuge." Adv. Bill Szelistowski. Lawrence. 1998. 22 pp. Fish community composition in Cahuita National Park and in Manzanillo National Wildlife Refuge were surveyed during March to May, 1998. Censes of the two communities were obtained by snorkeling along 7 predetermined transects at each area and using a rapid visual census technique to identify and count fish. Data from the two sites were compared, and the 1998 Cahuita data were also compared with data from a similar study done in Cahuita 1982. Significantly higher numbers of individuals were seen at Manzanillo than at Cahuita, but no differences were seen in species richness, diversity, or in the evenness of diversity. There was also a large overlap in fish species and in their dominance in the community. Comparisons between Cahuita 1982 and 1998 showed that the diversity and abundance were not significantly different, but richness was higher and the evenness of the species diversity was lower in 1998. Values for both areas were lower than those that were obtained in different Caribbean coral reefs (Jennings et al.,1995; Phillips and Perez-Cruet, 1984). These data support the hypothesis that the high levels of sedimentation at Cahuita are affecting the fish community there, although other factors, such as increased tourism, are also probably having a negative impact on the reef as well. Similarity between Manzanillo and Cahuita indicates that the factors that are affecting Cahuita could also be affecting Manzanillo. Goldberg, Alyssa, "The Effect of Artificial Temperature and Humidity for Incubation of the Olive Ridley (Lepidochelys olivacea) Sea Turtle During the Dry Season in Ostional, Guanacaste, Costa Rica." Advisor: Gerardo Chaves. Colorado College. 2004. 24pp. I studied hatching success of the Olive Ridley (Lepidochelys olivacea) sea turtle under different conditions at Playa Ostional, Guanacaste, Costa Rica during March and April of 2004. My objectives were to determine what effect different temperatures, humidity, nest location, and predation have on hatching success. A hatchery was set up with shaded and non-shaded nests, as well as watered and non-watered nests. After taking temperatures three times a day for 44 days and observing the hatching, I learned that eggs in the dry nests died immediately, eggs in the nests with only water went farther into development, and the eggs with shade and water had more than 30 days of successful development or hatched. Also, the nests in the upper beach by the lagoon developed and hatched more successfully than the nests in the middle beach. Mites predated eggs in the early stages of development while larvae flies predated developed embryos. With this information, the biologists of Ostional will work towards building a hatchery for enhanced hatching success during the winter, or dry season. This project will lead to repopulating an endangered species. Gove, Matt, “Effects of tourism on the coral reef of Cahuita National Park, Costa Rica.” Adv. Jorge Cortés. Colorado College. 2000. 10pp. The reef at Cahuita National Park was studied for effects of tourist damage. An area disturbed by people walking (Site 1) and one without disturbance (Site 2) were studied inside the shallow lagoon at Punta Cahuita. Four transects of 10 x 2 meters were set up to create 80 1 X 1 meter quadrats. Species, number of colonies, percent coverage and a check for damage was taken within each quadrat. Shannon-Weiner Diversity Index (H') were found to be significantly higher in Site 2. The average percent coverage and number of colonies per quadrat of breakable species were also significantly higher in Site 2. Damage information collected to measure the impact of this project on the corals demonstrates the effect walkers have on the lagoon. An average person per day was found to break 3.18 Porites porites and upturn 0.26 Amphiroa fragilissima. Snorkeler activity was also studied. Individuals were followed for two minutes each and watched for kicking, touching, breaking or standing on the coral. An average of 1.48 kicks per person with fins was found, significantly higher than the 0.31 kicks per person without fins. Both of these studies reveal a strong tourist pressure on a reef already dying from siltation pressure. Heberlein, Jake, “The Effect of Sun/Shade and Artificial Watering on Dry Season Hatching Success of Olive Ridley (Lepidochelys olivacea) Sea Turtles at Playa Ostional, Guanacaste, Costa Rica.” Advs. MSc. Marta L. Araúz Almengor and MSc. Rodrigo A. Morera Avila. Beloit. 2000. 25pp. I studied the effect of different moisture and sun intensity regimes on the hatching success of olive ridley (Lepidochelys olivacea) sea turtle nests at Playa Ostional, Costa Rica during March and April of 2000. By recording the average temperatures and percent success for nests placed in sun or shade with only natural moisture, and sun and shade with daily moistening, I determined that shading can significantly improve the hatching success for olive ridley nests during the summer when success rates are at a yearly low. I also created a socioeconomic profile of the registered egg harvesters at Ostional by interviewing 20 randomly selected individuals from a population of 210. The compilation of the answers to my questionnaire showed that many residents of Ostional are extremely dependent upon egg harvesting currently, and this dependence is increasing over time. The biological portion of my study provides a basis for future research that will be used to direct an upcoming rehabilitation project at Ostional. The socioeconomic profile will help the cooperative association responsible for egg commercialization invest its proceeds to ensure a stable economic future for Ostional. |
|
Johnson, Keri, "Distribution and Changes in Plant and Invertebrate Communities of the Coral Reef Lagoon at Cahuita National Park, Costa Rica." Adv. Jorge Cortés. Beloit. 1992. 11 pp. A study of the Caribbean coral reef system at Cahuita National Park, Costa Rica was performed during March and April, 1993. The reef was exposed to destruction resulting from the April, 1991 Limón earthquake and increased sedimentation. A current inventory of marine plant, algae, and invertebrate populations in the lagoon was performed to assess the earthquake's effects, and also the status of the reef communities. Comparisons within studied transects showed a greater population of algae and coral in the middle section, with numbers and diversity decreasing near the coastal areas. The distribution of seagrasses was more even throughout the lagoon. This data was compared with data collected in 1991, just before the earthquake and again in 1992. Data from the 1991 study shows similar populations of seagrasses, algae and coral as the 1993 study. The 1992 study showed higher populations of certain seagrasses and algae, showing that the lagoon may have been exposed to higher concentrations of nutrients just after the earthquake, but has now recovered. Kromer, Mark, "The Role of Reproductive Behavior in the Territoriality of the Dusky Damselfish (Stegastes dorsopunicans)". Adv. Helena Molina. Grinnell College. 1997. 18pp. Interspecific territoriality and behavioral patters related to reproduction was examined in the Dusky Damselfish, Stegastes dorsopunicans Poey (Pomacentridae), in Manzanillo, Limón, Costa Rica. Females fed more and had a significantly greater foray frequency than males, while males patrolled more and entered their refuge significantly more frequently. Males were found to have a significantly higher attack frequency against all intruders, and a significantly higher attack frequency against egg predators than females. A significant positive correlation was found between dietary overlap and aggression in both males and females. When recalculated with egg predators being excluded, the correlation coefficient for both males and females improved. Around the full moon, females were found to feed and foray significantly more frequently, but patrol significantly less frequently. Meanwhile, males were significantly more aggressive towards intruders while actively defending a clutch. The patterns of agonism exhibited by males and females indicate that nest defense plays an important role in the territorial strategy of male Dusky Damselfish, while defense of food resources is the major governing factor in the territoriality of females. Lewis, Emily S., "The Species Diversity of Tidepools in Western Costa Rica in Relation to Height, Duration of Exposure and Lunar Phase." Adv. Helena Molina Ureña. Cornell. 1996. 25pp. The species diversity and composition were calculated in seven tidepools at Curú National Wildlife Refuge on the southeast tip of the Nicoya Penninsula of Costa Rica and compared with the height and duration of exposure of each pool throughout an entire lunar cycle. Sixty-seven species were found during the study. Results of this study show that although duration, as a function of height, was a significant factor in species diversity of these tidepools (p=0.0000, R2=42.72%), height of pool explained more of the difference (p=0.0000, R2 = 54.22%) in species diversity of vertebrates and invertebrates. The lunar phase and day of the lunar month were not shown to significantly affect the species diversity of these species, although a change over time was visible, where the species diversity increased approximately four to five days after the change of lunar phase. The species diversity of sessile colonial invertebrates and algae were also found to be very different between high (H'=0.547) and low pools (H'=1.213). The species composition of the pools was also found to be important in determining the differences between high and low pools. Lopez, Ramon, “Relationship between the nesting and the depredation of Olive Ridley Turtle, Lepidochelys olivacia, with respect of Lunar Phases and Beach Section on Ostional Beach.” Advs. Marta Araúz and Rodrigo Morera. Colorado. 2000. 22pp. Daily counts were taken of new tracks, new nests, and new nests depredated for the olive ridley marine turtle (Lepidochelys olivacea) for the months of March and April 2000. Counts were made over all 7 km of Ostional beach, located in the Ostional National Wildlife Refuge in Guanacaste province, Costa Rica (10°00' N; 85°46' W). The study only considered the tracks and nests made by solitary nesting turtles and did not consider the number of new nests made during the mass reproductive period known as the “arribada.” The counts were compared to the lunar phase for the given date to determine if there was a relationship between olive ridley nesting and lunar phases. Counts were also compared by beach section to determine if there was a difference in the nesting behavior for the different sections of Ostional Beach. In addition, the percentage of tracks that resulted in nests vs. the percentage that did not result in nests (false crawls) was investigated. A survey of 10% of ADIO associates was conducted to gauge the community’s knowledge about nest predators and to elicit suggestions for curbing predation. The waning and new lunar phases had more new tracks and nests than the waxing and full lunar phases. Playa Principal had more new tracks and nests than Playas Norte and Boca. Depredation did not follow a relationship with the lunar phases. Humans, then dogs were the biggest predators of nests. There was no difference between the percentage of “false crawls” for any of the lunar phases, nor for any of the beach sections. Mead, Anne, "The Regeneration and Distribution of a Pacific Coastal Mangrove in Pochote, Costa Rica." Adv. Alvaro Castaing. Colorado. 1995. 37pp. The regeneration of four mangrove species were studied in the Pacific coastal mangrove located in Pochote, Puntarenas, Costa Rica, during March and April of 1995. The sizes of the individuals and distribution of species were studied, as were variables in the soil. Measurements were taken to determine density, frequency, and dominance of the four species found, and soil samples were taken to ascertain the Ph, salinity concentration, and percent organic material for the sites studied in the mangrove. The results of this investigation were that there was recolonization of all four mangrove species found at the sites studied. Neither the Ph nor the salinity concentration readings of the soil were found to have a significant correlation with the distance from the estuary. A slight correlation was found between the distance and the percent organic material, but the results were not conclusive. |
|
Meserve, Jeff, "Coral reef fish communities in Cahuita National Park and Gandoca-Manzanillo National Wildlife Refuge, Limón, Costa Rica." Adv. Bill Szelistowski. Knox 1998. 30pp. Coral reefs in both Cahuita National Park and Gandoca-Manzanillo National Wildlife Refuge have been under heavy impact from natural and anthropomorphic factors for many years. Using a species-time counting technique, fish communities were assessed for both coral reefs. Seven sites were sampled at each reef, with the sites at Cahuita being identical to those used in a 1982 fish community study in the same area. Diversity, evenness, and species richness were virtually identical for both reefs, with 94 species seen at Manzanillo and 89 species seen at Cahuita. The species richness values were lower for Cahuita and Manzanillo than for other Caribbean coral reef fish communities. The dominant families at both reefs were wrasses (Labridae), damselfish (Pomacentridae), and grunts (Haemulidae). Sedimentation, fishing, low live coral coverage and diver carelessness may all be reasons for the low number of fish species found on the reefs. Michael, Sheri, "Experimental Temperature Manipulation of Olive Ridley Sea Turtle (Lepidochelys olivacea) Nests in Artificial Hatcheries in Ostional Wildlife Refuge." Adv. Claudette Mo. Knox. 1993. 17pp. During the dry season in Ostional Wildlife Refuge, hatching success for the olive ridley sea turtle (Lepidochelys olivacea) falls to 0% (from December to May). The majority of the town is dependent on the income from the legal harvesting and selling of the turtle eggs. In order to promote the survival of the species, it is beneficial to construct a hatchery in which the turtle eggs can be guarded from predators and maintained in an environment which could increase hatching success. Temperature and humidity were manipulated in two experimental hatcheries to provide guidelines to share with the town for future use. Hatching success for both hatcheries was 0%. Embryonic mortality in the hatchery by the estuary was attributed to extreme moisture from high tides and decomposition of the eggs in the other hatchery resulted from crab, ant and larvae predation. Suggestions for further studies include the use of a double cylinder for the artificial nest to reduce crab predation, examination of other possible sites to build the hatcheries and measurement of different variables. Michalowski, Jennifer, "Mammalian Predation in Relation to Egg Development in Olive Ridley (Lepidochelys olivacea) Nests at Playa Nancite, Costa Rica". Adv. Claudette Mo. Grinnell College. 1997. 11pp. This study follows the predation of olive ridley sea turtle, Lepidochelys olivacea, eggs during March and April, 1997, at Playa Nancite, Guanacaste, Costa Rica. The focus of the research was to determine which egg stages are found most frequently among predated nests, and whether rotten eggs are eaten, or merely dug up and abandoned. A further aspect of the research considered whether new nests were most likely to be predated on the night of nesting, due to the visual clues provided to predators by turtle tracks. By determining predator species through excavation patterns and tracks and opening eggs to determine stage of development, it was found that nests containing rotten eggs are opened most frequently by coyotes, Canis latrans, and coatis, Nasua narica, and that raccoons, Proycon lotor, most frequently open new nests (nests that have been laid within three days). Observations suggests that coyotes do not always eat the rotten eggs in the nests they open. There was no significant difference found in the number of nests predated on the night of nesting as compared to the following two nights, before an embryo begins to develop. Myers, Mark, "A survey of the fish communities of Playa Blanca (Punta Leona, Costa Rica) with correlations to habitat parameters." Adv. Christopher Vaughan. 1995. Kenyon College. 39pp. In March and April of 1995, a total of 12,930 fish of 54 species were counted within six 500m2 transects in the Playa Blanca area (Punta Leona, Costa Rica). Average fish community diversity (Simpson's index) of the six transects ranged from 2.87 to 9.51; average richness, from 4.3 to 25.1. Community diversity was positively correlated with 6 physical (shelter index, rock %, medium and large caves, vertical walls, and canyons) and 7 biotic (2 algas, 2 anthozoas, 1 hydroid, 1 polychaeta, 1 tunicate) habitat parameters. Negative correlations between community diversity and 1 physical (sand %) and 1 biotic (1 plant) habitat parameter were revealed. The Cortez Damsel had the most positive correlations with habitat parameters (10), while the Blackspot Mojarra had the most negative correlations (6). Nelson, Kristen, "Predation of Olive Ridley (Lepidochelys olivacea) Nests by Vertebrates and Crabs at Playa Nancite, Costa Rica." Adv. Claudette Mo. Macalester. 1996. 14pp. This study documents the predation of olive ridley sea turtle (Lepicochelys olivacea) nests on Playa Nancite, Guanacaste Conservation Area, Costa Rica. Data were collected between February 27 and April 24. Predator frequency was determined by examining predated nests for tracks and distinctive ways of excavation. The date, egg development stage, number of crab holes within a one meter radius leading to the nest, and predator were recorded for each predated nest found. The predators in decreasing order of frequency were coyote (Canis latrans), racoon (Procyon lotor), coati (Nasua narica), humans (Homo sapiens sapiens), and caracara (Polyborus plancus). It was found that predation during the rainy season by vertebrates was not related to predation by ghost crabs (Ocypode occidentalis). Nest stage of embryonic development was related to type of predator. There was not a significant difference between number of nests predated, frequency of predators, and nest stages predated before and after an arribada. |
|
Nowak, Gretchen, "Comparison of Nest Predation Frequencies of the Olive Ridley Sea Turtle (Lepidochelys olivacea) by Vertebrate Predators at Playa Nancite, Costa Rica." Adv. Claudette Mo. Colorado. 1994. 12pp. During March and April, 1994, the vertebrate predation on the nests of the olive ridley sea turtle (Lepidochelys olivacea) in Playa Nancite, Santa Rosa National Park, Costa Rica were observed. Taking data several times daily, the frequencies in which different species visited the nests in relation to arribada dates, moon phases, time of depredation, and nest location were observed. By order of frequency, coyotes (Canis latrans) (46.68%), coati mundis (Nasua narica) (33.40%), and raccoons (Procyon lotor) (19.92%) excavated a total of 527 nests. From the information gathered, I was able to determine if any of these factors had significance in the amount of nest depredation on Playa Nancite. Because research was conducted during the dry season, on such an isolated and protected beach, I found data that differs from that influenced by unnatural factors or data collected during the rainy season. Paynter, Clara K., “A Comparison in Biomass, Density, and Productivity of Thalassia testudinum, Turtle Grass, Between Three Sites in Cahuita National Park, Limón, Costa Rica.” Adv. Jorge Cortés. Colorado. 1999. 15pp. The basic ecology of seagrass beds was investigated by comparing biomass, productivity and density of Thalassia testudinum (turtle grass) between three sites in Cahuita National Park, Costa Rica: Puerto Vargas, Punta Cahuita, and Rio Perezoso. Biomass cores, substrate samples, growth rate, and density samples were taken over a two month time period during which air temperature, water temperature, visibility, water depth, and salinity were monitored. Aboveground biomass, density, and areal productivity were highest in the Puerto Vargas site while Punta Cahuita had the least non-green aboveground biomass and was significantly lower in total biomass than Puerto Vargas. Punta Cahuita was distinguished by the largest sediment size, a very hard substrate, and shallower water. Rio Perezoso, on the other hand, had extremely fine sediment and lower salinity, while Puerto Vargas was intermediate both in sediment size and environmental conditions. It appears, therefore, that higher biomass and productivity result from a combination of moderate environmental characteristics and an intermediate sediment size. Reistetter, Joseph, "Marine Habitat Distribution in the Gandoca-Manzanillo Wildlife Reserve, Costa Rica: a Geographic Information Systems Mapping Project." Advisor: Ana Fonseca. Beloit College. 2005. 18pp. In 1985, Costa Rica created the Gandoca-Manzanillo Wildlife Refuge in the southern Caribbean region. The refuge includes marine and terrestrial habitats that contain high levels of biodivesity. To date the region remains relatively unstudied. In order to assist future investigations and provide a common document to gather the results of other studies in the area, a marine habitat distribution map was created using a geographic information system (GIS) software package, ILWIS. Field data was gathered in March and April of 2005 outside the town of Manzanillo. Transects were performed of the bay between Punta Uva and Punta Manzanillo, and at each point in the transect a GPS point was taken, the substrate noted (sand, reef cement, or sea grass bed), and the percent of algal and live hard coral cover estimated. Using these data and digitized aerial photographs taken of the area in 1998 the map was created in the ILWIS software package. The map was drawn using two substrate classes, reef cement and sand, and had an accuracy of 72 percent. However, it was not possible to create a map estimating algal cover and live hard coral cover accurately due to the insufficent resolution of the digital image and low water clarity. The maximum observed live hard coral cover was 25 percent, and 20 percent of the points where reef cement was observed had more than 50 percent algal coverage. Seidenfeld, Rebecca, "Analysis of Neonate Predation of the Leatherback Marine Turtle (Dermochelys coriacea) and the Olive Ridley Marine Turtle (Lepidochelys olivacea) at Playa Grande, Costa Rica." Adv. Claudette Mo. Lake Forest. 1995. 13pp. During March and April of 1995, I studied predation upon leatherback (Dermochelys coriacea) and olive ridley (Lepidochelys olivacea) neonates at Playa Grande, Las Baulas National Park, Costa Rica. I recorded the frequency of neonate predation, species of predator, lunar phases, and zones of the beach in which predation occurred. The three predators observed were raccoons (Procyon lotor), domestic dogs (Canis familiaris), and crabs (Ocypoda ceratopthalamus and Gecaricinus quadratus). Lunar phases showed no correlation with predation. Observed rates of predation for each predator were different than expected ones. Predation was not correlated with zones of the beach with a high nesting rate. It is interesting to note that this study exposes inferences to neonate predation in highly domesticated areas of the beach, where a low nesting density is found. My data differ from other data collected on neonate predation because it was conducted at the end of the nesting season, on a beach which is protected but highly influenced by human factors. Stendahl, Dan, "Success of Dermochelys coriacea Hatchlings During Two Months of the El Niño Season at Playa Grande, Costa Rica." Adv. José Manuel Mora. Colorado. 1998. 10pp. Emergent Dermochelys coriacea hatchlings were observed at Playa Grande, Costa Rica, in March and April of 1998. Nests were excavated and nest success data was recorded, along with nest depth and distance from vegetation. Five hundred gram sand samples were also taken. Only six emergent nests were found, none of which were in April. Three of the six nests were located to produce complete nest success data. Of all yolked eggs, 25.1% produced hatchlings, 8.9% produced hatclings found dead in nests, 40.9% produced incomplete embryos, 2.5% were victim to fly larvae and thus unable to be identified in development, and 22.7% showed no observable development. Causes of this low hatchling success remain unknown, but the high tides observed to inundate all nests and unusually high temperatures attributed to the El Niño phenomenon may have played a inhibitive role in egg development. Weber, Mark, "The Feeding Biology and Daily Activity Pattern of the Brittlestar Ophiocoma aethiops." Adv. William Szelistowski. Coe. 1990. 32pp. The daily activity pattern of Ophiocoma aethiops was studied at Curú National Wildlife Refuge from April to May 1990. This species is found under intertidal and subtidal rocks during the day, but at night extends its arms from the rocks. Experiments were conducted to understand how this behavior may be related to predation avoidance, feeding, and movement patterns. In the field tethering experiments, one hundred percent predation during the day (vs 13% during the night), strongly suggested predation as a major factor influencing the daily activity pattern. Ophiocoma aethiops used mucus spine suspension feeding and deposit podia mechanisms (which are adaptive to the constantly changing tide levels). Both methods involve arm extension which suggests feeding occurs during the night. An analysis of stomach contents of specimens collected from low tides at 3 h intervals showed that stomach contents were consistently the same throughout a 24 h period and consisted primarily of sand, unidentifiable pieces, and filmentous algae. The digestion indices for filamentous algae was significantly higher during the day supporting daily activity patterns for feeding. There was a significant difference between time intervals for proportion of brittlestars feeding in 1989 and 1990 and for percentage of stomach fullness in 1990. Recapture of brittlestars in a movement pattern experiment revealed six of them moved to adjacent rocks and seven unmarked ones appeared. |
|
Weber, Naomi, "Predation Frequencies of Leatherback Sea Turtle (Dermochelys coriacea) Nests on Playa Grande, Costa Rica." Adv. Claudette Mo. Colorado College. 1995. 13pp. This study documents the predation of leatherback sea turtle (Dermochelys coriacea) nests on Playa Grande, Guanacaste, Costa Rica. Information was collected between March 11 and April 24 of 1995. The frequency of predation and type of predator was determined using animal tracks around opened nests. For each nest data were taken on the location, date, moon phase, predator species, and species sequence. The most frequent predators were found to be; dogs (Canis familiaris), raccoons (Procyon lotor), and crabs (Gecaricinus quadratus, Ocypoda ceratopthalamus and Ocypoda kuhlii). Crabs preyed where nests were most abundant. However, dogs and raccoons only opened nests near human developments. Of all predators, crabs seemed to prey most heavily. There was no significant difference between predation frequencies of dogs and raccoons. External factors, such as moon phase, did not alter frequency of predation on Playa Grande. Willis, Samuel, "Richness, Diversity, Equitability, and Distribution of the Mollusc Community of Manuel Antonio National Park, Costa Rica." Adv. Jorge Cortéz. Macalester College. 1995. 16pp. A study was undertaken to document the species richness, diversity, and distribution of Manuel Antonio National Park, Manuel Antonio, Costa Rica. The study focused on the rocky intertidal zone, however, it included observations of these aspects of the mollusc community of the mangrove, beach, and marine communities of the park. The study took place in March and April of 1995. Seventy-eight mollusc species were identified and documented in the park. An additional approximation of thirty micromollusc species were collected, but not identified. Richness is compared with a previous study of the species of Costa Rica (Bakus, 1968). Attempts are made at explaining patterns noticed in diversity and equitability between different areas of the park. Withey, John, "Predation and Vertical Distribution of Four Snail Species in a Tropical Mangrove Estuary". Adv. William Szelistowski. Pomona. 1990. 34pp. The relationship between vertical distribution and susceptibility to predation in the mangrove snails Littorina fasciata, L. varia, Thais kiosquiformis, and Cerithium stercumuscarum was studied in a small mangrove estuary in the Gulf of Nicoya, Costa Rica. Vertical distributions on roots at low tide during the day decreased in the order L. fasciata > L. varia > Thais > Cerithium. At night L. varia was lower on the roots than Thais but L. fasciata and Cerithium maintained the same relative zones. All L. fasciata and some L. varia avoided submergence during high tides at night, but all Thais, Cerithium, and some L. varia remained underwater. At high tide L. fasciata was significantly higher above the water level than L. varia. Wyckoff, Chris, "The Effects of Terrigenous Sedimentation on the Health of the Coral Reef at Cahuita National Park, Costa Rica." Advisor: Jorge Cortés. Ripon College. 2004. 44 pp. The coral community and the level of sedimentation were studied at Cahuita National Park, Cahuita, Costa Rica. Eleven line transects were done to determine coral community makeup and health, and all individuals of Diadema antillarum, the Long-Spined Urchin, were counted within a meter of the transect line. Seawater samples were filtered to determine suspended particulate matter (SPM) levels, and samples of bottom sediments and of the beaches were analyzed for non-carbonate fraction and grain size distribution. Coral cover and D. antillarum numbers have risen from 1993 levels but are still lower than levels observed in 1980. Coral species abundance has changed with a significant decline of Agaricia agaricites, Lettuce Coral, and a significant rise in Diploria clivosa, Knobby Brain Coral. Siderastrea siderea, Massive Starlet Coral, is now the most dominant coral on the reef. A significant positive relationship was found between numbers of D. antillarum and coralline algae and a significant negative relationship was found with fleshy algae. SPM levels are higher and percent non-carbonate material is similar to both of the previous studies. The rise in both sediment levels and live coral coverage over the last ten years may indicate that other factors besides sedimentation, e.g. D. antillarum die-offs and the 1991 earthquake, may have had a bigger impact than previously thought in the drop in coral cover from 1980 to 1993. This study also shows that D. antillarum is a crucial species of the coral ecosystem and their numbers should be monitored closely. |
|
Return to top of page Go
to: Natural sciences
... agricultural sciences ...
botany ... chemistry
... entomology ... environmental
studies ... geology ... marine
biology ... ornithology ...
zoology |
updated 10/10/06
|
|
||