Coral reefs

With the exception of Elysia crispata, shell-less Sacoglossa species (Order: Mollusca), have been widely studied. Within the Caribbean, these small bodied organisms occur in low population densities, making them hard to find and, in turn, difficult to study. This project served to assess E. crispata abundance, ecology and life history traits on the island of Bonaire. Data collected for this study was conducted by observations from ten 40 m2 transects located at depths of 2.2 m, 7.9 m and 10.7 m. A pair of surveyors recorded the number of individuals found, size of individuals, substrate individuals were located on, and color intensity of individuals within each transect. Overall abundance of individuals found at the study sites were much higher than anticipated. Of the 275 individuals found, the highest population densities were found in shallow transects. The average size of individuals was between 3.0 ± 2.6 cm to 5.0 ± 3.8 cm (mean ± SD) in length, with no correlation between size of individual and coloration. Overall abundance of smaller individuals found on shallower transects could indicate higher densities of preferred substrate within these areas. Roughly 94% of individuals were found on various compositions of turf algae. These results implied that E. crispata were biased towards occupying substrates with turf algae compositions as opposed to other available substrates.

This student research was retrieved from Physis: Journal of Marine Science XVII (Spring 2015)19: 26-33 from CIEE Bonaire.

Processes affecting reef ecosystems have three levels of organization: macroscale, mesoscale and microscale. These processes are conducive to interspecific competition amongst various coral and aggressive invertebrate species. Surveys of these organisms’ distribution, abundance and ecological description of their intra/interspecific competition have been conducted throughout the Caribbean. Previous research has found that scleractinian corals in reef slope ecosystems are frequently outcompeted by sessile aggressive invertebrates, such as Clionid sponges, encrusting bryozoans, encrusting gorgonians and overgrowing mat tunicates. Furthermore, interspecific spatial competition between corals and aggressive invertebrates has been observed to increase in frequency with depth. This project analyzed the distribution and abundance of coral-aggressive invertebrate spatial competition along a fringing reef ecosystem on the west coast of Bonaire. Belt transects were laid out between 200 m north and south of the GPS coordinates N 12°09.6 12’ W 068° 16.9 15’, at two depths (10 and 15 m) along the reef slope. Instances of spatial competition involving individuals at least 10 cm in length were photographed for further analysis. Five coral species and 25 aggressive invertebrate species were encountered in a total of 216 coral-aggressive invertebrate interactions. Quantitative data analysis showed that the orange lumpy encrusting sponge (Scopalina ruetzleri) was the most abundant aggressor at 15 and 10 m, although mean total area covered by coralaggressive invertebrate interactions and their frequency did not increase with depth. Findings could be used as a baseline for future scientific marine research, potentially on growth rate of competing species and the underlying mechanisms responsible for their interspecific spatial competition.

This student research was retrieved from Physis: Journal of Marine Science XVII (Spring 2015)19: 17-25 from CIEE Bonaire.

Coral reef environments exhibit numerous ecological interactions between different organisms. The habitat structure of a healthy coral reef is composed of many different coral species, with various fish species inhabiting the reef. Coral reef studies often focus on a large spatial scale rather than smaller local scale environments within the reef. The objective of this study was to compare fish populations associated with the microhabitat surrounding individual coral heads of two different species. The purpose of this study was to determine if there were differences in fish abundance, fish species richness, and fish diversity between two massive stony corals, Diploria strigosa and Orbicella annularis. These two corals are common on many Caribbean reefs but are morphologically different; therefore, it was hypothesized that they would show differences between their associated fish assemblages. By conducting fish count observations on both D. strigosa and O. annularis, I was able to compare means between the coral associated fish populations using statistical tests. No statistically significant differences were found between these two coral species for mean fish abundance, species richness, or diversity. One possible explanation is that the larger scale reef environment and processes may have a significant effect on local fish populations found on individual coral heads. By studying the microhabitats of coral species and the associated fish assemblages, we can gain a better understanding of fish population dynamics of coral reefs across larger ecological scales—both regionally and globally

This student research was retrieved from Physis: Journal of Marine Science XVIII (Fall 2015)19: 61-69 from CIEE Bonaire.

El Niño Southern Oscillation (ENSO) events are known to bring high sea surface temperatures and in turn cause coral bleaching. The Fall 2015 ENSO event has had record breaking temperatures and has been severely detrimental to Pacific coral reef ecosystems. To gauge the effect this ENSO event would have on the Caribbean, this study looked at the frequency and severity of bleaching and paling, during this ENSO event. The bleaching was measured along a 2 m wide by 10 m long transect. Coral colonies along the transect were observed once a week for four weeks and the water temperature was recorded hourly. At the end of data collection, the overall number of corals experiencing bleaching was recorded and the percent difference in paling and bleaching from week to week was measured. At the end of the four weeks it was found that 60 out of 192 coral colonies were experiencing some form of bleaching. By the fourth week there was no significant increase in bleaching, and paling had significantly increased until week four. This trend followed the decrease of water temperature from week one to week three with signs of coral recovery, but there was also evidence of water temperature starting to increase again by week four.. This study shows the resilience of Bonairean reefs and that this ENSO event may have a lesser affect on the Caribbean coral reefs compared to the Pacific.

This student research was retrieved from Physis: Journal of Marine Science XVIII (Fall 2015)19: 47-52 from CIEE Bonaire.

Marine sponges provide an important link between the benthic and pelagic environments of coral reef ecosystems, yet there is relatively little known about them. Past studies have indicated that depth and size could be contributing factors in tube sponge filter feeding strategies. This study investigated the effects of depth and size on pumping rate and filtering efficiency of Aplysina lacunosa, a common Caribbean reef sponge. At two different depths, several parameters of the sponges were measured: tube length, wall thickness, tissue volume, pumping rate (using fluorescein dye), and filtering efficiency (percent reduction in turbidity between the ostia and osculum). Water samples collected from the water column had similar food availabilities between the two depths. There was a positive relationship between sponge size and pumping rate but not filtering efficiency. Additionally, no relationship was found between depth and sponge pumping rate and filtering efficiency, which is consistent with my finding that food availability did not differ across depths. The filter feeding strategy of A. lacunosa may be unique in the context of other benthic filter feeders in that its pumping rate but not filtering efficiency is affected by size and that neither pumping rate nor filtering efficiency are affected by depth. Further investigations are needed to learn more about the biology of A. lacunosa and its significance to Caribbean coral reefs.

This student research was retrieved from Physis: Journal of Marine Science XVIII (Fall 2015)19: 40-46 from CIEE Bonaire.

Understanding predator-prey relationships gives greater insight into coral reef health. A recent study on predator-prey relationships linked the relative brain mass of predators and their prey. Predation pressure forces prey to use decision making skills that require higher cognition by inspecting and identifying predators and then adjusting their behavior to achieve the highest chance for survival. However, the predation pressure that prey face outweighs the pressure predators face to find a prey. This results in prey having larger relative brain masses than their predators. There is little data on relative brain mass of fishes with few natural predators such as Pterois volitans. This study compared the brain mass to body mass ratio of P. volitans, which have very few natural predators and thus very little predation pressure, to the brain mass to body mass ratio of their prey, possible predators, competitors, and taxonomically similar fish. This study also analyzed the response of lionfish to divers with nets in order to investigate their ability to recognize divers as predators. Lionfish did swim away from divers 56.5% of the time which indicates that lionfish might be able to recognize divers as predators. Lionfish had a significantly smaller relative brain mass than their predators, prey, and competitors, but was not significantly smaller than taxonomically similar fish. These results demonstrate that the morphological antipredator adaptation of venomous spines cause very little predation pressure. Thus, lionfish are not forced to use the same cognitive skills as other prey or predators and in turn have smaller relative brain masses.

This student research was retrieved from Physis: Journal of Marine Science XVIII (Fall 2015)19: 10-20 from CIEE Bonaire.

Marine anemones influence oceanic food webs, partake in symbiotic relationships with many marine phyla, and can prove detrimental to coral reef ecosystems in excess. Few descriptive studies have been conducted on anemone communities. The present study examined anemone abundance and diversity using fluorescence across reef habitats in a coral reef ecosystem for the first time on Bonaire, Dutch Caribbean. A total of 110 fluorescent anemones belonging to at least 9 species were documented. Anemones exhibited species-specific ranges in one or multiple reef habitats including the reef flat (2-6 m depth), reef crest (6-9 m depth), and reef slope (9-15 m depth). Four possibly unidentified species were documented. Fluorescent anemone abundance varied significantly between reef flat (5.5 ± 0.7 individuals) and reef crest (27.5 ± 6.4 individuals) habitats. Although fluorescent anemone diversity was highest on the reef flat and lowest on the reef slope, there was no significant difference among the reef habitats. The study contributed to current knowledge on fluorescent anemone ecology by documenting species habitat ranges. It suggested that among species and as a whole, anemones are habitatspecific. The results also provided habitat ranges for obligate anemone symbionts. The study may be valuable for a variety of scientific fields. Descriptive studies such as the present project in Bonaire facilitate the possible discovery of new and groundbreaking species and model organisms. Tracking distribution and diversity could also inform of anemone bleaching and serve as a bioindicator of reef health and climate change ramifications.

This student research was retrieved from Physis: Journal of Marine Science XIX (Spring 2016)19: 74-84 from CIEE Bonaire.

Raw photo material of the 2016 reef survey using the GCRMN method.

The 20 survey sites lie within the St. Eustatius National Marine Park, which surrounds the island from the high water mark to a depth of 30 meters.  To maximize comparability across the region, GCRMN data was collected solely from forereef habitats at depths ranging from 8 – 15 meters. Sites included the industrialized harbor area along with sites with perceived lower anthropogenic influence on the north and south ends of the island. For each site 5 transects were surveyed. Photographs were taken along the 5 transect lines set for counting fish, capturing 15 images per transect line. Download the summary data of the photo-analysis. See this report for details.

Please contact the DCBD administratorfor access to the raw digital photographs.

The goal of the Global Coral Reef Monitoring Network (GCRMN), an operational network of ICRI, the International Coral Reef Initiative, is to improve data collection, archiving and the network internal functioning for a better diffusion of information on coral reef development and to increase the support for regional and sub-regional cooperation.By applying the GCRMN monitoring methods for a second year, St Eustatius is now on the way to providing scientifically pertinent coral reef data to the Marine Park

The survey location is the St. Eustatius National Marine Park (SNMP), which surrounds the island from the high water mark to a depth of 30 meters.management and the Island Government. To maximize comparability across the region, GCRMN data was collected solely from fore reef habitats at depths ranging from 8 – 18 meters. An effort was made to include sites within the industrialized harbor area along with sites having perceived lower anthropogenic influence on the east, north and south sides of the island. Within the SNMP the 20 sites selected for 2015 were again monitored in 2016:

To follow the health of the coral reefs of Bonaire and Curacao a number of locations on each island are photographed each year since 1973. At each location a 3 m square at up to 4 different depths is recorded.

Please contact the DCBD administratorfor access to the raw digital photographs.