Species diversification

A greater understanding of coralbased communities must be achieved in order to maximize reef conservation efforts. While a multitude of studies have analyzed coral reef recovery, resilience of reefs, and artificial reefs versus natural reefs, few have dissected the complex ecological networks of coral-based ecosystems during the first few decades of colonization. The following is a quantitative study of invertebrate and fish communities around a series of offshore mooring blocks in Kralendijk, Bonaire (n=18). These blocks were deployed roughly twenty years ago, are the same size, and are exposed to similar physical conditions. It was hypothesized that there would be positive correlations between coral cover and fish species richness, coral cover and fish species diversity, rugosity and fish species richness, and rugosity and fish species diversity. Visual surveys, photo quadrats, and a slightly modified chain intercept transect method were used to assess fish communities, coral cover, and rugosity, respectively. The results supported the hypotheses with significant positive correlations (p<0.05). Likewise, it was found that fire coral cover displayed significant positive correlation with both rugosity (p=0.005) and fish species diversity (p=0.014), whereas brain coral cover did not show a significant correlation with these two variables. Though these outcomes may have been expected based on the findings of previous studies, the manifestation of such ecology in these relatively young mooring blocks is impressive when compared to the same trends in well-established reefs. While this study constituted only a small window of the intricate field of coral reef ecology, the findings offer manageable insight into the dynamics of young artificial structures.

This student research was retrieved from Physis: Journal of Marine Science XVI (Fall 2014)19: 31-37 from CIEE Bonaire.

The estimated number of species of Moray Eels (Family: Muraenidae) worldwide is around 200. A majority of morays hide in crevices and holes during the day, but come out to forage at night. The amount of activity during the day and night differs between species. Some are strictly nocturnal or diurnal while others are equally present during both times. Morays are generally piscivores and have large impacts on the biomass of reef fishes due to their maneuverability. In some studies, morays have been found to have the largest impact out of all other piscivores regarding the quantity of fishes consumed. In this study we dove at 15 m for 45 min during the day and at sunset three times each (six dives total). We also snorkeled the same distance covered while diving, but shallower along the shoreline. The number and species of moray within a 2-m band while diving and a 1m band while snorkeling were recorded. Spotted morays were the most common species seen overall (87.3% of all morays recorded). The density of morays was the highest while snorkeling (1.38 ± 0.77/10 m2 ). The density of morays while snorkeling was roughly 10 times greater than the day dives and almost 14 times greater than the sunset dives. Smaller morays were seen in the shallows while snorkeling and larger morays were seen while diving. The high number of small morays seen shallower indicates that morays may use shallow habitats as juveniles and move deeper on the reef once they mature and can consume larger prey.

This student research was retrieved from Physis: Journal of Marine Science XVIII (Fall 2015)19: 21-26 from CIEE Bonaire.

Excess nutrients as a result of agricultural, urban, and industrial runoff are major causes to increases in plankton. Coral reefs are nutrient poor environments to begin with; therefore any increase in inorganic nutrients could potentially alter the balance of these ecosystems. Bonaire is suffering from nutrient input in the coastal waters and said trends are expected to increase in subsequent years. Zooplankton diversity and species richness, photosynthetic pigments, water properties and nutrients were measured at two different sites in Kralendijk, Bonaire. The most common taxonomic groups at each site were copepods and siphonophores. The difference in mean turbidity between the two sites was statistically significant (ttest; n = 14; p = 0.002). Excessively turbid water can be explained by an increased plankton population but also by sediment runoff from events such as coastal construction. A possible trend was found between number of zooplankton individuals, chlorophyll a, turbidity, and ammonia nitrogen concentration. This trend could indicate abnormal amounts of runoff entering the waters surrounding Bonaire. Not only is marine management necessary, but also an additional terrestrial aspect to monitor in the form of wastewater and watershed management. Zooplankton taxonomic groups identified during this study could be used as indicators of reef ecosystem health, reproduction success of organisms with planktonic larvae, or predator-prey impact studies such as with pelagic predators of zooplankton. Overall, this study shows important indicators of management for urban areas on Bonaire, but could also contribute to future ecological studies on zooplankton population dynamics around the Caribbean.

This student research was retrieved from Physis: Journal of Marine Science XVIII (Fall 2015)19: 1-9 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.

Abstract

Background: Scleractinian corals and their algal endosymbionts (genus Symbiodinium) exhibit distinct bathymetric distributions on coral reefs. Yet, few studies have assessed the evolutionary context of these ecological distributions by exploring the genetic diversity of closely related coral species and their associated Symbiodinium over large depth ranges. Here we assess the distribution and genetic diversity of five agariciid coral species (Agaricia humilis, A. agaricites, A. lamarcki, A. grahamae, and Helioseris cucullata) and their algal endosymbionts (Symbiodinium) across a large depth gradient (2-60 m) covering shallow to mesophotic depths on a Caribbean reef.

Results: The five agariciid species exhibited distinct depth distributions, and dominant Symbiodinium associations were found to be species-specific, with each of the agariciid species harbouring a distinct ITS2-DGGE profile (except for a shared profile between A. lamarcki and A. grahamae). Only A. lamarcki harboured different Symbiodinium types across its depth distribution (i.e. exhibited symbiont zonation). Phylogenetic analysis (atp6) of the coral hosts demonstrated a division of the Agaricia genus into two major lineages that correspond to their bathymetric distribution (“shallow”: A. humilis / A. agaricites and “deep”: A. lamarcki / A. grahamae), highlighting the role of depth-related factors in the diversification of these congeneric agariciid species. The divergence between “shallow” and “deep” host species was reflected in the relatedness of the associated Symbiodinium (with A. lamarcki and A. grahamae sharing an identical Symbiodinium profile, and A. humilis and A. agaricites harbouring a related ITS2 sequence in their Symbiodinium profiles), corroborating the notion that brooding corals and their Symbiodinium are engaged in coevolutionary processes.

Conclusions: Our findings support the hypothesis that the depth-related environmental gradient on reefs has played an important role in the diversification of the genus Agaricia and their associated Symbiodinium, resulting in a genetic segregation between coral host-symbiont communities at shallow and mesophotic depths.