Algae

On the shore of the Boca Jewfish area of the Lac, Bonaire, N.A., blue-green algae perform a sediment-stabilizing and binding function resulting in a wide variety of cryptalgal structures. The morphology and zonadon of these structures is related to variation in desiccation, sediment influx, water agitation and algal "species." The zunation of intertidal structures consists of stromatolites and oncolites, lithifiod nodules, smooth mat and tufted mat. A cryptalgal crust pavement is found in protected supratidal- areas. In the middle intertidal zone, cryptalgal nodules are lithified during intertidal exposure by pervasive pore-reducing, micritic, high-Mg calcite cement, which is pendent in its distribution around sediment grains. Calcium carbonate cement also occurs as rinds on algal filaments. Precipitated calcium carbonate is found in minor amounts on filaments and mucus within tufted and smooth mats. The preservation potential of the nodules is enhanced by rapid and early cementation. The other structures, not lithified by significant amounts of early cement, have lower preservation potentials. The normal marine salinity of the Lac indicates that growth of cryptalgal structures in fresh, brackish, or hypersaline waters is not essential for their early cementation and lithification.

This study provides a baseline of the marine algal flora composition around St. Eustatius, Dutch Caribbean, by describing algal community structure in terms of species richness and beta diversity, and by providing a taxonomically reliable DNA barcode collection. A total of 156 species was found, including 91 that represent new records for St. Eustatius. Subtidal assemblages (126 species) and intertidal assemblages (48 species) showed little overlap. Algae assemblages in seagrass beds differed from those on hard substrates in species composition. In addition, seagrass communities contained a relatively high number of associated green algae species. Artificial substrates (such as shipwrecks) mimicked natural hard substrates in terms of species richness and composition, but missed some key species that characterize natural reef floras. Species accumulation curves and asymptotic species richness estimators show that the expected species richness is higher than the observed number of species, indicating that additional sampling is needed to record rare species. The phylogenetic trees provided in this study identified the presence of cryptic species and fills knowledge gaps in our understanding of Caribbean macroalgae.

A reoccurring problem facing a majority of the coral reefs in the Caribbean for the past few decades has been the fear of a changing community structure from primarily reef-building corals to algal dominance. A shift in such ecosystems could inhibit coral growth and recruitment, eventually killing corals and lowering the diversity of fish in the area. Recent developments in agriculture and technology have advanced the dispersal of various inorganic nutrients into water systems, where excess nitrogen or phosphorous levels may lead to an increase in algal photosynthesis and thus growth. For my study I looked at relationships between algal growth and nutrient levels in seawater, specifically ammonia and nitrates + nitrites. Using photography and underwater transects I looked for differences in the amount of algae at sites with high or low nutrient levels as measured in March 2006 by the Bonaire Marine Park (BMP). The site with the highest nitrate + nitrite levels had a mean algal cover of 30.6% (std. dev. 30.4), which was not statistically different from the site with lowest concentrations (mean algal cover = 22.9%, std. dev. = 23.1). Algal cover was highest at 18 Palms (mean = 38.6% std. dev. = 39.5), where the lowest ammonia concentration was found. This research showed that nutrient levels did not influence the percent algal cover at my sites. Possible reasons for these findings are discussed.

This student research was retrieved from Physis: Journal of Marine Science I (Fall 2006)19: 21-25 from CIEE Bonaire.

Herbivory drives ecosystem dynamics in both terrestrial and marine habitats, controlling type and biomass of vegetation. In tropical coral reefs, herbivorous fishes and invertebrates feed on benthic macroalgae, resulting in decreased algal biomass and increased hard substratum available for coral growth and recruitment, providing for increased levels of biodiversity. In 1983, the long-spined sea urchin, Diadema antillarum, suffered mass mortality in the Caribbean, resulting in dramatic changes to ecosystem dynamics such as decreased coral cover and increased macroalgal cover. This study aimed to examine the impact of various grazers on algal biomass in areas with and without D. antillarum in Bonaire, Dutch Caribbean, from late February to early April, 2012, using herbivore exclusion cages with varying levels of exclusion. Grazer categories were established based on cage type and proximity to D. antillarum. It was hypothesized that algal biomass would decrease with increased herbivore access. At locations with D. antillarum, there was a general increase in algal biomass with increased exclusion, whereas at locations without D. antillarum, the opposite trend was observed. Algal biomass generally decreased with increased grazer access; however, differences were not statistically significant. Herbivorous fishes removed the highest amount of algae, followed by D. antillarum, and large invertebrates. This study shows the importance of multiple herbivores in maintaining low algal biomass in Bonaire.

This student research was retrieved from Physis: Journal of Marine Science XI (Fall 2012)19: 1-8 from CIEE Bonaire.

Coral reefs are undergoing phase shifts becoming dominated by algae rather than live coral. Algae on reefs is greatly impacted by herbivores such as parrotfish that use both the reef and shallow intertidal zone to feed. These two habitats are unique with differences in algal cover and algal community composition. The shallow intertidal may have greater risk of predation from ospreys and the habitat is more extreme in terms of turbulence and constantly changing microenvironments. It is unknown if feeding in the shallow intertidal zone provides a benefit that offsets the risk of feeding there. This study observed initial and terminal phases Sparisoma viride and Scarus taeniopterus to determine if there are differences in feeding by parrotfish between the shallow intertidal and the reef crest. The main goals of the study were 1) to compare algae from the shallow (higher predation risk) habitat to algae from the deeper (lower predation risk) habitats and 2) to compare abundance of terminal phase and initial phase. Transects at two different depths of 0.5 m and 10 m were placed at 10 different sites on the leeward side of Bonaire, Dutch Caribbean. Point intercept surveys and dry weight of algae samples were used to compare algal cover and fish surveys were conducted to measure parrotfish. Although the shallow intertidal zone had greater algal cover there was not a significant difference in abundance of parrotfish during either developmental stage studied, which may be explained by greater

This student research was retrieved from Physis: Journal of Marine Science XII (Fall 2012)19: 33-38 from CIEE Bonaire.

In recent decades, reduced grazing pressure caused by a die-off of Diadema antillarum and the overexploitation of herbivorous fishes have facilitated a phase shift from coral to algal dominated reefs. Thus, conservation of herbivorous fishes has become increasingly important on coral reefs. In the Caribbean reefs, parrotfish are the dominant herbivores. Studies have been conducted on parrotfish grazing, but there is a lack of knowledge about specific algal preferences. This study examined differences in bite frequencies on algal types and algal preferences of the most common parrotfish species of Bonaire, Dutch Caribbean. Mean bite frequencies (bites 30 min-1 ) and preferences were determined by offering algal plates with Padina sp., Ulva sp., Sargassum sp., and turf algae to parrotfish on the coral reef flat. During field observations, data was collected on the number of bites taken and algal type grazed by each individual parrotfish. Parrotfish as a group, and individual species (Sparisoma rubripinne, Scarus viride, and Sparisoma aurofrenatum), demonstrated significant differences in mean bite frequencies on algal types offered. There were also significant differences in mean bite frequencies among the three parrotfish species. All species of parrotfish, collectively and individually, demonstrated preferences for Padina sp. and avoidances for all other algal types offered. Determining which algal types parrotfish graze, and how grazing differs among parrotfish species is ecologically important. The results provide an understanding of how the selective pressures of specific herbivores may help regulate harmful macroalgae, and suggest the importance of maintaining the diversity of herbivorous fishes on the reef.

This student research was retrieved from Physis: Journal of Marine Science XIV (Fall 2013)19: 110-117 from CIEE Bonaire.

The transition in the Caribbean Sea from coral dominated reefs to algal dominated reefs poses a serious risk to the current existing community. Current research suggests that algal communities will follow a predictable pattern of growth and succession based on the environmental conditions of the community. Depth of the coral head hosting the community and location on the coral head may have a role in succession. This study was conducted on a fringing reef on the leeward side of the island of Bonaire, DC in March of 2014. Algal communities were sampled at two locations on coral heads: just below the livecoral/dead coral interface and between 10 and 30 cm below the first sample. Analysis of genera richness and mass percent of algal divisions were not found to be correlated with depth for all algal divisions. However, richness of Rhodophyta genera was shown to be different between sampling locations on the same coral head and mass percent of Chlorophyta genera was shown to be negatively correlated with distance between sampling locations. The lack of variation found among many of the samples suggests that depth and sampling location on a coral head are largely unimportant in determining the make-up of an algal community, except the aforementioned relationships. Within the framework of creating a predictive model for algal succession, depth and community location on the coral head are components, but more work is needed. The creation of a predictive model will let reef managers forecast future threats and mitigate potential catastrophes.

This student research was retrieved from Physis: Journal of Marine Science XV (Spring 2014)19: 15-20 from CIEE Bonaire.

Coral reefs harbor a vast amount of global diversity relative to their size, and are an important economic resource to coastal communities. Over the past few decades, many coral reefs have undergone a phase shift from a substrate dominated by coral to one dominated by algae, largely due to anthropogenic stress. Herbivorous fishes play a major role in topdown control of algal growth and composition; however, depletion of biomass due to overfishing and habitat degradation has threatened the top-down control of fish herbivory on algal composition. This experiment compared endolithic turf algae (TA) composition on coralline rubble under complete fish exclusion, large fish exclusion (>13 cm), and no fish exclusion treatments. There was a significant increase in growth, richness, and percent cover of TA in response to reduced herbivory. The greatest compositional shift occurred in complete fish exclusion treatments. Crustose coralline algae (CCA), important in coral recruitment and growth, significantly increased in cover under every treatment except complete fish exclusion. This illustrates the importance of large-bodied herbivorous fish in controlling TA growth and maintaining bare substrate to facilitate coral recruitment and growth. This study provided insight into how Caribbean reefs go through initial stages of a phase shift from a coral dominated benthos to one dominated by taller, denser algae. Finally, it illustrates how Bonaire’s reef, currently regarded as one of the most intact in the Caribbean, could change in composition if large herbivorous fish are removed from the ecosystem.

This student research was retrieved from Physis: Journal of Marine Science XVI (Fall 2014)19: 55-65 from CIEE Bonaire.

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.

Stressors causing coral reef degradation are making reefs susceptible to domination by other organisms. One documented phase-shift is increased macroalgal cover of deteriorated reefs. Sponges also have the potential to overtake reefs because of their tolerance for rising temperatures and ocean acidification, ability to outcompete corals for space, and tendency to grow on available substrate created by coral mortality. This study aimed to address gaps in the literature on sponge/coral relationships as well as simultaneously study the interactions between coral and both of its potential competitors. Percentage encrusting sponge cover, percentage algae cover, and encrusting sponge density were compared to percentage live, damaged, and dead coral cover to examine the interactions among coral, sponges, and algae. Sponge/coral interactions were also classified to assess sponge aggressiveness. Data was collected at Yellow Submarine dive site using belt transects and photoquadrats. Although no correlations were significant, most comparisons found that sponges and algae decreased with more live coral cover and increased with more dead coral cover. No significant differences among the abundance of sponge/coral interaction types were found on the reef slope, but there were significant differences present on the reef crest. In both locations, most interactions were not aggressive overgrowth interactions. The relationships among sponges, algae, and coral suggest that both sponges and algae tend to grow on substrate made available by coral death. By examining the interactions of both sponges and algae with coral, comparison of these relationships was possible, potentially prompting future work that also assesses multiple ecologically important interactions.

This student research was retrieved from Physis: Journal of Marine Science XIX (Spring 2016)19: 42-51 from CIEE Bonaire.