Anthropogenic impact

ABSTRACT: Corals harbor a complex suite of beneficial microbial symbionts. Shuffling the composition of these symbionts could, in theory, help the host withstand rapidly emerging or geographically varying stressors without requiring genetic change to the coral itself. The relative impact of host qualities on microbiome (bacteria) composition should provide insight into the extent that shifting microbial symbionts can play in resilience to environmental disturbance on reefs. We sought to assess the differences in microbiome composition across a large spatial scale (between Puerto Rico and Bonaire; >700 km apart) and in response to localized anthropogenic impacts in 2 co-occurring Caribbean soft corals (Eunicea flexuosa and Gorgonia ventalina) with well-documented differing degrees of population genetic differentiation. Host species was the strongest determinant of microbiome composition, with between-hosts distinction due largely to differences in the abundant genera Endozoicomonas and Mycoplasma. Interestingly, the microbiome of the more genetically subdivided G. ventalina showed stronger differentiation between islands and in response to local anthropogenic impacts than the less subdivided E. flexuosa. For both hosts, anthropogenic impacts on microbiome composition were stronger in Bonaire. Again, Endozoicomonas was responsible for much of the differentiation between and within islands and included host- and island-specific sequence variants. The level of intra-species microbiome variation mirrored the known geographic differentiation of their hosts, a trend that is consistent in the literature for 8 other coral species. Thus, while potentially adaptive bacteria may shuffle in response to environmental changes, our findings suggest that most changes to microbiomes are likely constrained by host genetics.

Final presentation 

Abstract

Human activities can degrade the quality of coral reefs, cause a decline in fish species richness and functional diversity and an erosion of the ecosystem services provided. Environmental DNA metabarcoding (eDNA) has been proposed as an alternative to Underwater Visual Census (UVC) to offer more rapid assessment of marine biodiversity to meet management demands for ecosystem health indices. Taxonomic information derived from sequenced eDNA can be combined with functional traits and phylogenetic positions to generate a variety of ecological indices describing ecosystem functioning. Here, we inventoried reef fish assemblages of two contrasted coastal areas of Cura¸cao, (i) in close proximity to the island’s capital city and (ii) in a more remote area under more limited anthropogenic pressure. We sampled eDNA by filtering large volumes of sea water (2 x 30L) along 2km boat transects, which we coupled with species ecological properties related to habitat use, trophic level and body size to investigate the difference in fish taxonomic composition, functional and phylogenetic indices recovered from eDNA metabarcoding between these two distinct coastal areas. Despite no marked difference in species richness, we found a higher phylogenetic diversity in proximity to the city, but a higher functional diversity on the more isolated reef. Composition differences between coastal areas were associated with different frequencies of reef fish families. Because of a partial reference database, eDNA only partly matched those detected with UVC, but eDNA surveys nevertheless provided rapid and robust species occupancy responses to contrasted environments. eDNA metabarcoding coupled with functional and phylogenetic diversity assessment can serve the management of coastal habitats under increasing threat from global changes.

The bat fauna of the Caribbean island of Sint Eustatius consists of five documented species—Monophyllus plethodon, Brachyphylla cavernarum, Artibeus jamaicensis, Ardops nichollsi, and Molossus molossus—and one provisional species—Tadarida brasiliensis. The Insular Single-leaf Bat, M. plethodon, is reported in the scientific literature for the first time from Sint Eustatius based on material presented herein. The bat fauna of the island is considered to be unbalanced because only three species, which are the environmental generalists, are abundant, whereas the more specialized species are rare or absent from the fauna. It is our hypothesis that the unbalanced bat fauna on St. Eustatius is the result of chronic environmental degradation and destruction due primarily to human activity.

Specific anthropogenic substrates demonstrate the ability to aid new coral growth among Caribbean reefs in Bonaire, N.A. In this study I documented the total percent coral cover on tires, concrete, and metal objects then compared it to nearby natural reef. I also documented the percent cover for individual coral species. Natural substrates exhibited the highest percent total coral cover (mean = 64.5 %), followed by concrete (mean = 21.5 %) and metal (mean = 22.9 %); tires supported the lowest mean coral cover (mean = 3.5 %). Coral species diversity was highest on metal substrates (11 spp.), followed by concrete (9 spp.), natural reef (8 spp.) and tires (2 spp.). These data suggest that concrete may be the most appropriate artificial substrate in efforts to aid reef regeneration and restoration in this region.

This student research was retrieved from Physis: Journal of Marine Science I (Fall 2006)19: 2-6 from CIEE Bonaire.

Phototoxic polycyclic aromatic hydrocarbons (PAHs) have been welldocumented as major marine pollutants. While PAHs are known to have negative ecological effects, the spread of point-source PAHs into coral reefs is poorly understood. This study focuses on a potential source of marine PAH contamination from a drain into a coral reef in Bonaire, Dutch Caribbean. PAHs were believed to be detected outside of the drain between October and November 2013, providing incentive for continued monitoring of PAH presence. Insight from this investigation is important not only to the general understanding of point-source marine pollution pathways, but holds implications for drain management strategies. Water samples from sites of varying distances from the drain were analyzed for UV-reactive toxicity using two Artemia sp. bioassays. Results from the bioassays indicated that PAH presence was undetectable, and that there was no relationship between distance from the drain and UVreactive toxicity. It was concluded that sediment dispersion and marine organism bioaccumulation likely accounted for the apparent temporal discrepancy in PAH presence. Field observations displayed noticeable coral reef degradation, which was assumed to be largely caused by factors other than PAH pollution. Despite the lack of evidence for current PAH presence, observations of poor reef health outside of the drain suggest that further studies and management strategies be considered for the drain and cement trough.

This student research was retrieved from Physis: Journal of Marine Science XVI (Fall 2014)19: 66-73 from CIEE Bonaire.

Coral reef fish larvae use sound to find suitable habitat during their vital settlement stage. Yet boat noise, which can cause stress and avoidance behaviour, and may cause masking via reduction of perceptual space, is common around coral islands and continental shelf habitats due to boat activity associated with fishing, tourism and transport of passengers and cargo. In a choice chamber experiment with settlement-stage coral reef fish larvae of the species Apogon doryssa, the directional responses of larvae were tested to 5 different noise types: Reef, Reef+Boat, Ocean, Ocean+Boat and White noise. The results showed that 69% of fish swam towards Reef playback compared with only 56% during Reef+Boat playback, while 44% of fish larvae moved away from Reef+Boat playback compared to only 8% during Reef playback. Significant directional responses were not observed during White noise, Ocean noise or Ocean+Boat noise playback. Overall, this study suggests that anthropogenic noise could have a disruptive effect on the response of fish larvae to natural reef sound, with implications for settlement and population dynamics in coral reef habitats disturbed by boat traffic.