Browsing by Subject "Coral reefs"
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Item Coral Fluorescent Proteins as Antioxidants(Public Library of Science, 2009-10-06) Palmer, Caroline V.; Modi, Chintan K.; Mydlarz, Laura D.Background -- A wide array of fluorescent proteins (FP) is present in anthozoans, although their biochemical characteristics and function in host tissue remain to be determined. Upregulation of FP's frequently occurs in injured or compromised coral tissue, suggesting a potential role of coral FPs in host stress responses. Methodology/Principal Findings -- The presence of FPs was determined and quantified for a subsample of seven healthy Caribbean coral species using spectral emission analysis of tissue extracts. FP concentration was correlated with the in vivo antioxidant potential of the tissue extracts by quantifying the hydrogen peroxide (H2O2) scavenging rates. FPs of the seven species varied in both type and abundance and demonstrated a positive correlation between H2O2 scavenging rate and FP concentration. To validate this data, the H2O2 scavenging rates of four pure scleractinian FPs, cyan (CFP), green (GFP), red (RFP) and chromoprotein (CP), and their mutant counterparts (without chromophores), were investigated. In vitro, each FP scavenged H2O2 with the most efficient being CP followed by equivalent activity of CFP and RFP. Scavenging was significantly higher in all mutant counterparts. Conclusions/Significance -- Both naturally occurring and pure coral FPs have significant H2O2 scavenging activity. The higher scavenging rate of RFP and the CP in vitro is consistent with observed increases of these specific FPs in areas of compromised coral tissue. However, the greater scavenging ability of the mutant counterparts suggests additional roles of scleractinian FPs, potentially pertaining to their color. This study documents H2O2 scavenging of scleractinian FPs, a novel biochemical characteristic, both in vivo across multiple species and in vitro with purified proteins. These data support a role for FPs in coral stress and immune responses and highlights the multi-functionality of these conspicuous proteins.Item Development of Gene Expression Markers of Acute Heat-Light Stress in Reef-Building Corals of the Genus Porites(Public Library of Science, 2011-10-26) Kenkel, Carly D.; Aglyamova, Galina; Alamaru, Ada; Bhagooli, Ranjeet; Capper, Roxana; Cunning, Ross; deVillers, Amanda; Haslun, Joshua A.; Hédouin, Laetitia; Keshavmurthy, Shashank; Kuehl, Kristin A.; Mahmoud, Huda; McGinty, Elizabeth S.; Montoya-Maya, Phanor H.; Palmer, Caroline V.; Pantile, Raffaella; Sánchez, Juan A.; Schils, Tom; Silverstein, Rachel N.; Squiers, Logan B.; Tang, Pei-Ciao; Goulet, Tamar L.; Matz, Mikhail V.Coral reefs are declining worldwide due to increased incidence of climate-induced coral bleaching, which will have widespread biodiversity and economic impacts. A simple method to measure the sub-bleaching level of heat-light stress experienced by corals would greatly inform reef management practices by making it possible to assess the distribution of bleaching risks among individual reef sites. Gene expression analysis based on quantitative PCR (qPCR) can be used as a diagnostic tool to determine coral condition in situ. We evaluated the expression of 13 candidate genes during heat-light stress in a common Caribbean coral Porites astreoides, and observed strong and consistent changes in gene expression in two independent experiments. Furthermore, we found that the apparent return to baseline expression levels during a recovery phase was rapid, despite visible signs of colony bleaching. We show that the response to acute heat-light stress in P. astreoides can be monitored by measuring the difference in expression of only two genes: Hsp16 and actin. We demonstrate that this assay discriminates between corals sampled from two field sites experiencing different temperatures. We also show that the assay is applicable to an Indo-Pacific congener, P. lobata, and therefore could potentially be used to diagnose acute heat-light stress on coral reefs worldwide.Item Gene Expression Signatures of Energetic Acclimatisation in the Reef Building Coral Acropora millepora(Public Library of Science, 2013-05-09) Bay, Line K.; Guérécheau, Aurélie; Andreakis, Nikos; Ulstrup, Karin E.; Matz, Mikhail V.Background -- Understanding the mechanisms by which natural populations cope with environmental stress is paramount to predict their persistence in the face of escalating anthropogenic impacts. Reef-building corals are increasingly exposed to local and global stressors that alter nutritional status causing reduced fitness and mortality, however, these responses can vary considerably across species and populations. -- Methodology/Principal Findings -- We compare the expression of 22 coral host genes in individuals from an inshore and an offshore reef location using quantitative Reverse Transcription-PCR (qRT-PCR) over the course of 26 days following translocation into a shaded, filtered seawater environment. Declines in lipid content and PSII activity of the algal endosymbionts (Symbiodinium ITS-1 type C2) over the course of the experiment indicated that heterotrophic uptake and photosynthesis were limited, creating nutritional deprivation conditions. Regulation of coral host genes involved in metabolism, CO2 transport and oxidative stress could be detected already after five days, whereas PSII activity took twice as long to respond. Opposing expression trajectories of Tgl, which releases fatty acids from the triacylglycerol storage, and Dgat1, which catalyses the formation of triglycerides, indicate that the decline in lipid content can be attributed, at least in part, by mobilisation of triacylglycerol stores. Corals from the inshore location had initially higher lipid content and showed consistently elevated expression levels of two genes involved in metabolism (aldehyde dehydrogenase) and calcification (carbonic anhydrase). -- Conclusions/Significance -- Coral host gene expression adjusts rapidly upon change in nutritional conditions, and therefore can serve as an early signature of imminent coral stress. Consistent gene expression differences between populations indicate that corals acclimatize and/or adapt to local environments. Our results set the stage for analysis of these processes in natural coral populations, to better understand the responses of coral communities to global climate change and to develop more efficient management strategies.Item Group Decisions in Biodiversity Conservation: Implications from Game Theory(Public Library of Science, 2010-05-27) Frank, David M.; Sarkar, SahotraBackground -- Decision analysis and game theory [1], [2] have proved useful tools in various biodiversity conservation planning and modeling contexts [3]–[5]. This paper shows how game theory may be used to inform group decisions in biodiversity conservation scenarios by modeling conflicts between stakeholders to identify Pareto–inefficient Nash equilibria. These are cases in which each agent pursuing individual self–interest leads to a worse outcome for all, relative to other feasible outcomes. Three case studies from biodiversity conservation contexts showing this feature are modeled to demonstrate how game–theoretical representation can inform group decision-making. Methodology and Principal Findings -- The mathematical theory of games is used to model three biodiversity conservation scenarios with Pareto–inefficient Nash equilibria: (i) a two–agent case involving wild dogs in South Africa; (ii) a three–agent raptor and grouse conservation scenario from the United Kingdom; and (iii) an n–agent fish and coral conservation scenario from the Philippines. In each case there is reason to believe that traditional mechanism–design solutions that appeal to material incentives may be inadequate, and the game–theoretical analysis recommends a resumption of further deliberation between agents and the initiation of trust—and confidence—building measures. Conclusions and Significance -- Game theory can and should be used as a normative tool in biodiversity conservation contexts: identifying scenarios with Pareto–inefficient Nash equilibria enables constructive action in order to achieve (closer to) optimal conservation outcomes, whether by policy solutions based on mechanism design or otherwise. However, there is mounting evidence [6] that formal mechanism–design solutions may backfire in certain cases. Such scenarios demand a return to group deliberation and the creation of reciprocal relationships of trust.Item Investigating complex larval traits in a reef-building coral(2017-08) Strader, Marie Elizabeth; Matz, Mikhail V.; Cummings, Molly; Gross, Jeff; Hofmann, Hans; Mueller, UlrichDispersal of the majority of large benthic marine invertebrates relies on a planktonic phase of the life cycle dispersed by ocean currents. Patterns and spatial scales of larval dispersal drive biogeographic distributions, genetic connectivity and population and community dynamics. Biological parameters that drive dispersal potential include larval traits such as the onset and length of competence, the ability of larvae to metamorphose in response to a specific environmental cue, and the rate of energetic storage depletion. This dissertation examines complex larval traits of a reef-building coral, Acropora millepora, giving insight into how larval trait variation and molecular pathways may contribute to the propensity to disperse. First, I examined whether or not light color (wavelength) acts as a cue to influence the likelihood of settlement and metamorphosis in two species of reef-building coral. I found that exposure to different colored lights impacts the propensity to metamorphose when exposed to chemical settlement cues, and these differences in behavior reflect wavelengths of light roughly associated with their respective habitats. Second, I characterized gene expression differences between three larval fluorescent color morphs in order to elucidate the functional significance of color variation in larvae. I found that red fluorescent larvae have gene expression profiles that correlate with gene expression profiles associated with coral larval thermal tolerance and diapause in other organisms. This suggests that red fluorescent larvae may be physiologically able to exist in the water column longer, potentially dispersing longer distances. Third, I described patterns of gene expression through development and correlated these patterns to competence and fluorescence. This revealed that larval maturation associated with competence is correlated with gene expression of neuropeptide signaling, ion transport and GPCR signaling. Environmental perturbation, such as temperature, may affect these pathways, which could alter larval dispersal dynamics in the sea. Finally, to complement these correlative studies, I developed the first method of genomic manipulation in reef-building corals. Utilizing the CRISPR/Cas9 system induced targeted mutagenesis in candidate genes associated with larval dispersal traits. This work is foundational to study gene functions in an ecological context, which will greatly improve our understanding of coral biology.Item Predicting the influence of source and receiver variation in the use of acoustic cues by larval fishes(2019-02-01) Salas, Andria Kay; Keitt, Timothy H.; Wilson, Preston S.; Altieri, Andrew H; Fuiman, Lee A; Jha, Shalene; Ryan, Michael JSoniferous reef animals produce sound through intentional behaviors like communication and as byproducts of activities like feeding and defending. Sounds from individuals collectively create habitat-specific and temporally variable biological soundscapes. As sounds propagate away from their sources, they may influence larval fishes that use acoustic cues during settlement. Therefore, animal behavior creates spatiotemporally-variable soundscapes, which in turn influence the behavior of fishes during a critical life history transition. These different scales of marine bioacoustics were investigated. The soundscapes across a range of reef quality were recorded for six weeks in an anthropogenically-degraded region of Caribbean Panama. The same contributors to the soundscapes were observed across sites, with taxa-specific variation in spatiotemporal patterns of acoustic behavior. The observed rate of these potential cues was predicted by an individual-based model to improve larval settlement, suggesting resiliency of some components of these acoustic cuescapes. The toadfish Ampicthyses cryptocentrus was a dominant contributor to the soundscapes and showed site-specific temporal variation. Analyses of recordings of ten focal males and males in neighboring burrows demonstrated that males were responsive to multiple neighbors, not just the perceived loudest competitor, and a null model supported that grunts overlapping neighbors’ calls were used as acoustic competition. These results suggest the contribution of toadfish to the soundscape is dependent on both abundance and spatial distribution. Calibrated propagation modelling was used to predict the acoustic fields created by reef-based sounds. It was found that spatial heterogeneity in cue strength increases with frequency and changes with source location, with implications for cue detection. Detection of reef-based cues is enhanced when the otoliths receive energy from the bladder’s response to pressure fluctuations. Changes in bladder size and otolith-bladder distances are likely to create ontogenetic changes in pressure sensitivity, which was tested with a combination of micro-computed tomography and finite-element modelling using larval Sciaenops ocellatus. Otolith-bladder distances increased with fish size, reducing predicted pressure sensitivity. Bladder volume also increased with growth, compensating for increasing distances by partially recovering predicted pressure sensitivity. Combined, these results highlight the system’s complexity: social behavior, spatiotemporal variation, and ontogenetic patterns dynamically influence how soundscapes influence larval behaviorItem The turbulent lives of copepods : how flow over a coral reef affects their ability to detect predators(2006-08) Robinson, Heather Eve; Buskey, Edward Joseph, 1952-Calanoid copepods exhibit rapid escape behavior in response to hydrodynamic stimuli generated by their predators. Currents and turbulence in nature may cause copepods to become less responsive to these stimuli or may otherwise interfere with the detection of predators. Structurally complex environments, such as coral reefs, disrupt water flow and present a range of flow microhabitats varying in both mean and turbulence characteristics. The heterogeneous distribution of flow over the reef may play an important role in the interactions between copepods and planktivorous fish through effects on copepod escape behavior. The escape response and capture rates of the copepod Acartia tonsa were examined in flumes that created both unidirectional and oscillatory flow conditions similar to those found on coral reefs. Copepods were tested in unidirectional flow velocities up to 34.4 cm s-1, which mimicked water currents, and also in oscillatory flow which simulated wave periods of 2.1 seconds. Two turbulent regimes were produced in each flume: "smooth" flow was formed using a grid collimator and "rough" flow was generated by placing a branched coral skeleton upstream of the flume's working section. A predator flow field was simulated by a fixed siphon. Using video analysis, copepod detection of the siphon "predator" was measured as the distance from the siphon tip to where an escape response was initiated. This reactive distance remained the same in low flow conditions as in still water but was reduced 25% in flow speeds of 11.1 cm s-1, indicating a decline in copepods' ability to detect velocity gradients formed by the siphon. Rough turbulence regimes in moderate flow conditions intensified the effect of current speeds by decreasing copepod reactive distance an additional 27%. Capture rates of copepods increased with current speed, wave motion and in rough flow, while the capture rates of non-evasive prey, Artemia nauplii, did not vary with flume conditions. The differences in capture rates between evasive and non-evasive prey suggest that behavioral shifts in copepod escape thresholds may account for increases in predation by reef-dwelling fishes observed in hydrodynamically complex coral environments.