Macroalgae reduces survival of nursery‐reared Acropora corals in the Florida reef tract

Recent declines in coral populations along the Florida reef tract have prompted the establishment of coral restoration programs which raise coral species, such as the threatened Acropora cervicornis, in nurseries ready for outplanting. Large numbers of nursery‐reared coral colonies have been outplanted along the Florida reef tract in recent years, yet few studies have characterized benthic habitats that are considered optimal for colony survival. In 2016, we surveyed 23 A. cervicornis restoration sites, located at six different reefs in the upper Florida Keys. We examined the condition of the outplanted corals and quantified the benthic assemblages adjacent to the outplanted coral colonies. We found that where A. cervicornis survived for more than 1 year, the substrate significantly supported less brown macroalgae of the genus Dictyota than at sites where A. cervicornis had died. Coral survival was highest at sites with less than 15% Dictyota cover. These results suggest that the habitat conditions that supported Dictyota spp. were not conducive to A. cervicornis growth and survival. Restoration practitioners should avoid attaching nursery‐raised corals to substrate with Dictyota spp. cover greater than 15%.     

Ecological impacts of coral gardening outplanting in the Maldives

As coral reefs continue to degrade at an alarming rate, coral restoration efforts are increasing worldwide in an attempt to keep up with the global challenge of preserving these iconic ecosystems and the many services they provide. Coral gardening, the farming and outplanting of coral fragments, is a commonly applied practice; however, regional validation is required before upscaling can be considered. This study follows up from the successful farming of fragments in mid-water rope nurseries, by reporting on the successive outplanting of these corals. Specifically, 60 Pocillopora verrucosa colonies were outplanted to a degraded reef at different depths (1–12 m), applying three arrangement patterns (equal, clustered, random). After 1 year, 72% were considered successfully outplanted (alive and still attached), with detachment being the main challenge at wave-impacted shallow depths, while loose coral rubble caused more partial mortality at depth. Outplanting stress was observed at 1–6 m depth, but had no impact on survival or growth. Drupella sp. predation was most common at 3 m and 79% of colonies hosted mutualistic fauna after 1 year. Outplanting significantly benefitted the reef environment with a higher fish abundance and diversity along with a higher increase in natural coral cover (H = 2.7; 6.2% increase) in comparison with the control sites. These are promising results, considering that the restoration site has shown little natural recovery in the last few years (coral cover <4%). We hope that our findings provide useful initial insights and help to guide effective restoration practices in the Maldives.     

Parrotfish predation on massive Porites on the Great Barrier Reef

Parrotfish grazing scars on coral colonies were quantified across four reef zones at Lizard Island, Northern Great Barrier Reef (GBR). The abundance of parrotfish grazing scars was highest on reef flat and crest, with massive Porites spp. colonies having more parrotfish grazing scars than all other coral species combined. Massive Porites was the only coral type positively selected for grazing by parrotfishes in all four reef zones. The density of parrotfish grazing scars on massive Porites spp., and the rate of new scar formation, was highest on the reef crest and flat, reflecting the lower massive Porites cover and higher parrotfish abundance in these habitats. Overall, it appears that parrotfish predation pressure on corals could affect the abundance of preferred coral species, especially massive Porites spp, across the reef gradient. Parrotfish predation on corals may have a more important role on the GBR reefs than previously thought.     

Differential survival of nursery‐reared Acropora cervicornis outplants along the Florida reef tract

In recent decades, the Florida reef tract has lost over 95% of its coral cover. Although isolated coral assemblages persist, coral restoration programs are attempting to recover local coral populations. Listed as threatened under the Endangered Species Act, Acropora cervicornis is the most widely targeted coral species for restoration in Florida. Yet strategies are still maturing to enhance the survival of nursery‐reared outplants of A. cervicornis colonies on natural reefs. This study examined the survival of 22,634 A. cervicornis colonies raised in nurseries along the Florida reef tract and outplanted to six reef habitats in seven geographical subregions between 2012 and 2018. A Cox proportional hazards regression was used within a Bayesian framework to examine the effects of seven variables: (1) coral‐colony size at outplanting, (2) coral‐colony attachment method, (3) genotypic diversity of outplanted A. cervicornis clusters, (4) reef habitat, (5) geographical subregion, (6) latitude, and (7) the year of monitoring. The best models included coral‐colony size at outplanting, reef habitat, geographical subregion, and the year of monitoring. Survival was highest when colonies were larger than 15 cm (total linear extension), when outplanted to back‐reef and fore‐reef habitats, and when outplanted in Biscayne Bay and Broward–Miami subregions, in the higher latitudes of the Florida reef tract. This study points to several variables that influence the survival of outplanted A. cervicornis colonies and highlights a need to refine restoration strategies to help restore their population along the Florida reef tract.     

Potential feedback between coral presence and farmerfish collective behavior promotes coral recovery

Stable between‐group differences in collective behavior have been documented in a variety of social taxa. Here we evaluate the effects of such variation, often termed collective or colony‐level personality, on coral recovery in a tropical marine farmerfish system. Groups of the farmerfish Stegastes nigricans cultivate and defend gardens of palatable algae on coral reefs in the Indo‐Pacific. These gardens can promote the recruitment, growth, and survival of corals by providing a refuge from coral predation. Here we experimentally evaluate whether the collective response of farmerfish colonies is correlated across intruder feeding guilds – herbivores, corallivores and egg‐eating predators. Further, we evaluate if overall colony responsiveness or situation‐specific responsiveness (i.e. towards herbivores, corallivores, or egg‐eaters in particular) best predicts the growth of outplanted corals. Finally, we experimentally manipulated communities within S. nigricans gardens, adding either macroalgae or large colonies of coral, to assess if farmerfish behavior changes in response to the communities they occupy. Between‐group differences in collective responsiveness were repeatable across intruder guilds. Despite this consistency, responsiveness towards corallivores (porcupinefish and ornate butterflyfish) was a better predictor of outplanted coral growth than responsiveness towards herbivores or egg‐eaters. Adding large corals to farmerfish gardens increased farmerfish attacks towards intruders, pointing to possible positive feedback loops between their aggression towards intruders and the presence of corals whose growth they facilitate. These data provide evidence that among‐group behavioral variation could strongly influence the ecological properties of whole communities.     

Microhabitat characteristics of <Emphasis Type="Italic">Stegastes planifrons</Emphasis> and <Emphasis Type="Italic">S. adustus</Emphasis> territories

Stegastes adustus and Stegastes planifrons are two species of damselfishes commonly found in the Caribbean. These territorial fishes have been widely studied due to their major ecological role on coral reef in controlling the growth of macroalgae that compete with corals for space and, inversely, on their deleterious role in destroying coral tissues to impulse the development of algae. However, few studies were conducted on the biotic and abiotic components of their territories. In the present study, territory size and surfaces of benthic components (macroalgae, algal turf, massive corals, branching corals, Milleporidae, sponges, sand and rubbles) were estimated for the two species at two contrasted sites. At Ilet Pigeon site (IP), the two damselfishes were found at different depth and exhibited different territory sizes. S. adustus defended a larger territory characterized by massive corals, sand and Milleporidae, while S. planifrons territories were smaller, deeper and characterized by branching corals, sponges and rubble. At Passe-à-Colas site (PC), the two fish species coexisted in the same depth range and defended territories of similar size. Their territories presented higher proportions of macroalgae, but smaller surfaces of Milleporidae than at IP. At PC, the main difference between the two species was a higher surface of massive corals inside S. planifrons territories than S. adustus territories. Differences in microhabitat characteristics between the two Stegastes seemed mostly site related. This resulted from the high plasticity of two species, allowing them to persist on Caribbean coral reefs after the decline of most branching acroporids, their former favorite habitats.     

Genotypic diversity and distribution of Ostreobium quekettii within scleractinian corals

The green filamentous endolithic alga Ostreobium quekettii resides inside skeletons of scleractinian corals in close proximity with their tissue and plays a role in the viability of the coral and its associates. This study examined the distribution and diversity of O. quekettii within scleractinian corals from the Red Sea (Eilat, Gulf of Aqaba), using a molecular phylogenetic marker. The massive coral species Porites lutea and Goniastrea perisi were sampled from a depth range of 6–55 m, and ribulose 1,5-bisphosphate carboxylase large subunit gene (rbcL) DNA sequence of the alga was amplified and analyzed for diversity and distribution of ecological patterns. This work reveals that O. quekettii has at least seven different clades distributed along a depth gradient in the examined scleractinian corals. Among the seven identified clades, four were found only in P. lutea, while the other two clades are found in both P. lutea and G. perisi. Goniastrea perisi colonies at depth of 30 m had a distinct O. quekettii clade that was absent in P. lutea. It is obvious from this study that the green endolithic alga O. quekettii is not a single genotype as previously considered but a complex of genotypes and that this differentiation is of ecological significance.     

Feasibility of early outplanting of sexually propagated Acropora verweyi for coral reef restoration demonstrated in the Philippines

Over the last 20 years, coral sexual propagation techniques for reef restoration have been steadily developed and improved. However, these techniques involve considerable time and costs to grow coral propagules. There is a need to examine the optimal size of juvenile corals for outplantation. Here, we outplanted sexually propagated small (3–5 mm diameter) and large (10–15 mm diameter) Acropora verweyi corals at 4 months after fertilization at two sites in northwestern Philippines, and compared their survival and radial growth rate after a year. A. verweyi coral juveniles (n = 240) exhibited an overall mean survival of 29.5% and growth rate of 11.12 ± 6.2 mm/year (mean ± SD). Large colonies had a significantly higher growth rate than smaller colonies. Although survivorship of large juveniles was significantly better than that of the smaller ones at one site, it did not differ significantly at the other. Each 4‐month‐old coral cost US$1.52 to produce, while the cost of each of the outplanted juveniles (n = 240) was about US$2.67, whereas the cost of each survivor about a year after outplantation was US$11.47. Results suggest that A. verweyi reared in ex situ nurseries for only 4 months can survive reasonably well when outplanted onto coral reefs.     

Coral microbiome diversity reflects mass coral bleaching susceptibility during the 2016 El Niño heat wave

Repeat marine heat wave‐induced mass coral bleaching has decimated reefs in Seychelles for 35 years, but how coral‐associated microbial diversity (microalgal endosymbionts of the family Symbiodiniaceae and bacterial communities) potentially underpins broad‐scale bleaching dynamics remains unknown. We assessed microbiome composition during the 2016 heat wave peak at two contrasting reef sites (clear vs. turbid) in Seychelles, for key coral species considered bleaching sensitive (Acropora muricata, Acropora gemmifera) or tolerant (Porites lutea, Coelastrea aspera). For all species and sites, we sampled bleached versus unbleached colonies to examine how microbiomes align with heat stress susceptibility. Over 30% of all corals bleached in 2016, half of which were from Acropora sp. and Pocillopora sp. mass bleaching that largely transitioned to mortality by 2017. Symbiodiniaceae ITS2‐sequencing revealed that the two Acropora sp. and P. lutea generally associated with C3z/C3 and C15 types, respectively, whereas C. aspera exhibited a plastic association with multiple D types and two C3z types. 16S rRNA gene sequencing revealed that bacterial communities were coral host‐specific, largely through differences in the most abundant families, Hahellaceae (comprising Endozoicomonas), Rhodospirillaceae, and Rhodobacteraceae. Both Acropora sp. exhibited lower bacterial diversity, species richness, and community evenness compared to more bleaching‐resistant P. lutea and C. aspera. Different bleaching susceptibility among coral species was thus consistent with distinct microbiome community profiles. These profiles were conserved across bleached and unbleached colonies of all coral species. As this pattern could also reflect a parallel response of the microbiome to environmental changes, the detailed functional associations will need to be determined in future studies. Further understanding such microbiome‐environmental interactions is likely critical to target more effective management within oceanically isolated reefs of Seychelles.     

Chronic parrotfish grazing impedes coral recovery after bleaching

Coral bleaching, in which corals become visibly pale and typically lose their endosymbiotic zooxanthellae (Symbiodinium spp.), increasingly threatens coral reefs worldwide. While the proximal environmental triggers of bleaching are reasonably well understood, considerably less is known concerning physiological and ecological factors that might exacerbate coral bleaching or delay recovery. We report a bleaching event in Belize during September 2004 in which Montastraea spp. corals that had been previously grazed by corallivorous parrotfishes showed a persistent reduction in symbiont density compared to intact colonies. Additionally, grazed corals exhibited greater diversity in the genetic composition of their symbiont communities, changing from uniform ITS2 type C7 Symbiodinium prior to bleaching to mixed assemblages of Symbiodinium types post-bleaching. These results suggest that chronic predation may exacerbate the influence of environmental stressors and, by altering the coral-zooxanthellae symbiosis, such abiotic-biotic interactions may contribute to spatial variation in bleaching processes.     

Spatial and temporal variation in coral predation by parrotfishes on the GBR: evidence from an inshore reef

There have been few studies of coral predation by fishes on the Great Barrier Reef (GBR). However, these studies have indicated that it is an important factor that may shape coral demographics. Here, for the first time, we document the spatial and temporal variation in coral predation by parrotfishes on an inshore reef on the GBR. The densities of parrotfish feeding scars on massive Porites spp. were compared within core and non-core areas of three Chlorurus microrhinos home ranges. The density of parrotfish feeding scars on massive Porites is among the highest recorded on the GBR and elsewhere with a higher abundance of excavating feeding scars within core areas, reflecting the higher occupancy of these areas by C. microrhinos. Furthermore, excavating scars were more abundant in October than in April. This may be related to the higher nutritional quality of coral colonies in October, as coral spawning usually occurs in November at this study location. No spatial or temporal variation was noted in the abundance of feeding scars from scraping parrotfishes. The lack of temporal differences may be a result of the shallow scraping scars which would not be able to reach the gonads within coral polyps. The frequency of parrotfish predation on Porites and the spatial and temporal variation recorded herein highlight the potential importance of parrotfish corallivory on the GBR.     

Effects of juvenile coral-feeding butterflyfishes on host corals

Corals provide critical settlement habitat for a wide range of coral reef fishes, particularly corallivorous butterflyfishes, which not only settle directly into live corals but also use this coral as an exclusive food source. This study examines the consequences of chronic predation by juvenile coral-feeding butterflyfishes on their specific host corals. Juvenile butterflyfishes had high levels of site fidelity for host corals with 88% (38/43) of small (<30 mm) juveniles of Chaetodon plebeius feeding exclusively from a single host colony. This highly concentrated predation had negative effects on the condition of these colonies, with tissue biomass declining with increasing predation intensity. Declines were consistent across both field observations and a controlled experiment. Coral tissue biomass declined by 26.7, 44.5 and 53.4% in low, medium and high predation intensity treatments. Similarly, a 41.7% difference in coral tissue biomass was observed between colonies that were naturally inhabited by juvenile butterflyfish compared to uninhabited control colonies. Total lipid content of host corals declined by 29–38% across all treatments including controls and was not related to predation intensity; rather, this decline coincided with the mass spawning of corals and the loss of lipid-rich eggs. Although the speed at which lost coral tissue is regenerated and the long-term consequences for growth and reproduction remain unknown, our findings indicate that predation by juvenile butterflyfishes represents a chronic stress to these coral colonies and will have negative energetic consequences for the corals used as settlement habitat.     

Farming behaviour of reef fishes increases the prevalence of coral disease associated microbes and black band disease

Microbial community structure on coral reefs is strongly influenced by coral–algae interactions; however, the extent to which this influence is mediated by fishes is unknown. By excluding fleshy macroalgae, cultivating palatable filamentous algae and engaging in frequent aggression to protect resources, territorial damselfish (f. Pomacentridae), such as Stegastes, mediate macro-benthic dynamics on coral reefs and may significantly influence microbial communities. To elucidate how Stegastes apicalis and Stegastes nigricans may alter benthic microbial assemblages and coral health, we determined the benthic community composition (epilithic algal matrix and prokaryotes) and coral disease prevalence inside and outside of damselfish territories in the Great Barrier Reef, Australia. 16S rDNA sequencing revealed distinct bacterial communities associated with turf algae and a two to three times greater relative abundance of phylotypes with high sequence similarity to potential coral pathogens inside Stegastes''s territories. These potentially pathogenic phylotypes (totalling 30.04% of the community) were found to have high sequence similarity to those amplified from black band disease (BBD) and disease affected corals worldwide. Disease surveys further revealed a significantly higher occurrence of BBD inside S. nigricans''s territories. These findings demonstrate the first link between fish behaviour, reservoirs of potential coral disease pathogens and the prevalence of coral disease.     

Context-dependent corallivory by parrotfishes in a Caribbean reef ecosystem

This study assesses the patterns of corallivory by parrotfishes across reefs of the Florida Keys, USA. These reefs represent a relatively unique combination within the wider Caribbean of low coral cover and high parrotfish abundance suggesting that predation pressure could be intense. Surveys across eight shallow forereefs documented the abundance of corals, corallivorous parrotfishes, and predation scars on corals. The corals Porites porites and Porites astreoides were preyed on most frequently with the rates of predation an order of magnitude greater than has been documented for other areas of the Caribbean. In fact, parrotfish bite density on these preferred corals was up to 34 times greater than reported for corals on other reefs worldwide. On reefs where coral cover was low and corals such as Montastraea faveolata, often preferred prey for parrotfishes, were rare, predation rates on P. porites and P. astreoides, and other less common corals, intensified further. The intensity of parrotfish predation increased significantly as coral cover decreased. However, parrotfish abundance showed only a marginal positive relationship with predation pressure on corals, likely because corallivorous parrotfish were abundant across all reefs. Parrotfishes often have significant positive impacts on coral cover by facilitating coral recruitment, survival, and growth via their grazing of algae. However, abundant corallivorous parrotfishes combined with low coral cover may result in higher predation on corals and intensify the negative impact that parrotfishes have on remaining corals.     

Toxic coral gobies reduce the feeding rate of a corallivorous butterflyfish on Acropora corals

The obligate coral-dwelling gobiid genus Gobiodon inhabits Acropora corals and has developed various physiological, morphological and ethological adaptations towards this life habit. While the advantages of this coral-fish association are well documented for Gobiodon, possible fitness-increasing factors for the host coral are unknown. This study examines the influence of coral-dwelling gobies on the feeding behaviour of obligate corallivorous butterflyfishes. In an aquarium experiment using video observation, the corallivorous butterflyfish Chaetodon austriacus fed significantly less on corals inhabited by two Gobiodon species compared to unoccupied coral colonies of similar size. The more agonistic species G. histrio, which mostly displayed directed movements towards butterflyfishes, decreased butterflyfish bite rate by 62–98 % compared to uninhabited colonies. For Gobiodon sp. 3, which mostly displayed undirected movements in response to visits by C. austriacus, bite rate reduction was 64–68 %. The scale-less skin of Gobiodon spp. is covered by mucus that is toxic and multi-functional by reducing predation as well as affecting parasite attachment. A choice flume experiment suggests that the highly diluted skin mucus of Gobiodon spp. also functions as a corallivore repellent. This study demonstrates that Gobiodon spp. exhibit resource defence against coral-feeding butterflyfishes and also that coral colonies without resident Gobiodon suffer higher predation rates. Although the genus Gobiodon is probably a facultative corallivore, this study shows that by reducing predation on inhabited colonies by other fishes, these obligate coral-dwellers either compensate for their own fitness-decreasing impact on host colonies or live in a mutualistic association with them.     

<Emphasis Type="Italic">Symbiodinium</Emphasis> associations with diseased and healthy scleractinian corals

Despite recent advances in identifying the causative agents of disease in corals and understanding the impact of epizootics on reef communities, little is known regarding the interactions among diseases, corals, and their dinoflagellate endosymbionts (Symbiodinium spp.). Since the genotypes of both corals and their resident Symbiodinium contribute to colony-level phenotypes, such as thermotolerance, symbiont genotypes might also contribute to the resistance or susceptibility of coral colonies to disease. To explore this, Symbiodinium were identified using the internal transcribed spacer-2 region of ribosomal DNA from diseased and healthy tissues within individual coral colonies infected with black band disease (BB), dark spot syndrome (DSS), white plague disease (WP), or yellow blotch disease (YB) in the Florida Keys (USA) and the US Virgin Islands. Most of the diseased colonies sampled contained B1, B5a, or C1 (depending on host species), while apparently healthy colonies of the same coral species frequently hosted these types and/or additional symbiont diversity. No potentially “parasitic” Symbiodinium types, uniquely associated with diseased coral tissue, were detected. Within most individual colonies, the same dominant Symbiodinium type was detected in diseased and visually healthy tissues. These data indicate that specific Symbiodinium types are not correlated with the infected tissues of diseased colonies and that DSS and WP onset do not trigger symbiont shuffling within infected tissues. However, few diseased colonies contained clade D symbionts suggesting a negative correlation between hosting Symbiodinium clade D and disease incidence in scleractinian corals. Understanding the influence of Symbiodinium diversity on colony phenotypes may play a critical role in predicting disease resistance and susceptibility in scleractinian corals.     

Coral Bioerosion at Enewetak: Agents and Dynamics

Significant differences were found in the extent to which massive coral species at Enewetak are excavated by boring organisms: Goniastrea retiformis, 7.9%; Porites lutea, 2.5%; and Favia pallida, 1.2%. While polychaetes constituted the most abundant and diverse group of coral associates, clionid sponges accounted for approximately 70–80% of skeletal damage. Clionid boring rates are initially very high but burrowing ceases when a particular burrow size (˜0.6 cm) or distance from the surface (≦2 cm) is reached. Most coral skeletal excavation occurs within 2 cm of a dead surface. Therefore, bioerosional damage to corals depends primarily on the amount of skeletal surface not covered by live coral tissue. Damage to skeletons is inversely correlated with colony size but is not correlated with coral growth rates or water depth. Massive corals have a potential escape in size from catastrophic bioerosion. Models relating 1) coral growth forms to skeletal density and stability in currents, 2) resistance of coral skeletons to breakage by water movement and suspended rubble, and 3) dead surface area on coral heads to bioerosional damage and consequent probability of detachment from the substrate, are proposed.     

Outplanting optimized: developing a more efficient coral attachment technique using Portland cement

Coral reefs are among the most valuable and vulnerable ecosystems on Earth. Their decline has spurred global interest in efforts to augment native coral populations through coral gardening. As these efforts expand, practitioners are constantly looking for new techniques to reduce costs and increase their restoration footprint. However, commonly employed coral attachment methods limit the numbers of corals that can be outplanted per day, representing a substantial bottleneck in the coral restoration process. Cement has potential as a more cost‐ and time‐efficient coral attachment technique, but research is needed to understand its effects on coral survivorship and develop best practices for its use. Here, we use lab and field tests in a three‐stage elimination format to determine the most effective cement mixture for outplanting Acropora cervicornis. We then compare this new method to two commonly used coral attachment techniques: the nail and cable tie method and two‐part epoxy putty. Our tests identified the optimal cement mix to be a combination of 10 parts type I/II Portland cement to one part silica fume. This mix yielded equivalent survivorship to the other two methods, is quick and easy to use making it ideal for citizen scientists, and has roughly one‐tenth of the material cost of other methods. These results support the wider use of cement for coral outplanting in order to minimize costs, maximize efficiency, and increase the effectiveness of coral restoration efforts around the world.     

Highly Heterogeneous Bacterial Communities Associated with the South China Sea Reef Corals Porites lutea,Galaxea fascicularis and Acropora millepora

Coral harbor diverse and specific bacteria play significant roles in coral holobiont function. Bacteria associated with three of the common and phylogenetically divergent reef-building corals in the South China Sea, Porites lutea, Galaxea fascicularis and Acropora millepora, were investigated using 454 barcoded-pyrosequencing. Three colonies of each species were sampled, and 16S rRNA gene libraries were constructed individually. Analysis of pyrosequencing libraries showed that bacterial communities associated with the three coral species were more diverse than previous estimates based on corals from the Caribbean Sea, Indo-Pacific reefs and the Red Sea. Three candidate phyla, including BRC1, OD1 and SR1, were found for the first time in corals. Bacterial communities were separated into three groups: P. lutea and G. fascicular, A. millepora and seawater. P. lutea and G. fascicular displayed more similar bacterial communities, and bacterial communities associated with A. millepora differed from the other two coral species. The three coral species shared only 22 OTUs, which were distributed in Alphaproteobacteria, Deltaproteobacteria, Gammaproteobacteria, Chloroflexi, Actinobacteria, Acidobacteria and an unclassified bacterial group. The composition of bacterial communities within each colony of each coral species also showed variation. The relatively small common and large specific bacterial communities in these corals implies that bacterial associations may be structured by multiple factors at different scales and that corals may associate with microbes in terms of similar function, rather than identical species.     

Bio-optical modeling of photosynthetic pigments in corals

The spectral reflectance of coral is inherently related to the amounts of photosynthetic pigments present in the zooxanthellae. There are no studies, however, showing that the suite of major photosynthetic pigments can be predicted from optical reflectance spectra. In this study, we measured cm-scale in vivo and in situ spectral reflectance for several colonies of the massive corals Porites lobata and Porites lutea, two colonies of the branching coral Porites compressa, and one colony of the encrusting coral Montipora flabellata in Kaneohe Bay, Oahu, Hawaii. For each reflectance spectrum, we collected a tissue sample and utilized high-performance liquid chromatography to quantify six major photosynthetic pigments, located in the zooxanthellae. We used multivariate multiple regression analysis with cross-validation to build and test an empirical linear model for predicting pigment concentrations from optical reflectance spectra. The model accurately predicted concentrations of chlorophyll a, chlorophyll c ₂, peridinin, diadinoxanthin, diatoxanthin and β-carotene, with correlation coefficients of 0.997, 0.941, 0.995, 0.996, 0.980 and 0.984, respectively. The relationship between predicted and actual concentrations was 1:1 for each pigment, except chlorophyll c ₂. This simple empirical model demonstrates the potential for routine, rapid, non-invasive monitoring of coral-zooxanthellae status, and ultimately for remote sensing of reef biogeochemical processes.