Coral Reef Organisms Research Articles

The reproductive system of the cryptogenic alga Chondria tumulosa (Florideophyceae) at Manawai, Papahānaumokuākea Marine National Monument

ABSTRACT Determining the relative importance of sexual and asexual reproduction is critical for determining how genetic diversity is partitioned within and among populations. Macroalgae exhibit reproductive system variability, with many species capable of both sexual and asexual reproduction. Thus, rates of fragmentation (asexual) versus sporic recruitment (sexual) must be quantified. This is critical during range expansions when shifts to uniparental reproduction are common. Chondria tumulosa is a cryptogenic red alga that was discovered forming thick mats at Manawai, in the Northwestern Hawaiian Islands, during opportunistic sampling in 2019. It reduced the biodiversity and abundance of associated coral reef organisms. To characterize the reproductive system of C. tumulosa in this atoll, we visually assessed 124 thallus clumps for reproductive structures and used five microsatellite loci to genotype 41 thalli. All thalli bearing reproductive structures (20%) and all thalli that were genotyped were tetrasporophytes. No gametophytic thalli were observed using microscopy or microsatellite genotyping, though 80% of thalli observed under the microscope were vegetative. We observed in situ thallus fragmentation supported by the presence of 17 repeated genotypes and other genetic signatures, suggesting high rates of asexual reproduction. These results suggest that C. tumulosa is partially clonal in this atoll and has the potential for spreading to other nearby atolls. Rapid establishment, thallus fragmentation and tetrasporophytic dominance are consistent with other red macroalgal invasions studied to date. Understanding the reproductive system is an important component of developing management strategies for this alga and expanding our understanding of the population genetics of partially clonal taxa.

Novel Interaction between a Rabbitfish and Black Corals

Herbivorous fishes play important functional roles in coral reef ecosystems, and their influence on mediating competitive dynamics between corals and macroalgae is well studied. Nonetheless, direct interactions between herbivorous fishes and corals may also be relevant, although these are less studied. Here, we describe a series of observations of schools of the herbivorous streaked rabbitfish (Siganus javus) nibbling on black corals (order Antipatharia) at the SS Yongala wreck, within the Great Barrier Reef Marine Park. We provide a hypothesis that may explain this behaviour, which, if confirmed, would represent a mechanism influencing the health of the corals. Moreover, this interaction extends the typical coral–algae competition for space paradigm and furthers knowledge of complex relationships between coral reef organisms.

The Habitat Persistence Hypothesis: a new perspective on the distribution of coral-reef organisms

We propose and define the “Habitat Persistence Hypothesis” (HPH) to explain the biogeographical distributions of organisms (especially fishes, invertebrates and algae) inhabiting tropical coral reefs. Both published and unpublished sources indicate that species occurringon deep coral reefs show higher rates of endemism and a less apparent biodiversity gradient across the Pacific Ocean than their counterparts inhabiting shallow coral reefs. The HPH accounts for these biogeographical differences by stipulating that deep reefs are relatively unaffected by sea level changes associated with glacial-interglacial cycles. Shallow-reef habitats may persist across sea level changes in regions with sloped bathymetry (e.g., continental regions and large islands), but are largely extirpated in regions with steep bathymetry (e.g., coral atolls). The HPH suggests that regions with habitat persistence are characterized by higher rates of endemism, and that patterns of attenuating diversity with increasing distance from centers of species richness are shaped by relatively recent recolonization of less persistent habitats from regions with greater habitat persistence. Whereas most existing hypotheses that attempt to explain biogeographical patterns observed on coral reefs (especially in the Indo-Pacific region) relyon observations limited to shallow (<30 m) coral-reef habitat and invoke processes operating on speciation time-scales (107 – 108 yr), the HPH incorporates patterns observed within the remaining 80% of coral-reef habitat (30 – 150 m) and invokes processes operating on time scales associated with sea-level changes (105 – 106 yr). The HPH posits seven specific predictions about coral-reef biogeography that can be directly tested to distinguish it from previous hypotheses. Our intention is to describe the rationale and qualitative support for the HPH with the hope of providing a framework for accumulating sufficient quantitative data to test the predictions, which we anticipate will require decades of robust field surveys.

Limited effects of environmentally-relevant concentrations in seawater of dibutyl phthalate, dimethyl phthalate, bisphenol A, and 4-nonylphenol on the reproductive products of coral-reef organisms

Plastic additives (PAs) are chemical compounds incorporated into the plastic during the manufacturing process. Phthalate acid esters, bisphenols, and nonylphenols are all PAs found in marine environments and associated with endocrine-disrupting processes. However, our knowledge regarding the impact of endocrine-disrupting PAs on coral-reef organisms is limited. As reef population structure is directly linked to reproduction and larval settlement processes, interference with hormonal systems can impact coral-reef community structure, particularly if the effects of PAs differ among species. In the current study we exposed the reproductive products of four tropical coral-reef invertebrates to environmentally-relevant concentrations of four prevalent PAs in seawater: dibutyl phthalate (DBP), dimethyl phthalate, (DMP), 4-nonylphenol (4-NP), and bisphenol A (BPA), as well as to 103 higher laboratory concentrations of these PAs. Our results revealed that apart from the significant negative effect of the 1 μg/L of 4-NP on the settlement of the soft coral Rhytisma fulvum, none of the other tested materials demonstrated a significant effect on the exposed organisms at environmentally-relevant concentrations in seawater. The 4-NP high laboratory concentration (1000 μg/L), however, had significant negative effects on all the examined species. The high laboratory BPA concentration (1000 μg/L) significantly reduced fertilization success in the solitary ascidian Herdmaniamomus, up to its complete failure to reproduce. Moreover, the high laboratory DMP concentration (100 μg/L) had a significant negative effect on planulae settlement of the stony coral Stylophora pistillata. Our findings demonstrate the negative and selective effects of PAs on the development and reproduction of coral-reef organisms; and, specifically, the significant effect found following exposure to 4-NP. Consequently, if we aim to fully understand the impact of these contaminants on this endangered ecosystem, we suggest that the actual concentrations within the living organism tissues should be tested in order to produce relevant risk assessments for brooding-coral species.

LITERATURE REVIEW OF CORAL REEF RESTORATION IN AND AROUND THE CORAL TRIANGLE FROM THE VIEWPOINT OF MARINE BIODIVERSITY

The coral reefs of the Coral Triangle and nearby marine regions are the most biodiverse marine ecosystems in the world, providing ecosystem services to hundreds of millions of people. However, like coral reefs in other regions, these ecosystems are in decline due to a myriad of anthropogenically-induced stressors. To mitigate this decline, active coral reef restoration efforts have been increasing worldwide, including in this region. An important end-goal of coral reef restoration is the conservation of functional biodiversity of not only zooxanthellate scleractinian corals, but of all associated coral reef organisms. In this literature review, we collected papers from the Web of Science (1995-2021) focused specifically on coral reef restoration from six countries and regions around the Coral Triangle (Japan, Taiwan, mainland China, Philippines, Malaysia, Indonesia) to examine how much coral reef restoration research has been performed in each area, when it was performed, what methodologies were used, what organisms were targeted, and whether any assessment of biodiversity was included. Our results show great disparity in the research efforts of each area, with the Philippines clearly leading research in the region with almost half of the literature examined, followed by Japan and Indonesia, with nascent efforts in mainland China, Taiwan, and Malaysia. Overall, for the region, research appears to be increasing with time. Research in most areas was concentrated in one or two locations, and almost exclusively focused only on corals. Only approximately 38% of papers mentioned biodiversity in any manner, and only 14% included organisms other than scleractinian corals in their results. It is clear from this review that extensive research and data gaps exist regarding coral reef restoration in the western Pacific and Coral Triangle, particularly from the viewpoint of biodiversity. It is hoped that research can address these gaps before coral reef ecosystems in the region decline even further.
 
 Keywords: coral reef ecosystems, knowledge gaps, East Asia, South-East Asia, Indo-Pacific.

How moonlight shapes environments, life histories, and ecological interactions on coral reefs.

The lunar cycle drives variation in nocturnal brightness. For the epipelagic larvae of coral reef organisms, nocturnal illumination may have widespread and underappreciated consequences. At sea, the onset of darkness coincides with an influx of mesopelagic organisms to shallow water (i.e. 'diel vertical migrants') that include predators (e.g. lanternfishes) and prey (zooplankton) of zooplanktivorous coral reef larvae. Moonlight generally suppresses this influx, but lunar periodicity in the timing and intensity of nocturnal brightness may affect vertically migrating predators and prey differently. A major turnover of species occurs at sunset on the reef, with diurnal species seeking shelter and nocturnal species emerging to hunt. The hunting ability of nocturnal reef-based predators is aided by the light of the moon. Consequently, variation in nocturnal illumination is likely to shape the timing of reproduction, larval development, and settlement for many coral reef organisms. This synthesis underscores the potential importance of trophic linkages between coral reefs and adjacent pelagic ecosystems, facilitated by the diel migrations of mesopelagic organisms and the ontogenetic migrations of coral reef larvae. Research is needed to better understand the effects of lunar cycles on life-history strategies, and the potentially disruptive effects of light pollution, turbidity, and climate-driven changes to nocturnal cloud cover. These underappreciated threats may alter patterns of nocturnal illumination that have shaped the evolutionary history of many coral reef organisms, with consequences for larval survival and population replenishment that could rival or exceed other effects arising from climate change.

Light‐driven dynamics between calcification and production in functionally diverse coral reef calcifiers

AbstractCoral reef metabolism underpins ecosystem function and is defined by the processes of photosynthesis, respiration, calcification, and calcium carbonate dissolution. However, the relationships between these physiological processes at the organismal level and their interactions with light remain unclear. We examined metabolic rates across a range of photosynthesising calcifiers in the Caribbean: the scleractinian corals Acropora cervicornis, Orbicella faveolata, Porites astreoides, and Siderastrea siderea, and crustose coralline algae (CCA) under varying natural light conditions. Net photosynthesis and calcification showed a parabolic response to light across all species, with differences among massive corals, branching corals, and CCA that reflect their relative functional roles on the reef. At night, all organisms were net respiring, and most were net calcifying, although some incubations demonstrated instances of net calcium carbonate (CaCO3) dissolution. Peak metabolic rates at light‐saturation (maximum photosynthesis and calcification) and average dark rates (respiration and dark calcification) were positively correlated across species. Interspecies relationships among photosynthesis, respiration, and calcification indicate that calcification rates are linked to energy production at the organismal level in calcifying reef organisms. The species‐specific ratios of net calcification to photosynthesis varied with light over a diurnal cycle. The dynamic nature of calcification/photosynthesis ratios over a diurnal cycle questions the use of this metric as an indicator for reef function and health at the ecosystem scale unless temporal variability is accounted for, and a new metric is proposed. The complex light‐driven dynamics of metabolic processes in coral reef organisms indicate that a more comprehensive understanding of reef metabolism is needed for predicting the future impacts of global change.

Spatial and Short-Term Temporal Patterns of Octocoral Assemblages in the West Philippine Sea

Octocorals are relatively understudied than other coral reef organisms despite their ecological and economic values. The Philippines is known to have high marine biodiversity, but information on octocorals is lacking. This study investigated spatial and temporal variations in the assemblage of octocorals in selected reef sites in the West Philippine Sea (WPS)- the Kalayaan Island Group (i.e., Pag-asa, Sabina, Lawak, and Northeast Investigator) and Ulugan in 2017 and 2019. Results showed high octocoral taxonomic richness (at least 10 families) in the study sites. Mean percent octocoral cover in WPS was 5.35% SE ± 0.55, with Sabina having the highest octocoral cover in both years. Significant differences in octocoral cover were observed among sites in both years, but among-station differences were only observed in 2017. Octocoral assemblage also differed among sites in both years (ANOSIM:R> 0.5,p< 0.05), wherein different octocoral taxa dominated in different sites. In particular, variations were driven by high cover of holaxonians, nephtheids, and coelogorgiids in Sabina, and clavulariids, tubiporiids, and xeniids in Northeast Investigator in 2017. In 2019, significant variations were driven by high cover of helioporiids in Pag-asa, while Sabina had higher abundance of holaxonians, nephtheids, alcyoniids, and xeniids. Short-term temporal variation on octocoral cover in monitoring stations in Pag-asa was not observed (Kruskal-Wallis,p> 0.05), although the overall mean octocoral cover increased from 1.23% ± SE 0.47 in 2017 to 2.09% SE ± 0.37 in 2019. Further, there was no significant change in the octocoral assemblage in Pag-asa between years (ANOSIM,R= 0.11,p= 0.07). This study highlights high octocoral taxonomic richness in the WPS relative to other sites in the Indo-Pacific Region and provides baseline information on the octocoral assemblages, which can be useful for future ecological studies and marine biodiversity conservation efforts.

Accumulation of commonly used agricultural herbicides in coral reef organisms from iSimangaliso Wetland Park, South Africa

Coral reefs are amongst the most biodiverse ecosystems on earth, but are significantly impacted by agricultural runoff. Despite herbicides being commonly detected in coastal waters, the possibility of herbicide accumulation in coral reef species has largely been overlooked. We investigate the accumulation of several herbicides in five species of coral reef invertebrates collected from ten sites along the Maputaland coast, South Africa. Multiple herbicide residues were detected in 95% of the samples, with total average concentrations across sites ranging between 25.2 ng g−1 to 51.3 ng g−1 dw. Acetochlor, alachlor and hexazinone were the predominant herbicides detected at all sites, with atrazine and simazine detected less frequently. Significant interactive effects were detected between sites nested in reef complex crossed with species, based on multiple and total herbicide concentrations. In general, multivariate herbicide concentrations varied significantly between species within and across most sites. Contrastingly, the concentrations of the different herbicides and that of total herbicide did not differ between conspecifics at most sites nested in their respective reef complexes. On average, highest total herbicide concentrations were measured in soft coral (Sarcophyton glaucum; 90.4 ± 60 ng g−1 and Sinularia gravis; 42.7 ± 25 ng g−1) and sponge (Theonela swinhoei; 39.0 ± 40 ng g−1) species, while significantly lower concentrations were detected in hard corals (Echinopora hirsutissima; 10.5 ± 5.9 ng g−1 and Acropora austera; 5.20 ± 4.5 ng g−1) at most sites. Agricultural runoff entering the ocean via the uMfolozi-St Lucia Estuary and Maputo Bay are likely sources of herbicide contamination to coral reefs in the region. There is an urgent need to assess the long-term effects of herbicide exposure on coral reef communities.

Knowledge Gaps in the Biology, Ecology, and Management of the Pacific Crown-of-Thorns Sea Star Acanthaster sp. on Australia's Great Barrier Reef.

AbstractCrown-of-thorns sea stars (Acanthaster sp.) are among the most studied coral reef organisms, owing to their propensity to undergo major population irruptions, which contribute to significant coral loss and reef degradation throughout the Indo-Pacific. However, there are still important knowledge gaps pertaining to the biology, ecology, and management of Acanthaster sp. Renewed efforts to advance understanding and management of Pacific crown-of-thorns sea stars (Acanthaster sp.) on Australia's Great Barrier Reef require explicit consideration of relevant and tractable knowledge gaps. Drawing on established horizon scanning methodologies, this study identified contemporary knowledge gaps by asking active and/or established crown-of-thorns sea star researchers to pose critical research questions that they believe should be addressed to improve the understanding and management of crown-of-thorns sea stars on the Great Barrier Reef. A total of 38 participants proposed 246 independent research questions, organized into 7 themes: feeding ecology, demography, distribution and abundance, predation, settlement, management, and environmental change. Questions were further assigned to 48 specific topics nested within the 7 themes. During this process, redundant questions were removed, which reduced the total number of distinct research questions to 172. Research questions posed were mostly related to themes of demography (46 questions) and management (48 questions). The dominant topics, meanwhile, were the incidence of population irruptions (16 questions), feeding ecology of larval sea stars (15 questions), effects of elevated water temperature on crown-of-thorns sea stars (13 questions), and predation on juveniles (12 questions). While the breadth of questions suggests that there is considerable research needed to improve understanding and management of crown-of-thorns sea stars on the Great Barrier Reef, the predominance of certain themes and topics suggests a major focus for new research while also providing a roadmap to guide future research efforts.

Development of a multi-excitation fluorescence (MEF) imaging method to improve the information content of benthic coral reef surveys

Benthic surveys are a key component of monitoring and conservation efforts for coral reefs worldwide. While traditional image-based surveys rely on manual annotation of photographs to characterise benthic composition, automatic image annotation based on computer vision is becoming increasingly common. However, accurate classification of some benthic groups from reflectance images presents a challenge to local ecologists and computers alike. Most coral reef organisms produce one or a combination of fluorescent pigments, such as Green Fluorescent Protein (GFP)-like proteins found in corals, chlorophyll-a found in all photosynthetic organisms, and phycobiliproteins found in red macroalgae, crustose coralline algae (CCA) and cyanobacteria. Building on the potential of these pigments as a target for automatic image annotation, we developed a novel imaging method based on off-the-shelf components to improve classification of coral and other biotic substrates using a multi-excitation fluorescence (MEF) imaging system. We used RGB cameras to image the fluorescence emission of coral and algal pigments stimulated by narrow-waveband blue and green light, and then combined the information into three-channel pseudocolour images. Using a set of a priori rules defined by the relative pixel intensity produced in different channels, the method achieved successful classification of organisms into three categories based on the dominant fluorescent pigment expressed, facilitating discrimination of traditionally problematic groups. This work provides a conceptual foundation for future technological developments that will improve the cost, accuracy and speed of coral reef surveys.

Growth and feeding in the sponge Agelas tubulata from shallow to mesophotic depths on Grand Cayman Island

AbstractOn Caribbean coral reefs, sponges are important members of the benthic community and play multiple roles in ecosystem structure and function. They have an important role in benthic‐pelagic coupling, consuming particulate organic matter (POM) and dissolved organic matter (DOM) and in turn providing food in the form of sponge biomass or the release of detritus for a variety of coral reef organisms. Throughout the Caribbean, sponges show consistent increases in their abundance and growth rates as depth increases into the mesophotic zone (30–150 m). This has been hypothesized to be driven by bottom‐up forces, particularly the increased supply of nitrogen‐rich POM in mesophotic coral reef ecosystems (MCEs). Here, we tested the hypothesis that the sponge, Agelas tubulata, exhibits increased growth rates on MCEs relative to shallow reefs on Grand Cayman Island and that this is driven by bottom‐up forcing. We observed increased growth rates in mesophotic A. tubulata, compared with shallow conspecifics, despite variability in feeding on both POM and DOM. Mesophotic sponges, however, were consistently exposed to greater amounts of POM, which was seasonally variable unlike DOM. Changes in stable isotopic signatures, and higher feeding rates with increasing depth, were consistent with increasing rates of growth in sponges as depth increases. These observations support the hypothesis that mesophotic sponges have higher growth rates due to increased POM availability and consumption over time. The results of this study illustrate the crucial role that bottom‐up forcing has in the structuring of sponge communities on both shallow and mesophotic Caribbean coral reefs and the importance of POM as a source of nitrogen in sponge diets.

Nutrient pollution alters the gut microbiome of a territorial reef fish

Human-induced nutrient pollution threatens coral reefs worldwide. Although eutrophication disrupts coral microbiomes, often leading to coral mortality, it is unknown whether eutrophication impacts the microbiomes of other coral reef organisms. Of particular interest are herbivorous fishes, whose algae consumption is critical in maintaining healthy corals. To examine the effects of eutrophication on fish gut microbiomes, we experimentally enriched territories of Stegastes nigricans, a predominantly herbivorous damselfish that farms turf algae. Using 16S RNA sequencing, we demonstrate that hindgut and foregut microbiomes have significantly higher alpha diversity in nutrient-enriched territories as compared to unenriched controls. S. nigricans gut microbiomes also exhibited significantly different compositions across treatments. In contrast, these changes were not observed in the microbiomes of the turf algae consumed by S. nigricans, indicating that the gut microbiome changes were autochthonous. Combined, our results provide a novel example of endogenous microbial shifts in wild vertebrates caused by simulated anthropogenic stress.

Comparison of 15 dinoflagellate genomes reveals extensive sequence and structural divergence in family Symbiodiniaceae and genus Symbiodinium

BackgroundDinoflagellates in the family Symbiodiniaceae are important photosynthetic symbionts in cnidarians (such as corals) and other coral reef organisms. Breakdown of the coral-dinoflagellate symbiosis due to environmental stress (i.e. coral bleaching) can lead to coral death and the potential collapse of reef ecosystems. However, evolution of Symbiodiniaceae genomes, and its implications for the coral, is little understood. Genome sequences of Symbiodiniaceae remain scarce due in part to their large genome sizes (1–5 Gbp) and idiosyncratic genome features.ResultsHere, we present de novo genome assemblies of seven members of the genus Symbiodinium, of which two are free-living, one is an opportunistic symbiont, and the remainder are mutualistic symbionts. Integrating other available data, we compare 15 dinoflagellate genomes revealing high sequence and structural divergence. Divergence among some Symbiodinium isolates is comparable to that among distinct genera of Symbiodiniaceae. We also recovered hundreds of gene families specific to each lineage, many of which encode unknown functions. An in-depth comparison between the genomes of the symbiotic Symbiodinium tridacnidorum (isolated from a coral) and the free-living Symbiodinium natans reveals a greater prevalence of transposable elements, genetic duplication, structural rearrangements, and pseudogenisation in the symbiotic species.ConclusionsOur results underscore the potential impact of lifestyle on lineage-specific gene-function innovation, genome divergence, and the diversification of Symbiodinium and Symbiodiniaceae. The divergent features we report, and their putative causes, may also apply to other microbial eukaryotes that have undergone symbiotic phases in their evolutionary history.

Quiet oceans: United States Virgin Islands coral reef soundscapes in the age of coronavirus

The COVID-19 pandemic has led to unprecedented changes in human behavior around the world. These changes have impacted local soundscapes in both terrestrial and marine environments resulting in a global ‘quieting’ event that has allowed for the opportunity to evaluate the activity of soniferous organisms in unique acoustic environments. Across the world’s oceans, patterns of commercial, research, and recreational vessel traffic have all been altered, with corresponding alterations in the anthropogenic contribution to underwater noise. To assess these changes we used long-term acoustic recorders at three different coral reef sites on the Southern coast of the island of St. John in the United States Virgin Islands (USVI). We compared conditions pre-coronavirus outbreak (2019) and post-outbreak (2020) and found a decrease in the incidence of boat noise over the course of the pandemic. Because anthropogenic noise tends to overlap with the low frequencies used by marine fishes and invertebrates for sound production and detection, we predicted that changes in boat noise patterns would lead to concurrent changes in biological sound production of coral reef organisms. Understanding the impacts of this “quiet time” on marine organismal activity in the USVI could play a role in worldwide coral reef acoustic studies and conservation efforts.

Interannual variability and decadal stability of benthic organisms on an Indonesian coral reef

AbstractThe availability of colonizable substrate is an important driver of the temporal dynamics of sessile invertebrates on coral reefs. Increased dominance of algae and, in some cases, sponges has been documented on many coral reefs around the world, but how these organisms benefit from non-colonized substrate on the reef is unclear. In this study, we described the temporal dynamics of benthic organisms on an Indonesian coral reef across two time periods between 2006 and 2017 (2006–2008 and 2014–2017), and investigated the effects of colonizable substrate on benthic cover of coral reef organisms at subsequent sampling events. In contrast with other Indonesian reefs where corals have been declining, corals were dominant and stable over time at this location (mean ± SE percentage cover 42.7 ± 1.9%). Percentage cover of turf algae and sponges showed larger interannual variability than corals and crustose coralline algae (CCA) (P < 0.001), indicating that these groups are more dynamic over short temporal scales. Bare substrate was a good predictor of turf cover in the following year (mean effect 0.2, 95% CI: 0–0.4). Algal cover combined with bare space was a good predictor of CCA cover the following year generally, and of sponge cover the following year but only at one of the three sites. These results indicate that turf algae on some Indonesian reefs can rapidly occupy free space when this becomes available, and that other benthic groups are probably not limited by the availability of bare substrate, but may overgrow already fouled substrates.

Response of Coral Reef Dinoflagellates to Nanoplastics under Experimental Conditions Suggests Downregulation of Cellular Metabolism.

Plastic products contribute heavily to anthropogenic pollution of the oceans. Small plastic particles in the microscale and nanoscale ranges have been found in all marine ecosystems, but little is known about their effects upon marine organisms. In this study, we examine changes in cell growth, aggregation, and gene expression of two symbiotic dinoflagellates of the family Symbiodiniaceae, Symbiodinium tridacnidorum (clade A3), and Cladocopium sp. (clade C) under exposure to 42-nm polystyrene beads. In laboratory experiments, the cell number and aggregation were reduced after 10 days of nanoplastic exposure at 0.01, 0.1, and 10 mg/L concentrations, but no clear correlation with plastic concentration was observed. Genes involved in dynein motor function were upregulated when compared to control conditions, while genes related to photosynthesis, mitosis, and intracellular degradation were downregulated. Overall, nanoplastic exposure led to more genes being downregulated than upregulated and the number of genes with altered expression was larger in Cladocopium sp. than in S. tridacnidorum, suggesting different sensitivity to nano-plastics between species. Our data show that nano-plastic inhibits growth and alters aggregation properties of microalgae, which may negatively affect the uptake of these indispensable symbionts by coral reef organisms.

High light alongside elevated PCO2 alleviates thermal depression of photosynthesis in a hard coral (Pocillopora acuta).

The absorbtion of human-emitted CO2 by the oceans (elevated PCO2 ) is projected to alter the physiological performance of coral reef organisms by perturbing seawater chemistry (i.e. ocean acidification). Simultaneously, greenhouse gas emissions are driving ocean warming and changes in irradiance (through turbidity and cloud cover), which have the potential to influence the effects of ocean acidification on coral reefs. Here, we explored whether physiological impacts of elevated PCO2 on a coral-algal symbiosis (Pocillopora acuta-Symbiodiniaceae) are mediated by light and/or temperature levels. In a 39 day experiment, elevated PCO2 (962 versus 431 µatm PCO2 ) had an interactive effect with midday light availability (400 versus 800 µmolphotonsm-2s-1) and temperature (25 versus 29°C) on areal gross and net photosynthesis, for which a decline at 29°C was ameliorated under simultaneous high-PCO2 and high-light conditions. Light-enhanced dark respiration increased under elevated PCO2 and/or elevated temperature. Symbiont to host cell ratio and chlorophyll a per symbiont increased at elevated temperature, whilst symbiont areal density decreased. The ability of moderately strong light in the presence of elevated PCO2 to alleviate the temperature-induced decrease in photosynthesis suggests that higher substrate availability facilitates a greater ability for photochemical quenching, partially offsetting the impacts of high temperature on the photosynthetic apparatus. Future environmental changes that result in moderate increases in light levels could therefore assist the P. acuta holobiont to cope with the 'one-two punch' of rising temperatures in the presence of an acidifying ocean.

Dynamic Satellite Seascapes as a Biogeographic Framework for Understanding Phytoplankton Assemblages in the Florida Keys National Marine Sanctuary, United States

Physical, chemical, geological, and biological factors interact in marine environments to shape complex but recurrent patterns of organization of life on multiple spatial and temporal scales. These factors define biogeographic regions in surface waters that we refer to as seascapes. We characterize seascapes for the Florida Keys National Marine Sanctuary (FKNMS) and southwest Florida shelf nearshore environment using multivariate satellite and in situ measurements of Essential Ocean Variables (EOVs) and Essential Biodiversity Variables (EBVs). The study focuses on three periods that cover separate oceanographic expeditions (March 11-18, May 9-13, and September 12-19, 2016). We collected observations on bio-optical parameters (particulate and dissolved spectral absorption coefficients), phytoplankton community composition, and hydrography from a ship. Phytoplankton community composition was evaluated using 1) chemotaxonomic analysis (CHEMTAX) based on high-performance liquid chromatography (HPLC) pigment measurements, and 2) analysis of spectral phytoplankton absorption coefficients (aphy). Dynamic seascapes were derived by combining satellite time series of sea surface temperature, chlorophyll-a concentration, and normalized fluorescent line height (nFLH) using a supervised thematic classification. The seascapes identified areas of different salinity and nutrient concentrations where different phytoplankton communities were present as determined by hierarchical cluster analyses of HPLC pigments and aphy spectra. Oligotrophic, Mesotrophic and Transition seascape classes of deeper offshore waters were dominated by small phytoplankton ( 60 %). Spectral analysis of aphy indicated higher absorption levels at 492 and 550 nm wavelengths in seascapes carrying predominantly small phytoplankton than in classes dominated by larger taxa. Seascapes carrying large phytoplankton showed absorption peaks at the 673 nm wavelength. The seascape framework promises to be a tool to detect different biogeographic domains quickly, providing information about the changing environmental conditions experienced by coral reef organisms including coral, sponges, fish and higher trophic levels. The effort illustrates best practices developed under the Marine Biodiversity Observation Network (MBON) demonstration project, in collaboration with the South Florida Ecosystem Restoration Research (SFER) project managed by the Atlantic Oceanographic and Meteorological Laboratory of NOAA (AOML-NOAA).

First Study on Marine Heterobranchia (Gastropoda, Mollusca) in Bangka Archipelago, North Sulawesi, Indonesia

As ephemeral, benthic, secondary consumers usually associated with sessile coral reef organisms, marine heterobranchs are good indicators of the health of marine tropical habitats. Thus, marine Heterobranchia have recently become a major target for monitoring programs. For this work, an extensive survey was made in Bangka Archipelago, the first of its kind in this area. Bangka Archipelago is composed of small islands and the adjacent coastline of North Sulawesi. The substrate is dominated by biogenic reefs and volcanic rocks, thus forming highly diverse habitats. In total, 149 species were collected and/or photo-documented in September 2017 and September 2018, which represents the dry season. They can be assigned to the Cephalaspidea, Aplysiida, Pleurobranchida, Nudibranchia, and Eupulmonata. Thirty-three species are new to science, highlighting the lack of knowledge about the group and especially about this region. Our data provide a baseline for future monitoring surveys, as the anthropogenic pressures on Bangka Archipelago are increasing due to enhanced touristic activities, but also due to large scale environmental changes caused by previous mining operation activities.