Precision and accuracy of common coral reef sampling protocols revisited with photogrammetry.

The rapid decline of coral reefs calls for cost-effective benthic cover data to improve reef health forecasts, policy building, management responses and evaluation. Reef monitoring has been largely based on divers' observations along transects, and secondarily on quadrat-based protocols, video and photographic records. However, the accuracy and precision of the most common sampling approaches are not yet fully understood. Here, we compared benthic cover estimates from three common sampling protocols: Reef Check (RC), Atlantic and Gulf Rapid Reef Assessment (AGRRA) and photoquadrats (PQ). The reef cover of two contrasting sites was reconstructed with ∼450 m2 orthomosaics built with high resolution Structure-from-Motion (SfM) photogrammetry, which were used as references for comparisons among protocols. In addition, we explored sample size requirements for each protocol and provided cost-effectiveness comparisons. Our results evidenced between-reef differences in the accuracy and precision of estimates with the different protocols. The three protocols performed similarly in the reef with low macroalgal cover (<0.5%), but PQ were more accurate and precise in the reef with relatively high (∼20%) macroalgal cover. The sample size for estimating coral cover with a 20% error margin and a 0.05 significance level was lower for PQ, followed by AGRRA and RC. Considering performance, cost surrogates and equipment needs, cost-effectiveness was higher for PQ. We also discuss costs, limitations and advantages/disadvantages of SfM photogrammetry as a sampling approach for coral reef monitoring.

Incised valleys drive distinctive oceanographic processes and biological assemblages within rhodolith beds.

Continental shelves encompass gently sloped seascapes that are highly productive and intensively exploited for natural resources. Islands, reefs and other emergent or quasi-emergent features punctuate these shallow (<100 m) seascapes and are well known drivers of increased biomass and biodiversity, as well as predictors of fishing and other human uses. On the other hand, relict mesoscale geomorphological features that do not represent navigation hazards, such as incised valleys (IVs), remain poorly charted. Consequently, their role in biophysical processes remains poorly assessed and sampled. Incised valleys are common within rhodolith beds (RBs), the most extensive benthic habitat along the tropical and subtropical portions of the mid and outer Brazilian shelf. Here, we report on a multi-proxy assessment carried out in a tropical-subtropical transition region (~20°S) off Eastern Brazil, contrasting physicochemical and biological variables in IVs and adjacent RBs. Valleys interfere in near bottom circulation and function as conduits for water and propagules from the slope up to the mid shelf. In addition, they provide a stable and structurally complex habitat for black corals and gorgonians that usually occur in deeper water, contrasting sharply with the algae-dominated RB. Fish richness, abundance and biomass were also higher in the IVs, with small planktivores and large-bodied, commercially important species (e.g. groupers, snappers and grunts) presenting smaller abundances or being absent from RBs. Overall, IVs are unique and vulnerable habitats that sustain diverse assemblages and important ecosystem processes. As new IVs are detected by remote sensing or bathymetric surveys, they can be incorporated into regional marine management plans as conservation targets and priority sites for detailed in situ surveys.

Coral growth bands recorded trace elements associated with the Fundão dam collapse.

In November 2015, the collapse of the Fundão dam (Minas Gerais, Brazil) carried over 40 × 106 m3 of iron ore tailings into the Doce river and caused massive environmental and socioeconomic impacts across the watershed. The downstream mudslide scavenged contaminants deposited in the riverbed, and several potentially toxic elements were further released through reduction and solubilization of Fe oxy-hydroxides under estuarine conditions. A turbidity plume was formed off the river mouth, but the detection of contaminants' dispersion in the ocean remains poorly assessed. This situation is specially concerning because Southwestern Atlantic's largest and richest reefs are located 70-250 km to the north of the Doce river mouth, and the legal dispute over the extent of monitoring, compensation and restoration measures are based either on indirect evidence from modeling or on direct evidence from remote sensing and contaminated organisms. Coral skeletons can incorporate trace elements and are considered good monitors of marine pollution, including inputs from open cut mining. Here, we studied a Montastraea cavernosa (Linnaeus 1767) coral colony collected 220 km northward to the river mouth, using X-rays for assessing growth bands and Laser Ablation Inductively Coupled Plasma Mass Spectrometry to recover trace elements incorporated in growth bands formed between 2014 and 2018. A threefold positive Fe anomaly was identified in early 2016, associated with negative anomalies in several elements. Variation in Ba and Y was coherent with the region's sedimentation dynamics, but also increased after 2016, akin to Pb, V and Zn. Coral growth rates decreased after the disaster. Besides validating M. cavernosa as a reliable archive of ocean chemistry, our results evidence wide-reaching sub-lethal coral contamination in the Abrolhos reefs, as well as different incorporation mechanisms into corals' skeletons.

Decadal (2006-2018) dynamics of Southwestern Atlantic's largest turbid zone reefs.

Tropical reefs are declining rapidly due to climate changes and local stressors such as water quality deterioration and overfishing. The so-called marginal reefs sustain significant coral cover and growth but are dominated by fewer species adapted to suboptimal conditions to most coral species. However, the dynamics of marginal systems may diverge from that of the archetypical oligotrophic tropical reefs, and it is unclear whether they are more or less susceptible to anthropogenic stress. Here, we present the largest (100 fixed quadrats at five reefs) and longest time series (13 years) of benthic cover data for Southwestern Atlantic turbid zone reefs, covering sites under contrasting anthropogenic and oceanographic forcing. Specifically, we addressed how benthic cover changed among habitats and sites, and possible dominance-shift trends. We found less temporal variation in offshore pinnacles' tops than on nearshore ones and, conversely, higher temporal fluctuation on offshore pinnacles' walls than on nearshore ones. In general, the Abrolhos reefs sustained a stable coral cover and we did not record regional-level dominance shifts favoring other organisms. However, coral decline was evidenced in one reef near a dredging disposal site. Relative abundances of longer-lived reef builders showed a high level of synchrony, which indicates that their dynamics fluctuate under similar drivers. Therefore, changes on those drivers could threaten the stability of these reefs. With the intensification of thermal anomalies and land-based stressors, it is unclear whether the Abrolhos reefs will keep providing key ecosystem services. It is paramount to restrain local stressors that contributed to coral reef deterioration in the last decades, once reversal and restoration tend to become increasingly difficult as coral reefs degrade further and climate changes escalate.

Tropical rhodolith beds are a major and belittled reef fish habitat.

Understanding habitat-level variation in community structure provides an informed basis for natural resources' management. Reef fishes are a major component of tropical marine biodiversity, but their abundance and distribution are poorly assessed beyond conventional SCUBA diving depths. Based on a baited-video survey of fish assemblages in Southwestern Atlantic's most biodiverse region we show that species composition responded mainly to the two major hard-bottom megahabitats (reefs and rhodolith beds) and to the amount of light reaching the bottom. Both megahabitats encompassed typical reef fish assemblages but, unexpectedly, richness in rhodolith beds and reefs was equivalent. The dissimilar fish biomass and trophic structure in reefs and rhodolith beds indicates that these systems function based on contrasting energy pathways, such as the much lower herbivory recorded in the latter. Rhodolith beds, the dominant benthic megahabitat in the tropical Southwestern Atlantic shelf, play an underrated role as fish habitats, and it is critical that they are considered in conservation planning.

Ecogenomics of the Marine Benthic Filamentous Cyanobacterium Adonisia.

Turfs are among the major benthic components of reef systems worldwide. The nearly complete genome sequences, basic physiological characteristics, and phylogenomic reconstruction of two phycobiliprotein-rich filamentous cyanobacteria strains isolated from turf assemblages from the Abrolhos Bank (Brazil) are investigated. Both Adonisia turfae CCMR0081T (= CBAS 745T) and CCMR0082 contain approximately 8 Mbp in genome size and experiments identified that both strains exhibit chromatic acclimation. Whereas CCMR0081T exhibits chromatic acclimation type 3 (CA3) regulating both phycocyanin (PC) and phycoerythrin (PE), CCMR0082 strain exhibits chromatic acclimation type 2 (CA2), in correspondence with genes encoding specific photosensors and regulators for PC and PE. Furthermore, a high number and diversity of secondary metabolite synthesis gene clusters were identified in both genomes, and they were able to grow at high temperatures (28 °C, with scant growth at 30 °C). These characteristics provide insights into their widespread distribution in reef systems.

Acidification-induced cellular changes in Symbiodinium isolated from Mussismilia braziliensis.

Dinoflagellates from the Symbiodiniaceae family and corals have an ecologically important endosymbiotic relationship. Scleractinian corals cannot survive for long periods without their symbionts. These algae, also known as zooxanthellae, on the other hand, thrives outside the coral cells. The free-living populations of zooxanthellae are essential for the resilience of the coral to environmental stressors such as temperature anomalies and ocean acidification. Yet, little is known about how ocean acidification may affect the free-living zooxanthellae. In this study we aimed to test morphological, physiological and biochemical responses of zooxanthellae from the Symbiodinium genus isolated from the coral Mussismilia braziliensis, endemic to the Brazilian coast, to acidification led by increased atmospheric CO2. We tested whether photosynthetic yield, cell ultrastructure, cell density and lipid profile would change after up to 16 days of exposure to pH 7.5 in an atmospheric pCO2 of 1633 µatm. Photosynthetic yield and cell density were negatively affected and chloroplasts showed vesiculated thylakoids, indicating morphological damage. Moreover, Symbiodinium fatty acid profile drastically changed in acidified condition, showing lower polyunsaturated fatty acids and higher saturated fatty acids contents, when compared to the control, non-acidified condition. These results show that seawater acidification as an only stressor causes significant changes in the physiology, biochemistry and ultrastructure of free-living Symbiodinium.

Metagenomics of Coral Reefs Under Phase Shift and High Hydrodynamics.

Local and global stressors have affected coral reef ecosystems worldwide. Switches from coral to algal dominance states and microbialization are the major processes underlying the global decline of coral reefs. However, most of the knowledge concerning microbialization has not considered physical disturbances (e.g., typhoons, waves, and currents). Southern Japan reef systems have developed under extreme physical disturbances. Here, we present analyses of a three-year investigation on the coral reefs of Ishigaki Island that comprised benthic and fish surveys, water quality analyses, metagenomics and microbial abundance data. At the four studied sites, inorganic nutrient concentrations were high and exceeded eutrophication thresholds. The dissolved organic carbon (DOC) concentration (up to 233.3 µM) and microbial abundance (up to 2.5 × 105 cell/mL) values were relatively high. The highest vibrio counts coincided with the highest turf cover (∼55-85%) and the lowest coral cover (∼4.4-10.2%) and fish biomass (0.06 individuals/m2). Microbiome compositions were similar among all sites and were dominated by heterotrophs. Our data suggest that a synergic effect among several regional stressors are driving coral decline. In a high hydrodynamics reef environment, high algal/turf cover, stimulated by eutrophication and low fish abundance due to overfishing, promote microbialization. Together with crown-of-thorns starfish (COTS) outbreaks and possible of climate changes impacts, theses coral reefs are likely to collapse.

Long-term effects of competition and environmental drivers on the growth of the endangered coral Mussismilia braziliensis (Verril, 1867).

Most coral reefs have recently experienced acute changes in benthic community structure, generally involving dominance shifts from slow-growing hard corals to fast-growing benthic invertebrates and fleshy photosynthesizers. Besides overfishing, increased nutrification and sedimentation are important drivers of this process, which is well documented at landscape scales in the Caribbean and in the Indo-Pacific. However, small-scale processes that occur at the level of individual organisms remain poorly explored. In addition, the generality of coral reef decline models still needs to be verified on the vast realm of turbid-zone reefs. Here, we documented the outcome of interactions between an endangered Brazilian-endemic coral (Mussismilia braziliensis) and its most abundant contacting organisms (turf, cyanobacteria, corals, crustose coralline algae and foliose macroalgae). Our study was based on a long (2006-2016) series of high resolution data (fixed photoquadrats) acquired along a cross-shelf gradient that includes coastal unprotected reefs and offshore protected sites. The study region (Abrolhos Bank) comprises the largest and richest coralline complex in the South Atlantic, and a foremost example of a turbid-zone reef system with low diversity and expressive coral cover. Coral growth was significantly different between reefs. Coral-algae contacts predominated inshore, while cyanobacteria and turf contacts dominated offshore. An overall trend in positive coral growth was detected from 2009 onward in the inshore reef, whereas retraction in live coral tissue was observed offshore during this period. Turbidity (+) and cyanobacteria (-) were the best predictors of coral growth. Complimentary incubation experiments, in which treatments of Symbiodinium spp. from M. braziliensis colonies were subjected to cyanobacterial exudates, showed a negative effect of the exudate on the symbionts, demonstrating that cyanobacteria play an important role in coral tissue necrosis. Negative effects of cyanobacteria on living coral tissue may remain undetected from percent cover estimates gathered at larger spatial scales, as these ephemeral organisms tend to be rapidly replaced by longer-living macroalgae, or complex turf-like consortia. The cross-shelf trend of decreasing turbidity and macroalgae abundance suggests either a direct positive effect of turbidity on coral growth, or an indirect effect related to the higher inshore cover of foliose macroalgae, constraining cyanobacterial abundance. It is unclear whether the higher inshore macroalgal abundance (10-20% of reef cover) is a stable phase related to a long-standing high turbidity background, or a contemporary response to anthropogenic stress. Our results challenge the idea that high macroalgal cover is always associated with compromised coral health, as the baselines for turbid zone reefs may derive sharply from those of coral-dominated reefs that dwell under oligotrophic conditions.

Taxonomic and Functional Metagenomic Signature of Turfs in the Abrolhos Reef System (Brazil).

Turfs are widespread assemblages (consisting of microbes and algae) that inhabit reef systems. They are the most abundant benthic component in the Abrolhos reef system (Brazil), representing greater than half the coverage of the entire benthic community. Their presence is associated with a reduction in three-dimensional coral reef complexity and decreases the habitats available for reef biodiversity. Despite their importance, the taxonomic and functional diversity of turfs remain unclear. We performed a metagenomics and pigments profile characterization of turfs from the Abrolhos reefs. Turf microbiome primarily encompassed Proteobacteria (mean 40.57% ± s.d. 10.36, N = 1.548,192), Cyanobacteria (mean 35.04% ± s.d. 15.5, N = 1.337,196), and Bacteroidetes (mean 11.12% ± s.d. 4.25, N = 424,185). Oxygenic and anoxygenic phototrophs, chemolithotrophs, and aerobic anoxygenic phototrophic (AANP) bacteria showed a conserved functional trait of the turf microbiomes. Genes associated with oxygenic photosynthesis, AANP, sulfur cycle (S oxidation, and DMSP consumption), and nitrogen metabolism (N2 fixation, ammonia assimilation, dissimilatory nitrate and nitrite ammonification) were found in the turf microbiomes. Principal component analyses of the most abundant taxa and functions showed that turf microbiomes differ from the other major Abrolhos benthic microbiomes (i.e., corals and rhodoliths) and seawater. Taken together, these features suggest that turfs have a homogeneous functional core across the Abrolhos Bank, which holds diverse microbial guilds when comparing with other benthic organisms.

An extensive reef system at the Amazon River mouth.

Large rivers create major gaps in reef distribution along tropical shelves. The Amazon River represents 20% of the global riverine discharge to the ocean, generating up to a 1.3 × 10(6)-km(2) plume, and extensive muddy bottoms in the equatorial margin of South America. As a result, a wide area of the tropical North Atlantic is heavily affected in terms of salinity, pH, light penetration, and sedimentation. Such unfavorable conditions were thought to imprint a major gap in Western Atlantic reefs. We present an extensive carbonate system off the Amazon mouth, underneath the river plume. Significant carbonate sedimentation occurred during lowstand sea level, and still occurs in the outer shelf, resulting in complex hard-bottom topography. A permanent near-bottom wedge of ocean water, together with the seasonal nature of the plume's eastward retroflection, conditions the existence of this extensive (~9500 km(2)) hard-bottom mosaic. The Amazon reefs transition from accretive to erosional structures and encompass extensive rhodolith beds. Carbonate structures function as a connectivity corridor for wide depth-ranging reef-associated species, being heavily colonized by large sponges and other structure-forming filter feeders that dwell under low light and high levels of particulates. The oxycline between the plume and subplume is associated with chemoautotrophic and anaerobic microbial metabolisms. The system described here provides several insights about the responses of tropical reefs to suboptimal and marginal reef-building conditions, which are accelerating worldwide due to global changes.

Use of a marine microbial community as inoculum for biomethane production.

Marine substrates are prominent candidates for the production of biofuels, especially for biogas, which is a well-established technology that accepts different types of substrates for its production. However, the use of marine substrates in bioreactors may cause inhibition of methanogenic bacteria due to the addition of seasalts. Here, we explore a simple and economically viable way to circumvent the problem of inoculum inhibition. Based on the current knowledge of the diversity of microorganisms in marine sediments, we tested the direct use of methanogenic bacteria from an anoxic marine environment as inoculum for biomethane production. Both marine and freshwater substrates were added to this inoculum. No pretreatment (that may have enhanced methane production, but would have made the process more expensive) was applied either to the inoculum or to the substrates. For comparison, the same substrates were added to a standard inoculum (cow manure). Both the marine inoculum and cow manure produced methane by anaerobic digestion of the substrates added. The highest methane production (0.299 m(3) kg VS(-1)) was obtained by adding marine microalgae biomass (Chlorella sp. and Synechococcus sp.) to the marine inoculum. No inhibitory effects were observed due to differences in salinity between the inocula and substrates. Our results indicate the potential of using both marine inoculum and substrates for methane production.

Environmental and Sanitary Conditions of Guanabara Bay, Rio de Janeiro.

Guanabara Bay is the second largest bay in the coast of Brazil, with an area of 384 km(2). In its surroundings live circa 16 million inhabitants, out of which 6 million live in Rio de Janeiro city, one of the largest cities of the country, and the host of the 2016 Olympic Games. Anthropogenic interference in Guanabara Bay area started early in the XVI century, but environmental impacts escalated from 1930, when this region underwent an industrialization process. Herein we present an overview of the current environmental and sanitary conditions of Guanabara Bay, a consequence of all these decades of impacts. We will focus on microbial communities, how they may affect higher trophic levels of the aquatic community and also human health. The anthropogenic impacts in the bay are flagged by heavy eutrophication and by the emergence of pathogenic microorganisms that are either carried by domestic and/or hospital waste (e.g., virus, KPC-producing bacteria, and fecal coliforms), or that proliferate in such conditions (e.g., vibrios). Antibiotic resistance genes are commonly found in metagenomes of Guanabara Bay planktonic microorganisms. Furthermore, eutrophication results in recurrent algal blooms, with signs of a shift toward flagellated, mixotrophic groups, including several potentially harmful species. A recent large-scale fish kill episode, and a long trend decrease in fish stocks also reflects the bay's degraded water quality. Although pollution of Guanabara Bay is not a recent problem, the hosting of the 2016 Olympic Games propelled the government to launch a series of plans to restore the bay's water quality. If all plans are fully implemented, the restoration of Guanabara Bay and its shores may be one of the best legacies of the Olympic Games in Rio de Janeiro.

BaMBa: towards the integrated management of Brazilian marine environmental data.

A new open access database, Brazilian Marine Biodiversity (BaMBa) (https://marinebiodiversity.lncc.br), was developed in order to maintain large datasets from the Brazilian marine environment. Essentially, any environmental information can be added to BaMBa. Certified datasets obtained from integrated holistic studies, comprising physical-chemical parameters, -omics, microbiology, benthic and fish surveys can be deposited in the new database, enabling scientific, industrial and governmental policies and actions to be undertaken on marine resources. There is a significant number of databases, however BaMBa is the only integrated database resource both supported by a government initiative and exclusive for marine data. BaMBa is linked to the Information System on Brazilian Biodiversity (SiBBr, http://www.sibbr.gov.br/) and will offer opportunities for improved governance of marine resources and scientists' integration. Database URL: http://marinebiodiversity.lncc.br.

Microbial and sponge loops modify fish production in phase-shifting coral reefs.

Shifts from coral to algae dominance of corals reefs have been correlated to fish biomass loss and increased microbial metabolism. Here we investigated reef benthic and planktonic primary production, benthic dissolved organic carbon (DOC) release and bacterial growth efficiency in the Abrolhos Bank, South Atlantic. Benthic DOC release rates are higher while water column bacterial growth efficiency is lower at impacted reefs. A trophic model based on the benthic and planktonic primary production was able to predict the observed relative fish biomass in healthy reefs. In contrast, in impacted reefs, the observed omnivorous fish biomass is higher, while that of the herbivorous/coralivorous fish is lower than predicted by the primary production-based model. Incorporating recycling of benthic-derived carbon in the model through microbial and sponge loops explains the difference and predicts the relative fish biomass in both reef types. Increased benthic carbon release rates and bacterial carbon metabolism, but decreased bacterial growth efficiency could lead to carbon losses through respiration and account for the uncoupling of benthic and fish production in phase-shifting reefs. Carbon recycling by microbial and sponge loops seems to promote an increase of small-bodied fish productivity in phase-shifting coral reefs.

Multiple Symbiodinium Strains Are Hosted by the Brazilian Endemic Corals Mussismilia spp.

Corals of genus Mussismilia (Mussidae) are one of the oldest extant clades of scleractinians. These Neogene relicts are endemic to the Brazilian coast and represent the main reef-building corals in the Southwest Atlantic Ocean (SAO). The relatively low-diversity/high-endemism SAO coralline systems are under rapid decline from emerging diseases and other local and global stressors, but have not been severely affected by coral bleaching. Despite the biogeographic significance and importance for understanding coral resilience, there is scant information about the diversity of Symbiodinium in this ocean basin. In this study, we established the first culture collections of Symbiodinium from Mussismilia hosts, comprising 11 isolates, four of them obtained by fluorescent-activated cell sorting (FACS). We also analyzed Symbiodinium diversity directly from Mussismilia tissue samples (N = 16) and characterized taxonomically the cultures and tissue samples by sequencing the dominant ITS2 region. Symbiodinium strains A4, B19, and C3 were detected. Symbiodinium C3 was predominant in the larger SAO reef system (Abrolhos), while Symbiodinium B19 was found only in deep samples from the oceanic Trindade Island. Symbiodinium strains A4 and C3 isolates were recovered from the same Mussismilia braziliensis coral colony. In face of increasing threats, these results indicate that Symbiodinium community dynamics shall have an important contribution for the resilience of Mussismilia spp. corals.

Consequences of increased temperature and acidification on bacterioplankton community composition during a mesocosm spring bloom in the Baltic Sea.

Despite the paramount importance of bacteria for biogeochemical cycling of carbon and nutrients, little is known about the potential effects of climate change on these key organisms. The consequences of the projected climate change on bacterioplankton community dynamics were investigated in a Baltic Sea spring phytoplankton bloom mesocosm experiment by increasing temperature with 3°C and decreasing pH by approximately 0.4 units via CO2 addition in a factorial design. Temperature was the major driver of differences in community composition during the experiment, as shown by denaturing gradient gel electrophoresis (DGGE) of amplified 16S rRNA gene fragments. Several bacterial phylotypes belonging to Betaproteobacteria were predominant at 3°C but were replaced by members of the Bacteriodetes in the 6°C mesocosms. Acidification alone had a limited impact on phylogenetic composition, but when combined with increased temperature, resulted in the proliferation of specific microbial phylotypes. Our results suggest that although temperature is an important driver in structuring bacterioplankton composition, evaluation of the combined effects of temperature and acidification is necessary to fully understand consequences of climate change for marine bacterioplankton, their implications for future spring bloom dynamics, and their role in ecosystem functioning.

Effects from log-yard stormwater runoff on the microalgae Scenedesmus subspicatus: intra-storm magnitude and variability.

This paper describes the effects posed by stormwater runoff from an industrial log-yard on the microalgae Scenedesmus subspicatus. The effects of stormwater runoff sampled during two rain events were determined by exposing S. subspicatus cells to different concentrations (% v:v) of each sample. The effects were measured as the percentage change in growth rates in relation to a control culture after exposure times of 24, 48, 72 and 96 h. The runoff from the first rain event had no negative effects to S. subspicatus, posing in most cases growth stimulation, whereas the runoff from the second rain event inhibited algae growth. Differences in runoff physico-chemical characteristics combined with the hydrological factors of each rain event explained these opposite effects. The hypothesis of toxic first flush phenomenon was confirmed in the second rain event on the basis of normalized inhibitory effects and runoff volume. It was found that 42, 51 and 50% of the inhibitory effects during exposures of 24, 48 and 72 h were associated with the initial 4% of the total discharged volume. The fact that negative effects were observed in the two runoff events analyzed, raises concern about the potential environmental threats posed by runoff originated from wood-based industrial areas during the entire hydrological year.

Chloroplast DNA content in Dinophysis (Dinophyceae) from different cell cycle stages is consistent with kleptoplasty.

Kleptoplasty is the retention of plastids obtained from ingested algal prey, which can remain temporarily functional and be used for photosynthesis by the predator. With a new approach based on cell cycle analysis, we have addressed the question of whether the toxic, bloom-forming dinoflagellate Dinophysis norvegica practice kleptoplasty or if they replicate their own plastid DNA. Dividing (G2) and non-dividing (G1) D. norvegica cells from a natural population were physically separated with a flow cytometer based on their DNA content. Average numbers of nuclear and plastid rDNA copies were quantified with real-time PCR both in the G1 and G2 group. Cells from the G1 group contained 5800 +/- 340 copies of nuclear rDNA and 1300 +/- 200 copies of plastid rDNA; cells from the G2 group contained 9700 +/- 58 copies of nuclear rDNA and 1400 +/- 220 copies of plastid rDNA (mean +/- SD, n = 3). The ratio G2/G1 in average rDNA copies per cell was 1.67 for nuclear DNA and 1.07 for plastid DNA. These ratios show that plastid acquisition in D. norvegica is either uncoupled with the cell cycle, or plastids accumulate rapidly in the beginning of the cell cycle owing to feeding, as would be expected in a protist with kleptoplastic behaviour but not in a protist with own plastid replication. In addition, flow cytometry measurements on cells from the same population used for real-time PCR showed that when kept without plastidic prey, live Dinophysis cells lost on average 36% of their plastid phycoerythrin fluorescence in 24 h. Together these findings strongly suggest that D. norvegica does not possess the ability for plastid replication.

Ocean urea fertilization for carbon credits poses high ecological risks.

The proposed plan for enrichment of the Sulu Sea, Philippines, a region of rich marine biodiversity, with thousands of tonnes of urea in order to stimulate algal blooms and sequester carbon is flawed for multiple reasons. Urea is preferentially used as a nitrogen source by some cyanobacteria and dinoflagellates, many of which are neutrally or positively buoyant. Biological pumps to the deep sea are classically leaky, and the inefficient burial of new biomass makes the estimation of a net loss of carbon from the atmosphere questionable at best. The potential for growth of toxic dinoflagellates is also high, as many grow well on urea and some even increase their toxicity when grown on urea. Many toxic dinoflagellates form cysts which can settle to the sediment and germinate in subsequent years, forming new blooms even without further fertilization. If large-scale blooms do occur, it is likely that they will contribute to hypoxia in the bottom waters upon decomposition. Lastly, urea production requires fossil fuel usage, further limiting the potential for net carbon sequestration. The environmental and economic impacts are potentially great and need to be rigorously assessed.