Please visit the Red Sea Research Center Home Page for more information.

Recent Submissions

  • Adhesion to coral surface as a potential sink for marine microplastics.

    Martin, Cecilia; Corona, Elena; Mahadik, Gauri A; Duarte, Carlos M. (Environmental pollution (Barking, Essex : 1987), Elsevier BV, 2019-10-11) [Article]
    Only 1% of plastic entering the ocean is found floating on its surface, with high loads in ocean accumulation zones and semi-enclosed seas, except for the Red Sea, which supports one of the lowest floating plastic loads worldwide. Given the extension of reefs in the Red Sea, we hypothesize a major role of scleractinian corals as sinks, through suspension-feeding, and assessed microplastic removal rates by three Red Sea coral species. Experimental evidence showed removal rates ranging from 0.25 × 10-3 to 14.8 × 10-3 microplastic particles polyp-1 hour-1, among species. However, this was only 2.2 ± 0.6% of the total removal rate, with passive removal through adhesion to the coral surface being 40 times higher than active removal through suspension-feeding. These results point at adhesion of plastic to coral reef structures as a major sink for microplastics suspended in the water column after sinking, helping explain low concentrations in Red Sea surface waters.
  • Remotely sensing phytoplankton size structure in the Red Sea

    Gittings, John; Brewin, Robert J.W.; Raitsos, Dionysios E.; Kheireddine, Malika; Ouhssain, Mustapha; Jones, Burton; Hoteit, Ibrahim (Remote Sensing of Environment, Elsevier BV, 2019-10-09) [Article]
    Phytoplankton size structure impacts ocean food-web dynamics and biogeochemical cycling, and is thus an important ecological indicator that can be utilised to quantitatively evaluate the state of marine ecosystems. Potential alterations to size structure are predicted to occur in tropical regions under future scenarios of climate change. Therefore, there is an increasing requirement for the synoptic monitoring of phytoplankton size structure in marine systems. The Red Sea remains a comparatively unexplored tropical marine ecosystem, particularly with regards to its large-scale biological dynamics. Using an in situ pigment dataset acquired in the Red Sea, we parameterise a two-component, abundance-based phytoplankton size model and apply it to remotely-sensed observations of chlorophyll-a (Chl-a) concentration, to infer Chl-a in two size classes of phytoplankton, small cells <2 μm in size (picophytoplankton) and large cells >2 μm in size. Satellite-derived estimates of phytoplankton size structure are in good agreement with corresponding in situ measurements and also capture the spatial variability related to regional mesoscale dynamics. Our analysis reveals that, for the estimation of Chl-a in the two size classes, the model performs comparably or in some cases better, to validations in other oceanic regions. Our model parameterisation will be useful for future studies on the seasonal and interannual variability of phytoplankton size classes in the Red Sea, which may ultimately be relevant for understanding trophic linkages between phytoplankton size structure and fisheries, and the development of marine management strategies.
  • Can Fish and Cell Phones Teach Us about Our Health?

    Lee, Michael A; Duarte, Carlos M.; Eguíluz, V. M.; Heller, Daniel A; Langer, Robert; Meekan, Mark G; Sikes, Hadley D; Srivastava, Mani; Strano, Michael S; Wilson, Rory P (ACS sensors, American Chemical Society (ACS), 2019-10-03) [Article]
    Biologging is a scientific endeavor that studies the environment and animals within it by outfitting the latter with sensors of their dynamics as they roam freely in their natural habitats. As wearable technologies advance for the monitoring of human health, it may be instructive to reflect on the successes and failures of biologging in field biology over the past few decades. Several lessons may be of value. Physiological sensors can
  • Functional metagenomic analysis of dust-associated microbiomes above the Red Sea.

    Aalismail, Nojood; Ngugi, David K; Diaz Rua, Ruben; Alam, Intikhab; Cusack, Michael; Duarte, Carlos M. (Scientific reports, Springer Science and Business Media LLC, 2019-09-26) [Article]
    Atmospheric transport is a major vector for the long-range transport of microbial communities, maintaining connectivity among them and delivering functionally important microbes, such as pathogens. Though the taxonomic diversity of aeolian microorganisms is well characterized, the genomic functional traits underpinning their survival during atmospheric transport are poorly characterized. Here we use functional metagenomics of dust samples collected on the Global Dust Belt to initiate a Gene Catalogue of Aeolian Microbiome (GCAM) and explore microbial genetic traits enabling a successful aeolian lifestyle in Aeolian microbial communities. The GCAM reported here, derived from ten aeolian microbial metagenomes, includes a total of 2,370,956 non-redundant coding DNA sequences, corresponding to a yield of ~31 × 106 predicted genes per Tera base-pair of DNA sequenced for the aeolian samples sequenced. Two-thirds of the cataloged genes were assigned to bacteria, followed by eukaryotes (5.4%), archaea (1.1%), and viruses (0.69%). Genes encoding proteins involved in repairing UV-induced DNA damage and aerosolization of cells were ubiquitous across samples, and appear as fundamental requirements for the aeolian lifestyle, while genes coding for other important functions supporting the aeolian lifestyle (chemotaxis, aerotaxis, germination, thermal resistance, sporulation, and biofilm formation) varied among the communities sampled.
  • Factors Regulating the Relationship Between Total and Size-Fractionated Chlorophyll-a in Coastal Waters of the Red Sea.

    Brewin, Robert J W; Moran, Xose Anxelu G.; Raitsos, Dionysios E; Gittings, John A; Calleja Cortes, Maria de Lluch; Viegas, Miguel; Ansari, Mohd Ikram; Al-otaibi, Najwa Aziz; Huete-Stauffer, Tamara M; Hoteit, Ibrahim (Frontiers in microbiology, Frontiers Media SA, 2019-09-26) [Article]
    Phytoplankton biomass and size structure are recognized as key ecological indicators. With the aim to quantify the relationship between these two ecological indicators in tropical waters and understand controlling factors, we analyzed the total chlorophyll-a concentration, a measure of phytoplankton biomass, and its partitioning into three size classes of phytoplankton, using a series of observations collected at coastal sites in the central Red Sea. Over a period of 4 years, measurements of flow cytometry, size-fractionated chlorophyll-a concentration, and physical-chemical variables were collected near Thuwal in Saudi Arabia. We fitted a three-component model to the size-fractionated chlorophyll-a data to quantify the relationship between total chlorophyll and that in three size classes of phytoplankton [pico- (<2 μm), nano- (2-20 μm) and micro-phytoplankton (>20 μm)]. The model has an advantage over other more empirical methods in that its parameters are interpretable, expressed as the maximum chlorophyll-a concentration of small phytoplankton (pico- and combined pico-nanophytoplankton, Cpm and Cp,nm , respectively) and the fractional contribution of these two size classes to total chlorophyll-a as it tends to zero (D p and D p,n ). Residuals between the model and the data (model minus data) were compared with a range of other environmental variables available in the dataset. Residuals in pico- and combined pico-nanophytoplankton fractions of total chlorophyll-a were significantly correlated with water temperature (positively) and picoeukaryote cell number (negatively). We conducted a running fit of the model with increasing temperature and found a negative relationship between temperature and parameters Cpm and Cp,nm and a positive relationship between temperature and parameters D p and D p,n . By harnessing the relative red fluorescence of the flow cytometric data, we show that picoeukaryotes, which are higher in cell number in winter (cold) than summer (warm), contain higher chlorophyll per cell than other picophytoplankton and are slightly larger in size, possibly explaining the temperature shift in model parameters, though further evidence is needed to substantiate this finding. Our results emphasize the importance of knowing the water temperature and taxonomic composition of phytoplankton within each size class when understanding their relative contribution to total chlorophyll. Furthermore, our results have implications for the development of algorithms for inferring size-fractionated chlorophyll from satellite data, and for how the partitioning of total chlorophyll into the three size classes may change in a future ocean.
  • A genomic view of the reef-building coral Porites lutea and its microbial symbionts

    Robbins, Steven J.; ReFuGe2020 Consortium; Chan, Cheong Xin; Chan, Cheong Xin; Messer, Lauren F.; Messer, Lauren F.; Ying, Hua; Baker, Alexander; Bell, Sara C.; Ragan, Mark A.; Ragan, Mark A.; Miller, David J.; Foret, Sylvain; Voolstra, Christian R.; Tyson, Gene W.; Bourne, David G. (Nature Microbiology, Springer Science and Business Media LLC, 2019-09-23) [Article]
    Corals and the reef ecosystems that they support are in global decline due to increasing anthropogenic pressures such as climate change. However, effective reef conservation strategies are hampered by a limited mechanistic understanding of coral biology and the functional roles of the diverse microbial communities that underpin coral health. Here, we present an integrated genomic characterization of the coral species Porites lutea and its microbial partners. High-quality genomes were recovered from P. lutea, as well as a metagenome-assembled Cladocopium C15 (the dinoflagellate symbiont) and 52 bacterial and archaeal populations. Comparative genomic analysis revealed that many of the bacterial and archaeal genomes encode motifs that may be involved in maintaining association with the coral host and in supplying fixed carbon, B-vitamins and amino acids to their eukaryotic partners. Furthermore, mechanisms for ammonia, urea, nitrate, dimethylsulfoniopropionate and taurine transformation were identified that interlink members of the holobiont and may be important for nutrient acquisition and retention in oligotrophic waters. Our findings demonstrate the critical and diverse roles that microorganisms play within the coral holobiont and underscore the need to consider all of the components of the holobiont if we are to effectively inform reef conservation strategies.
  • Similar bacterial communities on healthy and injured skin of black tip reef sharks

    Pogoreutz, Claudia; Gore, Mauvis A.; Perna, Gabriela; Millar, Catriona; Nestler, Robert; Ormond, Rupert F.; Clarke, Christopher R.; Voolstra, Christian R. (Animal Microbiome, Springer Science and Business Media LLC, 2019-09-16) [Article]
    Background Sharks are in severe global decline due to human exploitation. The additional concern of emerging diseases for this ancient group of fish, however, remains poorly understood. While wild-caught and captive sharks may be susceptible to bacterial and transmissible diseases, recent reports suggest that shark skin may harbor properties that prevent infection, such as a specialized ultrastructure or innate immune properties, possibly related to associated microbial assemblages. To assess whether bacterial community composition differs between visibly healthy and insulted (injured) shark skin, we compared bacterial assemblages of skin covering the gills and the back from 44 wild-caught black-tip reef sharks (Carcharhinus melanopterus) from the Amirante Islands (Seychelles) via 16S rRNA gene amplicon sequencing. Results Shark skin-associated bacterial communities were diverse (5971 bacterial taxa from 375 families) and dominated by three families of the phylum Proteobacteria typical of marine organisms and environments (Rhodobacteraceae, Alteromonadaceae, Halomonadaceae). Significant differences in bacterial community composition of skin were observed for sharks collected from different sites, but not between healthy or injured skin samples or skin type (gills vs. back). The core microbiome (defined as bacterial taxa present in ≥50% of all samples) consisted of 12 bacterial taxa, which are commonly observed in marine organisms, some of which may be associated with animal host health. Conclusion The conserved bacterial community composition of healthy and injured shark skin samples suggests absence of severe bacterial infections or substantial pathogen propagation upon skin insult. While a mild bacterial infection may have gone undetected, the overall conserved bacterial community implies that bacterial function(s) may be maintained in injured skin. At present, the contribution of bacteria, besides intrinsic animal host factors, to counter skin infection and support rapid wound healing in sharks are unknown. This represents clear knowledge gaps that should be addressed in future work, e.g. by screening for antimicrobial properties of skin-associated bacterial isolates.
  • The many faced symbiotic snakelocks anemone (Anemonia viridis, Anthozoa): host and symbiont genetic differentiation among colour morphs

    Porro, Barbara; Mallien, Cédric; Hume, Benjamin; Pey, Alexis; Aubin, Emilie; Christen, Richard; Voolstra, Christian R.; Furla, Paola; Forcioli, Didier (Heredity, Springer Science and Business Media LLC, 2019-09-16) [Article]
    How can we explain morphological variations in a holobiont? The genetic determinism of phenotypes is not always obvious and could be circumstantial in complex organisms. In symbiotic cnidarians, it is known that morphology or colour can misrepresent a complex genetic and symbiotic diversity. Anemonia viridis is a symbiotic sea anemone from temperate seas. This species displays different colour morphs based on pigment content and lives in a wide geographical range. Here, we investigated whether colour morph differentiation correlated with host genetic diversity or associated symbiotic genetic diversity by using RAD sequencing and symbiotic dinoflagellate typing of 140 sea anemones from the English Channel and the Mediterranean Sea. We did not observe genetic differentiation among colour morphs of A. viridis at the animal host or symbiont level, rejecting the hypothesis that A. viridis colour morphs correspond to species level differences. Interestingly, we however identified at least four independent animal host genetic lineages in A. viridis that differed in their associated symbiont populations. In conclusion, although the functional role of the different morphotypes of A. viridis remains to be determined, our approach provides new insights on the existence of cryptic species within A. viridis.
  • A multimetric approach to evaluate offshore mussel aquaculture effects on the taxonomical and functional diversity of macrobenthic communities.

    Lacson, A Z; Piló, D; Pereira, F; Carvalho, A N; Curdia, Joao; Caetano, M; Drago, T; Santos, M N; Gaspar, M B (Marine environmental research, Elsevier BV, 2019-09-11) [Article]
    A multimetric approach was used to detect structural, compositional, and functional shifts in the underlying macrobenthic communities of an offshore mussel (Mytilus galloprovincialis) farm in a Portuguese Aquaculture Production Area. Sampling stations distributed inside and outside this area were used to evaluate sediment descriptors and macrobenthic samples collected before (April and September 2010) and after (June and September 2014) the initiation of mussel farming. Sediment fine fraction, organic matter content, and trace element concentrations were found to increase with depth, independently from the mussel farm. Moreover, the structure and composition of the macrobenthic communities were likewise structured by depth. Turnover was the dominant temporal and spatial pattern of beta diversity for all communities. Furthermore, the functional diversity of these communities was unaffected by the mussel farm. These results suggested that an offshore profile allowed hydrodynamic conditions to weaken the impact of mussel farming and highlighted the importance of conducting an integrative multimetric analysis when studying aquaculture impacts on benthic communities.
  • Multi-method assessment of whale shark (Rhincodon typus) residency, distribution, and dispersal behavior at an aggregation site in the Red Sea.

    Cochran, Jesse; Braun, Camrin D; Cagua, Edgar F.; Campbell, Michael F; Hardenstine, Royale; Kattan, Alexander; Priest, Mark A; Sinclair-Taylor, Tane H; Skomal, Gregory B; Sultan, Sahar; Sun, Lu; Thorrold, Simon R; Berumen, Michael L. (PloS one, Public Library of Science (PLoS), 2019-09-10) [Article]
    Whale sharks (Rhincodon typus) are typically dispersed throughout their circumtropical range, but the species is also known to aggregate in specific coastal areas. Accurate site descriptions associated with these aggregations are essential for the conservation of R. typus, an Endangered species. Although aggregations have become valuable hubs for research, most site descriptions rely heavily on sightings data. In the present study, visual census, passive acoustic monitoring, and long range satellite telemetry were combined to track the movements of R. typus from Shib Habil, a reef-associated aggregation site in the Red Sea. An array of 63 receiver stations was used to record the presence of 84 acoustically tagged sharks (35 females, 37 males, 12 undetermined) from April 2010 to May 2016. Over the same period, identification photos were taken for 76 of these tagged individuals and 38 were fitted with satellite transmitters. In total of 37,461 acoustic detections, 210 visual encounters, and 33 satellite tracks were analyzed to describe the sharks' movement ecology. The results demonstrate that the aggregation is seasonal, mostly concentrated on the exposed side of Shib Habil, and seems to attract sharks of both sexes in roughly equal numbers. The combined methodologies also tracked 15 interannual homing-migrations, demonstrating that many sharks leave the area before returning in later years. When compared to acoustic studies from other aggregations, these results demonstrate that R. typus exhibits diverse, site-specific ecologies across its range. Sightings-independent data from acoustic telemetry and other sources are an effective means of validating more common visual surveys.
  • The future of Blue Carbon science.

    Macreadie, Peter I; Anton Gamazo, Andrea; Raven, John A; Beaumont, Nicola; Connolly, Rod M; Friess, Daniel A; Kelleway, Jeffrey J; Kennedy, Hilary; Kuwae, Tomohiro; Lavery, P. S.; Lovelock, Catherine E; Smale, Dan A; Apostolaki, Eugenia T; Atwood, Trisha B; Baldock, Jeff; Bianchi, Thomas S; Chmura, Gail L; Eyre, Bradley D; Fourqurean, J. W.; Hall-Spencer, Jason M; Huxham, Mark; Hendriks, Iris E; Krause-Jensen, Dorte; Laffoley, Dan; Luisetti, Tiziana; Marbà, Núria; Masqué, Pere; McGlathery, Karen J; Megonigal, J Patrick; Murdiyarso, Daniel; Russell, Bayden D; Santos, Rui; Serrano, Oscar; Silliman, Brian R; Watanabe, Kenta; Duarte, Carlos M. (Nature communications, Springer Science and Business Media LLC, 2019-09-07) [Article]
    The term Blue Carbon (BC) was first coined a decade ago to describe the disproportionately large contribution of coastal vegetated ecosystems to global carbon sequestration. The role of BC in climate change mitigation and adaptation has now reached international prominence. To help prioritise future research, we assembled leading experts in the field to agree upon the top-ten pending questions in BC science. Understanding how climate change affects carbon accumulation in mature BC ecosystems and during their restoration was a high priority. Controversial questions included the role of carbonate and macroalgae in BC cycling, and the degree to which greenhouse gases are released following disturbance of BC ecosystems. Scientists seek improved precision of the extent of BC ecosystems; techniques to determine BC provenance; understanding of the factors that influence sequestration in BC ecosystems, with the corresponding value of BC; and the management actions that are effective in enhancing this value. Overall this overview provides a comprehensive road map for the coming decades on future research in BC science.
  • Flexible tag design for semi-continuous wireless data acquisition from marine animals

    Karimi, Muhammad Akram; Zhang, Qingle; Kuo, Yen Hung; Shaikh, Sohail F.; Kaidarova, Altynay; Geraldi, Nathan; Hussain, Muhammad Mustafa; Kosel, Jürgen; Duarte, Carlos M.; Shamim, Atif (Flexible and Printed Electronics, IOP Publishing, 2019-09-06) [Article]
    Acquisition of sensor data from tagged marine animals has always been a challenge. Presently, we come across two extreme mechanisms to acquire marine data. For continuous data acquisition, hundreds of kilometers of optical fiber links are used which in addition to being expensive, are impractical in certain circumstances. On the other extreme, data is retrieved in an offline and invasive manner after removing the sensor tag from the animal's skin. This paper presents a semi-continuous method of acquiring marine data without requiring tags to be removed from the sea animal. Marine data is temporarily stored in the tag's memory, which is then automatically synced to floating receivers as soon as the animal rises to the water surface. To ensure effective wireless communication in an unpredictable environment, a quasi-isotropic antenna has been designed which works equally well irrespective of the orientation of the tagged animal. In contrast to existing rigid wireless devices, the tag presented in this work is flexible and thus convenient for mounting on marine animals. The tag has been initially tested in air as a standalone unit with a communication range of 120m. During tests in water, with the tag mounted on the skin of a crab, a range of 12m has been observed. In a system-level test, the muscle activity of a small giant clam (Tridacna maxima) has been recorded in real time via the non-invasive wireless tag.
  • Multiple stressor effects on coral reef ecosystems.

    Ellis, J I; Jamil, Tahira; Anlauf, Holger; Coker, Darren James; Curdia, Joao; Hewitt, J; Jones, B H; Krokos, Georgios; Kürten, Benjamin; Prasad, D; Roth, Florian; Carvalho, Susana; Hoteit, Ibrahim (Global change biology, Wiley, 2019-09-05) [Article]
    Global climate change has profound implications on species distributions and ecosystem functioning. In the coastal zone, ecological responses may be driven by various biogeochemical and physical environmental factors. Synergistic interactions can occur when the combined effects of stressors exceed their individual effects. The Red Sea, characterized by strong gradients in temperature, salinity, and nutrients along the latitudinal axis provides a unique opportunity to study ecological responses over a range of these environmental variables. Using multiple linear regression models integrating in situ, satellite and oceanographic data, we investigated the response of coral reef taxa to local stressors and recent climate variability. Taxa and functional groups responded to a combination of climate (temperature, salinity, air-sea heat fluxes, irradiance, wind speed), fishing pressure and biogeochemical (chlorophyll a and nutrients - phosphate, nitrate, nitrite) factors. The regression model for each species showed interactive effects of climate, fishing pressure and nutrient variables. The nature of the effects (antagonistic or synergistic) was dependent on the species and stressor pair. Variables consistently associated with the highest number of synergistic interactions included heat flux terms, temperature, and wind speed followed by fishing pressure. Hard corals and coralline algae abundance were sensitive to changing environmental conditions where synergistic interactions decreased their percentage cover. These synergistic interactions suggest that the negative effects of fishing pressure and eutrophication may exacerbate the impact of climate change on corals. A high number of interactions were also recorded for algae, however for this group, synergistic interactions increased algal abundance. This study is unique in applying regression analysis to multiple environmental variables simultaneously to understand stressor interactions in the field. The observed responses have important implications for understanding climate change impacts on marine ecosystems and whether managing local stressors, such as nutrient enrichment and fishing activities, may help mitigate global drivers of change. This article is protected by copyright. All rights reserved.
  • Morphology and molecules reveal two new species of Porites (Scleractinia, Poritidae) from the Red Sea and the Gulf of Aden

    Terraneo, Tullia Isotta; Benzoni, Francesca; Baird, Andrew H.; Arrigoni, Roberto; Berumen, Michael L. (Systematics and Biodiversity, Informa UK Limited, 2019-09-04) [Article]
    Two new reef coral species, Porites farasani sp. nov. and Porites hadramauti sp. nov. (Scleractinia, Poritidae), are described from the Red Sea and the Gulf of Aden. Porites farasani sp. nov. only occurs in the Farasan Islands in the southern Red Sea, while P. hadramauti sp. nov. has been collected in the Yemen Hadramaut region in the Gulf of Aden. Both species presented striking in situ differences with respect to other Porites species, and were characterized by small encrusting colonies and unusual polyp colouration. In order to test the genetic distinctiveness of P. farasani sp. nov. and P. hadramauti sp. nov. between each other and with respect to other representatives in the genus Porites, we investigated their evolutionary relationships with eight other morphological species of Porites occurring in the Red Sea and in the Gulf of Aden. Two DNA loci, the mitochondrial putative control region and the nuclear ribosomal ITS region, were sequenced, and three species delimitation approaches based on barcoding threshold (Automated Barcoding Gap Discovery) and coalescence theory (Poisson-Tree process, Generalized Mixed Yule Coalescent) were applied. Phylogenetic and species delimitation analyses were overall concordant, resolving P. farasani sp. nov. and P. hadramauti sp. nov. as two divergent but closely related lineages. Of the other morphologically defined Porites species, three were genetically differentiated (P. rus, P. columnaris and P. fontanesii), but five were genetically indistinguishable. The discovery of two regional endemics confirms the importance of the Red Sea and the Gulf of Aden as regions of high biodiversity and suggests the need for an integration of genome-wide molecular data with the re-evaluation of skeletal structures in the systematics of Porites.
  • Oxygen supersaturation protects coastal marine fauna from ocean warming

    Giomi, Folco; Barausse, Alberto; Duarte, Carlos M.; Booth, Jenny; Agusti, Susana; Saderne, Vincent; Anton Gamazo, Andrea; Daffonchio, Daniele; Fusi, Marco (Science Advances, American Association for the Advancement of Science (AAAS), 2019-09-04) [Article]
    Ocean warming affects the life history and fitness of marine organisms by, among others, increasing animal metabolism and reducing oxygen availability. In coastal habitats, animals live in close association with photosynthetic organisms whose oxygen supply supports metabolic demands and may compensate for acute warming. Using a unique high-frequency monitoring dataset, we show that oxygen supersaturation resulting from photosynthesis closely parallels sea temperature rise during diel cycles in Red Sea coastal habitats. We experimentally demonstrate that oxygen supersaturation extends the survival to more extreme temperatures of six species from four phyla. We clarify the mechanistic basis of the extended thermal tolerance by showing that hyperoxia fulfills the increased metabolic demand at high temperatures. By modeling 1 year of water temperatures and oxygen concentrations, we predict that oxygen supersaturation from photosynthetic activity invariably fuels peak animal metabolic demand, representing an underestimated factor of resistance and resilience to ocean warming in ectotherms.
  • MAP4K4 associates with BIK1 to regulate plant innate immunity.

    Jiang, Yunhe; Han, Baoda; Zhang, Huoming; Mariappan, Kiruthiga; Bigeard, Jean; Colcombet, Jean; Hirt, Heribert (EMBO reports, EMBO, 2019-09-03) [Article]
    To perceive pathogens, plants employ pattern recognition receptor (PRR) complexes, which then transmit these signals via the receptor-like cytoplasmic kinase BIK1 to induce defense responses. How BIK1 activity and stability are controlled is still not completely understood. Here, we show that the Hippo/STE20 homolog MAP4K4 regulates BIK1-mediated immune responses. MAP4K4 associates and phosphorylates BIK1 at Ser233, Ser236, and Thr242 to ensure BIK1 stability and activity. Furthermore, MAP4K4 phosphorylates PP2C38 at Ser77 to enable flg22-induced BIK1 activation. Our results uncover that a Hippo/STE20 homolog, MAP4K4, maintains the homeostasis of the central immune component BIK1.
  • Hydrodynamic and biological constraints on group cohesion in plankton.

    Chaput, Romain; Majoris, John Edwin; Buston, Peter M; Paris, Claire B (Journal of theoretical biology, Elsevier BV, 2019-09-02) [Article]
    The dynamics of plankton in the ocean are determined by biophysical interactions. Although physics and biotic behaviors are known to influence the observed patchiness of planktonic populations, it is still unclear how much, and if, group behavior contributes to this biophysical interaction. Here, we demonstrate how simple rules of behavior can enhance or inhibit active group cohesion in plankton in a turbulent environment. In this study, we used coral-reef fish larvae as a model to investigate the interaction between microscale turbulence and planktonic organisms. We synthesized available information on the swimming speeds and sizes of reef fish larvae, and developed a set of equations to investigate the effects of viscosity and turbulence on larvae dispersion. We then calculated the critical dispersion rates for three different swimming strategies - cruise, random-walk, and pause-travel - to determine which strategies could facilitate group cohesion during dispersal. Our results indicate that swimming strategies and migration to low-turbulence regions are the key to maintaining group cohesion, suggesting that many reef fish species have the potential to remain together, from hatching to settlement. In addition, larvae might change their swimming strategies to maintain group cohesion, depending on environmental conditions and/or their ontogenic stage. This study provides a better understanding of the hydrodynamic and biological constraints on group formation and cohesion in planktonic organisms, and reveals a wide range of conditions under which group formation may occur.
  • Implications of nutrient enrichment for the conservation and management of seagrass Zostera muelleri meadows

    Li, Moyang; Lundquist, Carolyn J.; Pilditch, Conrad A.; Rees, T. A.V.; Ellis, Joanne (Aquatic Conservation: Marine and Freshwater Ecosystems, Wiley, 2019-09-01) [Article]
    Nutrient overenrichment in aquatic environments, or eutrophication, is increasingly affecting seagrass habitats around the world, leading to the degradation of seagrass ecosystems and the loss of associated ecosystem services. The resistance of seagrass to nutrient enrichment is believed to be site specific, yet the direct correlations between environmental factors and the resistance of seagrass meadows has not yet been adequately resolved. The response of seagrass beds to long-term multiple-level sediment nutrient enrichment represents a current research gap. This study therefore assessed the in situ long-term influence of four levels of sediment urea fertilizer addition on Zostera muelleri plants using a manipulative experimental design at three sites with diverse sediment characteristics. Specifically, this study investigated the response of porewater nutrient concentration, seagrass morphology indices, and seagrass plant tissue carbon and nitrogen contents under experimental nutrient stress levels. Over a 13-month experiment, sediment nutrient addition substantially increased the ammonium concentrations in the sediment porewater, significantly decreased seagrass morphology indices, and caused a carbon and nitrogen imbalance in plant tissues. Ammonium toxicity was more pronounced in seagrass meadows growing on sandy substrates with lower relative above-ground biomass, which showed low resistance to eutrophication at sediment ammonium concentrations of up to 1 × 104 μM. Plants growing in muddy sand substrates with higher relative above-ground biomass were more resistant to nutrient impacts, however, with a delayed negative response observed in response to higher nutrient concentrations (up to 1 × 105 μM). Our findings suggest that seagrasses in low-nutrient sandy environments show more rapid responses to eutrophication, although seagrasses in both sandy and muddy substrates exhibited declines in response to a long-term elevation of sediment nutrient concentrations. While continuing to assess the relative susceptibility of seagrass habitats across differing environments to inform coastal management, conservation efforts should allocate resources accordingly and prioritize reducing nutrient overenrichment in sensitive seagrass meadows.
  • Environmental conditions and paternal care determine hatching synchronicity of coral reef fish larvae

    Chaput, Romain; Majoris, John Edwin; Guigand, Cédric M.; Huse, Megan; D’Alessandro, Evan K. (Marine Biology, Springer Science and Business Media LLC, 2019-09-01) [Article]
    For all fishes, hatching is a short but crucial event, and the conditions under which it occurs considerably influence the success of the larvae. For coral reef fish, hatching is even more important because it marks the beginning of the dispersal phase. The timing of hatching dictates the conditions that the larvae will encounter, potentially influencing their survival and dispersal. Despite this importance, very few studies have looked at hatching of marine fishes in the natural environment because of important technical constrains. In this study, we directly examined the temporal pattern of hatching during the night. Using remote night vision cameras and infrared lights to avoid disturbances, we successfully documented in situ hatching events of three coral reef fish species, all benthic brooders (Abudefduf saxatilis, Stegastes partitus, and Elacatinus lori). Hatching timing, rate, and duration were computed from the observations, and highlight different hatching strategies used by the fish species. The analysis of the fish behaviors shows that the males display parental care beyond the incubation period of the eggs and increase activity during the hatching events. With this study, we can relate the hatching events to the environmental context, giving us a better understanding of the factors influencing the beginning of the larval phase. These observations highlight the benefit of in situ studies to better understand the characteristics and potential consequences of hatching.
  • Herding mesopelagic fish by light

    Kaartvedt, Stein; Røstad, Anders; Opdal, Anders Frugård; Aksnes, Dag L. (Marine Ecology Progress Series, Inter-Research Science Center, 2019-08-29) [Article]
    To assess organisms forming mesopelagic scattering layers in the Red Sea, we took advantage of their reactions to light. We used a remotely operated vehicle (ROV) equipped with LED lamps for herding the acoustic targets down to the bottom (700 m), while concurrently monitoring the event by shipborne and deployed echosounders as well as video footage from the ROV. In essence, entire mesopelagic scattering layers at 38 kHz were moved downwards until the organisms became trapped and concentrated at the bottom and identified as fish from video images. However, responses to the artificial light source appeared to include both repulsion and attraction. An individual-based model reproduced the herding event by assuming a dichotomous response to light where targets close to the light source are attracted, while targets further away are repulsed. We hypothesize that attraction is associated with the artificial light acting as a point source (beam light), while the repulsion is associated with the artificial light acting as diffuse light.

View more