In-situ Effects of Eutrophication and Overfishing on Physiology and Bacterial Diversity of the Red Sea Coral Acropora hemprichii

Coral reefs of the Central Red Sea display a high degree of endemism, and are increasingly threatened by anthropogenic effects due to intense local coastal development measures. Overfishing and eutrophication are among the most significant local pressures on these reefs, but there is no information available about their potential effects on the associated microbial community. Therefore, we compared holobiont physiology and 16S-based bacterial communities of tissue and mucus of the hard coral Acropora hemprichii after 1 and 16 weeks of in-situ inorganic nutrient enrichment (via fertilizer diffusion) and/or herbivore exclusion (via caging) in an offshore reef of the Central Red Sea. Simulated eutrophication and/or overfishing treatments did not affect coral physiology with respect to coral respiration rates, chlorophyll a content, zooxanthellae abundance, or δ ¹⁵N isotopic signatures. The bacterial community of A. hemprichii was rich and uneven, and diversity increased over time in all treatments. While distinct bacterial species were identified as a consequence of eutrophication, overfishing, or both, two bacterial species that could be classified to the genus Endozoicomonas were consistently abundant and constituted two thirds of bacteria in the coral. Several nitrogen-fixing and denitrifying bacteria were found in the coral specimens that were exposed to experimentally increased nutrients. However, no particular bacterial species was consistently associated with the coral under a given treatment and the single effects of manipulated eutrophication and overfishing could not predict the combined effect. Our data underlines the importance of conducting field studies in a holobiont framework, taking both, physiological and molecular measures into account.     

Impact of Herbivore Identity on Algal Succession and Coral Growth on a Caribbean Reef

Background

Herbivory is an important top-down force on coral reefs that regulates macroalgal abundance, mediates competitive interactions between macroalgae and corals, and provides resilience following disturbances such as hurricanes and coral bleaching. However, reductions in herbivore diversity and abundance via disease or over-fishing may harm corals directly and may indirectly increase coral susceptibility to other disturbances.

Methodology and Principal Findings

In two experiments over two years, we enclosed equivalent densities and masses of either single-species or mixed-species of herbivorous fishes in replicate, 4 m² cages at a depth of 17 m on a reef in the Florida Keys, USA to evaluate the effects of herbivore identity and species richness on colonization and development of macroalgal communities and the cascading effects of algae on coral growth. In Year 1, we used the redband parrotfish (Sparisoma aurofrenatum) and the ocean surgeonfish (Acanthurus bahianus); in Year 2, we used the redband parrotfish and the princess parrotfish (Scarus taeniopterus). On new substrates, rapid grazing by ocean surgeonfish and princess parrotfish kept communities in an early successional stage dominated by short, filamentous algae and crustose coralline algae that did not suppress coral growth. In contrast, feeding by redband parrotfish allowed an accumulation of tall filaments and later successional macroalgae that suppressed coral growth. These patterns contrast with patterns from established communities not undergoing primary succession; on established substrates redband parrotfish significantly reduced upright macroalgal cover while ocean surgeonfish and princess parrotfish allowed significant increases in late successional macroalgae.

Significance

This study further highlights the importance of biodiversity in affecting ecosystem function in that different species of herbivorous fishes had very different impacts on reef communities depending on the developmental stage of the community. The species-specific effects of herbivorous fishes suggest that a species-rich herbivore fauna can be critical in providing the resilience that reefs need for recovery from common disturbances such as coral bleaching and storm damage.     

Spectral Diversity and Regulation of Coral Fluorescence in a Mesophotic Reef Habitat in the Red Sea

The phenomenon of coral fluorescence in mesophotic reefs, although well described for shallow waters, remains largely unstudied. We found that representatives of many scleractinian species are brightly fluorescent at depths of 50–60 m at the Interuniversity Institute for Marine Sciences (IUI) reef in Eilat, Israel. Some of these fluorescent species have distribution maxima at mesophotic depths (40–100 m). Several individuals from these depths displayed yellow or orange-red fluorescence, the latter being essentially absent in corals from the shallowest parts of this reef. We demonstrate experimentally that in some cases the production of fluorescent pigments is independent of the exposure to light; while in others, the fluorescence signature is altered or lost when the animals are kept in darkness. Furthermore, we show that green-to-red photoconversion of fluorescent pigments mediated by short-wavelength light can occur also at depths where ultraviolet wavelengths are absent from the underwater light field. Intraspecific colour polymorphisms regarding the colour of the tissue fluorescence, common among shallow water corals, were also observed for mesophotic species. Our results suggest that fluorescent pigments in mesophotic reefs fulfil a distinct biological function and offer promising application potential for coral-reef monitoring and biomedical imaging.     

Vibrio owensii Induces the Tissue Loss Disease Montipora White Syndrome in the Hawaiian Reef Coral Montipora capitata

Incidences of coral disease in the Indo-Pacific are increasing at an alarming rate. In particular, Montipora white syndrome, a tissue-loss disease found on corals throughout the Hawaiian archipelago, has the potential to degrade Hawaii’s reefs. To identify the etiologic agent of Montipora white syndrome, bacteria were isolated from a diseased fragment of Montipora capitata and used in a screen for virulent strains. A single isolate, designated strain OCN002, recreated disease signs in 53% of coral fragments in laboratory infection trials when added to a final concentration of 10⁷ cells/ml of seawater. In addition to displaying similar signs of disease, diseased coral fragments from the field and those from infection trials both had a dramatic increase in the abundance of associated culturable bacteria, with those of the genus Vibiro well represented. Bacteria isolated from diseased fragments used in infection trails were shown to be descendants of the original OCN002 inocula based on both the presence of a plasmid introduced to genetically tag the strain and the sequence of a region of the OCN002 genome. In contrast, OCN002 was not re-isolated from fragments that were exposed to the strain but did not develop tissue loss. Sequencing of the rrsH gene, metabolic characterization, as well as multilocus sequence analysis indicated that OCN002 is a strain of the recently described species Vibrio owensii. This investigation of Montipora white syndrome recognizes V. owensii OCN002 as the first bacterial coral pathogen identified from Hawaii’s reefs and expands the range of bacteria known to cause disease in corals.     

Coral Reef Community Composition in the Context of Disturbance History on the Great Barrier Reef,Australia

Much research on coral reefs has documented differential declines in coral and associated organisms. In order to contextualise this general degradation, research on community composition is necessary in the context of varied disturbance histories and the biological processes and physical features thought to retard or promote recovery. We conducted a spatial assessment of coral reef communities across five reefs of the central Great Barrier Reef, Australia, with known disturbance histories, and assessed patterns of coral cover and community composition related to a range of other variables thought to be important for reef dynamics. Two of the reefs had not been extensively disturbed for at least 15 years prior to the surveys. Three of the reefs had been severely impacted by crown-of-thorns starfish outbreaks and coral bleaching approximately a decade before the surveys, from which only one of them was showing signs of recovery based on independent surveys. We incorporated wave exposure (sheltered and exposed) and reef zone (slope, crest and flat) into our design, providing a comprehensive assessment of the spatial patterns in community composition on these reefs. Categorising corals into life history groupings, we document major coral community differences in the unrecovered reefs, compared to the composition and covers found on the undisturbed reefs. The recovered reef, despite having similar coral cover, had a different community composition from the undisturbed reefs, which may indicate slow successional processes, or a different natural community dominance pattern due to hydrology and other oceanographic factors. The variables that best correlated with patterns in the coral community among sites included the density of juvenile corals, herbivore fish biomass, fish species richness and the cover of macroalgae. Given increasing impacts to the Great Barrier Reef, efforts to mitigate local stressors will be imperative to encouraging coral communities to persist into the future.     

Budget of Primary Production and Dinitrogen Fixation in a Highly Seasonal Red Sea Coral Reef

Biological dinitrogen (N₂) fixation (diazotrophy, BNF) relieves marine primary producers of nitrogen (N) limitation in a large part of the world oceans. N concentrations are particularly low in tropical regions where coral reefs are located, and N is therefore a key limiting nutrient for these productive ecosystems. In this context, the importance of diazotrophy for reef productivity is still not resolved, with studies up to now lacking organismal and seasonal resolution. Here, we present a budget of gross primary production (GPP) and BNF for a highly seasonal Red Sea fringing reef, based on ecophysiological and benthic cover measurements combined with geospatial analyses. Benthic GPP varied from 215 to 262 mmol C m^?2 reef d^?1, with hard corals making the largest contribution (41–76%). Diazotrophy was omnipresent in space and time, and benthic BNF varied from 0.16 to 0.92 mmol N m^?2 reef d^?1. Planktonic GPP and BNF rates were respectively approximately 60- and 20-fold lower than those of the benthos, emphasizing the importance of the benthic compartment in reef biogeochemical cycling. BNF showed higher sensitivity to seasonality than GPP, implying greater climatic control on reef BNF. Up to about 20% of net reef primary production could be supported by BNF during summer, suggesting a strong biogeochemical coupling between diazotrophy and the reef carbon cycle.     

Benthic Composition of a Healthy Subtropical Reef: Baseline Species-Level Cover,with an Emphasis on Algae,in the Northwestern Hawaiian Islands

The Northwestern Hawaiian Islands (NWHI) are considered to be among the most pristine coral reef ecosystems remaining on the planet. These reefs naturally contain a high percent cover of algal functional groups with relatively low coral abundance and exhibit thriving fish communities dominated by top predators. Despite their highly protected status, these reefs are at risk from both direct and indirect anthropogenic sources. This study provides the first comprehensive data on percent coverage of algae, coral, and non-coral invertebrates at the species level, and investigates spatial diversity patterns across the archipelago to document benthic communities before further environmental changes occur in response to global warming and ocean acidification. Monitoring studies show that non-calcified macroalgae cover a greater percentage of substrate than corals on many high latitude reef sites. Forereef habitats in atoll systems often contain high abundances of the green macroalga Microdictyon setchellianum and the brown macroalga Lobophora variegata, yet these organisms were uncommon in forereefs of non-atoll systems. Species of the brown macroalgal genera Padina, Sargassum, and Stypopodium and the red macroalgal genus Laurencia became increasingly common in the two northernmost atolls of the island chain but were uncommon components of more southerly islands. Conversely, the scleractinian coral Porites lobata was common on forereefs at southern islands but less common at northern islands. Currently accepted paradigms of what constitutes a “healthy” reef may not apply to the subtropical NWHI, and metrics used to gauge reef health (e.g., high coral cover) need to be reevaluated.     

The Response of Antarctic Sea Ice Algae to Changes in pH and CO2

Ocean acidification substantially alters ocean carbon chemistry and hence pH but the effects on sea ice formation and the CO₂ concentration in the enclosed brine channels are unknown. Microbial communities inhabiting sea ice ecosystems currently contribute 10–50% of the annual primary production of polar seas, supporting overwintering zooplankton species, especially Antarctic krill, and seeding spring phytoplankton blooms. Ocean acidification is occurring in all surface waters but the strongest effects will be experienced in polar ecosystems with significant effects on all trophic levels. Brine algae collected from McMurdo Sound (Antarctica) sea ice was incubated in situ under various carbonate chemistry conditions. The carbon chemistry was manipulated with acid, bicarbonate and bases to produce a pCO₂ and pH range from 238 to 6066 µatm and 7.19 to 8.66, respectively. Elevated pCO₂ positively affected the growth rate of the brine algal community, dominated by the unique ice dinoflagellate, Polarella glacialis. Growth rates were significantly reduced when pH dropped below 7.6. However, when the pH was held constant and the pCO₂ increased, growth rates of the brine algae increased by more than 20% and showed no decline at pCO₂ values more than five times current ambient levels. We suggest that projected increases in seawater pCO₂, associated with OA, will not adversely impact brine algal communities.     

Productivity and abundance of large sponge populations on Flinders Reef flats,Coral Sea

Large populations of flattened sponges with cyanobacterial symbionts were observed on the shallow reef-flats of the Flinders Reefs, Coral Sea. Estimates of these populations indicated as many as 60 individuals with a total wet biomass of 1.2 kg per m² in some areas. Along a metre wide transect across 1.3 km of reef flat the population was estimated at 530 kg wet weight sponge (mean 411 g m^-2). The four prominent species had instantaneous P/R ratios between 1.3 and 1.8 at optimum light such that photosynthetic productivity was calculated to provide between 61 and 80% of sponge energy requirements in summer and 48 to 64% in winter. While such sponge beds are a prominent feature of these reefs, they appear to contribute less than 10% of gross reef-flat productivity.Contribution no. 352 from the Australian Institute of Marine Science     

氮、磷营养盐对底栖硅藻的生长及生化组成影响

目的:研究了从福建连江海域分离得到的一株野生底栖硅藻(Nitzschia.constricta)的生长和生理特性.方法:测定了在不同氮磷浓度条件下比增长速率、色素,以及不同时期底栖硅藻蛋白和胞外多糖的积累情况.结果:当硝酸氮浓度为900mg/l时,获得最大比增长速率0.21和叶绿素a含量4.31mg/l、类胡萝卜素含量3.44mg/l、胞外多糖产率90.57μg/ml.当氮浓度为75mg/l时,在第10d得到最大蛋白产率28.90μg/ml.当磷浓度为4.4mg/l时,可得到最大比增长速率0.13、叶绿素a含量3.42mg/l、类胡萝卜素2.82mg/l、蛋白含量23.16μg/ml,无磷培养基中第5d的胞外多糖产率最高13.51μg/ml.结论:氮磷营养盐浓度的增加促进了此种底栖硅藻的生长,但不一定会促进蛋白及胞外多糖的产生.     

Sexual Reproduction and Seasonality of the Alaskan Red Tree Coral,Primnoa pacifica

The red tree coral Primnoa pacifica is an important habitat forming octocoral in North Pacific waters. Given the prominence of this species in shelf and upper slope areas of the Gulf of Alaska where fishing disturbance can be high, it may be able to sustain healthy populations through adaptive reproductive processes. This study was designed to test this hypothesis, examining reproductive mode, seasonality and fecundity in both undamaged and simulated damaged colonies over the course of 16 months using a deepwater-emerged population in Tracy Arm Fjord. Females within the population developed asynchronously, though males showed trends of synchronicity, with production of immature spermatocysts heightened in December/January and maturation of gametes in the fall months. Periodicity of individuals varied from a single year reproductive event to some individuals taking more than the 16 months sampled to produce viable gametes. Multiple stages of gametes occurred in polyps of the same colony during most sampling periods. Mean oocyte size ranged from 50 to 200 µm in any season, and maximum oocyte size (802 µm) suggests a lecithotrophic larva. No brooding larvae were found during this study, though unfertilized oocytes were found adhered to the outside of polyps, where they are presumably fertilized. This species demonstrated size-dependent reproduction, with gametes first forming in colonies over 42-cm length, and steady oocyte sizes being achieved after reaching 80-cm in length. The average fecundity was 86 (±12) total oocytes per polyp, and 17 (±12) potential per polyp fecundity. Sub-lethal injury by removing 21–40% of colony tissue had no significant reproductive response in males or females over the course of this study, except for a corresponding loss in overall colony fecundity. The reproductive patterns and long gamete generation times observed in this study indicate that recruitment events are likely to be highly sporadic in this species increasing its vulnerability to anthropogenic disturbances.     

Benthic foraminiferal associations in the Northern Bay of Safaga, Red Sea, Egypt

In the shallow-water area (0–70 m) of the Northern Bay of Safaga, 73 surface samples were studied with respect to total foraminiferal fauna. The samples cover a great variety of shallow-water environments and yielded 239 foraminiferal taxa. Based on q-mode cluster analysis, and tested by canonical discriminant analysis, the samples are grouped into 13 foraminiferal associations, each characterized by several species:

(1) Quinqueloculina mosharrafai-Borelis schlumbergeri-Brizalina simpsoni Ass.,

(2) Heterostegina depressa-Amphlstegina lessonii/bicirculata Ass.,

(3) Cibicidids-Rosalina-Amphistegina lobifera-Pseudoschlumbergerina ovata Ass.,

(4) Peneroplis planatus Ass.,

(5) Peneroplis planatus-Varidentella neostriatula Ass.,

(6) Peneroplis planatus-Coscinospira hemprichii-Varidentella neostriatula Ass.,

(7) Quinqueloculina spp. Ass.,

(8) Hauerina diversa-Sorites orbiculus Ass.,

(9) Verneuilina sp.-n Articulina pacifica-Reussella simplex Ass.,

(10) Textularia agglutinans/rugulosa-Bolivina variabilis Ass.,

(11) Textularia agglutinans-Challengerella bradyi-Elphidium jenseni/simplex Ass.,

(12) Operculina ammonoides-Adelosina laevigata-Brizalina striatula/subspathulata Ass.,

(13) Bolivina variabilis—Miliolinella-Nonion fabum-Elphidium simplex Ass.

The characteristic forms of each association are linked to specific environmental parameters and modes of life. As long as taxonomic uniformitarianism can be applied, similar associations with comparable ecological demands may also be detected in the fossil record. For comparisons with taxonomically different material the 13 associations are summarized into 4 categories each reflecting a specific type of substrate. In the fossil record these categories may be recognized by general morphological characteristics of the foraminiferal tests and by sedimentological data. The 4 substrate types are: hardground, sand (with or without seagrass and/or corals), firmground, and soft bottom.     

Coral communities and coral-bivalve associations in the northern Red Sea at Safaga,Egypt

Summary The reefs near Safaga, Egypt, are built mainly by coral species ofPorites andAcropora. These genera are in general important for the formation of coral communities and reef structures. WhileMontipora orPavona are also species rich, their mean colony size is too small for a substantial role in the build-up of carbonate mass. Yet as a host coral,Montipora is more important thanPorites; both may accommodate the pectinidPedum and certain species of mytilidLithophaga. Such associations appear to be typical for specific reef areas and to be correlated to the food supply of the bivalves. These findings can be used for an actuopaleontological interpretation of the fossil situation. In addition to the frequency of occurrence, factors such as the growth form, growth rate, skeletal density and lifespan of corals are essential in determining their share in reef construction.     

Effect of Simulated Rainfall on Efficacy and Leaching of Two Formulations of Fenamiphos

Recoverable fenamiphos in the soil and residue in squash following different simulated rainfall treatments after nematicide application were determined in a 2-year study. Efficacy of fenamiphos also was evaluated. Fenamiphos treatments (3 SC and 15 G) were broadcast (6.7 kg a.i./ha) over plots and incorporated into the top 15 cm of soil immediately before planting ''Dixie Hybrid'' squash. Simulated rainfall treatments of 0, 2.5, and 5.0 cm water were applied 1 day after fenamiphos application. Soil samples from 0- to 8-cm, 8- to 15-cm, and 15- to 30-cm soil depths were collected 1 day after the simulated rainfall applications and analyzed for fenamiphos, fenamiphos sulfoxide (FSO), and fenamiphos sulfone (FSO₂). Squash was analyzed for total fenamiphos residue. Greater concentrations of fenamiphos were present in the 0- to 8-cm soil layer following application of 15 G than 3 SC formulation. Simulated rainfall treatments did not alter fenamiphos concentrations in any soil layer (except for the 0- to 8-cm depth in 1992) or concentration of FSO and total fenamiphos residue in the 15- to 30-cm soil layer. Root-gall indices were greater from untreated than most fenamiphos-treated plots, but were not affected by formulations of fenamiphos or simulated rainfall treatments. Concentrations of total residue in squash ranged from 1 to 4 μg FSO₂/g.     

Differential Impact of Monsoon and Large Amplitude Internal Waves on Coral Reef Development in the Andaman Sea

The Andaman Sea and other macrotidal semi-enclosed tropical seas feature large amplitude internal waves (LAIW). Although LAIW induce strong fluctuations i.e. of temperature, pH, and nutrients, their influence on reef development is so far unknown. A better-known source of disturbance is the monsoon affecting corals due to turbulent mixing and sedimentation. Because in the Andaman Sea both, LAIW and monsoon, act from the same westerly direction their relative contribution to reef development is difficult to discern. Here, we explore the framework development in a number of offshore island locations subjected to differential LAIW- and SW-monsoon impact to address this open question. Cumulative negative temperature anomalies – a proxy for LAIW impact – explained a higher percentage of the variability in coral reef framework height, than sedimentation rates which resulted mainly from the monsoon. Temperature anomalies and sediment grain size provided the best correlation with framework height suggesting that so far neglected subsurface processes (LAIW) play a significant role in shaping coral reefs.     

Ten-a Affects the Fusion of Central Complex Primordia in Drosophila

The central complex of Drosophila melanogaster plays important functions in various behaviors, such as visual and olfactory memory, visual orientation, sleep, and movement control. However little is known about the genes regulating the development of the central complex. Here we report that a mutant gene affecting central complex morphology, cbd (central brain defect), was mapped to ten-a, a type II trans-membrane protein coding gene. Down-regulation of ten-a in pan-neural cells contributed to abnormal morphology of central complex. Over-expression of ten-a by C767-Gal4 was able to partially restore the abnormal central complex morphology in the cbd mutant. Tracking the development of FB primordia revealed that C767-Gal4 labeled interhemispheric junction that separated fan-shaped body precursors at larval stage withdrew to allow the fusion of the precursors. While the C767-Gal4 labeled structure did not withdraw properly and detached from FB primordia, the two fan-shaped body precursors failed to fuse in the cbd mutant. We propose that the withdrawal of C767-Gal4 labeled structure is related to the formation of the fan-shaped body. Our result revealed the function of ten-a in central brain development, and possible cellular mechanism underlying Drosophila fan-shaped body formation.     

Effect of Temperature on Growth, Development and Reproduction of Meloidogyne hapla in Lettuce

Temperature was an important factor in growth, development and reproduction of Meloidogyne hapla in lettuce. Growth, as measured by increase in diameter of females, was not appreciably different at the intermediate (21.1 C night and 26.7 C day) and high (26.7 C night and 32.2 C day) temperature regimes, but was considerably less at the low temperature regime (15.5 C night and 21.1 C day) than at the two higher temperature regimes. Second-stage female larvae developed into adults 14 days after inoculation at the high, 18 days at the intermediate and 34 days at the low temperature regime. Eggs were observed 20 days after inoculation at the high, 26 days at the intermediate and 54 days at the low temperature regime. Number of eggs and larvae after 6 weeks was greater at the high than at the intermediate temperature regime and no eggs or larvae occurred at the low temperature regime during the observed 6 weeks.