DOC concentrations across a depth-dependent light gradient on a Caribbean coral reef

The dissolved organic carbon (DOC) pool on tropical coral reefs is mainly fueled by photosynthates released from benthic primary producers (BPP), such as reef algae and scleractinian corals. DOC concentrations near BPP have repeatedly been observed to be elevated compared to those in the surrounding water column. As the DOC release of BPP increases with increasing light availability, elevated DOC concentrations near them will, in part, also depend on light availability. Consequently, DOC concentrations are likely to be higher on the shallow, well-lit reef terrace than in deeper sections on the fore reef slope. We measured in situ DOC concentrations and light intensity in close proximity to the reef alga Dictyota sp. and the scleractinian coral Orbicella faveolata along a depth gradient from 5 to 20 m depth and compared these to background concentrations in the water column. DOC concentrations near Dictyota sp. were significantly higher at 10 m than at 5 and 20 m depth. Furthermore, at 10 m DOC concentrations near Dictyota sp. were elevated by 15 µmol C L-1 compared to background concentrations in the water column, but not at 5 and 20 m. DOC concentrations near O. faveolata and in the water column did not differ between depths and concentrations near O. faveolata were not elevated compared to background concentrations at any of the tested depths. Our results indicate that DOC concentrations near Dictyota sp. can differ along a depth gradient from 5 to 20 m. However, the occurrence of elevated DOC concentrations did not follow a natural light gradient across depth. Instead, a combination of light availability (including a restriction by photoinhibition) and water movement are proposed to interactively determine the DOC concentrations in the close vicinity of BPP across the reef slope.

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DOC concentrations across a depth gradient on a Caribbean coral reef

10.7287/peerj.preprints.2610v1 ◽

2016 ◽

Author(s):

Benjamin Mueller ◽

Erik H Meesters ◽

Fleur C van Duyl

Keyword(s):

Water Column ◽

Water Movement ◽

Light Availability ◽

Reef Slope ◽

Depth Gradient ◽

Background Concentrations ◽

Surrounding Water ◽

Light Gradient ◽

Close Proximity ◽

Caribbean Coral Reef

The dissolved organic carbon (DOC) pool on tropical coral reefs is mainly fueled by photosynthates released from benthic primary producers (BPP), such as reef algae and scleractinian corals. DOC concentrations near BPP have repeatedly been observed to be elevated compared to those in the surrounding water column. As the DOC release of BPP increases with increasing light availability, elevated DOC concentrations near them will, in part, also depend on light availability. Consequently, DOC concentrations are likely to be higher on the shallow, well-lit reef terrace than in deeper sections on the fore reef slope. We measured in situ DOC concentrations and light intensity in close proximity to the reef alga Dictyota sp. and the scleractinian coral Orbicella faveolata along a depth gradient from 5 to 20 m depth and compared these to background concentrations in the water column. DOC concentrations near Dictyota sp. were significantly higher at 10 m than at 5 and 20 m depth. Furthermore, at 10 m DOC concentrations near Dictyota sp. were elevated by 15 µmol C L-1 compared to background concentrations in the water column, but not at 5 and 20 m. DOC concentrations near O. faveolata and in the water column did not differ between depths and concentrations near O. faveolata were not elevated compared to background concentrations at any of the tested depths. Our results indicate that DOC concentrations near Dictyota sp. can differ along a depth gradient from 5 to 20 m. However, the occurrence of elevated DOC concentrations did not follow a natural light gradient across depth. Instead, a combination of light availability (including a restriction by photoinhibition) and water movement are proposed to interactively determine the DOC concentrations in the close vicinity of BPP across the reef slope.

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Water Column Optical Properties of Pacific Coral Reefs Across Geomorphic Zones and in Comparison to Offshore Waters

Remote Sensing ◽

10.3390/rs11151757 ◽

2019 ◽

Vol 11 (15) ◽

pp. 1757 ◽

Cited By ~ 5

Author(s):

Russell ◽

Dierssen ◽

Hochberg

Keyword(s):

Optical Properties ◽

Coral Reefs ◽

Water Column ◽

Light Availability ◽

Optical Measurements ◽

Fringing Reefs ◽

Tropical Conditions ◽

Local Measurements ◽

High Degree ◽

Significant Underestimation

Despite the traditional view of coral reefs occurring in oligotrophic tropical conditions, water optical properties over coral reefs differ substantially from nearby clear oceanic waters. Through an extensive set of optical measurements across the tropical Pacific, our results suggest that coral reefs themselves exert a high degree of influence over water column optics, primarily through release of colored dissolved organic matter (CDOM). The relative contributions of phytoplankton, non-algal particles, and CDOM were estimated from measurements of absorption and scattering across different geomorphic shallow-water reef zones (<10 m) in Hawaii, the Great Barrier Reef, Guam, and Palau (n = 172). Absorption was dominated at the majority of stations by CDOM, with mixtures of phytoplankton and CDOM more prevalent at the protected back reef and lagoon zones. Absorption could be dominated by sediments and phytoplankton at fringing reefs and terrestrially impacted sites where particulate backscattering was significantly higher than in the other zones. Scattering at three angles in the backward direction followed recent measurements of the particulate phase function. Optical properties derived from satellite imagery indicate that offshore waters are consistently lower in absorption and backscattering than reef waters. Therefore, the use of satellite-derived offshore parameters in modeling reef optics could lead to significant underestimation of absorption and scattering, and overestimation of benthic light availability. If local measurements are not available, average optical properties based on the general reef zone could provide a more accurate means of assessing light conditions on coral reefs than using offshore water as a proxy.

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DOWNWELLING DIFFUSE ATTENUATION COEFFICIENTS FROM IN SITU MEASUREMENTS OF DIFFERENT WATER TYPES

International Journal of Remote Sensing and Earth Sciences (IJReSES) ◽

10.30536/j.ijreses.2013.v10.a1851 ◽

2014 ◽

Vol 10 (2) ◽

Author(s):

Bisman Nababan ◽

Veronica S.A. Louhenapessy ◽

Risti E Arhatin

Keyword(s):

Water Column ◽

Coastal Region ◽

Euphotic Zone ◽

Time Range ◽

Water Type ◽

Attenuation Coefficients ◽

Water Types ◽

Light Reduction ◽

Ocean Ecosystem

Process of light reduction or loss (attenuation) by scattering and absorption is affected bysolar zenith, time, depth, and seawater constituents. Downwelling diffuse attenuation coefficient (Kd)is important to understand for light penetration and biological processes in ocean ecosystem. It is,therefore, important to know the Kd value and its variability in ocean ecosystem. The objective of thisstudy was to determine downwelling diffuse attenuation coefficients and its variability form in situmeasurements of different water types. In situ downwelling irradiances (Ed) were measured using asubmersible marine environmental radiometer instrument (MER) during a clear sky, calm watercondition, and at the time range of 10:30 a.m. up to 14:00 p.m. local time in the northeastern Gulf ofMexico in April 2000. In general, Ed values decreases exponentially with depth. Ed at 380 nmexhibited the lowest attenuation (the most penetrative light), while Ed at 683 nm exhibited the highestattenuation (the most light loss at the top of water column). Overall, the Kd patterns tended to decreasefrom 380 nm to 490 nm (blue-green wavelength), and increase from 490 nm to 683 nm (green-redwavelength). Kd values in offshore region were relatively lower than in coastal region. Kd can be usedto determine the depth of euphotic zone in offshore or teh case-1 water type and the depth of oneoptical depth (the water column depth where the ocean color satellite can possibly sense).

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Short-term fate of intertidal microphytobenthos carbon under enhanced nutrient availability: a <sup>13</sup>C pulse-chase experiment

Biogeosciences ◽

10.5194/bg-15-2873-2018 ◽

2018 ◽

Vol 15 (9) ◽

pp. 2873-2889 ◽

Cited By ~ 4

Author(s):

Philip M. Riekenberg ◽

Joanne M. Oakes ◽

Bradley D. Eyre

Keyword(s):

Water Column ◽

Nutrient Availability ◽

Nutrient Enrichment ◽

Extracellular Enzymes ◽

Turnover Time ◽

Ex Situ ◽

Nutrient Concentrations ◽

Organic C ◽

Storage Products

Abstract. Shallow coastal waters in many regions are subject to nutrient enrichment. Microphytobenthos (MPB) can account for much of the carbon (C) fixation in these environments, depending on the depth of the water column, but the effect of enhanced nutrient availability on the processing and fate of MPB-derived C (MPB-C) is relatively unknown. In this study, MPB was labeled (stable isotope enrichment) in situ using 13C-sodium bicarbonate. The processing and fate of the newly fixed MPB-C was then traced using ex situ incubations over 3.5 days under different concentrations of nutrients (NH4+ and PO43-: ambient, 2× ambient, 5× ambient, and 10× ambient). After 3.5 days, sediments incubated with increased nutrient concentrations (amended treatments) had increased loss of 13C from sediment organic matter (OM) as a portion of initial uptake (95 % remaining in ambient vs. 79–93 % for amended treatments) and less 13C in MPB (52 % ambient, 26–49 % amended), most likely reflecting increased turnover of MPB-derived C supporting increased production of extracellular enzymes and storage products. Loss of MPB-derived C to the water column via dissolved organic C (DOC) was minimal regardless of treatment (0.4–0.6 %). Loss due to respiration was more substantial, with effluxes of dissolved inorganic C (DIC) increasing with additional nutrient availability (4 % ambient, 6.6–19.8 % amended). These shifts resulted in a decreased turnover time for algal C (419 days ambient, 134–199 days amended). This suggests that nutrient enrichment of estuaries may ultimately lead to decreased retention of carbon within MPB-dominated sediments.

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Short-term fate of intertidal microphytobenthos carbon under enhanced nutrient availability: A <sup>13</sup>C pulse-chase experiment

10.5194/bg-2017-448 ◽

2017 ◽

Author(s):

Philip M. Riekenberg ◽

Joanne M. Oakes ◽

Bradley D. Eyre

Keyword(s):

Water Column ◽

Nutrient Availability ◽

Extracellular Enzymes ◽

Turnover Time ◽

Ex Situ ◽

Nutrient Concentrations ◽

Organic C ◽

Storage Products ◽

And Storage

Abstract. Shallow coastal waters in many regions are subject to nutrient over-enrichment. Microphytobenthos (MPB) can account for much of the carbon (C) fixation in these environments, depending on the depth of the water column, but the effect of enhanced nutrient availability on the processing and fate of MPB-derived C is relatively unknown. In this study, MPB were labeled (stable isotope enrichment) in situ using 13C-sodium bicarbonate. The processing and fate of the newly-fixed MPB-C was then traced using ex situ incubations over 3.5 d under different concentrations of nutrients (NH4+ and PO43−: ambient, 2× ambient, 5× ambient, and 10× ambient). After 3.5 d, sediments incubated with increased nutrient concentrations (amended treatments) had increased loss of 13C from sediment organic matter as a portion of initial uptake (95 % remaining in ambient vs 79–93 % for amended treatments) and less 13C in MPB (52 % ambient, 26–49 % amended), most likely reflecting increased turnover of MPB-derived C supporting increased production of extracellular enzymes and storage products. Loss of MPB-derived C to the water column via dissolved organic C was minimal regardless of treatment (0.4–0.6 %). Loss due to respiration was more substantial, with effluxes of dissolved inorganic C increasing with additional nutrient availability (4 % ambient, 6.6–19.8 % amended). These shifts resulted in a decreased turnover time for algal C (419 d ambient, 134–199 d amended). This suggests that nutrient enrichment of estuaries may ultimately lead to decreased retention of carbon within MPB-dominated sediments.

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Investigation of copper nanoscale electro-crystallization under directed and non-directed electrodeposition from dilute electrolytes

CrystEngComm ◽

10.1039/d1ce00143d ◽

2021 ◽

Author(s):

Mark Aarts ◽

Stefan van Vliet ◽

Roland Bliem ◽

Esther Alarcon-Llado

Keyword(s):

Atomic Force Microscopy ◽

Crystal Growth ◽

Ex Situ ◽

Gold Substrate ◽

Force Microscopy ◽

Atomic Force ◽

Close Proximity

In situ and ex situ atomic force microscopy was used to investigate crystal growth in copper electro-crystallization localized and directed by a moving nanoelectrode in close proximity to a gold substrate in a highly dilute electrolyte.

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Novel Herpesvirus Associated With Oropharyngeal Squamous Cell Carcinoma in Smooth Green Snakes (Opheodrys vernalis)

Veterinary Pathology ◽

10.1177/0300985819837722 ◽

2019 ◽

Vol 56 (4) ◽

pp. 630-635

Author(s):

Jessica N. Lovstad ◽

Robert J. Ossiboff ◽

Michael J. Kinsel ◽

Kathryn C. Gamble

Keyword(s):

Squamous Cell Carcinoma ◽

In Situ Hybridization ◽

Cell Carcinoma ◽

Squamous Cell ◽

Conventional Polymerase Chain Reaction ◽

Oropharyngeal Squamous Cell Carcinoma ◽

Ex Situ ◽

Neoplastic Tissue ◽

Close Proximity

During a 19-month period, 5 smooth green snakes ( Opheodrys vernalis) maintained as an ex situ conservation colony presented with rapid clinical progression of locally invasive oropharyngeal squamous cell carcinoma. All 5 originated from the same wild source and were housed together or in close proximity. An infectious cause was considered likely, and nested conventional polymerase chain reaction (PCR) and in situ hybridization confirmed the presence of a novel alphaherpesvirus, Opheodrys herpesvirus 1, in the neoplastic tissue in 4 of the 5 snakes. Retrospective screening of previously submitted smooth green snakes by in situ hybridization did not detect virus in prior submissions from the colony. This report documents molecular characterization of an ophidian herpesvirus as well as colocalization of its viral nucleic acid with neoplastic transformation in snakes.

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An in situ and ex situ TEM study of the formation of thin cobalt silicide films by molecular beam epitaxy on the silicon (100) surface

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010010648x ◽

1988 ◽

Vol 46 ◽

pp. 884-885

Author(s):

D. Loretto ◽

J. M. Gibson ◽

S. M. Yalisove ◽

R. T. Tung

Keyword(s):

Molecular Beam Epitaxy ◽

Molecular Beam ◽

Defect Density ◽

High Vacuum ◽

Ultra High Vacuum ◽

Ex Situ ◽

Metal Base ◽

In Situ Experiments ◽

Potential Applications

The cobalt disilicide/silicon system has potential applications as a metal-base and as a permeable-base transistor. Although thin, low defect density, films of CoSi2 on Si(111) have been successfully grown, there are reasons to believe that Si(100)/CoSi2 may be better suited to the transmission of electrons at the silicon/silicide interface than Si(111)/CoSi2. A TEM study of the formation of CoSi2 on Si(100) is therefore being conducted. We have previously reported TEM observations on Si(111)/CoSi2 grown both in situ, in an ultra high vacuum (UHV) TEM and ex situ, in a conventional Molecular Beam Epitaxy system.The procedures used for the MBE growth have been described elsewhere. In situ experiments were performed in a JEOL 200CX electron microscope, extensively modified to give a vacuum of better than 10-9 T in the specimen region and the capacity to do in situ sample heating and deposition. Cobalt was deposited onto clean Si(100) samples by thermal evaporation from cobalt-coated Ta filaments.

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The use of transmission and analytical electron microscopy in studying reactions and phase transformations in thin film

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100150046 ◽

1993 ◽

Vol 51 ◽

pp. 842-843

Author(s):

K. Barmak

Keyword(s):

Thin Film ◽

Thin Films ◽

Phase Transformations ◽

Analytical Electron Microscopy ◽

Ex Situ ◽

Multilayer Thin Films ◽

Absolute Concentration ◽

Analytical Electron ◽

Deposition Step

Generally, processing of thin films involves several annealing steps in addition to the deposition step. During the annealing steps, diffusion, transformations and reactions take place. In this paper, examples of the use of TEM and AEM for ex situ and in situ studies of reactions and phase transformations in thin films will be presented.The ex situ studies were carried out on Nb/Al multilayer thin films annealed to different stages of reaction. Figure 1 shows a multilayer with dNb = 383 and dAl = 117 nm annealed at 750°C for 4 hours. As can be seen in the micrograph, there are four phases, Nb/Nb3-xAl/Nb2-xAl/NbAl3, present in the film at this stage of the reaction. The composition of each of the four regions marked 1-4 was obtained by EDX analysis. The absolute concentration in each region could not be determined due to the lack of thickness and geometry parameters that were required to make the necessary absorption and fluorescence corrections.

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