Nissei Foundation grant to Dr Wyatt et al.

The Nissei Foundation has awarded Dr Wyatt and colleagues a Grant for Environmental Issues Research by Young Researchers, 環境問題研究助成 (若手研究):

Title: Elucidating jungle-to-reef connections using state-of-the-art chemical tracers: Towards harmony between human activities and the pristine environments of Iriomote-jima, Japan | 最先端化学トレーサーによる亜熱帯林とサンゴ礁生態系のつながりの 解明:西表島の貴重な自然の保全と人間活動の調和に向けて

Participants: Alex. S.J. Wyatt, Toshi Nagata, Yusuke Yokoyama, Toshihiro Miyajima, James Leichter (Scripps)

This grant will facilitate ongoing work examining ecological links between oceanic and terrestrial processes in the pristine coral reef ecosystems of the west coast of Iriomote-jima.  Preliminary isotope tracer work has demonstrated that corals may be strongly dependent  on ancient carbon exported from the forested catchment feeding into Funauki Bay, which suggests that reef habitats across the bay may depend on the preservation of the intact upstream sub-tropical forest.

More info:

Thank you to the Nissei Foundation for their support.


New paper on advances in amino acid nitrogen isotopic analysis (Ohkouchi et al., Organic Geochemsitry)

Advances in the application of amino acid nitrogen isotopic analysis in ecological and biogeochemical studies

Naohiko Ohkouchi1,*, Yoshito Chikaraishi1,13, Hilary G. Close2, Brian Fry3, Thomas Larsen4, Daniel J. Madigan5, Matthew D. McCarthy6, Kelton W. McMahon7, Toshi Nagata8, Yuichi I. Naito1,14, Nanako O. Ogawa1, Brian N. Popp9, Shawn Steffan10,11, Yoshinori Takano1, Ichiro Tayasu12, Alex S.J. Wyatt8, Yasuhiko T. Yamaguchi8,15, Yusuke Yokoyama8

1 Department of Biogeochemistry, Japan Agency for Marine-Earth Science and Technology, Japan; 2 Rosenstiel School of Marine and Atmospheric Science, University of Miami, USA3 Australian Rivers Institute, Griffith University, Australia; 4 Leibniz-Laboratory, University of Kiel, Germany; 5 Harvard University Center for the Environment, USA; 6 Department of Ocean Sciences, University of California, Santa Cruz, USA; 7 Graduate School of Oceanography, University of Rhode Island, USA; 8 Atmosphere and Ocean Research Institute, The University of Tokyo, Japan; 9 Department of Geology and Geophysics, University of Hawaii, USA; 10 US Department of Agriculture, Agricultural Research Service, USA; 11 Department of Entomology, University of Wisconsin-Madison, USA; 12 Research Institute of Humanity and Nature, Japan; 13 Present address: Institute of Low Temperature Science, Hokkaido University, Japan; 14 Present address: Nagoya University Museum, Japan; 15 Present address: Lake Biwa Environmental Research Institute, Japan

Compound-specific isotopic analysis of amino acids (CSIA-AA) has emerged in the last decade as a powerful approach for tracing the origins and fate of nitrogen in ecological and biogeochemical studies. This approach is based on the empirical observation that source amino acids (AAs) (i.e., phenylalanine), fractionate 15N very little (< 0.5‰) during trophic transfer, whereas trophic AAs (i.e., glutamic acid), are greatly (∼6–8‰) enriched in 15N during each trophic step. The differential fractionation of these two AA groups can provide a valuable estimate of consumer trophic position that is internally indexed to the baseline δ15N value of the integrated food web. In this paper, we critically review the analytical methods for determining the nitrogen isotopic composition of AAs by gas chromatography–isotope-ratio mass spectrometry. We also discuss methodological considerations for accurate trophic position assessment of organisms using CSIA-AA. We then discuss the advantages and challenges of the CSIA-AA approach using published case studies across a range of topics, including trophic position assessment in various ecosystems, reconstruction of ancient human diets, reconstruction of animal migration and environmental variability, and assessment of marine organic matter dynamics with new classification of microbial fractionation patterns. It is clear that the CSIA-AA approach can provide unique insight into the sources, cycling, and trophic modification of organic nitrogen as it flows through systems. However, this approach will be greatly improved through continued exploration into how biochemical, physiological, and ecological mechanisms affect isotopic fractionation of individual AAs. We end this review with a perspective on future work that will promote the evolution of the rapidly growing field of CSIA-AA.

Sumitomo Foundation grant to Dr Wyatt et al.

The Sumitomo Foundation has awarded an Environmenal Research Grant (環境研究助成) to Dr Wyatt and colleagues for their pioneering work on the environmental drivers of the structure and function of ‘twilight reefs’ (deep-water mesophotic coral ecosystems).

Title: A refuge for coral reef biodiversity: trophic function and reproduction in the twilight zone | 危機に瀕したサンゴ礁生物の避難場所:薄明帯の学際的解明による保全・再生の支援

Participants: Alex S.J. Wyatt, Toshihiro Miyajima, Toshi Nagata, James Leichter (Scripps), Satoshi Mitarai (OIST), Kazuhiko Sakai (U Ryukyu), Rob Toonen (U Hawaii).

More info:

Thank you to the Sumitomo Foundation for their support.


Impacts of internal waves on the twilight zone @ ICRS 2016, Hawaii (Dr Wyatt)

Ecological and biogeochemical impacts of internal waves on mesophotic coral ecosystems: testing eddy correlation and isotope approaches, Iriomote, Japan

Alex S.J. Wyatt1*, Toshihiro Miyajima1, James J. Leichter2, Tohru Naruse3, Tomohiro Kuwae4, Shoji Yamamoto5, Naomi Satoh1, Toshi Nagata1

1Department of Chemical Oceanography, Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba, JAPAN
2Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California, USA
3Tropical Biosphere Research Center, University of the Ryukyus, Taketomi, Japan
4Coastal and Estuarine Environment Research Group, Port and Airport Research Institute (PARI), Nagase, Yokosuka, JAPAN
5Department of Earth and Planetary Science, The University of Tokyo, Bunkyo-ku, Tokyo, Japan

While mesophotic coral ecosystems (MCE) may be protected or damped from disturbances impacting shallower reefs insufficient information is available on the environmental conditions supporting these ‘deep water refugia’. Nutrient inputs and recycling have rarely been quantified over MCE but may differ fundamentally to that of shallow counterparts due to the reduction in light and increasing reliance on oceanic nutrients, leading to increased heterotrophy over autotrophy at species and ecosystem levels and stronger links to oceanic processes. For instance, due to the depth of MCE relative to typical water column density stratification, internal waves may be a highly significant process depending on community aspect and exposure. Preliminary observations of MCE along a continuum of oceanic exposure in Funauki Bay, Iriomote, Japan indicate that ocean-exposed MCE are subject to semi-diurnal temperature oscillations of up to 4 C during summer (range 23 – 29 deg C), while inner MCE occur shallower in more turbid but stable environments. Oceanic exposure along the bay may determine both the distribution and function of spatially extensive, but relatively homogenous, communities dominated by Leptoseris sp. or Acropora ?horrida. Combining bulk and compound-specific stable isotope analyses, depth-specific radioisotope markers such as radiocarbon, and eddy correlation experiments in these habitat promises a useful approach for elucidating the functional importance of internal waves in the development and persistence of MCE at local to regional scales.

Dongsha Atoll Research Award (2016-2017) to Dr Wyatt and Prof Wang

Dr Wyatt has been awarded the Dongsha Atoll Research Award (2016-2017) by the Dongsha Atoll Research Station (DARS), managed by Taiwan’s National Sun Yat-sen University (NSYU).  The award will facilitate the implementation of a collaborative project with Professor Yu-Huai Wang (NSYU) examining the impact of internal waves on the biochemistry and ecology of Dongsha’s reef communities, focusing on ‘twilight zone’ mesophotic coral ecosystems around the atoll.

Dr Wyatt is excited to begin examining the reefs around Dongsha Atoll, which experiences some of the most energetic internal wave activity on the planet, and collaborating with Professor Wang’s group and NSYU.  The support of the Dongsha Atoll Research Station is greatly appreciated.

Ecosystem inputs and recycling over coral reefs @ 3rd APCRS, 2014 (Dr Wyatt)

Functional understanding of ecosystem-scale inputs and recycling over coral reef communities from stable isotope analyses of organic matter

Alex S.J. Wyatt1*, James J. Leichter2, Benoit Thibodeau1, Toshihiro Miyajima1, Craig A. Carlson3, Craig E. Nelson4, Toshi Nagata1

1Marine Biogeochemistry Laboratory, Department of Chemical Oceanography, Atmosphere & Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba, JAPAN
2Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California, USA
3University of California at Santa Barbara, Santa Barbara, California, USA
4Center for Microbial Oceanography: Research and Education, University of Hawai’i, USA

Stable isotope analyses (SIA) are an increasingly useful tool for understanding functional links between water flow and nutrient cycling over coral reefs, including relative fluxes of oceanic and reef-derived material. SIA have suggested that oceanic particulate organic matter (POM) flowing over reefs can be rapidly metabolized, with the subsequent release of remineralized inorganic nutrients, as well reef-derived POM, representing a significant resource for downstream communities. High oceanic concentrations of dissolved organic matter (DOM) relative to POM suggests DOM may be an even more significant resource, especially around low-POM reefs such as mid-ocean islands and atolls. However, DOM fluxes have rarely been quantified, perhaps due to the refractory nature of oceanic DOM and difficulties linking small concentration changes with spatial changes in both hydrodynamics and macro- and microbial communities. Our Lagrangian studies of DOM around Moorea, French Polynesia and Ishigaki Island, Japan suggest that DOM changes occurring over short spatial scales reflect a balance between uptake and release. SIA further suggest that the release of reef-derived DOM (i.e. enriched in 13C), perhaps relatively labile and from nitrogen fixing organisms (i.e. depleted in 15N), may promote nutrient recycling and supply to downstream communities. Linking SIA and local hydrodynamics offers a promising path towards elucidating the relative functional importance of oceanic and reef-level processes for reef communities.

Key words: dissolved organic matter, fluxes, particulate organic matter, recycling, stable isotope analyses

Bio-physical interactions on a coral reef island (Leichter et al., Oceanography)

Biological and Physical Interactions on a Tropical Island Coral Reef: Transport and Retention Processes on Moorea, French Polynesia

Leichter, J.J., Alldredge, A.L., Bernadi, G., Brooks, A.J., Carlson, C.A., Carpenter, R.C., Edmunds, P.J., Fewings, M.R., Hanson, K.M., Holbrook, S.J., Hench, J.L., Nelson, C.E., Schmitt, R.J., Toonen, R.J., Washburn, L. and Wyatt, A.S.J.

The Moorea Coral Reef Long Term Ecological Research project funded by the US National Science Foundation includes multidisciplinary studies of physical processes driving ecological dynamics across the fringing reef, back reef, and fore reef habitats of Moorea, French Polynesia. A network of oceanographic moorings and a variety of other approaches have been used to investigate the biological and biogeochemical aspects of water transport and retention processes in this system. There is evidence to support the hypothesis that a low-frequency counterclockwise flow around the island is superimposed on the relatively strong alongshore currents on each side of the island. Despite the rapid flow and flushing of the back reef, waters over the reef display chemical and biological characteristics distinct from those offshore. The patterns include higher nutrient and lower dissolved organic carbon concentrations, distinct microbial community compositions among habitats, and reef assemblages of zooplankton that exhibit migration behavior, suggesting multigenerational residence on the reef. Zooplankton consumption by planktivorous fish on the reef reflects both retention of reef-associated taxa and capture by the reef community of resources originating offshore. Coral recruitment and population genetics of reef fishes point to retention of larvae within the system and high recruitment levels from local adult populations. The combined results suggest that a broad suite of physical and biological processes contribute to high retention of externally derived and locally produced organic materials within this island coral reef system.

Formation and maintenance of high-nitrate, low pH layers (Waite et al., Biogeosciences)

Formation and maintenance of high-nitrate, low pH layers in the eastern Indian Ocean and the role of nitrogen fixation

A. M. Waite, V. Rossi, M. Roughan, B. Tilbrook, P. A. Thompson, M. Feng, A. S. J. Wyatt, and E. J. Raes

We investigated the biogeochemistry of low dissolved oxygen high-nitrate (LDOHN) layers forming against the backdrop of several interleaving regional water masses in the eastern Indian Ocean, off northwest Australia adjacent to Ningaloo Reef. These water masses, including the forming Leeuwin Current, have been shown directly to impact the ecological function of Ningaloo Reef and other iconic coastal habitats downstream. Our results indicate that LDOHN layers are formed from multiple subduction events of the Eastern Gyral Current beneath the Leeuwin Current (LC); the LC originates from both the Indonesian Throughflow and tropical Indian Ocean. Density differences of up to 0.025 kg m−3 between the Eastern Gyral Current and the Leeuwin Current produce sharp gradients that can trap high concentrations of particles (measured as low transmission) along the density interfaces. The oxidation of the trapped particulate matter results in local depletion of dissolved oxygen and regeneration of dissolved nitrate (nitrification). We document an associated increase in total dissolved carbon dioxide, which lowers the seawater pH by 0.04 units. Based on isotopic measurements (δ15N and δ18O) of dissolved nitrate, we determine that ~ 40–100% of the nitrate found in LDOHN layers is likely to originate from nitrogen fixation, and that, regionally, the importance of N-fixation in contributing to LDOHN layers is likely to be highest at the surface and offshore.