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.
Thank you to the Nissei Foundation for their support.
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.
↓↓ Check out Facebook for some images from our latest survey at Dongsha Atoll, South China Sea. Image above shows the very high soft coral cover on the atoll’s eastern reef terrace ↑↑
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.
Amino acid and radiocarbon insights from captive whale sharks
Alex S.J. WYATT1*, Rui Matsumoto2, Yoshito Chikaraishi3, Yosuke Miyari1, Yusuke Yokoyama1, Keiichi Sato2, Nao Ohkouchi3, Toshi Nagata1
1Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba, JAPAN
2Okinawa Churaumi Aquarium, Motobu, Okinawa, JAPAN
3Japan Agency for Marine-Earth Science and Technology, Yokosuka, JAPAN
Stable isotope analyses (SIA) have the potential to provide novel insights into spatial and temporal patterns in the trophic ecology of poorly understood organisms like whale sharks Rhincodon typus. However, interpreting SIA depends on accurate diet-tissue discrimination factors (DTDF) to quantify diets and trophic positions, with experimental derivations of DTDF rare for such large-bodied organisms. Captive R. typus have provided a unique opportunity to validate a range of SIA, compound-specific isotope analyses (CSIA) and radioisotope approaches in the world’s largest fish and one of three planktivorous sharks. Diet records over the past five years revealed a diet dominated by North Pacific and Antarctic krill, 44% and 49% of weighted diet for Euphausia pacifica and E. superba, respectively. Despite the well-known diet, SIA of fin tissue from three captive R. typus (7.1, 7.2, and 8.4 m in length) proved hard to reconcile, especially for bulk carbon. In contrast, CSIA of amino acid (AA) nitrogen in the sharks’ tissue was relatively stable over time, despite evidence of variation in AA compositions and δ15N-AA of diet components. Tissue radiocarbon further suggested either long turnover in fin tissues (27 months), or the preferential assimilation of the smaller E. pacifica (Δ14C of 3 ‰ compared to -112 ‰ for E. superba). Daily-scale analysis of radiocarbon in R. typus faeces may support the preferential assimilation hypothesis, faeces generally being depleted relative to diet. Together, CSIA-AA and radiocarbon analyses add multiple addtional axes to our isotope space and may alleviate some of the complications involved in interpreting bulk SIA in ecological studies.
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.