Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
• Data Files
• Related Publications
• Parameters
• Project Information
• Funding

This dataset represents information from a meta-analysis of primary producer amino acid δ¹⁵N data that were published in Ramirez et al. (2021) [https://doi.org/10.1111/2041-210X.13678].  

This meta-analysis fulfills a pressing need to comprehensively evaluate relevant sources of β value variability and its contribution to the uncertainty in trophic position compound specific isotope analysis (TPCSIA). We first synthesized all published primary producer AA δ15N data to investigate ecologically relevant sources of variability (e.g. taxonomy, tissue type, habitat type, mode of photosynthesis). We then reviewed the biogeochemical mechanisms underpinning AA δ15N and β value variability. 

Amino acids: alanine ,arginine, aspartic acid, glutamic acid, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tyrosine, and valine

Environmental system: bacteria, freshwater, marine, or terrestrial

Vascularization: vascular, or non-vascular

Phylum/Division: Brypohyta, Chlorophyta, Cyanophyta, Euryarchaeota, Haptophyta, Magnoliophyta, Myzozoa, Ochrophyta, Pinophyta, Polypodiophyta, Proteobacteria, Rhodophyta, or Unknown

Stem Class: herbaceous, woody, or semi-woody

Life Cycle: annual, biennial, or perennial

Taxonomic Group: Cactus, Chemoautotroph, Cyanobacteria, Eukaryotic microalgae, Fern, Forb, Grass, Ice algae, Leaf litter, Macroalgae, Macrophyte, Moss, POM, Seagrass, Shrub, Tree, or Vine

Respiration type: C3, C4, or CAM (Crassulacean acid metabolism)

Tissue type: flower, fruit, leaf, paddle, rachis, seed, shoot, whole, or wood

Cultivation type: culture, farm, filtered water, natural, sediment trap, or suburb

Literature Review Methods

We performed a structured literature search for primary producer amino acid (AA) δ¹⁵N data in Scopus and Google Scholar using the search terms nitrogen isotope OR 15N AND amino acid with each of the terms plant, *plankton, algae, bacteria, and autotroph. We also used the search terms trophic, diet, and food web to identify all studies that estimated trophic position via compound-specific stable isotope analysis (TP_CSIA) or that estimated AA-specific trophic discrimination factors (TDFs). We only included studies that reported natural abundance stable isotope data. The literature search yielded 15 studies that reported beta values (β) for individual primary producers, 44 studies that reported TDFs or paired consumer-diet data within a trophic ecology context (e.g., controlled feeding study designed to characterize AA fractionation), and 176 studies that applied the TP_CSIA equation (Figure 2 from Ramirez et al. 2021). The literature search yielded an additional 36 studies that reported AA δ¹⁵N data for autotrophs from which β values could be calculated and 9 additional studies from which TDFs could be calculated. The unit of replication for this meta-analysis was species-specific tissue within study. Therefore, if a study had multiple β values for a single primary producer species, a simple mean and standard deviation were calculated to consolidate the reported data into one estimate per species per study. Tissue-specific data were maintained separately whenever reported. This process resulted in a final dataset that consisted of 236 β values across ≥ 132 different primary producer genera in freshwater, marine, and terrestrial ecosystems (Table 1, Figure 3 in Ramirez et al. 2021). Our meta-analysis focused primarily on β values derived from Glx and Phe (β_Glx-Phe) given that they are the most commonly measured trophic and source AAs and applied to estimate TP_CSIA. However, we present β values for all combinations of trophic (Asx, Ala, Ile, Leu, Pro, Val) and source (Phe, Lys, Met, Tyr) AAs in Table 2 and Figures S1 (Ramirez et al. 2021).  We also calculated β values for the “metabolic” AA Thr relative to the source AAs given its unique isotope dynamics with trophic transfer (McMahon & McCarthy, 2016). Primary producer Met and Tyr δ¹⁵N data were not routinely collected nor reported, therefore inferences were limited for these AAs.

A list of the publications is found in the Publications section below, and also in Ramirez et al. (2021).

NSF Award Abstract:
Changes in ocean life, the environment, and the climate can influence the timing and composition of biological material that sinks to the sea floor. As this material sinks it is consumed by bottom-dwelling organisms such as deep-sea corals. Similar to tree rings, corals preserve a history of growth embedded in their skeletons, which can be analyzed using a new technique called microgeochemistry. This project is compiling a historic dataset from deep-sea corals spanning 50 years in the Gulf of Maine to understand how biological material sinking to the bottom has changed with time. Results from the coral analysis are being compared with archival samples of small planktonic crustaceans, copepods, to better understand the connection between productivity in the surface waters and the geochemical record in the coral tissue. A complementary modeling approach is identifying environmental and climatic drivers of decadal-scale oceanographic change with the sources and transformations of organic matter that connect the surface and the deep ocean. This cross-disciplinary project is unifying transformational research with broader impacts focused on science education and outreach that broaden the understanding of the links between climate, oceanography, and marine ecosystem response using a 50-year historical context. Two open-access, media-enhanced, and National curriculum standards-aligned educational lessons plans are being developed through partnerships with a science documentary filmmaker, K-12 teachers from RI and ME, and the PBS LearningMedia Program. The topics of these lesson plans are: 1) Deep-sea exploration: A window into the past and future, and 2) Changing food webs on a changing planet. The project's educational goals include training of three graduate students, career development of five early career researchers, and research experiences for undergraduates from underrepresented groups in STEM. The multi-faceted research and education effort is addressing a question described as highest priority in the Ocean Sciences by the National Research Council: How are ocean biogeochemical and physical processes linked to today's climate and its variability?

Pelagic-benthic coupling regulates ocean production and food web dynamics, biogeochemical cycling, and climate feedback mechanisms through the export of surface production to the ocean interior. Yet access to long-term data sets of export production are scarce and urgently needed to test assumptions about 1) the sources and transformations of organic matter through different food web pathways, and 2) the variability of these processes across climatic, oceanographic, and ecological changes through time. The proposed work is testing key hypotheses about bottom-up mechanisms that link decadal-scale oceanographic changes in hydrography and biogeochemical cycling with phytoplankton community composition, zooplankton abundance and trophic dynamics, and the resulting composition of export production. Complementary approaches are generating multiple and independent 50+ year, annually resolved time series of phytoplankton community composition, zooplankton trophic dynamics, and export composition. Coral tissue and archived zooplankton samples are being analyzed using pioneering molecular geochemistry approaches to assess changes in diet related variation in primary production. Deep-sea corals are being collected using a remotely operated vehicle (ROV), and zooplankton are available through archival samples from a Gulf of Maine long-term monitoring program managed by NOAA. The stable isotope data are being integrated with additional data from existing long-standing ocean monitoring programs and incorporated into a unifying modeling approach to identify unique ecosystem states and their environmental drivers. The project is focused on Jordan Basin in the Gulf of Maine, which has a long history of oceanographic study and is experiencing significant changes due to climate warming, making it an ideal natural laboratory for testing hypotheses on drivers of change in the composition of exported organic matter, and the relative importance of primary (e.g., phyto-detritus) vs. secondary production (e.g., copepod fecal pellets), and large vs. small pelagic plankton dynamics.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.