The influence of diet on the distribution of nitrogen isotopes in animals was investigated by analyzing animals grown in the laboratory on diets of constant nitrogen isotopic composition. 
The isotopic composition of the nitrogen in an animal reflects the nitrogen isotopic composition of its diet. The δ^(15)N values of the whole bodies of animals are usually more positive than those of their diets. Different individuals of a species raised on the same diet can have significantly different δ^(15)N values. The variability of the relationship between the δ^(15)N values of animals and their diets is greater for different species raised on the same diet than for the same species raised on different diets. Different tissues of mice are also enriched in ^(15)N relative to the diet, with the difference between the δ^(15)N values of a tissue and the diet depending on both the kind of tissue and the diet involved. The δ^(15)N values of collagen and chitin, biochemical components that are often preserved in fossil animal remains, are also related to the δ^(15)N value of the diet. 
The dependence of the δ^(15)N values of whole animals and their tissues and biochemical components on the δ^(15)N value of diet indicates that the isotopic composition of animal nitrogen can be used to obtain information about an animal's diet if its potential food sources had different δ^(15)N values. The nitrogen isotopic method of dietary analysis probably can be used to estimate the relative use of legumes vs non-legumes or of aquatic vs terrestrial organisms as food sources for extant and fossil animals. However, the method probably will not be applicable in those modern ecosystems in which the use of chemical fertilizers has influenced the distribution of nitrogen isotopes in food sources. 
The isotopic method of dietary analysis was used to reconstruct changes in the diet of the human population that occupied the Tehuacan Valley of Mexico over a 7000 yr span. Variations in the δ^(15)C and δ^(15)N values of bone collagen suggest that C_4 and/or CAM plants (presumably mostly corn) and legumes (presumably mostly beans) were introduced into the diet much earlier than suggested by conventional archaeological analysis.

Influence of Diet On the Distribtion of Nitrogen Isotopes in Animals

Food in the Anthropocene: the EAT–Lancet Commission on healthy diets from sustainable food systems

Today's surface ocean is saturated with respect to calcium carbonate, but increasing atmospheric carbon dioxide concentrations are reducing ocean pH and carbonate ion concentrations, and thus the level of calcium carbonate saturation. Experimental evidence suggests that if these trends continue, key marine organisms—such as corals and some plankton—will have difficulty maintaining their external calcium carbonate skeletons. Here we use 13 models of the ocean–carbon cycle to assess calcium carbonate saturation under the IS92a 'business-as-usual' scenario for future emissions of anthropogenic carbon dioxide. In our projections, Southern Ocean surface waters will begin to become undersaturated with respect to aragonite, a metastable form of calcium carbonate, by the year 2050. By 2100, this undersaturation could extend throughout the entire Southern Ocean and into the subarctic Pacific Ocean. When live pteropods were exposed to our predicted level of undersaturation during a two-day shipboard experiment, their aragonite shells showed notable dissolution. Our findings indicate that conditions detrimental to high-latitude ecosystems could develop within decades, not centuries as suggested previously.

/pdf/anthropogenic-ocean-acidification-over-the-twenty-first-p8m4yiib3x.pdf

Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms

Using inorganic carbon measurements from an international survey effort in the 1990s and a tracer-based separation technique, we estimate a global oceanic anthropogenic carbon dioxide (CO2) sink for the period from 1800 to 1994 of 118 19 petagrams of carbon. The oceanic sink accounts for48% of the total fossil-fuel and cement-manufacturing emissions, implying that the terrestrial biosphere was a net source of CO 2 to the atmosphere of about 39 28 petagrams of carbon for this period. The current fraction of total anthropogenic CO2 emissions stored in the ocean appears to be about one-third of the long-term potential. Since the beginning of the industrial period in the late 18th century, i.e., over the anthropocene (1), humankind has emitted large quantities of CO2 into the atmosphere, mainly as a result of fossil-fuel burning, but also because of land-use practices, e.g., deforestation (2). Measurements and reconstructions of the atmospheric CO2 history reveal, however, that less than half of these emissions remain in the atmosphere (3). The anthropogenic CO2 that did not accumulate in the atmosphere must have been taken up by the ocean, by the land biosphere, or by a combination of both. The relative roles of the ocean and land biosphere as sinks for anthropogenic CO2 over the anthropocene are currently not known. Although the anthropogenic CO2 budget for the past two decades, i.e., the 1980s and 1990s, has been investigated in detail (3), the estimates of the ocean sink have not been based on direct measurements of changes in the oceanic inventory of dissolved inorganic carbon (DIC). Recognizing the need to constrain the oceanic uptake, transport, and storage of anthropogenic CO 2 for the anthropocene and to provide a baseline for future estimates of oceanic CO 2 uptake, two international ocean research programs, the World Ocean Circulation Experiment (WOCE) and the Joint Global Ocean Flux Study (JGOFS), jointly conducted a comprehensive survey of inorganic carbon distributions in the global ocean in the 1990s (4). After completion of the U.S. field program in 1998, a 5-year effort was begun to compile and rigorously quality-control the U.S. and international data sets, in

/pdf/the-oceanic-sink-for-anthropogenic-co2-480zoye29p.pdf

The oceanic sink for anthropogenic CO2.

Rising atmospheric carbon dioxide (CO2), primarily from human fossil fuel combustion, reduces ocean pH and causes wholesale shifts in seawater carbonate chemistry. The process of ocean acidification is well documented in field data, and the rate will accelerate over this century unless future CO2 emissions are curbed dramatically. Acidification alters seawater chemical speciation and biogeochemical cycles of many elements and compounds. One well-known effect is the lowering of calcium carbonate saturation states, which impacts shell-forming marine organisms from plankton to benthic molluscs, echinoderms, and corals. Many calcifying species exhibit reduced calcification and growth rates in laboratory experiments under high-CO2 conditions. Ocean acidification also causes an increase in carbon fixation rates in some photosynthetic organisms (both calcifying and noncalcifying). The potential for marine organisms to adapt to increasing CO2 and broader implications for ocean ecosystems are not well known; both are high priorities for future research. Although ocean pH has varied in the geological past, paleo-events may be only imperfect analogs to current conditions.

/pdf/ocean-acidification-the-other-co-2-problem-4h18mw2cpj.pdf

Ocean Acidification: The Other CO 2 Problem

Despite their moderately sized surface area, continental marginal seas play a significant role in the biogeochemical cycles of carbon, as they receive huge amounts of upwelled and riverine inputs of carbon and nutrients, sustaining a disproportionate large biological activity compared to their relative surface area. A synthesis of worldwide measurements of the partial pressure of CO2 (pCO2) indicates that most open shelves in the temperate and high-latitude regions are under-saturated with respect to atmospheric CO2 during all seasons, although the low-latitude shelves seem to be over-saturated. Most inner estuaries and near-shore coastal areas on the other hand are over-saturated with respect to atmospheric CO2. The scaling of air–sea CO2 fluxes based on pCO2 measurements and carbon massbalance calculations indicate that the continental shelves absorb atmospheric CO2 ranging between 0.33 and 0.36 Pg C yr � 1 that corresponds to an additional sink of 27% to � 30% of the CO2 uptake by the open oceans based on the most recent pCO2 climatology [Takahashi, T., Sutherland, S.C., Wanninkhof, R.,

/pdf/reconciling-opposing-views-on-carbon-cycling-in-the-coastal-5bovobaf0v.pdf

Reconciling opposing views on carbon cycling in the coastal ocean: Continental shelves as sinks and near-shore ecosystems as sources of atmospheric CO2

http://ir.yic.ac.cn/bitstream/133337/5607/1/Heavy%20metal%20pollution%20status%20in%20surface%20sediments.pdf

Heavy metal pollution status in surface sediments of the coastal Bohai Bay.

Chemical and physical fronts in the Bohai, Yellow and East China seas

The western part of the Kuroshio Intermediate Water originates from the nutrient-rich South China Sea intermediate water which upwells onto the East China Sea (ECS) continental shelf and contributes a large amount of nutrients to the ECS. This contribution, especially for phosphorus, is far more than the inputs from the phosphorus-deficient Yangtze and Yellow Rivers. Mass balance calculations reveal that the net denitrification rate in the ECS shelf is 95 ± 50 × 109 mol N yr−1, which is more than the total riverine supply of nitrogen. The nutrient supply allows the ECS to produce 1030 ± 310 × 109 moles dissolved organic carbon and 709 ± 280 × 109 mol particulate organic carbon for a total of 1739 ± 870 × 109 mol organic carbon per year, which translates to a new production rate of phytoplankton as 64 ± 32 mg C m−2 d−1 or 15% of the average primary production rate. The downslope transport of modern particulate carbon is 2547 ± 1250 × 109 mol yr−1, of which 695 ± 350 × 109 mol yr−1 is organic. This value is only 12% of the offshore dissolved organic carbon transport of 5563 ± 1700 × 109 mol yr−1. The alkalinity budget, never attempted before, indicates that there is a substantial amount of alkalinity generation in the sediments (3.9 ± 3.9 mmol m−2 d−1) due to anaerobic respiration such as by iron and sulfate reductions.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/1999JC900055

Chen-Tung Arthur Chen

Papers

Reconciling opposing views on carbon cycling in the coastal ocean: Continental shelves as sinks and near-shore ecosystems as sources of atmospheric CO2

Heavy metal pollution status in surface sediments of the coastal Bohai Bay.

Chemical and physical fronts in the Bohai, Yellow and East China seas

Carbon, alkalinity and nutrient budgets on the East China Sea continental shelf

Recent changes of water discharge and sediment load in the Zhujiang (Pearl River) Basin, China