<p>Which has higher <span class="math-container">$\delta {}^{18} \text{O}$</span>, saline water or freshwater?
I searched for this question and found many researches about the relationship between <span class="math-container">$\delta {}^{18} \text{O}$</span> and salinity. But, I'm not sure why δ18O differs by salinity.
Some researches say that <span class="math-container">$\delta {}^{18} \text{O}$</span> is high in saline water and low in freshwater.</p>
<p>Why would <span class="math-container">$\delta {}^{18} \text{O}$</span> differs by salinity, especially of seawater and freshwater?</p>
<p>EDIT: I was just curious if I can determine whether a diadromous fish was anadromous or catadromous by examining <span class="math-container">$\delta {}^{18} \text{O}$</span> value of the fish fossil.</p>
<p>In <a href="https://www.nature.com/articles/s41598-021-03232-9#Fig2" rel="nofollow noreferrer">this</a> research, how can we know that the fish was anadromous by its <span class="math-container">$\delta {}^{18} \text{O}$</span> value?</p>

CC BY-SA 4.0
2022-01-14T17:58:52.087Z
It depends on what latitudes the fresh vs saline water samples are drawn from.
David Hammen
CC BY-SA 4.0
2022-01-14T21:31:36.583Z
Did you have a visit at NASA' Goddard Institute and the open access  [Global Seawater Oxygen-18 Database](https://data.giss.nasa.gov/o18data/)?
Buttonwood
CC BY-SA 4.0
2022-01-18T07:59:54.090Z
I found out that δ18O differs by salinity because of precipitation and evaporation. But I'm not sure if it can also be applied to δ18O difference between seawater and freshwater.
Kernel
<oxygen><salinity><isotopic>
Oxygen-18 in saline water and freshwater
Kernel
# Oxygen-18 in saline water and freshwater

(Asked by: username_0 on 2022-01-14)

Which has higher $\delta {}^{18} \text{O}$, saline water or freshwater?
I searched for this question and found many researches about the relationship between $\delta {}^{18} \text{O}$ and salinity. But, I'm not sure why δ18O differs by salinity.
Some researches say that $\delta {}^{18} \text{O}$ is high in saline water and low in freshwater.

Why would $\delta {}^{18} \text{O}$ differs by salinity, especially of seawater and freshwater?

EDIT: I was just curious if I can determine whether a diadromous fish was anadromous or catadromous by examining $\delta {}^{18} \text{O}$ value of the fish fossil.

In [this](https://www.nature.com/articles/s41598-021-03232-9#Fig2) research, how can we know that the fish was anadromous by its $\delta {}^{18} \text{O}$ value?

**Tags:** oxygen, salinity, isotopic

> **Comments:**
> **username_1**: It depends on what latitudes the fresh vs saline water samples are drawn from.  
> **username_2**: Did you have a visit at NASA' Goddard Institute and the open access  [Global Seawater Oxygen-18 Database](https://data.giss.nasa.gov/o18data/)?  
> **username_0**: I found out that δ18O differs by salinity because of precipitation and evaporation. But I'm not sure if it can also be applied to δ18O difference between seawater and freshwater.  

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## 0 answers

