Now.
And the answer is...
1. Most marine organisms ignore me.
2. Cyanobacteria sometimes don’t ignore me.
3. I like colder seawater
4. In 35 ppt seawater at 25 deg C, there is about 10.4 ppm of me present
What am I?
Nitrogen, N2.
Solubility of N2 from air is higher in colder water, and at normal pressure and temperature, there is about 10-11 ppm in seawater.
Unlike most marine organisms, that ignore N2, some types of cyanobacteria can take in N2 and "fix" it. That is, they can use it as a source of nitrogen for biomolecules.
What is Seawater? by Randy Holmes-Farley - Reefkeeping.com
Dissolved Atmospheric Gases
Any gas present in the atmosphere will be present in seawater. Many of these are unimportant to reef aquarists, but two are of critical importance: oxygen and carbon dioxide. Aside from carbon dioxide, all of the gases have lower solubility in seawater as the temperature and salinity are raised. Table 4 shows the concentration of the most common gases in seawater at 25°C.
Oxygen is generally most highly concentrated near the ocean's surface. In the top 50 meters or so, oxygen's concentration is controlled largely by exchange with the atmosphere, and is usually close to equilibrium with the air. Between 50 and 100 meters, the O2 level often rises due to photosynthesis. Below about 100 meters in the open ocean the oxygen level drops steadily for the next 1000 meters or so due to biological processes that consume it. It then sometimes rises again in the deeper oceans as oxygen there is replenished by sinking cold ocean water that is rich in oxygen. The importance of dissolved oxygen in seawater and reef aquaria has been discussed in a series of previous articles:
The Need to Breathe in Reef Tanks: Is it a Given Right?
http://www.reefkeeping.com/issues/2005-06/eb/index.php
The Need to Breathe, Part 2: Experimental Tanks
http://www.reefkeeping.com/issues/2005-07/eb/index.php
The Need to Breathe, Part 3: Real Tanks and Real Importance
http://reefkeeping.com/issues/2005-08/eb/index.php
Table 4. Atmospheric gases in seawater at 25 deg C when in equilibrium with air. | |
| Gas | Concentration |
| Carbon dioxide (as HCO3- and CO3--) | 100 ppm of CO2 |
| Nitrogen (N2) | 10.7 ppm |
| Oxygen (O2) | 6.6 ppm |
| Argon (Ar) | 0.40 ppm |
| Neon (Ne) | 0.13 ppb |
| Helium (He) | 0.0066 ppb |
| Krypton (Kr) | 0.185 ppb |
| Xenon (Xe) | 0.038 ppb |
