After returning from fair isle and i started looking at my results, two things become apparent. In certain scenarios nitrogen can have an effect on, not just an increasing in phytoplankton numbers, but if the compound in question, DMSP is produced rather then a more favorable compound such as proline. The other is cell history is also important, which can be indirectly extrapolated from historical environmental. During my research, eather i didn’t do my research properly, or there isn’t much particular branch, but i failed to sample for nitrogen compounds and i didn’t have a reliable method to get previous environmental conditions. Depending what you are looking for there are a range of options for this, some free and some paid for and some aren’t available.
NASA is able to offer usage of their satellites, but its only covers one moment in time approximately every 12 hours and misses important variables, notability salinity, conductivity
Argo floats offer pressure, conductivity, temperature, but since they rely on currents to drive their movement, they tend not to stick in one location or at a single depth.
Alternatively you can launch your own
These can be bought in/prefab or DIY.
The benefit here is that you can place one where ever you want (Permission must be sort for the owner of the water) and you can put whatever you want onto them, the downside is that they can cost allot, not just to buy and kit out, but also deploy, costing £1,000s to get into the water. Then threes the software behind them. These may be priority, meaning that you have to lock yourself into one vendor. If someone offers a better PH sensor, you may not be able to take advantage of that or integrate your own sensors.
In order to get the best flexibility the DIY route may be a route that offers more for less… as long as your willing to put the effort in. The quality of the data and the cost boils down to the sensors you decide to use, if these are bought off the shelf or built.
Atlas Scientific off a range of sensors, these are plug and play, but if your trying to ‘budget’ the cost can add up. A stamp is used to interface between the probe and your micro controller or data logger. These alone cost between $20-$30 each, and then a sensor on top, so the price adds up, but depending on what you use, the ‘stamp’ may not be worth it. If we take temperature for example, the simplest being a thermometer, as the temperature changes, the resistance changes, meaning that you will get a change in voltage. If you measure several points (2 or more) you can figure out an equation to represent the relationship in voltage change and temperature. Other temperature sensors spit out a value, such as the DS18B20 introduced by Dallas Semiconductor. pH works the same, in that a small voltage is produced and you just have to sense it. An op-amp may be needed to amplify the the voltage as the difference may be too subtle for a micro controller that isn’t highly sensitive to detect such a change.
If i want to gather historical data of a given site, i would need to deploy my own buoy, but to make it cost effective I would need go down the DIY route, to make it viable. With technology such as mobile phones, it has made everything more cost effective in this respect, not just for the processors, but sensors and batteries but also making them power efficent