The key factors allowing the plants growth inside the biospheres are: temperature (of the air inside the biosphere and the surrounding seawater), illuminance and indoor humidity. All these variables are monitored 24/24 hours every day in the Underwater Lab and all the live data are shared through the sensor panel page on the website.
The trend page, instead, shows all the data gathered since the beginning of the experiment. In this way all the monitored parameters can be related to the weather conditions, works maintenance, anomalies, etc.
In Nemo’s Garden direct sunlight gets inside the biosphere passing through the mass of seawater and the polymeric film constituting the dome. In the Noli’s Bay sun rays direction varies during the day. Indeed, the light sensor records a peak, where the maximum is reached during the day in the early afternoon (around 3-4 PM). Of course over night the illuminance is zero. The light transfer in the seawater mass determines a reduction of illuminance in respect to those typical of daylight and direct sunlight. A further reduction is observed in function of weather conditions and water depth. It is worth to note that the polymeric film constituting the biosphere shows a very high light transmission (>94%), thus not hampering the sunlight to reach the plants.
Current experiments demonstrated that the amount of sunlight illuminating the biosphere is sufficient to allow the plants growth. However, we need to keep investigating to better understand the influence of illuminance and its effectiveness on underwater crops; effects given by pressure, temperature, humidity, etc. might counter balance less light.
Water evaporation- condensation
Thanks to the nearly stable temperature of the water throughout the day, and the thermal excursion occurring inside the biosphere between night and dau, the seawater inside the biosphere can evaporate and condense on the internal surfaces of biosphere (cooler than the air). In this way fresh water is formed and it can be used for the growth of the plants, making Nemo's Garden a self-sustainable system.
The water evaporation-condensation is monitored in terms of Relative Humidity percentage (RH%) inside the biosphere. Usually plants need 70-75 RH% in standard conditions of growth. Generally speaking, RH% in the biosphere is very high: values up to 97% RH% have been recorded overnight during the day, RH% decreased till 85 % minimum.
Due to the high content of humidity, a large amount of fresh water is collected on the biosphere surfaces. This fresh water, once collected, can finally canalized inside the hydroponic system. Minerals are added to the fresh water collected which, after the evaporation-condensation process, does not contain any minerals.
Analyses performed on fresh water formed during evaporation demonstrates that it has physical-chemical and organoleptic characteristics in agreement with those required by the Italian legislation to a typical water employed for irrigation.
Data have shown us that higher pressure conditions effect the plants growth in a positive way which basically means a faster germination.
At the present the literature regarding this topic is very limited and only few studies concerning the use of hyperbaric chambers on land are reported. The novelty introduced by Nemo’s Garden Project could represent a less expensive alternative of having an accelerated growth rate.
Nemo’s Garden can be considered as a stable system when the equilibrium conditions are reached in terms of temperature, RH% and illuminance. This intrinsic stationarity is the key to allow a good plants growth, together with the water evaporation-condensation process.
Temperature of both the air inside the biosphere and the seawater are continuously recorded. Nowadays, the recorded seawater temperature of the Mediterranean is really close to the temperature of a typical tropical sea.
Thermal excursion occurring in seawater between day and night is almost constant. This evidence is the key factor for making possible the water condensation inside the biosphere.
Also the air temperature inside the biosphere shows a variation of approx. 3-4 °C in between day and night. Peaks of 30-31°C have been recorded during the same period (late July). Temperature inside the biosphere is higher than that of seawater. This is why we have the evaporation of the sea water inside each biosphere.
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