Setting up the mesocosm facility
Important!
Plans must be discussed well in advance with TZS research coordinator and technicians. Minimum preparation time for experiments is 3-6 months.
Location
The main experimental site is situated ca. 800 meters from the Tvärminne Zoological Station (TZS). The location is sheltered and the depth is 6 m. From the nearby island, access to electricity can be provided (3-phase, 32A).
Platform is mobile, and can therefore be situated flexibly around the station depending on the specific needs of the experiment.
Mesocosm mooring location coordinates: N59 50,591/E23 15,680
Platform structure
Mesocosm platform is built from plastic pier components, readily available from TZS. Components allow modular design of the platform, and can be designed to meet the needs of different experiments (e.g. number and size of bags).
Platform is assembled on land, and the ready platform hauled with small boats to the location.
Platform is anchored with 200 kg concrete weights available from TZS. This part of the preparation is carried out exclusively by TZS staff.
Instrument shed may be installed if proper design efforts are carried out.
Component manufacturer:
Suomen Kelluva
c/o Tero Hyytiäinen
Equipment
Various equipment and tools are needed for the setup.
Mouth of the bag is made rigid with plastic rings (95 cm diameter, made from PVC water pipe).
Weights in the bottom of each bag is needed to keep them upright (washers + nuts + bulbs).
For securing the bags to the frames on the platform flex ropes + carbin hooks are used.
Bags
Mesocosm enclosures are plastic (LDPE), flexible bags with taped seams. Diameter of the typical bag is 1 m and height max. 5m. These dimensions result in maximum volume of ca. 4 m3 per bag. Bag height can be adjusted upon ordering them from the manufacturer.
The bag integrity decays gradually during the experiment, and the maximum duration of an experiment is 5-6 weeks.
Hardened acrylic covers for bags are available, which are highly recommeded for protecting the contents from e.g. bird droppings. Acrylic covers are sensitive to scratches and breaking, and their condition need to be checked before experiments. Magnus Lindström measured the light attenuation spectra for the covers, but the data are not digitized.
Bag supplier:
6T Solutions
c/o Tuukka Hakanen
Cover supplier:
Keraplast
c/o Ida Rantanen
Filling
For filling up the bags, using a pump is recommended. An impeller pump is available, which uses 230 V current. Portable generator can be used to power the pump. Capacity of the pump is 16,500 l/h, but effectively filling up one bag takes around 30 min. Effects of pumping on the plankton community are minuscule, as verified by Aleksandra Lewandowska in 2020.
Filling the bags can also be carried out by lifting up and down the bags, but control of the final volume is worse and this method is not recommended.
Time requirements
Careful planning is needed to secure the required personnel for each task related to mesocosm operations.
Platform assembly and set-up (if platform rebuilding from components is needed)
minimum 1 week for 2 people
Bag assembly
one day for a group of 2-4 people
Attaching and filling the bags
one day for a group of 2-4 for
Platform hauling and mooring
Contact TZS technical staff
Notes
Continuous in situ sensors are available for mesocosm experiments:
HOBO temperature, conductivity and dissolved oxygen sensors; 12 pcs
Cumulative volume that is taken during each sampling must be logged and monitored, as if too much water is used, buoancy and rigidness of the bags is decreased.