We have arrived at the STARESO - Station de Recherches Sous-marines et Oceanographiques in Corsica. Our objective is to measure how the Seagrass oxygen production during its daily cycle affects the propagation of sound in the ocean. The received acoustic signal can be analysed to infer on the oxygen production on a given transect


The STARESO Research Station

Today we are setting up all our acoustic equipment, during the morning the acoustic transmiting station was setup and placed in the water.


The Acoustic Source a Lubell LL916C just before mooring



The Acoustic Source after mooring in 5 meter water depth, 2 meters from the sea floor

A set of received signals on the Autonomous Hydrophone Recorders during a testrun

A MarSensing digitalHyd SR-1 Autonomous Hydrophone recorder used at the receiving station.


The Kayak with the 3 autonomous hydrophones, a set of diver weights and floats visible at the front


Mooring from the Kayak of the 3 autonomous hydrophone array in 22m water depth

This figure shows the equipment setup in this experiment


A view of the equipment moorings from above the station..

This morning we perfomed CTD measurements along the transmission transect and also in the CALVI bay.


CTD measurements performed from the boat.

After lunch the hydrophones were recovered and the data retrieved.

The hydrophones after recovery.

Hydrophones were reprogrammed and memory card and battery was exchanged ready for redeployment and a full 24 hours of recording.
Some data from the hydrophone 1 was analysed and presented is the impulse response using the received signals

In the morning more CTDs were performed along the acoustic transmission path. Due to a an increase of wind and meteorological predictions that up-to 20kn of wind are expected for the next hours / days, the acoustic source was repositioned further away from the pier. At this time Hydrophones were also recovered and data retrieved.

Wind increase at the station.

Hydrophones redeployment with the rough weather increasing, we are at ~15kn of wind. A CTD was also performed close to the receiving station.

Hydrophones Redeployment for night-time acquistion.

Presented in the following figures are the impulse responses during the acquisition cycle of hydrophone 2 (4 meters from sea floor) from last night. Observable in both figures is a change of the impulse responses at ~7pm (localtime) and at ~7am (localtime) in correspondance with day light.

Impulse Responses from the low frequency band (400-800Hz).


Impulse Responses from the medium frequency band (1500-3500Hz).

Listen to the sound of our transmitted signals as received on the hydrophones. Right at the begining you can also hear the sound of (Damselfish ?) which is a constant throughout the acquired data.

Today we had some rough weather, the hydrophones were recovered in the afternoon and will only be redeployed once conditions permit...

Today it was not possible to redeploy the hydrophones due to bad weather. A short presentation by each of the groups was held at the end of the day.

Re-deployment of the hydrophones in the morning. The repetition rate of the transmissions was increased to every 5 minutes (from every 15 minutes).

Recovery and re-deployment of the hydrophones in the afternoon. one of the hydrophones was equipped with a larger battery pack.

The digitalHyd SR-1 self recording hydrophones, standard and extended battery pack.

CTDs performed in the morning. It is planned to recover and re-deploy all hydrophones in the afternoon. The weather is excellent.

The Portable Acoustic Source Unit (PASU). This includes a portable computer for the signal generation, the audio amplifier and the impedance adapter for the Lubell L916C underwater loud speaker. The PASU is contained in a PELI box and can be powered from its internal battery or externaly.

The hydrophones were recovered and re-deployed late yesterday afternoon. Today the weather conditions are good. It was possible to take the kayaks to the hydrophone mooring and take some pictures.

A picture of the hydrophone mooring taken this moorning from close to the sea surface. The hydrophones are in ~15-20m depth.