The first prototype of a photo-detection unit of the future KM3NeT neutrino telescope has been deployed in the deep waters of the Mediterranean Sea. This digital optical module has a novel design...

The NEutrino Mediterranean Observatory-Submarine Network 1 (NEMO-SN1) seafloor observatory is located in the central Mediterranean Sea, Western Ionian Sea, off Eastern Sicily (Southern Italy) at 2100-m water depth, 25 km from the harbor of the city of Catania. It is a prototype of a cabled deep-sea multiparameter observatory and the first one operating with real-time data transmission in Europe since 2005. NEMO-SN1 is also the first-established node of the European Multidisciplinary Seafloor Observatory (EMSO), one of the incoming European large-scale research infrastructures included in the Roadmap of the European Strategy Forum on Research Infrastructures (ESFRI) since 2006. EMSO will specifically address long-term monitoring of environmental processes related to marine ecosystems, climate change, and geohazards. NEMO-SN1 has been deployed and developed over the last decade thanks to Italian funding and to the European Commission (EC) project European Seas Observatory NETwork-Network of Excellence (ESONET-NoE, 2007-2011) that funded the Listening to the Deep Ocean-Demonstration Mission (LIDO-DM) and a technological interoperability test (http://www.esonet-emso.org). NEMO-SN1 is performing geophysical and environmental long-term monitoring by acquiring seismological, geomagnetic, gravimetric, accelerometric, physico-oceanographic, hydroacoustic, and bioacoustic measurements. Scientific objectives include studying seismic signals, tsunami generation and warnings, its hydroacoustic precursors, and ambient noise characterization in terms of marine mammal sounds, environmental and anthropogenic sources. NEMO-SN1 is also an important test site for the construction of the Kilometre-Cube Underwater Neutrino Telescope (KM3NeT), another large-scale research infrastructure included in the ESFRI Roadmap based on a large volume neutrino telescope. The description of the observatory and its most recent implementations is presented. On June 9, 2012, NEMO-SN1 was successfully deployed and is working in real time.

The sperm whale (Physeter macrocephalus) emits a typical short acoustic signal, defined as a “click”, almost continuously while diving. It is produced in different time patterns to acoustically explore the environment and communicate with conspecifics. Each emitted click has a multi-pulse structure, resulting from the production of the sound within the sperm whale’s head. A Stable Inter Pulse Interval (Stable IPI) can be identified among the pulses that compose a single click. Applying specific algorithms, the measurement of this interval provides useful information to assess the total length of the animal recorded. In January 2005, a cabled hydrophone array was deployed at a depth of 2,100 m in the Central Mediterranean Sea, 25 km offshore Catania (Ionian Sea). The acoustic antenna, named OνDE (Ocean noise Detection Experiment), was in operation until November 2006. OνDE provided real time acoustic data used to perform Passive Acoustic Monitoring (PAM) of cetacean sound emissions. In this work, an innovative approach was applied to automatically measure the Stable IPI of the clicks, performing a cepstrum analysis to the energy (square amplitude) of the signals. About 2,100 five-minute recordings were processed to study the size distribution of the sperm whales detected during the OνDE long term deep-sea acoustic monitoring. Stable IPIs were measured in the range between 2.1 ms and 6.4 ms. The equations of Gordon (1991) and of Growcott (2011) were used to convert the IPIs into measures of size. The results revealed that the sperm whales recorded were distributed in length from about 7.5 m to 14 m. The size category most represented was from 9 m to 12 m (adult females or juvenile males) and specimens longer than 14 m (old males) seemed to be absent.