Valeriano Parravicini, taking the “pulse” of atolls

© Pierre de Parscau

The schooner left 10 days ago from Papeete with the newly embarked BioAtoll team to complete and diversify the samples collected since the beginning of the Tara Pacific expedition. We interviewed Valeriano Parravicini (CRIOBE/EPHE-CNRS-UPVD) who is in charge of leading this 2-week exploration around the Tuamotu Islands.

 

tara-2016_10_29_pdeparscau6taraValeriano Parravicini, leader of the BioAtoll mission. © Pierre de Parscau /  Tara Expeditions Foundation

What are the objectives of this part of the expedition called « BioAtoll »?

The goal is to sample 7 atolls presenting different morphologies. First we’re going to sample 3 filled atolls – where there’s no lagoon left. There are only 4 of these in Polynesia. Then we chose 2 atolls with a closed lagoon – without any pass allowing water circulation between lagoon and ocean. Finally, we’re going to study 2 open atolls where there’s a real exchange between lagoon and reef.

The typical atoll’s shape is a lagoon connected to the ocean by a pass. The question is whether a link exists between the lagoon presence and productivity of the reef’s external slopes. A lagoon is the quietest and most accessible place. Therefore, it’s the most affected by human activities. Several fish species take advantage of the refuge – entering as larvae stage and leaving after growing up. Lagoon waters are also rich in nutrients, unlike the oceanic environment. If the lagoon became too affected by human activities, what would the effects be on the reef’s external slopes?

 

bioatolls_01Three examples of islands with different morphologies: Akiaki (filled lagoon), Haraiki (open lagoon), Vahitahi (closed lagoon).

Is the lagoon more threatened today than a few years ago?

Yes, several scientific articles have pointed out 2 aspects: 1) there’s almost no place left in the world that isn’t affected by human activities and 2) places that are currently less impacted are gradually deteriorating. The danger is that we end up forgetting what a healthy lagoon looks like while getting used to the degradations. Climate effects are visible even here: we’ve seen dead and bleached corals during our first dives. The cyclical and climatic El Niño phenomenon plays an important role in these deteriorations because of the temperature rise it generates. However, I believe the human factor remains the main cause. On the positive side, climate change consequences can only be addressed on a global scale whereas human impact can be controlled locally.

 

Who is part of the team for this mission?

The tools we use are quite conventional. We chose 2 different subjects for this study: corals and fish. Our team consists of 6 people: 4 fish counters in addition to Arjun Chennu – who came with the HyperDiver, a machine designed to retrieve information on biodiversity in an automatic way – and myself. I’ve already collaborated with Serge Planes, scientific director of the Tara Pacific expedition (CRIOBE-EPHE/CNRS/UPVD). Michael Berumen and Geoffrey Jones have joined us from Saudi Arabia and Australia because they have experienceworking in Polynesia. It’s really important to have counters who are comfortable working together and know Polynesian fish. This avoids confusion between species that sometimes look alike.

 

tara-2016_10_29_pdeparscau3taraDavid Monmarché, hyperbaric chief operator, supervises the BioAtoll team dive © Pierre de Parscau / Tara Expeditions Foundation

What are the features of diving in the Tuamotu Archipelago?

The difficulty we meet while counting fish and analyzing benthic communities (species that live at the sea bottom) comes from swell. We position a 50-meter long rope measure on the lagoon’s floor that serves as a guide during our counting. When the swell is heavy, it’s very difficult to follow this marker. To give you an idea, after sampling the first 3 atolls of this mission, each counter entered at least a thousand items into our database. We’ll analyze the data during the first 2 weeks following our return and then it will take 6 months to get the first statistical results.

 

It’s your first time aboard Tara. What difference does this make for your research?

It’s the first time I’ve worked aboard a sailboat. The scientific vessels I usually board have very different characteristics. To conduct this sampling, it’s convenient to work aboard Tara because we can cover scales impossible to reach with other boats.

Interview by Pierre de Parscau

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