Chagos 2016 - Day 12

Scientists from TRCC and GTOPP are at sea in the Indian Ocean with the Bertarelli Foundation's Chagos Archipelago Science Expedition 2016.  The daily reports are compiled by Dr. Heather Koldewey, Chief Scientist of the Expedition, and Dr. Barbara Block and Dr. Rob Dunbar from Stanford.

Day 12 highlights – 16 th April 2016 

Peros Banhos Atoll

Last day of fieldwork!

Further Salomon Highlights 15 th April

The Manta Team had a majestic day at Salomon – the taggers and

crew worked together to spot and tag 7 Mantas with pop-up

satellite tags, acoustic tags and camera tags. The satellite tags

range in duration from 180 to 365 days.

This manta did acrobatic feeding rolls while Robbie waited patiently to tag it

First manta tagged with a camera tag!

Thanks to the Vava II Salomon Manta Team!

Final fieldwork day for the team at 

Peros Banhos – and what a finale!

Coral Reef Team

The two sites surveyed today at Peros Banhos

had very high reef fish numbers and diversity

Coral disease

• Disease prevalence often increases

when corals are stressed

• Assessed the presence of coral diseases in the Chagos Archipelago

• Purple spot disease

• White band disease

'Reef of hope'

The final reef site at Moresby Island surveyed today

showed a very high number of younger corals from

several years and less bleaching than elsewhere. Local

oceanographic conditions may be a factor at this site.

Results will become clearer as data are analysed.

Tagging Team

Today was filled with rare tuna sights:

A small tuna, kawakawa (Euthynnus affini) jumping in the lagoon!

A dogtooth tuna was also seen on a dive – a first for Barb!

Ten sharks were tagged today

Species movements

• 58 receivers serviced and 33 new ones added

• 170,000 detections of 88 animals – 31 Grey Reefs, 22 Silvertips, 11 Mantas, 2 Nurse Sharks and 22 Bohar (fish)

• Two female Grey Reef Sharks were detected for the third year running!

• One of the Mantas made a 300nm round trip from Egmont, via Peros Banhos, Salomon, Speakers Bank and Victory Bank between June and November last year. It spent most of that time at the newly discovered ‘Manta Alley’ in Salomon Atoll.

A brilliant final Day! From the REEF & TAGGING TEAMS

Chagos 2016 - Day 11

Scientists from TRCC and GTOPP are at sea in the Indian Ocean with the Bertarelli Foundation's Chagos Archipelago Science Expedition 2016.  The daily reports are compiled by Dr. Heather Koldewey, Chief Scientist of the Expedition, and Dr. Barbara Block and Dr. Rob Dunbar from Stanford.

Day 11 highlights - 15th April 2016, Salomon Atoll

Value of long term data sets

• Today highlights the importance of long term data sets for the Chagos Archipelago
• Video data from Bangor Uni goes back to 2006 from Ile Passe (surveyed today) and other sites.
• Team members have surveyed these sites since 2012 and have recorded considerable changes.
• Due to the lack of local human impacts, the Chagos Archipelago provides a vital global reference site during this global coral bleaching event.
• Our discussions here have led to plans to use previous and new data for a collaborative peer reviewed publication from this expedition.

 

Coral Reef Team

A logging instrument that measures temperature, salinity, and depth every 10 minutes was installed at the entrance channel to Salomon Atoll.

This will help us understand how Salomon Atoll modifies waters derived from offshore. Atoll lagoon system properties control water density and also influence the distribution of life in the marine environment.

Twilight reefs of Ile Passe, Salomon

• Many fish associated with coral colonies
• Identified large schools of Thompson Surgeonfish over the reef from 40-50m depth
• Deepest reported sea anemones in Chagos Archipelago at 54m

Yellow damselfish associated with twilight coral

Thompson Surgeonfish

 Anemones on twilight reefs

Tagging Team

Another productive day for the shark tagging team. 14 sharks tagged, 2 SPOT tags deployed and another recapture!

This silvertip shark recapture was tagged yesterday in the same spot and almost at the same time…. it may not be the brightest shark in the atoll!

Thanks for another great day! Huge thanks to the Captain and crew for continued fantastic support on and off boats, underwater and back on Vava II.
 

Chagos 2016 - Day 8

Scientists from TRCC and GTOPP are at sea in the Indian Ocean with the Bertarelli Foundation's Chagos Archipelago Science Expedition 2016.  Dr Heather Koldewey, Chief Scientist of the Expedition, wrote:
 

Day 8 highlights – 12th April 2016, Egmont Atoll

Seamount tagging day!

•In a positive change from the original schedule (due to no longer needing to drop kit at Diego Garcia at the end of the trip), we spent today at Sandes/Swart seamounts with the sole focus on tagging sharks.

•The coral reef team helped out the tagging team, enjoyed the experience of helping tag sharks, and/or spent time preparing kit, processing samples and data.

Sandes seamount above and below the water – an incredible number of sharks which was encouraging to see. Shark abundance we should aim for throughout the reserve.

Working in shifts, the tagging team worked from early morning to dusk.

In addition to deploying tags, small tissue samples were taken for DNA and isotope analysis to be processed back in the lab.

A record total of 32 sharks were tagged today which was an outstanding achievement by the tagging team!

A series of new receivers were also deployed on the two seamounts, which will help track movements of tagged sharks around the Archipelago. 

The reef team tried to document the reefs on top of Sandes seamount without success, but did get some great shark images!

Particular thanks to the Captain and crew of Vava II today for supporting the tagging team so ably, especially in challenging sea conditions. The team were able to achieve a record tagging day thanks to you!

Chagos 2016 - Day 7

Scientists from TRCC and GTOPP are at sea in the Indian Ocean with the Bertarelli Foundation's Chagos Archipelago Science Expedition 2016.  Dr Heather Koldewey, Chief Scientist of the Expedition, wrote:

Day 7 highlights – 11th April 2016,  Egmont Atoll

Turtle team

• Two fresh hawksbill turtle tracks on Egmont Island today – these are new since the surveys yesterday.
  
• Lots of turtles seen during dives.

Coral Reef Team

The reef 3D models are developing well and we are hoping to use the super- computing power of the Vava II to process some of the larger projects while we are here.

Bleaching is progressing at most of the sites and has started to affect many different species and growth forms in the shallows down to around 12 m including some of the massive Porites boulder corals.

Environmental DNA (eDNA)

• eDNA is an exciting new monitoring technique being used for the first time in the Chagos Archipelago!
  
• Fish, corals and other reef life all release small amounts of DNA into the water, which we collect from the reef at all sites surveyed.
  
• These water samples are pumped through a filter, catching all the tiny DNA fragments.
  
• Genetic techniques will be used to identify reef life in the Chagos Archipelago, from microbes to sharks, just from these tiny DNA fragments floating in the water.
  

Tagging team

5 mantas tagged today in Egmont Atoll

False killer whales

• Identification of whales confirmed as false killer whales (Pseudorca crassidens) by colleagues at ZSL and Stanford.
  
• The prey of this species includes a variety of large pelagic fish, including several species of tuna.
  
• They are Data Deficient on IUCN Red List of Threatened Species.
  
• Main threats are bycatch from fisheries, decline of prey species and accumulation of high levels of persistent organic pollutants. The BIOT marine reserve is therefore a valuable refuge for this species.
  
• The false killer whale is a relatively poorly known species, and more research is needed.
  

Thanks for another busy but great day! 

Chagos 2016 - Day 4

Scientists from TRCC and GTOPP are at sea in the Indian Ocean with the Bertarelli Foundation's Chagos Archipelago Science Expedition 2016.  Dr Heather Koldewey, Chief Scientist of the Expedition, wrote: 

Day 4 highlights – 8th April 2016, Peros Banhos 

Turtle Team

• Today saw one turtle track on Vache Marine

• Aerial surveys completed in southwest of Peros Banhos atoll

• Signs (bottom) that the donkey is alive and well!

• Thanks Benoit and Lukas for continuing the turtle (and donkey!) research!

Coral Reef Team

• A busy day of surveys inside the lagoon (Bernards Knoll) and on the seaward side of Ile Poule.
• Ile Poule site had abundant reef fish populations.

Coral Health - Peros Banhos Reflection
• Past 3 days surveyed north, west & south
– Reef seems healthier in southern Peros Banhos
• But here at critical time
– Southern Peros Banhos sites showing early signs of bleaching

• –  Very worrying as large amount of damage to coral likely
  
• –  However, large numbers of juvenile corals on reef that appear less affected – so potential good recovery
  
• 
  
• 
  
  
  
  
  
• 
  

Lagoonal twilight zone reefs

• Continued twilight reef exploration (deeper than 30m) with the ROV in Peros Banhos lagoon:

• –  Interesting mix of corals and large fleshy algae not seen on shallow reefs
  
• –  3 grey & 1 black-tip reef sharks hanging out under VAVA II
  
• –  ‘Flattened’ corals adapted to deep reefs
  

Tagging and Array team

All hydrophones (except one which will be done early tomorrow) in Peros Banhos serviced

Great achievement by the Array Team and a huge amount of work!

Tagging team
• An exciting and very busy day for the tagging team:

• –  13 sharks tagged (grey reef sharks and silvertips)
  
• –  First camera tag deployed on grey reef shark
  
• –  First new generation tag deployed on grey reef shark
  

New Generation Pop Up Satellite Tag on Grey Reef Shark

A stunning end to another busy and productive day. Thanks everyone!