Tuesday, September 8, 2015

Research @ Otago - Tyler Northern

Tyler is studying the mineral make up of statoliths (a hard structure that works as a gravity receptor) from warty squid (Onykia ingens).

I am working closely with a group at the ALCES lab at AUT run by Dr Kathrin Bolstad who also study cephalopods (squid and octopus) around NZ.  As a result, I have recently been on a trawl survey with NIWA on their research vessel, the Tangaroa. I spent three and a half weeks living aboard the Tangaroa on the Chatham Rise in August 2015 and my job was to identify and collect cephalopods.
The RV Tangaroa docked in Lyttleton, Christchurch (Photo: Nathania Brooke)

Being aboard the Tangaroa was an amazing experience, I met lots of really easy going people and we were fed very well! We were targeting mid-trophic level organisms which means we wanted to catch the things that big fish eat, although we did get a few big fish! We measured and weighed all of the fish we caught and took stomach and tissue samples from a sub-sample of them to be analysed at NIWA.
Tyler with a 18kg Ling caught and sampled on the Chatham Rise

We also caught a lot of cool squid including my study animal! 

A mature warty squid (Onykia ingens) hauled up from the depths

If you have any questions you can email me at: tyler.northern@otago.ac.nz

Wednesday, July 29, 2015

Research @ Otago - Sorrel O'Connell-Milne

Sorrel is studying how parasite infection in clams varies in a commercial harvested environment.

Sorrel's research looks at the number of parasitic infections in the clam Austrovenus stutchburyi in  areas where commercial harvesting takes place and compares these with areas where there has been no harvesting.  She also examines the effect of these parasites on juvenile clam mortality, growth, body condition and foot length.

Mud snails were collected from Otago Harbour and their parasites were used to experimentally infect the juvenile clams and observe changes in their growth, body condition and foot length.
The parasites she studies are Curtutaria australis and Acanthoparyphium spp., two trematodes that play very similar roles within the ecosystem. These trematodes have a complex life cycle and require three different host species before they can reach maturity. The first intermediate host is a gastropod (whelk or mud snail) where the parasite infects the gonadal material, castrating the host and effectively turning the host into a 'parasite factory'.  The parasite then infects the second intermediate host, the clam, where the inactive juvenile stage is encapsulated as a cyst in the clam's foot.  The oystercatcher is the definitive host for the parasite and the trematode’s life cycle is completed when the oystercatcher preys upon the clam and ingests the trematode.
The trematodes encyst within the foot of the clam where they reduced foot muscle contractions and hinder burrowing behaviour.
As these parasites infect the foot of the clam they reduce the ability of the clam to bury into the sediment, increasing the chance of predation by birds seven-fold.  Effectively, the trematode is changing the clams burrowing behaviour and actively enhancing its own transmission to the definitive host, the oystercatcher.  However, not all is doom and gloom, parasites also have effects on the surrounding infauna; the shells of clams held above the sediment provide attachment surfaces and shelter for other organisms, which can result in increased biodiversity of the area.

Sorrel and her field volunteers, Chris and Steph, collecting clams in Blueskin Bay, Otago.
Areas with a reduced density of shellfish due to commercial harvesting were found to have 36% more parasites on average than equivalent unharvested areas. Results indicate that although mortality was unaffected by parasites infection directly, increased infestations negatively affect the growth, body condition and foot length of clams.  Therefore, in harvested areas increasednumbers of infections may result in the clam reaching maturity later and their ability to filter feed and bury into the sediment may be reduced.  This study portrays the complex impacts that human activity may have on the intertidal environment and highlights that commercial clam harvesting not only removes shellfish biomass but also has more inconspicuous effects on the surrounding ecosystem.

Sunday, May 3, 2015

Research @ Otago - Josie Crawshaw

Josie Crawshaw is studying the role of coastal lagoons and estuaries in removing nitrate from the water column before it reaches the ocean.
Josie collecting a sediment core from an enclosure at Lake Ellesmere
Our coastal waters are experiencing an increase in nutrient loading, due to increases in agricultural farming. Luckily, coastal ecosystems such as coastal lagoons and estuaries can perform an extremely important ecosystem function, and remove nitrate from the water column, before it reaches our oceans. This process is called denitrification, which is the conversion of nitrate from the water column, into nitrogen gas, and it is carried out in the sediment by denitrifying bacteria. Knowing what factors might influence this process, and how efficiently these systems can carry out this process is an important component that needs to be considered in catchment models of allowable nutrient loading.
The flexible enclosure in place
To study this, Josie has designed and built flexible in situ enclosures, which enclose a section of the water column and sediment. She uses stable isotope tracers to follow the conversion of nitrate to nitrogen gas and nitrous oxide.
Taking water samples from enclosures on windy days requires good balance!
Josie is also a keen diver, and an ambassador for Atlantis Dive. She tries to get out as often as she can, especially on research dives!

You can follow Josie's research and diving journey on the following pages.


Tuesday, April 21, 2015

Marine Science @ Otago - Oarfish

An Oarfish was found washed up in the Otago Harbour on 17th April 2015.  This specimen was 3 metres long.  They are known to grow to more than 11 metres in length!

There are thought to be only two species of Oarfish and this is the southern one, Regalecus glesne.  There are periodic strandings round New Zealand, but mainly in the Cook Strait region between our two islands.  It is an oceanic fish, so that is probably because of the ocean currents that are funnelled between our two main islands and then get caught in shallow bays or sandbanks.  

However, It is pretty rare to find an Oarfish washed up in our area, and especially such a good specimen.  The Otago Museum had about 5 reports of Oarfish found on local beaches from the last 150 years.  Since our story went out, I've had two further reports.  One was stranded in almost the same spot in 1998, and one was reported on a beach further south in 2011.

They are often found after storms or earthquakes, which has given them a bit of a reputation as harbingers of doom!  This specimen was stranded after some very stormy weather.
Little is known about the Oarfish.  When this was dissected, its stomach was full of nyctiphanes (krill).  Other specimens have also been found stuffed full of krill.  They are a deep water ocean fish.  They have been some caught on video in recent years and they have been observed swimming vertically with their pectoral fins out to the side, which is how they get their name "Oarfish". 

Tyson Roberts wrote a book on Oarfish in 2012 and he suggested that Oarfish "self-amputate"  their tails.  This is his theory based on finding specimens that have obviously healed up after losing their tails.   It has been suggested by others that this might be caused by injuries or attacks by other creatures.  Perhaps they shed parts of their tails as a defence mechanism - like skinks and lizards - to help them escape.  As long as the injury is not too bad it may heal and grow back.  But who knows what goes on in the deep ocean and the lives of these amazing fish!

Marine Science @ Otago - Sir Peter Blake Ambassadors

Marine Science Students, Zac Penman and Blake Hornblow, were selected by the Sir Peter Blake Trust as NIWA Science Ambassadors and in early 2015 joined a voyage to Antarctica on the NIWA vessel, Tangaroa. 
The Blake NIWA Ambassador programme is a once-in-a-lifetime adventure to work alongside and assist world class scientists in ground breaking research for New Zealand. 

The 2015 expedition on board the NIWA research vessel Tangaroa partnered with Antarctica New Zealand and the Australian Antarctic Division to undertake a six-week research initiative in the Southern Ocean on areas of importance to humpback, blue whales and Antarctic toothfish.

To read about their journey see their voyage blog:

The 2015 expedition is on-board the NIWA research vessel Tangaroa which will be partnering with Antarctica New Zealand and the Australian Antarctic Division and undertaking a six-week research initiative in the Southern Ocean on areas of importance to humpback, blue whales and Antarctic toothfish.
- See more at: http://www.sirpeterblaketrust.org/young-blake-expeditions/niwa-science-ambassador/follow-the-adventure-2015/#sthash.J71db5uI.dpufFor more about their journey: