January 10, 2018

Life in the deep blue

Posted by larryohanlon

For the second two weeks of November, RV Investigator is home to twenty marine science students, as we are part of the first Collaborative Australian Postgraduate Sea Training Alliance Network (CAPSTAN) voyage, travelling from Fremantle to Hobart across the Great Australian Bight. This blog reveals some of the marine creatures encountered on the voyage by three such students; Kate Simmonds, Helen Hayes and Anthony Uwalaka. Kate recently completed her Honours year at The University of New South Wales, where she researched how the El Niño – Southern Oscillation, an ocean-atmosphere phenomenon, affects temperature extremes in Australia. Helen is currently researching mixotrophy in phytoplankton for her Honours project, as part of her Masters degree in Marine Science & Management at The University of Technology, Sydney.  Anthony is currently enrolled in a Master of Petroleum Geoscience degree at the University of Western Australia and his prospective project is on submarine slope processes: the origin of the Perth Canyon.

The surface of the ocean is a deep blue, with white-tipped waves crashing around the RV Investigator and towards the horizon. Beneath the surface of the ocean, an abundance of life resides. The colour and vibrancy of coral reefs, the majesty of breaching whales and dolphins, as well as the mysterious deep abyss show life can thrive in the most wonderous places in the ocean.

Just above the water, curious seabirds, including species of shearwaters, gannets, albatross and terns, skip across the waves around us as they scour for food. The wandering albatross provides a particularly spectacular display, with the longest wingspan of any living bird. By collecting seabird data along our designated Bremer Canyon transect, we can learn both where they look for sustenance, and where there may be ocean mammals lurking just below the surface.

Our first indication of megafauna was a group of seabirds circling above the water, and before long, a pod of approximately a hundred pilot whales emerged. A few members of this pod are photographed (above) breaching the surface as they swam alongside the RV Investigator. They were likely attracted to the ship by the sonar gun used for bathymetric mapping of the ocean floor. This interaction between seabirds and large mammals shows just one of the complex dynamics between ocean life that we have seen during our voyage so far.

But what about the wide, open seas; can a lot of organisms live in such a vast blue desert? Fellow marine explorers, do not be fooled by the apparent emptiness of the sea, with the help of a plankton tow net and microscope you can explore the true wonders of the unseen microbial world of plankton!

Whales, seabirds and fish all rely on the plankton to serve as food; without which, life in the oceans would cease to exist. Plankton can be grouped into two types; phytoplankton and zooplankton. Just like on land, life in the open seas starts with a photosynthesising plant organism; phytoplankton! We found a beautiful species of dinoflagellate, Ceratium (pictured above).

Where there are plants there are always predators, which take the form of zooplankton in this dynamic microscopic world (above). Copepods are some of the most abundant organisms in all the world’s oceans! Larvae from many marine invertebrate families spend some time in the ocean currents as zooplankton, including starfish, crabs and lobsters, urchins and even fish.

Resting along the sea floor, from the recovered sediment core sample, we observed the presence of marine protozoa. These organisms are called foraminifera (forams) and they appear in different shapes and occur in different environments, from near shore to the deep sea, and from near surface to the ocean floor. They are very abundant in most marine sediments and live in marine to brackish water. The complexity of their shell structures (and their evolution in time) is the foundation of their geological usefulness. We photographed forams under the microscope amongst broken shell fragments and sediment (right). These organisms are mineralised and have carbonate walls. The significance of the foraminifera includes, but is not limited to, understanding how fossil organisms lived for historic ecological studies or modelling climate change throughout geological time.

Under the opaque blue, diverse worlds begin to emerge throughout all depths of the ocean, ranging from the greatest mammals to the smallest phytoplankton and forams. All one needs to do is look.

Want to know more about the CAPSTAN program? Check out our official website at: https://goto.mq/6g

Read more from the student participants in the CAPSTAN blog at https://voyage9181.wordpress.com or from our CAPSTAN director at https://aprilabbott.wordpress.com