Deep Sea Fishes – One Ten East Log

One Ten East Logs from the IIOE-2 voyage aboard RV Investigator will be posted on the WAMSI website during the month long voyage.

We are directly west of Fremantle and today have enjoyed very calm conditions with a beautiful long swell.

Log from One Ten East

The RV Investigator is currently undertaking oceanographic research along the 110°E meridian off Western Australia as part of the second International Indian Ocean Expedition. The voyage is led by Professor Lynnath Beckley of Murdoch University and the research is supported by a grant of sea time on RV Investigator from the CSIRO Marine National Facility.

Notes: The night samples at Station 6 were jam-packed with phyllosoma (rock lobster) larvae, which had the zooplankton scientists grinning from ear to ear. The whole ship’s complement is enjoying the lovely calm weather.

Deep Sea Fishes

By Daniel Cohen and Dr M. Pilar Olivar

Deep-sea fishes reside at depths greater than 200 m beyond the effective influence of sunlight for most of the time. The mesopelagic zone (between 200–1000 m depths) is home to many diverse and bizarre fishes, such as dragonfishes, snaketooths, bristlemouths, hatchetfishes, lightfishes and lanternfishes. The early stages of these fishes develop in the epipelagic layer nearer to the surface, but juveniles and adults move down into the dark zone. Some families are characterized by performing diel vertical migrations through the water column (e.g., lanternfishes), while others (e.g., bristlemouths or hatchetfishes) remain in the dark part of the ocean all the time.

Species of the family Myctophidae (lanternfish) are the dominant migrating mesopelagic fishes, and they constitute the focus of our studies on this voyage.  Adult myctophids are small (from 3 to 10 cm) and have some similarity in appearance to an anchovy, although being darker in color and characterized by the presence of small luminous organs on their bodies. Their larvae are small (from 2 to 15 mm) and transparent, similar to those of many other fish species. Myctophid larvae generally dominate plankton samples from the deep open ocean.

Worldwide, lanternfish comprise about 250 species and account for 65% of mesopelagic fish biomass. The name myctophid comes from the Greek word “mykter” meaning nose and “ophis” meaning serpent, while the common name lanternfish describes the array of light emitting organs called photophores that occur in species-specific patterns on their bodies.

Living in the light-limited mesopelagic zone means little access to prey. Myctophids deal with this problem by performing diel vertical migration, being the movement up into the plankton rich surface waters at night to feed, before returning to the safety of the deep during the day. In this way, myctophids occupy an important position in the oceanic food web transporting organic matter vertically through their migrations and providing food for larger predatory species.

Despite their importance, relatively little is known about myctophids in the south-east Indian Ocean and this is largely due to the difficulty in sampling deep-sea fishes. Fortunately, thanks to their diel vertical migration at night, when they are feeding near the surface, these fishes can be captured using large nets towed from research vessels. Additionally, the presence of their larval stages nearer to the surface allows sampling by means of standard plankton nets, and an indirect way of studying species distribution, abundance and diversity. Lanternfishes, through their abundance, play a vital role in the health and functioning of the ocean, particularly because they are prey for commercially important species such as tuna, mackerel and squid and ecologically significant species such as seabirds and whales.

Be sure to follow our daily Log from One Ten East at https://iioe-2.incois.gov.in or www.wamsi.org.au.

One Ten East Logs from the IIOE-2 voyage aboard RV Investigator will be posted on the WAMSI website during the month long voyage.

Log from One Ten East

The RV Investigator is currently undertaking oceanographic research along the 110°E meridian off Western Australia as part of the second International Indian Ocean Expedition. The voyage is led by Professor Lynnath Beckley of Murdoch University and the research is supported by a grant of sea time on RV Investigator from the CSIRO Marine National Facility.

Notes: What a beautiful day! The samples are full of rock lobster larvae (phyllosoma) and two pygmy blue whales are belting out low frequency calls. Are they looking for a dinner date?

Transparent Marine Animals

By Andrew Jeffs

Living in the clear waters of the open ocean is a dangerous business when you are a small swimming organism because there is nowhere to hide from predators. However, many marine creatures have evolved a clever way to overcome the lack of hiding places. They have evolved to make their bodies transparent–so they are almost invisible in the seawater. Having a transparent body can also be handy if you are a predator, as it helps for sneaking up on your prey unseen. Many different types of open ocean organisms have evolved to become transparent including fish, crustaceans, worms, jellyfish and squid. In fact, in some areas of the open ocean, over 90% of the organisms larger than a full stop, are transparent. Despite the prevalence of this phenomenon, it is not well known how these organisms achieve transparency, particularly requiring body tissues that do not absorb or bend light. Whilst on board the RV Investigator in the Indian Ocean we are capturing different types of small transparent ocean organisms in nets and then using laser beams to measure how well their bodies match the optical properties of the surrounding seawater, in order to achieve transparency.

Overall, from the range of nets we are using (and a lot of microscope work), we can quantify zooplankton in the south-east Indian Ocean, process this information in food web analyses and include the data in models of ocean functioning.

Be sure to follow our daily Log from One Ten East at https://iioe-2.incois.gov.in or www.wamsi.org.au.

One Ten East Logs from the IIOE-2 voyage aboard RV Investigator will be posted on the WAMSI website during the month long voyage.

Log from One Ten East

The RV Investigator is currently undertaking oceanographic research along the 110°E meridian off Western Australia as part of the second International Indian Ocean Expedition. The voyage is led by Professor Lynnath Beckley of Murdoch University and the research is supported by a grant of sea time on RV Investigator from the CSIRO Marine National Facility.

Notes: The wind is calming and the sky clearing as RV Investigator traverses the Naturaliste Plateau. The scientists are happy as the sample jars are being dutifully labelled and filled.

Net Benefits

By Prof Lynnath Beckley

The word plankton is derived from the Greek word ‘planktos’ meaning drifter. Planktonic organisms generally drift in the ocean but some can undertake limited swimming to achieve vertical migration from the depths towards the surface to feed at night.

On our voyage with the RV Investigator, along the 110°E meridian in the south-east Indian Ocean, in addition to filtering very tiny organisms from water samples, we are using a wide variety of nets to capture plankton. These range from a tiny net with 20-micron mesh to catch phytoplankton to a large net with 1000-micron (=1 mm) mesh to catch larger zooplankton like krill, and the larvae of fish and rock lobsters.

One of the most historically significant nets we are using is the Indian Ocean Standard Net. We have a specially built replica of the original nets deployed by 14 different ships during the first Indian Ocean Expedition in the 1960s to compare the biomass (weight) of zooplankton in the surface 200m of the water column across the ocean basin. We are replicating these vertical hauls at the same time of the year and locations along the 110°E meridian to ascertain if there are any major differences in the biomass and composition of the zooplankton between the two voyages.

Dr David Tranter, formerly of CSIRO, and now well-retired, led the Australian plankton research during the first expedition and was responsible for numerous publications revealing the composition and abundance of zooplankton in the south-east Indian Ocean. He and his wife, Helen, even went to live in India for a while to train scientists at the Indian Ocean Biological Centre to process and identify the over 2000 zooplankton samples that were collected by nine countries during the first expedition.

Other equipment that is particularly useful for elucidating plankton is the EZ multiple opening and closing net. This consists of ten 500-micron nets in a big frame and they are electronically opened and closed at different depths in the ocean to sample the zooplankton. This enables comparison of the depths that various zooplankton reside during the day and night and allows us to quantify zooplankton abundance in different depth zones.

Overall, from the range of nets we are using (and a lot of microscope work), we can quantify zooplankton in the south-east Indian Ocean, process this information in food web analyses and include the data in models of ocean functioning.

Be sure to follow our daily Log from One Ten East at https://iioe-2.incois.gov.in or www.wamsi.org.au.

One Ten East Logs from the IIOE-2 voyage aboard RV Investigator will be posted on the WAMSI website during the month long voyage.

We have had another great day and have almost completed Station 2 on the 110 East line.

It has been a little cloudy and a little breezier today but the flesh-footed shearwaters are happily gliding just above the waves. Everyone is getting into the swing of having their nets deployed and retrieved and the sample jars are being dutifully labelled and nicely filled!

Log from One Ten East

The RV Investigator is currently undertaking oceanographic research along the 110°E meridian off Western Australia as part of the second International Indian Ocean Expedition. The voyage is led by Professor Lynnath Beckley of Murdoch University and the research is supported by a grant of sea time on RV Investigator from the CSIRO Marine National Facility.

Phytoplankton & Pigments

By David Antoine and Martina Doblin

Phytoplankton–the microscopic plants inhabiting the surface lit layers of the ocean are among the most diverse group of micro-organisms inhabiting the planet. They comprise eight main groups, have individual cell sizes from less than a micron to about one millimeter (see Figure below) and play various roles in the ecosystem. As they photosynthesize, they collectively represent the first link of the marine food web. All phytoplankton contain the pigment chlorophyll-a, which is measured to ascertain phytoplankton biomass. As well as chlorophyll-a, each phytoplankton group has other accessory pigments, which can be used to determine phytoplankton groups or size classes. Phytoplankton are also responsible for the transfer of carbon dioxide from the atmosphere to the deep layers of the ocean and ultimately the sediments of the sea floor.

Fig 1. An indication of the scale of phytoplankton size in microns relative to larger biota and recognisable land features in metres. Source : Finkel et al. 2010. J. Plank. Res. 32(1), 119-137.

Peta Vine (University of Technology Sydney) using the large filtration rack to separate phytoplankton and their associated pigments from water samples collected at different depths with the CTD Niskin bottles. Photo: Micheline Jenner.

After the water has been filtered the pigments remain on the small filter papers and here, Peta Vine (University of Technology Sydney) points to a filter with pigments, in comparison to the adjacent clean filter. Photo: Micheline Jenner.

Examples of phytoplankton from the south-east Indian Ocean. Top: A diatom chain clearly showing green chlorophyll and a stunning Chaetoceros sp. photographed under a microscope from water samples collected from the RV Investigator on the 110°East line. Photo: Dr Peter Thompson.

Be sure to follow our daily Log from One Ten East at https://iioe-2.incois.gov.in or www.wamsi.org.au

One Ten East Logs from the IIOE-2 voyage aboard RV Investigator will be posted on the WAMSI website during the month long voyage.

The wind and swell was up a little yesterday. This seemed to keep a few participants in their bunks a bit longer in the morning but by evening, most were feeling fine again. Fortunately, this was a transit day and the weather has improved as we have begun the first station on 110 East meridian. 

The yellow-nosed and black-browed Albatross were soaring beautifully in the fresh 20-30 kts and all is well on the fine RV Investigator.

Log from One Ten East

The RV Investigator is currently undertaking oceanographic research along the 110°E meridian off Western Australia as part of the second International Indian Ocean Expedition. The voyage is led by Professor Lynnath Beckley of Murdoch University and the research is supported by a grant of sea time on RV Investigator from the CSIRO Marine National Facility.

Indian Ocean Nutrients

By Dr Peter Thompson

The CSIRO scientists involved in the original International Indian Ocean Expedition during the 1960s described it as a desert. Huge regions of the Indian Ocean had almost no plant life. The thousands of species and billions of microscopic plants found in most oceans were largely absent. These plants, just like the ones in your garden or paddock, require nutrients to grow. In the garden, we add fertiliser with these nutrients, particularly nitrogen and phosphorus, to ensure a successful crop. These nutrients are in very short supply in the surface waters of the Indian Ocean.

To find out how much nutrient is present it is necessary to get samples of water from deep in the ocean. Special tubular containers, called Niskin bottles, located on the CTD are sent down with the ends open (can you guess why?) on a wire to depths of 5000 m where they are electronically triggered to close and collect the samples. Several hours later when the bottles are winched back to the surface the chemists can start the process of measuring the nutrients. To do this we use sophisticated on board instruments and internationally agreed high precision methods. It is a bit like a blood test to check the health of the ocean.

Dr Peter Thompson (CSIRO) and Dr Karlie McDonald (CSIRO) take water from two of the 36 Niskin bottles in the CTD rosette, to analyse nutrient levels of the south-east Indian Ocean. Photo: Micheline Jenner.

In the nearly 60 years since the first International Indian Ocean Expedition we have learned much about the cycling of nutrients in the ocean. A thousand meters below the surface where the water is only 5°C, nitrate is plentiful (Figure 1). However, enough light for plants to grow only penetrates to about 100 m where nitrate is particularly scarce. Processes that we did not understand in the 1960s, we now know are changing the supply of nutrients to the surface and some parts of the Indian Ocean are becoming more productive (more nutrients = more plants = more fish) while others are less productive. On this second voyage (IIOE-2) we are exploring how nutrient supply has changed over the last six decades in the Indian Ocean offshore of Western Australia.

Figure 1. Plots of temperature, light and nitrate in the upper water column. Temperature declines slowly with depth but light disappears dramatically at about 100 m depth in the open Indian Ocean. The amounts of nutrients, such as nitrate, are very low until around 200 m depth. Data courtesy of CSIRO.

In particular, we are looking for evidence of changes in nutrients within the deep ocean as a result of changing global ocean circulation patterns. This mix of deep and shallow circulation brings deep nutrients from the North Atlantic and some nutrients from the Pacific into the Indian Ocean (Figure 2).

Figure 2. The global ocean and its thermo-haline circulation bring nutrients from deep regions in the North Atlantic and the surface of the Pacific into the Indian Ocean. Image courtesy of NASA/JPL.

These processes are changing faster than ever due to global warming. In addition, we will investigate nutrient recycling near the surface of the ocean. There, an expanding area of low oxygen is impacting on the microbial processes that recycle organic matter. Understanding the impacts of these changes on the ecology of the Indian Ocean is one of the key goals of the 110° East voyage.

Dr Peter Hughes (CSIRO) in the hydro-chemistry lab aboard RV Investigator uses sophisticated and precise equipment to measure chemical composition of the water sampled by the CTD. Photo: Micheline Jenner.

Be sure to follow our daily Log from One Ten East at https://iioe-2.incois.gov.in or www.wamsi.org.au .