Midwater Ecology 2012 Expedition

July 13-19, 2012

The midwater ecology group is documenting the effects of declining oxygen concentrations on midwater communities, and has spent thousands of hours surveying and describing the deep waters of the ocean. On this week-long research cruise, the midwater ecology research team, headed by Dr. Bruce Robison, will be examining the physiological characteristics of midwater animals relative to the expanding oxygen minimum zone.

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In order to document the effects of declining oxygen concentrations on midwater communities, the midwater ecology research group has conducted approximately one remotely operated vehicle (ROV) dive per month, compiling a time series which measures the identity, abundance, and vertical distribution of the constituents of the midwater fauna at specific sites. The results of the time series demonstrate that several species have already been displaced by the expanding oxygen minimum zone (OMZ). OMZs are depths, typically 300 to 1,000 meters below the surface, where oxygen concentrations are already quite low in many parts of the world’s oceans.

The midwater team will be examining the physiological characteristics of midwater animals relative to the expanding OMZ. This research utilizes the midwater respirometry system (MRS), an instrument which gathers oxygen consumption measurements in situ, to gauge the metabolism of animals without subjecting them to the stresses of decompression during transport to the surface. Data provided by the MRS helps to determine the oxygen level at which each species switches from “regulation” to “compensation.” Once these oxygen levels are known for a number of species, the future of how expansion of the OMZ will change the spatial composition of the midwater community can be predicted, as well as the ecological implications of such changes.

Another focus on this expedition will be age determination of squid and other deep-sea invertebrates. Despite their great importance in oceanic ecosystems, the life spans of deep-sea squids are simply not known. If they are like their shallow-water relatives, chances are their lives are quite short—perhaps a year or two years at the most. If they are like some other deep-living animals, their lives may be quite long. Henk-Jan Hoving, a post-doctoral fellow in the midwater ecology group has developed an experimental program of both laboratory and in situ research that will chemically “mark” increments in the deposition of squid statoliths (like the ear-bones of fish). Using the marks as temporal reference points, the pattern of deposition should allow him to determine the age of any squid, based on the number of increments (like tree rings). There will probably be differences between species, between sexes, between habitat depths, and between good years and bad years; but this technique, once developed, promises to be a powerful new diagnostic tool for deep-sea ecology.

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MBARI researchers Bruce Robison and Kim Reisenbichler used video taken by unmanned, undersea robots called remotely operated vehicles (ROVs) to study barreleye fish in the deep waters just offshore of Central California. At depths of 600 to 800 meters (2,000 to 2,600 feet) below the surface, the ROV cameras typically showed these fish hanging motionless in the water, their eyes glowing a vivid green in the ROV’s bright lights. The ROV video also revealed a previously undescribed feature of these fish–its eyes are surrounded by a transparent, fluid-filled shield that covers the top of the fish’s head.

The vampire squid (Vampyroteuthis infernalis) lives in the deep ocean, home to the largest ecosystems on our planet. A “living fossil,” this animal has remained relatively unchanged for hundreds of millions of years. The deep ocean contains what may be the greatest number of animal species, the greatest biomass, and the greatest number of individual organisms in the living world. Humans have explored the deep ocean for about 150 years, and most of what is known is based on studies of the deep seafloor. In contrast, the water column above the deep seabed comprises more than 90% of the living space, yet less than 1% of this biome has been explored.

Logbook

Seeing in the dark

The orange dot on the jelly Haliscera conica is a parasitic amphipod. We collected this jelly and it's stowaway and found that it had eaten a large hole from the jelly's bell.

Important observations

This morning we started our dive at 6:30 a.m. and searched for Sergestes similis shrimp for a new series of Midwater Respirometry System (MRS) experiments...

A squid's diet

Over the years of MBARI's ROV observations, many squid species have been encountered with food in their arms. Yesterday, we observed a Gonatus onyx with a fish in its arms

Science never sleeps

While waiting for our second ROV dive, we saw several humpback whales around the ship...

Searching the deep sea

During the dive we collected many different animals such as ctenophores, amphipods, squids, and worms. We spent a couple of hours slowly flying up and down looking for vampire squids...

Our first dive

Our first mission was to deploy the Midwater Respirometry System at 320 meters (1,050 feet) depth.