Midwater Ecology Fall 2013 Expedition

November 7-13, 2013

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.

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.

In addition, the MBARI research team will be joined by a group of husbandry staff from our sister organization—the Monterey Bay Aquarium. The Monterey Bay Aquarium is interested in the potential for creating an exhibit of deepwater organisms and will be working closely with MBARI on organisms such as jellies and cephalopods.

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Last day

We have had an amazingly productive cruise. On day one, we assembled a long list of target species and we managed to check almost every single species off our list.

Stayin' alive!

On this expedition, Stephanie Bush is working with cephalopods. Stephanie is a postdoctoral fellow at MBARI working with the Monterey Bay Aquarium husbandry staff in preparation of a cephalopod exhibit set to open in April 2014.

What's for dinner?

Today we spent many hours looking at not much more than marine snow, but we were rewarded for our patience. We witnessed feeding interactions of deep-sea animals, including a squid attacking an owlfish.

On the hunt for deep-living animals

Today we had another deep dive, reaching 2,000 meters (6,561 feet), searching for deep-living animals that we rarely get a chance to see. We also had the chance to collect some of our target animals, like Octopoteuthis deletron.

Expansion of the oxygen minimum zone

In yesterday's blog, I talked about the importance of studying midwater communities and the oxygen minimum zone (OMZ). I also mentioned that as the ocean warms due to climate change, OMZs are expanding. Why is that, you might ask? There are a few key factors in this expansion.

Why study the midwater and what the heck is OMZ?

We use this term “midwater” to describe the community of organisms that live in the pelagic zone. The pelagic zone can be described as any water that is neither close to the bottom nor near the shore.