There are several kinds of nets and other equipment that the SEAPLEX scientists will be using. In our relatively few post to this point, several have already been mentioned, so I thought that it would be nice to have a little clarification. These pictures are not from the SEAPLEX cruise, but from CalCOFI cruises to the California Current. Here is a quick description of the major pieces of equipment that will be used during the cruise.
CTD (Conductivity, Temperature, and Depth) Rosette
The CTD rosette is one of the most common pieces of oceanographic equipment. It allows us to see the vertical structure of the water and to collect water samples from various depths. It is composed of an array of sensors surrounded by a number of bottles. The sensors include pressure (depth), temperature and salinity (conductivity), which are used to determine density. Depending on the particular machine, there are also sensors to measure chlorophyll fluorescence (a proxy for phytoplankton abundance), nitrate, oxygen, and light levels. The bottles are all open when the instrument is deployed, and they are closed at various depths on the way up. The water collected in these bottles can be used to look at nutrients, bacteria, phytoplankton, and protists from different depths.
CTD being deployed
The bongo nets are probably the most common way to sample zooplankton. They are paired mesh nets attached to a metal frame, and some think that they resemble bongo drums. There are collection receptacles, called cod ends, at the end of the net where the zooplankton are concentrated. All of the water and particles smaller than the holes in the mesh pass through the net, and everything larger than the mesh is funneled into the cod end. The net is towed obliquely (in a V shape) so that all depths (except the deepest depth) are sampled twice. Most bongo tows go down to 200m depth. There are flow meters in the mouths of the nets so that the volume of water filtered can be calculated accurately.
Bongo nets being deployed
The manta net is used to sample zooplankton that are at or near the sea surface. It is a single mesh net with two large wings that extend out on either side of the mouth of the net. The wings help the net to stay at the surface. Surface zooplankton are funnelled into a cod end in the same manner as the bongo nets.
Manta net sampling in the California Current
The Oozeki trawl is another type of net, and works the same way as the bongo and manta nets. It is used to sample small fishes. The Oozeki is a much larger net (about 6 feet tall) than either the bongo or manta nets. It also has a larger mesh size than either of the other types of nets that will be used on the SEAPLEX cruise. The larger mesh means that most zooplankton pass through the mesh, leaving fish and larger zooplankton such as jellyfish and squid. The Oozeki is towed between about 400m and 2000m deep.
Getting ready to deploy the Oozeki trawl
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[...] Vampire Squid This vampire squid was caught in today’s IKMT. [...]
By: Vampire Squid « SEAPLEX on August 4, 2009
at 8:55 am
[...] sampling equipment includes the manta net (water surface), bongo nets (below surface) and IKMT (mid water trawl). All three of these pieces [...]
By: SEAPLEX Day 3 « SEAPLEX on August 4, 2009
at 10:52 am
[...] hope you are following along on the SEAPLEX blog. A great post about the kinds of gear used in open-water oceanography. But better than the gear itself is a Vampire Squid caught in that [...]
By: Seeking the Science of the Pacific Ocean Garbage Patch | Deep Sea News on August 4, 2009
at 5:25 pm
[...] manta tow to collect surface [...]
By: SEAPLEX Day 4 Part 1 « SEAPLEX on August 5, 2009
at 12:56 pm
what is the normal distribution of plastic particles in the oean outside of this area?
By: Jehu Hand on August 6, 2009
at 5:01 pm
No one really knows! The SEAPLEX cruise is doing daily sampling along their transect into the gyre. This will give them an idea of how the distribution in the abundance of plastic particles changes as you move away from shore and towards the gyre.
By: Alison Cawood on August 7, 2009
at 9:51 am
[...] Stillinger is always happy to assist in deploying the CDT around 3:30 AM in the [...]
By: SEAPLEX Day 7 « SEAPLEX on August 8, 2009
at 7:18 pm
[...] Institution of Oceanography at UC San Diego resident marine technician, assists in the retrieval of bongo nets. Durham coordinates shipboard activities between the science team and New Horizon’s [...]
By: SEAPLEX Day 9 Part 1 « SEAPLEX on August 10, 2009
at 10:59 am
[...] 1,000 km (620 miles) due west of the first station where we found plastic pieces in the surface manta tows. We have now found plastic in every tow, 28 out of 28 manta tows since the one on Aug. 6, when the [...]
By: SEAPLEX Day 9 Part 2 « SEAPLEX on August 10, 2009
at 11:19 am
[...] about 14:00 (2 pm), there is a manta net tow to collect material from the surface of the water. At 14:30 (2:30 pm) there is a CTD cast to see [...]
By: SEAPLEX Day 10 Part 2 « SEAPLEX on August 11, 2009
at 2:32 pm
[...] as people start wrapping up their respective research efforts. We will continue to conduct five manta tows daily as weather permits but almost all other scientific instruments were hung up to dry out [...]
By: SEAPLEX Day 17 Part 1 « SEAPLEX on August 18, 2009
at 9:45 am
[...] blogs, I’m sure you have seen mentioned several times our various standard sampling instruments—the manta net, Matsuda-Oozeki-Hu trawl (aka Oozeki trawl), bongo net, and CTD. I am sure that you have read some [...]
By: SEAPLEX Day 18 Part 1 « SEAPLEX on August 19, 2009
at 10:32 am
I love cruise shipping and cruise ships at all. This is great way to spend your vacation and to have great time around the sea and the ocean.
By: Oasis of the Seas on August 10, 2010
at 8:28 pm