Talk About It!

Sponge research

Asked by Michelle from Kapiolani Community College on Sep 26, 2002.
Are you going to take samples of the unusual sponges you saw and conduct reserach on them?

Answered by Rachel Shakelford, Hawaii Undersea Research Lab (HURL) on Sep 27, 2002.
We did not take any samples of sponges on this particular trip. One of the problems is that there is no time to deviate from protocol to take samples during a transect, where the primary objective is to count everything. Once the transects are finished, samples may be collected, but they are limited to what can be found nearby. The observers may have seen something unusual druing the transect, but once they have time to take samples there may be no such organisms around. We did take samples of a few corals, a crinoid, a few small crabs, and a cone shell that we weren't able to identify with certainty. Those samples will be sent off to experts so that their identities may be confirmed.

Are there more fish in deep or shallow areas?

Asked by Michelle from Kapiolani Community College on Sep 28, 2002.
In the research journal ROV DIVE 9/17/02, you saw more fish in the deeper area of the ocean (800m) than at 150-200m. Why did this occur? Is this the norm?

Answered by Rachel Shakelford, Hawaii Undersea Research Lab (HURL) on Sep 29, 2002.
That is a very good question, and there is no easy answer. The main thing to realize is that fish distribution is typically very patchy. We may have just happened upon a low density area in 150-200 m and a relatively high density area at 800 m. If our dive site had been different, we may have seen something different.

Another thing to keep in mind is that the types of fish that we see at 800 m are very different than those at 150-200m. The ideal fish habitat has lots of nooks and crannies for fish to hide in. At the site you refer to, it was quite sandy in the 150-200 m range and there weren't many hiding places for fish. Also, we noticed quite a few Kahala (Seriola dumerili) at most locations throughout the cruise. The Kahala are very efficent hunters (we saw them attack several small fish), so they may keep the numbers of other fish low in some places.

In the 150-200 m range, photosynthesis (plant growth) still occurs, whereas it does not at 800 m due to insufficent light. So shallow water fish are adapted to eating different kinds of food than deep water fish are. Perhaps this area lacked sufficient food in the shallower area, yet contained more down deep. There are several different actors that contibute to low numbers of fish in some areas, so it impossible to give you a simple answer!

Black smokers and undersea maps

Asked by Michelle from Kapiolani Community College on Sep 28, 2002.
Did you see any black smokers (hydrothermal vents) on your dive, and if so, were any animals present?

Answered by Rachel, HURL on Sep 29, 2002.
Hydrothermal vents only occur in certain areas of the ocean where there is volcanic activity at the sea floor. If you look closely at a map that shows the bathymetry (terrain of the ocean floor) of the Pacific Ocean, you can see some deep trenches (for example, off the Aleutian Islands and Tonga) and some ridges or mountains (for example, off South America and Washington State).

Trenches occur where one plate is going under another, and ridges occur where two plates are moving away from each other. Becuase of the interaction between plates at the ridges and trenches, volcanic activity and hydrothermal vents occur at these plate boundaries. The third type of hydrothermal activity occurs at mid-plate hotspots, like the one that created the Hawaiian Islands.

So, to get to your question, there are no hydrothermal vents around the NWHI because they are in the middle of the Pacific plate, far away from any hotspot activity. There are hydrothermal vents at Loihi, the seamount southeast of the Big Island, since it is right over the Hawaiian hotspot. Black smokers in particular occur only at some (not all) hydrothermal venting sites. For example, there are no black smokers at Loihi where the venting is not quite as hot as it is in other areas. Black smokers also occur at hydrothermal vent sites on the Juan de Fuca ridge (west of Washington) and on the East Pacific Rise (west of South America), among other places. For bathymetry maps, click here. Look at the North Pacific, Central Pacific and South Pacific maps separately for the most interesting results.

Ocean temperature and pressure

Asked by Michelle from Kapiolani Community College on Sep 28, 2002.
What is the temperature and pressure of the different zones of the ocean?

Answered by Rachel, HURL on Sep 29, 2002.
The temperature and pressure of the ocean depend largely on depth. For every 10 meters of water, you have one atmosphere of pressure (14.7 psi or pounds per square inch). At 400 m, where our deep transects were conducted, the ambient pressure is the equivalent of 41 atmospheres (40 from the water above the sub and one from the actual atmosphere). At 2000 m, the maximum operating depth of HURL's submersibles, the ambient pressure is 201 atmospheres. How much is that in pounds per square inch? We often draw pictures on styrofoam cups and bring them down to the bottom of the ocean with the submersible. What do you think happens to them? Why?

Answer: They shrink. As the pressure increases, the air pockets within the styrofoam are compressed. The air is effectively pushed out of the styrofoam cells so that the cup does not expand again as the pressure decreases upon ascent. Feel free to send us your own personalized cups for shrinking! The kind without bands around them work best.

The temperature of the ocean at sea level around Hawaii is about 25 or 26 degrees Celsius. At 200 m, the temperature is around 15 degress C and at 400 m it is about 7 degrees C. The deeper you go, the colder it gets. Below about 2000 m, the temperature is about 2 to 3 degrees C. Because the water surrounding the sub is quite cold, even at 400 m, the pilot and the observers on board take warm clothes and socks with them. Even those who like it a little chilly are sure to take warm clothes, because if there were an emergency and they were stuck down there for a while, they would get quite cold without a sweater!

Keep up the good work!

Asked by Anonymous on Oct 3, 2002.
I understand that the scientists work hard to gather information that will long benefit us. We need ongoing studies by your organization! I don't think any of this is possible without the hard work and knowledge of the captains and crew members of the research vessels. Hats off to the workhorses behind the scenes!

Answered by the NOW-RAMP Crew on Oct 4, 2002.
Many Mahalos!

A fish to write about...

Asked by Alex from People to People on Jan 26, 2005.
Which fish of hawaii do you think are the most important to include in a report? Is pufferfish the real name for the fish that expands?

Answered by Paulo from the University of Hawaii on Feb 6, 2005.
Aloha, Alex. The fishes that expand are many, and they are grouped into two families, with the common name of "pufferfishes" (with bristly skin) and "porcupinefishes" (with sharp spines). Both share the common defensive strategy of "puffing up" their bodies to make themselves very difficult to eat.

About your first question, it depends on what type of report you'd like to write, and your audience. If your audience is not familiar with the fishes from the Hawaiian islands, let me suggest the state of Hawaii official fish, the Humuhumu-nukunuku-a`pua`a (a trigger fish). Because of its appearance, significance, and behavior, you might find it interesting writing about it.

I hope this helps.

Paulo