Ask an Explorer

Below are questions from the public and answers from the Expedition to the Deep Slope team.

Questions from:  Liz Baird, North Carolina Museum of Natural Sciences

I was intrigued by the sea urchins shown plowing through the mud at site AT 340. Could you identify the species of urchin? It is difficult to tell whether they look more like pencil urchins with thicker spines or the more typical "green" urchin with many smaller spines. I'm assuming that the trek through the mud is a feeding behavior. If so, what are they feeding on? I am also wondering if the large aggregations of urchins might be a reproductive strategy. Have other missions documented this gathering of sea urchins? Is it seasonal or is it simply related to having a large quantity of food concentrated in one area?

Answer from: Bob Carney, Louisiana State University

The sea urchins we found are in a group commonly called "heart urchins," since the body is somewhat more heart-shaped than round. More formally, they are "spatangoid" urchins. Determining the exact genus and species will require examination by an expert. I suspect, however, that they are in the genus Brissopsis. The more familiar urchins are termed "regular" urchins in the sense that they are fairly round. Pencil urchins and green urchins are both regular urchins and usually are found on top of sediment or rock, feeding on attached material and fine particulates. In contrast, heart urchins burrow in organic-rich muds. They ingest organic particles. Heart urchins are common in shallow water but go unseen, burrowing in the sediment. There are deep-sea heart urchins, but until our discovery, little has been noted about their ecology. Perhaps all or some are associated with seeps or seep-like environments.

Aggregation in sea urchins is an often-reported behavior. It probably has multiple functions and may benefit reproduction. Most urchins shed gametes (cells that can fuse with other cells in reproduction) into the water, and an aggregation might experience greater fertilization success. The simplest explanation, which has been tested in shallow-water experiments, is that urchins gather where there is an abundance of food. In the case of our seep heart urchins, hydrocarbon seepage produces high microbial biomass in the sediments. Perhaps it is this bacterial material that attracts and is consumed by the urchins.

Questions from:  Liz Baird, North Carolina Museum of Natural Sciences

Having had the incredible pleasure of exploring some deep sites on the Atlantic side, I am curious about bioluminescence on the Gulf side — especially near the seeps. Have the researchers found any bioluminescent organisms near the seep (or have they even looked)? I know bamboo coral is bioluminescent, but that would arrive long after the seep stopped "seeping." Are any of the tubeworms, mussels, or clams bioluminescent? Is there any bioluminescent "marine snow" around the seeps?

During the Deep Scope expedition of 2004, Charles Matzel of Physical Sciences Inc. discovered a fluorescent shark and Mike Matz from the University of Florida discovered that methane hydrates are brilliantly fluorescent. Are you using the fluorescent characteristics to find methane hydrates and seeps at all? If so, is there a special light on the submersible?

Answers from: Chuck Fisher and Harry Roberts, Co-Chief Scientists; and Jeremy Potter, Office of Ocean Exploration

Great questions! Seep tubeworms, clams, and mussels do not bioluminesce. However, there is a bioluminescent pelagic sea cucumber that has been spotted around seeps. Oil does, in fact, fluoresce under ultraviolet light. If scientists took an ultraviolet light down to a hydrocarbon seep and turned off the regular submersible lights, they could find areas where oil seeps exist. Dr. Harry Roberts considered doing this years ago, but geologists had become so effective at finding hydrocarbons through other means that they never tried it. We have not added special lighting to the submersible to identify seeps or associated organisms during this cruise.

Question from:  Ryan

If you find a new animal will you bring it to a lab to study it?

Answer from:  Erik Cordes, Ecologist

Thanks for your question. First of all, I very much hope that we do find some new species of animals on this cruise. With all of the new sites we will be visiting, I think the chances are very good. The whole process of finding and describing new species can often take a long time. We first try to identify each animal that we collect while we are on board. Members of our team out here at sea have been working in this area for over 20 years, so we can identify most of things we collect. If there is something that we cannot identify, we will send it to one of the experts in that kind of animal. This person will carefully examine the specimen and will tell us what species it is (if it is already known) or they will describe it as a new species. If we're really lucky, they might even name it after one of us! Thanks again for the question, and keep checking out the Web site to see all of our new discoveries.