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March 26, 2003: Leg 3, Day #15

Today's update is provided by Rebeca Gasca from ECOSUR. Rebeca is one of the Mexican collaborators for the Gulf Expedition.

Alarcon Seamount

Mar26_ss_Rebeca052.jpg (32937 bytes)Soy Rebeca Gasca, la observadora mexicana participante en este crucero, además trabajo con los grupos de sifonóforos y anfípodos. Me siento muy afortunada de estar aquí y tener esta oportunidad única de estar en un barco con muchos de los instrumentos mas avanzados y sobre todo, el sumergible ROV, que permiten estudiar organismos en su medio natural, desde la superficie, hasta varios cientos o miles de metros de profundidad.  

Today we traveled 48 miles to the south of Pescadero basin and headed towards Alarcón Mar26_spiders.jpg (45478 bytes) seamount. As we dove, an echosounder registered the topography of the scattering layer and, with the ROV Tiburon, we went in search of the organisms that produced the layer. Despite several attempts going up and down through the layer, which was approximately 250–400 meters deep, we could not identify the fauna. They seemed to be avoiding the vehicle. That made me wonder how much else we are missing in this vast ocean when we are able to look at it only in such small pieces. 


Some organisms we did see include medusae, siphonophores, appendicularians, small fishes, and pteropods. At about 550 meters, we observed another scattering layer with the echosounder, but not the animals that caused it. In both cases fish probably caused tMar26_1.jpg (18407 bytes)he scatter because they are big enough to do so and fast enough to avoid the ROV. We observed a fair number of individual myctophids at ~550 meters. After that, when we reached the bottom at approximately 1300 meters, it looked more diverse than in the sites we visited before.
 

I have seen living animals that before I had only seen preserved. To see them alive has been breathtaking—I enjoy watching the screens for hours with all that the ROV cameras are registering, and as always, I am looking forward to seeing them on board. 

One of the most interesting things that we have found (and one of my dreams come true!) was a siphonophore of the family Rhodaliidae (see above and left), probably Stephalia corona. There are no previous reports of this animal in Mexico, and it will be interesting to know (for sure) who it is and more about its characteristics and distribution. 

Some of these organisms are so fragile. Just a touch with a finger would produce the disintegration of organisms like Lilyopsis, the siphonophore found on one of the blue water SCUBA dives. I wanted to include a photograph, but it disintegrated before we could take one. 

Mar26_3.jpg (36021 bytes)Another great thing for me was to snorkel in the middle of el Golfo (yesterday) and to feel as small and as much a part of nature as all the brilliant blue Sapphirina, stinging Athorybia (a small siphonophore-see below), and bleeding (not really) Eurhamphea ctenophores surrounding me. 

Tiburon came up early from today’s dive. We monitored the humidity increasing in a major component of the ROV, the VME can. When it rose quickly from 15% to almost over 20%, the pilots began to fear a leak, and we came up. So far they have found water in one cable, which can be replaced. If they do not find water in the can itself, we will be in the water again tomorrow just a little later than usual. The pilots are very good—some dives have been delayed due to equipment problems, but we have always been able to dive and will keep our fingers crossed for tomorrow.  

Agradezco a todo el personal del barco, tanto de la tripulación, como del equipo cientifico por las deferencias que han tenido para conmigo y especialmente a los Doctores Bruce Robison y Steve Haddock por invitarme a participar en este crucero que siempre recordaré como una de las experiencias mas enriquecedoras de mi vida.

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