Wednesday, July 1, 2009

Middle of 4th day update.

Here we are at about the midpoint of the research cruise. The weather has been incredible with mostly calm seas and almost no rain. Even on the one day it got a little breezy, everyone had their sea legs already and there were no reports of mal de mer.

As usual, we are taking lots and lots of water samples to characterize the continental shelf waters off the coast of Louisiana. This trip is particularly interesting because it has timed to coincide with the occurrence of a "dead zone" in this area almost every summer. The dead zone develops from a combination of processes; the strongest include 1) a thin layer of fresh water from the rivers which floats on top of the sea water and prevents oxygen from mixing in; 2) decreased mixing because of low winds this time of year, and 3) a process called "eutrophication" which occurs when plankton grow very rapidly when they have an abundance of food/nutrients. The growing plankton aren't the problem, themselves. The real problem is that they only live for a few days, so even as the plankton population is increasing, more and more of them are dying as well. When they die, they sink, and as they sink, other organisms (especially bacteria) break them down, recycling the nutrients. As they do so, they use up oxygen from the water column. And if the conditions are right, the dissolved oxygen concentration can drop low enough that fish and other critters can't get enough oxygen, and they either die or leave the area. On several stations, now, we have seen very low oxygen concentrations in the bottom water, meaning that we should be in for a pretty strong dead zone off the Mississippi River this summer.

This trip, I brought along three helpers from USF St. Petersburg. Alanna Lecher (who participated in the 1st cruise), Iuri Herzfeld (who participated in the second cruise) and Lisa Vlaming. Lisa is new to the lab, and I'm glad she could come along to get some experience. Check out their profiles on the USF website: MAG-Mix home

We have a busy schedule this trip. In addition to the water samples, we have an ambitious plan to get lots of mud samples to analyze the sediments and the pore water. We've done a few cores on the past trips, but we're hoping to get really good coverage of the study area.

I'm having trouble uploading images (sorry), but may be able to post some on facebook

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Anonymous said...

At least you guys are having nice weather it has been raining here everyday. Have you had any issues on board as of yet?

Jade said...

Hi Jim (and everyone else!), I'm doing field work of my own right now. I'm about halfway between Washington and Alaska collecting zoo- and phytoplankton samples from a large inlet on the BC coast. This inlet used to have the biggest salmon run in the area, but has dropped off drastically in the past couple decades. Juvenile salmon eat plankton, so we're studying it to see if there are any population changes contributing to the salmons' decline.

Have fun playing with mud!

britney said...

Oops you got breezy!!!!
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