[Coral-List] Orinoco River Plume in the Caribbean

Nelson Melo nelson.melo at noaa.gov
Wed Apr 29 17:17:36 EDT 2009

>Originally Sent: Wednesday, April 29, 2009 1:41 PM
>To: Frank Muller-Karger; Chuanmin Hu; Inia Soto; Peter Ortner; Thomas Lee
>Cc: Georgina Bustamante; ...

The NOAA RV Nancy Foster conducted an oceanographic and ichthyoplankton survey 
in the US and BVI, and Leeward Islands from April 7-21st, 2009. During that 
time frame we encountered the Orinoco River plume water. 

Below is a short description and an attached image showing the extent of the 
plume in mid April. We will have a more extensive report with mapped surface 
features available at the end of the week. Please contact Dr. Trika Gerard 
(trika.gerard at noaa.gov) and/or Dr. Libby Johns (Libby.Johns at noaa.gov) for 
additional information.

/ / April 19, 2009 Hello from the Caribbean Sea. Just wanted to share with you 
an unusual event in the area around US Virgin Islands and Puerto Rico we are 
experiencing on the current USVI cruise. The first week of the cruise 
oceanographic conditions were normal for the region, typical oligotrophic 
waters with low chlorophyll values throughout the region.  However, in the 
second week, the Orinoco river plume had pushed up into the region and now 
extends north of the Virgin Islands. This river plume water has decreased 
salinity with a very strong chlorophyll and colored dissolved organic matter 
(CDOM) signature. The low salinity, high chlorophyll layer is present at the 
surface and extends approximately 20 meters in depth. Plankton volumes are at 
least 4 times higher in the plume, compared to samples collected outside the 

I [can share with 'coral-list' subscribers] a MODIS color image showing the 
extent of the Orinoco river plume. Sampling stations are plotted in white. 
The Chl a and CDOM are scaled with red showing the highest and blue the 
lowest. Although this is a yearly event, the Orinoco outflow rarely reaches 
this far north. [Please contact Nelson directly for this plot! -eds.]

When we first started tracking the plume, it appeared to move north and then 
be advected west to Saint Croix and Puerto Rico by a cyclonic eddy. 

The high chlorophyll water subsequently wrapped around the western end of 
Saint Croix, and then north to Saint Thomas. At the same time another branch 
moved north along the Leeward Islands, and currently extends north through 
the Anegada Passage.

We are presently mapping the extent of the plume around Saint Croix. The 
maximum chlorophyll is at 20 meters depth instead of at the surface and 
appears to extend well inshore onto the reefs. We have reports from fishermen 
of ‘green water’ from St. Thomas and Puerto Rico as well. The impact of this 
event on the ecosystem is as yet unknown.

Trika Gerard, Estrella Malca, Barbara Muhling, Akihiro Shiroza, Francisco
Fuenmayor, John Lamkin - Southeast Fisheries Science Center 

Libby Johns, Ryan Smith, Nelson Melo, Grant Rawson- Atlantic Oceanographic
and Meteorology Laboratory

><((((º>¸.·´¯`·.¸¸.·´¯`·..¸¸ ><((((º>`·.¸¸¸.·´¯`·.¸¸

Nelson Melo
Physical Oceanography Division
4301 Rickenbacker Causeway
Miami, FL 33149-1026, USA
Ph: 305-361-4329
Fax: 305-361-4392
E-mail: nelson.melo at noaa.gov

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