[Coral-List] Question about a macro algae species seen on reefs in southern Cat Island, Bahamas

Carrie Vanessa Kappel ckappel at stanford.edu
Thu Feb 23 12:49:05 EST 2006

Hi Rick,

>From your description, it sounds like what you were seeing was likely
Microdictyon marinum, which has been observed to have strong summertime
blooms on reefs in The Bahamas. We also saw high densities of Microdictyon
during our surveys on North Andros in July 2002 and San Salvador in July
2003. It's not clear why this seaweed has increased so dramatically on
Bahamian reefs in recent years, but I'd guess it's due to an interaction
between nutrient runoff and grazing. Brian Lapointe and coauthors suggested
that Microdictyon marinum might benefit from submarine groundwater
discharge, whereby nutrients (in this case dissolved inorganic nitrogen)
from land are transported to reefs offshore via groundwater fluxes through
porous limestone (Lapointe et al. 2004. J. Exp. Mar. Biol. 298:275-301).
The Littler and Littler Caribbean Reef Plants book has a nice picture of
this species and others with which it might be confused.


Carrie Kappel
Postdoctoral Fellow
National Center for Ecological Analysis and Synthesis
University of California Santa Barbara
735 State Street, Suite 300
Santa Barbara, CA 93101

kappel at nceas.ucsb.edu
805.966.1677 w
805.892.2510 f
831.869.1503 m

Permanent email address
Carrie.Kappel at alumni.brown.edu


Message: 5
Date: Tue, 21 Feb 2006 13:34:49 -0500
From: "Rick Sanders" <ricksanders at comcast.net>
Subject: [Coral-List] Question about a macro algae species seen on
	reefs in	southern Cat Island, Bahamas
To: <coral-list at coral.aoml.noaa.gov>
Message-ID: <004b01c63715$7fa4b760$650da8c0 at manta>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";

Dear Listers,

I have spent many hours pouring over photos of macro algae trying to find an
image of the algae that I saw overgrowing corals on many of the reefs I
dived off the southern end of Cat Island in the Bahamas. I have been unable
to find an image of anything close to what I observed there in July 2003.

Description:  It appears to be a filamentous type algae on a greenish brown
color that appears to be made up of netting (the filaments cross each other
in a more or less orthogonal orientation) the netting appears to shaped into
more or less spherical or roundish mats.  The filaments are aprox 2-3 mm in
width. The mats are easy to dislodge from their substrate and feel as if to
crinkle when crushed under pressure with ones hand.  They are overgrowing
many types of corals in shallow and deeper reefs.

I am concerned about the impact that this algae might have on the reefs
there and want to get more information on what is happening there and the
first logical step is to identify it if possible. If anyone has seen what I
am describing and has some photos of this type of algae please send me a
copy or link.

Thanks very much in advance,

Best regards,


Rick Sanders
Deep Blue Solutions
Media, PA
ricksanders at comcast.net


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