Gulf Coast Research Lab  -  Marine Botany

Fig. 1: Hard at work

Chandeleur Islands Seagrasses -
Post Katrina Assessments

Sampling was conducted on shallow nearshore seagrass beds. Access by boat was restricted due to the shallow depths (1-4 ft). We had lots of equipment: transect tapes, 6” corers, quadrats, sampling bags, sieves, underwater camera, GPS, datasheets, snorkel gear; so we ended up using one of the R/V McIllwain’s life-rafts to help us out—it worked great!

 

Below the sampling images are some pictures of the seagrass condition at the seven sites visited:

· Site 2 - former Syringodium meadow site visited by USGS for water quality monitoring, this northern end of the island chain had been completely removed by Katrina, and only a shallow unvegetated sand bar was left.

· L12, MO2, L13 are behind a remaining fragment of the islands -  at L12 there was some burial, MO2 was patchy elongated meadows running north-south, L13 was a deeper mixed species patch eroding around the edges.

· L05, L03, and L04 were along the edge of a new deep tidal channel. Lots of water flow, quite a lot of drifting macroalgal mats. Erosion along the edges of the tidal channel was very evident. Grass looks very healthy compared to the other sites.

Fig. 3: Thalassia testudinum L12

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Pictures of 13 April sampling

 

Data from 1998/1999

Data from April 2006

Fig. 5: Syringodium filiforme L13

Data from September 2006

Fig. 2: no Syringodium left at Site 2

Fig. 4: Thalassia testudinum MO2—signs of burial and anoxia

Fig. 6: Thalassia testudinum L05

Fig. 7: Thalassia testudinum L03 showing algae and eroding edge

Fig. 8: L04 a previously vegetated site was now a barren mud flat