Thursday, May 24, 2012

Amazing Seedling Recruitment in a Natural Meadow

While it is not uncommon to observe the random eelgrass seedling or two in or adjacent to openings in the meadows during winter and early spring, it is a rare occasion when we find large numbers of these small shoots blanketing the bottom.  While diving near Stonington Pt., CT last week, we observed one of these rare events.  I had wanted to drop into this site to observe the natural meadow and compare the growth there to what we had observed earlier in the day at our Little Narragansett Bay, CT. test plots.  However, what I wasn't prepared to find were the incredible number of seedlings.
As I swam through the meadow I saw several large open areas; we usually call these areas "blowouts", but there was no indication as to how these formed as I don't think this site sees heavy wave energy and waves that could scour bottom.  When I dropped into the first open patch I was amazed when I saw all the seedlings carpeting the bottom.  They were all roughly the same size and seemed to be grouped in waves corresponding, more or less to bands of small gravel amongst the otherwise sandy bottom.
In my nearly 20 years of diving in eelgrass I have never seen so many seedlings in one area except for possibly several years ago when a meadow in at Noyack Creek in the Peconic Estuary recruited from seed after loss all of the adult shoots the previous year (these seedlings all eventually died that summer and the meadow was lost). 
In addition to the open patches there were also a number of seedlings growing in and amongst the adult shoots near the edge of the openings (see above).  I did not spend time looking further in the vegetated areas to see what the extent was, but I think the seedlings were mostly limited to the openings and near the edge of the openings.

It will be interesting to visit the same meadow later this year to see if the seedlings survive.  There are any number of reasons why the seedlings can be lost here not the least of which could be overcrowding and competition for space and light.  Other factors could be bioturbation and other disturbance.  

The main question I have is why the seedlings recruited here so well in the first place?


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