[CT Birds] Background on Barnacles

Dennis Varza dennisvz at optonline.net
Tue Mar 27 07:08:19 EDT 2012

Background on the Barnacle Phenomenon

Earlier I mentioned that this phenomenon is unique to Connecticut,  
but never explicitly explained why.  It is all because of  
Connecticut’s unique geography. Connecticut is separated from the  
ocean by Long Island and the Sound which were produced by the  
Glaciers. Long Island Sound is an estuary with properties very  
different from the ocean. I sometimes think of it as Chesapeake  Bay  
on its side.

Barnacles need a rocky substrate and the distribution of rocky shores  
is very limited. Sand beaches go from Florida to New Jersey then  
along the south shore of Long Island, then up to Cape Cod. Hence no  
habitat for barnacles there. Rocky shores go from Mane south to  
northern Massachusetts then again from Rhode Island through  
Connecticut. Connecticut is kind of unique because the shore is a  
mixture of rocky headlands separated by rivers and streams and small  
sand beaches.

In the Harrison Ford Movie the “Patriot Games” there is an amusing  
mistake. Harrison Ford is an analyst working in the Pentagon (in  
Virginia). He has a birthday party at his house which is a mansion on  
a bluff overlooking the ocean. The nearest bluff overlooking the  
ocean would be Rhode Island. That would be a tough commute! In  
reality it looks like California.

Long Island Sound is funnel shaped, wide on the east ocean end and  
narrow on the west New York end. This condition forms several  
gradients. As one goes from east to west The differential in tide  
goes from 4 ft. to 8 ft. West winds blow water out of the sound  
making tides lower than expected. East winds blow water into the  
sound making tides higher than expected. That is why “Noreasters” are  
so devistating to the Sound. And, of course their effect diminishes  
as one goes west.

Sedimentary material from the rivers and erosion from the east  
creates the sandy beaches, such as they are. If one looks at the  
location of the sand beaches from east to west, they start out well  
up bays and coves such as Jordan Cove and become situated at the  
mouths of bays. Look at the bars of Milford Pt.

It is the sheltered aspect of the western Sound that promotes the  
formation of Barnacle plumes. Water has different properties for  
organisms of different sized. When one gets below a certain size  
water becomes more like molasses. As a consequence they have great  
difficulty moving in it. Large scale movements are determined by  
currents wave action. I recall a study in California where the amount  
of recruitment of barnacles at a particular location were determined  
by the direction of currents at the time of recruitment. If they were  
onshore they got great recruitment. If there were off shore currents  
they go little recruitment.

In western Long Island Sound. wave action is almost entirely  
determined by wind.  The stronger the wind the bigger the waves. The  
direction of the wind also has an effect.  The longer the reach (the  
distance the wind travels over the water) the greater the waves. When  
the wind is above 10 mph. one can expect 2-3 ft. waves increasing to  
white caps. When the wind is around 5 to 10 mph. one can expect 1  
foot waves. Below 5 mph. the water becomes ripple to flat. It is  
during periods of light wind (less than 10 mph) that will cause the  
larvae to be stuck at the surface of the water. In the eastern sound  
one gets larger reaches and more waves in general.

So, although barnacles may be abundant and widespread from  
Connecticut to Maine, it is only the western sound that has the  
sheltered water that traps the larvae at the surface. In looking at a  
map the New England shore, Narragansett Bay caught my eye. Perhaps  
the bay provides enough shelter to produce the same phenomenon. I  
contacted Rhode Island Audubon and they reported nothing. The event  
may happen there, but on a scale too small to notice if one is not  
looking for it. I tried to contact Long Island birders and got no  
reply. I wonder if one has habitat like the south shore of Long  
Island to bird, does anyone bother to bird the north shore?

Dennis Varza

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