Dock fouling creatures disappearing in SF Bay as salinity hits new lows

Note to iNat dock-foulers: Due to heavy rains, salinity in the SF Bay is presently at record lows, the lowest numbers since 1986 (I think).

Today I was in Redwood City, where salinity has dropped to just 13 psu (Practical Salinity Units). For comparison, the SF Bay is normally around 20-25 psu during the winter, and the coastal ocean is around 33 psu. At the Marine Science Institute (Redwood City) dock, there was almost none of the normal 'mobile life' (mollusks, polychaetes, crustaceans, fish) -- these were the only three species for an hour of looking. The sessile creatures (tunicates, hydroids, bivalves) looked awful as well. And of course everything was covered in silty gunk. One MSI staffer mentioned increased numbers of dead leopard sharks washed ashore (and distressed sharks circling aimlessly). For their own aquariums, MSI has temporarily stopped collecting on the outer coast and is attempting to slowly acclimate their existing creatures to lower salinity levels (they normally pump in SF Bay water for their tanks).

If anyone's available to check other "Inside" SF Bay dock-fouling locations, it would be interesting to see what's survived there. Take along a hydrometer if you have one!

It will be interesting to see when/how the SF Bay creatures recover after the storms.

Posted by anudibranchmom anudibranchmom, February 15, 2017 23:05



Interesting. Do you have a specific kind /brand of hydrometer you use?

Posted by kueda over 3 years ago (Flag)
Posted by anudibranchmom over 3 years ago (Flag)

This is normal for SFB. During El Ninos and other periods of heavy rain dock fouling & intertidal dwellers die off. It's one of the reasons SFB is so full of invasive species. Once the fresh water flow stops recolonization of the docks depends on recruitment from whatever survived below the fresh water lens (which floated on top of salt water) or from fouling on newly arrived ships.

Posted by leslieh over 3 years ago (Flag)

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