We are now in LAB mode!  The alewives are spawning in North Pond, where we have a collection permit, and we have some eggs in a bucket (with the cool spring, the eggs have not concentrated in the waters making collection challenging). Now we need to set up our aquariums with the different amounts of salt we have decided for each tank.  Our question is:  Will a salinity greater than 2.0 ppt affect the survival of alewife eggs or fry?  Most classmates think that salinities greater than 2.0 ppt will decrease the survival of eggs and fry.(Substitute student hypothesis here?)  The question and our hypothesis was framed and informed by published results of the few previous salinity studies (a peer review process!) that we found.

 

We have to figure out how to create salinities of 2 ppt, 4 ppt, 6 ppt, and 8 ppt for the aquariums we’ll compare to our control aquarium.  Salinity is the one variable we are testing.  Our constants will be to use the same size tank, the same water level in the aquariums, the same temperature, and the same number of eggs.  To figure out our salinities, we used our math skills.

We started by putting a gallon of distilled water into a clean (large) aquarium.  We added 1/8 of a teaspoon of “Instant Ocean” salts, which we massed and determined was 1.14 grams, to the gallon of distilled water.  Interestingly, the gallon container was marked 3.78 L (3,780 ml), but we measured its contents and found the gallon to contain 3,880 ml of distilled water.  We mixed the solution thoroughly, then let it sit for about 5 minutes, then measured its salinity.  The salinity was 0.26 PPT.  Both our classes did these steps, and we both measured a salinity of 0.26 PPT.  From here, the rest was math to get a basic salinity “recipe” to make whatever we needed.  We had to use math to solve for how many grams of Instant Ocean would make 1 PPT.  Once we knew this, we could double our amount of Instant Ocean to make 2 PPT, for example.

 

The tanks are now all set up and ready for eggs!!