Snails eggs, most likely greater pond snails (Lymnaea stagnalis). Snails are an important part of your ponds ecology but they can become a nuisance in ponds where they have become overpopulated. The eggs themselves will not do any harm but their parents may well take a nibble at your plants.
Given that chemical controls cannot be used in or around water, you will need to reduce the population by fishing snails out when you see them. One technique is to float lettuce leaves on the water, then remove and destroy them when you have collected a number of feeding snails on them. As for the eggs, if you can remove them before they hatch then that will be a few less snails to worry about. Of course, if they are not causing a problem in your pond then no action need be taken.