You are correct, they are Pinus Strobus.
Pine needles are acidic and can lower the ph but they just need removal as like all debris in a pond. I treat them just like you would any other form of unwanted organic material. Keep your pond clean and it will keep your levels where you want them, whether you have pine trees, oak trees or fruit trees they all have issues of one thing or another. With the pine trees in mind during my build I installed a skimmer which works great for them and I also built a shallow but wide stream so when they do fall they tend to just get caught on the sides and are very easy to just pick out by hand. I have very few ever reach the bottom of the pond.