I have a probably very simple problem which I cant solve. I am weighing animals in seawater by placing them on a small PVC arm that is fixed on a balance and reaches into a beaker of seawater. On the arm, I place an organism and measure the specific weight of the animal. Now, the weight of the animal changes a lot between days which cannot be explained by physiological processes. I believe this might be due to the water temperature which I also collect alongside. Can anybody tell me how to correct for water temperature if I dont know the volume of the organism?