how to release GPU RAM after taking a photo.

Hello how to free gpu ram after taking a photo. when reached ~1000 photos my computer is stuck because I used all the gpu ram.
for now I am using the code below to create a photo:

IEnumerator takePhoto(string filename){

   yield return new WaitForEndOfFrame();
  // Debug.Log(gameObject.name + " Save Color Photo");
 Texture2D screenImage = new Texture2D(Screen.width, Screen.height);

 //Get Image from screen
 screenImage.ReadPixels(new Rect(0, 0, Screen.width, Screen.height), 0, 0);
 screenImage.Apply();

  //KOKO
 //Convert to png
 byte[] imageBytes = screenImage.EncodeToPNG();

 //Save image to file
 System.IO.File.WriteAllBytes(filename + "_scene.png", imageBytes);

2DTexture is seen as gameobject in Unity, they are alive as long as the scene is alive or you destroy them via Destroy().