What could be causing the presence of black brown gunk in my dog's ear and how should I address it?

The presence of black or brown gunk in your dog's ear could be due to an ear infection, ear mites, or excessive wax buildup. To address it, you should take your dog to the vet for a proper diagnosis and treatment. They may prescribe ear drops or medication to help clear up the issue. Regular ear cleanings and grooming can also help prevent future problems.