Estuaries differ from rivers in many regards. First and foremost, estuaries are subject to tides and the mixing of salt and fresh water. Any successful estuary monitoring program must take into account the stage of tide when scheduling training sessions and sampling times. Tide charts are readily available and should be a standard part of any program coordinator's toolkit. The fact that high tide occurs at different times in different parts of the estuary undeniably complicates scheduling.
Estuaries are complex, with a wide variety of environments that are constantly changing.
When the tide is rising, incoming salt water does not mix uniformly with fresh water. Estuaries are home to a fascinating variety of living organisms. Special regulations and methods pertain to monitoring bacteria in shellfishing waters. Shellfish poisoning is even more frightening than microbial contamination since it can be rapidly fatal, and the toxins are not destroyed by cooking. Let's take a quick look at some key water quality variables you're likely to monitor in estuaries, and see how they differ from their freshwater counterparts.