Saltiness of Manatee Habitats Changes with the Seasons
dry season, the saltiness or "salinity" of coastal and inshore
habitat waters rises because there is less rainfall and thus less fresh
water flowing from the canal and riverine systems. Because manatees are
mammals and need to seek out fresh water to drink, the high level of salinity
in the habitat waters can affect manatee movement patterns.
Wondering how this calf can find freshwater in the ocean?
In a similar situation, the inland rivers and creeks discharge fresh water into the coastal bays. During the dry season the flow is minimal so the salinity of the coastal bays is quite high. Therefore, manatees have to travel further up the rivers and creeks to get sufficient fresh water.
As the rainy or wet season approaches, the salinities will decrease because more fresh water enters these systems and dilutes the salinity with fresh water. When we are well into the wet season we rarely see the manatees go all the way into POI to drink because the water is often fresh enough at the southern end of Faka Union Canal. Likewise, we see fewer manatees traveling far up into the rivers and creeks because the water becomes fresh enough for them to drink near the mouths of the rivers.
Do You Define and Measure Salinity?
During the dry season we will typically see the manatees make a journey toward fresh water about once a week. During the wet season we see more extended periods of time using the outer islands areas with short trips to river mouths, mouth of Faka Union canal or the canals of Marco Island about once every 1-2 weeks.
Another interesting note is that manatees can actually sip the fresh water off the surface after a good rain that may let them stay in the salt water for a longer period of time.
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