Wildlife Drinking Water Availability Update 1/19/2021

It’s been a while since we issued a project update, primarily because the Keys’ rain season in 2020 was one of the wettest (and longest) in recent history, resulting in great drinking water availability to wildlife throughout our testing range (No Name Key to Upper Sugarloaf Key). Our volunteers continued to collect salinity measurements, however, so we have an unprecedented, complete record. As we are getting into the core of the dry season, another set of data came in over the past week…and here are a few (very welcome) highlights:

Overall, drinking water availability is excellent on all monitored islands! In fact, there are numerous natural water hole sources on islands like Middle Torch and No Name Key with salinities less than 1 ppt (part per thousand). That is not only extremely drinkable by both man and beast, but in most cases is just slightly higher that the Keys’ municipal tap water which we are measuring at @ 0.2 ppt. Just about the only negative in the recent reports is that a number of these sources have quite low water levels. In the case of solution holes that are connected to the underground fresh water lens, this may be due to our present very low tide cycle. A good example of this is No Name Key where the solution holes are all below 1.0 ppt but quite low in water volume, while a test site that is a “depression” (completely dependent on rain input) still has quite high water (at 0.86 ppt) that will last for several months. Some more interesting highlights:

Blue Hole, Big Pine Key: On 1/16/2021 Blue Hole’s salinity was 2.34 ppt. The famous Blue Hole is connected to the underground fresh water lens, but during Hurricane Irma got overwashed by sea water storm surge, making its salinity spike to double digits. Since then, it has steadily (but surprisingly slowly) declined in salinity. When this project officially began in April 2019 (1.5 years after Irma), its salinity was 5.57 ppt. A year ago it was 4.11 ppt. Our ample recent rain season pushed it significantly down to the present 2.34 ppt.

Long Beach Peninsula, Big Pine Key: As we have reported in previous updates, Long Beach got devastated during Irma and the extensive salt water storm surge left the very important ponds in the large hardwood hammock area spanning from Long Beach Rd. toward the BPK mainland saturated with salt. During subsequent dry seasons these ponds became hypersaline, breeding salt pond bacteria which actually turned them red, and of course unusable to wildlife as drinking sources.  This condition persisted through the first half of 2020, rendering the otherwise well-recovered forest practically void of wildlife. Ample rains by June 2020 finally tipped the balance. We are happy to report that that trend continues to today where one of the larger ponds has, for example, salinity of 7.29 ppt, and a smaller isolated one next to it 4.21 ppt. – not exactly boutique water but wildlife-drinkable. And a HUGE difference from this time last year when our best salinity measurement in the entire area was 34.2 ppt (essentially seawater strength). Our results show that entire important portion of Key deer habitat (the US1 was raised and underpasses constructed to connect it to BPK mainland) is so far again available to wildlife. The question now is: did the ample rains help get rid the ponds of the excess Irma salt through overflow so they can sustain low-enough salt concentrations through the rest of the dry season? We intend to intensify our sampling to answer that question.