Wednesday, August 08, 2007

A Week With Manatees

Manatee Week campers pose with Fred, a life-size Manatee model.


Jack Moran hustles toward the mark during a surf paddling race.
Recently, the campers at Sanibel Sea School camp were treated to everything manatee. For the week, we put ourselves into the role of our adorable marine mammals, the manatee.

The week started with our standard east-end hike in the morning, allowing us to explore the beaches and discover what the sea had brought forth. In the afternoon, we seined for fish to keep and observe for the week in our team aquaria. During that trip, we caught some juvenile Lookdown fish; which we continue to catch still – an uncommon summer treat in the shallows of the Gulf beaches. The previous week, we had the unexpected pleasure of swimming with a manatee, but on that day we only had the chance to hopefully look for a mammalian encounter. We didn’t get to swim with them, but we did make some close-up observations at Jensen’s Marina later in the week.

We made dioramas and had the great diorama design competition. Dioramas are museum-type displays that exhibit an animal in its habitat. Through this competition, we better understood the habitat requirements of manatees and the spatial relationship of these great creatures to their environment. Among the fascinating things we learned is that manatees can eat up to 180 lbs. of seagrass a day! The winning designers got a manatee toy to keep at home as a reminder of our massive mammalian friends.

We took the buoyancy challenge. In this game we donned life jackets, masks and snorkels and tried to get to the bottom despite our floatation devices! Then we stripped off the floatation and worked to stay afloat. It gave us a whole new meaning to floating on the deep blue sea. Buoyancy is something we take for granted, but is a real challenge for marine mammals; either it is easy to float and thus breathe, or it is difficult to get to the bottom and eat. Oh the tradeoffs we make.

The crowning glory was Manatee Madness where we blitzed some Sanibel hotspots to conduct some slightly different public education. In preparation, we had made a life-size manatee cut-out from cardboard to better understand the real size of an adult manatee. Armed with informative posters, our cardboard Manatee, Fred and sidewalk chalk, we stormed Doc Ford’s, Bailey’s and Fresh Produce to spread the conservation word. We drew manatees on the sidewalk and left behind information posters to help us all to better understand our mammalian friends. Two of our campers also recorded the process on film which can be seen on youtube.com by typing “manatee graffiti” in the search bar.

We owe a special thanks to the folks at Jensen’s Marina for sharing their manatees with us and Dairy Queen for cooling treats on the way back home. Doc Ford’s, Bailey’s and Fresh Produce allowed us to make spectacles (and leave some behind) at their businesses all in the name of conservation education – we appreciate their partnerships. Next week on the quest of our other marine mammals, during dolphin week.




Sea Sawdust - For Better or Worse

For the last two months, the offshore waters of Sanibel have experienced a prolific growth of a phytoplankton known as sea-sawdust. This phytoplankton is a type of bacteria – a cyanobacteria, previously known as a blue-green algae.

Within the past two weeks some of these clouds of dying phytoplankton have moved onshore and into San Carlos Bay.

This particular type of cyanobacteria occurs throughout the world in tropical and subtropical waters; it is in the genus Trichodesmium and there are about 8 known species. It was first recorded by Captain Cook in the 18th Century off the Australian coast. It was so extensive he mistook it for a sandbar and was afraid he was going aground. It is light brown in color and in calm conditions colonies of this bacteria (each colony looks like a microscopic brown rice grain) are caught in the surface tension of the water and float. It does look very much like a sandbar and still fools captains today.

Like so many things, it has good qualities and some not-so-good qualities. First , the good.

Estimates suggest that Trichodesmium accounts for perhaps 18% of the total photosynthesis on the planet – which makes it a very important component to life on this planet as we know it.
It is also fascinating because it can absorb nitrogen from air. Typically ocean waters are fairly nitrogen-poor and Trichodesmium is probably an important avenue through which ocean water gets badly needed nitrogen to support marine food webs. It gets this nitrogen from thin air (which is actually 70% nitrogen) especially well in waters that have high phosphorous concentrations; which the ocean waters near SW Florida naturally have.

It is also fascinating in that it undergoes daily migration patterns. Up to close to the surface during the day to harvest sunlight and nitrogen and then it sinks down deeper in the ocean during the nighttime. Pretty sophisticated behavior patterns for lowly bacteria. But, when there is no wind, it gets caught in the surface tension and makes big rafts on top of the water.
Now for some of the not-so-good stuff. It makes compounds that are toxic. In Brazil, in 1962 a human illness was described and linked to Trichodesmium; it is called Tamandare’ Fever (for the Bay in which it was described) or Trichodesmium Fever. Its symptoms include throat and respiratory irritations, extreme fatigue, joint and muscle soreness and post-orbital soreness (the backs of one’s eyes feeling sore). Many of these symptoms are shared with common colds, so the extent of this disease is rather unknown. It also appears that the reaction is rather short-lived – so that symptoms may go away rather quickly. Very little in know about this ailment and research is being done to know whether the species we have also can be responsible for this disease or other health issues.

The other not-so-good thing is that is has a particular odor and when colonies are decaying they smell bad.

So, next time you inhale, thank Trichodesmium for providing 18% of the oxygen you are putting in your blood, try to ignore the smell of their colonies dying, hope we don’t have a species that is dangerous to humans, and remember that among the wonders of living on our Sanctuary Island is the constant reminder of how we are a part of our natural, marine world.