Mangroves!

I have spent a lot of time around trees this weekend, so I thought I would share a bit about our leafy brethren.

Yesterday I went on a field trip (yes, we still do those in grad school) to the He`eia mangrove swamp.  Mangroves were introduced to Hawai`i at the beginning of the 20th century, and since then the debate has been hot whether or not the introduction has benefited the islands.  Pros: the mangroves prevent sediment runoff from polluting the bays, they provide nursery habitat for local marine creatures, they provide timber. Cons: the mangroves are changing the coastline habitats, local animals don't seem to utilize the mangrove biomass, traditional fish ponds are ruined by mangrove roots and detritus.

A mangrove is a saltwater-tolerant tree that has developed special adaptations to living along the shore (salt glands to remove excess salt, seed pods that float, above-ground roots that "breathe" air, etc.).  Here on O`ahu, we only have the red mangrove:

See the red tint to the roots?  Yes, scientists are very creative with names...  On the Bahamian islands where I worked we had the red, white and black mangrove trees (two guesses as to how they got their names...).  The mangroves are able to live in highly anoxic (oxygen-deprived) environments.  Along the sand flats the iron and sulfur in the soil turn black in these conditions just under the surface.  This anoxic soil gives the mangrove swamps their distinctive odor.

I've never been the biggest fan of mangroves.  I have nothing against them, mind you, but the smell and muck associated with them are not the most endearing characteristics.  And having to wade through the swamp peering in between the roots looking for animals in murky water is not my idea of a good time.

But their role as a nursery for many species cannot be ignored, and this is why the mangrove being endangered should be such a concern.  In the Bahamas the lemon sharks give birth along the mangrove roots and generation after generation of sharks return each year to give birth where they themselves were born.  Here is a pregnant male seahorse we found in the swamp (yes, in seahorses the males are the ones who give birth):

We also found this beautiful little sea-slug:

I love those spots.  I got really excited at first thinking this was an Aplysia (an animal whose simple reflexes and learning ability helped build the foundation of the study of the nervous system), but alas it was just a slug.

Next time: the Old Pali Road...