I’ve been ignoring something very important on my blog lately, which is the effect of the oil spill in the Gulf on the food system.  Today I thought I’d start to broach that topic from the bottom up, starting with oysters.

Oysters are filter feeders.  This means they open their shells and suck in water, filter out the plankton, nutrients, and algae in the water, and then release the clean water back into the ocean.  For an ecosystem this can be very handy because oysters and other filter feeders are essentially the biological version of those high-tech bubbling filters you see in aquariums.  When too much nutrient gets into a body of water (imagine a bunch of soil run-off from a big storm forcing nutrient rich soil down the Mississippi and into the Gulf of Mexico as an example) oysters can filter it out before it gets out of hand.

Unfortunately for oysters, being filter feeders also means that when something like the Deepwater Horizon oil spill starts polluting the Gulf, they are some of the first creatures to bear the environmental consequences.  The oysters suck in water full of oil droplets and filter out the oil and other yummy stuff like mercury or hydrocarbons along with the plankton, nutrients, and algae that they want.  The oil and the dispersants used by BP to break the oil up into droplets either kill the oysters outright or accumulate in the oysters and eventually show up in the aquatic creatures that eat oysters…or the people who do.

Apart from being bad news for oysters and the people who like to eat oyster po boys, this reduction in the oyster population could be bad news for the Gulf as a whole.  See, in the environment nothing lives in its own little bubble.  If something goes wrong with oysters then it’s going to effect other parts of the Gulf.  Here are some possible consequences:

1. A bigger “dead zone.”  Have you head of the dead zone?  It’s this big spot where nothing can grow because there’s been an over growth of algae.  Remember when I told you that oysters filter algae out of the water?  Yeah.  No oysters means more algae and more algae can mean bad things for the Gulf.  It’s essentially like pond scum that covers miles and miles of space and makes it so nothing else can live there.
2. Bad news moving up the food chain.  Welks, starfish, and seabirds all eat oysters and so whatever the oysters filter out of the water slowly moves up the food chain as these guys eat the oysters and other guys eat them.  As you may remember from DDT in the1960s, this can be very not good for creatures at the top of the food chain (seen any bald eagles lately?) because the concentrations of the nasty stuff in the oil dispersants can build up.
3. Habitat loss.  Oysters create reefs.  Basically, as they build up their shells and then die off oysters create these magnificent, craggy structures built of old and empty shells that act much like coral reefs in terms of providing homes for marine life.  When lots of oysters die all at once this means that no new shells are being generated and eventually the reefs will wash away due to ocean forces like tides and currents.  Loss of reefs means loss of the marine organisms who use those reefs as homes, including anemones, barnacles, and breeding fish.