e_moon60 (e_moon60) wrote,
e_moon60
e_moon60

  • Mood:

Gulf Ecology and the Oil Spill: ramifications

The implications of the Deepwater Horizon blowout are obvious in some ways (oiled pelicans, dead turtles, air pollution from burning oil)  and less so in others.  To discuss this in any depth, it's necessary to give some background on what's going on with marine ecosystems in a time of rapid change in atmospheric carbon dioxide (CO2) and the  pH of ocean water (it's becoming more acidic) and rising sealevel. 

Let's start with the basics of the carbon/oxygen biogeochemical cycle.   The source of oxygen in our atmosphere is photosynthesis--plants using the sun to break CO2 apart and release oxygen molecules, O2 (should be a subscript, but...)    Simplistically, plants release oxygen and fix carbon into their tissues--carbon is a component of sugars, starches, fats, and proteins.  Animals (like us) take in oxygen and combine it with sugars, starches, fats, and proteins to release energy to do everything we do (grow, repair, move, reproduce, etc.)   We exhale CO2.   In fact, many plants also use oxygen and exhale some CO2, but they release more oxygen than COs...and that's where we get it.    Much, if not most, of the oxygen currently being produced is released by photosynthetic plants in the ocean, including tiny one-celled phytoplankton, kelp beds, and the like--there's a lot of ocean surface, but these plants can only photosynthesize in the upper waters, where enough sunlight penetrates.  When the system is balanced, the oxygen levels in the atmosphere stay about the same (where we like it--about 21%) and the CO2 levels stay about the same (where plants like it and it's not toxic for any of us and the oysters' shells don't dissolve--about 0.03% of the atmosphere.) 

Why does higher CO2 lead to oyster (and other shells) dissolving?   Because when CO2 is dissolved in seawater it forms carbonic acid.    The acidity of a solution is measured as a change in pH--lower pH means more acid.   The shells of marine creatures are made of calcium carbonate...which dissolves in an acidic environment.    If the pH lowers too much--the sea becomes too acidic--shells will not form, and existing shells (and coral reefs) will dissolve.   Marine pH is already lowering in response to the rapid rise of atmospheric CO2, and the phytoplankton level in many parts of the world's ocean is much less than it was in 1960.  Other oxygenating water plants--sea grass, kelp, others--are also found less often.  Increased water temperature increases the rate at which acid dissolves calcium carbonate and also damages water that cannot tolerate it.  Pollution of bays and estuaries with agricultural and other chemicals, turbidity (muddiness) of the water that reduces penetration by sunlight, physical destruction (by human disturbance of the bottom of shallow water with dredges and nets) have all taken toll of the healthy plant life, just as human activities on land have reduced the vegetation cover and health of the land.  (CO2 also has direct toxicity, even in the presence of adequate oxygen--its effects begin to show at about 1%, breathing rate doubles at 3%, quadruples at 5%, and can cause death if such exposures continue--or if higher concentrations occur.) 

The Gulf has been at risk for a long time:  development of coastal areas, destruction of marshes and wetlands, a heavy load of agricultural chemicals entering from rivers,  toxic chemicals dumped illegally into rivers upstream and marshes,  treated and untreated sewage, accidental spills from cargo and other ships, flushing of bilges, and spills from coastal petrochemical plants, offshore rigs,  and other industrial activities along the Gulf coast of several states combine with the increased acidification, increasing temperature and rising sea levels to stress the sealife in the Gulf.  The Gulf, like other fisheries worldwide, has seen a decline in fish and shellfish production--total tonnage and the average size of the fish and wild-caught shrimp are all down. 

That's background.   Now factor in the magnitude of the current leak and here's what can be expected:  

1.  The oil will adversely affect all marine species in the Gulf except those bacteria that eat petroleum, from one-celled plants and animals to whales--all of them.   Some die because of contact and/or ingestion of the oil, which is toxic to them.   Some die because of contact with, or ingestion of, the dispersant that is used to make the oil break into little droplets: it's toxic to them.  Some--including phytoplankton--will die when the water is too turbid, or the surface covered with oil, so that they cannot photosynthesize.   The loss of phytoplankton in deep water will lower the dissolved oxygen in the water--the oxygen fish and shellfish extract with their gills and without which they cannot survive.   As the oil moves inshore and gets into coastal marshes, the submerged oxygenators in shallow water, such as eelgrass, will be less able to produce oxygen.  At sea, the loss of seaweed, such as sargasso weed, will remove habitat vital to many sea creatures; in the shallow waters of bays and estuaries and salt and brackish marshes, the loss of  submerged vegetation and emergent vegetation will remove habitat vital to fish and shellfish.  

2.Adverse effects on marine life will cascade through the food web.   Every population crash in a marine species will cause others to decline--big fish eat little fish, and bigger fish eat the big fish.   But more than other fish depend on the web of species:   coastal birds such as ospreys and eagles are fish-eaters; more marine species (terns, gulls, pelicans, frigate birds, others) fish the coastal waters.  Not only will they find fewer fish, they will find fish containing toxins that were in the oil, toxins concentrated as they moved up the food chain.   Beyond that are the shorebirds, from tiny sandpipers picking little shellfish out of the sand as the waves lap in and out to the tall cranes that hunt the marshes for crabs and other fat-full prey that move into the marshes to reproduce, stocking up for the long migration back to the north.    Their habitats have already been cut by human development--in years of drought, in Texas, so little fresh water runs down the rivers to the bays that salinity rises and their needed prey may not survive.   Both year-round and migratory birds utilizing coastal food sources will find less food--and toxic food--and can be expected to experience die-offs from that alone.  Migratory birds arrive hungry after their breeding season and the long flight south--they must eat voraciously to be strong enough to migrate north and reproduce in the spring.    The two years of the most recent Texas drought saw die-offs among whooping cranes, the most endangered.

3)  In addition to the food problem, the oil presents a physical threat: not only oiled feathers, but--as it becomes more and more tarry--a gooey mess that can trap small animals and weigh down birds.    The Gulf Coast sees most of the fall and spring bird migration in North America (a smaller migration travels west of the Rockies.)  Both the Eastern and Central flyways bring birds to the Gulf coast--and birdwatchers come to see them.  Many birds not shorebirds or waterbirds land on the beaches through exhaustion...and if they land on a sticky tar ball they can become stuck (or, in trying to clean tar off their toes with their bills, contaminated.)  Shorebirds and waterfowl need the water, and seek it out--herons fish in the surf as well as in quiet inland ponds.  Geese and ducks utilize bays and estuaries as well as swamps, marshes, ponds. So they will go there, whether it's healthy or not.

4) Dead animals decay  or (the minority) are burned: both produce more CO2.   When animals decay underwater, the CO2 produced further depresses pH.  When the CO2 enters the atmosphere, that's no better.  Toxins in the oil, that were in the animal, may eventually sink to the sea floor if they're dense enough but can re-enter the food chain if marine life recolonizes the area.  Decaying matter also lowers dissolved oxygen, a more immediate threat as this makes the water anoxic and unsuitable for many marine organisms, such as fish.  The dieoffs already seen (and the unseen ones of fish and shellfish that die in deep water)  are producing more CO2 (and other gases) that will only make the problems worse.

So we have an interlocking series of problems caused by the oil, on top of some interlocking problems caused by the rapid rise in atmospheric CO2 and the associated acidification of the ocean and the rise in sea level and the higher mean global temperature.   Most of these problems are the result of human mismanagement of the ecosystem, starting back a ways but accelerating rapidly in the 20th and (so far) 21st century.   How bad could it get?  Very bad: the entire Gulf ecosystem could crash, and would not be replaced by in-migration until the pollution had been cleared out.   If the oil can't be stopped, this is a definite possibility.  Recovery would not eve begin to occur until the oil quit flowing.  The Gulf is a small part of the global marine environment, so the loss of oxygen from Gulf phytoplankton would lower oxygen production nituceably but not critically--but to keep the oxygen fraction where it should be, some other oxygenators would have to be found, and CO2 emissions cut back.  Pretty bad: we lose quite a few marine species, including some keystone species. Both primary (plant) production and the production of seafood that we like to eat would drop to low levels, with the need to impose strict limits on take until the population recovered--likely to take decades.  Some favorite seafoods might be unsafe to eat for years.  We lose many migratory birds, but only a few species of them (whooping cranes are obviously at risk.)  Bad: we lose fewer  marine species directly, we lose only one or two non-marine species,  fish and shellfish harvests are deferred several years, with limits (but slightly more generous) for another decade.    And those harvests would have to be tested for toxicity.

This spill occurred at a critical time of year--at the front end of hurricane season, at breeding season for permanent Gulf wildlife (birds and turtles, but also spawning fish and shellfish and corals.)   Summer wind patterns will tend to move the oil shoreward, as will hurricanes.  Storms like the one we just had will interrupt efforts to deal directly with the oil.   The fall migration has already begun in some species (long-billed curlews are already at the coast.)  The incomplete and secretive response of BP, and the collusion of politicians (like mine from Texas--for whom I didn't vote, from gov to Congressman) who owe their seats to oil money, prevented quick and effective action on the coasts.  BP claims to have some 2 billion in an escrow fund to pay damages...but that money needs to be spent upfront, hiring the people who are unemployed because of the loss of fishing and shrimping (as two examples) and who have applied for jobs and been ignored.  Spend the money putting people to work to do what can be done to save the coastal areas before the oil arrives, and clean it up afterward.  

And it would be a really good idea to make judges reveal their oil company holdings before they're allowed to rule on whether drilling should keep going in the same dangerous deepwater situations.   That judge should have recused himself...that he didn't proves he's unfit for the bench (I dare not hope that a bar association would actually kick him out of the bar altogether...)

Back in grad school, my applied ecology prof told us that if you manage the water, the land will just about manage itself.  Most of this planet's surface is water.   If we managed the water right...the whole ecosystem would manage the rest of it.





Tags: ecology, oil spill
Subscribe
  • Post a new comment

    Error

    default userpic

    Your reply will be screened

    Your IP address will be recorded 

    When you submit the form an invisible reCAPTCHA check will be performed.
    You must follow the Privacy Policy and Google Terms of use.
  • 11 comments