As part of my ongoing community-based research on water quality in coastal North Carolina, I ended up tasked with answering what I thought would be a very basic question: what is the predominant pesticide used in my county? The largest farm and by far the largest amount of cropland is occupied by a traditional corn/soy rotation with the occasional cotton thrown in. Given the multitude of American acres donated to corn/soy, I figured I could easily find out the basics of that crop’s chemistry. Not so. My little information adventure has made me realize why there are so many rumors surrounding farming’s impact on water quality in the region. Rumors are easier to find than facts.
fish face a tradeoff of where to use their energy, much like the polluted fish in the Lorax by Dr. Suess
Overfishing is most often implicated as the cause of decreasing fish stocks and that makes a lot of logical sense if you’ve ever seen a large commercial trawler unload its catch. But there very well might be another force at work in the precipitous decline in fish stocks worldwide: pollution. The basic premise is that it takes resources to deal with pollutants that normally would be given to growth and reproduction. Through polluting the ocean, we have selected for the fish individuals that can most effectively divert those resources, inadvertently also selecting for smaller fish that reproduce less. That has huge implications for the fish’s population dynamics and potentially total fish stock. More details below the fold…
Caffeinated crabs, anti-depressed dolphins, and feminized fish, oh, my! Can you imagine what would happen if sea creatures had access to your medicine cabinet? Well, they do. Pharmaceuticals from humans make their way into the ecosystem either through excretion into urine or by people disposing of old medications down the toilet. The first of these sources then flows with sewage, which has already been described by this series, out from leaking septic systems or through ocean outfalls into the sea.
"Warning! Stormwater discharge area may be contaminated by discharge from pipe. Swimming is not recommended within 200 feet of this sign during active discharge"
You live on a rural island. You poop. You flush. Does your island have a sewage treatment plant? Is your plant large enough to deal with the influx of tourists that increases the population of your island by an order of magnitude in the summer? Ever stop to look at the metal pipes on your island’s beach to see what was coming out? More than likely, there’s an ocean outfall involved in your island’s wastewater treatment plan. It may only be for overflow, but it’s an option.
What does “ocean outfall” really mean? Well, often it means raw sewage is dumped into the coastal environment that we all love to swim in. Read More
Sedimentation in the Chesapeake - look at the brown toward the headwaters. Found at nasa.gov
Rocks erode, travel down rivers and eventually in the form of small particles, settle in river deltas and estuaries. Even smaller pieces can be carried hundreds of miles into the ocean. It’s all part of the natural process of sedimentation, but like many other natural cycles, this one has been hijacked by human activities. Development, agriculture, channelization of streams, damming and many other practices change the natural course of sediment in the coastal oceans more than the ecosystem can handle.
These changes can either be a drastic increase in sediment runoff from upstream sources or a complete deprivation of naturally occurring deltas. In addition, many pollutants cling to these sediment particles so that changing the location of the sediment also shifts the location of pollution.
The Great Big Blue looks like it contains nothing but water and maybe a little salt, especially out in the open ocean. However, this kind of sparse environment is exactly where the chemistry matters the most – it’s a fine line between not enough, too much, and just right. Given this, there’s no distinct myth here but an underlying unresolved question: what is the limiting factor that keeps the open ocean at low productivity?
The ocean is full of metals and minerals that naturally occur such as zinc, copper, and cobalt and many marine organisms therefore depend upon access to those metals in small concentrations. However, inshore marine systems receive inputs from industrial, mining, and stormwater runoff that far exceed what these organisms can use. So what’s the effect? There was recently a good review article by Mayer-Pinto et al describings the effects of these metals at the assemblage level that basically did my job for me, research-wise, covering both marine and freshwater systems.
In light of the BP oil spill, this week’s installment of Chemistry of the Great Big Blue will be particularly relevant to current events and hopefully already on the minds of everyone reading. Where do petrochemicals in the marine environment come from other than oil spills? Road runoff, refineries, plastic production, plastic degradation, atmospheric deposition and ocean circulation from other parts of the world, natural seeps, and the list goes on and on. It is important to note, however, that oil spills are not necessarily the predominant source of petrochemicals. So what exactly is a petrochemical and what does it do?
From the microscopic to the gigantic, plastic debris has plagued our oceans since its invention. Much of the problem originated initially because we didn’t realize that plastics don’t degrade until after we had dumped tons into the ocean, largely off of ships as trash. WHOI offers a good summary of the history of plastic pollution. Many things changed since that first realization and the nature of plastics in the marine environment has a very different face nowadays.
The plastic is smaller and more widely distributed. There are fairly well-known areas that collect the plastics such as the Great Pacific Garbage Patch. There are also other areas affected that are closer to shore and where people use marine resources. Plastic often settles in seagrass beds that serve as important nursery habitat and on beaches where turtles and shorebirds mistake them for food and nesting material. Need more details on plastic?
Remember when I promised to profile chemicals in the ocean as a New Year’s resolution? If not, here‘s my first in the series of one posts that resulted, reposted here as a reminder. As always, I encourage checking out the old comments. From now on, I still hope to give the series a second shot at life, so keep checking back for more installments of the series.
As my fellow fry-entists can attest, we know so little about the oceans that every deep sea expedition yields a handful of new species to describe, focus on saving one species may come at the demise of another, and people still won’t go swimming in some areas for fear Jaws will eat them. And that’s just a quick sampling of what we’ve written so far. The depth of our societal ignorance about the ocean and how it functions is enormous. Just as the fishermen of days gone by used to think that the sea offered God’s unlimited bounty, modern day people don’t seem to understand that the ocean isn’t an endlessly large dumping ground for all things undesired in our terrestrial lives. From trash to carbon dioxide to birth control pills, our oceans are the unfortunate downstream victims of human decisions. We don’t understand the impacts, sources, or even types of chemicals that are ending up flushed to the seas. One of my new year’s resolutions is to become more acquainted with the chemicals of the great big sea. Today’s profiled chemical: the unknown. Read More