Oh, that fresh Rocky Mountain stream water… sparkling snowmelt, flowing from the ancient peaks to the broad plains, teeming with hermaphroditic fish. Hermaphroditic fish, you say? Like, fish with male parts and female parts, all in one? In our streams? Ok… well, maybe not everywhere… just downstream from where we use the bathroom.
Hormonal disruption seems to be in the news quite a bit lately. Endocrine disrupters have been found in our food containers, and by proxy, our food. Every once in a while, a report on these hormonal substances is highlighted in the mainstream media, stirring a little panic and raising many questions. This week, it was reported that intersexual trout were found in five different Rocky Mountain National Park lakes. It is becoming a well known fact: endocrine disrupters are in our water. But that fact just raises more questions: How high are the concentrations of these chemicals? How much is too much? Is there a safe amount of endocrine disrupters to have in your water supply? And, while we’re at it, just what are endocrine disrupters? Where do they come from? Finally, the one everyone wants to know: are they harmful to humans?
Research at the University of Colorado at Boulder has turned up some interesting answers to these questions over the years. As a student in the environmental studies program, I don’t need to wait for a slow news day to hear about the subject… this is one of the professors’s favorite studies to cite. A study on the reproductive systems of invertebrates in Boulder Creek revealed high levels of common endocrine disrupters alongside an unusually large number of female and intersexual fish, downstream from the municipal treatment plant.
I can’t blame my professors for liking this one.. what better way to get your students interested in the effects of pollution than to make it personal? "Your pee is making the fish turn female!" For students who strive to reduce, reuse, and recycle, this can come as sort of a shock. Now, before you start to snicker at the excess hormonal output of college students, you should realize this same situation is quite possibly happening downstream from your water treatment plant, too.
Today, I’m attending a guest lecture by Dr. Alan M. Vajda, one of the researchers who found anomalous intersexual fish in Boulder Creek. Here, I’ll be live-blogging the lecture, and sharing some of the images and data available on the Boulder Area Sustainability Information Network (BASIN) website. At the end, I’ll offer my own thoughts on some of the new questions being raised: Are these substances harmful to humans? To our ecosystems? Should we stop using products which contain these substances?
First, allow me to introduce the star of the show, the fabulous sex-changing Osteichth–yes, the white sucker. This fish is native to a broad swath of North America, including the eastern slope of the Rocky Mountains. (It has been introduced to the western slope as well.) The white sucker (Catostomus commersoni) made an ideal subject for this study, as it is found in both the frigid rapids in Boulder canyon, as well as the warmer sections of Boulder Creek to the east, where it flows across the plains. A weir in the creek separates the two habitats; fish downstream from the plant cannot pass the barrier and swim upstream. The fish are named for their sucker-like mouth, which is well suited for bottom feeding. Around dawn or dusk (those magical times when the wetlands seem to come alive) you can find these guys troweling along the bottom of the creek, sucking up anything they find like a vacuum cleaner: insects, worms, freshwater crustaceans and mollusks, and whatever else happens to be in the way. They have no need for teeth; they just suck it down.
While they’ll eat anything, just about anything will eat the white sucker–birds of prey (herons, loons, eagles, ospreys, etc.,) mammals (including bears, wolves, raccoons,) and naturally, bigger fish, (pike or bass). Of course, we’ll eat them, too. (Well, not me–I’m not a big fan of fish. I’m told they have flaky and sweet white meat and lots of little bones.) Are they an essential species in our ecosystem? I’m afraid that’s not for me to decide, but I’m willing to give the fish the benefit of doubt. Besides, I can respect any species that likes to clean up the muck.
Now, to the science. Dr. Vajda begins by describing the area studied. Here in the arid west, we don’t let a drop go to waste; all of the water flowing down from the mountain essentially goes straight into the municipal water supply of the Front Range. Dr. Vajda points out that if Denver stops returning their wastewater (better known as effluent) to the river systems, the river would simply stop flowing. In other words, most of the water–around 90%–of the water flowing downstream from the treatment plant is effluent flow, rather than fresh. Because these streams all flow into the same place, they concentrate just about everything, including endocrine disrupters.
What is an endocrine disrupter? Technically, it is any substance which interferes with natural hormones. Estrogen is the most primitive hormone, and so tends to have a broader effect. So, chemicals which act like estrogen can easily send the wrong signals to the body. There are a wide variety of chemicals found in our environment which can act in this manner. Some are natural (certain steroids), but many come from us: synthetic steroids (17a-ethynylestradiol), more commonly known as "the pill". Other contaminants include metabolites in detergents, pharmaceuticals and non prescription drugs (including caffeine), antibiotics, antioxidants (BTA), disinfectants (which turn into dioxins in the river system), insect repellants (DEET) and pesticides, and finally, Bisphenol A.
Bisphenol A was invented by Aleksandr P. Dianin in 1891 as a synthetic estrogen. Sometime after its discovery, someone figured out it was useful in creating plastic, and it has become a rather ubiquitous compound since. (Notice… we knew it was a estrogen-mimicking carcinogen BEFORE we started to use it in plastics. Priorities, right?) While this substance has certainly made plenty of headlines, it didn’t really make it into the study we’re discussing here. Dr. Vajda’s work focused mainly on natural and synthetic steroids and detergent metabolites, rather than Bisphenol A. This is partially because natural and synthetic steroids as well as detergents all work in the same manner. They work as additive… if you put a little bit in the water, you’ll see an effect. (Other chemicals have certain threshholds… some can be present in the water without causing any apparent harm.)
When they looked at the water in Boulder creek, they found more than a little bit. Upstream from the wastewater treatment plants, the water is quite pristine… only trace (naturally occuring?) amounts of estrogen are found. Downstream, on the other hand, estrogens are found at much higher amounts. Of course, it isn’t just a location issue, but also a timing issue. The peak flow of Boulder Creek (and other mountain-fed estuaries) occurs in the spring, with the lowest flows occurring in the fall–the same time students are arriving to the college.
Endocrines are used in regulation of many vertebrate systems: the heart and blood vessels, the pancreas, brain, liver, gonads and so on. When present, they tend to effect reproductive effects: fertility, puberty, sexual differentiation and development, metabolism, and insulin regulation. It isn’t just us verts; not only do we depend on an estrogen signaling network, but also many invertebrates, fungi, and plants. While many species can be affected by these chemicals, the fish make a model species for examining the effects of estrogen in the water.
Researchers first discovered the strange effects in the early 1980s, when intersexual fish were discovered in the United Kingdom. When examined closely (as in removed and put under a microscope) the fish’s gonads revealed some oddities. As you can see in the picture to the right (from the Boulder Creek study) the gonads appeared to be both ovary-like and testes-like. You’d suppose the discovery of dual-gendered fish would immediately become breaking news. Unfortunately, the original research wasn’t publicized for another decade or so, by which time the phenomena began to observed elsewhere. Now, intersexual fish have been found all over the world, in Tokyo, in the United States, and across Europe.
Here in Colorado, quite a few fish in Boulder Creek turned out to have it both ways: 20% of fish downstream from the treatment plant have intersex gonads (as opposed to none upstream.) But that wasn’t all. Dr. Vajda and his team revealed that more is going on in the creek than just mixed up sex. Upstream, there is a normal ratio of males to females. Downstream, females outnumber males 4 to 1. The few downstream males show decreased testicular sperm abundance, while upstream females suffer impaired ovarian development. On another odd note (though unrelated to human physiology) the downstream males have elevated plasma vitellogenin levels–in other words, they’re making yolk for eggs that they’ll never have.
So… is it just a coincidence? Or are Boulder residents actually changing local riparian ecosystems by using the bathroom? In order to find out, Dr. Vajda and his colleagues built a Fish Exposure Mobile, an RV gone wild. Containing a series of aquariums, the mobile could monitor up to 300 fish at one time, exposing them to upstream water, downstream water, or a combination of the two. Here, they used another Colorado native fish, the Fathead minnow (Pimephales promelas). These fish make handy test subjects, in addition to being small enough to fit in mobile aquariums. Like the suckers, they are common in streams from the mountains to the plains. But unlike the suckers, the minnows display obvious secondary sexual characteristics. For one, the males have a dorsal fatty pad where the females do not, which makes it easy to identify gender without, as Dr. Vajda puts it, snatching nads. Unfortunately, after only four days of exposure to the downstream water, at least 50% of the males had begun to change sex, rendering them difficult to identify. Feminization and demasculization of the males was so common that the dorsal pads on downstream fish were often missing. (Without the dorsal pads and other visual cues, researchers had to take samples of the reproductive tissue to identify gender.)
Of course, we shouldn’t just consider the fish. Our entire ecosystems are of immense and unmeasurable value. So, perhaps in that vein, Dr. Vajda is looking at ecosystem responses to estrogenic wastewater treatment plant effluent. He has found that diatoms and other macro invertebrates (which themselves thrive on diatoms) are also affected by contaminants in the water. The benthic fishes (like the white sucker) depend on both the diatoms and the macro invertebrates for a steady food supply. While they aren’t subject to hormonal changes, the surfactant properties of some of the contaminants mentioned above (such as soapy detergents) can affect the health of the diatoms, depleting the amount of available nutrition for the fish.
Meanwhile, estrogen in the water works actually as an advantage for some species, for instance, the invasive New Zealand mud snails. When exposed to estrogens, these snails become "superfemales" or "polyvaginal" breeding machines. These snails feed on the diatoms, competing with the macro invertebrates. Unfortunately, fish like the suckers can’t break the shells of the mud snail, so the snails are not subject to predation. Without any natural predators or parasites in this environment, these snails are already at an advantage. In other words, if we add more estrogen to the water, we may be dangerously tipping the scales in the favor of a highly invasive species.
But back to the fish. Dr. Vajda is now looking beyond Boulder Creek at 40 other sites for similar situations. The Fish Exposure Mobile II looked the at the waters around Vail, but didn’t find near the same levels of estrogens beyond the treatment plant as they did in Boulder. Since there were no minnows present, they looked at a local species, the sculpin. There, no intersex fish were found. Vail’s treatment plant is quite a bit more state-of-the-art than Boulder. Also, in this case, size matters. "Vail is too small," says Dr. Vajda. The big cities down on the plains are another story. Vajda and his crew have found intersex fish and skewed sex ratios in both Denver and Colorado Springs.
Incidentally, Boulder is planning to spend 55 million dollars to improve their water treatment plants–not for the sake of the fish, but I’m sure the fish won’t mind. It might be easier to focus on cleaning up the water than it would be to change our habits… or even pinpoint which habits are having the worst effect. "This is just one of the many sources where humans are exposed… we’re getting it through our food, through our water bottles, through our energy, agriculture and military," says Dr. Vajda. So, what does it mean for you as a consumer? Drink tap or bottled water? Dr. Vajda suggests you need to find out for yourself… it’s your call as to whether chlorine or plastic is more dangerous. He also warns that there may be troubles with over-treating our water supply. Some research is going on into "living water", he tells us, but not really in the US. We have a long way to go. (I blogged a bit about flowforms about a year ago, and I sadly agree… we have a long way to go.)
Thanks to Dr. Alan M. Vajda for an excellent and informative lecture, and thanks to Dr. Alexander Cruz for inviting him to speak. All images used here can be found on the BASIN website.