Decades of incoming strong acids have depleted the buffering capacity of some bodies of water and soils; they have run out of Alka-Seltzer, so to speak. This has happened in the Adirondack Mountains in New York, where more than 200 lakes have lost their fish life because of acidification (SI, Sept. 21, 1981). Similarly, the coastal-plain soils in Maryland have scant buffering capacity. Since 1971, Dr. David L. Correll of the Smithsonian Institution and a team of scientists have been ivestigating the Rhode River watershed, near Edgewater, Md. In a paper delivered in 1982 and published this past February in a book entitled Geological Aspects of Acid Deposition, he reports that the coastal plain is "very vulnerable to acid rain." Correll notes that over a seven-year period (1972-78) the mean spring pH of the larger streams in the Rhode watershed dropped from 6.3 to 5.8. Asked his opinion of SI's hypothesis concerning acid rain and its effect on spawning in tributaries of the bay, Correll said, "I've been saying the same thing. I think it's a serious concern that people should be working on." Correll says that striped bass, which used to spawn in the Rhode River system, no longer do so, and that yellow perch "have become extinct" in the watershed. This spring he is monitoring fish spawning and pH levels.
The precipitation (rain, snow, even fog) that falls on Maryland is very acid, as acid as any in the world. Its pH ranges from 4.45 to 3.5; that is 15 to 110 times more acid than normal. A rainstorm in Baltimore three years ago had a pH of 2.9, more than 700 times more acid than normal. When a heavy rain hits this flat coastal plain, it's like throwing a bucket of water on a rubber sheet. What had been up in the sky a few hours before collects in the streams, and the streams can suffer sudden acid pulses. If the pH of a stream isn't being monitored daily, no one will notice the pulse. In a matter of hours, or a day, or two days, the pH can rebound to 7 or more, and the only witnesses to the destructive pulses are the larval fish that have been killed.
According to Dr. Serge Doroshov, who worked on the acclimatization of striped bass in Russia before he defected in 1975—he has taught animal science at the University of California at Davis since 1977—striped bass larvae have difficulty tolerating pH levels below 7. "Mortalities are higher in water with a low pH," he says. "I haven't seen the data [SI has for certain rivers], but with those pH levels I would speculate that striped bass larvae wouldn't survive. The larvae do best in water with a pH of 7.5 to 8.5. At Davis we raise them in water close to pH 8." Moreover, Doroshov adds, striped bass larvae are extremely sensitive to a sharp change of pH even within the favorable pH range. He cites two instances where a sudden change of pH by 0.8 to 1.0 caused 100% mortality.
Last year, the Power Plant Siting Program of the Maryland Department of Natural Resources (DNR) monitored the pH of the headwaters of 23 coastal streams feeding into the Chesapeake. The study was designed by Dr. Tony Janicki of Martin Marietta Environmental Systems of Columbia, Md. and Michael L. Bowman of the DNR. One of the criteria used by Janicki—whose doctoral thesis stemmed from his studies of acid-affected aquatic systems—was that the streams had historically supported spawning runs of white perch, yellow perch, American shad, hickory shad, alewives or blueback herring. These species tend to spawn farther up freshwater systems than do striped bass. Monitoring took place in March and April, and the streams were sampled weekly, not daily. In those two months all 23 streams experienced acid pulses, each dropping to pH 5.8 at least once. The pH of 14 of the streams fell at least once to 5.5, and six of the streams suffered slumps to a pH between 4.9 and 4.5.
Acid rain can mobilize aluminum and other metals toxic to fish—in other words, draw these metals from the soil into the water. A level of only .02 parts per million of dissolved aluminum in stream water is considered to be lethal to many larval fish. The Maryland DNR study revealed that dissolved aluminum levels in some Maryland streams were so high, up to 2.00 to 3.00 pm on occasion—100 to 150 times the lethal dose—that authorities in the field have strongly questioned the method of aluminum analysis. That research will be extended this spring.
Jay O'Dell, the DNR biologist in charge of migratory fish, helped Janicki pick the streams. O'Dell has walked them all for years, and he says, "I've noticed a decline in spawning runs in some streams in the last 14 years. There's no doubt about it. The river herring [alewife and blueback] runs are gone, or there are reduced populations. The same for yellow perch. Runs are gone that were heavy in the 1970s. The run of yellow perch [in the Rhode River Watershed] is gone, and so are two runs at the head of the Magothy River. Since 1978, yellow perch no longer spawn at all in some freshwater streams. The die-off seems to come in the egg and larval stages. White perch appear to be following the same trend. There are no obvious physical changes, no new pollution. I used to think it was PCBs or chlorine, but now, from what I know, I believe [the cause is] acid rain."
Since 1980, DNR biologist Jim Uphoff has conducted a trawl survey for larval striped bass in the Choptank, a river on the Chesapeake's Eastern Shore. Among other functions, the survey gives the state an early estimate of spawning success. Jim Price, a charter-boat captain in Oxford, Md., is usually out on the Choptank at the same time Uphoff is, catching mature striped bass for research purposes. Price's family has spent 100 years fishing the Choptank, and he's sick at heart at what he has seen. "Back in the '60s and early '70s, the Choptank was full of striped bass," Price says. "In the fall, you could run through 10 to 15 miles of breaking fish. Now we've got practically nothing." In November, Price petitioned the DNR to have striped bass declared a threatened species and thereby accorded protection. The striper happens to be Maryland's official state fish and is on its great seal.
The story that Price and Uphoff tell of striper spawning in the Choptank is the same. Reproduction in the springs of 1980 and 1981 was, in Uphoff's words, "a disaster." In both years, trawls showed that striped bass had reached the larval stage, but after several days of heavy rain they disappeared and presumably died. No pH measurements were taken. In 1982, the Choptank yielded a good crop of striped bass. "It was a fairly dry spring," says Price. Uphoff adds, "The flow stabilized when the eggs hatched, and the fish survived." There were heavy rains again last spring, and striped bass production was nil. "Originally I was the ultimate skeptic about acid deposition in the Chesapeake system," says Uphoff, "but I'm far from that now."
Acid rain may also be affecting striped bass spawning in North Carolina. Last spring, Dr. William W. Hassler, at North Carolina State, wanted to collect living striped bass eggs from the Roanoke River—which along with the Hudson and Chesapeake Bay has been traditionally thought of as a prime striper spawning ground—for feeding experiments. He found only 35% of them viable.
Runs of American shad also are down in North Carolina, and are way, way down in Chesapeake Bay. In 1970 the Chesapeake shad catch was five million pounds, but by 1980 it had declined more than 80% and Maryland imposed a ban on shad fishing.