June 2006, Vol. 18, No.6

Waterline

Manure Microbes Lend Farmers a Hand

Infection-causing bacteria are battled by farmers to protect their animals’ health. But according to U.S. Agricultural Research Service (ARS) scientists, microbes — including several types of bacteria — can be a farmer’s ally when it comes to reducing the risk that antibiotic-containing manure may pose to the environment.

More than 9 million kg (21 million lb) of antibiotics were administered to U.S. farm animals and pets in 2004, according to an ARS news release. The trouble is that when animals excrete antibiotics and other pharmaceuticals that their bodies don’t use, the compounds may linger in the environment. This so-called pharmaceutical pollution can encourage bacteria to mutate and form strains that are resistant to current antibiotics, the news release notes.

Scott Yates, a soil scientist at the ARS George E. Brown Jr. Salinity Laboratory in Riverside, Calif., wanted to find out what happens to antibiotic-laced manure once it’s mixed with soil, as typically happens when livestock manure is spread onto farm fields as a fertilizer.

Yates and colleague Qiquan Wang developed a mathematical model which revealed that thriving manure microbes play an important role in determining how quickly one particular antibiotic, sulfadimethoxine, degrades. Some microbes in manure can digest and inactivate the excreted antibiotic.

According to Yates and Wang, farmers should try to create a hospitable environment for these tiny helpers. They should store waste from treated animals in a warm, moist place for as long as possible before spreading it onto fields. This gives the microbes an opportunity to act on an antibiotic before it has the chance to leach into soils and waterways.
 

Uncovering the Secret Lives of Deep-Sea Nomads

In addition to uncovering new and unusually large deep-sea fish species, recent results from the Mid-Atlantic Ridge Ecosystems program (MAR-ECO), an international study of the animals of the northern mid-Atlantic, have revealed the spawning habits of deep-sea pelagic fish. A news release issued by the Harbor Branch Oceanographic Institution (Fort Pierce, Fla.) states that this new information is useful in determining how deep-sea ecosystems should be managed to prevent habitat destruction by deep trawling activities.

Pelagic fish are those that live in open water, as opposed to staying near the sea floor. Adequate understanding of the deepwater fishes has been hard to achieve because deep-sea fish research has remained quite limited, the press release notes. Not since a deep-sea expedition in the 1870s has a research project collected as many bathypelagic (deeper than 1000 m) fish samples as the MAR-ECO project.

To date, MAR-ECO researchers have collected more than 300 fish species along the Mid-Atlantic Ridge — a massive undersea mountain range that runs almost the entire length of the Atlantic about midway between the continents. Of the samples collected, more than 30 were species never before known to inhabit the Mid-Atlantic Ridge region, and six appear to be species new to science, the news release notes.

The team also made some rare finds, including the largest dragonfish and anglerfish ever collected. Anglerfish, for example, typically can fit in the palm of a hand, but one sample weighed in at 16 kg (35 lb).

One of the major overall results of the MAR-ECO project to date is evidence that deep-sea pelagic fish are more closely associated with such features as the Mid-Atlantic Ridge than previously recognized. The group has collected several pieces of key evidence that these fish are congregating at the ridge, likely for spawning.

One key line of evidence was in the surprising numbers of several fish species collected, including tubeshoulders, which spurt bioluminescent liquid. Past deep-sea work has suggested the fish are rare and scattered, the press release states.

“We’re used to ones and twos,” said Tracey Sutton of the Harbor Branch Oceanographic Institution, “but we were getting tens, twenties, thirties — laundry baskets of these guys at 2,000 meters, which is pretty unusual,” the press release states. Most of those that were collected were gravid females, suggesting spawning activity, she said.

Using underwater video, MAR-ECO collaborator Franz Uiblein of the Norwegian Institute of Marine Research and his colleagues have shown that even slight disturbances to the deep-sea floor from fishing activities can lead to a loss of biodiversity — for instance, in a trawl’s path, suggesting that widespread deep trawling can have major impacts on deep-sea life.

While trawling on the Mid-Atlantic Ridge is rare, as deep-sea species become fished out in other areas, trawlers are wandering to new regions. If there are pelagic spawning aggregations at the ridge or other prominent features, they are likely to be critical to the preservation of the species involved, but they also are likely to become primary trawling targets, which could lead to devastating effects on spawning aggregations, according to the news release.