New evidence that chemical contaminants are finding their way into the deep-sea food web has been found in deep-sea squids and octopods, including the strange-looking 'vampire squid'. These species are food for deep-diving toothed whales and other predators.
In a study to be published Marine Pollution Bulletin, Michael Vecchione of the US National Oceanic and Atmospheric Administration (NOAA) Fisheries' National Systematics Laboratory and colleagues Michael Unger, Ellen Harvey and George Vadas at the Virginia Institute of Marine Science of the College of William and Mary report finding a variety of chemical contaminants in nine species of cephalopods, a class of organisms that includes octopods, squids, cuttlefishes and nautiluses.
"It was surprising to find measurable and sometimes high amounts of toxic pollutants in such a deep and remote environment," Vecchione said. Among the chemicals detected were tributyltin (TBT), polychlorinated biphenyls (PCBs), brominated diphenyl ethers (BDEs), and dichlorodiphenyl-trichloroethane (DDT). They are known as persistent organic pollutants (POPs) because they do not degrade and persist in the environment for a long time.
Cephalopods are important to the diet of cetaceans, a class of marine mammals which includes whales, dolphins and porpoises. Cephalopods are the primary food for 28 species of odontocetes, the sub-order of cetaceans that have teeth and include beaked, sperm, killer and beluga whales and narwhals as well as dolphins and porpoises.
Recent studies have reported the accumulation of POPs in the blubber and tissues of whales and other predatory marine mammals as well as in some deep-sea fish. Other investigators had speculated that the pollutants in marine mammals had resulted from feeding on contaminated squids. However, almost no information existed prior to this study about POPs in deep-sea cephalopods.
Vecchione and colleagues wanted to see if whales had a unique capacity to accumulate pollutants or if they were simply one of the top predators in a contaminated deep-sea food web (Fig.1).
The researchers collected nine species of cephalopods from depths between 1000 and 2000 metres in 2003 in the western North Atlantic ocean using a large mid-water trawl. Species were selected for chemical analysis based on their importance as prey and included the commercially important short-finned squid Illex illecebrosus, as well as cockatoo squid (Fig.2), 'vampire squid', and the large jelly-like octopus Haliphron atlanticus.
Twenty-two specimens were analysed for a variety of contaminants. One of the chemical pollutants, TBT, is an additive used to control growth of organisms and is found in antifouling paints for boats, wood preservatives, and many other products. TBT is an endocrine disrupting compound and has been detected in whales and dolphins. It has been regulated worldwide since the late 1980s, but has been a concern because of its extreme toxicity to marine invertebrates in the coastal environment.
Other chemical contaminants found in the specimens include polycyclic aromatic hydrocarbons (PAHs), found in all the samples, diphenyl ether (DPE), polychlorinated biphenyls (PCBs), and brominated diphenyl ethers (BDEs).
The researchers also detected DDT, a pesticide banned in the US in the 1970s but still used on a limited basis in some parts of the world to control diseases like malaria.
PCBs are a class of human-produced compounds used to insulate electrical transformers and capacitors and in coatings, sealants, adhesives, paints, wood floor finishes, and even in carbonless copy paper. PCB production was banned in the US in the 1970s. BDEs have been used as flame retardants in a variety of household products, from plastics to foam in furniture and fabrics.
An understanding how environmental processes and agricultural practices interact to determine the transport and fate of agricultural chemicals in the environment is essential for effectively addressing the widespread degradation of surface and ground waters from past, present, and future agricultural activities. While considerable research has been conducted at field or smaller scales, the holistic understanding of processes at the watershed scale, encompassing multiple environmental compartments, is generally lacking.
To improve understanding, scientists at the US Geological Survey (USGS) have conducted studies in five diverse agricultural settings across the country as part of the USGS national water-quality assessment programme.
The holistic study design, which was employed at each setting, focused on the catchments of small streams and included all of the important environmental compartments - surface water, ground water, the unsaturated zone, the streambed, and the atmosphere.
A detailed description of this whole-system study approach is published in the May-June issue of the Journal of Environmental Quality and serves as an introduction to a group of 13 companion papers that compare and contrast the results for the specific environmental compartments from the five settings in included the study.
Results from the companion papers show the value of this holistic study design.
Conclusions drawn from the interpretations of data in each of the environmental compartments are corroborated and enhanced by information from neighbouring compartments.
Paul Capel, who lead the study, stated: "Because of the holistic approach used, these investigations provide valuable information that can help optimise site-specific changes in agricultural practices to reduce the concentrations of nutrients, pesticides, and pesticide degradates in surface and ground waters and mitigate the impacts of agriculture on the environment."
At each of the five agricultural settings, a wide variety of field data - hydrologic, mineralogical, chemical, dissolved gas, and isotopic - were collected during 2003 and 2004.
In addition, several numerical models were employed to help interpret and simulate water and chemical transport and transformation processes within and between environmental compartments.
This work shows the value of a thorough understanding of the hydrologic system and water budget for an agricultural setting when seeking to understand water-quality issues.
