Marine Food Sources Research Articles

Toxicology and seafood toxins: domoic acid.

Marine and terrestrial food sources are susceptible to contamination by various industrial chemicals and microbial pathogens. Both types of hazard are amenable to regulatory assessment using a single toxicology data base, along with some knowledge of contaminant levels and consumption figures for food. On the other hand, regulatory problems persist with acutely toxic naturally occurring phycotoxins, which may accumulate unpredictably to toxic levels in seafood. However, a scarce supply of pure toxin often precludes the availability of acceptable toxicology studies describing their biological effects. An exception to this situation is domoic acid, a neurotoxin phycotoxin that produced numerous cases of severe human intoxication which demanded extensive toxicological study. This paper describes a series of ongoing studies initiated in the wake of the outbreak of domoic acid toxicity that occurred in 1987 in Eastern Canada.

Stable Isotopes of Sulfur, Carbon, and Nitrogen as Indicators of Trophic Level and Fish Migration in the Lower Mackenzie River Basin, Canada

Stable isotopes of sulfur, carbon, and nitrogen were used to investigate the incorporation of nutrients into food chains (fish, invertebrates, and plants) and the influence of migration on the nutritional origins of fish in two freshwater systems in the Mackenzie Delta region. Sulfur isotope analyses of fish muscle showed that broad whitefish (Coregonus nasus) in Travaillant Lake and lake whitefish (Coregonus clupeaformis) in the Kukjuktuk Creek system were migrant populations which had grown mostly on sources outside the local food base. A marine food source was indicated for the lake whitefish, while no specific source was determined for the broad whitefish. The δ15N clearly defined the trophic levels in the local food chains in both systems. Fish were in three levels in Travaillant Lake. Amphipods were in a level below the lowest fish and sediments and macrophytes were in the lowest level. The Kukjuktuk Creek fish were in two levels above a level including macrophytes, amphipods, and zooplankton. The δ13C varied widely even within single fish species local to Travaillant Lake. The δ13C did not differentiate migrants from local fish. Plants of both the C3 and C4 photosynthetic pathway were indicated by carbon isotopes.

Nitrogen and carbon isotopic composition of bone collagen from marine and terrestrial animals

The stable nitrogen and carbon isotope ratios of bone collagen prepared from more than 100 animals representing 66 species of birds, fish, and mammals are presented. The δ 15 N values of bone collagen from animals that fed exclusively in the marine environment are, on average, 9%. more positive than those from animals that fed exclusively in the terrestrial environment; ranges for the two groups overlap by less than 1%. Bone collagen δ 15 N values also serve to separate marine fish from the small number of freshwater fish we analyzed. The bone collagen δ 15 N values of birds and fish that spent part of their life cycles feeding in the marine environment and part in the freshwater environment are intermediate between those of animals that fed exclusively in one or the other system. Further, animals that fed at successive trophic levels in the marine and terrestrial environment are separated, on average, by a 3%. difference in the δ 15 N values of their bone collagen. Specifically, carnivorous and herbivorous terrestrial animals have mean δ 15 N values for bone collagen of + 8.0 and + 5.3%., respectively. Among marine animals, those that fed on fish have a mean δ 15 N value for bone collagen of + 16.5%., whereas those that fed on invertebrates have a mean δ 15 N value of + 13.3%. These results support previous suggestions of a 3%. enrichment in δ 15 N values at each successively higher trophic level. In contrast to the results for δ 15 N values, the ranges of bone collagen δ 13 C values from marine and terrestrial feeders overlap to a great extent. Additionally, bone collagen δ 13 C values do not reflect the trophic levels at which the animals fed. These results indicate that bone collagen δ 15 N values will be useful in determining relative dependence on marine and terrestrial food sources and in investigating trophic level relationships among different animal species within an ecosystem. This approach should be applicable to animals represented by prehistoric or fossilized bone in which collagen is preserved.

Stable nitrogen isotope ratios of bone collagen reflect marine and terrestrial components of prehistoric human diet.

The delta 15N values of bone collagen from Eskimos and from Northwest Coast Indians dependent on salmon fishing are about 10 per mil more positive than those from agriculturalists in historic times. Among prehistoric humans, two groups dependent on marine food sources show bone collagen delta 15N values that are 4 to 6 per mil more positive than those from two agricultural groups. The nitrogen isotope ratios of bone collagen from prehistoric inhabitants of the Bahamas are anomalously low for reasons that relate to the biogeochemical cycle of nitrogen in coral reefs.

Carbon-13 depletion in an estuarine bivalve: Detection of marine and terrestrial food sources.

Stable carbon isotope analysis was used to define the food sources of bivalve Chione (Austrovenus) stutchburyi in the Avon-Heathcote Estuary, Christchurch, New Zealand. δ13C values of C. stutchburyi tissue were significantly different (from -16.7‰ to -23.5‰ relative to the PDB standard) at five locations separated by less than 4 km but subject to different hydrological regimes. This is related to differences in the isotopic composition of the suspended particulate matter of the inflowing water. C. stutchburyi is shown to utilise carbon of terrestrial and marine origin depending upon its position within the estuary and local hydrology.

Toxins from Fish and other Marine Organisms

Sea creatures from virtually all marine phyla have been a source of food for humans from the earliest days of history, as soon as man began to explore his aquatic environment. Although, fish and shellfish have always been the principal objects of man's harvest from the sea, consumption of such diverse organisms as algae, echinoderms, or mammals has not exactly been negligible. Along with the exploration of marine food sources came the recognition that some species were tastier than others were, and that ingestion of certain other species caused discomfort, illness, or even death. Recent attempts to manufacture a fish protein concentrate, in order to help feed the world's expanding population, have directed attention to the question of marine toxins. Clearly, it could be a dangerous undertaking of far-reaching consequences if one were to catch fish indiscriminately, process the fish into a meal, and distribute the concentrate without knowing whether any of the processed fish are toxic or whether the toxins survive the processing. Indeed, of equal importance, with the problem of producing a palatable and inexpensive fish protein concentrate is the problem of producing one that is safe to eat. This chapter attempts to present a picture of the current state of the chemical knowledge of marine toxins. Emphasis is placed on toxins isolated from fish and shellfish, but toxins from other marine organisms that have been characterized are also included. Many of these species are used as food and many are implicated in the food chain of the marine organisms themselves, a chain which leads from plankton feeders and other herbivores to the large carnivorous fishes.