Ocean food chain

This chapter reviews recent experimental evidence of a bacterial source of sodium channel blockers, principly TTXs. These findings support the hypothesis that procaryotic organisms produce TTXs which contaminate oceanic food chains. 

Ozone is vital to life it acts like a shield, protecting the earth s surface from destructive ultraviolet radiation. A decrease in ozone concentration in this protective layer would have some immediate consequences, including an increase in the incidence of skin cancer and eye cataracts. Other long-term effects include a reduced immune response, interference with photosynthesis in plants, and harmful effects on the growth of plankton, the mainstay of the ocean food chain. 

These carnivores are near the top of the ocean food chains and feed mainly on fish and squid, although they may also dine on penguins and some species of seals. Their sharp teeth are used for grasping and not chewing. 

Dissolved carbon dioxide is one of the most important diprotic acids in Earth s ecosystem. Box 11-1 describes imminent danger to the entire ocean food chain as a result of increasing atmospheric CO2 dissolving in the oceans. Reaction A in Box 11-1 lowers the concentration of C03 in the oceans. As a result, CaCOs shells and skeletons of creatures at the bottom of the food chain will dissolve by Reaction B in Box 11-1. This effect is far more certain than the effects of atmospheric CO2 on Earth s climate. 

The 1998 and 2002 Scientific Assessments of Stratospheric Ozone firmly established the link between decreased ozone and increased UV-B radiation. In humans, UV-B is linked to skin cancer. It also contributes to cataracts and suppression of the immune system. The effects of UV-B on plant and aquatic ecosystems are not well understood. However, the growth of certain plants can be slowed by excessive UV-B. Some scientists suggest that marine phytoplankton, which are the foundation of the ocean food chain, are already under stress from UV-B. If true, this could adversely affect supplies of food from the oceans. 

Aquatic pollution occurs when harmful, or potentially harmful effects, can result from the entry into the ocean of chemicals, particles, industrial, agricultural, and residential waste, noise, or the spread of invasive organisms. Most sources of marine pollution are land based. The pollution often comes from nonpoint sources such as agricultural runoff and windblown debris and dust Many potentially toxic chemicals adhere to tiny particles which are then taken up by plankton and benthos animals, most of which are either deposit or filter feeders. In this way, the toxins are concentrated upward within ocean food chains. Many particles combine chemically in a manner highly depletive of oxygen, causing estuaries to become anoxic. 

Radiocarbon (14C) is produced in the atmosphere by the cosmic ray neutron flux interacting with 14N[14N(n,p)14C], The 14C hot1 atom then equilibrates with atmospheric C02 which participates in the C-0 cycle and passes into the food chain (biosphere). Most of the radiocarbon is taken up by the oceans which constitute the largest reservoir of C02 within the secondary geochemical cycle. 

Mercury point sources and rates of particle scavenging are key factors in atmospheric transport rates to sites of methylation and subsequent entry into the marine food chain (Rolfhus and Fitzgerald 1995). Airborne soot particles transport mercury into the marine environment either as nuclei for raindrop formation or by direct deposition on water (Rawson etal. 1995). In early 1990, both dimethylmercury and monomethylmercury were found in the subthermocline waters of the equatorial Pacific Ocean the formation of these alkylmercury species in the low oxygen zone suggests that Hg2+ is the most likely substrate (Mason and Fitzgerald 1991 Figure 5.1). 

Bertine, K.K. and E.D. Goldberg. 1972. Trace elements in clams, mussels, and shrimp. Limnol. Ocean. 17 877-884. Besser, J.M., T.J. Canfield, and T.W. La Point. 1993. Bioaccumulation of organic and inorganic selenium in a laboratory food chain. Environ. Toxicol. Chem. 12 57-72. 

Because of the complex cycling of MMHg in the ocean, carnivorous fish at the top of the food chain could be naturally enriched in mercury. But mercury levels in seabird feathers show significant increases over time, suggesting that anthropogenic emissions have similarly caused an increase in fish tissues. 

The impact of marine food is directly proportional to the rate of consuming each level of marine food chain. For example, the phytoplanktons, seaweeds/grasses are consumed by the next level of ecological pyramid, the herbivores, which consists of zooplanktons, parrot fish, oyster, shrimp, clams, crabs scallops, tilapia, lobster, etc. Oceans carnivores... 

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