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modules/m45558/index.cnxml

@@ -86,7 +86,7 @@
 <para id="fs-idm75019552">One of the most important consequences of ecosystem dynamics in terms of human impact is biomagnification. <term id="term-00021">Biomagnification</term> is the increasing concentration of persistent, toxic substances in organisms at each successive trophic level. These are substances that are fat soluble, not water soluble, and are stored in the fat reserves of each organism. Many substances have been shown to biomagnify, including classical studies with the pesticide dichlorodiphenyltrichloroethane (DDT), which were described in the 1960s bestseller, <emphasis effect="italics">Silent Spring</emphasis> by Rachel Carson. DDT was a commonly used pesticide before its dangers to apex consumers, such as the bald eagle, became known. In aquatic ecosystems, organisms from each trophic level consumed many organisms in the lower level, which caused DDT to increase in birds (apex consumers) that ate fish. Thus, the birds accumulated sufficient amounts of DDT to cause fragility in their eggshells. This effect increased egg breakage during nesting and was shown to have devastating effects on these bird populations. The use of DDT was banned in the United States in the 1970s.</para>
 <para id="fs-idm24016">Other substances that biomagnify are polychlorinated biphenyls (PCB), which were used as coolant liquids in the United States until their use was banned in 1979, and heavy metals, such as mercury, lead, and cadmium. These substances are best studied in aquatic ecosystems, where predatory fish species accumulate very high concentrations of toxic substances that are at quite low concentrations in the environment and in producers. As illustrated in a study performed by the NOAA in the Saginaw Bay of Lake Huron of the North American Great Lakes (<link target-id="fig-ch20_01_07"/>), PCB concentrations increased from the producers of the ecosystem (phytoplankton) through the different trophic levels of fish species. The apex consumer, the walleye, has more than four times the amount of PCBs compared to phytoplankton. Also, based on results from other studies, birds that eat these fish may have PCB levels at least one order of magnitude higher than those found in the lake fish.</para>
 <figure id="fig-ch20_01_07">
-<media id="fs-idm101096304" alt="The illustration is a graph that plots total PCBs in micrograms per gram of dry weight versus nitrogen-15 enrichment, shows that PCBs become increasingly concentrated at higher trophic levels. The slope of the graph becomes increasingly steep as consumer levels increase, from phytoplankton to walleye.">
+<media id="fs-idm101096304" alt="The illustration is a graph that plots total PCBs in micrograms per gram of dry weight versus nitrogen-15 enrichment. It shows that PCBs become increasingly concentrated at higher trophic levels. The slope of the graph becomes increasingly steep as consumer levels increase, from phytoplankton to walleye.">
 <image mime-type="image/jpg" src="../../media/Figure_20_01_07.jpg" width="360"/>
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 <caption>This chart shows the PCB concentrations found at the various trophic levels in the Saginaw Bay ecosystem of Lake Huron. Notice that the fish in the higher trophic levels accumulate more PCBs than those in lower trophic levels. (credit: Patricia Van Hoof, NOAA)</caption>

modules/m63037/index.cnxml

@@ -145,7 +145,7 @@
         <title>Consequences of Food Webs: Biological Magnification</title>
 <para id="fs-idm13265440">One of the most important environmental consequences of ecosystem dynamics is biomagnification. <emphasis>Biomagnification</emphasis> is the increasing concentration of persistent, toxic substances in organisms at each trophic level, from the primary producers to the apex consumers. Many substances have been shown to bioaccumulate, including classical studies with the pesticide <emphasis effect="bold">d</emphasis>ichloro<emphasis effect="bold">d</emphasis>iphenyl<emphasis effect="bold">t</emphasis>richloroethane (DDT), which was published in the 1960s bestseller, <emphasis effect="italics">Silent Spring</emphasis>, by Rachel Carson. DDT was a commonly used pesticide before its dangers became known. In some aquatic ecosystems, organisms from each trophic level consumed many organisms of the lower level, which caused DDT to increase in birds (apex consumers) that ate fish. Thus, the birds accumulated sufficient amounts of DDT to cause fragility in their eggshells. This effect increased egg breakage during nesting and was shown to have adverse effects on these bird populations. The use of DDT was banned in the United States in the 1970s.</para>
 <para id="fs-idp13422016">Other substances that biomagnify are polychlorinated biphenyls (PCBs), which were used in coolant liquids in the United States until their use was banned in 1979, and heavy metals, such as mercury, lead, and cadmium. These substances were best studied in aquatic ecosystems, where fish species at different trophic levels accumulate toxic substances brought through the ecosystem by the primary producers. As illustrated in a study performed by the National Oceanic and Atmospheric Administration (NOAA) in the Saginaw Bay of Lake Huron (<link target-id="fig-ch46_02_03"/>), PCB concentrations increased from the ecosystem’s primary producers (phytoplankton) through the different trophic levels of fish species. The apex consumer (walleye) has more than four times the amount of PCBs compared to phytoplankton. Also, based on results from other studies, birds that eat these fish may have PCB levels at least one order of magnitude higher than those found in the lake fish.</para>
-<figure id="fig-ch46_02_03" class="ost-tag-lo-apbio-ch37-s02-aplo-4-14 ost-tag-lo-apbio-ch37-s02-aplo-4-15"><media id="fs-idp108251952" alt="The illustration is a graph that plots total PCBs in micrograms per gram of dry weight versus nitrogen-15 enrichment, shows that PCBs become increasingly concentrated at higher trophic levels. The slope of the graph becomes increasingly steep from phytoplankton (the primary consumer) to walleye (the tertiary consumer).">
+<figure id="fig-ch46_02_03" class="ost-tag-lo-apbio-ch37-s02-aplo-4-14 ost-tag-lo-apbio-ch37-s02-aplo-4-15"><media id="fs-idp108251952" alt="The illustration is a graph that plots total PCBs in micrograms per gram of dry weight versus nitrogen-15 enrichment. It shows that PCBs become increasingly concentrated at higher trophic levels. The slope of the graph becomes increasingly steep from phytoplankton (the primary consumer) to walleye (the tertiary consumer).">
 <image mime-type="image/jpg" src="../../media/CNX_AP_Bio_46_02_PCBchart.jpg" width="320"/>
 </media>
 <caption>This chart shows the PCB concentrations found at the various trophic levels in the Saginaw Bay ecosystem of Lake Huron. Numbers on the x-axis reflect enrichment with heavy isotopes of nitrogen (<sup>15</sup>N), which is a marker for increasing trophic level. Notice that the fish in the higher trophic levels accumulate more PCBs than those in lower trophic levels. (credit: Patricia Van Hoof, NOAA, GLERL)</caption></figure><para id="fs-idp35207760">Other concerns have been raised by the accumulation of heavy metals, such as mercury and cadmium, in certain types of seafood. The United States Environmental Protection Agency (EPA) recommends that pregnant women and young children should not consume any swordfish, shark, king mackerel, or tilefish because of their high mercury content. These individuals are advised to eat fish low in mercury: salmon, tilapia, shrimp, pollock, and catfish. Biomagnification is a good example of how ecosystem dynamics can affect our everyday lives, even influencing the food we eat.</para>

modules/m66702/index.cnxml

@@ -84,7 +84,7 @@
 <section id="fs-idp117234848">
 <title>Consequences of Food Webs: Biological Magnification</title>
 <para id="fs-idm13265440">One of the most important environmental consequences of ecosystem dynamics is biomagnification. <term id="term-00010">Biomagnification</term> is the increasing concentration of persistent, toxic substances in organisms at each trophic level, from the primary producers to the apex consumers. Many substances have been shown to bioaccumulate, including the pesticide <emphasis effect="bold">d</emphasis>ichloro<emphasis effect="bold">d</emphasis>iphenyl<emphasis effect="bold">t</emphasis>richloroethane (DDT), which was described in the 1960s bestseller, <emphasis effect="italics">Silent Spring</emphasis>, by marine biologist Rachel Carson. DDT was a commonly used pesticide before its dangers became known. In some aquatic ecosystems, organisms from each trophic level consumed many organisms of the lower level, which caused DDT to increase in birds (apex consumers) that ate fish. Thus, the birds accumulated sufficient amounts of DDT to cause fragility in their eggshells. This effect increased egg breakage during nesting and was shown to have adverse effects on these bird populations. Carson's combination of scientific knowledge and illuminating writing helped raise awareness about overall environmental issues as well as the specifics of the pesticide. The use of DDT was banned in the United States in the 1970s.</para><para id="fs-idp13422016">Other substances that biomagnify are polychlorinated biphenyls (PCBs), which were used in coolant liquids in the United States until their use was banned in 1979, and heavy metals, such as mercury, lead, and cadmium. These substances were best studied in aquatic ecosystems, where fish species at different trophic levels accumulate toxic substances brought through the ecosystem by the primary producers. As illustrated in a study performed by the National Oceanic and Atmospheric Administration (NOAA) in the Saginaw Bay of Lake Huron (<link target-id="fig-ch46_02_03"/>), PCB concentrations increased from the ecosystem’s primary producers (phytoplankton) through the different trophic levels of fish species. The apex consumer (walleye) has more than four times the amount of PCBs compared to phytoplankton. Also, based on results from other studies, birds that eat these fish may have PCB levels at least one order of magnitude higher than those found in the lake fish.</para>
-<figure id="fig-ch46_02_03"><media id="fs-idp108251952" alt="The illustration is a graph that plots total P C Bs in micrograms per gram of dry weight versus nitrogen 15 enrichment, shows that P C Bs become increasingly concentrated at higher trophic levels. The slope of the graph becomes increasingly steep from phytoplankton, the primary consumer, to walleye, the tertiary consumer.">
+<figure id="fig-ch46_02_03"><media id="fs-idp108251952" alt="The illustration is a graph that plots total P C Bs in micrograms per gram of dry weight versus nitrogen 15 enrichment. It shows that P C Bs become increasingly concentrated at higher trophic levels. The slope of the graph becomes increasingly steep from phytoplankton, the primary consumer, to walleye, the tertiary consumer.">
 <image mime-type="image/jpg" src="../../media/Figure_46_02_03.jpg" width="320"/>
 </media>