What are the Effects of Oil on Seagrass? - U.S. National Response ...

<strong>Oil</strong> or Chemical SpillNotificationcall <strong>the</strong> National Response Center at800-424-8802<strong>Oil</strong> Spill Responsein <strong>the</strong> Region IV Coastal Zone,contact <strong>the</strong> U.S. Coast GuardMarine Safety Office (MSO):MSO Wilmington, NC MSO Charleston, SC910-792-8408 843-724-7616MSO Savannah, GA MSO Jacksonville, FL912-652-4353 904-247-7310MSO Miami, FL MSO Tampa, FL305-732-0160 813-228-2189MSO Mobile, AL334-441-5121In <strong>the</strong> Region IV Inland Zone,contact <strong>the</strong> U.S. EnvironmentalProtection Agency:404-562-8700Inland Zone U.S. Coast Guard Offices <strong>are</strong>:MSO Huntington, WV MSO Louisville, KY800-253-7465 800-253-7465MSO Paducah, KY MSO Memphis, TN502-442-1621 901-544-3912State Pollution Response Contacts <strong>are</strong>:North Carolina South Carolina919-733-3867 Spill: 888-481-0125Office: 803-896-4000Georgia Florida404-656-4300 850-413-9911Alabama Mississippi334-242-4378 601-352-9100Tennessee Kentucky800-258-3300 800-928-2380<strong>What</strong> <strong>are</strong> <strong>the</strong><strong>Effects</strong> <strong>of</strong><strong>Oil</strong> onSeagrass?Document prep<strong>are</strong>d by:Region IVRegional Response TeamRRT IV Co-Chairs:U.S. Coast Guard 305-536-5651U.S. EPA 404-562-8721For more informational pamphlets concerning varioussubjects go to <strong>the</strong> RRT IV Web Site at www.nrt.org

<strong>What</strong> <strong>are</strong> Seagrasses?Seagrasses <strong>are</strong> found worldwide in shallow coastalwaters. Owing to <strong>the</strong> protection <strong>the</strong>y provide fromerosion, <strong>the</strong>ir role in sediment accretion, and <strong>the</strong>irprimary productivity, seagrasses <strong>are</strong> extremelyimportant. Seagrasses <strong>are</strong> unique because <strong>the</strong>y <strong>are</strong> landplants that have fully returned to <strong>the</strong> sea. Theyconstitute one <strong>of</strong> <strong>the</strong> most productive ecosystemsknown.High light levels <strong>are</strong> needed to sustain <strong>the</strong>ir high rate <strong>of</strong>productivity. As rooted plants <strong>the</strong>y also requiresediments for both attachment and nutrition. Therefore,seagrasses <strong>are</strong> primarily found in shallow coastal waters.Because <strong>of</strong> <strong>the</strong>ir sediment stabilization and highproductivity functions, seagrasses tend to link <strong>the</strong>coastal and <strong>of</strong>fshore ecosystems.Seagrass EcologyAs photosyn<strong>the</strong>tic organisms, <strong>the</strong>y require high levels <strong>of</strong>light to sustain <strong>the</strong>ir high rate <strong>of</strong> productivity.However, as rooted plants <strong>the</strong>y require sediments forboth attachment and nutrition. Thus, <strong>the</strong>y <strong>are</strong> restrictedto a narrow band <strong>of</strong> coastal waters where <strong>the</strong> <strong>of</strong>tenconflicting demands <strong>of</strong> man <strong>are</strong> <strong>the</strong> greatest.Seagrasses provide many important functions in <strong>the</strong>aquatic environment, including:• The leaves decrease current velocities <strong>the</strong>rebystabilizing sediments and increasing sedimentation<strong>of</strong> both organic and inorganic particles around <strong>the</strong>plants.• They bind toge<strong>the</strong>r to help stabilize <strong>the</strong> bottomstructure and reduce erosion. Their hold to <strong>the</strong>bottom is so effective that <strong>the</strong>y can persist through150 kt winds during hurricanes.• Nutrition for many organisms throughout <strong>the</strong> foodchain.• The leaves support large numbers <strong>of</strong> epiphyticorganisms, with a total biomass which <strong>of</strong>tenapproaches that <strong>of</strong> <strong>the</strong> plants <strong>the</strong>mselves.Seagrasses <strong>are</strong> positioned in <strong>the</strong> coastal zone betweenupland ecosystems and <strong>the</strong> <strong>of</strong>fshore oceanic ecosystem.As a result <strong>of</strong> <strong>the</strong>ir sediment stabilization and highproductivity functions, seagrasses tend to link <strong>the</strong>seo<strong>the</strong>rwise dissimilar ecosystems. Seagrass ecosystems<strong>are</strong> comparable to saltmarsh ecosystems in that <strong>the</strong>y trapmaterials and export quantities <strong>of</strong> plant and animalproducts to <strong>the</strong> open sea. These products range fromwhole leaves and stems, to detritus, to dissolved organicmatter, and to fauna that have consumed <strong>the</strong>se plants.The depth distribution <strong>of</strong> seagrass depends on a number<strong>of</strong> interrelated factors: light penetration, turbidity,substrate, currents, and waves. Any activity thatincreases turbidity or reduces light penetration in waterover seagrasses limits <strong>the</strong> growth and survival <strong>of</strong> <strong>the</strong>plants. Among human-related factors that have suchimpacts <strong>are</strong> dredging, sewage release, and oil pollution.Susceptibility Of Seagrass Ecosystems To<strong>Oil</strong> DamageThe potential for damage to seagrass ecosystems can bebroken down into two broad categories: susceptibilityand vulnerability. Susceptibility is taken to be <strong>the</strong>potential for damage to <strong>the</strong> plants and associatedcommunities due to contact with oil or oil-relatedchemicals, ei<strong>the</strong>r breakdown products or cleanupchemicals. In particular, certain components <strong>of</strong> bothcrude and refined products have high toxicity to marineorganisms in small concentrations. By comparison,vulnerability is largely a positional effect, reflecting <strong>the</strong>proximity <strong>of</strong> a particular grass bed to a potential hazard.Seagrass beds <strong>are</strong> especially vulnerable to damage anddegradation by human activities because <strong>of</strong> <strong>the</strong>ir locationin <strong>the</strong> shallow coastals seas where activities <strong>of</strong> man <strong>are</strong>greatest. The potential for damage is highest in grassbeds within harbors, estuaries, and lagoons, and in <strong>are</strong>asin close proximity to shipping lanes.Petroleum products can act to damage seagrassaecosystems in a variety <strong>of</strong> ways, including:• Direct mortality <strong>of</strong> organisms due to smo<strong>the</strong>ring,fouling, asphyxiation or poisoning.• Indirect mortality due to <strong>the</strong> death <strong>of</strong> food sourcesor <strong>the</strong> destruction or removal <strong>of</strong> habitat.• Destruction <strong>of</strong> juveniles using grass beds as anursery ground.• Incorporation <strong>of</strong> sublethal amounts <strong>of</strong> petroleumfractions into body tissues, potentially loweringtolerance to o<strong>the</strong>r stresses.• Reduction or destruction <strong>of</strong> <strong>the</strong> food or marketvalue <strong>of</strong> fisheries due to absorption <strong>of</strong>hydrocarbons.• Incorporation <strong>of</strong> potentially carcinogenic ormutagenic substances into <strong>the</strong> food chain.