of dtiaerobiosis on photosynthetic rates of 

 turtle grass and Halophila deci piens. 

 I'hile photosynthesis was depressed in both 

 species, Halophila did not recover after a 

 24-hour exposure, whereas the recovery of 

 turtle grass was complete, possibly be- 

 cause of its greater ability to store oxy- 

 gen in the internal lacunar spaces. Such 

 an oxygen reduction, however, will have a 

 far greater impact on the faunal co;npo- 

 nents than on the plants. 



8.3 OIL 



With the Nation's continued energy 

 deciands, the transport of petroleum and 

 the possibility of new offshore drilling 

 operations threaten the coastal zone of 

 south Florida. The impact on marine and 

 estuarine communities of several large- 

 scale oil spills has been investigated; 

 laboratory studies have assessed the tox- 

 icity of oil to specific organisms. The 

 effects of oil spills, cleanup procedures, 

 and restoration on seagrass ecosystems 

 have recently been reviewed by Zienan 

 et al . (in press) . 



Tatem ot al . (1978) studied the tox- 

 icity of two crude oils and two refined 

 oils on several life stages of estuarine 

 shrimp. Refined Bunker C and number 2 

 fuel oil were more toxic to all forms than 

 were crude oils from south Louisiana and 

 Kuwait. The larval stages of the grass 

 shrimp ( Palaemonetes pugio ) were slightly 

 more resistant to the oil than the adults, 

 while all forms of the oils were toxic to 

 the larval and juvenile stages of the 

 white shrimp ( Penaeus setiferus ) and the 

 brown shrimp ( Penaeus aztecus ), both com- 

 mon grass bed inhabitants. Changes in 

 temperature and salinity, which are rou- 

 tine in estuaries, enhanced the toxic 

 effects of the petroleum hydrocarbons. 

 The greatest danger to aquatic organisms 

 seems to be the aromatic hydrocarbons as 

 opposed to the paraffins or alkanes. The 

 bicyclic and polycyclic aromatics, espe- 

 cially napthalene, are major sources of 

 the observed mortalities (Tatem et al . 

 1978). The best indicator of an oil's 

 toxicity is probably its aromatic hydro- 

 carbon content (Anderson et al . 1974; 

 Tatem et al . 1978)). 



The effects of oil-in-water disper- 

 sions and soluble fractions of crude and 



refined oils were evaluated for six spe- 

 cies of estuarine Crustacea and fishes 

 from Galveston Bay, Texas (Anderson et al . 

 1974). The refined oils were consist- 

 ently more toxic than the crude oils, and 

 the three invertebrate species studied 

 were more sensitive than were the three 

 fishes. 



The effects on seagrass photosynthe- 

 sis of exposure to sublethal levels of 

 hydrocarbons were studied by NicRoy and 

 Williams (1977). Plants exposed to low 

 levels of water suspensions of kerosene 

 and toluene shov;ed significantly reduced 

 rates of carbon uptake. Plants probably 

 are not the most susceptible portion of 

 the community; in boat harbors where sea- 

 grasses occur, the associated fauna are 

 often severely affected. 



In the vicinity of Roscoff, France, 

 den Hartog and Jacobs (1980) studied the 

 impact of the 1978 "Amoco Cadiz" oil spill 

 on the Zostera marina beds. For a few 

 weeks after the spill, the eelgrass suf- 

 fered leaf damage, but no long-term effect 

 on the plants was observed. Among the 

 grass bed fauna, filter-feeding amphipods 

 and polychaetes were most effected. The 

 eelgrass leaves were a physical harrier 

 protecting the sediments and infauna from 

 direct contact with the oil, and the rhi- 

 zome system's sediment-binding capabili- 

 ties prevented the mixing of oil with the 

 sediment. Diaz-Pi ferrer (1962) found that 

 turtle grass beds near Guanica, Puerto 

 Rico, suffered greatly when 10,000 tons of 

 crude oil were released into the waters on 

 an incoming tide. Mass mortalities of 

 marine animals occurred, including species 

 commonly found in grass beds, fany months 

 after the incident turtle grass beds con- 

 tinued to decline. 



In March of 1973, the tanker Zee 

 Colocotronis released 37,000 barrels of 

 Venezuelan crude oil in an attempt to free 

 itself from a shoal off the south coast of 

 Puerto Ric®. The easterly trade winds 

 moved the oil into Bahia Sucia and contam- 

 inated the beaches, seagrasses, and man- 

 groves. Observations v/ere made and sam- 

 ples collected shortly after the spill. 

 By the third day following the release, 

 dead and dying animals were abundant in 

 the turtle grass beds; and large numbers 

 of sea urchins, conchs, polychaetes, 

 prawns, and holothurians were washed up 



87 



