Bhoopander Giri. Suspended Matter in the Aquatic Environment. Doeke Eisma.
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Impacts on intertidal habitats, such as salt marshes, mangroves, macroalgal beds and coral reefs, are assumed to be a percent loss if a threshold thickness dose is exceeded for any interval of time. The threshold is based on observational data for salt marsh impacts French et al. Wildlife birds, mammals, and reptiles are primarily impacted by direct exposure to floating oil, ingestion of contaminated prey or depletion of food resources. Models used to assess impacts of oil on wildlife populations are summarized in Table In evaluating the wildlife impacts of the Exxon Valdez , Ford et al.
Oiled and dead birds are scavenged and may sink at sea. The percent stranded is related to the trajectory of the carcasses. Ford et al.
Wildlife are assumed to move randomly within the habitats they normally use for foraging. The dose is estimated from the oil thickness, path length through the oil, and the width of a swimming bird. A portion of wildlife in the area swept by the slick is assumed to die based on the probability of encounter with the slick, dosage, and mortality once oiled. Estimates for these probabilities are derived from information on behavior and field observations of mortality after oil spills. French and Rines performed hind-casts on 27 oil spills to validate the wildlife impact model.
The results showed that the model is capable of hind-casting the oil trajectory and shoreline oiling, given 1 accurate observed wind data following the spill, and 2 a reasonable depiction of surface currents. Since winds and currents are the primary forcing variables on oil fate, obtaining accurate data on these is very important to the accuracy of any simulation. The accuracy of the impact model is primarily dependent on the accuracy of the wildlife abundance data for the time and location of the event. In the validation study, regional mean abundances from literature sources were assumed.
In nearly all cases, impact information for a spill consists primarily of counts of rescued or dead wildlife. Model validation is necessary to illustrate where the model predicts reasonable estimates of impacts on wildlife. Modeling results show that the wildlife impact algorithm in the model is valid when input data on abundance are accurate French and Rines, In a few cases, the model estimated more birds killed than were observed.
These cases were for species impacts not normally assessed or reported. Even in cases where large efforts were made to recover oiled wildlife, such as following the Exxon Valdez , it is well recognized that many oiled animals are lost at sea or scavenged and not counted directly as oiled. Small and less visible species and. Sea birds and marine mammals—Oil slick encounter and subsequent mortality.
Fur seal model—Simulated population processes and mortality due to oiling. Sea birds—Estimate numbers oiled from strandings of oiled animals on beaches. Exxon Valdez —Experimental bird drift and loss rates to estimate the percent of oiled animals that would reach a beach and be stranded.
Thus, it is not possible to verify some of the model estimates of impacts. The model results point to where additional observations are needed to evaluate impacts to these less obvious species French and Rines, Oil toxicity models have been developed to estimate water column toxicity after an oil spill French, ; French McCay, As discussed above oil toxicity may be attributed to many different compounds. Exposure concentrations of each compound in the mixture, as well as their toxicities, must be estimated to quantify the toxicity of oil to water column organisms French et al. Typically, for surface releases of fuel and crude oils, only the PAH are dissolved in sufficient quantity and remain in the water long enough for their toxic effects to be significant.
The more turbulent the release i. For a subsurface release deep in the water column or for a gasoline or other product spill where the MAHs and lower molecular weight aliphatics are significant fractions of the oil, all of these compounds may cause significant acute toxic effects French, ; French McCay, Other, less familiar models may address the challenges of modeling oil spill fates and effects at least as well. Fish and their eggs and larvae are affected by dissolved contaminant concentration in the water or sediment.
Mortality is calculated using LC 50 , corrected for temperature and duration of exposure, and assuming a log-normal relationship between percent mortality and dissolved concentration. Movements of biota, either active or by current transport, are accounted for in determining concentration and duration of exposure. Organisms killed are integrated over space and time by habitat type to calculate a total kill. Lost production of plants and animals at the base of the food chain is also computed.
Lost production of fish, shellfish, birds, and mammals due to reduction or contamination of food supply is estimated using a simple food web model French et al. In addition to the direct kill and food-web losses of eggs and larvae, young-of-the-year fish may be lost via habitat disruption. This is included in the model for wetland and other nursery habitats destroyed by lethal concentrations or oiling.
Losses are related to the habitat loss. Thus, recovery of spawning and nursery habitat in wetlands follows recovery of plant biomass and production French et al. Success of a model simulation is dependent on both the algorithms and the accuracy of the input data. Results of the validation exercises have shown the algorithms provide reasonably accurate results. The most important input data in determining accuracy of results are winds, currents, and biological abundance of the affected species.
These data inputs need to be site- and event-specific for an accurate model estimate of impacts of a spill. Thus, the limitations of modeling are largely driven by the availability of these input data French and Rines, ; French, a,b,c. While oiled wildlife and shoreline habitats may be observed and quantified in the field after a spill, it is difficult and often infeasible to measure directly impacts to aquatic biota in the water column. To characterize fully the impact by field sampling, water and sediment samples would be needed at frequent time intervals over the first few weeks after the release and especially in the first hours , and with enough spatial coverage to characterize the extent of contamination.
In addition, comprehensive sampling of each of the species affected is needed in the exposed and unaffected areas. Because marine organisms are patchy in their distribution, large numbers of stations and samples within stations are needed to map abundance accurately.
Such extensive sampling of all or even selected species affected is often not feasible, given the rapidity at which the evidence disappears by scavenging of killed organisms and by migration of animals into the impacted area. Modeling may be used in combination with field sampling to quantify oil fate and impacts French, a,b,c. The weaknesses of modeling are related to our incomplete scientific knowledge of the impacts of oil spills.
Because oil spills are infrequent and unplanned events, which have most of their effects on organisms over a very short time, it is very difficult to obtain quantitative information with which to develop and verify models. The implementation of NRDA regulations under OPA has facilitated the gathering of quantitative data on spills, and provided opportunities for improving and verifying models. Effects on communities will be discussed from the standpoint of habitat types in which they occur. Two broad habitat categories are considered: 1 biogenically-structured habitats, and 2 inorganic substrates, such as intertidal rock, sand, and subtidal muds.
Long-term and chronic effects are likely to be expressed as residual damage from oil spills to biogenically-structured communities, such as coastal wetlands, reefs, and vegetation beds. Effects of oiling on biogenically-structured habitats may result from acute damage on habitats such as coral. Here the concern is that even though oil may not persist following an oil spill, the time required for recovery of damaged populations of organisms that provide the physical structure of the habitat may be many years.
In some biogenic habitats, such as mangroves and mussel beds, oil can sometimes penetrate into the lower-energy sediments associated with these habitats and have potentially long-lasting effects. Biological communities that are integrally dependent on physical structures, which are themselves formed by living organisms, may be inherently slow to recover from severe impacts.
In some cases where the structure-forming species actually stabilize the habitat, it is conceivable that permanent modification of that habitat could result from an acute incident that kills the key structuring species. Recovery from the effects of an oil spill in a community in which organisms provide the physical structure of the habitat depends on structural damage incurred during cleanup operations, the persistence of contamination, and the inherent ability of the community to recover.
The Oil in the Sea report focused extensively on the effects of oil spills on tropical habitats including coral reef ecosystems and mangroves. At the time, there were multiple field studies documenting effects on corals including decreased feeding response, coral colonization and premature expulsion of coral planula.
One lament of the Oil in the Sea report was the lack of information on concentrations and composition of oil in the water that prevented comparison of spill effects between coral sites. Since , a wealth of field and laboratory studies have increased our knowledge of the effects of oil on coral reefs. The Galeta spill into Bahia las Minas, Panama is arguably the most studied oil spill in the tropics.
Large amounts of medium weight crude oil see Box spilled into mangroves, seagrass beds, and coral reefs on the Caribbean coast of Panama Burns and Knap, ; Jackson et al. Another notable tropical oil spill was the consequence of the Persian Gulf War in where 1,, tonnes of oil were spilled into the marine environment Price and Robinson, Despite a fold difference in total volume of oil spilled, the long-term effects greater than five years of oil in Panama were more pronounced and detrimental due likely to repeat inoculation of oil from the surrounding mangroves into the coral ecosystem.
In contrast, no long-lasting effects to the coral reef ecosystem were reported from the Persian Gulf War spills Price and Robinson, Corals located in intertidal reef flats are exposed to oil slicks and are more susceptible to damage and death than corals in subtidal reefs. Coral located subtidally or in areas with high wave action are not directly exposed to the marine surface layer where oil slicks can coat them.
Instead, only the water-soluble fraction of oil generally affects submerged coral. The water-soluble fraction is primarily composed of benzene, toluene, ethylbenzene, and xylene, which can rapidly evaporate to the atmosphere. One laboratory study found that 15 percent of the benzene and toluene and 80 percent of the xylene were lost after 24 hours of exposure to the atmosphere Michel and Fitt, Acute and chronic exposures of oil on coral have been studied in the laboratory and field reviewed by Peters et al, The symbiotic algae associated with coral are affected after 24 hours of exposure to the water-soluble fraction of oil benzene, toluene, ethylbenzene, and xylene; see Box Photosynthetic capacity can recover fully if there is only short-term exposure to oil less than 72 hours , and no adverse affects were measured for exposure of less than one hour Michel and Fitt, Mixtures of dispersants and oil are more toxic to coral than just the oil Peters et al, Branching coral e.
Montastre , Bak, Mussels often occur in dense intertidal aggregations and their interlocking byssal threads provide a low-energy habitat with protection from the rigors of breaking waves above the bed. The interstices of mussel beds are micro-habitats rich in intertidal life Ricketts and Calvin, As with other bivalves, mussels effectively accumulate high concentrations of a variety of contaminants including petroleum hydrocarbons from the water and their food.
Mussels can be affected by the accumulation of petroleum compounds. Low concentrations of petroleum hydrocarbons can interfere with cellular and physiological processes like cellular immunity McCormick-Ray, ; Dyrynda et al. Thus, there is a basis for expecting population impact under some conditions. Oil exposure or vigorous cleanup of the intertidal zone results in damage to these beds, and it may take years for the beds to re-establish their former richness.
At the same time mussel beds effectively trap oil and under some circumstances allow the oil to persist for years after a spill. For example, after a 7, tonnes spill into a tropical estuary with mangrove habitats, damage to mussels was apparent one year after the spill Garrity and Levings, A spill of Bunker C fuel oil, spilled from a collision of two tankers in San Francisco Bay in , resulted initially in smothering of intertidal invertebrates.
Five years after the spill, there was no evidence of long-lasting effects of the oil spill on recruitment patterns of intertidal invertebrates in high energy environments Chan, Onshore winds kept the oil trapped in deep bays near the release site for six days, but shifting winds and rainfall runoff caused the slicks to spread to adjacent areas. Dispersants were applied 21, L starting nine days after the spill.
Eventual impacts resulting from dispersant application could not be separated out from other factors. About 82 km of coastline were heavily oiled, including more than 1, ha of mangrove forests, intertidal reef flats, and subtidal flats and seagrass beds. These habitats received extremely heavy dosing of a medium-heavy crude oil. There was some shoreline cleanup on beaches and rocky shores, and channels were dug into mangroves in an effort to increase oil flushing from interior areas.
Large expanses of mangrove forest were inaccessible, however, and no oil removal was conducted there. Approximately 69 ha of mangrove forest dominated by the red mangrove, Rhizophora mangle were killed; sublethal impacts affected approximately ha Duke et al. The spill affected a biological preserve at the Smithsonian Tropical Research Institute, where biological baseline studies had been conducted since , sixteen years pre-spill.
Because of these extensive baseline data, the U. Minerals Management Service funded studies of the fate and effect of the oil in this tropical ecosystem for five years Keller and Jackson, ; many important findings have resulted. Oil in surficial soils degraded within six months; however, pools of oil trapped in mangrove soils showed little degradation, and chronic re-oiling of adjacent areas occurred for at least five years Burns et al.
Oil concentrations in bivalves were times background five years post-spill, with seasonal highs associated with periods of oil remobilization. The mangrove fringe along the outer coast, lagoons, and tidal creeks was frequently re-oiled, resulting in high prop root mortality and severe impacts on attached populations and communities that was most severe five years later Garrity et al. Where the oil floated over the reef flats, there was little mortality. The spill occurred, however, during a period of low tides, and oil was trapped on the seaward borders of the reef flat.
Wherever the reef flat was in direct contact with the oil, there was extensive mortality, and the effects persisted for over five years for sessile species Cubit and Connor, Mortality to intertidal communities and organisms was not a widespread, toxic effect of oil mixed in water, because the oil had weathered prior to stranding.
A primary factor in the recovery rate for sessile biota on reef flats was also how much of the plants and animals survived the spill and cleanup, and then vegetatively spread or washed in from nearby habitats afterwards—an important factor in cleanup design. In most areas, subtidal seagrass beds Thalassia showed sublethal impacts but recovered within eight months. The exception was the shoreward margins of the beds that died off in a band cm wide. The fauna of oiled seagrass beds remained highly altered for years post-spill Marshall et al. As mangrove forest and seagrass beds died back, oiled sediments were exposed and eroded, providing a chronic source of oiled sediment for re-deposition in adjacent habitats.
Subtidal reef corals Diplora clivosa, Porites asteroides, and Siderastrea siderea were affected to water depths of 6m, with a strong correlation between effects and oil concentrations in subtidal sediments Guzman et al. Affected coral populations had not started recovery after five years, as demonstrated by reduced sexual reproduction and larval recruitment, reduced populations of grazing fish, and very low recruitment of most formerly dominant coral species.
Minimal estimates of the time required for equivalent populations to become established were years Guzman et al. Studies among the habitats showed consistent patterns in recovery rates; that is, species with high reproductive potential, planktonic stages, and immigration or wave transport of fragments of surviving sessile species from adjacent habitats recovered more quickly, whereas those with low dispersal abilities and low reproductive potentials recovered more slowly.
Habitats where heavily oiled sediments persisted or where they were exposed to chronic re-oiling also recovered slowly. This spill provided some of the best evidence of the complexity of the tradeoffs of natural recovery versus the impacts of cleanup in sensitive environments.
Little evaluation of chronic or acute damage from laboratory studies exists. Among marine mammals, river otters Lutra lutra in the British Isles and Alaska, and sea otters Enhydra lutris and harbor seals Phoca vitulina in Prince William Sound, Alaska, all showed short-term population declines after oiling of their inshore marine habitats Baker et al. Reviews of shorter length i. Stephen Safe. Acute and chronic exposures of oil on coral have been studied in the laboratory and field reviewed by Peters et al, Major oil spills occur occasionally and receive considerable public attention because of the obvious attendant environmental damage, including oil-coated shorelines and dead or moribund wildlife, especially oiled seabirds and marine mammals. Around shallow-water natural petroleum seeps, the large kelp Macrocyctis pyrifera in the sporophyte stage does not accumulate petroleum hydrocarbons to very high concentrations Straughn, , and these kelp beds are well-developed despite continual inundation with surface oil.
In the Exxon Valdez spill, mussel beds were contaminated with oil, and it was decided not to disturb the mussel beds during cleanup operations. This decision was based partly on the food value of mussels to sea ducks, shorebirds, and sea otters A. Weiner, Alaska Department of Environmental Conservation, personal communication. As a consequence, oil persisted in these less energetic habitats within the intertidal zone. In these environments, oil was retained in the sediments underneath the mussel beds in an unweathered state for many years after the spill and would be expected to continue to persist Babcock et al.
There were at least 50 such mussel beds identified in western Prince William Sound, and it is likely that oil will only slowly decrease in these environments without intervention. Since it appears that some species of fish, sea birds and sea otters are still exposed to low levels of oil in western Prince Williams Sound 11 years after the spill, and some of the highest remaining concentrations of oil are found in mussel beds, these beds might be contributing to the continuing contamination of higher-trophic-level species e. Boehm et al. There is no consensus yet on which choice is best: immediate cleanup with destruction of mussel beds that may take many years to re-establish, or leaving them alone to.
Studies of oil effects on sea grass e. Little evaluation of chronic or acute damage from laboratory studies exists. Eelgrass meadows in the tidal zone are generally directly exposed to oil and die-off in the first year of an oil spill. In the subtidal areas, damage is limited to dying leaves. After the initial mortality in the first year, long-term effects of eelgrass are mixed.
Biomass, however, was the same between oiled and non-oiled areas Dean et al. In the Persian Gulf War spills, no difference between oiled or non-oiled seagrass meadows could be detected after one year Kenworthy et al. Reasons for resilience of eelgrass are speculative but are likely a result of life history patterns. Some species such as Zostera marina in Alaska propagate by lateral root growth, not by producing germinating seeds, and are less susceptible to oil in the sediment. Environmental parameters such as time of year of the spill relative to germination may also be important, but remains unexplored.
Subtidal kelps are apparently not particularly vulnerable to petroleum hydrocarbons.
Around shallow-water natural petroleum seeps, the large kelp Macrocyctis pyrifera in the sporophyte stage does not accumulate petroleum hydrocarbons to very high concentrations Straughn, , and these kelp beds are well-developed despite continual inundation with surface oil. Laboratory and field studies indicate that gametophytes of this species may be more sensitive than mature plants Reed et al.
Following the Exxon Valdez spill, some large subtidal kelps had different size distributions in oiled areas compared to non-oiled areas, but it is uncertain if this was a spill effect Dean et al. In the Nakhodka oil spill in Japan, no effects on subtidal kelp were reported from field surveys Hayashi et al. Like mussels, which retain oil in their byssus threads, kelp holdfasts are also low-energy environments that can retain oil for years after a spill.
For example, a small spill of diesel oil at Macquarie Island in the sub-Antarctic resulted in contamination of holdfasts of kelp that lasted for at least five years and inhibited the full recovery of the kelp-associated invertebrate community from the effects of the oil Smith and Simpson, Estuaries in many areas of the world are susceptible to exposure by oil because of the location of petrochemical industries in the coastal zone and transport of oil products, either by vessel or via pipelines, that either pass closely by or through estuaries.
Spills or operational discharges can potentially cause damage to intertidal vegetated habitats, including salt marshes and mangroves. These types of vegetation may occur separately or in combination with each other. Oil spills are known to cause severe and long-term damage to mangrove and salt marsh ecosystems e. The vegetation and the structure that salt marshes and mangroves provide may be affected, sediments may be contaminated, and ecosystem functions may be impaired with regard to utilization by organisms, including important fisheries species, geochemical cycling, and stabilization of sediments.
Oiling effects may be limited or negligible and short-term when the oil exposure is minimal, the vegetative structure is not impacted either by the oiling or various cleanup procedures , and residual oil levels are minimal or rapidly weathered. Oiling effects are particularly great when oil coats the vegetation or is incorporated deeply in the sediments beneath the vegetation.
The negative effects of oil on marsh vegetation are dependent on the type of oil constituents, viscosity , the amount of oil, the amount of plant coverage, the depth of penetration of the oil into the marsh sediments, the season, and the type and effectiveness of any cleanup or remedial actions reviewed by Webb, ; Pezeshki et al.
Lighter and more refined oils such as No. Crude oils and heavy fuel oils are generally the same in overall effects on plants, i. The aboveground portion of smooth cordgrass is generally killed only when oil covers all plant surfaces. Regrowth from roots will occur soon after death of the aboveground portions of the plants.
If sediments are heavily contaminated by oil, then production of new shoots is problematic and plant recovery is diminished.
Oil spills are more damaging to smooth cordgrass during the spring growing season than in fall when the plants are beginning their dormancy. Regrowth the following spring after a fall oil spill does not appear to be greatly reduced. When high levels of crude and heavy fuel oils accumulate in the sediments or remain within the marsh for long periods, the result is complete death of large areas of smooth cordgrass. In a series of experimentally oiled salt marsh plots, cleanup techniques implemented 18 to 24 h after the application were not effective in removing oil that had penetrated the surface Kiesling et al.
When oil remained on the sediment surface, flushing techniques were most effective at removal, reducing levels of oil by 73 to 83 percent. When dispersants were added to the water during flushing, oil removal was only slightly enhanced. Clipping of vegetation followed by sorbent pad application to sediments was moderately effective, reducing added oil by 36 to 44 percent. Burning had a negative effect on oil removal; oil increased in sediments of burned plots compared to controls.
Consideration should be given to natural microbial breakdown of the oil that can be facilitated with fertilizers. When large amounts of oil are present on a marsh, damage from trampling during cleanup can be severe, causing damage to plants and forcing oil into the sediments Webb, Densities of animals in salt marshes may be reduced by acute, short-term toxic effects of crude oil that sharply increase mortality rates Anderson et al. Oil may persist in marsh sediments for many years Teal and Howarth, ; DeLaune et al. Populations of opportunistic infaunal organisms, such as capitellid and spionid polychaetes and nematodes, are often enhanced in oiled sediments if the concentrations are not high enough to be toxic DeLaune et al.
Many of these organisms in highly urbanized estuaries and in estuaries near petrochemical installations or petroleum production facilities may be acclimated to hydrocarbons Smith et al. Marsh sediments were contaminated with low levels of petroleum hydrocarbons, but there were few statistically significant negative relationships between animal density fish and decapod crustaceans and hydrocarbon concentration Rozas et al.
Further, hydrocarbon concentration was not important among the environmental variables measured in explaining animal densities. The conclusions of Rozas et al. The background levels found in the Galveston Bay marshes were similar to those found in other highly urbanized estuaries Overton et al. Even though oil may initially reduce the use of intertidal habitats by aquatic organisms Sanders, ; Burns and Teal, ; Maccarone and Brzorad, , habitat use may return to normal levels after the oil has undergone sufficient weathering Barber et al.
One of the most detailed post-spill studies was carried out on the long-term effects of No. The oil had its greatest effect, and persisted the longest, in the Wild Harbor marsh versus a control in Sippewissett marsh 4 km to the south. Marsh grasses contaminated with oil died. Recovery of the Wild Harbor marsh was well along five years after the spill,.
The population of fiddler crabs in the Wild Harbor marsh was reduced relative to that in Sippewissett marsh for at least seven years Krebs and Burns, Behavioral effects, abnormal burrow shapes, and reduced female-to-male ratios were seen in Wild Harbor. Crab density was negatively correlated with aromatic hydrocarbon concentrations within the marsh, as was the density of newly settled juveniles. Other sources of oils that may directly affect salt marshes or mangroves are produced water discharges. Results from Louisiana estuaries indicate that discharges of produced waters directly onto salt marshes will kill the vegetation, but discharges into receiving waters do not affect the peripheral marsh vegetation Boesch and Rabalais, a.
Within the Nueces Bay estuary of Texas, however, Caudle identified extensive marsh areas in the bay that were denuded of vegetation due to long-term exposure to produced water. Documented recovery times return to some precursor percent cover of vegetation, diversity, or height and biomass of plants for oiled marshes range from a few weeks to decades reviewed by Hoff, The reasons for longer recovery times were related to the following characteristics: 1 northern, temperate, cold environments, 2 the high organic content of the peaty soils, 3 sheltered location, 4 heavy oiling, 5 spills of fuel oils bunker C or No.
In contrast, recovery times of three years or less have been documented for sites at several locations in the Gulf of Mexico: Neches River, Texas Esso Bayway , Harbor Island, Texas pipeline, and a pipeline rupture in southeastern Louisiana Table These marshes exhibiting quicker recovery share the following characteristics: 1 warm climate, 2 more mineral-rich soils, 3 light to moderate oiling, 4 spills of light to medium crude oil, and 5 variety of cleanup methods that were less intrusive.
In many instances, cleanup techniques delayed recovery time, from physical disruption of roots, flushing of soils, thus lowering the soil surface below levels where vegetation could re-establish, and activities that mix oil deeper into the marsh soils. There are numerous documentations of the death, defoliation, genetic, and other damage to mangroves and their associated communities after exposure to oil e.
Damage to mangrove forests varies with the amount and toxicity of the spilled oil product s with or with. Oiling effects on mangroves differ with life history state and may affect the growth forms of young trees Getter, ; Devlin and Proffitt, A primary cause of death in oiled mangroves is reported to be the disruption of gas exchange when aerial roots are coated with oil and can no longer supply oxygen to root tissues below ground in hypoxic soils Teas et al. Oil can also be taken up by the root system, translocated to leaves, accumulate in the stomata, thereby interrupting transpiration Getter et al.
Oil can also disrupt root membranes and allow lethal concentrations of salt to accumulate in mangrove tissues Page et al. Oiling of mangroves following spills can lead to the death of those plants and ultimately unstable habitats and sediment erosion Nadeau and Berquist, ; Duke and Pinzon, ; Garrity et al. Following the death of large numbers of mangrove trees after the Galeta oil spill in Panama, many trees rotted and fell, seagrass rhizome mats disappeared, and sediments from these habitats eroded at rates up to several centimeters per day Jackson et al.
The eroded sediments and oil in various stages of degradation were deposited in neighboring habitats including seagrass beds and coral reefs, which had not been contaminated in the original spill. In many instances the residence times of oil in these deep mud habitats have stretched to decades, which prolongs ecosystem recovery. The degree of impact to mangroves is a function of the oil type, spill volume, duration of re-oiling, extent of oil coverage on exposed roots, and degree of substrate oiling.
Light, refined products can be acutely toxic, for example the jet fuel spill in Puerto Rico that killed 5. Heavier types of oil can lead to eventual death by smothering. Slicks passing though forests at high water often leave a band of oil at the water line, with minimal impacts to the trees. Greatest impacts occur where sediments are contaminated, such as along intertidal berms Getter et al. Black mangroves are most sensitive to oil because they osmoregulate by passing materials through the roots and the vascular system, and then out of the leaves.
When black mangroves are oiled, this osmoregulatory process facilitates the uptake of oil Getter et al. Impacts can be spatially variable healthy trees adjacent to dead trees and delayed for years. Because of the potential for damage during cleanup and to the difficulty of access into mangrove forests, intrusive cleanup is considered only under very heavy oiling conditions e. Recovery of oiled mangroves depends on the initial and residual oil loading as well as damages resulting from cleanup efforts.
Physical and chemical weathering of oil may be fairly rapid, occurring over a few months to a year, or gradual and long-term Burns et al. Two researchers have attempted to predict the rates of recovery of oiled mangrove habitats; each of these analyses is summarized in Table The earliest effort to describe the phases of recovery of oiled mangroves was by Lewis Lamparelli et al. They measured leaf area and herbivory, tree density, basal area, and tree height for Rhizophora mangle , Laguncularia racemosa , and Avicennia schaueriana.
Dotted line indicates time predicted for beginning of recovery of benthic fauna at Gladstone from Burns et al. Reduction in litter fall, reduced reproduction, and reduced survival of seedlings; death or reduced growth of young trees colonizing oiled site? High mortality is observed, and the oil impact can be measured in terms of major structural alterations. Tre mendous efforts worldwide have been mobilized to evaluate the nature, pres ence, magnitude, fate, and toxicology of the chemicals loosed upon the earth.
Among the sequelae of this broad new emphasis is an undeniable need for an articulated set of authoritative publications, where one can find the latest impor tant world literature produced by these emerging areas of science together with documentation of pertinent ancillary legislation.
Research directors and legislative or administrative advisers do not have the time to scan the escalating number of technical publications that may contain articles important to current responsibility. Rather, these individuals need the background provided by detailed reviews and the assurance that the latest infor mation is made available to them, all with minimal literature searching.
Selected pages Title Page. Table of Contents. Biodegradation Kinetics for Pesticide Exposure Assessment. Pharmacokinetics Metabolism and Carcinogenicity of Arsenic.