A SURVEY OF POTENTIAL IMPACTS OF
ON ESTUARINE PRODUCTIVITY
MARINE ENGINES AND VESSELS PUBLIC WORKSHOP
(sponsored by U.S.E.P.A. Office of Air and Radiation)
Ann Arbor, Michigan
Nils E. Stolpe
July 29, 1992
(This information is the result of reviewing literature from varying
sources and is meant to indicate possible directions for further investigation
rather than to draw any definite - or indefinite - conclusions concerning
An increasing amount of attention is being directed towards the health of our living marine resources. Declining stocks of economically and/or ecologically important species of finfish and shellfish in recent years have generated a great deal of focused public scrutiny, unfocused legislation, high profile law suits and friction between competing user groups. Generally this culminates in attempts - usually successful - to fix the blame on (commercial) over-fishing, power generation or loss of "critical" habitat. But, having been employed by or for commercial fishermen for the past fifteen years, I have yet to be convinced that their efforts are up to the task of severely depleting so many stocks so rapidly. In fact the total commercial fishing effort in the Mid-Atlantic region on the traditional "inshore" species has probably increased less than 10% in the last ten years. Likewise, installed electrical generating capacity hasn't increased significantly in this time. And while coastal development, generally considered to be the prime cause of habitat destruction, has been continuing, in recent years it has been carried out in an increasingly controlled and environmentally responsible manner.
But what has changed? In 1979 the total number of boats registered in New Jersey, including most motorized craft but excluding jet skies and the larger documented vessels, was 110,000. In 1989 this number had risen to 173,000, an increase of 57%. Quoting Dr. William Fox, who as the National Oceanographic and Atmospheric Administration's Assistant Administrator for Fisheries is the head fisheries manager for the federal government, "Over 70 percent of the U.S. commercial and recreational landings that provide over $30 billion to the U.S. economy are composed of species associated with estuaries at some time in their life history. Seventy percent of our production is dependent upon the preservation of nearshore habitat." (taken from a presentation by Dr. Fox to the National Fisheries Institute, April, 1991). These critical estuaries are the site of most of the boating activity in the Mid-Atlantic and are obviously on the receiving end of most of the growth in that activity.
Through contacts with marine researchers, environmentalists and resource managers it was found that, with the exception of a few narrowly defined areas of investigation, virtually no recent work has been done on the impact of boating activity on the estuarine environment. Some studies were completed in the 1960's and early 70's (when recreational boating was carried on at a level significantly less intensive than it is today, boats being smaller and with much less power), some questions were raised, and then the research community directed its attention elsewhere. But it seemed as if, at least with the levels of recreational boating use that have become common in water bodies such as New Jersey's coastal bays, there might very well be an impact of such activities on at least some of the less tolerant finfish or shellfish species.
With this in mind, a literature review was begun aimed at identifying
negative impacts from sources that could be related to those that might
be generated by boating. These impacts were grouped into three categories:
direct physical stresses on aquatic organisms similar to those that might
be caused by vessel operation (impacts by propeller leading edges or hull
parts, propeller generated turbulence and shear forces, hull generated
rotational forces), negative impacts on the physical environment similar
to those that might be caused by vessel operation (increased thermal loading,
increased turbidity, disruption of stratification) and biological effects
of pollutants, particularly hydrocarbons, similar to boat engine emissions.
While little or no work is available directly assessing the impacts of
boat operation, enough has been done in related or similar areas to allow
inferences to be drawn regarding whether or not an actual potential exists
for such impacts.
DIRECT PHYSICAL STRESSES:
Some research has been carried out, primarily by the Corps of Engineers, on physical impacts to fish and invertebrates from commercial river traffic - barges and tow boats - and a significant amount has been done to assess the impact on aquatic organisms of passage through hydroelectric turbines or thermoelectric generating station cooling systems. Physical damage, principally occurring during passage through the circulating pumps, was reported as the major cause of entrainment mortality of aquatic organisms during normal power plant operation (Shubel and Marcy, 1978) and shearing and striking were determined to be the major causes of damage to fish passing through turbines (with significant damage - decapitation and losses of chunks of flesh - attributed to cavitation forces as well. Bell, 1974). However, other workers (Taylor and Kynard, 1985 and Cramer and Oligher, 1974) reported that cavitation in turbines was the chief cause of mortality of entrained organisms. (While the role of cavitation in turbine and pump induced injuries and mortality is poorly understood, there is general agreement that it is a factor).
The shear and rotational forces generated along the wetted surfaces of barge traffic on the upper Mississippi were reported to have caused damage to 20% to 50% of fish eggs in the area of passage (Holland, 1986). Propeller generated turbulence 17 meters behind a vessel pushing barges varied from 2,500 dynes/cm2 with unloaded barges going upriver to 50,000 dynes/cm2 with loaded barges going down river (Kilgore and Conley, 1987) and Morgan et al experimentally determined that shear stresses between 120 and 785 dynes/cm2 for 1 to 20 minutes were lethal to 50% of eggs and larvae of striped bass and white perch (1976). In laboratory tests on paddlefish and carp, significant differences in mortality were seen in larvae exposed to low versus high levels of turbulence similar to those resulting from commercial river traffic (Pearson et al, 1989).
There isn't agreement on either the magnitude of the forces generated
by particular types of vessel operation or pump and turbine impellers operated
under different conditions. Nor is there a consensus on the magnitude of
the forces required to cause a specific level of injury or death to particular
organisms. There is general agreement, however, that the disturbances to
the water column caused by vessels and by the impellers of large pumps
and turbines may be responsible for injuring or killing aquatic organisms
and that the eggs and larval stages of finfish and shellfish are much more
susceptible to damage by these forces than juveniles and adults.
IMPACTS ON THE PHYSICAL ENVIRONMENT:
Heat: To the extent that elevated temperatures may be a concern in an estuary under a particular set of conditions, added thermal input from any source could be significant. With an understanding of the intensity and distribution of boating activity in a particular estuary, it should be possible to model the effects of the resultant thermal inputs to determine under what conditions - if any - they could have any effect.
Turbidity: The deleterious effects of dredging induced turbidity on the estuarine environment are now commonly accepted and dredging projects are designed to minimize them. While adult finfish are capable of either avoiding or withstanding high levels of turbidity, eggs, larvae and juveniles can be severely impacted. Effects of increased turbidity include: smothering of sessile organisms, prolonged hatching time (Morgan, Raisin and Noe, 1983), reduction in growth, lessened feeding efficiency (Newcombe and MacDonald, 1991), impaired schooling ability (Pearson et al, 1989), and impaired growth of bottom vegetation due to lessened light penetration. While reported for only one species, herring larvae moved to higher levels of the water column as turbidity increased (Johnston and Wildish, 1982). Breitburg (1988) speculated that turbidity and other factors affecting feeding in the Chesapeake system might account for the difference between actual and predicted spawning success in striped bass while Morgan, Raisin and Noe reported that high turbidity levels could reduce larval survival in the same species by 57% (1983). Sediment loading and turbidity have long been recognized as significant factors in the successful hatching and development of salmonids.
Organic and inorganic sediments also play an important role in the movement and concentra-tion of toxic materials in the estuarine environment.
Disruption of Stratification: Temperature and density (salinity) stratification
during certain periods are characteristic of some estuaries. While
it is possible that intense boating activity might disrupt such stratification,
no descriptions of any other mechanisms capable of disrupting such stratification
nor any effects of such a disruption were discovered.
The effects of hydrocarbons and heavy metals on and their movements
through the marine environment have generated volumes of material that
need not be surveyed here. However, areas with particular relevance to
possible boating impacts include the concentration of these substances
through adsorption onto suspended particles and in the flocculent layers
of bottom sediments; the persistence of these substances in the marine
environment (Burns and Saliot, 1986); and their contributions to forming
microlayers at the air/water interface. Von Westerhagen et al (1987) reported
that surface microlayer materials significantly affected development and
survival of marine fish eggs and discussed the high susceptibility of thin-shelled
pelagic eggs to petroleum hydrocarbon-derived pollution of natural waters.
In Puget Sound it was demonstrated that exposure to surface microlayer
samples collected from urban bay sites resulted in increased chromosomal
aberrations in developing sole embryos and reduced hatching rates of sole
eggs. These effects were associated with high concentrations of contaminants,
including hydrocarbons and heavy metals.
From the foregoing, it is obvious that, given a high enough level of
boating activity, there could be some negative effects on the estuarine
environment or to fish stocks, particlarly at the more susceptible early
life stages. From here, then, we moved to a review of the available information
on boating usage (fortunately, a number of data collection efforts - including
the EPA initiative that has resulted in this workshop - were underway or
had been recently completed and will provide a reasonably solid basis for
BOATING USE LEVELS:
Going back to the early sixties (English, McDermott and Henderson, 1963), "extreme critical" boating use intensity - one that would have a significant toxic effect on fish life - was determined to be (converting their figures) at a level that used 18 gallons of fuel per acre-foot of lake volume per year. Eleven years later (Breidenback, 1974) "Saturation Boating Use" was determined for 5,100 acre Lake Geneva, Wisconsin for 600 boats with 9,000 total horsepower (300 boats with 5 hp engines used for trolling, 150 with 40 hp for water skiing and 150 with 10 hp for "boating" ). When converted, their figures yielded a 15 gallon per acre-foot per year fuel use (assuming a 5 month boating season).
These can be contrasted with the current situation in Barnegat Bay, New Jersey. Barnegat Bay is fairly typical of estuaries in the Mid-Atlantic region. Having a total area of 47,000 acres, an average depth of 4.5 feet, a maximum depth of about 13 feet and 44% of its area covered by less than three feet of water, it is the site of intensive recreational boating activity for four or five months each year. There are 11,500 slips in marinas, an unknown number at private residences, dry storage for 7500 boats and 45 boat launching ramps in Barnegat Bay. Thirty percent of New Jersey's recreational boating takes place on this bay (Rogers, Golden and Halpern, 1990). Using recently derived figures for recreational boating fuel use in New Jersey commissioned by the U.S. Fish and Wildlife Service (Price Waterhouse, 1992), it can be estimated that 10,344,000 gallons of fuel was used in recreational boating on Barnegat Bay in 1990 (30% of New Jersey's total recreational boating fuel consumption of 34,481,000 gallons). This represents a usage level of 50 gallons per acre-foot per year and hasn't generated any discernible interest as being "out of the ordinary" or in any way exceptional.
What were once considered to be "worst case" levels of boating activity
now appear to be regularly and significantly exceeded during normal recreational
use of coastal waters.
DIRECT PHYSICAL IMPACTS:
Looking at the potential for direct physical impacts of boating activity on estuarine organisms it was assumed that the propeller of a boat in motion would impact on a volume of water - and the finfish and shellfish eggs, larvae and juveniles in it not capable of escape - equivalent to the area swept by the prop moving through the water at the speed of the vessel (while this is probably underestimating the volume - and organisms - impacted considerably it is adequate for an initial approximation). A propeller 14 inches in diameter sweeps an area of approximately one square foot. At 30 miles an hour it would pass through and directly affect 3.6 acre-feet of water every hour. For comparison, an "average" base load generating station uses 150,000 cubic feet of water a minute - sixty boats worth - for condenser cooling. If all of the 19,000 boats in commercial storage (marina slip and rack) on Barnegat Bay were single screw craft capable of 30 miles an hour, a volume of water equivalent to the entire volume of the bay - 211,000 acre feet - would be completely swept by their propellers in only 3 hours of combined operation.
While not quantifiable at this time, it is hard to imagine that the
impacts on affected estuarine organisms - particularly the more fragile
eggs and larvae - of the propeller driving a boat at what are now accepted
as normal cruising speeds aren't dramatic. They might well be of the same
order of magnitude as those of the pumps and turbines in thermoelectric
or hydroelectric plants. [for
more on propeller impacts]
Because of a lack of accessible performance data (marine engines are for the most part unregulated) the potential impact of marine engine emissions is one that is hard to get a direct handle on, at least for modern engines. Using the Price Waterhouse recreational fuel use figures previously referred to and projecting the levels of emissions reported by Breidenback in 1974 gives a dated (and we hope inflated, based on the improved performance of today's motors) measure of these emissions. Returning to Barnegat Bay, estimating that 80% of the total recreational boating fuel is used by outboard motors, and applying Breidenback's conclusion that the "average" pre-1974 motor will contribute 2.5% of its fuel to the water during most of the time it is in use would result in releases to the Bay of almost 500 tons annually. Even assuming a significant improvement in outboard engine efficiency and emission control since 1974 and a corresponding reduction in the release of condensable material ("...found to contain parrafinic, olefinic and aromatic hydrocarbons, as well as small amounts of phenols and carbonyl com-pounds." Breidenback, 1974) to only 1% of the total fuel input, the yearly release is still 200 tons for Barnegat Bay and 600 tons for the entire state.
POSSIBLE OBM INPUTS INTO COASTAL WATERS (and how they were estimated):
* 11,000,000 gallons = 55,000,000 pounds = 25,000 tons/yr recreational
fuel use in Barnegat Bay
Assuming New Jersey has 1/50th of the total U.S. outboard boating activity (a conservative estimate given the length of the N.J. coastline and the abbreviated boating season here), then annual U.S. hydrocarbon inputs from OBMs could be 30,000 tons - mostly concentrated in the estuaries and near-shore waters. Total inputs of all petroleum products into the world ocean annually have been estimated to be from 1.7 to 8.8 million metric tons. The estimate for the total (worldwide) from urban runoff in 1985 was 40,000 tons and from industrial wastes was 200,000 tons. "While inputs from pleasure craft may be locally significant, we believe that the total amount of this input would not be on the same scale with the other in-puts."(Steering Committee ..., 1985). Since 1981 total oil inputs from shipping into the world's oceans declined 60% to 568,000 tons (Marine Pollution Bulletin, 1990).
While these estimates (and I hesitate to refer to them even with the level of accuracy that "estimate" implies) are nowhere near conclusive, they are an indication that, in spite of the Academy's belief to the contrary, outboard motor operation could be a major source of petroleum products released into the world's oceans, with effects focused on our own coastal waters.
As reported by Yousef (1974), in water depths of 15 feet the operation
of a 50 horsepower outboard would re suspend bottom sediments in a lake
in Florida. Isolating turbidity attributable to boating activity - and
its impacts - from that occurring normally or resulting from other anthropogenic
activities would be difficult. However, it seems obvious that in shallow
water bodies exposed to high natural inputs of silt, boating activity could
play a large part in re suspending sediments and, particularly with the
finest fractions, keeping them in suspension. Along with the direct contribution
to increased turbidity, this could also contribute in-directly through
making nutrients more readily available to the phytoplankton (Yousef et
al, 1980). The role of boat traffic in increasing turbidity - and decreasing
the survival of bottom vegetation - has received a great deal of attention
in the United Kingdom (Garrad and Hay, 1987, Liddle, 1980 and others).
There are a several other potential negative impacts resulting from boating activities - propeller bottom scouring, leaching of toxics from bottom paints, spills during fueling operations, waste releases, etc. - that are at this point being considered and evaluated by the research community and aren't covered here.
The potential impacts that have been surveyed, however, have been ignored for the past twenty years. They are - or should be - of particular concern because any of them could be playing a significant role in the decline of one or several species that are or have been important to the inshore recreational and commercial fisheries in the Mid-Atlantic region.
The bay anchovy (Anchoa mitchilli), one of the primary forage fish in these waters, is an estuarine spawner from April to September that lays neutral density eggs. After hatching, the larvae migrate to the lower salinity, shallower and near-surface waters where they remain until winter approaches (Grosslem and Azarovit, 1986, Vougliotois et al, 1987). Declines in the abundance of bay anchovies is part of the impetus (declining weakfish stocks is the other) to force the construction of cooling towers at a nuclear power plant on the Delaware River. Bluefish (Pomatomus saltatrix) support an important commercial fishery and the largest segment of the recreational fishing industry in the Mid-Atlantic. Ocean spawners, the juvenile fish move into the estuaries in the spring and remain there until the waters begin to cool in the fall. Striped bass (Morone saxatalis) are important commercially and recreationally. Severe population declines attributed to lack of hatching success and/or larval survival in recent years have forced the almost complete closure of the fishery. Supposedly based on a single successful year-class, the striped bass fishery has been reopened but severely restricted for the past two years. Striped bass are estuarine spawners in the early spring, the juveniles moving into the ocean in the fall. Weakfish (Cynoscion regalis), summer flounder (Paralichthys dentatus), American oysters (Crassostrea virginica) and hard clams (Mercenaria mercenaria) as well are all dependent on the Mid-Atlantic estuaries for spawning, larval development and/or maturation during the peak of the recreational boating season and all are experiencing serious stock declines.
These species would all be in a position to suffer most acutely any negative effects of boat opera-tion. They are in the estuaries during the peak boating period; they are there in forms - eggs, larvae or juveniles - least able to avoid or withstand physical or chemical challenges; they are generally found in the upper water levels that would receive the greatest impact of boating activity, possibly in prolonged contact with toxic substances concentrated in water surface microlayers or on constantly re suspended solids; and they are often being stressed by low oxygen levels and/or high water temperatures.
Considering the importance of maintaining the health of our inshore waters, the intesive and increasing use of these waters by recreational boaters, the increasing demands placed upon them by competing user groups, and the growing public attention directed towards the misuse - perceived or actual - of any public resource, further examination of these areas that I have briefly touched on is definitely warranted. Solely on the basis of the volume of water that they directly and violently disturb, it would seem that boating activities should receive a partial share of the scrutiny that other coastal activities must endure, at least until reasonable estimates concerning what - if any - impacts they are responsible for can be made.
In New Jersey alone the unburned residues, combustion products and generated heat from 30 million gallons of fuel are injected into our highly productive estuarine waters each year, generally at a time that is most critical to the delicate eggs, larvae and juvenile life stages of many of our important species. The impacts - if any - of this demand investigation as well.
Penalties and restrictions levied against other users of our estuarine
resources for the supposed impacts of their operations on our fishery resources
amount to billions of dollars each year. If these penalties and restrictions
are misdirected and ineffective (and the continuing declines in many of
our fisheries seem to be arguing strongly that they might be), then increasing
them will be of no benefit. At the same time, continuing to ignore the
effects of recreational boating - probably cumulative and possibly
devastating - and allowing its continuing unfettered growth could be exacerbating
a situation which could already be far beyond critical.
(This survey was conducted with the support of Public Service Electric and Gas Company, Inc. and the New Jersey Commercial Fishermen's Association.)