John P. Jacobson and C. S. Fang
During the Agnes flood hourly tidal height data were collected at seven locations along the tidal James River and currents were measured at two transects in the lower James. A comparison between actual tides and currents and the predicted tidal features as given by the tide and tidal current tables of NOAA was made. Results of this comparison show that Agnes did significantly affect water levels in the upper portion of the tidal James, especially near Richmond. However in the lower portion of the James no discernible rise was evident due to the passage of the flood crest. A small storm surge (<2>feet) was noted on the day of the passage of Agnes, 21 June, throughout the tidal James. A phase shift in times of high and low water due to the interaction of the two wave systems was not observed. In the freshwater portion of the tidal James currents continually ebbed during the passage of the flood crest. In the saline portion of the system, the flood effect on the currents was limited to the surface portion of the channel.
Observations On Dissolved Oxygen Conditions In Three Virginia Estuaries After Tropical Storm Agnes (Summer 1972)
Dissolved oxygen (DO) and salinity levels in the James, York, and Rappahannock estuaries were monitored for approximately two months (June 24-August 31, 1972) following Tropical Storm Agnes. DO depressions developed more rapidly and were more severe in the deep waters of the York and Rappahannock than in the James. Depressions that developed immediately after the storm were followed by recoveries and subsequent, more severe depressions. In late July, bottom water DO concentrations below 1 mg/1 were found at stations covering 15 miles of the York and 25 miles of the Rappahannock. Comparison of river data with Chesapeake Bay data suggests that the rivers contributed oxygen poor water to the Bay during the post-Agnes period. Comparison of 1972 river data with data from other years suggests that the post-Agnes oxygen depressions were more severe than those that occur in normal years.
Patterns of Distribution of Estuarine Organisms and their Response to a Catastrophic Decrease in Salinity
Peter F. Larsen
The occurrence of Tropical Storm Agnes during an ongoing study on the community structure of the macrobenthos associated with the James River oyster reefs provided a unique opportunity to document the responses of this assemblage to such a disturbance. The spatial and temporal patterns of abundance of 18 important taxa are examined in this paper. Eight species exhibited limited up estuary penetration, six were most successful in the upper part of the estuarine segment studied, two were most abundant in the mid-section of the study area, and two were ubiquitous. In the post-Agnes period, .six species exhibited reduced population levels, three experienced population increases, three became relatively more abundant at the down estuary sites and reduced at the up estuary sites, three became relatively more abundant at the up estuary sites and reduced at the down estuary sites, while no significant response was shown by three others. Hypothetical response categories are advanced to explain these responses. The freshet arrived and removed stenotopic species (category 1 response) which allowed others to fill the void in abundance (category 2 response). Other species essentially extended their range downstream where conditions were not optimal but were reduced in their original range because of the physiological stress caused by very .Low salinities (category 3 response). With the return of higher salinities the larvae of more stenohaline species settled where there was open space, i.e., at the up estuary sites (category 4 response). Some species showed no significant changes in abundance (category 5 response).
Public health aspects of Tropical Storm Agnes in Virginia's portion of Chesapeake Bay and its Tributaries
M. P. Lynch and J. Claiborne Jones
All Virginia waters within Chesapeake Bay were closed for the taking of shellfish for direct consumption on 23 June 1972. This initial closing was in anticipation of high microorganism levels accompanying flood waters moving downstream. Various areas beginning with the lower portion of Chesapeake Bay were reopened beginning )n 20 July 1972. By 5 October 1972 all areas closed as a result )f Tropical Storm Agnes were reopened. No increased incidents of infectious diseases caused by waterborne microorganisms were noted in Virginia which could be attributed to Tropical Storm Agnes.
Maynard M. Nichols, Galen Thompson, and Bruce Nelson
Flooding from Tropical Stonn Agnes produced unique hydrographic conditions for transport and dispersal of sediment in the Rappahannock and .James estuaries. Analyses indicate two cycles of response and recovery to the shock of extreme freshwater and sediment influx; one cycle in response to Rappahannock inflow; the other to intense mixing within the estuary. Important stages in the sequence consist of: (1) an initial response and seaward surge of river water and sediment; (2) shock with downstream translation of the salt intrusion head with a near-bottom salinity front and high turbidity in surface and in bottom water; (3) rebound with intense stratification and formation of an enriched turbidity maximum; (4) partial recovery with salinity intrusion strengthened by upstream flow along the bottom; landward migration of the maximum; (5) full recovery and return to partly-mixed state with decay of turbidity maximum over a broad zone 30 days after flooding. Sediment was derived initially from lateral tributaries and then from the main river. The bulk of the load sedimented above the salt intrusion during the first three days of flooding. Sediment dispersed into the estuarine circulation system later was effectively trapped by upstream flow along the bottom. Over the entire event, 91% of the sediment load was trapped.
The displacement and loss of larval fishes from the Rappahannock and James rivers, Virginia, following a major tropical storm
Walter J. Hoagman and John V. Merriner
Two days after Tropical Storm Agnes, the Virginia Institute of Marine Science (VIMS) established an anchor station at Mile 15 in the Rappahannock and Mile 10 in the James River. Both stations were in mainstream, manned constantly for 10 days, and took continuous current data from meters placed at 0, 6, 8, and 15 min the Rappahannock and 0, 4, 5, 8, and 14 min the James. Concurrently, 0.85 m diameter plankton nets of No. 1 nylon mesh were hung in the flowing surface water for 10 minutes hourly. A small collection of midwater (4 m) plankton samples was obtained from the James station. The shoal areas were not sampled for larval fish. The ichthyoplankton and zooplankton captured were preserved and later identified to species.
The Effect of Tropical Storm Agnes as Reflected in Chlorophyll A and Heterotrophic Potential of the Lower Chesapeake Bay
Paul L. Zubkoff and J. Ernest Warriner III
A hydrographic station (Station Y) at the mouth of the York River (37°14.6'N, 76°23.4'W) was under biological surveillance for one year prior to the arrival of Tropical Storm Agnes. For one full year following this storm, these measurements were continued. In addition, the chlorophyll a and heterotrophic potential measurements were incorporated into an ongoing zooplankton sampling program of the lower Chesapeake Bay below 37°40'N latitude.
The Effect Of Tropical Storm Agnes On Heavy Metal And Pesticide Residues In The Eastern Oyster From Southern Chesapeake Bay
M. E. Bender and R. J. Huggett
The concentrations of cadmium, copper, and zinc in the eastern oyster, Crassostrea virginica, are compared for samples collected before and after Tropical Storm Agnes. The "before" samples consisted of 475 animals from 95 stations collected in January 1971 and the "after" samples of 285 animals from 57 stations collected in January 1973. Shifts in the areal concentrations distributions were observed, apparently due to Agnes. Analyses of hard clams, blue crabs and oysters for chlorinated hydrocarbon pesticides showed influx of these compounds to be minimal as reflected by the residue levels observed. Comparison of residue levels in oysters to pre-Agnes conditions revealed a decrease in pesticide body burden.
The Effect of Tropical Storm Agnes on Oysters, Hard Clams, Soft Clams, and Oyster Drills in VIrginia
D. S. Haven, W. J. Hargis Jr., J. G. Loesch, and J. P. Whitcomb
Tropical Storm Agnes had a major effect on the molluscan fisheries of Virginia. One effect was the direct mortality of oysters, Crassostrea virginiaa, in the upper parts of many estuaries. Typical losses on leased bottoms were: the James River, 10%; the York River, 2%; the Rappahannock River, 50%; and the Potomac River tributaries (Virginia) 70%. Economic loss was in excess of 7.9 million dollars. There was a nearly complete absence of oyster larvae attachment (setting) in 1972. Other effects of Agnes included a nearly complete loss of soft clams, Mya arenaria, in the Rappahannock River. Hard clams, Meraenaria meraenaria, were killed in the upper part of the York River. Oyster drills, Urosalpinx ainerea, were eliminated from the Rappahannock and reduced greatly in numbers in the York and James Rivers.
The effect of Tropical Storm Agnes on the benthic fauna of eelgrass, Zostera marina, in the lower Chesapeake Bay
Robert J. Orth
Tropical Storm Agnes caused major changes in the macroinvertebrate assemblages of both epifauna and infauna in eelgrass, Zostera marina, beds. Species abundance and density of infauna declined by one-third to one-half of values found prior to Agnes. Typical members of the infaunal community such as the amphipods, Ampelisca spp. and Lysianassa alba, the polychaetes Sabella microphthalma and Exogone dispar, ostracods and gastropods were either absent or rare following Agnes. Epifaunal density was much higher than that recorded before Agnes but the number of species was reduced. This high density was attributed to several species, e.g. Molgula manhattensis, which appeared to occupy space left open by the absence of typical members of this community, e.g. Paracereceis caudata and Bittium varium. The abnormally low salinities following Agnes affected various species in different ways. Some species were totally eliminated, severely reduced in abundance or, in a few euryhaline species, not affected at all. In some populations it appeared that adults survived but juveniles suffered high mortalities. Recovery and reestablishment by many species will be complicated by the disappearance of eelgrass in some portions of the Bay.
The effects of the Agnes flood on the salinity structure of the lower Chesapeake Bay and contiguous waters
A. Y. Kuo, E. P. Ruzecki, and C. S. Fang
The transient response of salinity distribution in lower Chesapeake Bay to flood waters from Tropical Storm Agnes is studied in terms of a two-layered, partially mixed estuary. Prior to 30 June 1972, surface salinities were well depressed throughout the Bay while those at the bottom near the Bay mouth were not depressed by 5 July. This resulted in a highly stratified situation normally found in the spring of the year. Stratification decreased when bottom waters were flushed down-bay by the flood (on 5 to 10 July for the region south of New Point Comfort). The "rebound" of salinity structure started immediately after the passage of the flood water which otherwise retarded up-bay movement of bottom waters. This "rebound" began on 13 July near the Bay mouth and progressed up-bay reaching the mouth of the Potomac River by 20 July. During this period, surface salinity remained low, resulting in strong stratification again. The recovery of surface salinity by tidal mixing finally weakened stratification to a near "normal" salinity structure by the end of August. The large mass of flood water leaving the Bay mouth is treated as a natural tracer release. The distribution of flood water on the continental shelf indicates that pulses of freshened surface water left the Bay on ebb tide and were separated from one another by intrusion of saltier shelf water on flood tide. During the period when the wind speed was below 4 m/s, the flood water remained in the upper 10 meters of the water column and traveled southward with a speed of 80 cm/sec.
The Effects of Tropical Storm Agnes on Fishes in the James, York, and Rappahannock Rivers of Virginia
Walter J. Hoagman and Woodrow L. Wilson
Intensive trawl surveys during and after Tropical Storm Agnes were mounted on the James, York, and Rappahannock Rivers to measure the effects of the floodwaters on the distribution and abundance of fish. The direct effect of Agnes on the fish populations was minor and temporary. The normal zone was extended downriver. A substantial portion of the lower-river (marine) species was also displaced downstream and into Chesapeake Bay, but had returned by the follow-up surveys. No adult mortalities due to Agnes were detected. Although we know vast quantities of fish larvae and other plankton were swept into Chesapeake Bay, the overall impact on all fish appears to have been slight.
Robert J. Huggett and Michael E. Bender
The metals copper and zinc were analyzed in bottom sediments (top 1 cm) from the Rappahannock River before and after Tropical Storm Agnes. By extracting the sediments with various techniques (HN03, HCl) the nature of the metal speciation can be estimated. Data show that the inorganic copper was increased by a factor of 2 to 3 in the normally saline portion of the river as a result of Agnes but returned to before-Agnes levels within one year. Metal analyses of suspended sediments collected during the Agnes flooding allows an estimate of sedimentation indicating at least 7.5 mm of new sediments at mile 40, decreasing nearly linearly to 1 mm at mile 15.
Morris L. Brehmer
I have modified the scope of this paper slightly to include urban pollution because the pollution problems produced by the agricultural industry are essentially the same as those produced by municipalities. We know that environmental degradation occurs as a result of the discharge and the byproducts from both sources.
In the case of agricultural activities, the terrain has and still is being modified to convert it to crop production. In the livestock industry, large populations of animals are being concentrated into relatively small areas to meet the economic pressures of meat production. With the human population, the numbers of people are not only increasing but are also concentrating. Probably more important, countless square miles of terrain have been denuded and modified to make way for highway and street construction or for the development of housing units. From both sources the results are the same. We have increased siltation; we have increased organic loading; and we have increased nutrient loading
Dexter S. Haven and Reinaldo Morales-Alamo
Filter feeders, such as mollusks, tunicates, and barnacles, ingest particles as small as 1 micron during their feeding process and void them in fecal pellets which range from 500 to 3,000 microns in length; these pellets settle at a much faster rate than their component particles. Feces and pseudofeces that settle to the bottom are termed biodeposits. Oyster biodeposits contain 77 to 91 percent inorganic matter, 4 to 12 percent organic carbon, and about 1.0 gram per kilogram of phosphorus. Fecal pellets are alternately deposited and resuspended by tidal currents. They settle and accumulate in areas of estuaries where the fine particles themselves would not. A portion of the biodeposits settling on sediment surfaces is mixed into subsurface deposits and may alter the textural and chemical properties of the original sediments.
Maynard M. Nichols
The effects of channel deepening on the salinity and density flow in the James River estuary, Virginia, were studied to predict changes that might affect oyster production. A hydraulic model with 1: 1,000 horizontal and l: 100 vertical scales was employed to integrate three-dimensional changes in salinity and velocity through reaches of variable bottom geometry. After natural characteristics of the tide, current, and salinity were reproduced in the model, tests were run at three levels of steady river inflow, before and after a 3-meter channel deepening. Results were combined with corollary field observations to evaluate changes in present-day ecological conditions.
Deepening produced the greatest salinity change in the middle estuary where the major cut was performed. The lower water layer located mainly in the channel became saltier by about 0.5 part per thousand, whereas the upper layer over the oyster shoals became fresher by about 0.2 part per thousand. Changes in bottom water salinity were greatest at intermediate inflow and least at very low inflow. High fresh-water inflow created the greatest change in vertical salinity gradient. With greater stratification, tidal velocities were less effective in promoting vertical mixing between lower and upper estuarine water layers, and the net volume transport in each layer was reduced.
Since the changes in salinity and flow pattern due to channel deepening were small, no effects inimical to the oyster fishery were predicted. Similarly the prospective changes in sedimentary regime will not offset the beneficial effects of the proposed deepening project.
William J. Hargis Jr.
This paper discusses the tidal tributaries of the ocean and the coastal areas of the mid-Atlantic Bight and the ecological significance of engineering projects. While occasional reference may be made in this paper to remote sensing of problems engendered by engineering works on maritime environments and resources, principal efforts along those Jines are reserved for the group discussion to follow.
The Chesapeake Bay drainage basin_encompasses.almost 65,000 miles and provides space and partial resources for over 11 million people ( 1960) in New York, Pennsylvania, Maryland, Virginia, and the District of Columbia. Two other states, Delaware and West Virginia, to a lesser extent are part of this basin. Major residential, industrial and commercial, military, and recreational activities in the mid-Atlantic area make their demands on the environment and resources and contribute to the economic and social well-being of the populace. Certain social and economic disbenefits often accompany these activities. Population growth in the basin is increasing as are economic and social activities and other user activities.
Reference 1 includes many of the vital statistics on the Chesapeake Bay drainage basin. Numerous other studies in all fields have reported upon many natural, economic and social features of the Bay. Still others on these and additional subjects are in process.
Maynard M. Nichols
The James River estuary of the Chesapeake Bay region follows the course of a former river valley drowned within the last 9,000 years by the most recent rise of sea level. The floor is shaped into a central channel bordered by submerged shoals. Observations show suspended sediment is transported mainly by alternating tidal currents and secondarily by the net nontidal estuarine circulation. Transport results in a sequence of grain size distributions reflecting the mixing of two textural end members, clay and sand.
Silty clay is deposited in the river and upper estuary, whereas sand occurs near the mouth. Transitional types, clayey sand and sand-silt-clay, predominate in the middle estuary. Additionally, biogenic materials, oyster shells and fecal pellets, and small amounts of residual components eroded from older deposits are mixed into the sediments by currents, waves, and organisms. Bottom sediment types vary widely according to local relief, to varying intensity of environmental processes, and to changing rates of supply from different sources:
Deposition is greatest in the middle estuary where salinity ranges from 5 to 14 parts per thousand. An elongate zone of relatively high deposition in the lower estuary corresponds to the intersection of the level of no-net-motion with the bottom. Despite substantial infilling, it is believed the estuary is maintained by the continued rise of sea level and by currents that flush part of the river-borne load through the estuary.
Age Composition and Magnitude of Striped Bass Winter Gill-net Catches in the Rappahannock River,1967-1970
George C. Grant, Victor G. Burrell Jr., and William H. Kriete
The dependence of commercial fishing success on strong yearclasses of striped bass is demonstrated, using four years of catch records from a small group of cooperating gill-net fishermen. Age analysis of these Rappahannock River catches during 1969 and 1970 revealed that an approximate tripling of landings in 1970 was a result of selection for the dominant 1966 year-class.
J. E. Warriner, J. P. Miller, and J. Davis
This report concerns the distribution of juvenile alewife (Alosa pseudoharengus) and blueback herring (Alosa aestivalis) in the tidal portion of the Potomac River as determined in 1968. The river courses for 100 nautical miles from the Lower Falls at Washington, D. C. to empty into the Chesapeake Bay some 60 miles from the Virginia capes. It is second only to the Susquehanna River in freshwater input to the bay, contributing 18% of the total. The salinity at the mouth is approximately 18 ppt., and salt water intrudes 70 to 75 miles. The upper tidal portion is heavily polluted by domestic wastes from the Washington Metropolitan area. Although much of the sewage is treated, over enrichment causes massive algal blooms.
George G. Grant, Victor G. Burrell Jr., C. E. Richards, and Edwin B. Joseph
A total of 8525 striped bass, Morone saxatilis (Walbaum), were tagged and released in Virginia during 1968 and 1969. Releases were grouped in three periods: (1) 3195 in winter 1968, (2) 2439 during summer-fall 1968; and (3) 2891 in winter 1969. Streamer disc tags, employed in winter 1968, were subsequently replaced by internal anchor tags (Floy Tag No. FD-67). This substitution shortened application time and eliminated a source of bias introduced by the entanglement of disc tags in gill nets. Releases were made in the James, York, and Rappahannock rivers in all three periods. Rewards of one dollar have been paid for return of tags. Percentages of returns within tagged year-classes increased with age, indicating change in fishing mortality rates of striped bass during their initial 3 to 4-year residence in the lower Chesapeake Bay system.
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