WES WEEK EIGHT: 29 October-2 November 2001

• Coral reefs can develop in nutrient-poor waters -- German scientists using sophisticated cameras have been able to probe coral reefs in the Red Sea in an attempt to understand how marine organisms appear to survive in a reef that is located in nutrient-poor ocean waters. [Scientific American]
• Earth diary - A summary of the week's major environmental events on Planet Earth. [CNN]

Concept of the Week: Chesapeake Bay Ecosystem

Chesapeake Bay is North America's largest estuarine ecosystem; it is more than 300 km (185 mi) long, 65 km (40 mi) at its broadest, and averages about 20 m (66 ft) deep. The estuary was formed by the post-glacial rise in sea level that flooded the valley of the ancient Susquehanna River. The Bay receives about half its water from the Atlantic Ocean and the other half from the more than 150 rivers and streams draining a 166,000 square-kilometer land area encompassing parts of New York, Pennsylvania, West Virginia, Delaware, Maryland, Virginia, and the District of Columbia. Rivers emptying into Chesapeake Bay include the Potomac, Susquehanna, York, and James.

An estuary is a complex and highly productive ecosystem formed where seawater and fresh runoff meet. In Chesapeake Bay, more-dense seawater creeps northward along the bottom of the estuary, under the less-dense fresh water flowing in the opposite direction. This circulation combined with wind-driven motions causes salinity to decrease upstream in the Bay, from values typical of seawater at its mouth to freshwater values at its northern margin.

As in all ecosystems, organisms living in estuaries depend on one another and their physical environment for food energy and habitat. This interdependency is evident in food webs, complex pathways along which energy flows and materials cycle. Phytoplankton and submerged aquatic vegetation (e.g., marsh grass) are the primary producers in estuarine food webs. (Producers acquire energy from solar radiation through photosynthesis and are at the bottom of grazing food chains.) Consumers in food webs are organisms that derive their energy by eating producers or other consumers. Chesapeake Bay consumers include zooplankton, finfish, shellfish, birds, and humans. Through cellular respiration, producers and consumers convert energy to a form that the organism can use for growth and reproduction.

Human activity has greatly modified Chesapeake Bay with consequences for the functioning of its ecosystem. Much of the original forest that covered its drainage basin was converted to farmland, roads, cities, and suburban developments. These modifications accelerated the influx of nutrients (i.e., compounds of phosphorous and nitrogen), sediment, pesticides, and other pollutants. More nutrients spur growth of algal populations and when these organisms die (in mid-summer) decomposition of their remains reduces dissolved oxygen levels in the Chesapeake's bottom water. More sediment makes the water cloudy, reducing sunlight penetration for photosynthesis.

One casualty of human modification of the Chesapeake Bay ecosystem was marsh grass--reduced by 90% from historical levels. Marsh grass anchors sediment and dampens wave action thereby controlling erosion and turbidity. Marsh grass is a food source for many organisms including waterfowl and small mammals and serves as a primary nursery ground for crabs and many species of fish. Reduction of this habitat along with over-fishing has been implicated in the decline of populations of blue crabs, a mainstay of the Bay fishery for more than a century. Over the past decade, the number of adult female crabs has plunged by 80%. Without adequate protection by marsh grass the blue crab is more vulnerable to predation by striped bass (i.e., rockfish). Striped bass turned to blue crabs as a food source when fishing reduced the numbers of menhaden, their preferred food. Menhaden is a marine fish in the herring family and the Bay's top fishery by weight.

Concept of the Week: Questions

1. Within the waters of Chesapeake Bay, salinity [(is relatively uniform)(varies greatly)].
2. Marsh grass is a [(producer)(consumer)] in the Chesapeake Bay ecosystem.

• 29 October 1999...Tropical Cyclone 5B, with sustained winds of 155 mph, made landfall at Paradwip (Orissa, India). A storm surge of at least 20 feet height swept at least 12 miles inland. More than 10,000 killed. With 2 million homes either damaged or destroyed, 35 million people were left homeless. Damage from this tropical cyclone was 1.5 billion dollars. (Accord Weather Calendar)
• 30 October-1 November 1991...After absorbing Hurricane Grace on the 29th, an intense ocean storm took an unusual course and moved westward along 40 north latitude and battered eastern New England with high winds and tides. Winds had already been gusting over 50 mph along the coast 2 days before, so seas and tides were very high. Major coastal flooding and beach erosion occurred all along the New England, New York and New Jersey coastlines. Over 1000 homes were damaged or destroyed with tides 4 to 7 feet above normal. Wind gusts reached 78 mph at Chatham, MA and 74 at Gloucester, MA . One ship east of New England reported a 63 foot wave. Total damage from the storm was $200 million. One ship east of New England reported a 63 foot wave. Total damage from the storm was $200 million. On the 1 November this ocean storm underwent a remarkable transformation. Convection developed and rapidly wound around the storm center and an eye became visible on satellite imagery. Air Force reconnaissance aircraft found a small but intense circulation with maximum winds of 75 mph. This evolution from a large extratropical low to a small hurricane is rare but not unprecedented. (Intellicast)
• 31 October 1846...Eighty-seven pioneers were trapped by early snows in the Sierra Nevada Mountains that piled five feet deep, with 30 to 40 foot drifts. Just 47 persons survived the "Donner Pass Tragedy". (The Weather Channel)
• 31 October 1874...A waterspout (a tornado-like vortex that travels over water) formed over Lake Erie and reached the lakeshore approximately 0.5 miles west of Buffalo, MY. Upon reaching the shore, it dissipated, scattering sand in all directions. (Accord Weather Calendar)
• 31 October 1965...Fort Lauderdale, FL was deluged with 13.81 inches of rain inches over a two day period (30th-31st), the second heavy rains in two weeks and brought their rainfall total for the month of October to an all-time record of 42.43 inches. More road and street damage occurred and some homes were flooded for the second time. (David Ludlum) (The Weather Channel) (Intellicast)
• 31 October 1984...An exceptional thunderstorm at Al Wajh on the Red Sea coast of northern Saudi Arabia produced 4.81 inches of rain, which was more than the total rainfall there in the previous ten years. At Tabuk 150 miles to the north, 0.49 inches of rain fell to set a daily October rainfall record at that location. (Accord Weather Calendar)
• 1 November 1861...A hurricane near Cape Hatteras, NC battered a Union fleet of ships attacking Carolina ports, and produced high tides and high winds in New York State and New England. (David Ludlum)
• 2 November 1946...A heavy wet snow began to cover the Southern Rockies. Up to three feet of snow blanketed the mountains of New Mexico, and a three day snowstorm began at Denver, CO. By the time it ended, this storm had dropped 31 inches, making it the second greatest snowfall ever in city history and causing roofs to collapse. (David Ludlum)
• 2-4 November 1927...The 'Great Vermont Flood' occurred as a two day rain of up to 15 inches at the higher elevations put rivers in western New England over their banks and causing the worst flood in the history of Vermont. Somerset, VT was deluged with 8.77 inches of rain to establish a 24 hour record for the state. (3rd-4th) The Winooski Valley was devastated. Eighty four died in Vermont's town of Vernon. Flooding left up to eight to ten feet of water in downtown Montpelier. Across New England the flooding claimed 200 lives in all of New England, caused 40 million dollars damage and halted traffic for days. (The Weather Channel) (Intellicast) (David Ludlum)
• 4 November 1989...Typhoon Gay, reportedly Thailand's worst storm in 50 years, struck the southern peninsula of Thailand with sustained surface winds of 105 mph. More than 645 sailors and fishermen may have drowned as 200 ships capsized. On land, 489 deaths were confirmed. (Accord Weather Calendar)

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Prepared by AMS WES Central Staff and Edward J. Hopkins, Ph.D., email hopkins@meteor.wisc.edu
© Copyright, 2001, The American Meteorological Society.