Anthropogenic Influences of Oyster Degradation in the Lower Hudson River

1
Anthropogenic Influences of Oyster Degradation in
the Lower Hudson River

• Patricia Chin-Sweeney
• Advisor Stephanie Pfirman, Barnard Environmental
  Science Department
• Mentor Robin Bell, LDEO

2
History of the New York Oystering Industry

• Oysters in the Hudson date back to
  pre-colonialism.
• 350 sq miles of oyster beds once ran from the
  Harbor area to Croton Point.
• NYC was the center of the oystering industry for
  the Northeast during the mid- to late-1800s.
• Sites of historic oyster beds
• Staten Island, Gowanus Bay, Gravesend Bay,
  Jamaica Bay, East River, Kill Van Kull, Arthur
  Kill, Newark Bay, Raritan Bay, Shrewsbury River.

3
The Eastern Oyster, Crassostrea viginica

• Habitat Requirements
• Dissolved Oxygen Concentration gt3 ppm required
  for survival.
• Hard, clean substrate to which spat can attach.
• Salinity 10-30 ppm 15-18 optimal- at which
  spawning will occur.
• Why Should We Care About These Oysters?
• Filter feeders- remove contaminants/ suspended
  matter? cleaner, clearer water.
• Indicators of ecosystem health
• Reefs act as shelter to many marine species?
  diversity.
• Native to NY and the Hudson River.

4
Primary Factors of Influence

• Sedimentation
• Dissolved Oxygen Content
• Overharvesting
• Other Factors
• Salinity changes
• Disease (Dermo, MSX)
• Other Contaminants (PCBs, mercury)

5
The Role of Human Activity

• Increased Siltation/Sedimentation
• Development/Construction
• Anoxia/Hypoxia
• Run-off (agricultural city sewage)
• High coliform levels
• Decreased Salinity
• Excess fresh water inflow
• Overharvesting
• Without returning shells
• ? Severe Habitat Degradation

6
Another Factor to Consider
7
Siltation/Sedimentation

• Causes
• Deforestation
• Development, esp. along the waterfront
• Agricultural practices
• Dredging
• Effects
• Suffocation
• No proper substrate for setting? reduced
  recruitment.
• Decreased filtering efficiency slower growth
• Reduced sun exposure? less food supply

8
Anoxia/Hypoxia

• Causes
• Untreated sewage garbage dumped directly into
  the Hudson.
• High Fecal Coliform levels
• Effects
• Suffocation
• Reduced food supply
• Increased intake of pollutants
• By the 1920s, DOC levels in much of the harbor
  dropped to critical levels (0-20 Saturation in
  summer).

NYCDEP Harbor Survey
9
Overharvesting

• Cause of the more recent almost complete
  disappearance
• Exploitation
• Poor harvesting practices
• Dredging of oyster beds
• No shells for cultch

Top Leased oyster beds off Princes Bay and Ward
Point, Staten Island (1917). Bottom Same area
in 1937 after industry was shut down.
10
Summary

• Primary factors that caused the present oyster
  population conditions
• Population Growth
• Development/Agriculture
• Untreated Waste/ Poor Sanitation
• Overharvesting
• Sedimentation/Siltation
• Anoxia?Eutrophication