Ecological Impacts of Zebra Mussels in the Hudson River

Introduction

• Challenges in understanding ecological impacts of invaders.
• First sign of invasion is often the changes caused by the invader, making it difficult to assess pre-invasion conditions.
• Unique opportunity due to years of pre-invasion data available on the Hudson River.

Background on Zebra Mussels

• Zebra mussels are small, striped bivalves (like clams and oysters).
• Easily transported by humans due to microscopic larvae in the water column.
• Known presence in the Great Lakes, which are connected to the Hudson River.
• Anticipation of their arrival in the Hudson river slowly.

Monitoring the Hudson River

• Long-term monitoring station located at Kingston.
• Regular measurements include:
  • Temperature
  • Dissolved oxygen
  • Light penetration
• Water samples are collected for laboratory analysis.

Physical Parameters Observed

• Temperature: 9.7°C
• Oxygen: 104.7% saturation
• Light penetration measured at only 20 cm due to turbidity.
• Important for the growth of phytoplankton, as they need sunlight.

Impact of Zebra Mussels

• First observed in 1991; significant population increase by 1992 (500 individuals).
• Filter feeders that primarily consume small algae and tiny zooplankton.
• Significant changes observed post-invasion:
  • 80% loss of phytoplankton populations.
  • 90% reduction in smaller zooplankton.
  • Overall zooplankton biomass decreased by 50%.
• Resulted in diminished fish food supply, affecting the entire fish community.

Public Reaction and Long-term Effects

• Community concerns due to declining fish populations.
• Short-term acute impacts documented, including water chemistry changes.

Observing Changes Over Time

• Ongoing monitoring has shown increasing numbers of smaller zebra mussels each year.
• Lifespan of zebra mussels has decreased from 6-8 years to 1-2 years.
• Possible reasons for decreased lifespan:
  • Diseases
  • Predators
  • Overconsumption of food resources.
• Larger zebra mussels can consume zooplankton, indicating a potential recovery of zooplankton populations.

Conclusion

• River ecosystems are dynamic, with some changes being natural and others linked to invasive species.
• Importance of continuous observation to understand and identify the causes of changes in the river ecosystem.
• Current conditions in the Hudson differ significantly from those in the 1990s, prompting new research questions.