Environmental variables driving horseshoe crab spawning behavior in a microtidal lagoon in Florida

Area of Science:

• Marine Biology
• Estuarine Ecology
• Crustacean Research

Background:

• American horseshoe crabs (Limulus polyphemus) typically spawn during high tides linked to lunar cycles.
• Florida's Indian River Lagoon is a microtidal estuary where tidal cues for spawning may be less pronounced.
• Environmental factors influencing horseshoe crab spawning in microtidal systems require further investigation.

Purpose of the Study:

• To identify key environmental factors affecting American horseshoe crab (Limulus polyphemus) spawning in the microtidal Indian River Lagoon.
• To investigate the relationship between spawning activity and environmental variables like wind, temperature, and salinity.
• To understand horseshoe crab (Limulus polyphemus) reproductive behavior in estuarine systems with limited tidal influence.

Main Methods:

• Utilized daily surveys conducted by volunteers from Florida Horseshoe Crab Watch during peak spawning months (February-April 2019).
• Collected data on the number of spawning horseshoe crabs (Limulus polyphemus) and environmental parameters (tide height, water/air temperature, wind speed/direction, salinity).
• Applied negative-binomial regression models to analyze the correlation between horseshoe crab (Limulus polyphemus) abundance and environmental factors.

Main Results:

• A significant positive correlation was found between onshore wind speed and the number of spawning horseshoe crabs (Limulus polyphemus).
• Tidal height showed a weaker influence on spawning activity compared to wind speed in this microtidal environment.
• Other environmental variables like water temperature and salinity did not show a strong direct relationship with spawning numbers.

Conclusions:

• Onshore wind speed appears to be a critical environmental driver for American horseshoe crab (Limulus polyphemus) spawning in microtidal estuaries like the Indian River Lagoon.
• The absence of strong tidal cues necessitates a reevaluation of spawning triggers for horseshoe crabs (Limulus polyphemus) in such systems.
• Findings highlight the importance of wind patterns in estuarine ecosystems for the reproductive success of horseshoe crabs (Limulus polyphemus).