Tranzition Zone Chlorophyll Front

 Food Items available to loggerhead turtles:

Loggerhead turtles (Caretta caretta) living near Baja California, particularly the sub-adult and adult individuals, primarily feed on a wide variety of benthic (bottom-dwelling) invertebrates. Their powerful jaws are well-adapted for crushing hard-shelled prey.

Here's a breakdown of their typical diet in this region:

• Crabs: This is a major component of their diet. They consume various species of crabs found on the seafloor.
• Clams and Bivalves: Loggerheads are known to dig for and crush clams and other bivalves.
• Snails and Gastropods: Different types of marine snails are also part of their diet.
• Sea Urchins: These spiny invertebrates are also prey for loggerheads.
• Conchs: Larger conchs and other large shelled mollusks are consumed.
• Other Invertebrates: They may also feed on other bottom-dwelling creatures like worms, sea cucumbers, and various crustaceans.
• Occasional Fish: While not their primary food source, they may opportunistically consume slow-moving or injured fish.
• Jellyfish and Siphonophores: Especially younger loggerheads in pelagic (open ocean) habitats might feed on these, but as they mature and move to coastal foraging grounds, their diet shifts to more benthic prey.

Importance of Baja California as a Foraging Ground:

The waters off Baja California, particularly the Pacific coast and parts of the Gulf of California, are critically important foraging grounds for loggerhead turtles, especially those originating from nesting beaches in Japan. These turtles undertake trans-Pacific migrations to reach these rich feeding areas. The abundance of suitable benthic prey makes this region a vital "hotspot" for their growth and development before they potentially return to their distant nesting sites.

Understanding their diet in this region is crucial for conservation efforts, as it helps identify critical habitats and potential threats related to prey availability or contaminationLoggerhead turtles in their pelagic (open ocean) phase, particularly in the North Central Pacific, have a distinctly different diet from their benthic (bottom-dwelling) counterparts in coastal areas. These are often juvenile turtles, sometimes referred to as being in their "lost years," as they spend an extended period in the open ocean before recruiting to coastal habitats.

Their diet in these pelagic waters primarily consists of floating, surface-dwelling organisms (neuston) and other items found within the upper water column. This includes a wide variety of prey, reflecting their opportunistic foraging behavior in this environment.

Here's a breakdown of what they feed on:

• Jelly-like Organisms (Gelatinous Zooplankton): This is a very significant part of their diet. This includes:
• Siphonophores: Such as the Portuguese man-of-war (Physalia physalis) and other colonial hydrozoans.

• Chondrophores: Like the by-the-wind sailor (Velella velella).

• Pyrosomes (Pyrosoma spp.): Colonial tunicates.

• True Jellyfish: Though less dominant than the other gelatinous forms, they will consume them.

• Pelagic Mollusks:

• Janthina spp. (Violet Sea Snails): These snails create a raft of bubbles to float on the surface.

Carinaria cithara (Heteropods): Transparent, carnivorous pelagic snails.

• Cavolinia spp. (Sea Butterflies/Pteropods): Small, winged snails.

• Squid: Though often associated with deeper waters, certain pelagic squid species can be part of their diet.

• Pelagic Crustaceans:

• Goose Barnacles (Lepas spp.): These barnacles attach to floating debris.

• Planes spp. (Grapsid crabs): Small, pelagic crabs often associated with floating Sargassum.

• Amphipods: Small, shrimp-like crustaceans.
• Pelagic Red Crabs (Pleuroncodes planipes): Especially off the coast of Baja California in upwelling regions, these can be a dominant food source for juvenile loggerheads.

• Other Floating Items:

  • Fish Eggs: Opportunistically consumed.
    
    
  • Small, slow-moving or injured pelagic fish.

Key Foraging Areas:

Loggerheads in the North Pacific, particularly those from Japanese nesting beaches, undertake vast trans-Pacific migrations. They often concentrate their foraging efforts in productive areas like the North Pacific Transition Zone (NPTZ), which is a highly dynamic region where subtropical and subarctic waters mix. This zone is known as a "buffet line" due to its rich concentration of marine life, including the neustonic organisms that loggerheads feed on. They also forage along subtropical fronts, where sharp gradients in surface chlorophyll (indicating high productivity) occur.

The North Pacific Transition Zone Chlorophyll Front (TZCF) is a dynamic, basin-wide feature characterized by rapidly changing chlorophyll concentrations, temperature, and nutrients, marking a boundary between subtropical and subarctic phytoplankton communities, and influencing marine ecosystems and fisheries. 

Here's a more detailed explanation:

• What it is:

  The TZCF is a zone of surface convergence where cool, vertically mixed, high chlorophyll water on the north side sinks beneath warm, stratified, low chlorophyll water on the south side. 
• Location and Movement:

  It spans the east-west extent of the North Pacific and moves seasonally northward and southward within the North Pacific Transition Zone between 30°N and 45°N. 
• Seasonal Dynamics:

  • In the fall and winter, the TZCF moves southward, potentially due to strong winds moving nutrients across the boundary between gyres. 
  • In the spring, winds lessen and nutrient transport southward is reduced, causing the TZCF to move northward, reaching its most northerly position in the summer. 
• Importance:

  • The TZCF is an important ecological and economic demarcation in the Northern Pacific, associated with migrating predators like tuna, loggerhead turtles, and squid. 
  • Changes in its position can alter the spatial distribution of marine animals. 
  • The TZCF supports enhanced phytoplankton net community production. 
• Monitoring and Research:

  The front is easily monitored with ocean color satellite remote sensing. Ongoing research continues to advance our understanding of the physics and biology of the TZCF. 

• The transition zone chlorophyll front, a dynamic global feature ...

  It is a zone of surface convergence where cool, vertically mixed, high chlorophyll, surface water on the north side sinks beneath ...

  

  ScienceDirect.com
• North Pacific Transition Zone - Ocean Tracks

  Transition Zone Chlorophyll Front * The Transition Zone Chlorophyll Front (TZCF) is an area of rapidly changing chlorophyll conce...

  Ocean Tracks
• The Transition Zone Chlorophyll Front updated: Advances from a ...

  Subsequent research has provided considerable evidence that the TZCF is an indicator for a dynamic ocean feature with important ph...

  

  ScienceDirect.com
• Show all