Starfish, also known as sea stars, are marine invertebrates classified under the phylum Echinodermata. These fascinating creatures thrive in a range of marine environments, but their survival is heavily dependent on specific environmental conditions. Understanding these parameters provides valuable insights into their ecological roles and the health of the ecosystems they inhabit.

1. Temperature

• Optimal Range: Most starfish species thrive in water temperatures between 1°C and 30°C, depending on their geographic location and species type.
• Effect of Temperature: Warmer waters typically favor tropical species like the Crown-of-Thorns starfish, while polar species such as Labidiaster annulatus thrive in colder environments. Extreme temperatures can disrupt metabolic processes and affect reproductive success.

2. Salinity

• Typical Range: Starfish generally require salinity levels of 30–35 parts per thousand (ppt), similar to ocean water.
• Tolerance: While most species are sensitive to rapid salinity changes, some estuarine starfish can tolerate variations. Prolonged exposure to low salinity can cause stress or even mortality in less adaptable species.

3. Dissolved Oxygen

• Requirement: Starfish rely on dissolved oxygen for respiration through their papulae (skin gills).
• Adaptation: In areas with low oxygen levels, they may migrate or reduce activity to conserve energy. Hypoxic (oxygen-deprived) conditions, however, can severely impact their survival.

4. Habitat and Substrate

• Preferences: Starfish exhibit substrate-specific preferences:
  • Asterias rubens thrives on rocky surfaces.
  • Luidia clathrata prefers sandy or muddy sea bottoms.
• Ecological Role: The substrate type influences their diet and interaction with other organisms.

5. Light and Depth

• Depth Range: Starfish inhabit depths from shallow intertidal zones to the deep sea, with some species found over 6,000 meters below the surface.
• Light Sensitivity: Though they lack true eyes, light-sensitive cells on their arms help them navigate and select suitable habitats.

6. Ocean pH

• Optimal Levels: Slightly alkaline waters with a pH of 7.8–8.4 are ideal for starfish.
• Threat of Acidification: Ocean acidification, caused by increased CO2 absorption, can weaken their calcareous skeletons, posing a significant threat to their survival.

7. Food Availability

• Diet: Starfish feed on bivalves, corals, and decaying organic matter.
• Impact of Scarcity: A decline in prey populations due to overfishing or habitat destruction can reduce starfish populations. Conversely, overabundance of prey can lead to population booms, as seen with the Crown-of-Thorns starfish, which can harm coral reefs.

8. Predators and Competition

• Predators: Natural predators like crabs, fish, and seabirds help regulate starfish populations.
• Competition: Starfish often compete with other benthic organisms for space and resources, influencing their distribution.

Conservation Considerations

Starfish play crucial roles in marine ecosystems, including maintaining bivalve populations and nutrient recycling. However, climate change, ocean acidification, pollution, and habitat destruction threaten their habitats and survival.

Efforts to mitigate these impacts, such as marine habitat protection and reducing CO2 emissions, are vital to preserving starfish populations and the broader marine ecosystem. Understanding and managing these environmental parameters is essential for maintaining the ecological balance of oceans.