Yes, Doc—I would expect chronic 72°F (22.2°C) water to potentially shorten an American lobster’s lifespan compared with keeping it cooler, although we don’t have good data that let us say something precise like “72°F takes five years off its life.”

The important distinction is that 72°F isn’t immediately lethal. An adult lobster can tolerate it. But it’s above the range generally considered favorable for long-term physiological function. Research reviews put the preferred/favorable range roughly around 46–64°F (8–18°C) and identify temperatures above about 69°F (20.6°C) as increasingly stressful, with more energy devoted to respiration and less available for other functions.

At 72°F, I’d be concerned about chronic effects such as:

• Higher metabolic rate
• Greater oxygen demand while warm water holds less dissolved oxygen
• Physiological and cellular heat stress
• Potentially impaired immune defenses
• Greater susceptibility to opportunistic infection
• Possibly more physiologically demanding molt cycles

Studies at 22°C have demonstrated cellular stress responses in American lobster developmental stages, and elevated temperature has also been associated with reduced immune measures and increased disease susceptibility in subadult lobsters under experimental conditions.

For your pet lobster, I’d personally aim for about 60–65°F rather than 72°F. If you can reliably maintain 65°F with strong aeration, I’d feel considerably better about keeping a large American lobster there for years. I wouldn’t panic over brief excursions to 70–72°F, but I wouldn’t choose 72°F as its permanent temperature.

So, in plain English: 65°F = I’d be comfortable. 72°F = probably survivable, but unnecessarily warm for lifelong captivity. 🦞