Sex in the Sea: The Importance of Reproduction in Marine Conservation Biology

Dr. Marah Hardt
CU Boulder
Science Discovery Teen Café


Written by Youth Leader, Jackson Carter

Dr. Marah Hardt talks about sex and reproduction in the sea.

Dr. Marah Hardt talks about sex and reproduction in the sea.


Boulder’s February café featured Dr. Marah Hardt, a marine biologist who specializes in the reproduction methods employed by various marine life-forms. Her area of focus is on corals and coral reef production, both present day and prehistorically. She began her talk by asking students the question “why sex?” She then explained that sexual reproduction allows species to diversify their gene pool and is facultative for evolutionary advancement. The oceans provide us with oxygen, food, medicines, etc…, making it a crucial part of the global ecosystem and essential for human development and activity on earth. Dr. Hardt introduced us to several examples of marine reproduction and their mating habits. She began her explanation of individual species with the osedax, a bizarre bone-eating worm with dramatically different sizes between members of the opposite sex.  She then went on to talk about salmon. Their reproductive strategy is so physically demanding that the fish die quickly thereafter. Yikes, I’ll never look at them the same! She then described seahorses, that court and synchronize by dancing through seagrass. With cod, the males produce high-frequency vibrations to time fertilization perfectly. Clownfish undergo sex changes as they mature, this develops a hierarchical system to organize such evolutions. Finally, there was the octopi, which pass a specialized tentacle known as hectocotylus to their spouses.

Hands on Activity

The café then transitioned into a sort of game that students were invited to participate in: a Cards Against Humanity-based card game in which students filled in the blank with actual reproductive strategies from marine life. Question cards included “Why can’t I sleep at night?”, “Your persistence is admirable, but you cannot win my heart without ______.”, and “I got 99 problems but _______ ain’t one of them.”, and answers included “vibrating so loudly I release my eggs”, “a daily stroll through the seagrass to coordinate our cycles”, and “challenging the matriarchy”. Dr. Hardt then reunited the students to explain the details behind each of the answer cards, revealing shocking and strange trends in marine reproduction. She touched on problems to undersea reproduction posed by human activity, many of which result from an arrogance on our part on how these species thrive, highlighting the ever to paramount importance of communication as scientists aiming to protect the environment.